METHOD AND APPARATUS FOR DEPOSITING AMORPHOUS SILICON FILM

Abstract

Provided is a method and apparatus for depositing an amorphous silicon film. The method includes supplying a source gas and an atmospheric gas onto a substrate in a state where the substrate is loaded in a chamber to deposit the amorphous silicon film on the substrate. The atmospheric gas includes at least one of hydrogen and helium. The source gas includes at least one of silane (SiH.sub.2), disilane (Si.sub.2H.sub.6), and dichlorosilane (SiCl.sub.2H.sub.2).

Claims

1. A method for depositing an amorphous silicon film, the method comprising: supplying a source gas and an atmospheric gas onto a substrate in a state where the substrate is loaded in a chamber; and depositing the amorphous silicon film on the substrate at a process temperature under a process pressure, wherein the source gas comprises at least one of silane (SiH.sub.2), disilane (Si.sub.2H.sub.6), and dichlorosilane (SiCl.sub.2H.sub.2), wherein the process temperature is adjusted to be in a range of about 540 C. to about 580 C. and the process pressure is adjusted to be in a range of about 8 Torr to about 300 Torr, so that the source gas is pyrolyzed to deposit the amorphous silicon film on the substrate, and wherein the atmospheric gas comprises at least one of hydrogen and helium.

2. The method of claim 1, wherein the source gas has a flow rate of about 0.5 sccm to about 300 sccm, and the atmospheric gas has a flow rate of about 100 sccm to about 25000 sccm.

3. The method of claim 1, wherein the amorphous silicon film is deposited to have a thickness of about 1000 or more.

4. The method of claim 3, wherein the amorphous silicon film is deposited to have a surface roughness of about 1 nm or less.

5. The method of claim 1, wherein the substrate is placed on a heater, and the substrate is heated by the heater to the process temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain principles of the present invention. In the drawings:

[0015] FIG. 1 is a schematic view of an apparatus for depositing an amorphous silicon film according to an embodiment of the present invention;

[0016] FIG. 2 is a graph illustrating a variation in surface roughness according to a temperature when the amorphous silicon film is deposited using a nitrogen gas as an atmospheric gas;

[0017] FIG. 3 is a graph illustrating a variation in surface roughness according to a temperature when the amorphous silicon film is deposited using a helium gas as an atmospheric gas;

[0018] FIG. 4 is a graph illustrating results obtained by comparing deposition rates of the amorphous silicon films according to a deposition temperature when the nitrogen gas and the helium gas are used as the atmospheric gas; and

[0019] FIG. 5 is a graph illustrating surface roughness of the amorphous film according to the atmospheric gases.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0020] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 1 to 5. The present invention may, however, be embodied in different forms and should not be constructed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, the shapes of components are exaggerated for clarity of illustration.

[0021] Hereinafter, the term amorphous silicon does not merely represent only the amorphous silicon. For example, the amorphous silicon includes amorphous silicon, nano-crystalline silicon formed by combining crystal grains each of which has an amorphous nano size to achieve precision in surface roughness that will be described below, and silicon in which the amorphous silicon is mixed with the nano-crystalline silicon.

[0022] FIG. 1 is a schematic view of an apparatus for depositing an amorphous silicon film according to an embodiment of the present invention. In general, chemical vapor deposition is a process in which a gaseous source gas is supplied onto a semiconductor substrate to induce chemical reaction with the substrate, thereby forming a thin film on the substrate.

[0023] Referring to FIG. 1, a chamber 11 provides an inner space sealed from the outside. An introduction unit 12 for introducing a source gas into the inner space is provided in an upper portion of the chamber 11. A main supply line 12a and first and second supply lines 18a and 19a connected to the main supply line 12a may be connected to the introduction unit 12. The source gas may be supplied into the chamber 11 through the first supply line 18a, and an atmospheric gas may be supplied into the chamber 11 through the second supply line 19a. The source gas may be a silane-based gas such as silane (SiH.sub.2), disilane (Si.sub.2H.sub.6), and dichlorosilane (SiCl.sub.2H.sub.2, DCS). The atmospheric gas may be at least one of hydrogen (H) and helium (He). The source gas may be stored in a first storage tank 18d connected to the first supply line 18a, and the atmospheric gas may be stored in a second storage tank 19d connected to the second supply line 19a.

