JP2001110727A - Method and device for forming semiconductor thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve the uniformity of film formation in a batch, even at low dose quantity. SOLUTION: This method for forming a semiconductor thin film comprises a first exhausting process for exhausting the inside of a chamber, an impurity gas introducing process for introducing an impurity gas 13 to the chamber after the first exhaustion process, a leasing process for leaving the chamber, to which the impurity gas 13 is introduced for a prescribed time under a prescribed pressure after the impurity gas introducing process, a second exhaustion process for exhausting the inside of the chamber to which the impurity gas is introduced after the left-to-stand process, and a film-forming gas introducing process for introducing cyan system gas 12 to the chamber, after the second exhausting process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor thin film forming method and a film forming apparatus for improving the film forming uniformity in a batch (between wafers) even at a low dose.

[0002]

2. Description of the Related Art A poly-Si layer serving as an active layer of a low-temperature poly-Si TFT (polysilicon thin film transistor) is formed by excimer laser annealing (hereinafter, referred to as "ELA") of an a-Si thin film formed on an amorphous substrate. Or by crystallization by solid phase growth (hereinafter referred to as “SPC”) or the like. Here, the threshold value of the operating voltage (hereinafter referred to as “V _TH ”) in the TFT characteristics is an important value in circuit operation. Therefore, the silicon flat band is controlled by doping impurities such as boron (hereinafter, referred to as "B") or phosphorus (hereinafter, referred to as "P") into the silicon thin film which is the channel portion, and the optimum V _TH Get the value.

Conventionally, ion implantation (hereinafter referred to as "I / I") or ion doping (hereinafter referred to as "I / D") has been employed as a method of doping impurities into a silicon thin film. As a method other than I / I and I / D, a silane-based gas (SiH ₄ , Si ₂ H ₆ etc.) and a doping impurity gas (B ₂ H ₆ , PH ₃ etc.) together with
A method of obtaining an a-Si thin film doped with impurities by epo has been used. This method is called gas phase doping.

The method of forming an a-Si thin film is roughly classified into a method using plasma CVD and a method using LPCVD (low pressure chemical vapor deposition). Here, when the a-Si thin film is formed by LPCVD, it is premised that batch processing (batch processing of a fixed number of wafers) is performed in order to improve throughput. However, in the case of performing a batch process, a variation in film formation within one batch occurs. In particular,
Impurity concentration (dose) to be doped in silicon layer
As the number of particles decreases, the allowable range of variation within a batch decreases, which causes a reduction in manufacturing yield. Thus, a method for improving the film forming uniformity in a batch is disclosed in Japanese Patent Application Laid-Open No. 7-307292.

[0005]

However, even with the method for forming an a-Si thin film disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-307292, the formation of a film in a batch especially at a low dose amount is difficult. There is a problem that the variation is not sufficiently small.

The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to further improve the uniformity of film formation in a batch even at a low dose. It is an object to provide a method for forming a semiconductor thin film to be formed, and a film forming apparatus.

[0007]

According to a first aspect of the present invention, there is provided a method of forming a semiconductor thin film, comprising: introducing a film forming substrate into a chamber of an LPCVD film forming apparatus; In a method for forming a semiconductor thin film containing a desired impurity on a substrate, a first exhaust step of exhausting the chamber after the film formation substrate is introduced into the chamber, and after the first exhaust step, An impurity gas introducing step of introducing an impurity gas into the chamber, a second exhausting step of exhausting the chamber into which the impurity gas has been introduced after the impurity gas introducing step, and an inside of the chamber after the second exhausting step. And a film forming gas introducing step of introducing a film forming gas into the semiconductor thin film.

With this configuration, only the desired impurity gas can be introduced into the chamber, and the chamber can be uniformly filled with the impurity gas. Thus, the impurity can be uniformly attached to the entire surface of the deposition substrate in the chamber which is in contact with the impurity gas regardless of the location in the chamber. Thereafter, by introducing a film formation gas, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the film formation uniformity in the batch can be improved.

