JP3090847B2 - Method for manufacturing semiconductor substrate and method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in, for example, an active matrix type liquid crystal display device or an image sensor, and is a method of manufacturing a semiconductor substrate having a semiconductor thin film formed on a substrate, and a semiconductor device using the semiconductor thin film. And a method for producing the same.

[0002]

2. Description of the Related Art In the above-mentioned active matrix type liquid crystal display device and the like, a semiconductor device having a thin film transistor (TFT) on an insulating substrate such as glass is used for driving pixels provided therein. In general, a thin film silicon semiconductor is used for the TFT, and the silicon semiconductor used for the TFT is amorphous silicon (a-S
i) It is roughly classified into a semiconductor and a silicon semiconductor having crystallinity.

The former amorphous silicon semiconductor is most commonly used because it has a low manufacturing temperature, can be manufactured relatively easily by a vapor phase method, and has high mass productivity. However, since this amorphous silicon semiconductor is inferior in physical properties such as conductivity to a silicon semiconductor having crystallinity, in order to obtain higher-speed characteristics in the future, a TFT made of the latter silicon semiconductor having crystallinity will be used. There was a strong demand for the establishment of a manufacturing method. Note that as the silicon semiconductor having crystallinity, polycrystalline silicon, microcrystalline silicon, amorphous silicon containing a crystal component, semi-amorphous silicon having an intermediate state between crystalline and non-crystalline are known.

[0004] The following three methods are known as methods for obtaining a thin film silicon semiconductor having such crystallinity.

(1) A first method of directly forming a silicon semiconductor film having crystallinity at the time of film formation (2) An amorphous silicon semiconductor film is formed in advance, and the crystallinity is increased by the energy of laser light. Second method of imparting (3) Third method of forming an amorphous silicon semiconductor film and imparting crystallinity by applying thermal energy However, these methods have the following problems. There is a point.

In the first method, since the film formation step and the crystallization proceed simultaneously, it is indispensable to make the silicon film thick in order to obtain crystalline silicon having a large grain size.
It is technically difficult to form a film having good semiconductor properties uniformly over the entire surface of the substrate. Further, since the film formation temperature is as high as 600 ° C. or higher, there is a problem in cost that an inexpensive glass substrate cannot be used.

In the second method, since the crystallization phenomenon in the melting and solidification process is used, the grain boundaries are satisfactorily processed with a small grain size, and a high-quality crystalline silicon film can be obtained. But,
Taking the excimer laser, which is currently most commonly used, as an example, there is a problem of low throughput due to the small irradiation area of the laser beam, and the stability of the laser is required to uniformly process the entire surface of a large-area substrate. Sex is not enough. Therefore, there is a strong sense of next-generation technology.

In the third method, the first and second methods
There is an advantage that it can cope with a large area as compared with the method described above, but a heat treatment at a high temperature of 600 ° C. or more for several tens of hours is required for crystallization. Therefore, in consideration of using an inexpensive glass substrate and improving the throughput, it is necessary to simultaneously solve the conflicting problems of lowering the heating temperature and crystallizing in a short time. In addition, since this method utilizes the solid-phase crystallization phenomenon, crystal grains spread in parallel to the substrate surface and some grains have a grain size of several μm, and the grown crystal grains collide with each other to form grain boundaries. You. Since the grain boundaries act as trap levels for carriers, they are a major cause of lowering the mobility of the TFT.

Therefore, the following two fourth and fifth methods for solving the problem of the crystal grain boundary by using the third method have been proposed. A fourth method is a method in which an impurity such as silicon (Si ⁺ ) is introduced by an ion implantation method or the like, and a polycrystalline silicon film having crystal grains having a particle size of several μm is obtained by a subsequent heat treatment (Japanese Patent Laid-Open No. Hei 5 (1993) -105). -55142). Another fifth method is a method of spraying silicon particles having a particle diameter of 10 to 100 nm together with high-pressure nitrogen gas onto an amorphous silicon film to form a growth nucleus (Japanese Patent Laid-Open No. 5-136048).
issue). In both of the fourth and fifth methods, after a foreign substance serving as a nucleus for crystal growth is defined and selectively introduced into an amorphous silicon film, crystal growth using the foreign substance as a nucleus is performed by heat treatment. In addition, a high-quality crystalline silicon film having a large grain size is obtained, and a semiconductor element such as a TFT is formed by using this.

However, in these fourth and fifth methods, the foreign matter introduced acts only as a growth nucleus. Therefore, although it is effective for controlling nucleation and crystal growth direction during crystal growth, the above-described problem in the heat treatment step for crystallization still remains. For example, in the fourth method, crystallization is performed by a heat treatment at a temperature of 600 ° C. for 40 hours.
In the above method, the heat treatment is performed at a temperature of 650 ° C. or higher.
Because of this high temperature heating, these techniques are
Although it is an effective technique for an I substrate or an SOS substrate, it is difficult to apply it to an inexpensive glass substrate. For example, Corning 7059 glass used for an active matrix type liquid crystal display device has a glass strain point of 593 ° C.,
When the area of the substrate is increased, there is a problem in heating at 600 ° C. or higher.

