JP4125387B2 - Semiconductor device manufacturing method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a semiconductor device using a crystalline semiconductor and a manufacturing method thereof.
[0002]
[Prior art]
A thin film transistor (hereinafter referred to as TFT) using a thin film semiconductor is known. This TFT is formed by forming a thin film semiconductor on a substrate and using this thin film semiconductor. This TFT is used in various integrated circuits, and is particularly attracting attention as a switching element provided with each pixel of an electro-optical device, particularly an active matrix liquid crystal display device, and a driver element formed in a peripheral circuit portion. .
[0003]
As a thin film semiconductor used for a TFT, it is easy to use an amorphous silicon film, but there is a problem that its electrical characteristics are low. In order to obtain improved TFT characteristics, a silicon thin film having crystallinity may be used. The crystalline silicon film is called polycrystalline silicon, polysilicon, microcrystalline silicon, or the like. In order to obtain this silicon film having crystallinity, an amorphous silicon film is first formed and then crystallized by heating.
[0004]
However, crystallization by heating requires a heating temperature of 600 ° C. or more and a time of 10 hours or more, and there is a problem that it is difficult to use a glass substrate as a substrate. For example, Corning 7059 glass used for an active type liquid crystal display device has a glass strain point of 593 ° C., and there is a problem with heating at 600 ° C. or higher in consideration of an increase in area of the substrate.
[0005]
BACKGROUND OF THE INVENTION
According to the study by the present inventors, a small amount of elements such as nickel, palladium, and lead are deposited on the surface of the amorphous silicon film, and then heated, so that the processing time is about 550 ° C. for about 4 hours. It has been found that crystallization can be performed.
[0006]
In order to introduce such a trace amount of element (catalytic element that promotes crystallization), plasma treatment, vapor deposition, or ion implantation may be used. The plasma treatment is a parallel plate type or positive column type plasma CVD apparatus using a material containing a catalytic element as an electrode, and generating a plasma in an atmosphere of nitrogen or hydrogen to form a catalytic element on the amorphous silicon film. It is a method of adding.
[0007]
However, the presence of a large amount of the elements as described above in the semiconductor is not preferable because it impedes the reliability and electrical stability of a device using these semiconductors.
[0008]
That is, the above-mentioned element (catalyst element) that promotes crystallization, such as nickel, is necessary when crystallizing amorphous silicon, but should not be included in crystallized silicon as much as possible. Is desirable. In order to achieve this purpose, a catalyst element that has a strong tendency to be inert in crystalline silicon is selected, and at the same time, the amount of catalyst element required for crystallization is minimized and crystallization is performed with a minimum amount. Need to do. For this purpose, it is necessary to precisely control the amount of the catalyst element added.
[0009]
In addition, when nickel is used as a catalyst element, an amorphous silicon film is formed, a nickel treatment is performed by plasma treatment to produce a crystalline silicon film, and the crystallization process and the like are examined in detail. There was found.
(1) When nickel is introduced onto the amorphous silicon film by plasma treatment, the nickel has already penetrated to a considerable depth in the amorphous silicon film before the heat treatment.
(2) The initial nucleation of the crystal is generated from the surface where nickel is introduced.
(3) Even when nickel is deposited on the amorphous silicon film by vapor deposition, crystallization occurs in the same manner as when plasma treatment is performed.
[0010]
From the above, it can be concluded that not all nickel introduced by plasma treatment is functioning effectively. That is, it is considered that there is nickel that does not function sufficiently even when a large amount of nickel is introduced. From this, it is considered that the point (plane) where nickel and silicon are in contact functions during low-temperature crystallization. It is concluded that nickel must be dispersed as finely as possible in the atomic form. That is, it is concluded that “what is necessary is that nickel as low as possible should be introduced in the form of atoms dispersed in the vicinity of the surface of the amorphous silicon film as long as low-temperature crystallization is possible”.
[0011]
As a method of introducing a very small amount of nickel only in the vicinity of the surface of the amorphous silicon film, in other words, as a method of introducing a very small amount of the catalytic element that promotes crystallization only in the vicinity of the surface of the amorphous silicon film, a vapor deposition method is used. However, the vapor deposition method has a problem of poor controllability, and it is difficult to strictly control the amount of catalyst element introduced.
[0012]
[Problems to be solved by the invention]
In the production of a thin film silicon semiconductor having crystallinity by heat treatment at 600 ° C. or lower using a catalyst element,
(1) A controlled amount of catalyst element is introduced to minimize the amount.
(2) Use a highly productive method.
The purpose is to satisfy such requirements.
[0013]
[Means for Solving the Problems]
In order to satisfy the above object, the present invention obtains a silicon film having crystallinity using the following means.
A catalyst element alone or a compound containing the catalyst element that promotes crystallization of the amorphous silicon film is held in contact with the amorphous silicon film, and the catalyst element alone or the catalyst element is contained in the amorphous silicon film. In the state where the compound is in contact, heat treatment is performed to crystallize the amorphous silicon film.
