Patent Application
20190181056
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-238355, filed on Dec. 13, 2017, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a method of etching a silicon-containing film formed on a substrate, a non-transitory computer-readable storage medium, and an apparatus of etching the silicon-containing film.
In a semiconductor device, a film containing silicon is applied in a wide variety of applications. For example, a silicon germanium (SiGe) film or a silicon (Si) film is used for a gate electrode, a seed layer or the like. In a manufacturing process of a semiconductor device, the SiGe film or the Si film is formed on a substrate and is etched into a predetermined pattern.
Etching of a silicon-containing film such as a SiGe film or a Si film has been conventionally performed by various methods. For example, the SiGe film or the Si film is etched by exposing the SiGe film or the Si film to an etching gas containing F2, HF, ClF3 or HCl.
Depending on the state of a silicon-containing film which has been subjected to a previous process before an etching process, it may be necessary to control the in-plane distribution of an etching amount when etching the silicon-containing film. For example, when there is a deviation in the film thickness of the silicon-containing film subjected to the previous process, the in-plane uniformity of etching can be improved by controlling the in-plane distribution of an etching amount, for example, by increasing or decreasing an etching amount at the central portion of the silicon-containing film as compared to an etching amount at the outer peripheral portion thereof.
Similarly, even after performing a subsequent process followed by the etching process, it may be necessary to control the in-plane distribution of an etching amount depending on the state of the silicon-containing film. Particularly, along with the miniaturization of semiconductor devices in recent years, the pattern has also been miniaturized. Thus, such control of the etching amount is useful.
However, in the etching method of the related art, the state of the silicon-containing film which has been subjected to the previous process before the etching process or the subsequent process after the etching process is not taken into consideration. Therefore, there is room for improvement in the conventional silicon-containing film etching method.
Some embodiments of the present disclosure provide a technique of appropriately controlling the in-plane distribution of an etching amount of a silicon-containing film when etching the silicon-containing film formed on a substrate.
According to one embodiment of the present disclosure, there is provided a method of etching a silicon-containing film formed on a substrate, including: supplying an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF3 to the silicon-containing film; and controlling etching amounts at a central portion and an outer peripheral portion of the silicon-containing film by controlling a flow velocity of the etching gas.
According to another embodiment of the present disclosure, there is provided a non-transitory computer-readable storage medium storing a program that operates on a computer of a controller for controlling an etching apparatus such that the aforementioned method is performed by the etching apparatus.
According to another embodiment of the present disclosure, there is provided an apparatus of etching a silicon-containing film formed on a substrate, including: a chamber in which the substrate is accommodated; a gas supply part configured to supply an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF3 to the silicon-containing film; an exhaust part configured to discharge the etching gas inside the chamber; and a controller configured to control the gas supply part and the exhaust part, wherein the control part controls etching amounts at a central portion and an outer peripheral portion of the silicon-containing film by controlling a flow velocity of the etching gas.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure.
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the subject specification and the drawings, elements having substantially the same functional configuration will be denoted by like reference numerals and redundant explanation will be omitted. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.
As a result of intensive investigation conducted by the present inventors, it was found that when etching a silicon-containing film, if an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF3 is used and if the etching gas is supplied to the silicon-containing film while controlling a flow velocity of the etching gas, it is possible to control etching amounts in the central portion and the outer peripheral portion of the silicon-containing film. That is to say, when a ClF3 gas was used as the etching gas for the silicon-containing film, it was impossible to control the in-plane distribution of an etching amount of the silicon-containing film. The reason why the in-plane distribution of an etching amount can be controlled by controlling the flow velocity of the etching gas including the fluorine-containing gas will be described in detail in the embodiment described below.
First, the configuration of the etching apparatus according to an embodiment of the present disclosure will be described.
As shown in
The chamber 10 includes a chamber body 20 and a lid 21. An upper portion of the chamber body 20 is opened, and the opening is closed by the lid 21. A top surface of a side wall of the chamber body 20 and a lower surface of the lid 21 are hermetically sealed by a sealing material (not shown), whereby airtightness in the chamber 10 is secured. An airtight etching process space is defined inside the chamber 10. A loading/unloading port (not shown) for loading and unloading the wafer W therethrough is formed in the side wall of the chamber body 20. The loading/unloading port can be opened and closed by a gate valve (not shown).
The mounting table 11 includes an upper table 30 on which the wafer W is mounted and a lower table 31 fixed to a bottom surface of the chamber body 20 and configured to support the upper table 30. A temperature controller 32 for adjusting a temperature of the wafer W is provided inside the upper table 30. The temperature controller 32 adjusts a temperature of the mounting table 11 by circulating a temperature control medium such as, for example, water or the like and controls the temperature of the wafer W mounted on the mounting table 11 to a predetermined temperature.
