Patent Application
20060254516
1. Field of the Invention
The present invention relates to a heating element CVD system and a heating element CVD method for depositing a thin film on a substrate disposed in a vacuum chamber (processing chamber) by providing a heating element which is maintained at a predetermined temperature in the vacuum chamber, and decomposing and/or activating a material gas by using the heating element.
2. Description of the Related Art
In the production of various kinds of semiconductor devices such as an LSI (large scale integrated circuit), LCDs (liquid crystal displays), solar cells, or the like, the chemical vapor deposition (CVD) method is widely used as a process for forming a predetermined thin film on a substrate.
As the CVD method, in addition to a plasma CVD method for forming a film by decomposing and/or activating a material gas in a discharge plasma, a thermal CVD method for forming a film by heating a substrate for generating the chemical reaction by the heat, or the like, and a CVD method for forming a film by decomposing and/or activating a material gas by a heating element which is maintained at a predetermined high temperature (hereinafter referred to as the “heating element CVD method”) can be presented. A film formation processing system for executing the heating element CVD method (heating element CVD system) is provided in a configuration of introducing a material gas while maintaining a heating element which is made of a high melting point metal such as a tungsten at a high temperature of about 1,000 to 2,000° C. in a processing chamber that is capable of evacuating to the vacuum. The introduced material gas is decomposed or activated at the time of passing by the surface of the heating element. By having the material gas reach a substrate, a thin film of a finally targeted substance (such as a silicon film) is deposited on the substrate surface.
Among the heating element CVD methods, those using a wire-like heating element are referred to as a hot wire CVD method. Moreover, among the heating element CVD methods, those utilizing the catalytic-CVD reaction of a heating element in the decomposition or activation of the material gas by the heating element are referred to as a catalytic-CVD (Cat-CVD) method.
According to the heating element CVD method, since the decomposition or activation of the material gas is generated at the time of passing by the heating element, as compared with the thermal CVD method of generating the reaction only by the heat of the substrate, it is advantageous in that the substrate temperature can be made lower. Moreover, unlike the plasma CVD method, since the plasma is not formed, a problem of damage on/to the substrate by the plasma can be eliminated. From these viewpoints, the heating element CVD method is regarded as a promising film forming method for the next generation devices or the like having a larger scale integration and higher function.
However, although the heating element CVD method is highly useful, it has not achieved the stable formation of a high quality polycrystalline silicon film with a good reproductivity. Here, the high quality polycrystalline silicon film refers to those having, for example, an electron mobility which has improved to 20 cm2/Vs as the electronic devices. In general, in the case a silicon film is formed by using a conventional heating element CVD system, although a polycrystalline state can be realized, the degree of crystallization in the stage after the film formation is not good, and a film quality that is close to the amorphous state is provided. That is, the as-deposited polycrystalline silicon film which is formed by a conventional heating element CVD method has not attained the quality that is required for the electronic devices in the industry.
Therefore, the present inventors have studied elaborately, paying attention to, in particular, the importance of the film formation environment at the time of the silicon film formation in the processing chamber, the importance of maintenance and stabilization of the atomic hydrogen for establishing the apparatus configuration and the film forming method which is capable of maintaining the film forming environment that are not present in the prior art.
That is, the present inventors concluded that in a silicon film formation, it is indispensable for the high quality polycrystalline silicon film formation to create the environment where the deactivation of an atomic hydrogen which is produced in the decomposition process and/or activation process of silane (SiH4) or hydrogen (H2) can be restrained, and as a result, the atomic hydrogen can exist stably in the processing chamber. The present inventors aimed at putting these conclusions into practice in the heating element CVD system and the heating element CVD method of the present invention.
