JPH0319340A - Manufacturing method of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to form a high-efficiency TFT at a high throughput using a low-temperature process by a method wherein in a method of forming an insulating film on the surface of a semiconductor by a chemical vapor growth method, the concentration of diluent gas, such as helium, neon, argon and xenon gases or the like, is changed to a film-forming time. CONSTITUTION:An SiO2 thin film 203 which is used as a gate insulating film is formed on a polycrystalline silicon thin film 202 made to perform a solid phase growth. In case a PCVD method is used for the film formation of the SiO2 thin film 203, inert gas, such as He gas or the like, is added to the mixed gas of SiH4 gas and N2O gas for reducing damage to the film 203. In the PCVD method, in case He gas is used as diluent gas in the gas flow rate ratio of low-temperature gas, the flow rate of the He gas is changed to a film-forming time. When the flow rate of the He gas is changed, the He gas is brought into a state that its amount of dilution is large in the vicinity of an Si/SiO2 interface, that is, though the damage to the film 203 is very small, the film formation progresses in a state that a film forming speed is slow and as the film formation becomes more distant from the Si/SiO2 interface, the film-forming speed becomes first. By adopting such a film-forming method, a good Si/SiO2 interface is realized as the film-forming time is kept short.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device. [Prior Art] In recent years, insulating amorphous substrates such as glass and quartz, and SiOz
Attempts are being made to form high-performance semiconductor devices on insulating amorphous layers such as those described above. Particularly in large liquid crystal display panels and the like, in order to meet the demand for low cost, it is becoming essential to form thin film transistors (TPT) on inexpensive low melting point glass. Conventionally, Journal was applied to the TPT gate insulating film formed on a low melting point glass substrate.
l of Vacuum Science & Tec
hnology Vol. Ba(2) p. 517 (
1988), Journal of Applied
Phy-sics Vol. 60, p. 3138
(1986) and others, plasma vapor phase epitaxy (
PCVD), Applied Physi
cs Letters Vol. 50(17) p. 1
167 (1987), etc., using low pressure chemical vapor deposition (LPGVD);
cs Letters Vol. 24(3) p.
172 (1988), Japanese Jour-
nal of Applied Physics Vo
l. 26(6) p. 805,835,L908 (1
988), etc., using the photochemical vapor deposition method, Japanese Journal of
Applied Physics Vol. 22(4)
p. ECR as seen in L210 (1983) etc.
There are some that use plasma vapor phase epitaxy, and all of them have used SiC)+ thin films fabricated using low-temperature deposition methods. [Problem to be solved by the invention] However, the formation of the gate oxide film of TPT is performed at a low temperature (600℃).
℃), there was a problem that the film quality was inferior to that of a gate insulating film formed by high-temperature oxidation, and a high-performance TPT could not be achieved. Gate absolute aX film formed at low temperature
The reason for the inferior film performance is the residual stress in the gate insulating film,
This is because defect levels caused by dangling bonds, impurities, etc. exist at the semiconductor/gate insulating film interface, and the depletion layer does not expand. For this reason, T
It was difficult to improve performance with PT. To solve this problem, the Journal of Applied Phys.
icsVol. 60, p. 3138 (1986), when forming a SiO2 film by the pcvD method, H
A method using e-gas as a diluent gas is known. According to this method, PCvDrli. It is possible to significantly reduce plasma damage during ll [time, and to form a high-quality gate oxide film. However, this method requires dilution with a large flow of He, and has the problem that the film formation rate is low and the film formation time is long. The present invention solves the above problems, and its purpose is to manufacture high-performance TPT at high throughput using a low-temperature process. [1000 Steps to Solve the Problems] The method for manufacturing a semiconductor device of the present invention includes forming an insulating film on a semiconductor surface by chemical vapor deposition, in which helium, helium,
It is characterized by changing the concentration of diluent gas such as neon, argon, xenon, etc. with respect to the film formation time. [Example] First, a non-quality semiconductor is deposited on a quartz or glass substrate. In this example, amorphous silicon is used as an example of an amorphous semiconductor. The substrate is S covered with SiO2.