Therefore, the present inventors have found a method for producing a crystalline silicon thin film which can achieve both a reduction in the temperature required for crystallization and a reduction in processing time, and further minimize the influence of grain boundaries. Was.

According to the study of the present inventors, a minute amount of a metal element such as nickel, palladium, and lead is introduced into the surface of an amorphous silicon film, and then heated to obtain 55%.
It has been found that crystallization can be performed at 0 ° C. for about 4 hours. It is understood that this mechanism is such that crystal nucleus generation with a metal element as a nucleus occurs early, and then the metal element acts as a catalyst to promote crystal growth, and crystallization proceeds rapidly. In this sense, these metal elements are hereinafter referred to as catalyst elements.

While the silicon film crystallized by the ordinary solid-phase growth method has a twin structure, the crystalline silicon film crystallized by the crystallization promoted by these catalytic elements is
It is composed of many needle-like crystals or columnar crystals, and the inside of each needle-like crystal or columnar crystal is in an ideal single crystal state.

When a TFT is manufactured using such a crystalline silicon film as an active region, the field-effect mobility is improved by about 1.2 times as compared with the case where a crystalline silicon film formed by a usual solid phase growth method is used. I do. After that, by irradiating laser light or strong light to promote its crystallinity,
The difference becomes even more pronounced. This is for the following reasons. That is, when the crystalline silicon film is irradiated with laser light or strong light, the crystal grain boundary portion is intensively processed due to the difference between the melting point of the crystalline silicon film and the melting point of the amorphous silicon film. At this time, since the crystal structure of the crystalline silicon film formed by the ordinary solid phase growth method is a twin structure, the inside of the crystal grain boundary remains as a twin defect even after irradiation with laser light. In contrast, a crystalline silicon film crystallized by introducing a catalytic element is composed of needle-like crystals or columnar crystals, and since the inside thereof is in a single crystal state, crystal grains are irradiated by laser light or strong light. When the boundary portion is processed, a crystalline silicon film almost in a single crystal state is obtained over the entire surface of the substrate.

[0015]

However, the presence of a large amount of such a catalytic element in a semiconductor impairs the reliability and electrical stability of a device using such a semiconductor. Yes, not preferred.

That is, a catalyst element such as nickel which promotes crystallization is necessary when crystallizing amorphous silicon, but it is necessary to minimize the inclusion in the crystallized silicon film. desirable. According to the study of the present inventors, the concentration of the catalytic element in the silicon film is 1 × 10 ¹⁹ atoms / c.
If it exceeds m ³ , after crystallization by heat treatment, when irradiating with an excimer laser, a catalytic element precipitates on the silicon film surface. If a TFT is manufactured while the deposited catalyst element is left as it is, an SD (source-drain) leak is caused, so that the obtained TFT cannot obtain effective characteristics as a semiconductor element. Further, since the precipitated catalyst element is a silicon compound, it is impossible to remove the catalyst element without damaging the silicon film surface. Therefore, when the TFT is manufactured by removing the deposited catalytic element, the mobility is deteriorated and the contact is poor due to the damage of the silicon film surface, which causes a problem in reliability and electrical stability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and a semiconductor having a uniform crystallinity in a substrate surface by performing crystallization in a short time by a heat treatment at 600 ° C. or less. Meet the requirement that a thin film can be produced, higher crystallinity than that obtained by heat treatment can be obtained, and the concentration of the catalyst element contained in the semiconductor thin film having crystallinity can be reduced. It is another object of the present invention to provide a method for manufacturing a high-performance semiconductor substrate and a method for manufacturing a semiconductor device having excellent electrical stability.

[0018]

A method of manufacturing a semiconductor substrate according to the present invention is directed to a method of manufacturing a semiconductor substrate in which a crystalline semiconductor film is formed on an insulating substrate or a substrate having an insulating film deposited on the surface. A step of forming at least an amorphous semiconductor film over a substrate, a step of introducing a catalytic element that promotes crystallization of the amorphous semiconductor film into the amorphous semiconductor film, and heating the entire substrate. The step of crystallizing the amorphous semiconductor film, the step of oxidizing the crystallized semiconductor film surface, and the step of irradiating the oxidized semiconductor film with high-energy light. Objective is achieved.

The method of manufacturing a semiconductor substrate according to the present invention is a method of manufacturing a semiconductor substrate in which a crystalline semiconductor film is formed on an insulating substrate or a substrate having an insulating film deposited on the surface. Forming at least an amorphous semiconductor film, selectively introducing a catalytic element that promotes crystallization of the amorphous semiconductor film into a part of the amorphous semiconductor film, and heating the entire substrate. The step of crystallizing the amorphous semiconductor film, the step of oxidizing the crystallized semiconductor film surface, and the step of irradiating the oxidized semiconductor film with high-energy light. Objective is achieved.

The method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device in which a thin film transistor using a semiconductor film having crystallinity is formed on an insulating substrate or a substrate having an insulating film deposited on the surface. Forming at least an amorphous semiconductor film over the substrate; and selectively introducing a catalytic element that promotes crystallization of the amorphous semiconductor film into a part of the amorphous semiconductor film. Crystallizing the amorphous semiconductor film by heating the entire substrate; oxidizing the crystallized semiconductor film surface; irradiating the oxidized semiconductor film with high-energy light; And the step of manufacturing a thin film transistor so that the region where the is selectively introduced does not overlap with the manufacturing region of the thin film transistor, thereby achieving the above object.