A silicon film is formed on a substrate by decomposing and/or activating silane (SiH4) or hydrogen (H2) as the material gas by a heating element. At the same time, a silicon film is formed on the inner wall of a processing chamber. The atomic hydrogen which is produced in the decomposition process and/or activation process of the silane (SiH4) or hydrogen (H2) produces a secondary product by the reaction with the adhered film that is deposited on the inner wall of processing chamber, which influences the quality of the silicon film that is formed on the substrate so as to disturb the production of a high quality silicon film. This phenomenon is also learned.
This phenomenon is reported by Atsushi Masuda, et al. in the preliminary reports for the lectures for the 48th applied physics related association assembly 2001 29a-ZQ-3, p. 949.
In view of the above-mentioned conventional heating element CVD system and heating element CVD method, an object of the present invention is to provide a heating element CVD system and a heating element CVD method which are capable of forming a high quality polycrystalline silicon film (polysilicon film) as a device, in the case of producing a silicon film by using a heating element CVD system.
Similar to the conventional heating element CVD system, a heating element CVD system which is proposed by the present invention comprises a processing chamber (vacuum chamber) for applying a predetermined process to a substrate that is held by a substrate holder which is provided inside the processing chamber, an evacuating system that is connected with the processing chamber for evacuating the inside of the processing chamber to the vacuum, a material gas supplying system for supplying a predetermined material gas into the processing chamber, and a heating element which is disposed in the processing chamber for receiving the electric power supply from an electric power supplying mechanism so as to be at a high temperature. Then, a thin film is formed on the substrate that is held by the substrate holder by the decomposition and/or the activation of the material gas that is introduced from the material gas supplying system into the processing chamber by the heating element which is maintained at a high temperature.
According to the heating element CVD system of the above-mentioned configuration, in the heating element CVD system which is proposed by the present invention, the inner surface of a structure surrounding the space between the substrate holder and the heating element is heated during the formation of the thin film on the substrate.
According to the heating element CVD system of the present invention, since the inner surface of the structure surrounding the space between the substrate holder and the heating element is heated during the formation of the thin film, such as a silicon film, on the substrate, the atomic hydrogen can exist stably in the space between the substrate holder and the heating element, and the specific environment can be obtained under which the secondary product, which is generated at the same time when the silicon film is formed, can be reduced. Thereby, a high quality polycrystalline silicon film can be formed.
In the above-mentioned heating element CVD system of the present invention, the above-described predetermined process denotes, for example, the thin film formation on the substrate which is disposed in the processing chamber, cleaning for eliminating the adhered substance on the inside of the processing chamber, or the like. Moreover, the predetermined material gas can be determined variously depending on the thin film that is to be formed. For example, in the case of forming a silicon film, a gas mixture of silane (SiH4) and hydrogen (H2) is used as the predetermined material gas. Further, in the case of forming a silicon carbide film, a gas mixture of silane (SiH4), hydrogen (H2) and at least one selected from the group consisting of methane (CH4), acetylene (C2H2) and ethane (C2H6) is used as the predetermined gas. Also, in the case of forming a silicon germanium film, a gas mixture of silane (SiH4), germane (GeH4) and hydrogen (H2) is used as the predetermined gas. Furthermore, the high temperature at which the heated heating element maintains is about 1,600 to 2,000° C. at the time of the film formation, and is about 2,000 to 2,500° C. at the time of cleaning (at the time of eliminating the substance that is adhered on the insdie of the processing chamber).
In the above-described heating element CVD system of the present invention, as the structure surrounding the space between the substrate holder and the heating element, any structure may be adopted so long as it is a structure which is provided with a heating mechanism in itself, such as a jig which is provided with a heating mechanism in itself and which surrounds the space between the substrate holder and the heating element in consideration of the efficiency of the electric power.
Therefore, a heating jig which is disposed so as to surround the space between the substrate holder and the heating element inside of the inner wall of the processing chamber and a heating of the inner surface of the heating jig is carried out by a heating mechanism stored therein can be adopted as the structure surrounding the space between the substrate holder and the heating element.