An i-board may also be used. Quartz substrate or SiO2
When using a Si substrate covered with glass, it can withstand a high-temperature process of 1200°C, but when using a glass substrate, the softening temperature is low, so low-temperature processes are limited to about 600°C or less. This will be explained below according to Fig. 2(a). Introduction Non-quality insulating base Fi. An amorphous silicon thin film 202 is deposited on 201. It is desirable that the non-quality silicon thin film 202 is uniform, does not contain minute crystallites, and does not have any nuclei for crystal growth. In the case of low-pressure chemical vapor deposition (LPCVD), conditions are suitable where the film-forming temperature is as low as possible and the film-forming rate is fast. Silane gas (
When using SiH4), the temperature is about 500°C to 560°C, and when using disilane gas (Si2Hs), the temperature is about 300°C to 50°C.
Decomposition deposition is possible at a film formation temperature of around 00'C. Trisilane gas (Si3H●) has a lower decomposition temperature.If the film formation temperature is increased, the deposited film becomes polycrystalline, so Si
Another method is to temporarily make it amorphous by ion implantation. In the case of plasma chemical vapor deposition (PCVD), films can be formed even when the substrate temperature is 500°C or less. Furthermore, if hydrogen plasma or argon plasma treatment is performed immediately before film formation, cleaning of the substrate surface and film formation can be performed continuously. The photo-excited CVD method is also effective in that it can form a film at a low temperature of 500°C or less and can continuously perform cleaning of the substrate surface and film formation. In the case of high-vacuum deposition methods such as electron beam evaporation, since the film is a bolus, oxygen from the atmosphere is easily incorporated into the film, which hinders crystal growth. To prevent this, before removing from the vacuum atmosphere,
It is effective to densify the film by performing low-temperature heat treatment at around 0°C. In order to improve the performance of TPT, it is desirable to perform an annealing process to elongate the semiconductor thin film in a solid state on the semiconductor thin film produced as described above. The solid phase growth method is
Furnace annealing using a quartz tube is convenient. The annealing atmosphere uses nitrogen gas, hydrogen gas, argon gas, helium gas, etc. 1×10-6 to IXIO-”T
Annealing may be performed in a high vacuum atmosphere of orr. The solid phase growth annealing temperature is approximately 500°C to 700°C. Low-temperature annealing selectively grows only crystal grains with crystal orientations that have low activation energy for crystal growth. Si that becomes the gate insulating film is grown on the silicon thin film grown in solid phase.
200 to 1,500 people deposit O2 thin films. When using the PCVD method to form a SiO2 film, a mixed gas of SiH4 and nitrous oxide gas (N20) is used. To reduce damage to the film, an inert gas such as He is added to the SiHz and N20 mixture gas. Among the inert gases, He, which has the smallest atomic weight, is preferable because it causes the least plasma damage. When using 81 nitride film for the gate insulating film, SiH4, nitrogen gas (N2) or ammonia gas (
NH3), and in addition to this, an inert gas such as He is used as a diluent gas. In optical CVD, Si2Hs, SitH● gas, etc. are used instead of SiHa, P
In CVD, when He is used as the diluent gas, the gas flow rate ratio of the film-forming gas is SiHn/N20/He=1/1 in the initial state.
25/4000, and the flow rate of He gas is varied according to the film forming time according to the curve shown in FIG. The flow rate was controlled by a mass flow controller controlled by a microcomputer. The substrate temperature is 50-6
50℃, RF power is 10~40mW/c
m'' range is desirable. As shown in Figure 1, when the He flow rate is changed, near the S i / S i O 2 interface, He is in a state where the dilution I is large, that is, the damage to the film is extremely small, but it is difficult to form a film. Film formation progresses at a slow rate, and S
The film formation rate increases as the distance from the i/SiO2 interface increases. By adopting such a film formation method,
Good S i / 3 i while keeping the deposition time short
02 interface can be realized. Eoo~1000 SiO2 layers are formed in a film formation time of about 10 minutes. It is desirable to heat-treat the SiOz film formed in this way at a temperature of 300 to 500°C in a vacuum or in an inert gas because the film becomes denser. An example in which a polycrystalline silicon thin film produced using the present invention is applied to a thin film transistor will be explained with reference to FIG. Figure 2(a) shows a polycrystalline silicon thin film substrate. 20
1 is an insulating substrate, and 202 is a polycrystalline silicon thin film. 2
03 is SiO2 of the gate insulating film produced by the method described above. Next, the silicon thin film is patterned by photolithography to form an island shape as shown in FIG. 2(b). Next, as shown in FIG. 2(C), the gate electrode 2
Form 04. The gate electrode material may be a polycrystalline silicon thin film, molybdenum silicide, a metal film such as aluminum or chromium, or a polycrystalline silicon thin film.