The method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device in which a thin film transistor using a crystalline semiconductor film is formed on an insulating substrate or a substrate having an insulating film deposited on the surface. Forming at least an amorphous semiconductor film over the substrate; and selectively introducing a catalytic element that promotes crystallization of the amorphous semiconductor film into a part of the amorphous semiconductor film. Crystallizing the amorphous semiconductor film by heating the entire substrate; oxidizing the crystallized semiconductor film surface; irradiating the oxidized semiconductor film with high-energy light; So that the region into which is selectively introduced does not overlap with the region for forming the thin film transistor, and the region for forming the thin film transistor is located inside the crystal growth end of the semiconductor film. Since a step of preparing, the object is achieved.

In the present invention, the concentration of the catalytic element in the semiconductor film after the oxidation step is 1 × 10 ¹⁹ atoms / s.
cm ³ or less is desirable. Further, as the catalyst element, Ni, Co, Pd, Pt, Fe, Cu, Ag, A
At least one of u, In, Sn, P, As and Sb can be used. Further, an excimer laser may be used as a light source of the high energy light, or a halogen lamp may be used. Further, a silicon film can be used as the semiconductor film.

[0023]

According to the present invention, a catalytic element is introduced into an amorphous semiconductor film formed on an insulating substrate or a substrate having an insulating film on its surface and heated to grow crystals with the catalytic element as a nucleus. In addition, crystallization is promoted by irradiating the crystallized semiconductor film with high energy and performing crystal grain boundary treatment. Between these two steps, a step of oxidizing the crystallized semiconductor film surface is performed, whereby the concentration of the catalytic element in the crystallized silicon film is reduced.
Hereinafter, this mechanism will be described.

When a nickel element is introduced into an amorphous silicon film, first, a crystal nucleus is generated in a region where the nickel element is introduced, and crystallization of the silicon film occurs. Crystallization proceeds radially along the substrate surface toward the region. Hereinafter, the crystal growth region along the substrate surface is referred to as a lateral growth region. The present inventors measured the nickel concentration using SIMS at three points of a nickel element selective introduction region, a lateral growth region, and a lateral growth end, and found that the nickel element selective introduction region and the lateral growth end 1 × 10 ¹⁹ atoms
s / cm ³ , and 1 × 10
It was about ¹⁸ atoms / cm ³ . From this, it is considered that the nickel element moves while exhibiting a catalytic action of forming a silicon-silicon bond in the nickel-silicon bond portion, and there is always a region where the nickel concentration is high at the growth end portion of the crystal. In addition, when limited to the lateral growth region, the crystal structure of this part is a needle-like crystal or a columnar crystal. However, since the nickel element moves from the crystal part to the amorphous part, the nickel element is Or it exists in the grain boundary part between the columnar crystals. This concentration of the nickel element at the grain boundary is a way for current to escape,
When this is manufactured, the off characteristic is deteriorated, and a problem arises in terms of reliability and electrical stability of the element. As described above, the region where the concentration of the catalyst element is high is distributed in the region where the catalyst element is introduced, the amorphous silicon portion near the crystal growth end of the silicon crystal, and the vicinity of the crystal grain boundary between the crystals.

On the other hand, in a silicon film in which amorphous silicon and crystalline silicon are mixed, when observing the size of crystal grains of crystalline silicon with an electron microscope or the like, a mixed solution of potassium dichromate, nitric acid and hydrofluoric acid is used. When a process called Secco etch is performed using the method, the amorphous portion is removed by etching, and the crystal grains of the crystalline silicon can be easily observed. In this mixed solution, potassium dichromate and nitric acid oxidize the silicon film by a strong oxidizing action, and the hydrofluoric acid component etches the oxidized silicon film. In the amorphous part and the crystalline part, the amorphous silicon part is more easily oxidized,
Fast etching rate. When amorphous silicon and crystalline silicon are compared in this way, it is generally known that amorphous silicon is more easily oxidized.

From the above two facts, when the surface of a crystallized silicon film is oxidized by introducing a catalyst element which promotes crystallization, the crystal growth end portion or the crystal grain boundary portion which is an amorphous portion is obtained. Oxidation proceeds faster than the crystalline portion. Since the concentration of the catalyst element is high in the crystal growth end portion and the crystal grain boundary portion, an oxide film containing the catalyst element is formed, and the catalyst element is removed together with the oxide film by the subsequent etching. As a result, the concentration of the catalytic element in the crystallized silicon film can be significantly reduced. It is desirable that the concentration of the catalytic element in the semiconductor film after the oxidation step is 1 × 10 ¹⁹ atoms / cm ³ or less. Can be prevented. According to our experiments,
The concentration of the catalyst element in the silicon film crystallized by introducing the catalyst element was about 1 × 10 ¹⁹ atoms / cm ³ before oxidation, but reduced to about 1 × 10 ¹⁸ cm ³ after oxidation. did it. Further, when such a method is applied to a crystallized silicon substrate, surface contaminants such as organic substances adhering to the surface of the crystallized silicon film, which can be a cause of characteristic deterioration during TFT fabrication, can be simultaneously cleaned. .