Moreover, it is also possible to use the inner wall of the processing chamber as the structure surrounding the space between the substrate holder and the heating element. In this case, the heating of the inner surface of the structure (the inner wall of the processing chamber) is carried out by a heating mechanism which is stored in the inner wall of the processing chamber.
The heating mechanism may be composed of for example, a heater, a temperature detection sensor, a heating temperature adjusting device for adjusting the input electric power to the heater based on a signal from the temperature detection sensor, or the like.
Furthermore, in the above-described heating element CVD system of the present invention, the heating is carried out so as to have the inner surface of the structure heated and maintained at least at 200° C. or higher, preferably 350° C. or higher.
It is preferable to maintain the temperature of the inner surface of the structure at least at 350° C. or higher in a pressure range in which the heating element CVD system is used ordinarily, such as a several tens Pa area. In the several tens Pa pressure area, by surrounding the space between the substrate holder and the heating element by the inner surface of the structure being maintained at least at 350° C. or higher, during the formation of the silicon film on the substrate, the atomic hydrogen can exist stably in the space between the substrate holder and the heating element, and the specific environment can be obtained under which the secondary product, which is generated at the same time during the formation of the silicon film, can be reduced.
In the case where the heating element CVD system is used in a slightly low pressure range, such as a several Pa area, by maintaining the temperature of the inner surface of the structure at least at 200° C. or higher, during the formation of the silicon film on the substrate, the atomic hydrogen can exist stably in the space between the substrate holder and the heating element, and the specific environment can be obtained under which the secondary product, which is generated at the same time during the formation of the silicon film, can be reduced. Therefore, in the case where the heating element CVD system is used in a slightly low pressure range, such as several Pa, it is sufficient to maintain the temperature of the inner surface of the structure at least at 200° C. or higher.
The upper limit of the temperature of the inner surface of the structure surrounding the space between the substrate holder and the heating element is not particularly limited so long as it is in a temperature range which does not cause thermal damage on the substrate with the thin film formed.
Next, in order to achieve the above-mentioned object, a heating element CVD method which is proposed by the present invention is carried out by using the above-mentioned heating element CVD system of the present invention, wherein the thin film formed on the substrate is any one of a silicon film, a silicon carbide film, or a silicon germanium film, etc., and the inner surface of the structure surrounding the space between the substrate holder and the heating element is heated and maintained at least at 200° C. or higher, preferably 350° C. or higher during the formation of the aforementioned silicon films for the above-mentioned reason.
According to the heating element CVD system and the heating element CVD method of the present invention, by forming a silicon film, a silicon carbide film, or a silicon germanium film, etc., by heating the inner surface of the structure surrounding the space between the substrate holder and the heating element and maintaining the temperature of the inner surface at least at 200° C. or higher, preferably at least at 350° C. or higher, a high quality polycrystalline silicon film having a good device characteristic can be formed.
Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be explained. However, the configuration, the shape and the arrangement relationships of the present invention are shown schematically in the drawings to the degree that the present invention can be understood, and furthermore, the numerical values and the compositions (materials) of the configurations are merely examples. Therefore, the present invention is not limited to the embodiments explained below, and the present invention can be modified in various forms within the technological scope of the appended claims.
The heating element CVD system shown in
Moreover, the substrate 9 and the substrate holder 5 are contacted closely by an unshown electrostatic chucking mechanism. At the time of forming a silicon film, the substrate 9 is heated at 300 to 350° C.
As shown in
The processing chamber 1 is an airtight vacuum chamber, providing an unshown gate valve for placing or removing the substrate 9.
The processing chamber 1 provides an evacuating opening 11 such that the inside of the processing chamber 1 can be evacuated through the evacuating opening 11.
The evacuating system 2 provides a vacuum pump 21 such as a turbo molecular pump. The evacuating system 2 connected with the evacuating opening 11 of the processing chamber 1 is provided so as to evacuate the inside of the processing chamber 1 to about 10−5 to 10−7 Pa. The evacuating system 2 provides an evacuation speed adjusting device 22 such as a variable orifice.