According to a second aspect of the present invention, there is provided a method of forming a semiconductor thin film, comprising: introducing a film forming substrate into a chamber of an LPCVD film forming apparatus; A first evacuation step of exhausting the chamber after a film formation substrate is introduced into the chamber; and
A film forming gas introducing step of introducing a film forming gas into the chamber after the evacuation step, a second evacuation step of exhausting the chamber into which the film forming gas has been introduced after the film forming gas introducing step, An impurity gas introducing step of introducing an impurity gas into the chamber after the second evacuation step.

With this configuration, it is possible to form a non-doped semiconductor thin film by introducing only a film forming gas into the chamber. Next, after exhausting the film forming gas in the chamber, only the desired impurity gas is introduced into the chamber,
The chamber can be uniformly filled with the impurity gas. Thus, the impurity can be uniformly attached to the entire surface of the non-doped semiconductor thin film in the chamber in contact with the impurity gas, regardless of the location in the chamber. By terminating the film formation thereafter, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the uniformity of the film formation in the batch can be improved.

Further, a method of forming a semiconductor thin film according to a third invention of the present application provided to solve the above-mentioned problem is a method of manufacturing a semiconductor thin film according to the first or second invention of the present application. Immediately after the step, there is provided a leaving step in which the inside of the chamber into which the impurity gas has been introduced is left for a predetermined time.

According to this structure, the concentration of impurities adhering to the surface of the film-forming substrate or the non-doped semiconductor thin film is saturated with time, and the concentration of impurities adhering to the surface can be stabilized. Thereby, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the uniformity of film formation in the batch can be improved.

[0013] Further, according to a fourth aspect of the present invention, there is provided a method of forming a semiconductor thin film according to the first or second aspect of the present invention. Immediately after the step, there is provided a leaving step in which the inside of the chamber into which the impurity gas has been introduced is left under a predetermined pressure for a predetermined time.

According to a fifth aspect of the present invention, there is provided a method of forming a semiconductor thin film according to the fifth aspect of the present invention. Immediately after the step, there is provided a leaving step of leaving the inside of the chamber into which the impurity gas has been introduced under a pressure of 1 Pa or more and 100 Pa or less for a predetermined time.

According to the fourth or fifth aspect of the present invention, by adopting such a configuration, impurities can be more uniformly attached to the surface of the film-formed substrate or the non-doped semiconductor thin film under a predetermined pressure. Further, by leaving the inside of the chamber for a predetermined period of time, the concentration of impurities adhering to the surface of the film formation substrate or the non-doped semiconductor thin film is saturated with time, and the concentration of impurities adhering to the surface can be stabilized. Therefore, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the uniformity of film formation in the batch can be improved.

Further, a method of forming a semiconductor thin film according to a sixth aspect of the present invention, which is provided to solve the above-mentioned problem, is a method of forming a semiconductor thin film according to any one of the third to fifth aspects of the present invention. , Wherein the predetermined time is one minute or more.

According to this structure, the impurity concentration on the surface of the film-forming substrate or the non-doped semiconductor thin film reaches saturation with the lapse of time by leaving the inside of the chamber for 1 minute or more, and the impurity concentration on the surface becomes higher. Can be stabilized. Therefore, the impurity concentration in the semiconductor thin film becomes more uniform in the batch, and the uniformity of film formation in the batch can be further improved.

Further, a film forming apparatus according to a seventh aspect of the present invention, which is provided to solve the above-mentioned problem, comprises: a LPCVD film forming chamber into which a film forming substrate is introduced; an exhaust means for exhausting the inside of the chamber; In a film forming apparatus having a film forming gas introducing unit for introducing a film forming gas into the chamber and an impurity gas introducing unit for introducing an impurity gas into the chamber, after a film forming substrate is introduced into the chamber, The evacuation unit performs a first evacuation of the chamber, and after the first evacuation of the chamber, the impurity gas introducing unit introduces an impurity gas into the chamber, and the impurity gas is introduced into the chamber. After the gas is introduced, the exhaust unit exhausts the second gas in the chamber, and after the second exhaust gas in the chamber, the film-forming gas introducing unit emits the gas in the chamber. Deposition apparatus characterized by introducing a deposition gas within.