When a catalytic element is introduced into the amorphous semiconductor film,
Crystal nuclei are generated by heating, and then needle-like or columnar crystal growth occurs radially around the crystal nuclei. In particular, when the catalyst element is selectively introduced into a part of the amorphous semiconductor film, the needle-like or columnar crystals grow along the substrate surface from the introduction region to the outside (non-introduction region side). As it goes, the crystal growth direction can be controlled.

In the case where a catalytic element is selectively introduced into a part of the amorphous semiconductor film, it is desirable to manufacture the thin film transistor so that the catalytic element introduction region does not overlap with the thin film transistor manufacturing region. The reason is as follows. In the case where the catalyst element is selectively introduced into the silicon film and the crystal is laterally grown, in order to obtain a sufficient lateral growth distance, the amount of the catalyst element to be introduced is 10 to 100 times as compared with the case where the catalyst element is entirely introduced. It is necessary to be about. As described above, in the region where the catalytic element is introduced at a high concentration, the silicon film has weak laser resistance, hydrofluoric acid resistance, and the like, and is likely to cause surface roughness. This is because the occurrence of surface roughness causes a decrease in TFT mobility and a contact failure. Therefore, it is desirable to arrange the selective introduction region of the catalyst element and the element formation region of the TFT so as not to overlap.

Further, the thin film transistor is manufactured so that the catalyst element introduction region does not overlap with the thin film transistor formation region and the thin film transistor formation region is inside (introduction region side) the crystal growth end of the semiconductor film. It is desirable. The reason is the same as above,
It is as follows. In the case where the catalyst element is selectively introduced into the silicon film and the crystal is laterally grown, in order to obtain a sufficient lateral growth distance, the amount of the catalyst element to be introduced is 10 to 100 times as compared with the case where the catalyst element is entirely introduced. It is necessary to be about. As described above, in the region where the catalytic element is introduced at a high concentration, the silicon film has weak laser resistance, hydrofluoric acid resistance, and the like, and is likely to cause surface roughness. If surface roughness occurs, T
This is because it causes a decrease in the mobility of the FT and a contact failure. Therefore, it is desirable to arrange the selective introduction region of the catalyst element and the element formation region of the TFT so as not to overlap.

Ni, Co, Pd, P
At least one of t, Fe, Cu, Ag, Au, In, Sn, P, As and Sb can be used,
With these catalyst elements, the heat treatment temperature for crystallization can be lowered to about 500 ° C. to 580 ° C.

When an excimer laser is used as a light source of high-energy light, light having a high energy density can be easily obtained, so that a crystal grain boundary portion can be processed to obtain a highly crystalline semiconductor film. When a halogen lamp is used, light can be irradiated over a large area at the same time, and the process throughput can be further improved.

When a silicon film is used as a semiconductor film, C
Using a VD apparatus, a high-quality semiconductor film can be easily obtained over a large area at a temperature of 500 ° C. or lower.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1A to 1D are process sectional views showing an outline of a method for manufacturing a semiconductor substrate of Embodiment 1. FIG.

First, as shown in FIG. 1A, after cleaning the surface of an insulating substrate such as glass, silicon dioxide is deposited to a thickness of about 200 nm using a sputtering device to form a base coat film 101.

An amorphous silicon film having a thickness of about 100 nm is deposited thereon by chemical vapor deposition (CVD) or sputtering. The thickness of this amorphous silicon film can be in the range of 20 to 150 nm.

After introducing nickel as a catalyst element for promoting crystallization into the amorphous silicon film, the entire substrate is heated at 550 ° C.
The heat treatment is performed at a temperature of. By this heat treatment, 3 to 10
A crystal nucleus is generated in about a minute, and thereafter, needle-like or columnar crystal growth radially occurs around the crystal nucleus. FIG.
(A) is a cross-sectional view when the substrate is cut in a direction crossing the needle-like or columnar crystal region 102, and 103 denotes an amorphous silicon region at a crystal grain boundary portion. It is to be noted that nickel is introduced by directly or directly forming a mask for selective implantation on a silicon film, and then forming a film of Ni or a Ni-Si compound by a sputtering method or the like, and then adding N
a method of diffusing i, after depositing Ni on the surface by plasma treatment in a plasma chamber having a Ni electrode,
It can be performed by a method of diffusing into a silicon film, a method of injecting Ni by ion doping, or the like.

Next, as shown in FIG. 1B, the surface of the silicon film is oxidized. In this figure, 104 is an oxide film, 105 is a silicon film surface before surface oxidation, and 106 is a silicon film surface after surface oxidation. In this example, thermal oxidation was performed at 600 ° C. for 12 hours in a steam atmosphere. This thermal oxidation reduced the thickness of the silicon film by about 10 nm. Here, paying particular attention to the interface 106 between the silicon film and the silicon oxide film, since the oxidation rate is higher in the amorphous portion (shaded portion) than in the crystalline portion, the oxidation proceeds deeper in the crystal grain boundary portion. doing. Further, oxidation proceeds rapidly in the crystal grain boundary portion where the nickel concentration is high, so that the nickel concentration contained in the silicon film can be reduced.
SIMS analysis results, it was confirmed that was reduced to approximately ^{1 × 10 1 8 atoms / cm} 3 from 1 × 10 ¹⁹ atoms / cm ³ or so.