The gas supply part 12 includes a shower head 40 configured to supply the processing gas to the wafer W mounted on the mounting table 11. The shower head 40 is provided on the lower surface of the lid 21 of the chamber 10 so as face the mounting table 11. A plurality of supply holes 41 for supplying the processing gas therethrough is formed in a lower surface (shower plate) of the shower head 40. The shower head 40 may have a diameter at least larger than that of the wafer W in order to uniformly supply the processing gas over the entire surface of the wafer W mounted on the mounting table 11.
In addition, the gas supply part 12 includes an F2 gas supply source 50 for supplying an F2 gas, an NH3 gas supply source 51 for supplying an NH3 gas, an HF gas supply source 52 for supplying an HF gas, and an Ar gas supply source 53 for supplying an Ar gas. An F2 gas supply pipe 54 is connected to the F2 gas supply source 50, an NH3 gas supply pipe 55 is connected to the NH3 gas supply source 51, an HF gas supply pipe 56 is connected to the HF gas supply source 52, and an Ar gas supply pipe 57 is connected to the Ar gas supply source 53. The supply pipes 54 to 57 are connected to a collective pipe 58 which is connected to the above-described shower head 40. The F2 gas, the NH3 gas, the HF gas and the Ar gas are supplied into the chamber 10 from the shower head 40 via the supply pipes 54 to 57 and the collective pipe 58.
Each of the F2 gas supply pipe 54, the NH3 gas supply pipe 55, the HF gas supply pipe 56 and the Ar gas supply pipe 57 is provided with a flow rate controller 59 for controlling the opening/closing operation of each of the supply pipes 54 to 57 and a flow rate of each of the processing gases. The flow rate controller 59 is constituted by, for example, an opening/closing valve and a mass flow controller.
Among the processing gases supplied from the gas supply part 12, the F2 gas is an etching gas used for main etching. The NH3 gas and the HF gas are used for removing a natural oxide film and terminating a film subjected to an etching process. The Ar gas is used as a dilution gas or a purge gas. Instead of the Ar gas, another inert gas such as an N2 gas or the like may be used, or two or more inert gases may be used.
In the gas supply part 12 of the present embodiment, the processing gases are supplied from the shower head 40 to the wafer W. However, the method of supplying the processing gases is not limited thereto. For example, a gas supply nozzle (not shown) may be provided in the central portion of the lid 21 of the chamber 10, and the processing gases may be supplied from the gas supply nozzle.
The exhaust part 13 includes an exhaust pipe 60 installed outside the mounting table 11 and provided at the bottom of the chamber body 20 of the chamber 10. An exhaust mechanism 61 for evacuating the interior of the chamber 10 is connected to the exhaust pipe 60. An automatic pressure control valve (APC) 62 is provided in the exhaust pipe 60. An internal pressure of the chamber 10 is controlled by the exhaust mechanism 61 and the automatic pressure control valve 62.
The etching apparatus 1 is provided with a control part 70. The control part 70 is, for example, a computer, and includes a program storage part (not shown). In the program storage part, a program for controlling the etching process performed in the etching apparatus 1 is stored. The program may be recorded on a computer-readable storage medium such as a computer-readable hard disk (HD), a flexible disk (FD), a magneto-optical disk (MO), a memory card or the like and may be installed from the storage medium on the control part 70.
Next, an etching method performed in the etching apparatus 1 configured as above will be described. As described above, in the etching apparatus 1 of the present embodiment, the SiGe film formed on the wafer W is etched.
First, in a state in which the gate valve is opened, the wafer W is loaded into the chamber 10 and mounted on the mounting table 11. The temperature of the mounting table 11 is controlled by the temperature controller 32, and the temperature of the wafer W mounted on the mounting table 11 is controlled to a predetermined temperature. Further, when the wafer W is mounted on the mounting table 11, the gate valve is closed to hermetically seal the interior of the chamber 10, whereby an etching process space is formed in the chamber 10.
Thereafter, the NH3 gas and the HF gas are supplied into the chamber 10 while regulating the internal pressure of the chamber 10, whereby the natural oxide film formed on the wafer W is removed. At this time, in addition to the NH3 gas and the HF gas, the Ar gas may be supplied as a dilution gas. In some embodiments, the NH3 gas may be first supplied into the chamber 10 to stabilize the internal pressure and then the HF gas may be introduced into the chamber 10.
Thereafter, while supplying the Ar gas as a purge gas into the chamber 10, evacuation is performed to purge the interior of the chamber 10.
