Carbon doping method for thin films on wafers

Abstract

The present invention provides a method for doping a thin film of a wafer with carbon, the method including the steps of: placing a wafer having a thin film formed thereon in a process chamber; supplying an ambient gas into the process chamber so that the pressure of the process chamber reaches a process pressure higher than atmospheric pressure; heating the process chamber so that the temperature of the process chamber reaches a process temperature; and supplying a source gas containing carbon into the process chamber so that the source gas chemically reacts with the thin film at the process pressure and the process temperature, thereby doping the carbon into the thin film.

Description

[Technical Field]

[0001] The present invention relates to a method for doping thin films of wafers with carbon during semiconductor fabrication. [Background technology]

[0002] Generally, semiconductor manufacturing processes are divided into front-end and back-end processes, which include oxidation, deposition, exposure, etching, ion implantation, and wiring.

[0003] The deposition process is a process of depositing a very thin layer of a desired material on the surface of a wafer. Specific deposition methods include chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD). Chemical vapor deposition forms thin films through chemical reactions, while physical vapor deposition forms thin films using physical methods. Atomic layer deposition forms very thin films by stacking atomic layers. This method, along with chemical vapor deposition, has shown excellent step coverage.

[0004] Carbon is sometimes added to the deposition process to improve the properties of the thin film. To do this, carbon gas is co-injected into the vacuum chamber along with the gas used to form the thin film, reacting with the wafer. While adding carbon in this way improves other properties of the thin film, it can cause poor step coverage, a problem that cannot be solved even with atomic layer deposition. Poor step coverage is a major drawback in semiconductor designs with large aspect ratios. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide a method for carbon doping a thin film of a wafer that allows carbon to be implanted into the thin film of the wafer, but does not thereby degrade the step coverage of the thin film. [Means for solving the problem]

[0006] To achieve the above object, according to one aspect of the present invention, a method for doping carbon into a thin film on a wafer may include the steps of placing the wafer on which a thin film is formed in a process chamber; supplying an ambient gas into the process chamber so that the pressure in the process chamber reaches a process pressure higher than atmospheric pressure; heating the process chamber so that the temperature of the process chamber reaches a process temperature; and supplying a source gas containing carbon into the process chamber so that the source gas chemically reacts with the thin film at the process pressure and the process temperature, thereby doping the carbon into the thin film.

[0007] Here, the thin film may include any one of a silicon oxide film, a silicon nitride film, and a silicon nitride oxide film.

[0008] Here, the process pressure may be higher than 2 ATM.

[0009] Here, the process pressure may be determined within a range of 5 ATM to 20 ATM.

[0010] Here, the process temperature may be a temperature lower than the thermal decomposition temperature of the source gas.

[0011] Here, the process temperature may be determined within the range of 400°C to 600°C.

[0012] Here, the source gas may include one of ethylene gas and propylene gas.

[0013] Here, the atmospheric gas may include any one of H2, D2, N2, and Ar gas.

[0014] According to another aspect of the present invention, a method for doping carbon into a thin film on a wafer may include placing the wafer having a thin film formed thereon in a process chamber; supplying a source gas containing carbon into the process chamber; causing the source gas to chemically react with the thin film in a molecular state so that the carbon is chemically absorbed into the thin film; and causing the carbon to penetrate into the thin film by a pressure generated by a process pressure.

[0015] Here, the step of chemically reacting the source gas with the thin film in a molecular state to chemically absorb the carbon into the thin film may include maintaining a temperature of the process chamber below a temperature at which the source gas is thermally decomposed.

[0016] Here, the step of chemically reacting the source gas in a molecular state with the thin film to chemically absorb the carbon into the thin film may include maintaining the temperature of the processing chamber at a temperature in the range of 400°C to 600°C.

[0017] Here, the step of permeating the carbon into the thin film by the applied pressure from the process pressure may include maintaining the process pressure at a pressure higher than 2 ATM.