Specifically, a solution containing a catalytic element is applied to the surface of a substrate on which an amorphous silicon film is formed (even if a protective film sugar is formed on the surface, it is simply referred to as a substrate in this specification). Crystallization of the amorphous silicon film can be realized by forming an amorphous silicon film on the substrate surface and further performing heat treatment.
In particular, the present invention is characterized in that the catalytic element is introduced in contact with the surface of the amorphous silicon film. This is extremely important in controlling the amount of catalytic element.
[0014]
Further, the crystalline silicon film is used to form an active region having at least one electrical junction such as PN, PI, NI or the like of the semiconductor device. As the semiconductor device, a thin film transistor (TFT), a diode, or an optical sensor can be used.
[0015]
By adopting the configuration of the present invention, the following basic significance can be obtained.
(A) The catalyst element concentration in the solution is strictly controlled in advance. Accordingly, it is possible to increase the crystallinity and reduce the amount of the element.
(B) If the solution and the surface of the amorphous silicon film are in contact with each other, the amount of the catalytic element introduced into the amorphous silicon is determined by the concentration of the catalytic element in the solution.
(C) Since the catalytic element in contact with the surface of the amorphous silicon film mainly contributes to crystallization, the catalytic element can be introduced at a necessary minimum concentration.
[0016]
When a solution containing an element that promotes crystallization is applied to a substrate on which an amorphous silicon film is formed, an aqueous solution, an organic solvent solution, or the like can be used as the solution. Here, the inclusion includes both the meaning of inclusion as a compound and the meaning of inclusion by simply dispersing.
[0017]
As the solvent containing the catalyst element, a solvent selected from water, alcohol, acid and ammonia which are polar solvents can be used.
[0018]
When nickel is used as a catalyst and this nickel is included in a polar solvent, nickel is introduced as a nickel compound. Typical nickel compounds include nickel bromide, nickel acetate, nickel oxalate, nickel carbonate, nickel chloride, nickel iodide, nickel nitrate, nickel sulfate, nickel formate, nickel acetylacetonate, 4-cyclohexylbutyric acid. A material selected from nickel, nickel oxide and nickel hydroxide is used.
[0019]
As the solvent containing the catalyst element, a nonpolar solvent selected from benzene, toluene, xylene, carbon tetrachloride, chloroform, and ether can be used.
[0020]
In this case, nickel is introduced as a nickel compound. As this nickel compound, typically, one selected from nickel acetylacetonate and nickel 2-ethylhexanoate can be used.
[0021]
When Fe (iron) is used as the catalyst element, a material known as an iron salt as the compound, for example, ferrous bromide (FeBr) ₂ 6H ₂ O), ferric bromide (FeBr) _Three 6H ₂ O), ferric acetate (Fe (C ₂ H _Three O ₂ ) _Three xH ₂ O), ferrous chloride (FeCl ₂ 4H ₂ O), ferric chloride (FeCl _Three 6H ₂ O), ferric fluoride (FeF) _Three 3H ₂ O), ferric nitrate (Fe (NO _Three ) _Three 9H ₂ O), ferrous phosphate (Fe _Three (PO _Four ) ₂ 8H ₂ O), ferric phosphate (FePO _Four 2H ₂ Those selected from O) can be used.
[0022]
When Co (cobalt) is used as the catalyst element, a material known as a cobalt salt as the compound, for example, cobalt bromide (CoBr6H) ₂ O), cobalt acetate (Co (C ₂ H _Three O ₂ ) ₂ 4H ₂ O), cobalt chloride (CoCl ₂ 6H ₂ O), cobalt fluoride (CoF) ₂ xH ₂ O), cobalt nitrate (Co (No _Three ) ₂ 6H ₂ Those selected from O) can be used.
[0023]
When Ru (ruthenium) is used as the catalyst element, the compound is known as a ruthenium salt, such as ruthenium chloride (RuCl). _Three H ₂ O) can be used.
[0024]
When Rh (rhodium) is used as a catalytic element, a material known as a rhodium salt as the compound, for example, rhodium chloride (RhCl) _Three 3H ₂ O) can be used.
[0025]
When Pd (palladium) is used as a catalyst element, a material known as a palladium salt as the compound, for example, palladium chloride (PdCl ₂ 2H ₂ O) can be used.
[0026]
When Os (osnium) is used as the catalytic element, a material known as an osnium salt as the compound, for example, osmium chloride (OsCl) _Three ) Can be used.
[0027]
When Ir (iridium) is used as a catalyst element, a material known as an iridium salt as the compound, for example, iridium trichloride (IrCl _Three 3H ₂ O), iridium tetrachloride (IrCl _Four ) Can be used.
