JP3428767B2 - Deposition method of polycrystalline Si thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for depositing a polycrystalline Si thin film. More specifically, it relates to a method for depositing a polycrystalline Si thin film having good crystallinity and high conductivity.

[0002]

2. Description of the Related Art Conventionally, there have been the following two methods (a) and (b) for depositing a polycrystalline Si thin film. (A) A gas such as SiH ₄ is blown onto a substrate heated to a high temperature, and the gas is decomposed to generate a deposition species,
A thermal CVD method for forming a polycrystalline Si thin film on a substrate. (B) By the CVD method or the glow discharge plasma decomposition method,
An amorphous Si film or a polycrystalline Si film with a small grain size produced on a substrate is laser-irradiated, infrared-irradiated, or is heated and melted in an electric furnace or the like, and then cooled to form a substrate. A method combining a CVD method for forming a polycrystalline Si thin film and an annealing treatment.

However, the above methods (a) and (b) require heat treatment at about 1000 ° C. or higher when producing a polycrystalline Si thin film. Therefore, there is a problem that ordinary glass or metal cannot be used as a substrate for forming a polycrystalline Si thin film. Therefore, 50
A method of depositing a polycrystalline Si thin film by a low temperature process of 0 ° C. or lower has been desired.

As a method of realizing the above-mentioned low temperature process, for example, a method (c) of decomposing gas by using discharge or light instead of heat has been devised.

As a typical gas decomposition method, there are a plasma CVD method and a photo CVD method. The plasma CVD method is superior to the photo CVD method in that the film deposition rate is high. Usually, in these methods, SiH ₄ gas, S
When the raw material gas such as iF ₄ gas and Si ₂ H ₆ gas is largely diluted with H ₂ gas and the discharge power is increased, a polycrystalline Si thin film can be formed even on a substrate at a low temperature of 300 to 450 ° C.

However, the polycrystalline Si thin film produced by the above method (c) also contains a large amount of amorphous Si portions. Therefore, the photoelectric conversion characteristics are poor and the crystal grain size is 5
There was a problem that it was 0 or less. The reason is believed to be that the deposited species formed by the non-equilibrium reaction of glow discharge plasma fall on the substrate and are taken into the film, so that the structural relaxation of the formed thin film is not sufficiently performed. .
Therefore, there has been a demand for a method of depositing a polycrystalline Si thin film that can sufficiently perform the above structural relaxation while maintaining a low temperature process.

As a method of simultaneously realizing the above-mentioned low temperature process and structural relaxation, for example, during the film formation, the supply of the raw material gas is stopped midway, or the raw material gas is not supplied. By moving the substrate to another plasma space, the deposition of the thin film is stopped periodically, and the surface of the thin film in the process of film formation is exposed to H ₂ plasma to relax the structure by the chemical annealing action of atomic hydrogen. A method (d) for improving the crystallinity of the thin film is proposed.

However, in the polycrystalline Si thin film produced by the above method (d), a doping gas such as PH ₃ , B ₂ H ₆ or BF ₃ is mixed in the source gas to produce an n-type or p-type polycrystalline film. When producing a Si thin film, the crystallization rate of the thin film is remarkably reduced, and it is difficult to obtain a good n-type or p-type polycrystalline Si thin film. However, the polycrystalline S is prepared by using only the source gas without mixing the doping gas.
When an i thin film was produced, a film with good crystallinity was obtained.

Therefore, even when a doping gas is mixed with a source gas to produce an n-type or p-type polycrystalline Si thin film, a method of depositing a polycrystalline Si thin film having good crystallinity has been desired.

[0010]

DISCLOSURE OF THE INVENTION According to the present invention, the structure of a thin film can be sufficiently relaxed while maintaining a low temperature process, and a doping gas is mixed with a source gas,
An object of the present invention is to provide a deposition method by which a polycrystalline Si thin film having good crystallinity can be obtained even when producing an n-type or p-type polycrystalline Si thin film.

