JP2022184730A - Substrate processing method and substrate processing apparatus - Google Patents

Abstract

To suppress roughness on the surface of an etched silicon film.SOLUTION: A first step for supplying processing gas containing halogen-containing gas and basic gas to a substrate in which a silicon film is formed on the surface and the substrate itself is set to a first temperature and generating a reaction product by altering the surface of the silicon film and a second step for removing the reaction product by setting the substrate to the second temperature after the first step.SELECTED DRAWING: Figure 1C

Description

The present disclosure relates to a substrate processing method and a substrate processing apparatus.

2. Description of the Related Art In manufacturing a semiconductor device, a Si film out of a Si film and a SiGe film formed on a surface of a semiconductor wafer (hereinafter referred to as a wafer), which is a substrate, may be selectively etched. For example, Patent Document 1 describes that the above selective etching is performed by using _F2 gas and _NH3 gas as etching gases and setting the ratio of _NH3 gas to the etching gas to a predetermined value. .

Japanese Patent No. 6426489

The present disclosure provides a technique capable of suppressing surface roughness of a silicon film after etching.

In the substrate processing method of the present disclosure, a processing gas containing a halogen-containing gas and a basic gas is supplied to a substrate having a silicon film formed thereon and set to a first temperature, thereby altering the surface of the silicon film. a first step of producing a reaction product;
a second step of removing the reaction product by setting the substrate to a second temperature after the first step;
including.

According to the present disclosure, surface roughness of the silicon film after etching can be suppressed.

1 is a longitudinal side view of a wafer to be processed according to the first embodiment of the present disclosure; FIG. It is a longitudinal side view of the wafer. It is a longitudinal side view of the wafer. It is a longitudinal side view of the wafer. It is a longitudinal side view of the wafer. It is a longitudinal side view of the wafer. It is a longitudinal side view showing the surface of a wafer. It is a longitudinal side view showing the surface of a wafer. It is a top view which shows one Embodiment of the substrate processing apparatus for performing the said process. It is a vertical side view which shows an example of the processing module provided in the said substrate processing apparatus. FIG. 5 is a vertical cross-sectional side view of a wafer to be processed according to a second embodiment of the present disclosure; It is a longitudinal side view of the recessed part formed in the said wafer. It is explanatory drawing which shows the change of the said recessed part. It is explanatory drawing which shows the change of the said recessed part. It is explanatory drawing which shows the change of the said recessed part. It is explanatory drawing which shows the change of the said recessed part. It is a top view which shows the result of an evaluation test. It is a top view which shows the result of an evaluation test. It is a schematic diagram of the recessed part of a wafer which shows the result of an evaluation test. It is a graph chart which shows the result of an evaluation test.

[First Embodiment]
The outline of the processing that is the first embodiment of the substrate processing method of the present disclosure will be described. FIG. 1A is a longitudinal side view of the surface of a wafer W, which is a substrate before processing. On the surface of the wafer W, a Si (silicon) film 11 and a SiGe (silicon germanium) film 12, which is a silicon-containing film, are exposed. ing. Of the Si film 11 and the SiGe film 12, only a portion of the Si film 11 is selectively etched. That is, etching is performed so that the Si film 11 remains on the wafer W after processing.

In this etching, a halogen-containing gas and a basic gas are supplied to the wafer W as processing gases so that the above-described selective etching can be performed. Step S1 of selectively altering the surface of 11 to generate a reaction product is performed. In this embodiment, the halogen-containing gas is F ₂ (fluorine) gas, and the basic gas is NH ₃ (ammonia) gas. After step S1 (first step) is performed, the surface of the Si film 11 is selectively etched by performing step S2 (second step) in which the reaction product is sublimated by heat treatment. The above reaction product is ammonia fluorosilicate (AFS).

The formation and sublimation of the reaction product described above are repeated. That is, a repetition process is performed in which the first process and the second process are repeated in order, and the etching amount of the Si film 11 is controlled. The Si film 11 is made to remain on the surface of the wafer W at the end of this repeated process (that is, at the end of the etching). Concavities and convexities are formed on the surface of the Si film 11 that remains later, and the roughness of the surface becomes relatively large. The processing of the present embodiment is performed so as to suppress this surface roughness.

Next, with reference to FIGS. 1 to 3, the processing performed on the wafer W will be described in order. The arrows in each drawing indicate the processing gas, and the processing shown in each drawing is performed in a state in which the wafer W is loaded into a processing container and the inside of the processing container is evacuated to a vacuum atmosphere of a predetermined pressure. The wafer W being processed is adjusted to a desired temperature. In this embodiment, steps S1 and S2 are performed in different processing containers.

First, for example, the inside of the processing container is evacuated to, for example, 100 mTorr (13.3 Pa) to 10 Torr (1333 Pa), and the temperature of the wafer W is adjusted to a first temperature, for example, -20°C to 60°C. . Such a temperature range is used to prevent sublimation of the AFS, although the above-described reaction for generating AFS occurs due to the processing gas. The reason why sublimation is not performed will be described later. It is more preferable to set the temperature of the wafer W to, for example, 20.degree. C. to 30.degree.