[0028]
When Pt (platinum) is used as the catalyst element, a material known as a platinum salt as the compound, for example, platinous chloride (PtCl) _Four 5H ₂ O) can be used.
[0029]
When Cu (copper) is used as the catalyst element, cupric acetate (Cu (CH _Three COO) ₂ ), Cupric chloride (CuCl ₂ 2H ₂ O), cupric nitrate (Cu (NO _Three ) ₂ 3H ₂ Materials selected from O) can be used.
[0030]
When gold is used as the catalytic element, gold trichloride (AuCl) is used as the compound. _Three xH ₂ O), gold chloride (AuHCl) _Four 4H ₂ O), sodium tetrachlorogold (AuNaCl) _Four 2H ₂ Materials selected from O) can be used.
[0031]
It is also useful to add a surfactant to the solution containing the catalyst element. This is for increasing the adhesion to the surface to be coated and controlling the adsorptivity. This surfactant may be applied on the surface to be coated in advance.
[0032]
When nickel simple substance is used as a catalyst element, it is necessary to dissolve in acid to form a solution.
[0033]
The above is an example using a solution in which nickel as a catalyst element is completely dissolved, but even if nickel is not completely dissolved, powder of nickel alone or a compound of nickel is uniformly distributed in the dispersion medium. Materials such as dispersed emulsions may be used.
[0034]
These are the same even when a material other than nickel is used as the catalyst element.
[0035]
When nickel is used as a catalyst element for promoting crystallization, and a polar solvent such as water is used as a solution solvent containing nickel, these solutions are directly applied to the surface to be a substrate on which an amorphous silicon film is formed. Then, the solution may be repelled. In this case, a thin oxide film having a thickness of 100 mm or less is first formed, and a solution containing a catalytic element is applied thereon, whereby the solution can be uniformly applied. Also effective is a method of improving wetting by adding a material such as a surfactant to the solution. In the structure of a TFT formed on a glass substrate, a method of forming a silicon oxide film or a silicon nitride film as a base film on the glass substrate surface is known. In this case, a solution can be applied directly. It is.
[0036]
Further, by using a nonpolar solvent such as a toluene solution of nickel 2-ethylhexanoate as the solution, the solution can be applied without forming an underlying oxide film. In this case, it is effective to apply in advance a material such as an adhesive used in resist application.
[0037]
The amount of the catalytic element contained in the solution depends on the type of the solution, but as a general tendency, the amount of nickel is 1 ppm to 200 ppm, preferably 1 ppm to 50 ppm, based on the solution (weight ratio of the catalytic element to the whole solution) ) Is desirable. This is a value determined in view of the nickel concentration in the film and the hydrofluoric acid resistance after crystallization is completed.
[0038]
Moreover, crystal growth can be selectively performed by selectively applying a solution containing a catalytic element. Particularly in this case, crystal growth can be performed in a direction substantially parallel to the surface of the silicon film from the region where the solution is applied toward the region where the solution is not applied. In this specification, a region where crystal growth is performed in a direction substantially parallel to the surface of the silicon film is referred to as a laterally crystallized region.
[0039]
Further, it has been confirmed that the concentration of the catalytic element is low in the region where the crystal growth is performed in the lateral direction. Although it is useful to use a crystalline silicon film as the active layer region of the semiconductor device, it is generally preferable that the impurity concentration in the active layer region is low. Therefore, it is useful for device fabrication to form the active layer region of the semiconductor device using the region where the crystal is grown in the lateral direction.
[0040]
In the present invention, since a catalytic element for promoting crystallization is introduced into the interface between the surface to be formed and the thin film silicon semiconductor formed on the surface to be formed, the catalyst on the surface of the crystallized thin film silicon semiconductor is used. The element concentration can be kept low.
[0041]
In general, a TFT has a configuration of an insulated gate type field effect transistor. In an insulated gate type field effect transistor, an interface between a channel forming region and a gate insulating film and a region near the interface are important.
[0042]
In the insulated gate field effect semiconductor device, if there is a level at the interface between the channel forming region and the gate insulating film or in the vicinity thereof, the characteristics of the insulated gate field effect transistor are greatly inhibited. As a factor for forming such a level, mobile ions and impurities can be considered. Therefore, when manufacturing a TFT employing a configuration in which a gate insulating film is formed on a silicon thin film, it is desirable that impurities and the like are not present on the silicon thin film surface as much as possible.
[0043]
Furthermore, the present invention is extremely useful because the concentration of the catalytic element that promotes crystallization can be reduced as much as possible in the entire region of the crystallized silicon thin film.
[0044]
In addition, when the method of the present invention is adopted, the concentration distribution of the catalytic element in the depth direction of the surface to be processed, which is seen when using the plasma processing, is not seen, so the catalytic element diffuses unnecessarily during the heat treatment There is no such thing.