The gas supplying system 3 is composed of a first gas bomb 31a for storing silane (SiH4) as the material gas, a second gas bomb 31b for storing hydrogen (H2) to be mixed with the silane (SiH4), a pipe 33 for connecting the first and second gas bombs 31a, 31b and the material gas supplying device 32, at least one valve 34 and flow rate adjusting devices 35, 36 which are provided on the pipe 33.
That is, the silane (SiH4) and the hydrogen (H2) from the first and second gas bombs 31a, 31b are mixed halfway in the pipe 33 and become the material gas so as to be introduced into the material gas supplying device 32. The material gas is blown from a gas blowing hole 320 of the material gas supplying device 32 toward the heating element 4 so as to be supplied into the processing chamber 1.
The heating element 4 is made of a high melting point metal, such as tungsten, molybdenum, and tantalum. Moreover, the electric power supplying system 6 is composed so as to energize the heating element 4 for generating the Joule's heat in the heating element 4. That is, the electric power supplying mechanism 6 is composed so as to maintain the heating element 4 at a predetermined high temperature, for example at about 1,600° C. to 2,500° C., by supplying electric power.
In
As shown in
Accordingly, as shown in
Since the construction is adopted in which the connecting terminals 321 and the interlocking plate 323 are not contacted with the material gas, there is no risk of corrosion, deterioration, or the like.
Since the heating element 4 is fixed on the connecting terminals 321 which are fixed on the inside of the material gas supplying device 32 by a pressuring spring (not shown) or the like, the heating element 4 can be detached easily. Moreover, the distance between the substrate 9 and the heating element 4 can be adjusted and/or the distance between the heating elements 4 which are mounted on the material gas supplying device 32 can be adjusted according to the size of the substrate 9 that is held by the substrate holder 5, the process condition, or the like.
In
This embodiment is advantageous for effectively heating the space between the substrate holder 5 and the heating element 4.
The method for fixing the processing chamber 1 and the heating jig 8 is not limited to the embodiment of being fixed on the upper surface of the processing chamber 1 (shown in
In
Moreover, in
The embodiment of the heating element CVD system of the present invention is not limited to that described above.
For example, although it is not shown, an alternative embodiment can be adopted in which the structure surrounding the space between the substrate holder 5 and the heating element 4 is the inner wall of the processing chamber 1 such that a heating of the inner surface of the structure is carried out by a heating mechanism which is stored in the inner wall of the processing chamber 1, where, as a result, the inner wall of the processing chamber 1 can be heated and maintained at least 200° C. or higher, preferably at least 350° C. or higher.
Next, the operation of the system of an embodiment shown in FIGS. 1 to 3(b) will be explained together with the explanation for the CVD method of the present invention.
The inside of the preliminary vacuum chamber (not shown) and the processing chamber 1 is evacuated to a predetermined pressure with the substrate 9 disposed in a preliminary vacuum chamber. With a gate valve (not shown) opened, the substrate 9 is conveyed into the processing chamber 1 by an unshown conveying mechanism. According to an unshown driving system, the substrate holder 5 is moved vertically so that the substrate 9 is placed and held on the substrate holder 5.
At that time, the substrate holder 5 is maintained at a predetermined temperature (for example, 300 to 350° C.), and the substrate 9 and the substrate holder 5 are contacted closely by the electrostatic chuck (not shown).
Next, the electric power supplying mechanism 6 starts to energize the heating element 4 so as to maintain the heating element 4 at a predetermined high temperature. Moreover, the heater 13 which is stored in the heating jig 8 is energized so as to operate the heating temperature adjusting device 15 for heating the heater 13 to a predetermined temperature, for example 350° C. In the case where the heating element 4 is maintained at a predetermined temperature, and the inner surface temperature of the heating jig 8 is confirmed to have reached at 350° C. by the sensor 14, the gas supplying system 3 is operated so that the material gas, that is, a silane gas mixed with a hydrogen gas, is introduced into the processing chamber 1 while adjusting the flow rate thereof by the flow rate adjusting device 35. Thereafter, the inside of the processing chamber 1 is maintained at a predetermined pressure by the evacuating system 2.