With this configuration, only the desired impurity gas can be introduced into the chamber, and the chamber can be uniformly filled with the impurity gas. Thus, the impurity can be uniformly attached to the entire surface of the deposition substrate in the chamber which is in contact with the impurity gas regardless of the location in the chamber. Thereafter, by introducing a film formation gas, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the film formation uniformity in the batch can be improved.

The film forming apparatus according to the eighth aspect of the present invention, which is provided to solve the above-mentioned problem, is characterized in that an LP in which a film forming substrate is introduced is provided.
A CVD film forming chamber, an exhaust unit for exhausting the inside of the chamber, a film forming gas introducing unit for introducing a film forming gas into the chamber, and an impurity gas introducing unit for introducing an impurity gas into the chamber. In the film forming apparatus, after the film forming substrate is introduced into the chamber, the exhaust unit performs first exhaust in the chamber, and after the first exhaust in the chamber, the film forming gas introducing unit Introduces a film-forming gas into the chamber, and after the film-forming gas is introduced into the chamber, the exhaust means performs a second exhaust in the chamber, and a second exhaust in the chamber is performed. And a step of introducing the impurity gas into the chamber.

With this configuration, a non-doped semiconductor thin film can be formed by introducing only a film forming gas into the chamber. Next, after exhausting the film forming gas in the chamber, only the desired impurity gas is introduced into the chamber,
The chamber can be uniformly filled with the impurity gas. Thus, the impurity can be uniformly attached to the entire surface of the non-doped semiconductor thin film in the chamber in contact with the impurity gas, regardless of the location in the chamber. By terminating the film formation thereafter, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the uniformity of the film formation in the batch can be improved.

According to a ninth aspect of the present invention, there is provided a film forming apparatus according to the ninth aspect, wherein the impurity gas is contained in the chamber. Immediately after the introduction, the film forming apparatus further includes a leaving unit that leaves the inside of the chamber into which the impurity gas has been introduced for a predetermined time.

With such a configuration, the concentration of impurities adhering to the surface of the film-forming substrate or the non-doped semiconductor thin film saturates over time, and the concentration of impurities adhering to the surface can be stabilized. Thereby, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the uniformity of film formation in the batch can be improved.

According to a tenth aspect of the present invention, there is provided a film forming apparatus according to the seventh or eighth aspect, wherein the impurity gas is contained in the chamber. Immediately after the introduction, the film forming apparatus includes a leaving unit that leaves the inside of the chamber into which the impurity gas has been introduced under a predetermined pressure for a predetermined time.

[0025] Further, according to an eleventh aspect of the present invention, there is provided a film forming apparatus according to the eleventh or eighth aspect of the present invention, wherein the impurity gas is contained in the chamber. Immediately after the introduction, the film forming apparatus further includes a leaving unit for leaving the inside of the chamber into which the impurity gas has been introduced under a pressure of 1 Pa or more and 100 Pa or less for a predetermined time.

In the tenth or eleventh invention of the present application,
With such a configuration, impurities can be more uniformly attached to the surface of the film formation substrate or the non-doped semiconductor thin film under a predetermined pressure. Further, by leaving the inside of the chamber for a predetermined period of time, the concentration of impurities adhering to the surface of the film formation substrate or the non-doped semiconductor thin film is saturated with time, and the concentration of impurities adhering to the surface can be stabilized. Therefore, the impurity concentration in the semiconductor thin film becomes uniform in the batch, and the uniformity of film formation in the batch can be improved.

According to a twelfth aspect of the present invention, there is provided a film forming apparatus according to any one of the ninth to eleventh aspects of the present invention, wherein: Is 1 minute or more.

