JPH0738110A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide the manufacturing method with which an amorphous silicon TFT of low leak current and a high mobility polycrystalline silicon TFT can be manufactured easily on the same substrate. CONSTITUTION:A polycrystalline silicon film 21 is formed by depositing amorphous silicon of low hydrogen concentration of 5X10<20> atoms/cm<3> or lower and by crystallizing a part of an amorphous silicon film 2 by beam annealing. The amorphous silicon film 2, which is not beam-annealed, is hydrogenated and an amorphous silicon film 2, having little dangling bond, is formed. As a result, an amorphous silicon TFT and a polycrystalline silicon TFT are simply formed on the same substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device using a thin film transistor.

[0002]

2. Description of the Related Art In recent years, a drive circuit integrated type T in which a drive circuit is formed by a TFT on the same substrate as a pixel switching TFT
FT-LCDs are receiving attention. Drive circuit integrated TFT
-A high-mobility polycrystalline silicon TFT is used for the TFT for the LCD drive circuit. However, when the pixel switching TFT and the drive circuit are formed of polycrystalline silicon TFTs, there is a problem that the pixel switching TFT has a large leak current and the pixel holding characteristic is insufficient.
Therefore, a method has been proposed in which an amorphous silicon TFT having a small leak current is used for the pixel switching TFT, and a high mobility polycrystalline silicon TFT is used for the drive circuit section.

Conventionally, an amorphous silicon TFT is formed on the same substrate.
In order to fabricate a polycrystalline silicon TFT, there is a method of depositing an amorphous silicon film and performing beam annealing only on the drive circuit portion to form a polycrystalline silicon film. In Figure 4,
The conventional manufacturing method is shown.

First, a conductive film 7 is deposited on an insulating substrate 1 and patterned into a gate electrode shape, and then a laminated film composed of a gate insulating film 3 / amorphous silicon film 20 is formed.
(FIG. 4 (a)).

Next, as shown in FIG. 4B, after separating the laminated film on the substrate, the amorphous silicon film 20 in the drive circuit portion is beam annealed to form a polycrystalline silicon film 21. .

Finally, the nitride film 8 / n ⁺ Si film 9 / metal film 1
0 is formed as shown in FIG. 4C, and an amorphous silicon TFT (A) and a polycrystalline silicon TFT (B) are completed on the same substrate.

By the way, a pixel switching TFT
Since it is necessary to reduce the dangling bonds in the amorphous silicon film 20 in order to reduce the leakage current of (A), the amorphous silicon film 20 usually contains a large amount of hydrogen of about 12 at. . However, when such a large amount of hydrogen-containing amorphous silicon film 20 is beam-annealed, microvoids are generated or the film is ablated.
It was found that the beam annealing could not be performed well. Therefore, since the polycrystalline silicon film 21 having good crystallinity cannot be obtained, the mobility of the polycrystalline silicon TFT (B) is insufficient for use in a drive circuit. The above problems can be solved by depositing the amorphous silicon film and the polycrystalline silicon film in separate steps, but after forming one film, mask this film to deposit the other film. It is necessary to perform the process, which causes an increase in the mask formation process and the film deposition process. As described above, the conventional method cannot provide an amorphous silicon TFT having a small leak current and a polycrystalline silicon TFT having a high mobility on the same substrate without complicating the manufacturing process.

[0008]

In a conventional liquid crystal display device, in a driving circuit integrated TFT-LCD, when a polycrystalline silicon TFT is used only in the driving circuit portion, an amorphous silicon used in a pixel switching TFT is used. When the film is beam annealed, microvoids are generated or the film is ablated, so that there is a problem that a polycrystalline silicon TFT having a high mobility cannot be obtained.

The present invention has been made in view of the above problems, and provides a method of manufacturing a semiconductor device in which an amorphous silicon TFT having a small leak current and a polycrystalline silicon TFT having a high mobility are easily manufactured on the same substrate. The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION The present invention is a semiconductor device in which an amorphous silicon thin film transistor in which an active layer is formed from an amorphous silicon thin film formed on the same substrate and a polycrystalline silicon thin film transistor are mixed. In the manufacturing method of step 1, a step of depositing an amorphous silicon film having a hydrogen concentration of 5 × 10 ²⁰ atoms / cm ³ or less on the substrate to form an active layer of the amorphous silicon thin film transistor, Forming an active layer of the polycrystalline silicon thin film transistor by beam annealing an amorphous silicon film different from the active layer of the amorphous silicon thin film transistor in the silicon film to convert it into polycrystalline silicon; And a step of hydrogenating an active layer of a silicon thin film transistor. It

In particular, it is preferable to perform hydrogenation of the amorphous silicon film and hydrogenation of the polycrystalline silicon film in the same step.
The hydrogen concentration here can be known by secondary ion mass spectrometry.