[0024] Also, a first flow controller 18b and a first valve 18c are disposed in the first supply line 18a, and a second flow controller 19b and a second valve 19c are disposed in the second supply line 19a. Here, the gas introduced through the introduction unit 12 may be injected into the chamber 11 through a showerhead 13 disposed in the chamber 11.

[0025] Also, a wafer 15 that is a target object to be deposited may be placed on a heater 14. The heater 14 may heat the wafer 15 to a process temperature in a state where the heater 14 is supported by a heater support 16. When the deposition is completed, a non-reaction gas and by-products within the chamber 11 may be exhausted through a vacuum port 17. An exhaust line 17a and a vacuum pump 17b may be connected to the vacuum port 17 to forcibly exhaust the non-reaction gas and the by-products within the chamber 11. Also, a process pressure within the chamber 11 may be adjusted by using the exhaust line 17a and the vacuum pump 17b.

[0026] According to the above-described method, the source gas and the atmospheric gas may be supplied onto the wafer 15 within the chamber 11. Then, an amorphous silicon film may be deposited on the wafer 15 using a source gas pyrolyzed by the heater 14. Here, a control unit 20 may control the heater 14 for adjusting the process temperature, the vacuum pump 17b for adjusting the process pressure, and the first and second flow controllers 18b and 19b for respectively adjusting supply flow rates of the source gas and the atmospheric gas. The controller 20 may adjust the process temperature in the chamber 11 to a temperature of about 200 C. to about 800 C. and the process pressure in the chamber 11 to a pressure of about 1 Torr to about 200 Torr. Also, the control unit 20 may adjust the supply flow rate of the source gas to a flow rate of about 0.5 sccm to about 300 sccm and the supply flow rate of the atmospheric gas to a flow rate of about 100 sccm to about 25,000 sccm.

[0027] As described above, the wafer 15 may be loaded into the chamber 11, and then the source gas and the atmospheric gas may be supplied onto the wafer 15 at nearly the same time to deposit the amorphous silicon film on the wafer 15. The source gas may be a silane-based gas such as a silane (SiH.sub.2), disilane (Si.sub.2H.sub.6), and dichlorosilane (SiCl.sub.2H.sub.2, DCS). Also, the wafer 15 may be loaded into the chamber 11 in a state where a seed layer is formed on a top surface of the wafer 15. Here, the amorphous silicon film may be formed on the seed layer.

[0028] FIG. 2 is a graph illustrating a variation in surface roughness according to a temperature when the amorphous silicon film is deposited using a nitrogen gas as an atmospheric gas. That is, FIG. 2 shows surface roughness of each of the amorphous silicon films when an amorphous silicon film is deposited to a thickness of about 1000 at temperatures of about 530 C. and about 540 C. , and when an amorphous silicon film is deposited to a thickness of about 7500 at temperatures of about 550 C. and about 570 C. (process pressure: 2 Torr, and the source gas is disilane (Si.sub.2H.sub.6)). FIG. 3 is a graph illustrating a variation in surface roughness according to a temperature when the amorphous silicon film is deposited using a helium gas as an atmospheric gas. That is, FIG. 3 shows surface roughness of each of the amorphous silicon films when an amorphous silicon film is deposited to a thickness of about 1000 at temperatures of about 530 C. and about 540 C. , and when an amorphous silicon film is deposited to a thickness of about 7500 at temperatures of about 550 C. and about 570 C.

[0029] Referring to FIG. 2, it was seen that, if a nitrogen gas is used as the atmospheric gas, when the amorphous silicon film has a thickness of about 1,000 , the amorphous silicon film has surface roughness of about 1 nm or less, however, when the amorphous silicon film has a thickness of about 7500 , the amorphous silicon film has surface roughness of about 2 nm or more. That is, as the amorphous silicon film increases in thickness, the surface roughness thereof may rapidly increase. On the other hand, referring to FIG. 3, it was seen that, if a helium gas is used as the atmospheric gas, when the amorphous silicon film has a thickness of about 1000 , the amorphous silicon film has surface roughness of about 1 nm or less, and, when the amorphous silicon film has a thickness of about 7500 , the amorphous silicon film has surface roughness of about 1 nm or less. That is, in spite of that the amorphous silicon film increases in thickness, the surface roughness thereof may be maintained at the same level.