[0011]

The method of depositing a polycrystalline Si thin film according to the present invention comprises applying a microwave power to hydrogen gas in another space adjacent to a film forming space to generate a pre-generated atomic state. In a deposition method of decomposing a source gas and a doping gas using hydrogen to generate radicals for forming a film, thereby forming a polycrystalline Si thin film on the surface of a substrate in the film formation space, the hydrogen gas Is always flowed, the raw material gas and the doping gas are temporally divided and introduced into the separate space where the microwave power is always applied, and the raw material gas and the hydrogen gas are flowing. time (t _1), the doping gas and the hydrogen time gas is flowing (t _2), and is deposited by repeating three times consisting of the time only hydrogen gas is flowing (t ₃₎ Characterized by That.

In the method of depositing a polycrystalline Si thin film of the present invention, t ₃ is preferably 10 seconds or more and 50 seconds or less.

Further, in the method for depositing a polycrystalline Si thin film of the present invention, the source gas is SiF ₄ or SiH.
₄ is PH ₃ or BF ₃ as the doping gas.
Is preferably used.

[0014]

[Action]

(Claim 1) In the invention according to claim 1, hydrogen gas is constantly flowed and microwave power is always applied in another space adjacent to the film formation space during thin film formation. is there. In this state, the source gas and the doping gas were introduced into the separate space intermittently and with a temporal shift.

As a result, film formation is performed while the source gas and hydrogen gas are flowing (t ₁ ), impurity diffusion is performed while the doping gas and hydrogen gas are flowing (t ₂ ), and only hydrogen gas is flown. During this time (t ₃ ), it became possible to perform hydrogen plasma treatment on the film surface.

Therefore, by the time-divisional process of flowing this gas, the structure of the thin film can be sufficiently relaxed while the low temperature process is maintained, and the doping gas is mixed with the source gas to form the n-type or p-type. Even in the case of producing the polycrystalline Si thin film, the deposition method capable of forming the polycrystalline Si thin film having good crystallinity was obtained.

(Aspect 2) In the invention according to aspect 2, since the t ₃ is 10 seconds or more and 50 seconds or less, a deposition method capable of forming a polycrystalline Si thin film having good crystallinity and high conductivity. was gotten.

(Claim 3) In the invention according to claim 3, since the raw material gas is SiF ₄ or SiH ₄ , a polycrystalline Si thin film is formed which is characterized by low manufacturing cost and good crystallinity. A possible deposition method was obtained.

(Claim 4) In the invention according to claim 4, since the doping gas is PH ₃ or BF ₃ , the manufacturing cost is low, the crystallinity is good, and the conductivity is high. A deposition method capable of forming a crystalline Si thin film was obtained.

[0020]

[Example embodiment]

(Deposition Method for Forming Polycrystalline Si Thin Film) As a deposition method for forming a polycrystalline Si thin film in the present invention, for example, FIG.
And those shown in FIG. 2. FIG. 1 is a time chart of the present deposition method, and FIG. 2 is a schematic diagram of a film forming apparatus used in the present deposition method.

In the following, with reference to FIG. 1, the timing of introducing three kinds of gas and the timing of applying microwave power will be described.

In another space adjacent to the film-forming space during thin film formation, hydrogen gas is constantly flown and microwave power is always applied. In this state, the source gas is flowed intermittently. Film formation is performed while the source gas is flowing, and hydrogen plasma treatment is performed while the introduction of the source gas is stopped to relax the structure of the film.

On the other hand, when the doping gas is supplied together with the source gas, the decomposition product of the doping gas or the reaction product of the decomposition product of the doping gas and H radicals, the decomposition product of the source gas or the decomposition of the source gas. The crystallinity of the film is remarkably lowered as compared with the case where the doping gas is not flowed, probably because the gas phase reaction between the reaction product of the product and H radical occurs. In this case, it is difficult to improve the crystallinity even if the hydrogen plasma treatment time per cycle is sufficiently long.

Therefore, in the present invention, as shown in FIG. 1, the introduction of the source gas and the doping gas is staggered in time.
As a result, it was possible to suppress the reaction between the decomposition product of the doping gas and the decomposition product of the source gas in the gas phase, and it was possible to prevent the crystallinity from significantly lowering due to the introduction of the doping gas. .

The details of the film forming apparatus will be described below with reference to FIG. Reference numeral 1 is a vacuum chamber for film formation. Reference numeral 2 denotes an exhaust pipe of the vacuum chamber 1, which is composed of two pipes in order to make the gas flow uniform, and is finally connected to one and connected to the vacuum exhaust device 4. An electric butterfly valve 3 for pressure adjustment is connected in the middle of the exhaust pipe 2, and the degree of opening and closing is adjusted by a pressure adjuster 6 based on a signal from a pressure gauge 5 so that a desired pressure is obtained.