[0045]
As described above, in the present invention, since the concentration of the catalytic elements present on the surface of the crystallized silicon thin film can be reduced as much as possible, it is possible to form a TFT that is not affected by these catalytic elements as much as possible. . That is, by introducing a catalytic element that promotes crystallization in contact with the lower surface of the silicon thin film, a configuration in which the catalytic element has less influence on the characteristics of the electronic device using the crystalline silicon film surface can be realized.
[0046]
In the present invention, the most prominent effect can be obtained when nickel is used as the catalyst element, but the other usable catalyst elements are preferably Ni, Pd, Pt, Cu, Ag, Au, In, and the like. , Sn, Pd, Sn, Pd, P, As, Sb can be used. One or more kinds of elements selected from group VIII elements, IIIb, IVb, and Vb elements can also be used.
[0047]
The method for introducing the catalyst element is not limited to using a solution such as an aqueous solution or alcohol, and a substance containing the catalyst element can be widely used. For example, a metal compound or oxide containing a catalyst element can be used.
[0048]
【Example】
[Example 1]
[0049]
In this embodiment, a catalyst element that promotes crystallization is contained in an aqueous solution, applied onto a glass substrate, and then an amorphous silicon film is formed and crystallized by heat treatment.
[0050]
In this embodiment, Corning 7059 glass is used as the substrate. Moreover, the magnitude | size shall be 100 mm x 100 mm.
[0051]
FIG. 1 shows a manufacturing process of this embodiment. First, a base silicon oxide film 12 is formed on a glass substrate 11 to a thickness of 2000 mm by sputtering. Then, hydrofluoric acid treatment is performed to remove dirt and a natural oxide film. Needless to say, this step may be omitted if the contamination is negligible.
[0052]
Next, an acetate solution is prepared by adding nickel to the acetate solution. The nickel concentration is 25 ppm. Then, 5 ml of this acetate solution is dropped on the surface of the silicon oxide film 12, and this state is maintained for 5 minutes. Then, spin drying (2000 rpm, 60 seconds) is performed using a spinner. (Fig. 1 (A))
[0053]
The concentration of nickel in the acetic acid solution is preferably used in the range of 1 ppm to 50 ppm.
[0054]
By performing this nickel solution coating step once to a plurality of times, a layer containing nickel having an average film thickness of several to several hundreds of mm can be formed on the surface of the silicon oxide film 12 after spin drying. it can. In this case, nickel in this layer diffuses into the amorphous silicon film in the subsequent heating step, and acts as a catalyst for promoting crystallization. Note that this layer is not necessarily a complete film.
[0055]
After application of the solution, pre-baking is performed at a temperature of 400 ° C. in a nitrogen atmosphere. This step is performed to decompose the solution adsorbed on the surface of the silicon oxide film 12. By performing this step, it is possible to prevent the quality of the amorphous silicon film 14 to be formed later from being deteriorated. Needless to say, the pre-baking temperature is changed depending on the type of solution used in the coating process.
[0056]
Next, an amorphous silicon film 14 is formed to a thickness of 100 to 1500 mm by plasma CVD or LPCVD. Here, the amorphous silicon film 12 is formed to a thickness of 1000 mm by plasma CVD.
[0057]
Then, using a heating furnace, heat treatment is performed at 550 ° C. for 4 hours in a nitrogen atmosphere. As a result, the crystalline silicon thin film 14 formed on the substrate 11 can be obtained.
[0058]
The above heat treatment can be performed at a temperature of 450 ° C. or higher. However, if the temperature is low, the heating time must be lengthened and the production efficiency is lowered. On the other hand, if it is 550 ° or more, the problem of heat resistance of the glass substrate used as the substrate will surface.
[0059]
[Example 2]
In this embodiment, nickel, which is a catalyst element, is contained in alcohol, which is a non-aqueous solution, and applied onto an amorphous silicon film. In this example, nickel acetylacetonate is used as the nickel compound, and the alcohol is contained in the compound. The concentration of nickel may be set to a required concentration.
[0060]
The subsequent steps are the same as those shown in Example 1. The outline of the manufacturing process is the same as that shown in FIG. Specific conditions will be described below. First, nickel acetylacetonate is prepared as a nickel compound. Since this substance is soluble in alcohol and has a low decomposition temperature, it can be easily decomposed during heating in the crystallization step.
[0061]
Further, ethanol is used as the alcohol. First, the above-mentioned nickel acetylacetonate is adjusted to 50 ppm in terms of nickel in ethanol to prepare a solution containing nickel.
[0062]
Then, this solution is applied onto the silicon oxide film 12 which is a base film. The application of the solution onto the underlying silicon oxide film is less than when the aqueous solution of Example 1 is used. This is due to the fact that the contact angle of alcohol is smaller than that of water. Here, it is set as 2 ml dripping with respect to an area of 100 square mm.