Thereafter, as shown in FIG. 1C, the oxide film 104 on the surface is removed. At this time, the nickel element is removed together with the oxide film. Further, contaminants on the surface of the silicon film can be removed at the same time.

When the substrate in this state is irradiated with excimer laser light 107 as high-energy light, as shown in FIG.
Is taken into the crystal. In this figure, reference numeral 108 denotes a new crystal grain interface, and a broken line 109 denotes a crystal grain interface before laser irradiation. In this example, since the concentration contained in the silicon film was reduced by the surface oxidation step, no deposition of nickel due to laser beam irradiation was observed.

As described above, a polycrystallized silicon film having good uniformity in the substrate surface and excellent electric characteristics almost similar to a single crystal was obtained.

(Embodiment 2) FIGS. 2A to 2D are process sectional views showing an outline of a method for manufacturing a semiconductor substrate of Embodiment 2. FIG.

First, as shown in FIG. 2A, after cleaning the surface of an insulating substrate such as glass, silicon dioxide is deposited to a thickness of about 200 nm using a sputtering device to form a base coat film 201.

An amorphous silicon film having a thickness of about 100 nm is deposited thereon by chemical vapor deposition (CVD) or sputtering.

After introducing nickel as a catalyst element for promoting crystallization into the amorphous silicon film, the entire substrate is heated to 550 ° C.
The heat treatment is performed at a temperature of. By this heat treatment, 3 to 10
A crystal nucleus is generated in about a minute, and thereafter, needle-like or columnar crystal growth radially occurs around the crystal nucleus. FIG.
(A) is a cross-sectional view of the substrate cut in a direction transverse to the needle-like or columnar crystal region 202, and 203 denotes an amorphous silicon region at a crystal grain boundary portion.

Next, as shown in FIG. 2B, the surface of the silicon film is oxidized. In this figure, reference numeral 204 denotes an oxide film, 205 denotes a silicon film surface before surface oxidation, and 206 denotes a silicon film surface after surface oxidation. In this example, thermal oxidation was performed at 600 ° C. for 12 hours in a steam atmosphere. This thermal oxidation reduced the thickness of the silicon film by about 10 nm. Here, paying particular attention to the interface 206 between the silicon film and the silicon oxide film, since the oxidation rate is higher in the amorphous portion (shaded portion) than in the crystalline portion, oxidation proceeds deeper in the crystal grain boundary portion. doing. Further, oxidation proceeds rapidly in the crystal grain boundary portion where the nickel concentration is high, so that the nickel concentration contained in the silicon film can be reduced.
SIMS analysis results, it was confirmed that was reduced to approximately ^{1 × 10 1 8 atoms / cm} 3 from 1 × 10 ¹⁹ atoms / cm ³ or so.

When the substrate in this state is irradiated with excimer laser light 207 as high energy light, as shown in FIG.
Is taken into the crystal. In this figure, reference numeral 208 denotes a new crystal grain interface, and a broken line 209 denotes a crystal grain interface before laser irradiation. In this example, since the concentration contained in the silicon film was reduced by the surface oxidation step, no deposition of nickel due to laser beam irradiation was observed.

Thereafter, as shown in FIG. 2D, the oxide film 204 on the surface is removed. At this time, the nickel element is removed together with the oxide film. Further, contaminants on the surface of the silicon film can be removed at the same time.

As described above, a crystalline silicon film having good uniformity in the substrate surface and excellent electric properties almost similar to a single crystal was obtained.

(Embodiment 3) FIGS. 3A to 3F are process sectional views showing an outline of a method for manufacturing a semiconductor substrate of Embodiment 3. FIG.

First, as shown in FIG. 3A, after cleaning the surface of an insulating substrate such as glass, silicon dioxide is deposited to a thickness of about 200 nm using a sputtering apparatus to form a base coat film 301.

An amorphous silicon film 302 having a thickness of about 100 nm is deposited thereon by chemical vapor deposition (CVD) or sputtering. The thickness of this amorphous silicon film can be in the range of 20 to 150 nm.

Next, nickel is selectively introduced into the region 303 in the amorphous silicon film 302 as a catalyst element for promoting crystallization. FIG. 3A is a cross-sectional view in this state.

Thereafter, when the entire substrate is subjected to a heat treatment at a temperature of 550 ° C., crystal nuclei are generated in about 3 to 10 minutes, and further, needle-like or columnar crystal growth occurs radially around the crystal nuclei. . This needle-like or columnar crystal eventually becomes a region 303 as shown by an arrow 304 in FIG.
Grows along the substrate surface from the outside toward the outside (non-introduction region). The nickel is selectively introduced by forming Ni or a Ni—Si compound by sputtering or the like with a mask for selective implantation formed on the silicon film, and then diffusing Ni into the silicon film. A method in which Ni is deposited on a surface by plasma treatment in a plasma chamber having a Ni electrode and then diffused into a silicon film;
Alternatively, it can be performed by a method of injecting Ni by ion doping or the like.