Reference numeral 7 denotes a substrate support, on the surface of which a substrate 8 for film formation is placed. A heater block 9 containing a heater 10 is installed on the substrate support 7, and is used for heating the substrate 8 to a desired temperature. Reference numeral 11 is a thermocouple mounted on the heater block 9 to measure the temperature of the heater block 9. In order to bring the surface temperature of the substrate 8 to a desired temperature, the temperature controller 12 controls the temperature of the heater block 9 to a predetermined value that is calibrated in advance.

Numeral 13 is a bellows tube which is mounted so that the position of the substrate support base 7 can be moved in the vertical direction in FIG. The substrate support base 7 is electrically connected to the vacuum chamber 1.

Reference numeral 15 denotes a microwave cavity into which the gas introduced from the gas introduction pipe 16 is introduced through the microwave introduction window 28. It is excited by microwave power to generate plasma glow discharge and generate atomic hydrogen.

Reference numeral 17 denotes a flow rate controller for controlling the flow rate of hydrogen gas, which is connected to a pressure regulator (not shown) for hydrogen gas and a hydrogen gas cylinder (not shown) by a gas pipe 19 via a valve 18. There is.

The produced atomic hydrogen collides with the source gas and the doping gas introduced from the ring-shaped gas blowing pipe 20, and decomposes and reacts with the source gas and the doping gas to have a film depositing ability. Generate radicals.

Reference numeral 21 denotes a gas introduction pipe for introducing gas into the gas blowing pipe 20, which is divided into two on the way and is connected to a source gas flow controller 22 and a doping gas flow controller 25, respectively.

The raw material gas flow rate controller 22 is connected to a raw material gas pressure regulator (not shown) and a raw material gas cylinder (not shown) by a gas pipe 24 via a valve 23. The doping gas flow controller 25 is connected to a doping gas pressure regulator (not shown) and a doping gas cylinder (not shown) by a gas pipe 27 via a valve 26.

29 is a tapered conversion waveguide,
It is tapered so that the microwave power is less lost and is introduced into the microwave cavity 15. Reference numeral 30 denotes a waveguide for microwave power monitoring, to which a detector 31 for incident power monitor and a detector 33 for reflected power monitor are attached. The detectors 31 and 33 are connected to meters 32 and 34, respectively, so that incident power and reflected power can be monitored.

Reference numeral 35 denotes a microwave matching device, which is used for matching with a load. Reference numeral 36 is a waveguide for connection. An isolator 37 prevents reflected power from entering the microwave power source 38.

(Raw material gas) The raw material gas in the present invention includes, for example, a hydride containing a Si element, a halide, or a Si hydride in which a part of hydrogen is halogenated. Specifically, SiH ₄ , Si ₂ H ₆ , Si _{3
H 8, SiF 4, Si 2} F 6, SiCl 4, Si 2 Cl 6, S
Typical examples are iH ₂ Cl ₂ , SiH ₂ F ₂ , SiHCl ₃ , and SiHF ₃ .

(Doping Gas) As a doping gas for producing the n-type Si film in the present invention, for example, a gas containing an element of Group V of the periodic table can be mentioned. Specifically, PH ₃ , PF ₅ , PF ₃ , AsH ₃ , AsF ₃ ,
AsF ₅ , PCl ₃ , PCl ₅ , AsCl ₃ , AsCl ₅ ,
_{C 4 H 11 P, C 4} H 11 As and the like are used. Further, as a doping gas for forming the p-type Si film, for example, a gas containing a Group III element of the periodic table can be mentioned. Specifically, BF ₃ , B ₂ H ₆ , Al (CH ₃ ) ₃ , A
l (C ₂ H ₅ ) ₃ , BCl ₃ , BBr ₃ , B (CH ₃ ) ₃ , B
(C ₂ H ₅ ) ₃ or the like is used.

(Evaluation of Crystallinity) For the evaluation of crystallinity in the present invention, for example, X-ray diffraction method and Raman spectroscopy method were used.

In the X-ray diffraction method, the Si (220) plane,
Each diffraction intensity due to the (111) plane and the (311) plane was examined.