[0063]
And it hold | maintains for 5 minutes in this state. Thereafter, drying is performed using a spinner. At this time, the spinner is rotated at 1500 rpm for 1 minute. Thereafter, an amorphous silicon film is formed and subjected to crystallization at 550 ° C. for 4 hours. Thus, a crystalline silicon film is obtained.
[0064]
Example 3
In this embodiment, nickel as a catalytic element is dissolved in an acid, and the acid in which the nickel is dissolved is applied onto the oxide film 12 underlying the amorphous silicon film. The outline of the manufacturing process is the same as that shown in FIG.
[0065]
In this embodiment, 0.1 mol / l nitric acid is used as the acid. Nickel powder is dissolved in this nitric acid so that the concentration of nickel is 50 ppm, and this is used as a solution. The subsequent steps are the same as those in the first embodiment.
[0066]
Example 4
This embodiment shows an example in which a TFT provided in each pixel portion of an active matrix liquid crystal display device is manufactured using a crystalline silicon film manufactured by using the method of the present invention. Needless to say, the application range of the TFT is applicable not only to a liquid crystal display device but also to a generally called thin film integrated circuit.
[0067]
FIG. 2 shows an outline of the manufacturing process of this example. First, a base silicon oxide film (not shown) is formed to a thickness of 2000 mm on a glass substrate. This silicon oxide film has functions of preventing the diffusion of impurities from the glass substrate and improving the wetting characteristics when introducing the catalytic element.
[0068]
Then, an acetate solution containing 10 ppm of nickel is applied, held for 5 minutes, and spin dried using a spinner. Thereafter, pre-baking is performed in a nitrogen atmosphere.
[0069]
The step of introducing nickel may be performed by the method shown in Example 2 or Example 3.
[0070]
Then, an amorphous silicon film is formed to a thickness of 1000 mm by the same method as in Example 1 and crystallized by heat treatment at 550 ° C. for 4 hours. A crystalline silicon film is obtained by this process.
[0071]
Next, the crystallized silicon film is patterned to form island-like regions 104. This island-shaped region 104 constitutes the active layer of the TFT. Then, silicon oxide 105 having a thickness of 200 to 1500 mm, here 1000 mm is formed. This silicon oxide film also functions as a gate insulating film. (Fig. 2 (A))
[0072]
Care must be taken in the production of the silicon oxide film 105. Here, TEOS was used as a raw material, and decomposed and deposited by RF plasma CVD with oxygen at a substrate temperature of 150 to 600 ° C., preferably 300 to 450 ° C. The pressure ratio between TEOS and oxygen was 1: 1 to 1: 3, the pressure was 0.05 to 0.5 torr, and the RF power was 100 to 250 W. Alternatively, the substrate temperature was set to 350 to 600 ° C., preferably 400 to 550 ° C. using TEOS as a raw material together with ozone gas by low pressure CVD or normal pressure CVD. After film formation, annealing was performed at 400 to 600 ° C. for 30 to 60 minutes in an oxygen or ozone atmosphere.
[0073]
In this state, crystallization of the silicon region 104 may be promoted by irradiation with KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) or strong light equivalent thereto. In particular, RTA (rapid thermal annealing) using infrared light can selectively heat only silicon without heating the glass substrate, and further, the interface state at the interface between the silicon and the silicon oxide film is changed. Since it can be reduced, it is useful in the manufacture of an insulated gate field effect semiconductor device.
[0074]
Thereafter, an aluminum film having a thickness of 2000 to 1 μm is formed by an electron beam evaporation method and patterned to form a gate electrode 106. Aluminum may be doped with scandium (Sc) in an amount of 0.15 to 0.2% by weight. Next, the substrate is immersed in an ethylene glycol solution of tartaric acid having a pH of about 7 to 1%, and anodization is performed using platinum as a cathode and the aluminum gate electrode as an anode. The anodization is terminated by first increasing the voltage to 220 V at a constant current and holding it in that state for 1 hour. In this embodiment, 2 to 5 V / min is appropriate for the voltage increase rate in the constant current state. In this manner, the anodic oxide 109 having a thickness of 1500 to 3500 mm, for example, 2000 mm is formed. (Fig. 2 (B))
[0075]
Thereafter, an impurity (phosphorus) was implanted into the island-like silicon film of each TFT by the ion doping method (also called plasma doping method) using the gate electrode portion as a mask. As a doping gas, phosphine (PH _Three ) Was used. Dose amount is 1-4 × 10 ¹⁵ cm ^-2 And
[0076]
Further, as shown in FIG. 2C, irradiation with a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) is performed to improve the crystallinity of the portion where the crystallinity has deteriorated due to the introduction of the impurity region. Laser energy density is 150-400mJ / cm ² , Preferably 200 to 250 mJ / cm ² It is. Thus, N-type impurity (phosphorus) regions 108 and 109 are formed. The sheet resistance in these regions was 200 to 800 Ω / □.