While the temperature of the wafer W is adjusted in this manner, the _F2 gas and the _NH3 gas, which are processing gases, are supplied into the processing chamber, and the surface of the Si film 11 is altered as described above. An AFS layer 13 is formed on the surface. For example, it is assumed that the thickness of the AFS layer 13 varies due to variations in gas concentration distribution and flow in the processing container (FIG. 1B). However, since the temperature of the wafer W is adjusted so that the AFS layer 13 remains without sublimation, the processing gas is further supplied to the wafer W while the AFS 13 covers the Si film 11 .

The processing gas permeates through the AFS layer 13 to reach the underlying Si film 11 at a portion where the AFS layer 13 is relatively thin, thereby altering the Si film 11 . However, the portion where the AFS layer 13 is relatively thick prevents the processing gas from permeating downward, and the deterioration of the Si film is less likely to occur below the portion where the AFS layer 13 is relatively thick. Therefore, the thickness of the AFS layer 13 is homogenized (FIG. 1C). When the thickness of the AFS layer 13 is uniformized in this manner, the supply of the processing gas is stopped, and step S1 ends.

Subsequently, step S2 (second step) is performed, and the wafer W is heated to a second temperature higher than the temperature in step S1 (first step), eg, 80.degree. C. to 300.degree. This heating sublimates and removes the AFS layer 13, exposing the Si film 11 covered with the AFS layer 13 (FIG. 2A). In this way, the surface of the Si film 11 is etched in a series of steps S1 and S2. Etched with high uniformity. Therefore, formation of unevenness is suppressed on the surface of the Si film 11 after etching.

After that, step S1 is performed again. Therefore, the processing gas is supplied to the wafer W adjusted to the temperature described above, and the surface of the Si film 11 selectively becomes the AFS layer 13 (FIG. 2B). By continuing to supply the processing gas while the AFS layer 13 remains, the thickness of each portion of the AFS layer 13 is made uniform (FIG. 2C). Subsequently, step S2 is performed again. Therefore, the AFS layer 13 formed in the second step S1 is sublimated (FIG. 3A). As the process progresses in this way, the formation of irregularities on the surface of the Si film 11 after the second etching (after the second steps S1 and S2 are performed) is suppressed.

After that, the cycle consisting of steps S1 and S2 is repeated, and the selective etching of the Si film 11 progresses. Then, when the remaining Si film 11 reaches a desired thickness, the repeated processing of steps S1 and S2 is stopped. That is, the etching process is stopped so that the Si film 11 remains on the wafer W (FIG. 3B). In the third and subsequent cycles, the formation of irregularities on the surface of the Si film 11 is suppressed in the same manner as in the first and second cycles. there is In other words, the process is finished with the roughness of the surface of the Si film 11 suppressed.

Next, a substrate processing apparatus 2, which is an embodiment of the substrate processing apparatus that performs the series of processes described with reference to FIGS. 1 to 3, will be described with reference to the plan view of FIG. The substrate processing apparatus 2 includes a loading/unloading section 21 for loading/unloading the wafer W, two load-lock chambers 31 provided adjacent to the loading/unloading section 21, and two load-lock chambers 31 adjacent to each other. Two heat treatment modules 30 provided and two treatment modules 4 provided adjacent to the two heat treatment modules 30 are provided.

The loading/unloading section 21 includes a normal pressure transfer chamber 23 in which a first substrate transfer mechanism 22 is provided and a normal pressure atmosphere, and a carrier provided on the side of the normal pressure transfer chamber 23 for storing the wafer W. and a carrier mounting table 25 on which 24 is mounted. Reference numeral 26 in the figure denotes an orienter chamber adjacent to the normal pressure transfer chamber 23, which is provided for rotating the wafer W to optically obtain the amount of eccentricity and aligning the wafer W with the first substrate transfer mechanism 22. . The first substrate transfer mechanism 22 transfers the wafer W between the carrier 24 on the carrier mounting table 25 , the orienter chamber 26 and the load lock chamber 31 .

A second substrate transfer mechanism 32 having, for example, a multi-joint arm structure is provided in each load lock chamber 31 . and the processing module 4. The inside of the processing container that constitutes the heat treatment module 40 and the inside of the processing container that constitutes the processing module 4 are in a vacuum atmosphere, and the inside of the load lock chamber 31 includes the inside of these vacuum atmosphere processing containers and the normal pressure transfer chamber 23 . A normal pressure atmosphere and a vacuum atmosphere are switched so that the wafer W can be transferred between the two.

In the figure, 33 is a gate valve that can be opened and closed between the normal pressure transfer chamber 23 and the load lock chamber 31, between the load lock chamber 31 and the heat treatment module 30, and between the heat treatment module 30 and the treatment module 4, respectively. is provided. The heat treatment module 30 includes the above-described processing container, an exhaust mechanism for evacuating the inside of the processing container to form a vacuum atmosphere, a stage provided in the processing container and capable of heating the wafer W mounted thereon, and the like. , is configured to be able to execute step S2.