In Raman spectroscopy, a device whose light source was an Ar ⁺ laser was used. The reason why Raman spectroscopy was performed in combination with the X-ray diffraction method is to investigate how the measurement results of the X-ray diffraction method relate to the actual crystal structure. The ratio of crystallization is estimated from the measurement results of Raman spectroscopy, that is, the integrated intensity ratio of the sharp peak near 520 cm ⁻¹ due to crystalline Si and the broad peak near 480 cm ⁻¹ due to amorphous Si. did.

The fact that the sharp peak near 520 cm ^-1 is due to crystalline Si was identified by measuring a crystalline Si wafer. Similarly, the fact that the broad peak near 480 cm ⁻¹ is due to amorphous Si was identified by measurement of an amorphous Si film produced by glow discharge plasma using ordinary SiH ₄ gas. The structures of the crystalline Si wafer and the amorphous Si film were also confirmed by electron beam diffraction images.

In the sample manufactured by the deposition method of the present invention, the ratio of crystallization in the Raman spectroscopic measurement was increased, and therefore, from the (220) plane of Si in the X-ray diffraction measurement. The result that the diffraction intensity was increased was obtained. Moreover, the film thickness of the sample is 700 nm to 900 n.
In the range of m, when the diffraction intensity from the (220) plane of Si exceeds 300 counts / second (abbreviated as cps hereinafter), the Raman spectroscopic measurement shows that 480 cm ⁻¹ due to amorphous Si. No longer detected. From this result, it was determined that the sample in which the X-ray diffraction intensity of 300 cps or more was obtained was almost 100% crystallized.

Therefore, in view of the crystallization rate, a desirable polycrystalline Si thin film has a film thickness of 700 nm to 900 nm.
In the range of 1, the sample has a diffraction intensity from the Si (220) plane of 300 cps or more.

(Evaluation of Conductivity) The four-terminal method was used to evaluate the conductivity in the present invention. Examples 1 to 1 of the present invention
Under each film forming condition of No. 4, P actually incorporated in the Si film
The amount of (phosphorus) or B (boron) is the same in the measurement using a secondary ion mass spectrometer (SIMS), that is, 1 to 2 × 10 ¹⁹ cm ^−3.
However, the conductivity of each sample was significantly different.

On the other hand, the maximum conductivity of the amorphous Si film produced by glow discharge plasma using ordinary SiH ₄ gas is 2 S / cm for the N type sample doped with P (phosphorus), and B ( It was 2 × 10 ⁻³ S / cm for the P-type sample doped with boron).

Therefore, in the present invention, P (phosphorus) is
The conductivity of the lapped N-type sample is more than 2 S / cm.
Consider the conditions for obtaining a large polycrystalline Si thin film deposition method.
It was Similarly, in the case of P type doped with B (boron),
The sample has a conductivity of 2 × 10 ^-3Multiple connections larger than S / cm
The conditions under which the deposition method of the crystalline Si thin film was obtained were examined.

[0046]

【Example】

(Example 1) In this example, as shown in FIG. 1, the effect of introducing the source gas and the doping gas into the film formation space by temporally dividing them will be examined. A polycrystalline Si thin film doped with P (phosphorus) was deposited on a glass substrate using the film forming apparatus shown in FIG.

The method for producing a polycrystalline Si thin film will be described below in accordance with the procedure. (1) After cleaning Na-free (sodium) glass with an organic solvent (acetone and isopropyl alcohol), it is attached to the substrate support 7 and the chamber 1 is evacuated to a pressure of 3 × 10 ⁻⁶ Torr or less with a vacuum exhaust device. It was Further, the substrate 8 was heated by a heater so that the surface temperature of the substrate 8 became 350 ° C. (2) Flow control device 1 for H ₂ gas from gas introduction pipe 16
Flowed through 7 through 15 sccm. Using a pressure controller (not shown), set the internal pressure of chamber 1 to 400 mT
set to orr. (3) When the internal pressure of the chamber 1 was stabilized at 400 mTorr, 400 W of microwave power was applied to generate glow discharge plasma by hydrogen gas. When the discharge became stable, the next film forming process was started. (4) The film forming process is composed of the following three processes, which are repeated 90 times in the order of →→→, and P
A (Si) -doped polycrystalline Si thin film was deposited. As a source gas, SiF ₄ gas (flow rate 100 scc
m) is introduced into the chamber 1 through the gas blowing pipe 20 for 10 seconds to deposit a polycrystalline Si thin film. The introduction of the source gas into the chamber 1 was stopped, and PH ₃ gas (flow rate 1 sccm) diluted to 2% with H ₂ gas was introduced as a doping gas into the chamber 1 for 10 seconds from the gas blowing pipe 20 to deposit the gas. Dope the film with P (phosphorus). Stop introducing the doping gas into the chamber 1,
Only hydrogen gas is introduced into the chamber 1 for 10 seconds, and the surface treatment of the deposited film is performed by hydrogen plasma.