[0077]
In this process, instead of using a laser, a flash lamp is used to raise the temperature to 1000 to 1200 ° C. (silicon monitor temperature) in a short time and heat the sample, so-called RTA (rapid thermal annealing) (RTP, (Also referred to as a rapid thermal process).
[0078]
Thereafter, a silicon oxide film having a thickness of 3000 mm is formed on the entire surface as an interlayer insulator 110 by using TEOS as a raw material and a plasma CVD method using this and oxygen, a low pressure CVD method using ozone, or an atmospheric pressure CVD method. The substrate temperature is 250 to 450 ° C., for example, 350 ° C. After film formation, this silicon oxide film is mechanically polished to obtain surface flatness. Further, an ITO film is deposited by sputtering, and this is patterned to form the pixel electrode 111. (Fig. 2 (D))
[0079]
Then, the interlayer insulator 110 is etched to form contact holes in the source / drain of the TFT as shown in FIG. 1E, and chrome or titanium nitride wirings 112 and 113 are formed. The wiring 113 is a pixel electrode. 111 is connected.
[0080]
A crystalline silicon film into which nickel has been introduced by plasma treatment has a low selectivity to buffer hydrofluoric acid compared to a silicon oxide film, and thus is often etched in the contact hole forming step.
[0081]
However, when nickel is introduced using an aqueous solution at a low concentration of 10 ppm as in this embodiment, the resistance to hydrofluoric acid is high, so that the formation of the contact hole can be performed stably and with good reproducibility.
[0082]
Finally, annealing in hydrogen at 300-400 ° C. for 0.1-2 hours completes the hydrogenation of silicon. In this way, the TFT is completed. A large number of TFTs manufactured at the same time are arranged in a matrix to complete an active matrix liquid crystal display device. This TFT has source / drain regions 108/109 and a channel formation region 114. Reference numeral 115 is an NI electrical junction.
[0083]
When the configuration of this example is adopted, the concentration of nickel present in the active layer is 3 × 10 ¹⁸ cm ^-3 1x10 to a degree or less ¹⁶ atoms cm ^-3 ~ 3x10 ¹⁸ atoms cm ^-3 It is thought that.
[0084]
Example 5
FIG. 3 shows a cross-sectional view of the manufacturing process of this example. First, a silicon oxide base film 502 having a thickness of 2000 mm is formed on a substrate (Corning 7059) 501 by sputtering. The substrate is annealed at a temperature higher than the strain temperature before or after the formation of the base film, and then slowly cooled to below the strain temperature at 0.1 to 1.0 ° C./min. There is little shrinkage of the substrate in the accompanying processes (including the thermal oxidation process of the present invention and the subsequent thermal annealing process), and mask alignment becomes easy. In the Corning 7059 substrate, after annealing at 620 to 660 ° C. for 1 to 4 hours, 0.03 to 1.0 ° C./min, preferably 0.1 to 0.3 ° C./min, and then slowly cooled to 400 to 500 It is good to take it out when the temperature drops to ℃.
[0085]
Next, the amorphous silicon film was crystallized by the method shown in Example 1. That is, a solution containing nickel is applied onto the underlying silicon oxide film 502 and nickel is adsorbed on the surface of the amorphous silicon film 502.
[0086]
Next, an intrinsic (I-type) amorphous silicon film having a thickness of 500 to 1500 mm, for example, 1000 mm is formed by plasma CVD. Then, it is crystallized by annealing for 48 hours at 600 ° C. in a nitrogen atmosphere (atmospheric pressure), and the silicon film is patterned to a size of 10 to 1000 μm square to form an island-like silicon film (TFT active layer) 503. . (Fig. 3 (A))
[0087]
Thereafter, an atmosphere of oxygen containing 70 to 90% of water vapor, 1 atmosphere, 500 to 750 ° C., typically 600 ° C. is formed using a pyrogenic reaction method at a ratio of hydrogen / oxygen = 1.5 to 1.9. To do. By leaving it in this atmosphere for 3 to 5 hours, the surface of the silicon film is oxidized to form a silicon oxide film 504 having a thickness of 500 to 1500 mm, for example, 1000 mm. It should be noted that due to such oxidation, the surface of the initial silicon film is reduced by 50 mm or more, and as a result, the contamination of the outermost surface portion of the silicon film does not reach the silicon-silicon oxide interface. is there. That is, a clean silicon-silicon oxide interface is obtained. Since the thickness of the silicon oxide film is twice that of the silicon film to be oxidized, a silicon oxide film having a thickness of 1000 mm is oxidized to obtain a silicon oxide film having a thickness of 1000 mm. The thickness will be 500 mm.