The electric power supply amount of the heater 13 is adjusted such that the inner surface of the heating jig 8 is maintained at least at 350° C. or higher in the case where the heating element CVD system of the present invention is used in a several tens Pa pressure area, and the inner surface of the heating jig 8 is heated and maintained at least at 200° C. or higher in the case where the heating element CVD system of the present invention is used in a relatively low pressure range, for example, of a several Pa pressure area.
Since it takes a long time for heating to 350° C. or higher, the production efficiency can be improved by adjusting the temperature to 200° C. or higher even in the case where the formation of the film is not executed for shortening the heating time to 350° C. or higher.
As a result, the material gas which is decomposed and/or activated on the surface of the heating element 4 can efficiently reach the surface of the substrate 9 so that a polycrystalline silicon film can be deposited on the surface of the substrate 9.
After the passage of a period of time which is needed for having the thin film thickness reach at a predetermined thickness, the valve 34 of the gas supplying system 3 is closed and the operation of the electric power supplying mechanism 6 is stopped. As needed, the electric power supply to the heating element 4 and the heater 13 may be blocked.
After operating the evacuating system 2 so as to evacuate the inside of the processing chamber 1 again to the predetermined pressure, the unshown gate valve is opened for taking out the substrate 9 from the processing chamber 1 by the unshown conveying mechanism. Thereby, a series of the film forming process can be finished.
An example of the film forming condition for forming a silicon film (film thickness: 1,000 nm) by a CVD method of the present invention using a heating element CVD system of the present invention will be shown below. In this example, a heating jig 8 surrounding the space between the substrate holder 5 and the heating element 4 on the inner side of the processing chamber 1 as in the embodiment shown in
In contrast, a silicon film (film thickness: 1,000 nm) was formed in the same condition except that the heating operation by the heating jig 8 was not carried out, using the same heating element CVD system, and it was provided as a comparative example.
The electron mobility was measured for both of the silicon films (film thickness: 1,000 nm).
As a result, it was confirmed that the electron mobility of the silicon film of the comparative example was at most 1 cm2/Vs, which is substantially the same as an amorphous film, but the electron mobility was improved according to the silicon film which was formed with the inner surface of the heating jig 8 being maintained at 350° C. by using the system and the method of the present invention.
The other heating element CVD system of the present invention is used, in which the inner wall of the processing chamber 1 is used as the structure surrounding the space between the substrate holder 5 and the heating element 4. A silicon film (film thickness: 1,000 nm) was formed in the same condition as described above by using this heating element CVD system with the inner surface of the wall of processing chamber 1 being maintained at 350° C. The electron mobility was measured for this silicon film. It was also confirmed that the electron mobility of this silicon film was improved.
Although preferred embodiments in the polycrystalline silicon film formation have been described in the above-mentioned examples, the configuration of the heating element CVD system and the heating element CVD method disclosed in the present invention are essential in stably forming a high quality thin film. Therefore, the heating element CVD system and the heating element CVD method using the same of the present invention can be adopted for the formation of the kinds of films with the atomic hydrogen that is produced during the film formation, such as a silicon carbide film which is obtained by using the material gas comprising at least one selected from the group consisting of methane (CH4), acetylene (C2H2) and ethane (C2H6), and at least one selected from the group consisting of silane (SiH4) and hydrogen (H2), and a silicon germanium film which is obtained by using the material gas comprising silane (SiH4), germane (GeH4) and hydrogen (H2), or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2001-349075 | Nov 2001 | JP | national |
This application is a continuation of U.S. application Ser. No. 10/293,698, filed Nov. 14, 2002.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10293698 | Nov 2002 | US |
| Child | 11489522 | Jul 2006 | US |