The amount of hydrogen gas introduced and the microwave power applied were not particularly changed in each of the processes. (5) The sample manufactured by the steps (1) to (4) above was taken out of the chamber 1 after the film formation was completed, by lowering the substrate temperature to room temperature.

Comparative Example 1 In this example, the process in the film forming step was omitted, and the process was repeated 90 times in the order of →→, and a polycrystalline Si thin film not doped with P (phosphorus) was deposited. different. The other points were the same as in Example 1.

Comparative Example 2 This example is different from Example 1 in that the following process was performed instead of the process in the film forming process. That is, in Example 1, the source gas and the doping gas were temporally divided and introduced into the film forming chamber, but in the present example, the source gas and the doping gas were used at the same time. Therefore, in this example, 9 → 9
Repeated 0 times, P (phosphorus) -doped polycrystalline Si
A thin film was deposited. SiF ₄ gas (flow rate 100 sccm) and PH ₃ gas diluted with H ₂ gas to 2% (flow rate 1 sccm) were introduced into the chamber 1 at the same time from the gas blowing pipe 20.
Introduced for seconds, while doping P (phosphorus), polycrystalline S
i Deposit thin film. The other points were the same as in Example 1.

In the following, two evaluations performed on each of the samples prepared in Example 1, Comparative Example 1 and Comparative Example 2, namely, evaluation of crystallinity by X-ray diffraction method and conductivity by four-terminal method The results of rate evaluation are described. However, the film thickness of each sample was in the range of 750 nm to 800 nm.

(1) Crystalline Evaluation Results by X-ray Diffraction Method Table 1 shows the measurement results of each sample. Example 1 and Comparative Example 1
In the sample of (2), an extremely large peak at (220), (1
Small peaks were observed at 11) and (311). On the other hand, in the sample of Comparative Example 2, only a small peak at (220), that is, a peak almost hidden by the background was confirmed.

From these results, it was found that an extremely good polycrystalline Si thin film could be produced when no dopant was mixed (Comparative Example 1).

However, it can be seen that when the doping gas is mixed in the source gas (Comparative Example 2), the crystallinity is extremely lowered.

However, when the introduction of the source gas and the doping gas is temporally separated, and then the film is formed by repeating the step of performing the hydrogen plasma treatment (Example 1),
It was found that the crystallinity of the thin film obtained without doping (Comparative Example 1) can be maintained.

[0056]

[Table 1]

(2) Evaluation results of conductivity by four-terminal method Table 2 shows the measurement results of each sample. From Table 2, Comparative Example 1
It was also found that the sample of Example 1 having higher crystallinity also had excellent conductivity as compared with Comparative Example 2.

[0058]

[Table 2]

Example 2 This example is different from Example 1 in that the time of one hydrogen plasma treatment was changed. The time for one hydrogen plasma treatment is 0 seconds, 5 seconds, 10 seconds.
Seven conditions of seconds, 20 seconds, 30 seconds, 50 seconds, and 60 seconds were examined. However, the film thickness of each sample was in the range of 700 nm to 800 nm. The other points were the same as in Example 1.

FIG. 3 shows the results of the evaluation of the crystallinity by the X-ray diffraction method and the evaluation of the conductivity by the four terminal method. From FIG. 3, polycrystalline S having a conductivity of more than 2 S / cm
It was found that the time for one hydrogen plasma treatment for obtaining the i thin film deposition method was 10 seconds or more and 50 seconds or less.

Example 3 In this example, BF ₃ diluted with H ₂ to 2% was used as a doping gas, and the flow rate was 15 s.
The difference from Example 1 is that it is ccm. The other points were the same as in Example 1.