[0030] In general, in a batch type deposition apparatus, the thin film has an improved surface roughness when compared to that in a single type deposition apparatus illustrated in FIG. 1.

[0031] Here, the surface roughness gradually increases as a thin film increases in thickness. However, as illustrated in FIG. 3, when the helium gas is used as the atmospheric gas, the amorphous silicon film has the same surface roughness regardless of the thickness of the thin film. In particular, when the amorphous silicon film has a thickness of about 7500 , the surface roughness of the amorphous silicon film may be the same level as that of the amorphous silicon film in the batch type deposition apparatus.

[0032] FIG. 4 is a graph illustrating results obtained by comparing deposition rates of the amorphous silicon films according to a deposition temperature when the nitrogen gas and the helium gas are used as the atmospheric gas. Referring to FIG. 4, it was seen that, when a deposition temperature is about 530 C., a deposition rate is about 11.07 (the atmospheric gas: the nitrogen gas) which is little different from that of about 11.19 (the atmospheric gas: the helium gas). However, as the deposition temperature increases, a difference between the deposition rates gradually increases. When the deposition temperature is about 570 C. , the deposition rate is about 26.48 (the atmospheric gas: the nitrogen gas) which is different by about 30% or more from the deposition rate of about 35.51 (the atmospheric gas: the helium gas).

[0033] Resultantly, if the helium gas is used as the atmospheric gas, when the thin film increases in thickness (for example, a thickness of about 7500 ), the increase of the surface roughness may be prevented. Also, the amorphous silicon film in the single type deposition apparatus may have the same surface roughness as that in the batch type deposition apparatus. In particular, the deposition rate at a high temperature (for example, a temperature of about 540 C. or more) may be significantly improved.

[0034] FIG. 5 is a graph illustrating surface roughness of the amorphous film according to the atmospheric gases. An amorphous silicon film was deposited under conditions shown in following Table 1 by using nitrogen (N), argon (Ar), helium (He), and hydrogen (H) as an atmospheric gas and using disilane (Si.sub.2H.sub.6) as a source gas.

TABLE-US-00001 TABLE 1 Atmospheric Process Disilane Atmospheric Deposition Thickness gas temperature ( C.) (sccm) gas (sccm) Pressure rate (/sec) () Nitrogen (N) 530 30 20000 30 0.7 50 Argon (Ar) 18000 0.79 Helium (He) 12000 0.72 Hydrogen (H) 8000 0.76

[0035] As a result, it was seen that, when helium (He) is supplied, the surface roughness of the amorphous silicon film was improved in comparison to that of the amorphous silicon film when nitrogen (N) and argon (Ar) are supplied. That is, when each of nitrogen (N) and argon (Ar) are supplied onto the amorphous silicon film, a surface roughness of the amorphous silicon film is greater than about 0.3 nm. However, when helium (He) is supplied, a surface roughness of the amorphous silicon film is less than about 0.3 nm. That is, it was seen that, when helium (He) is supplied, the amorphous silicon film has surface roughness improved by about 15% or more. Also, when hydrogen (H) is supplied, a surface roughness of the amorphous silicon film was improved in comparison to that when helium (He) is supplied. Also, when hydrogen (H) is supplied, the amorphous silicon film has a deposition rate of about 0.76 /sec which is greater than that of about 0.72 /sec when helium (He) is supplied.

[0036] The above-described amorphous silicon film is useful to fill a contact hole defined in an interlayer dielectric such as a silicon oxide film or a silicon nitride film or to fill a line defined in the interlayer dielectric, e.g., a groove for an inner wire. Particularly, if the amorphous silicon film has great surface roughness, a large void may be generated when the contact hole is filled with the amorphous silicon film. On the other hand, if the amorphous silicon film has low surface roughness, a small void may be generated to prevent a resistance of the amorphous silicon film filled in the contact hole from increasing.

[0037] According to the embodiments of the present invention, the surface roughness may be more improved in precision. Also, the method and apparatus according to the present invention may respond to the miniaturization of the contact hole or line.

[0038] Although the present invention is described in detail with reference to the exemplary embodiments, the invention may be embodied in many different forms. Thus, technical idea and scope of claims set forth below are not limited to the preferred embodiments.

[0039] The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.