[0018] Here, the step of permeating the carbon into the thin film by the process pressure may include maintaining the process pressure within a range of 5 ATM to 20 ATM. [Effects of the Invention]

[0019] According to the carbon doping method for a thin film on a wafer according to the present invention, a process pressure is created by using an ambient gas in a process chamber containing a wafer on which a thin film has been formed, and a process temperature is created by heating. Then, a carbon-containing source gas is supplied, and the source gas chemically reacts with the thin film at the process pressure and process temperature, thereby doping carbon into the thin film. Therefore, while the properties of the thin film are improved by the carbon doping, the step coverage of the thin film is not impaired because additional carbon is doped into the thin film of an already formed wafer. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a conceptual diagram of a wafer high-pressure processing apparatus 100 used to perform a carbon doping method for a thin film on a wafer according to one embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram for explaining the control operation of the wafer high-pressure processing apparatus 100 of FIG. [Figure 3] 1 is a flowchart illustrating a method for doping carbon into a thin film of a wafer according to an embodiment of the present invention. [Figure 4] 4 is a flowchart for more specifically explaining some steps of FIG. 3. [Figure 5] 4 is a graph comparing carbon concentrations of thin films doped by carbon doping methods for the thin films of the wafers of FIG. 3; [Figure 6] 4 is a graph comparing wet etching depths of thin films doped by carbon doping methods to the thin films of the wafers of FIG. 3; DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, a method for carbon doping a thin film of a wafer according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this specification, the same or similar reference numerals are used to refer to the same or similar components in different embodiments, and the description thereof supersedes the first description.

[0022] FIG. 1 is a conceptual diagram of a wafer high pressure processing apparatus 100 used to perform a carbon doping method for a thin film of a wafer according to one embodiment of the present invention.

[0023] As shown in this figure, the wafer high pressure processing apparatus 100 includes an inner chamber 110 , an outer chamber 120 , an air supply module 130 , and an exhaust module 140 .

[0024] The inner chamber 110 includes a processing chamber 115 for high-pressure processing of semiconductor wafers. The inner chamber 110 may be made of a non-metallic material, such as quartz, to reduce the possibility of contaminants (particles) being generated in the process environment. Although simplified in the drawing, a door (not shown) for opening the processing chamber 115 is provided at the bottom of the inner chamber 110. The processing chamber 115 is opened by lowering the door, and a semiconductor wafer mounted on a holder (not shown) is loaded into the processing chamber 115. The temperature of the processing chamber 115 can reach several hundred degrees Celsius by operating a heater (not shown) located outside the inner chamber 110. The holder may be a wafer boat capable of stacking multiple semiconductor wafers.

[0025] The outer chamber 120 is configured to house the inner chamber 110. Unlike the inner chamber 110, the outer chamber 120 is free from the problem of contamination of semiconductor wafers and may be made of metal. The outer chamber 120 has a housing space 125 that houses the inner chamber 110. The outer chamber 120 also has a door (not shown) at its bottom, which can be lowered together with the door of the inner chamber 110 to open the housing space 125.

[0026] The gas supply module 130 is configured to supply gas to the chambers 110 and 120. The gas supply module 130 includes a gas supplier 131 connected to a utility (gas supply facility) of a semiconductor factory. The gas supplier 131 may supply a carbon-containing source gas, such as ethylene (C2H4) or propylene (C3H6) gas, to the inner chamber 110, specifically the processing chamber 115. The gas supplier 131 may also supply hydrogen, deuterium, nitrogen, or argon gas as an ambient gas to the processing chamber 115. The gas supplier 131 may also supply an inert gas, such as nitrogen or argon gas, as a protective gas to the receiving space 125. The protective gas injected into the receiving space 125 specifically fills the region of the receiving space 125 excluding the inner chamber 110. These gases are injected into the processing chamber 115 or the receiving space 125 via an internal gas line 133 or an external gas line 135, respectively.