A transparent conductive film such as O or Sn02 can be used. Film forming methods include CVD, sputtering, vacuum evaporation, etc., but detailed explanations are omitted here. Subsequently, as shown in FIG. 3(d), the gate electrode 20
4 as a mask, impurity ions are implanted to form a source region 205 and a drain region 206 in a self-aligned manner. As the impurity, P0 or As9 is used when producing an Nch transistor, and B' or the like is used when producing a Pch transistor. In addition to ion implantation, methods for adding impurities include laser doping and plasma doping. The arrow 207 represents the impurity ion beam. When a quartz substrate is used as the amorphous insulating substrate 201, a thermal diffusion method can be used. The impurity concentration is IXI
From O" to IXIO" cm-g. Subsequently, as shown in FIG. 2(e), an interlayer insulating film 20 is formed.
Layer 8. As the interlayer insulating film material, an oxide film or a nitride film is used. As long as the insulation is good, the film thickness can be any thickness, but it is usually from several thousand to several micrometers.
A simple method for forming the nitride film is the LPCVD method or the plasma CVD method. For the reaction, a mixed gas of ammonia gas, silane gas, and nitrogen gas, or a mixed gas of silane gas and nitrogen gas is used. If hydrogen ions are introduced using a method such as a hydrogen plasma method, a hydrogen ion implantation method, or a hydrogen diffusion method from a plasma nitride film, defects such as dangling bonds that exist at the gate oxide film interface will be terminated. It will be done. Such a hydrogenation step may be performed before laminating the interlayer insulating film 208. Next, as shown in FIG. 2(f), contact holes are formed in the interlayer insulating film and the gate insulating film, contact electrodes are formed, and a source electrode 209 and a drain electrode 210 are formed.
Suppose that The source electrode and drain electrode are formed of a metal material such as aluminum. In this way, a thin film transistor is formed. [J! [Bright Effect] When a thin film transistor is made using the large-grain polycrystalline silicon thin film obtained by the present invention, excellent characteristics can be obtained. Compared to conventional thin film transistors, the ON current increases and the OFFI current decreases. In addition, the threshold voltage is reduced and transistor characteristics are greatly improved. Since it is possible to fabricate thin film transistors with excellent characteristics on an amorphous insulating substrate, sufficient high-speed operation can be achieved even when applied to an active matrix substrate where a driver circuit is integrated on the same substrate. Furthermore, it has great effects in reducing power supply voltage, reducing current consumption, and improving reliability. In addition, since it can be manufactured using a low-temperature process at temperatures below 600°C, it is highly effective in reducing the cost and increasing the area of active matrix substrates. When the present invention is applied to a contact type image sensor in which a charging conversion element and its scanning circuit are integrated on the same chip, it will have a very large effect in increasing the reading speed, increasing the resolution, and further increasing the gradation. It produces. Once high resolution is achieved, it will be easier to apply it to contact image sensors for color reading. Of course, this has great effects in reducing power supply voltage, reducing current consumption, and improving reliability. Furthermore, since it can be manufactured using a low-temperature process, it is possible to increase the length of the contact image sensor chip, making it possible to realize a reading device for large-sized facsimile machines such as A4 or A3 size with a single chip. Therefore, it is possible to avoid complicated and unreliable techniques such as splicing two sensor chips, and the mounting yield is also improved. In addition to quartz and glass substrates, sapphire substrates (
Al201) or MgO. Al203, BP, Ca
A crystalline insulating substrate such as F2 can also be used. Although the explanation has been given above using a thin film transistor as an example, the present invention can also be applied to elements using thin films such as a bibolar transistor or a heterojunction bibolar transistor. In addition, SO such as a three-dimensional device
The present invention can also be applied to elements using engineering technology. 4. Brief Explanation of Iili Plane FIG. 1 is a diagram showing the change in He gas flow rate with respect to film formation time in the present invention.

FIG. 2 is a diagram showing the manufacturing process of a thin film transistor according to the present invention.

201...Insulating substrate 202...Polycrystalline silicon thin film 203.
......Gate insulating film 204...
- Gate electrode 205... Source region 206... Drain region 207...
...Ion beam 208...Interlayer insulating film 209...Source electrode 210...Drain electrode Figure 1 and above

Claims (1)

[Claims] A method for manufacturing a semiconductor device, which comprises changing the concentration of a diluent gas such as helium, neon, argon, or xenon with respect to film formation time, in a method of forming an insulating film on a semiconductor surface by chemical vapor deposition.