[0012]

According to the method of manufacturing a semiconductor device of the present invention, an amorphous silicon film having a small amount of hydrogen in the film is used, so that microvoids and film ablation are not generated even when a high energy beam is irradiated. Since the entire amorphous silicon film can be crystallized in the film thickness direction, a high mobility polycrystalline silicon TFT can be obtained. On the other hand, since the amorphous silicon film that is not laser-annealed is hydrogenated and the dangling bonds are terminated with hydrogen, an amorphous silicon TFT with a small leak current can be manufactured. In this way, the film formation only needs to be done once, and the number of steps can be increased only by hydrogenation afterward, so that the manufacturing steps are not complicated.

[0013]

EXAMPLES The present invention will be described below with reference to examples. (Embodiment 1) FIG. 1 shows a method of manufacturing a liquid crystal display device using a TFT according to the present invention in the order of steps.

First, as shown in FIG. 1A, the hydrogen concentration in the film is 3 × on an insulating substrate 1 such as non-alkali glass or quartz.
An amorphous silicon film 2 of 10 ²⁰ atoms / cm ³ is formed. The deposition of the amorphous silicon film 2 is performed by using the source gases SiH4 and H2 as the forming conditions, and the substrate temperature is 450 ° C. to 600 ° C.
The plasma CVD method is performed at a high temperature of ° C. Also, LP
A similar low hydrogen concentration amorphous silicon 2 may be deposited by using a method such as a CVD method or a sputtering method. By setting the film thickness of the amorphous silicon film 2 to about 500 A, the entire film can be crystallized in the film thickness direction, so that a polycrystalline silicon film with good crystallinity can be obtained.

Next, as shown in FIG. 1B, beam annealing is performed only on the amorphous silicon film 2 in the drive circuit portion to obtain a polycrystalline silicon film 21. For beam annealing, an electron beam is used in addition to a laser beam such as an excimer laser or an Ar laser, and any energy beam that can melt and solidify a silicon film may be used. At this time, since the amount of hydrogen in the film of the amorphous silicon 2 is small, microvoids are not generated, the film is not ablated, and high energy can be irradiated.

Next, as shown in FIG. 1C, the amorphous silicon film 2 of the pixel switching TFT is hydrogenated. For hydrogenation, a method of performing plasma treatment in an atmosphere containing hydrogen is used. The hydrogenation condition at this time is RF power 1.45.
kW, temperature 300 ° C, processing time 60 minutes, gas pressure 1.5T
oor. Further, hydrogenation may be performed by using a method of generating hydrogen radicals by using microwaves other than plasma or a method of generating atomic hydrogen by using a tungsten filament. By such a treatment, the dangling bond in the amorphous silicon 22 is terminated with hydrogen to reduce the leak current. Further, not only the pixel switching TFT but also the polycrystalline silicon 21 of the drive circuit portion obtained by beam annealing may be hydrogenated at the same time. By terminating the dangling bonds at the crystal grain boundaries of the polycrystalline silicon film with hydrogen, a polycrystalline silicon TFT having higher mobility and lower threshold voltage can be obtained. The hydrogenation of the silicon film at this time is 3 × 10 ²⁰ atom
The leak current, which is a required characteristic of the pixel switching TFT, is 10 ^-12 s / cm ^{3 to} 6 × 10 ²⁰ atoms / cm ^3.
It is preferable because it satisfies A or less.

After the layers to be the active layers of the amorphous silicon TFT and the polycrystalline silicon TFT are formed in this way, the amorphous silicon 22 and the polycrystalline silicon 21 are patterned, and the gate insulating film 3 / A gate electrode 4 is deposited, and a P-type source is ion-implanted at a dose amount of 1 × 10 ⁻¹⁵ cm ⁻² and an accelerating voltage of 80 keV on both sides of the channel region of the amorphous silicon 22 and the polycrystalline silicon 21. Then, the source 23 and drain 24 regions are formed. SiO2, SiNx or the like is used for the gate insulating film 3, and an n ⁺ poly-Si film is used for the gate electrode. Finally, the interlayer insulating film 5 and the metal film 6 to be the wiring are deposited and processed, and
The TFT shown in (d) is completed. Si is used for the interlayer insulating film 5.
O2, SiNx, etc. are used, and Mo, Al, T are used for the metal film 6 for wiring.
Refractory metals such as a and Cr and their silicides are used.

FIG. 2 shows the relationship between the field effect mobility and the amount of hydrogen in the film before beam annealing. Here, the mobility is the maximum value obtained when the film is crystallized by beam annealing in a range of irradiation energy that does not ablate the amorphous silicon film. Hydrogen concentration in the amorphous silicon film is 5 × 10 ²⁰ at
It can be seen that if it is oms / cm ³ or less, a high mobility polycrystalline silicon TFT satisfying the specification conditions of the drive circuit of the 10-inch TFT-LCD can be obtained. As described above, according to the manufacturing method of this embodiment, the amorphous silicon T having a low leakage current is used.
The FT and the high mobility polycrystalline silicon TFT can be easily formed on the same substrate.