[0088]
In general, the thinner the silicon oxide film (gate insulating film) and the active layer, the better the characteristics of improving mobility and reducing off-current. On the other hand, the initial amorphous silicon film is easily crystallized as the film thickness increases. Therefore, conventionally, there has been a contradiction in terms of characteristics and process regarding the thickness of the active layer. The present invention solves this contradiction for the first time. That is, a thick amorphous silicon film is formed before crystallization to obtain a good crystalline silicon film. Next, by oxidizing the silicon film, the silicon film is thinned to improve the characteristics as a TFT. Further, this thermal oxidation has a feature that the amorphous component and the crystal grain boundary in which recombination centers are likely to exist are easily oxidized, and as a result, the number of recombination centers in the active layer is reduced. This increases the product yield.
[0089]
After the silicon oxide film 504 is formed by thermal oxidation, the substrate is annealed at 600 ° C. for 2 hours in a dinitrogen monoxide atmosphere (1 atm, 100%). (Fig. 3 (B))
Subsequently, polycrystalline silicon (containing 0.01 to 0.2% phosphorus) having a thickness of 3000 to 8000 mm, for example, 6000 mm is formed by low pressure CVD. Then, the gate electrode 505 is formed by patterning the silicon film. Further, an impurity (in this case, phosphorus) is given to the active layer region (which constitutes a source / drain and a channel) by an ion doping method (also called plasma doping method) in a self-aligning manner using this silicon film as a mask. ) Is added. As doping gas, phosphine (PH _Three ) And the acceleration voltage is set to 60 to 90 kV, for example, 80 kV. The dose is 1 × 10 ¹⁵ ~ 8x10 ¹⁵ cm ^-2 For example, 5 × 10 ¹⁵ cm ^-2 And As a result, N-type impurity regions 506 and 507 are formed.
[0090]
Thereafter, annealing is performed by laser light irradiation. As the laser light, a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) was used, but other lasers may be used. The laser light irradiation condition is an energy density of 200 to 400 mJ / cm. ² For example, 250 mJ / cm ² Then, 2 to 10 shots, for example, 2 shots are irradiated at one place. The effect may be increased by heating the substrate to about 200 to 450 ° C. during the laser light irradiation. (Figure 3 (C))
[0091]
Further, this step may be a method by lamp annealing using near infrared light. Near-infrared rays are more easily absorbed by crystallized silicon than amorphous silicon, and effective annealing comparable to thermal annealing at 1000 ° C. or higher can be performed. On the other hand, the glass substrate (far infrared light is absorbed by the glass substrate, but visible / near infrared light (wavelength 0.5 to 4 μm) is hardly absorbed) is hardly absorbed. Since it is not heated and only a short time is required, it can be said that it is an optimal method in a process where shrinkage of the glass substrate is a problem.
[0092]
Subsequently, a silicon oxide film 508 having a thickness of 6000 mm is formed by plasma CVD as an interlayer insulator. Polyimide may be used as the interlayer insulator. Further, contact holes are formed, and TFT electrodes and wirings 509 and 510 are formed of a metal material, for example, a multilayer film of titanium nitride and aluminum. Finally, annealing is performed at 350 ° C. for 30 minutes in a hydrogen atmosphere of 1 atm to complete the TFT. (Fig. 3 (D))
[0093]
The mobility of the TFT obtained by the method shown above is 110 to 150 cm. ² / Vs and S value were 0.2 to 0.5 V / digit. Further, when a P-channel TFT in which boron is doped in the source / drain by a similar method was also produced, the mobility was 90 to 120 cm. ² / Vs and S value are 0.4 to 0.6 V / digit, and the mobility is 20% or more higher than when a gate insulating film is formed by a known PVD method or CVD method, and the S value is 20 More than%.
Also, from the viewpoint of reliability, the TFT manufactured in this example showed a good result that is not inferior to a TFT manufactured by high-temperature thermal oxidation at 1000 ° C.
[0094]
【effect】
By manufacturing a semiconductor device using a crystalline silicon film that is crystallized at a low temperature in a short time by introducing a catalytic element, a device with high productivity and good characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 shows a manufacturing process of an example.
FIG. 2 shows a manufacturing process of the example.
FIG. 3 shows a manufacturing process of the example.