The processing module 4 will be described with reference to the longitudinal side view of FIG. This processing module 4 executes step S1 already described. Reference numeral 41 in the drawing denotes a processing container that constitutes the processing module 4 . Reference numeral 42 in the drawing denotes a transfer port for wafers W which opens in the side wall of the processing container 41 and is opened and closed by the gate valve 33 described above. A stage 51 on which the wafer W is placed is provided in the processing container 41, and the stage 51 is provided with lifting pins (not shown). The wafer W is transferred between the second substrate transfer mechanism 32 and the stage 51 via the elevating pins.

A temperature adjustment unit 52 is embedded in the stage 51, and the temperature of the wafer W placed on the stage 51 is set to the temperature described above. The temperature adjustment unit 52 is configured as a flow path forming a part of a circulation path in which a temperature adjustment fluid such as water flows, and the temperature of the wafer W is adjusted by heat exchange with the fluid. However, the temperature adjustment unit 52 is not limited to being such a fluid flow path, and may be configured by a heater for performing resistance heating, for example.

One end of the exhaust pipe 53 is open in the processing container 41, and the other end of the exhaust pipe 53 is connected to an exhaust mechanism 55 composed of, for example, a vacuum pump via a valve 54, which is a pressure change mechanism. It is By adjusting the degree of opening of the valve 54, the pressure in the processing container 41 is set within the range described above, and processing is performed.

A gas shower head 56 , which is a processing gas supply mechanism, is provided on the upper side inside the processing container 41 so as to face the stage 51 . The downstream side of the gas supply paths 61 to 64 is connected to the gas shower head 56, and the upstream side of the gas supply paths 61 to 64 is connected to the gas supply sources 66 to 69 via the flow rate adjusting section 65, respectively. there is Each flow control unit 65 has a valve and a mass flow controller. The gas supplied from the gas supply sources 66 to 69 is supplied or cut off to the downstream side by opening and closing valves included in the flow rate adjusting section 65 .

Gas supply sources 66, 67, 68, and 69 supply _F2 gas, _NH3 gas, Ar (argon) gas, and _N2 (nitrogen) gas, respectively. Therefore, these HF gas, NH ₃ gas, Ar gas, and N ₂ gas can be supplied into the processing container 41 from the gas shower head 56 . Ar gas and N ₂ gas are supplied into the processing container 41 together with F ₂ gas and NH ₃ gas as carrier gases. Regarding the flow rate of the F ₂ gas and the NH ₃ gas supplied into the processing chamber 41 in such a manner, the flow rate of the F ₂ gas is, for example, 100 sccm to 1000 sccm, and the flow rate of the NH ₃ gas is, for example, 4 sccm to 80 sccm.

By the way, as shown in FIG. 4, the substrate processing apparatus 2 has a control section 20 which is a computer, and the control section 20 has a program, a memory, and a CPU. The program incorporates commands (each step) to perform the above-described wafer W processing and wafer transfer. etc., and installed in the control unit 20 . The control unit 20 outputs a control signal to each unit of the substrate processing apparatus 2 according to the program, and controls the operation of each unit. Specifically, the operation of the processing module 4, the operation of the heat treatment module 30, the operations of the first substrate transfer mechanism 22, the second substrate transfer mechanism 32, and the orienter chamber 26 are controlled by control signals. The operation of the processing module 4 includes, for example, the temperature of the fluid supplied to the stage 51, the supply/stop of each gas from the gas shower head 56, and the adjustment of the exhaust flow rate by the valve 54.

A transfer route of the wafer W in the substrate processing apparatus 2 will be described. The carrier 24 storing the wafer W on which each film is formed as described with reference to FIG. 1A is mounted on the carrier mounting table 25 . Then, the wafer W is transferred in the order of normal pressure transfer chamber 23 →orienter chamber 26 →normal pressure transfer chamber 23 →load lock chamber 31 and transferred to processing module 4 via heat treatment module 30 . Then, as described above, the processing described as step S1 is performed to form the AFS layer 13 . Subsequently, the wafer W is transferred to the heat treatment module 40, and sublimation of the AFS layer 13 in step S2 is performed.

Thereafter, the wafer W is transported back and forth between the processing module 4 and the thermal processing module 40, thereby repeating steps S1 and S2 a predetermined number of times. After that, the wafer W is transferred from the heat treatment module 40 to the load lock chamber 31 →the normal pressure transfer chamber 23 in this order and returned to the carrier 24 .

According to the processing method shown in this embodiment, as described above, the Si film 11 can be selectively etched from among the Si film 11 and the SiGe film 12, and the roughness of the surface of the Si film 11 after the etching process can be reduced. can be suppressed. Therefore, the yield of semiconductor products manufactured from the wafer W after the etching process can be increased.

In the processing example described above, steps S1 and S2 are shown to be repeated three times or more in etching the Si film 11, but the number of repetitions is not limited to the above example, and may be, for example, two times. Steps S1 and S2 may be performed only once without being repeated. In the substrate processing apparatus 2 described above, the wafer W is transferred between the processing module 4 and the thermal processing module 40, and steps S1 and S2 are performed in different processing containers. The steps S1 and S2 may be performed by changing the temperature of the stage 51 of the processing module 4, for example. That is, steps S1 and S2 may be performed in the same processing container. However, in this case, when steps S1 and S2 are repeatedly performed, time is required to lower the temperature of the stage 51 in order to perform step S1 again after performing step S2. Therefore, in order to obtain a high throughput in repeating steps S1 and S2, it is preferable that steps S1 and S2 be placed on stages in different processing vessels as described above.