Thereafter, the F2 gas is supplied as an etching gas into the chamber 10. At this time, the Ar gas may be added as a dilution gas. Then, the SiGe film on the wafer W is etched by the etching gas.
In the etching apparatus 1, the SiGe film on the wafer W is etched as described above. Next, a method of controlling the in-plane distribution of an etching amount when etching the SiGe film will be described.
As a result of verification under various etching conditions, the present inventors have found that if a flow velocity of the etching gas including the F2 gas is controlled when etching the SiGe film, it is possible to control etching amounts at the central portion and the outer peripheral portion of the SiGe film. The flow velocity of the etching gas referred to herein is a flow velocity of the etching gas supplied to the SiGe film inside the chamber 10. The control of the flow velocity of the etching gas is performed by controlling a flow rate of the etching gas supplied to the SiGe film inside the chamber 10 or the internal pressure of the chamber 10. Based on the verification results, the aforementioned findings will be described below.
In general, the F2 gas or the ClF3 gas is often used as the etching gas for the SiGe film. In the case of using the F2 gas or the ClF3 gas, the present inventors changed the flow rate of the etching gas and compared the in-plane distributions of an etching amount. The flow rate of the etching gas is controlled, for example, by the flow rate controller 59. In addition, the etching gas contains the Ar gas as a dilution gas. In the present verification, the flow rate of the etching gas as a whole was changed by changing the flow rate of the Ar gas. In the verification using the F2 gas or the ClF3 gas, the internal pressure of the chamber 10 is kept constant at 150 to 250 mT.
The results of this verification are shown in
As shown in
On the other hand, as shown in
In the verification shown in
As shown in
In the verification shown in
As shown in
As described above, according to the verification results shown in
Next, a mechanism which controls the etching amounts at the central portion and the outer peripheral portion of the SiGe film by controlling the flow velocity of the etching gas including the F2 gas in the aforementioned manner will be described.
On the other hand,
As described above, the etching amounts at the central portion and the outer peripheral portion of the SiGe film vary depending on whether the flow velocity of the etching gas is high or low. This is because the molecular weight of the F2 contained in the etching gas is at a low level of 38. That is to say, as will be described later, the F2 has a small molecular weight, a long incubation time and a moderate reactivity. Therefore, the in-plane distribution of the etching amount varies depending on the flow velocity of the etching gas.
On the other hand, when the molecular weight of the F2 is at a high level of 92.45 as in ClF3, the etching gas is likely to be supplied to the central portion of the SiGe film regardless of the flow velocity of the etching gas. Therefore, in the case of using the etching gas including the ClF3 gas, the etching amount at the central portion becomes larger than the etching amount at the outer peripheral portion. Thus, the in-plane distribution of the etching amount cannot be controlled.
Further, as shown in
Further, as shown in
As described above, ClF3 has a larger molecular weight than F2, and the incubation time of ClF3 is relatively short due to the difference in molecular weight. Moreover, ClF3 is more reactive than F2. Therefore, in the case of the etching gas including the ClF3 gas, it is difficult to control the in-plane distribution of the etching amount.
In other words, F2 has a smaller molecular weight than ClF3, and the incubation time of F2 is relatively long due to the difference in molecular weight. In addition, the reactivity of F2 is moderate. Therefore, in the case of using the etching gas including the F2 gas, as shown in
Furthermore, as a result of investigation conducted by the present inventors, it was found that if the etching gas contains a fluorine-based gas having a smaller molecular weight than ClF3, the incubation time becomes longer and the reactivity becomes moderate. For this reason, it is possible to obtain the same tendency as the tendency shown in
Next, application examples of the above etching control will be described. As the application examples, description will be made on a case where the etching control is applied to the setting of etching conditions (application example 1), a case where the etching control is applied to a feed-forward control based on the state of the silicon-containing film subjected to a previous process before etching (application example 2), a case where the etching control is applied to a feed-back control based on the state of the silicon-containing film subjected to a subsequent process followed by etching (application example 3), and a case where the etching control is applied to a feed-back control based on the state of the silicon-containing film immediately after etching (application example 4).
The etching condition setting of the application example 1 will be described. In the application example 1, first, an etching gas including an F2 gas is supplied to a wafer Wc for etching condition setting to etch an SiGe film. The wafer Wc is not a product wafer W manufactured on an in-line basis but is a wafer used only for setting the etching conditions. Thereafter, the in-plane distribution of the etching amount of the etched SiGe film is measured. Any well-known method may be used for measuring the etching amount. Thereafter, based on the measurement result, the etching amount of the SiGe film is set in the plane so that the SiGe film after the etching has a desired size in the plane. The flow velocity of the etching gas is set based on this etching amount. For example, when it is desired to make an etching amount at the central portion of the SiGe film larger than an etching amount at the outer peripheral portion, the flow rate of the etching gas and the internal pressure of the chamber 10 are set so that the flow velocity of the etching gas becomes relatively high. Under the conditions thus set, the product wafer W is etched.