FIG. 3C is a cross-sectional view of the substrate after the crystallization by the heat treatment has been completed. A needle-like or columnar crystal region (lateral growth region) 305 exists outside the nickel selective introduction region 303, and a crystal growth end region 306 exists outside that. Here, the selective introduction region 303 and the crystal growth end region 306 have a higher nickel concentration than the needle-like or columnar crystal region 305.

FIG. 3D is a cross-sectional view when a portion indicated by a dashed line in FIG. 3C is cut along a plane perpendicular to the paper surface. In this figure, reference numeral 307 denotes a needle-like or columnar crystal region, and reference numeral 308 denotes an amorphous silicon region where a core crystal grain boundary portion remains.

Next, as shown in FIG. 3E, the surface of the silicon film is oxidized. In this figure, 309 indicates an oxide film, 310 indicates the surface of the silicon film before surface oxidation, and 311 indicates the surface of the silicon film after surface oxidation. In this example, thermal oxidation was performed at 600 ° C. for 12 hours in a steam atmosphere. This thermal oxidation reduced the thickness of the silicon film by about 10 nm. Here, paying particular attention to the interface 311 between the silicon film and the silicon oxide film, since the oxidation rate is higher in the amorphous portion than in the crystal region 307, the oxidation proceeds deeper in the crystal grain boundary region 308. . In addition, oxidation in the crystal grain boundary region 308 having a high nickel concentration and the crystal growth edge proceeds rapidly, so that the concentration of nickel contained in the silicon film can be reduced. As a result of the SIMS analysis, the selective introduction region 303 of the nickel element and the crystal growth end 306 have a density of about 1 × 10 ¹⁹ atoms / cm ³ to 1 × 10 ¹⁸ at.
oms / cm ³ , and in the acicular or columnar crystal growth region 305, it was confirmed to have decreased from about 1 × 10 ¹⁸ atoms / cm ^{3 to} about 4 × 10 ¹⁷ atoms / cm ³ .

Thereafter, as shown in FIG. 3F, the oxide film 309 on the surface is removed. At this time, the nickel element is removed together with the oxide film. Further, contaminants on the surface of the silicon film can be removed at the same time.

When the substrate in this state is irradiated with excimer laser light 312 as high-energy light, the amorphous silicon region 308 at the crystal grain boundary is taken into the crystal.
In this figure, reference numeral 314 denotes a new crystal grain interface, and a broken line 313 denotes a crystal grain interface before laser irradiation. In this example, since the concentration contained in the silicon film was reduced by the surface oxidation step, no deposition of nickel due to laser beam irradiation was observed.

As described above, a crystalline silicon film having good uniformity in the substrate surface and excellent electric characteristics almost similar to a single crystal was obtained. Further, in the region 305 of the crystalline silicon film,
The growth direction of the acicular or columnar crystals was controlled from the catalyst element introduction region 303 toward the non-introduction region (outside).

Fourth Embodiment FIGS. 4A to 4F are process cross-sectional views showing an outline of a method for manufacturing a semiconductor substrate of a third embodiment.

First, as shown in FIG. 4A, after cleaning the surface of an insulating substrate such as glass, silicon dioxide is deposited to a thickness of about 200 nm using a sputtering apparatus to form a base coat film 401.

An amorphous silicon film 402 having a thickness of about 100 nm is deposited thereon by chemical vapor deposition (CVD) or sputtering.

Next, nickel is selectively introduced into the region 403 of the amorphous silicon film 402 as a catalyst element for promoting crystallization. FIG. 4A is a cross-sectional view in this state.

Thereafter, when the entire substrate is subjected to a heat treatment at a temperature of 550 ° C., crystal nuclei are generated in about 3 to 10 minutes, and further, needle-like or columnar crystal growth occurs radially around the crystal nuclei. . This needle-like or columnar crystal eventually becomes a region 403 as shown by an arrow 404 in FIG.
Grows along the substrate surface from the outside toward the outside (non-introduction region).

FIG. 4C shows a cross-sectional view of the substrate in a state where the crystallization by the heat treatment has been completed. A needle-like or columnar crystal region (lateral growth region) 405 exists outside the nickel selective introduction region 403, and a crystal growth end region 406 exists outside the region. Here, the selective introduction region 403 and the crystal growth end region 406 have a higher nickel concentration than the needle-like or columnar crystal region 405.

FIG. 4D is a cross-sectional view when a portion indicated by a dashed line in FIG. 4C is cut along a plane perpendicular to the paper surface. In this drawing, reference numeral 407 denotes a needle-like or columnar crystal region, and reference numeral 408 denotes an amorphous remaining portion at the core crystal grain boundary.

Next, as shown in FIG. 4E, the surface of the silicon film is oxidized. In this figure, 409 is an oxide film, 410 is a silicon film surface before surface oxidation, and 411 is a silicon film surface after surface oxidation. In this example, thermal oxidation was performed at 600 ° C. for 12 hours in a steam atmosphere. This thermal oxidation reduced the thickness of the silicon film by about 10 nm. Here, paying particular attention to the interface 411 between the silicon film and the silicon oxide film, since the oxidation rate of the amorphous portion is faster than that of the crystalline portion 407, the oxidation proceeds deeper in the crystal grain boundary portion 408. I have. In addition, oxidation at the crystal grain boundary portion 408 with a high nickel concentration and at the crystal growth end proceeds rapidly, so that the concentration of nickel contained in the silicon film can be reduced. As a result of the SIMS analysis, the selective introduction region 403 of the nickel element and the crystal growth end 406 have a density of about 1 × 10 ¹⁹ atoms / cm ³ to 1 × 10 ¹⁸ a.
It was confirmed that the density decreased to about toms / cm ³ , and decreased to about 4 × 10 ¹⁷ atoms / cm ³ from about 1 × 10 ¹⁸ atoms / cm ³ in the acicular or columnar crystal growth region 405.