Comparative Example 3 In this example, BF ₃ diluted with H ₂ to 2% was used as a doping gas, and the flow rate was 15 s.
It differs from Comparative Example 2 in that it is set to ccm. The other points were the same as in Comparative Example 2.

In the following, the results of two evaluations performed on each sample prepared in Example 3 and Comparative Example 3, namely, evaluation of crystallinity by X-ray diffraction method and evaluation of conductivity by four-terminal method State. However, the sample film thickness of Example 3 was 730 nm, and the sample film thickness of Comparative Example 3 was 720 nm.

From the above-mentioned evaluation result of crystallinity, it was confirmed that the sample of Example 3 was a good polycrystalline Si thin film because a large peak (900 cps) was observed at (220). On the other hand, no peak was observed in the sample of Comparative Example 3.

Further, in the above-mentioned evaluation of conductivity, the sample of Example 3 had a conductivity of 1.8 S / cm. On the other hand, the sample of Comparative Example 3 was 6 × 10 ⁻⁵ S / cm.

(Embodiment 4) In this embodiment, S is used as a source gas.
It differs from Example 1 in that a polycrystalline Si thin film doped with P is deposited using iH ₄ .

Below, a method for producing a polycrystalline Si thin film will be described according to procedures. (1) After cleaning Na-free (sodium) glass with an organic solvent (acetone and isopropyl alcohol), it is attached to the substrate support 7 and the chamber 1 is evacuated to a pressure of 3 × 10 ⁻⁶ Torr or less with a vacuum exhaust device. It was Further, the substrate 8 was heated by a heater so that the surface temperature of the substrate 8 became 450 ° C. (2) Flow control device 1 for H ₂ gas from gas introduction pipe 14
Flowed through 300 through 300 sccm. Using a pressure controller (not shown), set the internal pressure of chamber 1 to 100 mT
set to orr. (3) When the internal pressure of the chamber 1 was stabilized at 100 mTorr, microwave power of 500 W was applied to generate glow discharge plasma by hydrogen gas. When the discharge became stable, the next film forming process was started. (4) The film-forming process consists of the following three processes, which are repeated 150 times in the order of →→→
A polycrystalline Si thin film doped with P (phosphorus) was deposited. As a source gas, SiH ₄ gas (flow rate 20 scc
m) is introduced into the chamber 1 through the gas blowing pipe 20 for 10 seconds to deposit a polycrystalline Si thin film. PH ₃ gas (flow rate 0.2 sccm) diluted to 2% with H ₂ gas is introduced as a doping gas into the chamber 1 through the gas blowing pipe 20 for 10 seconds to dope P (phosphorus) into the deposited film. Only hydrogen gas is introduced into the chamber 1 for 30 seconds, and the surface treatment of the deposited film is performed by hydrogen plasma.

The amount of hydrogen gas introduced and the power applied to the microwaves were not particularly changed in each of the processes. (5) The sample manufactured by the steps (1) to (4) above was taken out of the chamber 1 after the film formation was completed, by lowering the substrate temperature to room temperature.

Comparative Example 4 This example is different from Example 4 in that the following process was performed instead of the process in the film forming process. That is, in Example 4, the source gas and the doping gas were temporally divided and introduced into the film forming chamber, but in the present example, the source gas and the doping gas were used simultaneously. Therefore, in this example, the order of →→ is 1
Repeated 50 times, polycrystalline S doped with P (phosphorus)
An i thin film was deposited. 2 with SiH ₄ gas (flow rate 20 sccm) and H ₂ gas
% PH ₃ gas (flow rate 0.2 sccm),
At the same time from the gas blowing pipe 20 into the chamber 1
It is introduced for 0 seconds, and a polycrystalline Si thin film is deposited while doping P (phosphorus). The other points were the same as in Example 4.

In the following, the results of two evaluations performed on each sample prepared in Example 4 and Comparative Example 4, namely, evaluation of crystallinity by X-ray diffraction method and evaluation of conductivity by four-terminal method State. However, the sample film thickness of Example 4 was 750 nm, and the sample film thickness of Comparative Example 4 was 740 nm.