With this configuration, the concentration of impurities adhering to the film-forming substrate or the surface of the non-doped semiconductor thin film reaches saturation with the passage of time by leaving the inside of the chamber for 1 minute or more, and the concentration of the impurities adhering to the surface becomes higher. Can be stabilized. Therefore, the impurity concentration in the semiconductor thin film becomes more uniform in the batch, and the uniformity of film formation in the batch can be further improved.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for forming a semiconductor thin film according to the present invention will be described below with reference to FIG. (Embodiment 1) FIGS. 1A to 1F are process charts showing a method for forming a semiconductor thin film according to the present embodiment. In the method for forming a semiconductor thin film according to the present embodiment, a first evacuation step (FIG. 1A) of introducing a deposition substrate into a chamber and evacuating the chamber and stopping the evacuation of the chamber are performed. A step of introducing an impurity gas into the chamber (FIG. 1 (b)), and after the pressure in the chamber reaches a predetermined pressure, the introduction of the impurity gas is stopped and the inside of the chamber is kept under the predetermined pressure for a predetermined time. A leaving step (FIG. 1 (c)), a second evacuation step (FIG. 1 (d)) for exhausting the chamber, stopping the exhaust in the chamber, and introducing a film forming gas into the chamber. The method includes a film forming gas introducing step (FIG. 1E) and a step of ending the film formation of the silicon thin film (FIG. 1F).

The process of forming the semiconductor thin film according to the present embodiment having the above configuration will be described in detail. As shown in FIG. 1A, first, the deposition substrate 1 is introduced into an LPCVD chamber, and the chamber is evacuated by an exhaust unit until the pressure in the chamber becomes less than 1 mPa (base pressure). At this time,
The temperature in the chamber is maintained at 450 ° C.

Next, as shown in FIG. 1B, after the evacuation of the chamber is stopped, the impurity gas for doping 13 is introduced into the chamber from the impurity gas inlet 3 by the impurity gas introducing means. For example, the doping impurity gas 13 includes B ₂ H ₆ , PH _{3 and the} like.

Next, as shown in FIG. 1C, after the pressure in the chamber reaches 26.6 Pa by the leaving means, the impurity gas 1
Stop introducing 3. In this state, it is left for 1 minute in the chamber. The dispersion of the impurity gas is eliminated within the standing time, and the deposition of the impurity proceeds uniformly at all places in the chamber. At this time, as shown in FIG.
It can be seen that the concentration of impurities adhering to the surface saturates over time. Therefore, in order to stabilize the concentration of the adhering impurities, a standing time of 1 minute or more is preferable. Here, the leaving means means a means for stopping the introduction of gas into and out of the chamber and keeping the pressure in the chamber constant. For example, a valve that opens and closes the impurity gas inlet 3 can be used as the leaving means. By closing the impurity gas inlet 3 with the valve, the introduction of the impurity gas 13 from the impurity gas introducing means into the chamber can be stopped, and the pressure in the chamber can be kept constant.

Next, as shown in FIG. 1 (d), the inside of the chamber is evacuated to a base pressure by evacuation means.

Next, as shown in FIG. 1E, the evacuation of the chamber is stopped, and a silane-based gas 12 as a film-forming gas is introduced into the chamber from the silane-based gas inlet 2 by a film-forming gas introducing means. Introduce. For example, the silane-based gas 12 includes SiH ₄ , Si ₂ H _{6 and the} like.

Finally, as shown in FIG. 1F, the introduction of the silane-based gas 12 into the chamber is stopped, and the formation of the silicon thin film (a-Si thin film) is completed. By forming an a-Si thin film by the above method, it is possible to form an a-Si thin film having a uniform impurity concentration in the batch. Compared with the case where the silane-based gas and the impurity gas are simultaneously introduced into the LPCVD chamber as in the prior art, the variation in the impurities in the a-Si thin film after the film formation is reduced to 1/50 or less. That is,
The uniformity of film formation in a batch can be greatly improved. In addition, when a polycrystalline film is formed by ELA or SPC using an a-Si thin film formed by the method for forming a semiconductor thin film according to the present embodiment, the entire film is affected by variations in the thickness of the a-Si thin film. Even if a problem such as the occurrence of a portion that is not crystallized occurs, all impurities are always on the surface of the a-Si thin film, so that all impurities are always activated. As a result, the electrical characteristics of the a-Si thin film (poly-Si layer) after crystallization are less affected by variations in the crystallization process. Therefore, when applying to TFT etc.,
Device yield and reliability can be improved.