Although the SiGe film 12 is exposed on the surface of the wafer W in the example described above as the silicon-containing film, a SiN film or SiO ₂ film, for example, may be exposed on the surface of the wafer W instead of the SiGe film 12. good. These SiN films and SiO ₂ films have a lower Si content than Si films. Therefore, compared to the Si film 11, AFS is less likely to occur due to NH ₃ gas and F ₂ gas. Therefore, even if the SiN film and the SiO ₂ film are exposed on the surface of the wafer W instead of the SiGe film 12, the Si film 11 can be selectively etched. Halogen gas is not limited to _F2 gas. For example, _IF7 gas, _IF5 gas, _ClF3 gas, and _SF6 gas may be used to form the AFS layer 13 and perform similar processing. can.

In the above example, the F ₂ gas and the NH ₃ gas are simultaneously supplied to the wafer W for processing, that is, the F ₂ gas supply period and the NH ₃ gas supply period coincide. , is not limited to supplying each gas as such. For example, F ₂ gas and NH ₃ gas are supplied alternately and repeatedly, and one of the F ₂ gas and NH ₃ gas adsorbed on the Si film 11 reacts with the other gas to generate AFS. You may make it In other words, each of these gases may be supplied so that the period of supplying the _F2 gas and the period of supplying the _NH3 gas do not overlap each other. Further, each gas may be supplied so that the period of supplying the _F2 gas and the period of supplying the _NH3 gas only partially overlap. However, by supplying F ₂ gas and NH ₃ gas at the same time as in the processes of FIGS. , is preferable because it can increase the throughput.

In the above example, sublimation of the AFS layer 13 is performed by raising the temperature of the wafer W in step S2 higher than that in step S1. can't For example, it is assumed that step S2 is also performed by the processing module 4 in the same manner as step S1. Then, when step S2 is executed, the opening of the valve 54 of the exhaust pipe 53 is made larger than when step S1 is executed. As a result, the pressure in the processing container 41 during execution of step S2 is made lower than that during execution of step S1. The pressure change may cause the AFS layer 13 to sublimate.

[Second embodiment]
The second embodiment will be described assuming that the wafer W having the structure 71 shown in FIG. 6 formed thereon is processed. FIG. 6 is a longitudinal side view of the structure 71. As shown in FIG. The structure 71 is provided with a Si film, and a recess 72 is formed in the Si film in the vertical direction (thickness direction of the wafer W). and a recess 73 bored in the Si film so as to face rightward. The recess 72 is open to the surface of the wafer W, and each gas supplied to the wafer W is introduced into the recess 73 through the recess 72 . Since the recesses 73 are formed at different heights in the vertical direction on the left and right sides of the recesses 72 , the recesses 73 and the Si film are formed in the vertical direction on the left and right sides of the recesses 72 . They are lined up alternately.

The structure 71 will be further described with reference to the vertical cross-sectional side view of FIG. Since the structure is as described above, the upper and lower walls forming the recess 73 are formed of a Si film, which is shown as a Si film 74 in the drawing. Moreover, the sidewalls forming the recess 73 are made of the SiGe film 75 . In the second embodiment, the Si film 74 forming the upper and lower walls of the recess 73 is selectively etched with respect to the SiGe film 75 to reduce the vertical thickness of the Si film 74 . That is, the opening width of the concave portion 73 is widened. This etching is performed so as to suppress roughness of the surface of the Si film 74 after etching.

The etching process in the second embodiment will be described below with reference to FIGS. 8 to 11, focusing on differences from the etching process in the first embodiment. 8 to 11 are schematic diagrams showing how the Si film 74 changes presumably during processing. In this process, in addition to _NH3 gas, _F2 gas and HF (hydrogen fluoride) gas are used as fluorine-containing gases. In the figure, _F2 gas is represented by 81, _NH3 gas by 82, and HF gas by 83.

First, the pressure in the processing container 41 in which the wafers W are stored and the temperature of the wafers W in the processing container 41 are adjusted to the same pressure and temperature as in step S1 of the first embodiment, for example. As in step S1, the _F2 gas 81 and the _NH3 gas 82 are simultaneously supplied (FIG. 8, step T1). As a result, the surface layer of the Si film 74 forming the recess 73 is altered, and the AFS layer 13 is produced. When the AFS layer 13 is formed, fine unevenness is formed on the surface layer of the Si film 74 by the action of each gas, and the AFS layer 13 is formed so as to cover the Si film 74 having such unevenness. (Fig. 9).