When the substrate in this state is irradiated with an excimer laser 412 as high-energy light as shown in FIG. 4F, the amorphous portion 408 at the crystal grain boundary portion is taken into the crystal. In this figure, reference numeral 414 denotes a new crystal grain interface, and broken line 413 denotes a crystal grain interface before laser irradiation. In this example, since the concentration contained in the silicon film was reduced by the surface oxidation step, no deposition of nickel due to laser beam irradiation was observed.

After that, the oxide film 409 on the surface is removed.
At this time, the nickel element is removed together with the oxide film. Further, contaminants on the surface of the silicon film can be removed at the same time.

As described above, a crystalline silicon film having good uniformity in the substrate surface and excellent electric characteristics almost similar to a single crystal was obtained. Further, in the region 405 of the crystalline silicon film,
The growth direction of the acicular or columnar crystals was controlled from the catalyst element introduction region 403 toward the non-introduction region (outside).

When a semiconductor device is manufactured using the crystalline silicon film obtained in Examples 1 to 4 as an active region of a TFT, a crystalline silicon film having good crystallinity, which is very close to single-crystal silicon, is formed. Since it can be a region, high field-effect mobility can be obtained. Since the crystalline silicon film has a low concentration of the catalytic element, the off-characteristics do not deteriorate, and since there is no precipitation of the catalytic element at the time of fabrication, current leakage, mobility deterioration, and contact failure do not occur. Therefore, a semiconductor device with excellent reliability and electrical stability can be obtained.

Example 5 In this example, TFTs were formed on a semiconductor substrate manufactured in the same manner as in Example 3 or 4, with the arrangement shown in FIG.

In this figure, reference numeral 501 denotes a selective introduction region of a catalytic element for promoting crystallization. After the introduction of the catalytic element, if the entire substrate is subjected to heat treatment, a crystal nucleus is generated in the region 501 in about 3 to 10 minutes, and if the heating is further continued, a needle-like or columnar crystal grows radially around the crystal nucleus Happens. This needle-like or columnar crystal eventually becomes the arrow 5
03, outside (non-introduction area) from area 501
Grows along the substrate surface toward. Curve 502
Indicates the crystal growth end at the end of the heat treatment.

In this semiconductor device, the TFT is arranged in the region 504 outside the selective introduction region 501 of the catalytic element, and it is possible to obtain a TFT having good electric characteristics for the reason described in the above-mentioned section of the operation. Can be.

Example 6 In this example, TFTs were manufactured on a semiconductor substrate manufactured in the same manner as in Example 3 or 4, with the arrangement shown in FIG.

In this figure, reference numeral 601 denotes a selective introduction region of a catalytic element for promoting crystallization. When the entire substrate is subjected to heat treatment after the introduction of the catalytic element, a crystal nucleus is generated in the region 601 in about 3 to 10 minutes. Happens. This needle-like or columnar crystal eventually becomes an arrow 6
03, outside the region 601 (non-introduction region)
Grows along the substrate surface toward. Curve 602
Indicates the crystal growth end at the end of the heat treatment.

In this semiconductor device, the TFT is arranged in the region 604 outside the selective introduction region 601 of the catalyst element and inside the crystal growth end 602, and for the reason explained in the above-mentioned operation section. Thus, a TFT having good electric characteristics can be obtained.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications can be made based on the technical concept of the present invention.

In the above embodiment, the film thickness required for the base coat film depends on the surface condition of the substrate, and is omitted if the substrate is sufficiently flat and has a sufficiently low ion concentration such as sodium ions that adversely affects semiconductor characteristics such as sodium ions. It is also possible. Conversely, if the substrate has a poor surface condition and severe scratches and irregularities, it is necessary to deposit the film thicker than the above film thickness.

Nickel is given as an example of a catalyst element for promoting crystallization, but Ni, Co, Pd, Pt, F
e, Cu, Ag, Au, In, Sn, P, As and S
Any one of b may be used as long as it is at least one.

The same effect can be obtained by using another method such as thermal oxidation using HCl, a halogen gas or an oxygen gas as the method of oxidizing the silicon film.

Although an excimer laser is used as a light source for high energy light, other light sources such as a halogen lamp and a continuous wave laser may be used. Excimer lasers have the advantage that light with a high energy density can be easily obtained, and halogen lamps have the advantage that they can simultaneously irradiate light over a large area, thereby improving process throughput.