The feed-forward control of the application example 2 will be described. In the application example 2, the previous process before etching is performed on a wafer W manufactured on an in-line basis. Thereafter, immediately before the wafer W is loaded into the etching apparatus 1, the state of the SiGe film formed on the wafer W, for example, the film thickness of the SiGe film is measured. Any well-known method can be used for the measurement of the film thickness. Thereafter, the flow velocity of the etching gas is corrected based on the measurement result. For example, when the measurement result indicates that the film thickness at the central portion of the SiGe film is larger than the film thickness at the outer peripheral portion, the etching amount at the center portion is set larger than the etching amount at the outer peripheral portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber 10 are set so that the flow velocity of the etching gas becomes relatively high. On the other hand, for example, when the measurement result indicates that the film thickness at the outer peripheral portion of the SiGe film is smaller than the film thickness at the central portion, the etching amount at the outer peripheral portion is set larger than the etching amount at the central portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber 10 are set so that the flow velocity of the etching gas becomes relatively low. Then, the wafer W is etched under the corrected set conditions.
The feed-back control of the application example 3 will be described. In the application example 3, the subsequent process followed by etching is performed on a wafer W manufactured on an in-line basis, the state of the SiGe film formed on the wafer W, for example, the film thickness of the SiGe film is measured. Thereafter, the flow velocity of the etching gas is corrected based on the measurement result. For example, when the measurement result indicates that the film thickness at the central portion of the SiGe film is larger than the film thickness at the outer peripheral portion, the etching amount at the central portion is set larger than the etching amount at the outer peripheral portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber 10 are set so that the flow velocity of the etching gas becomes relatively high. On the other hand, for example, when the measurement result indicates that the film thickness at the outer peripheral portion of the SiGe film is smaller than the film thickness at the central portion, the etching amount at the outer peripheral portion is set larger than the etching amount at the central portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber 10 are set so that the flow velocity of the etching gas becomes relatively low. Then, a subsequent wafer W is etched under the corrected set conditions.
The feed-back control of the application example 4 will be described. In the application example 4, immediately after etching, the state of the SiGe film formed on the wafer W manufactured on an in-line basis, for example, the film thickness of the SiGe film is measured. Thereafter, the flow velocity of the etching gas is corrected based on the measurement result. For example, when it is desired to make the etching amount at the central portion of the SiGe film larger than the etching amount at the outer peripheral portion, the flow rate of the etching gas and the internal pressure of the chamber 10 are set so that the flow velocity of the etching gas becomes relatively high. On the other hand, for example, when it is desired to make the etching amount at the outer peripheral portion of the SiGe film larger than the etching amount at the central portion, the flow rate of the etching gas and the internal pressure of the chamber 10 are set so that the flow velocity of the etching gas becomes relatively low. Then, a subsequent wafer W is etched under the corrected set conditions.
In the above embodiment, the etching control when etching the SiGe film has been described. However, the etching control of the present disclosure may also be applied to other silicon-containing films.
For example, when etching a silicon (Si) film, for example, a mixed gas of an F2 gas and an NH3 gas is used as the etching gas. The gas to be mixed with the F2 gas is not limited to the NH3 gas and may be any basic gas.
As in the above embodiment, it is possible to control the in-plane distribution of the etching amount of the Si film by controlling the flow velocity of the etching gas including the F2 gas and the NH3 gas. That is to say, by increasing the flow velocity of the etching gas, the etching amount at the central portion of the Si film can be made larger than the etching amount at the outer peripheral portion. Further, by lowering the flow velocity of the etching gas, the etching amount at the outer peripheral portion of the Si film can be made larger than the etching amount at the central portion. Since the mechanism of etching control of the Si film is similar to the mechanism of etching control of the SiGe film of the above embodiment, the detailed description thereof will be omitted.
According to the present disclosure in some embodiments, it is possible to appropriately control an in-plane distribution of an etching amount of a silicon-containing film by controlling a flow velocity of an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF3 when etching the silicon-containing film formed on a substrate.
Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to this embodiment. Those having ordinary knowledge in the technical field to which the present disclosure belongs may clearly appreciate that various modifications or changes can be conceived within the scope of the technical idea described in the claims. It is understood that these modifications or changes fall within the technical scope of the present disclosure as well.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-238355 | Dec 2017 | JP | national |