After the F ₂ gas 81 and NH ₃ gas 82 into the processing container 41 are stopped, the N ₂ gas is supplied into the processing container 41 and exhausted, and the remaining F ₂ gas 81 and NH 3 gas are discharged. ₃ gas 82 is purged and removed from the processing container 41 (step T2). Thereafter, HF gas 83 is supplied into the processing container 41 (FIG. 10: step T3), and the HF gas 83, the AFS layer 13, and the Si film 74 in contact with the AFS ((NH ₄ ) ₂ SiF ₆ ) layer 13 are It is considered that the reaction represented by the following formula 1 occurs between
2Si+( _{( NH4} ) _2SiF6 )+4HF→ _SiF6 + _{SiH4 +} ( _NH4 ) _2SiF6 Formula 1

To describe the above reaction in detail, the AFS layer 13 formed in step T1 contains a relatively large amount of fluorine. By supplying the HF gas 83 also containing fluorine in step T3, the fluorine in the AFS layer 13 becomes even more excessive, and the extreme surface of the Si film 74 in contact with the AFS layer 13 is fluorinated. It is referred to as an altered layer 75 . In this way, it is considered that the fluorine contained in the AFS layer 13 is used with the supply of the fluorine-containing gas as a trigger, so that the extreme surface of the Si film 74 is changed to the deteriorated layer 75 .

After that, the supply of the HF gas 83 into the processing container 41 is stopped, the N ₂ gas is supplied into the processing container 41, and the processing container 41 is exhausted. (step T4). After that, similarly to step S2 of the first embodiment, the wafer W is heated to a temperature higher than that in steps T1 to T4, eg, 80.degree. C. to 300.degree. By this heating, the AFS layer 13 and the altered layer 75 are sublimated and removed, exposing the Si film 74 covering these layers (FIG. 11: step T5).

As described above, the surface roughness of the Si film 74 exposed in step T5 is suppressed by removing the extreme surface of the Si film 74 on which unevenness is formed after step T1. As in the first embodiment, the Si film 74 is selectively etched out of the Si film 74 and the SiGe film 75 by the above process. After that, the cycle consisting of steps T1 to T5 is repeated, the selective etching of the Si film 11 progresses, the thinning of the Si film 74 progresses, and when the Si film 74 reaches a desired thickness, The repeated processing of steps T1 to T5 is stopped.

According to the etching process of the second embodiment described above, the roughness of the Si film after etching can be more reliably suppressed, as will be shown in later evaluation tests. For example, the substrate processing apparatus 2 described with reference to FIG. 4 can also be used for the etching process of this second embodiment. Note that steps T1 to T4 performed in the processing module 4 correspond to a first step of altering the Si film 74 to generate a reaction product. In the step T1, the first supply of the _F2 gas, which is the first fluorine-containing gas, to the wafer W and the supply of the _NH3 gas, which is a basic gas, to the wafer W in parallel. It corresponds to a process. Further, step T3 corresponds to the second supply step, and in this example, the HF gas, which is the second fluorine-containing gas different in kind from the first fluorine-containing gas, is supplied to the wafer W as described above. will be

For the processing module 4 that performs steps T1 to T4 in this manner, for example, in addition to the gas supply sources 66 to 69 already described, an HF gas supply source is provided. are connected via a channel. A flow rate adjusting unit 65 is interposed in the HF gas flow path in the same manner as other gas flow paths, and the HF gas is supplied into the processing container 41 at a desired flow rate through the gas shower head 56. . When supplying the HF gas into the processing container 41, for example, Ar gas and N ₂ gas are also supplied into the processing container 41 as carrier gases.

By the way, in step T3, a gas that acts on the AFS layer 13 to cause a reaction between the fluorine contained in the AFS layer 13 and the Si film 74 may be used. F ₂ gas, NF ₃ (nitrogen trifluoride) gas, or the like may be used. When _F2 gas is used, the same type of fluorine-containing gas is used in steps T1 and T3. In the processing example described above, purging with _N2 gas, which is an inert gas, is performed in step T2 so that the processing in step T3 is suppressed from being affected by the gas used in step T1. If _F2 gas is used in both T1 and T3, step T2 may be omitted. Specifically, first, both the _F2 gas and the _NH3 gas are supplied into the processing container 41 in step T1, and then the supply of the _NH3 gas out of the _F2 gas and the _NH3 gas is stopped to supply the _F2 gas. By setting the state in which only is supplied into the processing container 41, step T2 can be omitted and the processing of step T3 can be performed.

Also, in step T3, NH ₃ gas may be supplied instead of the fluorine-containing gas. As described above, the AFS layer 13 contains a large amount of fluorine. By supplying NH ₃ gas, the fluorine of the AFS layer 13, NH ₃ and the extreme surface of the Si film 74 react with each other. The extreme surface of the Si film 74 is transformed into a reaction product, which is sublimated and removed together with the AFS layer 13 in step T5. Roughness on the surface of the Si film 74 after step T5 is thereby suppressed. When NH ₃ gas is supplied in step T3 as described above, step T2 may be omitted as in the case of using F ₂ gas in step T3.

As described above, after performing the first supply step in which the F ₂ gas (first fluorine-containing gas) is supplied to the wafer W and the NH ₃ gas is supplied to the wafer W in parallel, The gas supplied to the wafer W in the second supply step is not limited to the second fluorine-containing gas different in kind from the first fluorine-containing gas. By the way, in the first embodiment, the supply periods of the _F2 gas and the _NH3 gas are the same in this specification (the supply start timing is the same for each gas and the supply end timing is the same for each gas). being) is to supply at the same time. In the second embodiment, when the F ₂ gas and the NH ₃ gas are supplied in parallel, the timing of starting the supply of these gases is not limited to be the same. In other words, the supply of _F2 gas and _NH3 gas is not limited to the simultaneous supply described in this specification.