Next, another embodiment of the method for forming a semiconductor thin film according to the present invention will be described with reference to FIG. (Embodiment 2) FIGS. 3 (a) to 3 (f) are process diagrams showing a method for forming a semiconductor thin film according to the present embodiment. In the method for forming a semiconductor thin film according to the present embodiment, a first evacuation step (FIG. 3A) of introducing a deposition substrate into a chamber and evacuating the chamber and stopping the evacuation of the chamber are performed. , A second gas introducing step of introducing a film forming gas into the chamber (FIG. 3)
(b)), a second exhaust step of exhausting the chamber (FIG. 3 (c)), and a first gas introducing step of stopping the exhaust of the chamber and introducing the impurity gas into the chamber (FIG. 3 (d)), after the pressure in the chamber reaches a predetermined pressure, the introduction of the impurity gas is stopped, and the leaving step of leaving the inside of the chamber under the predetermined pressure for a predetermined time (FIG. 3 (e)); (FIG. 3F) for terminating the film formation.

The present invention can also be implemented by the method for forming a semiconductor thin film according to the present embodiment having the above configuration. That is, an effect similar to that of the method for forming a semiconductor thin film according to the first embodiment can be obtained by first forming a non-doped silicon thin film on a film formation substrate and then introducing an impurity gas into the chamber to form a silicon thin film. be able to.

[0038]

As described above, according to the present invention, a semiconductor thin film having a uniform impurity concentration in a semiconductor thin film in a batch can be formed. Compared with the conventional technique in which a silane-based gas and an impurity gas are simultaneously introduced into a chamber, the variation in impurities in a semiconductor thin film after film formation in a batch is 1/50 or less. That is, the uniformity of film formation in a batch can be significantly improved.

[Brief description of the drawings]

FIGS. 1A to 1F are process diagrams showing a method for forming a semiconductor thin film according to the present embodiment. FIG. 1A is a first evacuation process diagram for introducing a film formation substrate into a chamber and evacuating the chamber. FIG. 1B is an impurity gas introduction process diagram in which the evacuation of the chamber is stopped and the impurity gas is introduced into the chamber. FIG. 1C is a leaving process diagram in which after the pressure in the chamber reaches a predetermined pressure, the introduction of the impurity gas is stopped and the inside of the chamber is left under the predetermined pressure for a predetermined time. FIG. 1D is a second exhaust process diagram for exhausting the inside of the chamber. Fig. 1 (e) stops the exhaust in the chamber,
It is a film-forming-gas introduction process figure which introduces a film-forming gas in a chamber. FIG. 1F is a process chart for terminating the formation of the silicon thin film.

FIG. 2 is a diagram showing a relationship between a standing time and an impurity concentration.

FIGS. 3A to 3F are process diagrams showing a method for forming a semiconductor thin film according to the present embodiment. FIG. 3A is a first evacuation process diagram in which a film formation substrate is introduced into a chamber and the chamber is evacuated. FIG. 3B is a film forming gas introduction process diagram in which the evacuation of the chamber is stopped and a film forming gas is introduced into the chamber. FIG. 3C is a second evacuation process diagram for evacuating the chamber. FIG. 3D is an impurity gas introduction process diagram in which the evacuation of the chamber is stopped and the impurity gas is introduced into the chamber. FIG. 3E is a leaving process diagram in which the introduction of the impurity gas is stopped after the pressure in the chamber reaches a predetermined pressure, and the chamber is left under the predetermined pressure for a predetermined time. FIG. 3F is a process chart for terminating the formation of the silicon thin film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film-forming board 2 Silane-based gas inlet 3 Impurity gas inlet 12 Silane-based gas 13 Impurity gas

Claims (12)