By forming the 10-inch type TFT-LCD by the above-described manufacturing method, the conventional method is used as compared with the conventional case in which the active layers of the driving circuit TFT and the pixel TFT are separately formed. After the active layer of the driving circuit TFT is formed, a mask is formed on this film, and the exposure process required for the mask formation and the process of forming the active layer of the pixel TFT are all unnecessary. In the example, even if the number of hydrogen treatment steps is increased, the number of steps can be significantly reduced. Moreover, the basic advantage that the driving TFT and the pixel TFT can be simultaneously formed on one glass substrate can be achieved at the same time. (Second Embodiment) FIG. 3 shows a second embodiment of the present invention. Less than,
The same parts as those in the first embodiment are designated by the same reference numerals, and the details are omitted.

First, a conductive film 7 is deposited on an insulating substrate 1 and patterned by etching into a gate electrode shape, and then a laminated film of a gate insulating film 3 / amorphous silicon film 2 is formed. A refractory metal such as Mo, Ta, or Cr that can be used as a gate electrode material of a TFT or its silicide is used for the conductive film 7, and SiO2, SiNx or the like is used for the gate insulating film 3. In some cases, the surface of the gate electrode 7 may be anodized. As the amorphous silicon film 2, the amorphous silicon film 2 having a hydrogen concentration in the film of 3 × 10 ²⁰ atoms / cm 3 is used (FIG. 3A).

Next, only the amorphous silicon film 2 in the drive circuit portion is beam-annealed and crystallized to obtain a polycrystalline silicon film 21. The conditions at this time are the same as in Example 1 (FIG. 3B).

Further, the amorphous silicon film 2 of the pixel switching TFT is hydrogenated. The hydrogenation conditions are the same as in Example 1. By such a treatment, the dangling bond in the amorphous silicon 22 is terminated with hydrogen to reduce the leak current. Further, not only the pixel switching TFT but also the polycrystalline silicon 21 of the drive circuit portion obtained by beam annealing may be hydrogenated at the same time (FIG. 3C).

Next, a nitride film 8 of SiNx or the like for preventing the etching of the channel portions 21 and 22 is deposited by the CVD method and then patterned (FIG. 3D). Finally, the n ⁺ film 9 / metal film 6 is formed as shown in FIG. As the n ⁺ film 9, an n ⁺ a-Si film or a polycrystalline n ⁺ Si film is used.

As described above, the 10-inch TFT-L
When the CD is formed, the same effect as that of the first embodiment can be obtained. The present invention is not limited to the above embodiments, but can be variously modified as follows without departing from the gist thereof. (1) In the above two embodiments, the n-channel TFT has been described as an example, but the p-channel can be similarly manufactured by reversing the conductivity type of the source / drain regions. (2) The present invention can be applied not only to the liquid crystal display device but also to other semiconductor devices such as an image sensor and a printer head which form a polycrystalline silicon TFT and an amorphous silicon TFT on the same substrate.

[0025]

As described above, according to the present invention, there is provided a method for manufacturing a semiconductor device in which an amorphous silicon TFT having a small leak current and a polycrystalline silicon TFT having a high mobility are easily manufactured on the same substrate. be able to.

[Brief description of drawings]

1A to 1C are cross-sectional views in order of steps of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the first embodiment of the present invention.

3A to 3C are cross-sectional views in order of steps of Embodiment 2 of the present invention.

4A to 4C are cross-sectional views in the order of steps of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Amorphous silicon film of low hydrogen concentration 3 ... Gate insulating film 4 ... Gate electrode 5 ... Interlayer insulating film 6 ... Metal film 7 ... Conductive film 8 ... Nitride film 9 ... N ⁺ Si film 20 ... 12at Amorphous silicon film containing.% Hydrogen 21 ... Polycrystalline silicon film 22 ... Hydrogenated amorphous silicon film 23 ... Source region 24 ... Drain region

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/336

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device comprising a mixture of an amorphous silicon thin film transistor in which an active layer is formed from an amorphous silicon thin film formed on the same substrate and a polycrystalline silicon thin film transistor in a mixed manner. × 1
A step of depositing an amorphous silicon film of 0 ²⁰ atoms / cm ³ or less on the substrate to form an active layer of the amorphous silicon thin film transistor, and thereafter, the amorphous silicon of the amorphous silicon film. A step of performing beam annealing on an amorphous silicon film different from the active layer of the thin film transistor to convert it into polycrystalline silicon to form the active layer of the polycrystalline silicon thin film transistor, and then hydrogenating the active layer of the amorphous silicon thin film transistor. A method of manufacturing a semiconductor device, comprising: