Etching method and etching apparatus

Abstract

To provide an etching method and an etching apparatus capable of enhancing a selective ratio of a silicon nitride film over a silicon oxide film or a polysilicon film.SOLUTION: An etching method is a method for selectively etching a first silicon film S1 of a substrate S including the first silicon film S1 and a second silicon film S2. The etching method includes: supplying a hydrogen fluoride gas to the substrate S while heating the substrate S so as to maintain a temperature of the substrate S at a predetermined temperature included in a range of a first temperature or higher and a second temperature or lower; and supplying an activated radical generated from a gas for radical generation to an etching target while heating the substrate S so as to maintain the temperature of the substrate S after the supply of the hydrogen fluoride gas at the predetermined temperature.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an etching method and an etching apparatus. [Background technology]

[0002] One example of a method for selectively etching a silicon nitride film on a wafer having adjacent silicon nitride and silicon oxide films includes the steps of supplying hydrogen fluoride gas to a processing space containing the wafer and supplying inert gas radicals to the processing space. The wafer temperature is maintained low during the steps of supplying fluorine gas and supplying inert gas radicals. In the etching method, hydrogen fluoride gas is first supplied to the wafer, causing hydrogen fluoride to be adsorbed onto the surface of the silicon nitride film. Subsequently, inert gas radicals are supplied to the wafer, which provides the wafer with energy equal to or greater than the activation energy of the etching reaction between hydrogen fluoride and silicon nitride. As a result, etching of the silicon nitride film proceeds (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-12759 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described etching method, the wafer temperature is maintained at a low temperature throughout the etching of the silicon nitride film. Therefore, ammonia generated by the etching reaction between hydrogen fluoride and silicon nitride is less likely to desorb from the wafer surface. As a result, hydrogen fluoride and ammonia are supplied to the silicon oxide film of the wafer along with the silicon nitride film, resulting in the etching of the silicon oxide film progressing. This problem is not limited to cases where the wafer includes both a silicon nitride film and a silicon oxide film, but is also common to cases where the wafer includes both a silicon nitride film and a polysilicon film. [Means for solving the problem]

[0005] An etching method for solving the above problem is a method for selectively etching a silicon nitride film among etching targets including a silicon nitride film and a silicon oxide film or a polysilicon film, the etching method including: supplying hydrogen fluoride gas to the etching target while heating the etching target so as to maintain the temperature of the etching target at a predetermined temperature that is equal to or higher than a first temperature and equal to or lower than a second temperature; and supplying active radicals generated from a radical generating gas to the etching target while heating the etching target so as to maintain the temperature of the etching target at the predetermined temperature after the hydrogen fluoride gas is supplied.

[0006] An etching apparatus for solving the above problems includes a vacuum chamber defining a processing space for accommodating an etching target including a silicon nitride film and a silicon oxide film or a polysilicon film, a heating unit for heating the etching target, a hydrogen fluoride gas supply unit for supplying hydrogen fluoride gas into the processing space, a radical supply unit for supplying active radicals generated from a gas containing oxygen atoms into the processing space, and a control unit for controlling the operation of the heating unit, the hydrogen fluoride gas supply unit, and the radical supply unit. The control unit controls the heating unit to heat the etching target so as to maintain the temperature at a predetermined temperature between a first temperature and a second temperature, and then controls the hydrogen fluoride gas supply unit to supply the hydrogen fluoride gas and the radical supply unit to supply the active radicals.

[0007] According to the above-described etching method and etching apparatus, hydrogen fluoride gas and active radicals are supplied to an etching target heated to a predetermined temperature, which reduces variations in the depth direction of hydrogen fluoride adsorption in the etching target. Furthermore, since hydrogen fluoride reacts with active radicals in an etching target heated to a predetermined temperature, ammonia, a by-product of etching a silicon nitride film, is easily desorbed from the etching target. This prevents a silicon oxide film or polysilicon film from being etched by an etchant generated from ammonia and hydrogen fluoride. As a result, it is possible to increase the selectivity of a silicon nitride film relative to a silicon oxide film or polysilicon film.

[0008] In the etching method, the first temperature may be 80°C, and the second temperature may be 400°C. According to the above etching method, the first temperature is 80° C., which enhances the effect of suppressing variations in the depth direction of hydrogen fluoride adsorption in the etching target. Furthermore, the second temperature is 400° C., which prevents the etching target from becoming difficult to adsorb hydrogen fluoride due to an excessively high temperature of the etching target.

[0009] In the etching method, supplying the hydrogen fluoride gas to the etching target may include setting a pressure of 500 Pa or higher in a processing space that accommodates the etching target and to which the hydrogen fluoride gas is supplied.

[0010] According to the above etching method, the pressure in the processing space is 500 Pa or more, so that hydrogen fluoride is easily adsorbed onto the etching target, and as a result, the silicon nitride film is easily etched.

[0011] In the etching method, the radical generating gas may be a gas containing oxygen atoms. According to the above etching method, it is possible to obtain active radicals that are difficult to inactivate and function as an oxidation source.

[0012] In the etching method, the gas containing oxygen atoms may be at least one selected from the group consisting of oxygen gas, a mixed gas of oxygen gas and hydrogen gas, and nitrogen oxide gas.

[0013] The etching method may further include supplying the radical generating gas to the etching target between supplying the hydrogen fluoride gas to the etching target and supplying the active radicals to the etching target.

[0014] According to the above etching method, at least a portion of unnecessary hydrogen fluoride located on the etching target can be removed from the etching target by the flow of the fluid generated by the radical generating gas.

[0015] In the above etching method, one cycle may include supplying the hydrogen fluoride gas to the etching target and supplying the active radicals to the etching target, and the etching method may include repeating a plurality of the cycles, and each cycle may include supplying an inert gas to the etching target after supplying the active radicals to the etching target.

[0016] According to the above etching method, the active radicals supplied to the etching target in the nth cycle are less likely to be present in the vicinity of the etching target at the start of the (n+1)th cycle, and therefore, when hydrogen fluoride gas is supplied in the (n+1)th cycle, etching of portions of the etching target other than the silicon nitride film is suppressed.

[0017] In the above etching method, the silicon nitride film may be a first silicon film, the silicon oxide film or the polysilicon film may be a second silicon film, the etching target may include a plurality of the first silicon films and a plurality of the second silicon films, the first silicon films and the second silicon films may be alternately stacked in the etching target, and the etching target may include a hole extending along a thickness direction, and the hole may penetrate two or more layers of the first silicon films and two or more layers of the second silicon films.

[0018] According to the above etching method, since the etching target is heated, hydrogen fluoride is easily supplied to the inside of the hole, and as a result, the silicon nitride film that defines the hole is also easily etched. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing the configuration of an etching apparatus. [Figure 2] FIG. 2 is a diagram showing the structure of an etching chamber included in the etching apparatus shown in FIG. [Figure 3]FIG. 3 is a timing chart for explaining the driving of each supply unit in the etching apparatus. [Figure 4] FIG. 4 is a process diagram for explaining one step included in the etching method. [Figure 5] FIG. 5 is a process diagram for explaining one step included in the etching method. [Figure 6] FIG. 6 is a process diagram for explaining one step included in the etching method. [Figure 7] FIG. 7 is a process diagram for explaining one step included in the etching method. [Figure 8] FIG. 8 is a graph showing the selectivity of a silicon nitride film to a silicon oxide film in a test example. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of an etching method and an etching apparatus will be described with reference to FIGS.

[0021] [Etching equipment] The etching apparatus will be described with reference to FIG. 1, the etching apparatus 10 includes an etching chamber 11, a load lock chamber 12, and a gate valve 13. The etching apparatus 10 includes an oxygen-containing gas supply unit 21, a hydrogen fluoride (HF) gas supply unit 22, a plasma supply unit 23, and an inert gas supply unit 24. The etching apparatus 10 includes a control unit 10C.

[0022] The etching chamber 11 is an example of a vacuum chamber. The etching chamber 11 defines a processing space 11S (see FIG. 2) that accommodates a substrate S (see FIG. 2), which is an example of an etching target. The substrate S includes a silicon nitride film and a silicon oxide film or a polysilicon film. The etching chamber 11 etches the silicon nitride film within the processing space 11S. The load lock chamber 12 loads the substrate S before etching into the etching chamber 11 from outside the etching apparatus 10. The load lock chamber 12 loads the substrate S after etching out of the etching chamber 11 to outside the etching apparatus 10.

[0023] The gate valve 13 is disposed between the etching chamber 11 and the load lock chamber 12. When the gate valve 13 is opened, the etching chamber 11 communicates with the load lock chamber 12. When the gate valve 13 is closed, the etching chamber 11 is isolated from the load lock chamber 12.

[0024] The load lock chamber 12 is connected to a cooling gas supply unit 12A. The cooling gas supply unit 12A supplies a cooling gas to the load lock chamber 12. The cooling gas is an inert gas for cooling the substrate S after etching.

[0025] The etching chamber 11 is equipped with a heating unit 11A and an exhaust unit 11B. The heating unit 11A heats the etching chamber 11, thereby heating the substrate S in the processing space 11S. The exhaust unit 11B depressurizes the etching chamber 11 to a predetermined pressure.

[0026] The etching chamber 11 is connected to an HF gas supply unit 22 and a plasma supply unit 23. The HF gas supply unit 22 supplies HF gas to the processing space 11S. The HF gas supply unit 22 is configured to be able to supply HF gas to the processing space 11S at a predetermined flow rate. The HF gas supply unit 22 is, for example, a mass flow controller.

[0027] The plasma supply unit 23 supplies plasma to the processing space 11S, thereby supplying active radicals contained in the plasma into the processing space 11S. The oxygen-containing gas supply unit 21 and the plasma supply unit 23 constitute an example of a radical supply unit.

[0028] The plasma supply unit 23 includes a discharge tube 23A, a waveguide 23B, and a microwave irradiation unit 23C. The microwave irradiation unit 23C irradiates microwaves to the discharge tube 23A through the waveguide 23B. The discharge tube 23A is connected to the oxygen-containing gas supply unit 21. The inner surface of the discharge tube 23A is made of an inorganic oxide. The inorganic oxide that forms the inner surface of the discharge tube 23A may be silicon oxide or aluminum oxide. The discharge tube 23A may be, for example, a quartz tube.

[0029] The oxygen-containing gas supply unit 21 supplies a gas containing oxygen atoms to the discharge tube 23A. The oxygen-containing gas supply unit 21 is configured to be able to supply the gas containing oxygen atoms to the discharge tube 23A at a predetermined flow rate. The oxygen-containing gas supply unit 21 is, for example, a mass flow controller.

[0030] The gas containing oxygen atoms is an example of a radical generating gas. The gas containing oxygen atoms includes oxygen gas, a mixed gas of oxygen gas and hydrogen gas, nitrogen oxide (N x O y The nitrogen oxide gas may be, for example, any one of nitric oxide (NO) gas, nitrogen dioxide (NO) gas, dinitrogen monoxide (NO) gas, dinitrogen trioxide (NO) gas, and dinitrogen pentoxide (NO) gas.

[0031] The plasma supply unit 23 generates plasma in the discharge tube 23 A by irradiating microwaves to the oxygen-containing gas in the discharge tube 23 A. The plasma contains oxygen-containing radicals.

[0032] The inert gas supply unit 24 supplies an inert gas to the processing space 11S. The inert gas supply unit 24 is configured to be able to supply the inert gas to the processing space 11S at a predetermined flow rate. The inert gas supply unit 24 is, for example, a mass flow controller. The inert gas may be, for example, nitrogen (N2) gas or argon (Ar) gas. The inert gas supply unit 24 may supply the inert gas to the processing space 11S using the same piping as the HF gas supply unit 22, or may supply the inert gas to the processing space 11S using a separate piping.

[0033] The control unit 10C includes a memory unit 10CM. The memory unit 10CM stores process conditions for etching a silicon nitride film. The process conditions include the pressure in the etching chamber 11, the temperature of the substrate S, the flow rates of various gases, and the output of the microwave irradiation unit 23C. The control unit 10C controls the operation of the heating unit 11A, the exhaust unit 11B, the oxygen-containing gas supply unit 21, the HF gas supply unit 22, the plasma supply unit 23, and the inert gas supply unit 24 so that the etching conditions match the process conditions.