[0027] The source gas, the ambient gas, and the protective gas may be supplied at a pressure higher than atmospheric pressure, for example, at a pressure ranging from several atmospheres to several tens of atmospheres. Furthermore, when the pressures of the source gas and the ambient gas are a first pressure and the pressure of the protective gas is a second pressure, they may be maintained in a set relationship. For example, the second pressure may be set to be slightly higher than the first pressure. Such a pressure difference provides the advantage of preventing the source gas and the ambient gas from leaking from the process chamber 115.

[0028] The exhaust module 140 is configured to exhaust the source gas, the ambient gas, and the protective gas from the chambers 110 and 120. An exhaust pipe 141 is connected to the upper part of the inner chamber 110 to exhaust the source gas and the ambient gas from the inner chamber 110, specifically the process chamber 115. A gas exhauster 143 is installed in the exhaust pipe 141. The gas exhauster 143 may be a valve that allows or blocks the exhaust of the source gas and the ambient gas.

[0029] In order to exhaust the protective gas from the outer chamber 120, specifically from the receiving space 125, an exhaust pipe 145 communicating with the outer chamber 120 and a gas exhauster 147 installed therein are provided. These exhaust pipes 141 and 145 communicate with each other, so that the source gas and the ambient gas are exhausted in a state diluted with the protective gas.

[0030] The control configuration of the wafer high pressure processing apparatus 100 will be described with reference to Fig. 2. Fig. 2 is a block diagram for explaining the control operation of the wafer high pressure processing apparatus 100 of Fig. 1.

[0031] Referring to this figure (and FIG. 1), the wafer high pressure processing apparatus 100 may further include a heating module 150, a sensing module 160, a control module 170, and a storage module 180 in addition to the aforementioned gas supply module 130 and the like.

[0032] The heating module 150 includes the heater described above. The heater may be disposed in the receiving space 125. The heater heats the ambient gas and the source gas to a process temperature.

[0033] The sensing module 160 is configured to sense the environment of the chambers 110 and 120. The sensing module 160 may include a pressure gauge 161 and a temperature gauge 165. The pressure gauge 161 and the temperature gauge 165 may be installed in each of the chambers 110 and 120.

[0034] The control module 170 is configured to control the air intake module 130, the air exhaust module 140, etc. The control module 170 can control the air intake module 130, etc. based on the detection result of the detection module 160.

[0035] The storage module 180 is configured to store data, programs, etc. referenced for control by the control module 170. The storage module 180 may include at least one type of storage medium selected from the group consisting of a flash memory, a hard disk, a magnetic disk, and an optical disk.

[0036] According to this configuration, the control module 170 can control the gas supply module 130 and the like to perform the carbon doping method for the thin film of the wafer according to an embodiment of the present invention.

[0037] Specifically, the control module 170 can control the operation of the gas supply module 130 based on the pressure of the chambers 110 and 120 obtained from the pressure gauge 161. By operating the gas supply module 130, the chambers 110 and 120 are filled with the atmospheric gas, the source gas, and the protective gas at the first pressure or the second pressure.

[0038] The control module 170 can also control the operation of the heating module 150 based on the temperatures of the chambers 110 and 120 obtained from the temperature gauge 165. The operation of the heating module 150 allows the source gas and the ambient gas to reach the process temperature.

[0039] A specific method for doping carbon into a thin film on a wafer using the wafer high-pressure processing apparatus 100 will be described with reference to FIGS.

[0040] First, FIG. 3 is a flowchart illustrating a method for doping carbon into a thin film of a wafer according to an embodiment of the present invention.

[0041] Referring to this figure (and FIGS. 1 and 2), a wafer on which a thin film has been formed is placed in a processing chamber 115 (S1). The wafer is loaded into the processing chamber 115 while being secured on a wafer boat. The thin film may be a silicon oxide film (SiO), a silicon nitride film (SiN), a silicon oxynitride film (SiON), or the like. These thin films may be formed by chemical vapor deposition or atomic layer deposition.