Regarding the X-ray diffraction pattern, in the sample of Example 4, the diffraction peak intensity of (220) was as strong as 1050 cps, and other small peaks were observed at (111) and (311). On the other hand, in the sample of Comparative Example 4, none of the peaks could be observed below the background noise.
From this result, it was found that the sample of Example 4 had better crystallinity than the sample of Comparative Example 4.

The conductivity of the sample of Example 4 is 2.8.
The sample of Comparative Example 4 had a S / cm of 8 × 10.
It was ^-1 S / cm. From this result, it was found that the sample of Example 4 having high crystallinity also had high conductivity.

[0073]

【The invention's effect】

(Claim 1) As described above, in the invention according to claim 1, the structure of the thin film can be sufficiently relaxed by the time-divisional process of flowing the source gas and the doping gas while maintaining the low temperature process. Also, when a doping gas is mixed with the source gas to produce an n-type or p-type polycrystalline Si thin film, a deposition method capable of forming a polycrystalline Si thin film with good crystallinity can be obtained.

(Claim 2) In the invention according to claim 2, the crystallinity is better than that of an amorphous Si film prepared by glow discharge plasma using SiH ₄ gas diluted with a large amount of ordinary hydrogen gas, and It is possible to obtain a deposition method capable of forming a polycrystalline Si thin film having high conductivity.

(Claim 3) The invention according to claim 3 provides a deposition method capable of forming a polycrystalline Si thin film, which is characterized by low manufacturing temperature and low manufacturing cost.

(Claim 4) The invention according to claim 4 provides a deposition method capable of forming a polycrystalline Si thin film, which is characterized by good crystallinity and high conductivity under conditions of low fabrication temperature.

[Brief description of drawings]

FIG. 1 is a graph showing a time chart of a deposition method according to the present invention.

FIG. 2 is a schematic view of a film forming apparatus according to the present invention.

FIG. 3 is a graph showing an evaluation result of crystallinity by an X-ray diffraction method according to Example 2 and an evaluation result of conductivity by a four-terminal method.

[Explanation of symbols]

t ₁ raw material gas introduction time for one process, t ₂ doping gas introduction time for one process, t ₃ hydrogen plasma treatment time for one process, 1 vacuum chamber, 2 exhaust pipes, 3 electric butterfly Valve, 4 vacuum exhaust device, 5 pressure gauge, 6 pressure regulator, 7 substrate support, 8 substrate, 9 heater block, 10 heater, 11 thermocouple, 12 temperature controller, 13 bellows tube, 15 microwave cavity, 16 gas Introducing pipe, 17 Flow controller for controlling hydrogen gas flow rate, 18 valve, 19 gas pipe, 20 ring-shaped gas blowing pipe, 21 gas introducing pipe, 22 raw material gas flow controller, 23 valve, 24 gas pipe , 25 doping gas flow controller, 26 valve, 27 gas tube, 29 tapered conversion waveguide, 30 microphone B Waveguide for power monitoring of microwaves, 31 Detector for incident power monitoring, 32, 34 meters, 33 Detector for reflected power monitoring, 35 Microwave matching box, 36 Connection waveguide, 37 Isolator , 38 microwave power supply.

Claims (4)

(57) [Claims] 1. A microwave power is applied to hydrogen gas in another space adjacent to the film formation space, and the source gas and the doping gas are decomposed using atomic hydrogen that is generated in advance,
In the deposition method of forming a polycrystalline Si thin film on the surface of the substrate in the film formation space by generating radicals for film formation, the hydrogen gas was constantly flowed and the microwave power was always applied. The raw material gas and the doping gas are temporally divided and introduced into the separate space in the state, the time (t ₁ ) during which the raw material gas and the hydrogen gas are flowing, the doping gas and the hydrogen gas are A method for depositing a polycrystalline Si thin film, which is characterized in that a film is formed by repeating three kinds of times, which are a flowing time (t ₂ ) and a flowing time (t ₃ ) of only the hydrogen gas. 2. The method for depositing a polycrystalline Si thin film according to claim 1, wherein the t ₃ is 10 seconds or more and 50 seconds or less. 3. The source gas is SiF ₄ or SiH ₄
The method for depositing a polycrystalline Si thin film according to claim 1 or 2, wherein 4. The doping gas is PH ₃ or B
The method for depositing a polycrystalline Si thin film according to claim 1, wherein the method is F ₃ .