[0084]

As is apparent from the above description, according to the present invention, since the amorphous film is crystallized by introducing a catalyst element which promotes crystallization, the process temperature is reduced to about 550 ° C. A crystalline semiconductor film can be manufactured by a short-time treatment at a low temperature. At this time, the crystal growth direction can be controlled by selectively introducing the catalyst element. Further, by oxidizing the surface of the crystallized semiconductor film, the concentration of the catalytic element can be reduced, and contaminants on the film surface can be removed at the same time. Further, by performing high-energy light irradiation and performing grain boundary treatment, a favorable crystalline semiconductor film which is almost single crystal can be obtained.

When a TFT is manufactured using this crystalline semiconductor film, a TFT having a large on / off ratio, a low leakage current and a high mobility can be obtained, and a semiconductor device excellent in reliability and electrical stability can be obtained. Can be provided.

Further, since the maximum process temperature is suppressed to about 600 ° C. and the crystallization time can be shortened, a plate glass having a strain point of about 650 ° C., which has recently started to be mass-produced, can be used as a substrate. Therefore, mass production of a direct-view type driver monolithic large-screen liquid crystal display device can be realized.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view illustrating a method for manufacturing a semiconductor substrate of Example 1.

FIG. 2 is a process cross-sectional view illustrating a method for manufacturing a semiconductor substrate of Example 2.

FIG. 3 is a process cross-sectional view illustrating a method for manufacturing a semiconductor substrate of Example 3;

FIG. 4 is a process cross-sectional view illustrating a method for manufacturing a semiconductor substrate of Example 4;

FIG. 5 is a layout view of a manufacturing region of a TFT in the semiconductor device of Example 5;

FIG. 6 is a layout view of a TFT manufacturing region in a semiconductor device of Example 6.

[Explanation of symbols]

101, 201, 301, 401 Base coat film 102, 202, 305, 307, 405, 407 Needle or columnar crystal region 103, 203, 308 Amorphous silicon region (grain boundary region) 408 Amorphous remaining portion (crystal Grain boundary portion) 104, 204, 309, 409 Oxide film 105, 205, 310, 410 Silicon film surface before surface oxidation 106, 206, 311, 411 Silicon film surface after surface oxidation (interface) 107, 207, 312, 412 Excimer laser beam 108, 208, 313, 413 Crystal grain interface 109, 209, 314, 414 Crystal grain interface 302, 402 Silicon film 303, 403 Selective introduction region (region) 304, 404 Arrow (growth direction) 306, 406 Crystal Growth edge area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01L 21/336 H01L 29/78 627G 29/786 (56) References JP-A-6-267988 (JP, A) JP-A-4 -196312 (JP, A) JP-A-6-181178 (JP, A) JP-A-8-8181 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 H01L 21/31 H01L 21/20 H01L 29/786

Claims (4)

(57) [Claims] 1. A method for manufacturing a semiconductor substrate comprising a semiconductor substrate having crystallinity formed on an insulating substrate or a substrate having an insulating film deposited on a surface thereof, wherein at least an amorphous semiconductor film is formed on the substrate. Forming, a step of introducing a catalytic element that promotes crystallization of the amorphous semiconductor film into the amorphous semiconductor film, and a step of crystallizing the amorphous semiconductor film by heating the entire substrate. A method of manufacturing a semiconductor substrate, comprising: oxidizing a surface of a crystallized semiconductor film; and irradiating the oxidized semiconductor film with high-energy light. 2. A method for manufacturing a semiconductor substrate in which a semiconductor film having crystallinity is formed on an insulating substrate or a substrate having an insulating film deposited on a surface thereof, wherein at least an amorphous semiconductor film is formed on the substrate. Forming, a step of selectively introducing a catalyst element that promotes crystallization of the amorphous semiconductor film into a part of the amorphous semiconductor film, and heating the entire substrate to form the amorphous semiconductor film. A method of manufacturing a semiconductor substrate, comprising: crystallizing a semiconductor film; oxidizing a surface of the crystallized semiconductor film; and irradiating the oxidized semiconductor film with high-energy light. 3. A method for manufacturing a semiconductor device in which a thin film transistor using a semiconductor film having crystallinity is formed over an insulating substrate or a substrate having an insulating film deposited on a surface thereof, wherein at least an amorphous film is formed on the substrate. Forming a crystalline semiconductor film; selectively introducing a catalytic element that promotes crystallization of the amorphous semiconductor film into a part of the amorphous semiconductor film; Crystallizing the amorphous semiconductor film, oxidizing the crystallized semiconductor film surface, irradiating the oxidized semiconductor film with high-energy light, and selectively introducing the catalytic element. And a step of manufacturing a thin film transistor so that a manufacturing region of the thin film transistor does not overlap. 4. A method for manufacturing a semiconductor device in which a thin film transistor using a semiconductor film having crystallinity is formed on an insulating substrate or a substrate having an insulating film deposited on a surface thereof, wherein at least an amorphous film is formed on the substrate. Forming a crystalline semiconductor film; selectively introducing a catalytic element that promotes crystallization of the amorphous semiconductor film into a part of the amorphous semiconductor film; Crystallizing the amorphous semiconductor film, oxidizing the crystallized semiconductor film surface, irradiating the oxidized semiconductor film with high-energy light, and selectively introducing the catalytic element. And forming a thin film transistor such that the thin film transistor is not overlapped with the thin film transistor formation region and the thin film transistor formation region is inside the crystal growth end of the semiconductor film. Method of manufacturing a body apparatus.