[0042] An ambient gas is supplied to the process chamber 115 so that the pressure in the process chamber 115 reaches the process pressure (S3). The ambient gas is supplied to the process chamber 115 through the gas supply module 130 under the control of the control module 170. The ambient gas may be supplied at a higher flow rate than the source gas. Alternatively, the source gas may be supplied at a higher flow rate depending on the desired carbon injection amount.

[0043] The process chamber 115 is heated (S3) so that the temperature of the process chamber 115 reaches the process temperature. This is performed by operating the heating module 150 under the control of the control module 170.

[0044] The source gas is supplied to the process chamber 115 through the gas supply module 130 (S5). The source gas is a carbon-containing gas, and may be ethylene gas or propylene gas, as described above. The source gas also determines the process pressure and the process temperature. The source gas may also be supplied to the process chamber 115 together with the ambient gas.

[0045] Carbon from the source gas is implanted into the thin film (S7) by chemically reacting with the thin film at the process pressure and temperature.

[0046] The formation of the thin film and the carbon injection into the thin film are not performed simultaneously. That is, the carbon is injected into the thin film after the thin film has already been formed. This carbon injection method does not significantly change the pre-defined shape (volume) of the thin film, and therefore does not impair the step coverage of the thin film.

[0047] The above three steps (S3 to S7) will be described in more detail with further reference to Figure 4. Figure 4 is a flowchart for explaining some of the steps in Figure 3 in more detail.

[0048] Referring to this figure (and FIGS. 1 and 2), the source gas maintains its molecular state in the process chamber 115 (S11). To achieve this, the process temperature is maintained below the thermal decomposition temperature of the source gas. Specifically, for ethylene gas or propylene gas, the process temperature may be set within the range of 400°C to 600°C. This is a relatively low temperature compared to the temperature of the thin film deposition process.

[0049] The source gas chemically reacts with the thin film in a molecular state (S13), which is possible because the source gas is maintained in a molecular state due to the process temperature.

[0050] Carbon in the source gas is absorbed into the thin film through a chemical reaction, specifically chemical absorption, between the source gas and the thin film (S15).

[0051] The carbon penetrates deep into the thin film due to the applied pressure (S17). The applied pressure is a force generated by the process pressure. To generate the applied pressure, the process pressure may be higher than atmospheric pressure.

[0052] The setting of the process pressure will be further described with reference to Figures 5 and 6. Figure 5 is a graph comparing the carbon concentration of the thin film doped by the carbon doping method to the thin film of the wafer of Figure 3, and Figure 6 is a graph comparing the wet etching depth of the thin film doped by the carbon doping method to the thin film of the wafer of Figure 3.

[0053] These graphs show the results of an experiment in which carbon doping was performed on a wafer with a silicon dioxide (SiO2) film formed thereon. In this experiment, the silicon dioxide film was 50 nm thick. Ethylene (C2H4) gas was used as the source gas. The process temperature was 400°C. The process pressure was adjusted within the range of 1 Torr to 20 ATM. The solution used for wet etching was a mixture of 100 parts by weight of pure water and 1 part by weight of hydrofluoric acid. Wet etching was performed for 100 seconds.

[0054] 5, when the process pressure is 1 Torr and 1 ATM, the carbon concentration in the thin film is insufficient. The period during which the carbon concentration is maintained at a constant concentration is also short. This is because the effect of carbon doping is not significant.

[0055] On the other hand, when the process pressure is 2 ATM or higher, the carbon concentration is significantly higher than at 1 ATM. At 2 ATM, the carbon concentration far exceeds 1e^10, reaching a significant level. At 2 ATM, the period in which the carbon concentration exceeds 1e^10 is also longer. This is even more true as the process pressure increases to 5 ATM and 10 ATM. In particular, when the process pressure is 5 ATM or higher, there is a period in which the oxygen concentration exceeds 1e^11.