[Explanation of symbols]
11 .... Glass substrate
12 .... Silicon oxide film
13 .... Acetic acid solution film containing nickel
14... Silicon film
104 ... Active layer
105 ... Silicon oxide film
106 ... Gate electrode
109 ... Oxide layer
108 ... Source / drain region
109 ... Drain / source region
110... Interlayer insulating film (silicon oxide film)
111 ... Pixel electrode (ITO)
112 ... Electrodes
113 ... Electrode

Claims (16)

An oxide film is formed on the glass substrate,
A solution containing an element that promotes crystallization of amorphous silicon in contact with the oxide film is applied using a spinner ,
Drying the solution containing an element that promotes crystallization of the amorphous silicon;
Forming an amorphous silicon film in contact with a surface coated with a solution containing an element that promotes crystallization of the amorphous silicon;
A method for manufacturing a semiconductor device, wherein the amorphous silicon film is crystallized by heating. A solution containing an element that promotes crystallization of amorphous silicon mixed with a surfactant in contact with a glass substrate is applied using a spinner ,
Drying a solution containing an element that promotes crystallization of amorphous silicon mixed with the surfactant;
Forming an amorphous silicon film in contact with a surface coated with a solution containing an element that promotes crystallization of amorphous silicon mixed with the surfactant;
A method for manufacturing a semiconductor device, wherein the amorphous silicon film is crystallized by heating. 3. The element for promoting crystallization of amorphous silicon according to claim 1, wherein the element is selected from Ni, Pd, Pt, Cu, Ag, Au, In, Sn, Pd, and Sn. A method for manufacturing a semiconductor device. According to claim 1 or 2, wherein the solution containing the element that promotes the crystallization of amorphous silicon is first iron _(FeBr 2 _6H 2 O) bromide, ferric bromide _(FeBr 3 _6H 2 O) , Ferric acetate (Fe (C ₂ H ₃ O ₂ ) ₃ xH ₂ O), ferrous chloride (FeCl ₂ 4H ₂ O), ferric chloride (FeCl ₃ 6H ₂ O), ferric fluoride (FeF ₃ 3H ₂ O), ferric nitrate (Fe (NO ₃ ) ₃ 9H ₂ O), ferrous phosphate (Fe ₃ (PO ₄ ) ₂ 8H ₂ O), ferric phosphate (FePO ₄ A method for manufacturing a semiconductor device, wherein a material selected from 2H ₂ O) is used. According to claim 1 or 2, wherein the solution containing the element which promotes crystallization of the amorphous silicon cobalt bromide (CoBr6H ₂ O), cobalt acetate _{(Co (C 2 H 3 O} 2) 2 4H 2 O ), Cobalt chloride (CoCl ₂ 6H ₂ O), cobalt fluoride (CoF ₂ xH ₂ O), and cobalt nitrate (Co (NO ₃ ) ₂ 6H ₂ O) are used. Manufacturing method. According to claim 1 or 2, wherein was contained an element which promotes crystallization of the amorphous silicon solution semiconductor device manufacturing method which comprises using a ruthenium chloride (RuCl 3 H _{2 O).} According to claim 1 or 2, wherein was contained an element which promotes crystallization of the amorphous silicon solution semiconductor device manufacturing method which comprises using a rhodium chloride (RhCl 3 3H _{2 O).} 3. The method for manufacturing a semiconductor device according to claim 1, wherein the solution containing an element that promotes crystallization of amorphous silicon uses palladium chloride (PdCl ₂ 2H ₂ O). According to claim 1 or 2, wherein the solution containing the element which promotes crystallization of the amorphous silicon semiconductor device manufacturing method which comprises using the osmium chloride (OsCl _3). According to claim 1 or 2, wherein the solution containing the element that promotes the crystallization of amorphous silicon is characterized by using the iridium trichloride _(IrCl 3 _3H 2 O) or iridium tetrachloride (IrCl ₄₎ Semiconductor device manufacturing method. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the solution containing an element that promotes crystallization of amorphous silicon uses platinum chloride (PtCl ₄ 5H ₂ O). 3. The solution according to claim 1 or 2 , wherein the solution containing an element that promotes crystallization of amorphous silicon is cupric acetate (Cu (CH ₃ COO) ₂ ) or cupric chloride (CuCl ₂ 2H ₂ O). A method for manufacturing a semiconductor device, wherein a material selected from cupric nitrate (Cu (NO ₃ ) ₂ 3H ₂ O) is used. According to claim 1 or 2, wherein the solution containing the element that promotes the crystallization of amorphous silicon is gold trichloride _(AuCl 3 _xH 2 O), gold chloride salts (AuHCl ₄ 4H ₂ O), tetrachloroaurate A method for manufacturing a semiconductor device, wherein a material selected from sodium (AuNaCl ₄ 2H ₂ O) is used. Using a spinner, a solution in which a compound containing an element that promotes crystallization of amorphous silicon in contact with a glass substrate is dissolved or dispersed in a nonpolar solvent is applied.
Drying a solution in which a compound containing an element that promotes crystallization of amorphous silicon is dissolved or dispersed in a nonpolar solvent;
Forming an amorphous silicon film in contact with a surface coated with a solution in which a compound containing an element that promotes crystallization of amorphous silicon is dissolved or dispersed in a nonpolar solvent;
A method for manufacturing a semiconductor device, wherein the amorphous silicon film is crystallized by heating. The method for manufacturing a semiconductor device according to claim 14 , wherein any one selected from benzene, toluene, xylene, carbon tetrachloride, chloroform, and ether is used as the nonpolar solvent. 16. When nickel is used as an element for promoting crystallization of amorphous silicon in claim 14 , the compound containing the element is selected from nickel acetylacetonate and nickel 2-ethylhexanoate A method for manufacturing a semiconductor device, wherein

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