In addition, steps T1 to T5 are not limited to being repeatedly performed multiple times, and may be performed only once. Furthermore, although an example of etching the wall surface of the concave portion 73 formed in the lateral direction of the structure 71 has been shown, the portion to be etched is arbitrary, and the etching is not limited to the wall surface.

In addition, the embodiment disclosed this time should be considered as an example and not restrictive in all respects. The above-described embodiments may be omitted, substituted, modified, and combined in various ways without departing from the scope and spirit of the appended claims.

〔Evaluation test〕
・Evaluation test 1
Evaluation tests conducted in relation to the technology of the present disclosure will be described. As an evaluation test 1, the wafer W was subjected to an etching process in which steps S1 and S2 were repeated multiple times as described in the embodiment. As for the wafer W used in this process, the Si film 11 and the SiGe film 12 are exposed on the surface as shown in the embodiment. In step S1 of this evaluation test 1, the flow rate of the _F2 gas and the flow rate of the _NH3 gas supplied into the processing container storing the wafer W were set to values within the ranges described above. As described in the embodiment, together with the flow rate of _F2 gas and _NH3 gas, Ar gas and _N2 gas were also supplied into the processing container. Further, the pressure in the processing container and the temperature of the wafer W in step S1 are also set to values within the range described in the embodiment.

In this evaluation test 1, the process was performed by changing the supply time of the processing gas ( _F2 gas and _NH3 gas) in one step S1 and the number of repetitions of steps S1 and S2 for each wafer W. For each processed wafer W, an image of the surface of the Si film 11 was obtained, and an etching selectivity (=etching amount of Si film 11/etching amount of SiGe film 12) was calculated. As evaluation test 1-1, the process gas supply time was set to 30 seconds, and the number of repetitions was set to 6 times. As evaluation test 1-2, the process gas supply time was set to 45 seconds, and the number of repetitions was set to 4 times. As evaluation test 1-3, the processing gas supply time was set to 60 seconds, and the number of repetitions was set to 3 times. Therefore, in each of the evaluation tests 1-1 to 1-3, the total time for supplying the processing gas to the wafer W was 180 seconds.

In evaluation tests 1-1 to 1-3, the etching selectivity was 30 or more, and therefore the Si film 11 was selectively etched with respect to the SiGe film 12. FIG. FIG. 12 schematically shows images obtained in evaluation tests 1-1 to 1-3 and an image obtained from the Si film 11 before processing. In the obtained image, unevenness on the surface of the Si film 11 is shown as black and white contrast. In the image shown in FIG. 12, the recessed portions of the unevenness are surrounded and shown with dots. showing. As shown in FIG. 12, formation of unevenness was confirmed in the image of the evaluation test 1-1. However, only slight unevenness was formed in Evaluation Tests 1-2 and 1-3.

In this way, the roughness of the surface of the Si film 11 is suppressed in the evaluation tests 1-2 and 1-3 in which the process gas supply time is relatively long in one step S1. This is because in evaluation test 1-1, the reaction between the processing gas and the surface layer of the Si film 11 is insufficient, and the sublimation in step S2 is performed in a state in which the thickness uniformity of the AFS layer 13 is low. On the other hand, in evaluation tests 1-2 and 1-3, the surface layer of the Si film 11 sufficiently reacted with the processing gas, and the AFS layer 13 was formed with a highly uniform thickness as described in the embodiment. It is considered to be a thing.

In the evaluation test 1-2 in which the supply time was 45 seconds, the surface roughness was sufficiently suppressed, and it is considered that this roughness could be suppressed even if the supply time was slightly shorter than 45 seconds. However, some roughness is observed in the evaluation test 1-1 in which the processing gas supply time is 30 seconds. From the above, it is considered that the supply time of the processing gas is preferably 40 seconds or longer. However, if the processing gas supply time is too long, the processing gas is blocked by the formed AFS layer 13 and cannot act on the Si film 11, resulting in wasteful consumption of the processing gas. Considering that the processing gas supply time is 60 seconds and the roughness of the Si film 11 is appropriately suppressed, it is considered preferable to set the supply time to a longer supply time or less, for example, 120 seconds or less.

・Evaluation test 2
Next, evaluation test 2 will be described. In this evaluation test 2, steps S1 and S2 were repeatedly performed on a plurality of wafers W in the same manner as in evaluation test 1, thereby etching the Si film 11 . Then, an image of the surface of the Si film 11 was acquired and an etching selectivity was calculated. In this evaluation test 2, the process gas supply time in one step S1 was set to 30 seconds for each wafer W, and steps S1 and S2 were repeated six times for each wafer W. Therefore, the processing gas supply time for one time and the number of repetitions of S1 and S2 are the same as in the evaluation test 1-1. However, the flow rate of NH ₃ gas is different from Evaluation Test 1-1. Regarding the flow rate of the NH ₃ gas in this evaluation test 2 (2-1, 2-2), there is a relationship of evaluation test 2-1<evaluation test 1-1<evaluation test 2-2. In Evaluation Test 2, the processing conditions other than the flow rate of NH ₃ gas were set to be the same as those in Evaluation Test 1.

The etching selectivity of Evaluation Tests 2-1 and 2-2 was 30 or more, and therefore the Si film 11 was selectively etched with respect to the SiGe film 12. FIG. FIG. 13 schematically shows the images obtained in Evaluation Tests 2-1 and 2-2, similarly to Evaluation Test 1. FIG. 13 also shows a schematic diagram of the image of the evaluation test 1-1 shown in FIG. 12 in order to facilitate understanding of the test results. As shown in FIG. 13, evaluation test 2-1 has greater roughness than evaluation test 1-1, and evaluation test 2-2 suppresses roughness. Therefore, the roughness is suppressed as the flow rate of the NH ₃ gas increases. This is because the F ₂ gas is supplied at a relatively large flow rate, so the higher the flow rate of the NH ₃ gas, the more the surface layer of the Si film 11 is transformed into the AFS layer 13 . This is believed to be due to the increased thickness uniformity of the layer 13 .

In evaluation test 1-1, the ratio of the flow rate of NH ₃ gas to the flow rate of F ₂ gas (flow rate of NH ₃ gas/flow rate of F ₂ gas) was 0.026. As described above, since some unevenness was observed in the evaluation test 1-1, it was confirmed that it is preferable to set the ratio to be larger than 0.026. In the evaluation test 2-2, the NH ₃ gas was set to a value within the range described in the embodiment, and the flow rate of NH ₃ gas/flow rate of F ₂ gas was 0.036. Therefore, it was confirmed that setting the ratio to 0.036 or more is more preferable.

・Evaluation test 3
Next, evaluation test 3 will be described. A plurality of wafers W on which the structures 71 described with reference to FIGS. 6 and 7 are formed are processed by repeating the cycle of steps T1 to T5 described in the second embodiment ten times. The flow rate of the HF gas supplied into the processing container 41 in step T3 was changed for each wafer W to be processed. An image of the processed wafer W was obtained by SEM, and the state of the surface of the Si film 74 in the structure 71 was observed. Evaluation Tests 3-1, 3-2, and 3-3 were performed by setting the flow rate of the HF gas to 100 sccm, 200 sccm, and 450 sccm, respectively.

The pressure inside the processing vessel 41 was set to a value within the range described in the embodiment, and the supply time of the HF gas was set to 30 seconds. In addition, the flow rate of Ar gas and the flow rate of N ₂ gas supplied into the processing chamber 41 together with the HF gas were each set to 275 sccm. In addition, as evaluation test 3-4, processing was performed under the same conditions as in evaluation tests 3-1 to 3-3 except that step T3 and step T4 (purging with N ₂ gas after HF gas supply) were not performed. Images were acquired by SEM. Therefore, the process in this evaluation test 3-4 is a process of repeating steps S1 and S2 described in the first embodiment.

Schematic diagrams of images obtained in evaluation tests 3-1, 3-2, and 3-4 are shown in the upper, middle, and lower stages of FIG. Compared to Evaluation Test 3-4, the roughness of the surface of the Si film 74 was suppressed in Evaluation Tests 3-1 to 3-3. Therefore, it was shown that it is preferable to supply HF gas as described in the second embodiment. Among Evaluation Tests 3-1 to 3-3, the above roughness was suppressed more in Evaluation Tests 3-2 and 3-3 than in Evaluation Test 3-1, which was at a practically desirable level. In addition, since the state of roughness was the same in evaluation tests 3-2 and 3-3, only the schematic diagram of 3-2 of these evaluation tests 3-2 and 3-3 is shown in FIG. .

From the above results, it was confirmed that the flow rate of the HF gas supplied to the wafer W in step T3 is preferably greater than 100 sccm, and more preferably greater than 200 sccm. As described above, 250 sccm of Ar gas and N ₂ gas, which are inert gases, are supplied during the supply of HF gas. Therefore, the ratio of the flow rate of the HF gas to the flow rate of all the gases supplied into the processing chamber 41 is expressed by Equation 2 below. Note that X in Equation 2 is the flow rate of HF gas.
Xsccm/(X+250+250)sccm Expression 2

It is 0.1667 from Equation 2 when X=100 sccm, and 0.2857 from Equation 2 when X=200 sccm. Therefore, from this evaluation test 3, it is preferable that the ratio of the flow rate of the HF gas to the flow rate of all the gases supplied into the processing container 41 is greater than 0.1667, and more preferably 0.2857 or more. I understand. The reason why the roughness was the same between the evaluation tests 3-2 and 3-3 is that the fluorine in the AFS layer 13 modifies the Si film 74, thereby improving the roughness. However, even if the flow rate of the HF gas is increased, the amount of fluorine that can contribute to the deterioration of the Si film 74 in the AFS layer 13 is limited.

・Evaluation test 4
Next, evaluation test 4 will be described. In evaluation test 4, the wafer W on which the structures 71 were formed was processed by repeating the cycle of steps T1, T2, and T5 in the second embodiment nine times. Then, after performing the processing as described above, an SEM image of the structure 71 is acquired, and the amount of etching near the opening of the recess 73 and the amount of etching near the back (near the end opposite to the opening) are calculated. was measured. Note that the smaller the difference between these etching amounts, the better. The flow rate of the NH ₃ gas supplied into the processing container 41 in step S1 is changed for each wafer W, and set to any one of 5 sccm, 8 sccm, 10 sccm, 12 sccm, and 14 sccm.