[0056] Referring again to FIG. 6, when the process pressure is 1 Torr and 1 ATM, the wet etching thickness is not significantly different from that without carbon doping (reference).

[0057] On the other hand, when the process pressure is 2 ATM or more, it can be seen that the wet etching thickness is significantly reduced. Specifically, when the process pressure is 2 ATM, the wet etching thickness is reliably reduced to about 90% of the reference thickness.

[0058] The higher the process pressure, the more the wet etching thickness decreases. Specifically, when the process pressure is 5 ATM, the wet etching thickness is approximately mid-60% of the reference. When the process pressure is 10 ATM or even 20 ATM, the wet etching thickness is further reduced to approximately low 60% of the reference.

[0059] In view of the carbon concentration and wet etching thickness, the process pressure of 2 ATM or more significantly enhances the carbon doping effect, and the process pressure of 5 ATM, 10 ATM, or 20 ATM further enhances the carbon doping effect.

[0060] The carbon doping method for a thin film of a wafer as described above is not limited to the configurations and operation modes of the above-described embodiments, and various modifications may be made by selectively combining all or part of each embodiment. [Industrial Applicability]

[0061] The present invention has industrial applicability in the field of carbon doping for thin films on wafers.

Claims

1. placing the wafer with the thin film formed thereon into a processing chamber; supplying an ambient gas into the processing chamber until the pressure in the processing chamber reaches a process pressure higher than atmospheric pressure; heating the processing chamber to a process temperature; supplying a source gas containing carbon into the process chamber, and causing the source gas to chemically react with the thin film at the process pressure and the process temperature, thereby doping the carbon into the thin film.

2. The thin film is 2. The method for carbon doping a thin film of a wafer according to claim 1, wherein the thin film comprises any one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film.

3. The process pressure is 2. The method of carbon doping a thin film on a wafer according to claim 1, wherein the pressure is greater than 2 ATM.

4. The process pressure is 2. The method of carbon doping for a thin film of a wafer according to claim 1, wherein the pressure is determined within the range of 5 ATM to 20 ATM.

5. The process temperature is 2. The method for carbon doping a thin film on a wafer according to claim 1, wherein the temperature is below the thermal decomposition temperature of the source gas.

6. The process temperature is 2. The method of claim 1, wherein the temperature is determined within the range of 400 to 600 degrees Celsius.

7. The source gas is 2. The method of carbon doping a thin film on a wafer according to claim 1, wherein the gas includes one of ethylene gas and propylene gas.

8. The atmospheric gas is H ２ , D ２ , N ２ 2. The carbon doping method for a thin film of a wafer according to claim 1, wherein the carbon doping gas comprises any one of:

9. placing the wafer with the thin film formed thereon into a processing chamber; supplying a carbon-containing source gas into the process chamber; the source gas reacts chemically with the thin film in a molecular state to chemically absorb the carbon into the thin film; and permeating the carbon into the thin film by applying a pressure due to a process pressure.

10. the step of chemically reacting the source gas with the thin film in a molecular state to chemically absorb the carbon into the thin film includes:

10. The method of carbon doping a thin film on a wafer according to claim 9, further comprising the step of maintaining a temperature of the process chamber below a temperature at which the source gas thermally decomposes.

11. the step of chemically reacting the source gas with the thin film in a molecular state to chemically absorb the carbon into the thin film includes:

10. The method of claim 9, further comprising the step of maintaining the temperature of the processing chamber within a range of 400 to 600 degrees Celsius.

12. The step of permeating the carbon into the thin film by the applied pressure of the process pressure includes:

10. The method of claim 9, further comprising maintaining the process pressure at a pressure higher than 2 ATM.

13. The step of permeating the carbon into the thin film by the applied pressure of the process pressure includes:

10. The method of claim 9, further comprising maintaining the process pressure within a range of 5 ATM to 20 ATM.

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