[Claims] In a method for producing a semiconductor thin film containing a desired impurity on a film-forming substrate, the film-forming substrate is introduced into the chamber. A first exhaust step of exhausting the chamber later, and an impurity gas introducing step of introducing an impurity gas into the chamber after the first exhaust step;
A second exhaust step of exhausting the chamber into which the impurity gas has been introduced after the impurity gas introducing step, and a film forming gas introducing step of introducing a film forming gas into the chamber after the second exhaust step. A method for producing a semiconductor thin film, comprising: 2. A method for producing a semiconductor thin film containing a desired impurity on a film forming substrate by introducing the film forming substrate into a chamber of an LPCVD film forming apparatus, wherein the film forming substrate is introduced into the chamber. A first evacuation step of exhausting the interior of the chamber later, a deposition gas introduction step of introducing a deposition gas into the chamber after the first exhaustion step, and the deposition gas after the deposition gas introduction step. A second exhausting step of exhausting the chamber into which the gas has been introduced, and an impurity gas introducing step of introducing an impurity gas into the chamber after the second exhausting step. . 3. The method according to claim 1, further comprising the step of leaving the chamber into which the impurity gas has been introduced for a predetermined time immediately after the step of introducing the impurity gas.
3. The method for producing a semiconductor thin film according to item 1. 4. The method according to claim 1, further comprising a leaving step in which the chamber into which the impurity gas has been introduced is left under a predetermined pressure for a predetermined time immediately after the impurity gas introducing step. How to make a semiconductor thin film. 5. The method according to claim 1, further comprising a leaving step in which the chamber into which the impurity gas has been introduced is left under a pressure of 1 Pa or more and 100 Pa or less for a predetermined time immediately after the introducing step of the impurity gas. 3. The method for producing a semiconductor thin film according to item 2. 6. The method according to claim 3, wherein the predetermined time is one minute or more. 7. An LPCVD deposition chamber into which a deposition substrate is introduced, and an exhaust unit that exhausts the chamber.
In a film forming apparatus having a film forming gas introducing unit for introducing a film forming gas into the chamber and an impurity gas introducing unit for introducing an impurity gas into the chamber, after a film forming substrate is introduced into the chamber, The evacuation unit performs a first evacuation of the chamber, and after the first evacuation of the chamber, the impurity gas introducing unit introduces an impurity gas into the chamber, and the impurity gas is introduced into the chamber. After the gas is introduced, the exhaust means exhausts the second gas in the chamber, and exhausts the second gas in the chamber.
The film forming gas introducing means introduces a film forming gas into the chamber after the gas is exhausted. 8. An LPCVD deposition chamber into which a deposition substrate is introduced, and an exhaust unit that exhausts the chamber.
In a film forming apparatus having a film forming gas introducing unit for introducing a film forming gas into the chamber and an impurity gas introducing unit for introducing an impurity gas into the chamber, after a film forming substrate is introduced into the chamber, The evacuation unit performs a first evacuation in the chamber, and after the first evacuation in the chamber, the film formation gas introduction unit introduces a film formation gas into the chamber, and the film formation gas is introduced into the chamber. After the film-forming gas is introduced, the evacuation unit performs a second evacuation of the chamber, and after the second evacuation of the chamber, the impurity gas introduction unit introduces an impurity gas into the chamber. A film forming apparatus characterized by the above-mentioned. 9. The apparatus according to claim 7, further comprising a leaving unit for leaving the inside of the chamber into which the impurity gas has been introduced for a predetermined time immediately after the introduction of the impurity gas into the chamber. Film forming equipment. 10. The apparatus according to claim 7, further comprising a leaving unit for leaving the inside of the chamber into which the impurity gas has been introduced for a predetermined time under a predetermined pressure immediately after the introduction of the impurity gas into the chamber. A film forming apparatus according to claim 8. 11. Immediately after the impurity gas is introduced into the chamber, there is provided a leaving means for leaving the inside of the chamber into which the impurity gas is introduced under a pressure of 1 Pa or more and 100 Pa or less for a predetermined time. A film forming apparatus according to claim 7. 12. The film forming apparatus according to claim 9, wherein the predetermined time is one minute or more.