Another processing condition of step _S1 will be described. The flow rate of the _N2 gas was changed according to the flow rate _{of the NH3 gas, and the flow rate of the N2 gas was set so that the total flow rate of the N2 gas and the NH3 gas was 700} sccm. . The supply time of _F2 gas and _NH3 gas in one cycle was set to 15 seconds. Also, the temperature of the wafer W was set to a value within the range described in the embodiment.

FIG. 15 is a graph summarizing the results of Evaluation Test 4, in which the vertical axis and horizontal axis indicate the etching amount (unit: nm) and the flow rate of NH ₃ gas (unit: sccm), respectively. The vertical axis is scaled every 2 nm increase with respect to A, and A is a real number. As shown in the graph, when the NH ₃ gas flow rate is 5 sccm, the etching amount near the back is smaller than the etching amount near the opening, and these etching amounts are relatively large. When the flow rate of the NH ₃ gas is 8 sccm, the etching amount near the back is smaller than the etching amount near the opening. It is desirable that the difference between is even smaller.

When the flow rate of NH ₃ gas was 10 sccm or more, the difference in etching amount was sufficiently small. The reason for this result is that when the flow rate of the NH ₃ gas is 10 sccm or more, the NH ₃ gas is sufficiently supplied from the opening in the recess 73 to the back, so that the recess 73 is formed. This is probably because the AFS layer 13 was sufficiently formed on the surfaces of the upper and lower walls made of the Si film 74 .

As described above, in Evaluation Test 4, the F ₂ gas and the NH ₃ gas were supplied into the processing chamber 41 in parallel to etch _each portion of the concave portion 73 with high uniformity. As a result, it is preferable to increase it, and it is more preferable to set it to 10 sccm or more. F ₂ gas is supplied at 500 sccm as described above. Therefore, in this evaluation test 4, the ratio of the flow rate of _NH3 gas to the flow rate of _F2 gas is preferably greater than 8 sccm/500 sccm = 0.016, and more preferably 10 sccm/500 sccm = 0.02 or more. This is the result.

W wafer 11 Si film 13 AFS layer

Claims (16)

A first step of supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed thereon and having a first temperature to alter the surface of the silicon film to generate a reaction product. the process of
a second step of removing the reaction product by setting the substrate to a second temperature after the first step;
A substrate processing method comprising: 2. The substrate processing method according to claim 1, further comprising repeating the first step and the second step in order. 3. The substrate processing method according to claim 2, wherein said silicon film remains on said substrate when said repeating step is completed. 4. The substrate processing method according to claim 1, wherein said second temperature is higher than said first temperature. the substrate has a silicon-containing film different from the silicon film formed on its surface;
5. The substrate processing according to claim 1, wherein said first step and said second step are steps of selectively altering and removing said silicon film with respect to said silicon-containing film. Method. 6. The substrate processing method according to claim 5, wherein said silicon-containing film is a SiGe film. The substrate processing method according to any one of claims 1 to 6, wherein the first temperature is -20°C to 60°C. 8. The substrate processing method according to claim 1, wherein in said first step, said halogen-containing gas and said basic gas are simultaneously supplied to said substrate. 9. The substrate processing method according to claim 8, wherein in said first step, said halogen-containing gas and said basic gas are simultaneously supplied to said substrate for 40 seconds or longer. 10. The substrate processing method according to claim 1, wherein said halogen-containing gas is fluorine gas, and said basic gas is ammonia gas. In the first step,
supplying the fluorine gas into a processing container that stores the substrate and supplying the fluorine gas into the processing container are performed in parallel,
11. The substrate processing method according to claim 10, wherein a ratio of a flow rate of ammonia gas supplied into said processing chamber to a flow rate of fluorine gas supplied into said processing chamber is greater than 0.16. The first step is
a first supply step of simultaneously supplying the halogen-containing gas to the substrate and supplying the basic gas to the substrate;
a second supply step of supplying only one of the halogen-containing gas and the basic gas to the substrate after the first supply step;
The substrate processing method according to any one of claims 1 to 11, comprising: The halogen-containing gas is
a first fluorine-containing gas supplied to the substrate in the first supply step;
a second fluorine-containing gas supplied to the substrate in the second supply step;
13. The substrate processing method according to claim 12, wherein the first fluorine-containing gas and the second fluorine-containing gas are of different types. the first fluorine-containing gas is fluorine gas;
14. The substrate processing method according to claim 13, wherein said second fluorine-containing gas is hydrogen fluoride gas. supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed thereon to alter the surface of the silicon film to generate a reaction product;
then, supplying the processing gas to the substrate while the reaction product remains on the silicon film;
subsequently removing the reaction product;
A substrate processing method comprising: a processing container for storing a substrate having a silicon film formed on its surface;
a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and a basic gas into the processing container;
a first step in which the surface of the silicon film is altered by the processing gas to generate a reaction product, and the processing gas is supplied in a state in which the reaction product remains on the silicon film; a control unit that outputs a control signal so that after the step, a second step of removing the reaction product is performed;
A substrate processing apparatus comprising:

Images