[0034] The control unit 10C causes the heating unit 11A to heat the substrate S so as to maintain it at a predetermined temperature that is equal to or higher than the first temperature and equal to or lower than the second temperature, and then causes the HF gas supply unit 22 to supply HF gas, and then causes the radical supply unit to supply active radicals.

[0035] [Etching chamber] As shown in Figure 2, the etching chamber 11 accommodates a support 10A. The support 10A is capable of supporting a plurality of substrates S. The plurality of substrates S supported by the support 10A are stacked with gaps between adjacent substrates S. The substrates S include a silicon nitride film and a silicon oxide film or a polysilicon film. An example of the substrate S has a disk shape.

[0036] The etching chamber 11 is equipped with a shower head 11D. The shower head 11D is connected to a discharge tube 23A. The number of discharge tubes 23A connected to the shower head 11D may be one or more. Note that FIG. 2 shows an example in which two discharge tubes 23A are connected to the shower head 11D. The shower head 11D is equipped with a plurality of supply ports. The supply ports of the shower head 11D are aligned along the stacking direction of the substrates S. The supply ports of the shower head 11D supply plasma supplied from the discharge tube 23A toward the substrates S.

[0037] The etching chamber 11 includes a rotating unit 11E. The rotating unit 11E rotates the support unit 10A in the circumferential direction of the substrate S. The rotating unit 11E disperses the plasma supplied from the shower head 11D toward the substrate S and the HF gas supplied from the HF gas supply unit 22 toward the substrate S in the circumferential direction of the substrate S.

[0038] The etching chamber 11 is equipped with a temperature measurement unit 11F. The temperature measurement unit 11F measures the temperature inside the etching chamber 11 as the temperature of the substrate S. The temperature measurement unit 11F is connected to the control unit 10C. The temperature measurement results by the temperature measurement unit 11F are input to the control unit 10C. The control unit 10C controls the driving of the heating unit 11A based on the measurement results by the temperature measurement unit 11F.

[0039] 3 shows an example of an embodiment in which the control unit 10C drives the heating unit 11A, the oxygen-containing gas supply unit 21, the HF gas supply unit 22, the microwave irradiator 23C, and the inert gas supply unit 24. In FIG. 3, the state in which heating by the heating unit 11A is stopped is indicated as "OFF," and the state in which heating by the heating unit 11A is performed is indicated as "ON." In addition, the state in which microwave irradiation by the microwave irradiator 23C is stopped is indicated as "OFF," and the state in which microwave irradiation by the microwave irradiator 23C is performed is indicated as "ON."

[0040] Furthermore, the state in which the gas supply from each of the gas supply units 21, 22, 24 is stopped is indicated as "OFF", and the state in which the gas supply from each of the gas supply units 21, 22, 24 is being performed is indicated as "ON".

[0041] 3, when etching the substrate S in the etching chamber 11, first, at timing t1, the control unit 10C causes the heating unit 11A to start heating. As a result, the temperature T of the substrate S starts to rise, and at timing t2, the temperature T of the substrate S reaches a predetermined temperature in the range of not less than a first temperature and not more than a second temperature.

[0042] Thereafter, at timing t3, control unit 10C causes HF gas supply unit 22 to start supplying HF gas. Next, at timing t4, control unit 10C causes HF gas supply unit 22 to stop supplying HF gas and causes oxygen-containing gas supply unit 21 to start supplying oxygen-containing gas. Then, at timing t5, control unit 10C causes microwave irradiation unit 23C to start irradiating microwaves.

[0043] Subsequently, at timing t6, the control unit 10C causes the oxygen-containing gas supply unit 21 to stop supplying the oxygen-containing gas, causes the microwave irradiation unit 23C to stop irradiating the microwaves, and causes the inert gas supply unit 24 to start supplying the inert gas. Then, at timing t7, the control unit causes the inert gas supply unit 24 to stop supplying the inert gas.

[0044] Thus, among the processes that the control unit 10C causes the etching chamber 11 to perform, the process of heating the substrate S starts at timing t1, and heating of the substrate S continues until etching of the substrate S is completed. Furthermore, among the processes that the control unit 10C causes the etching chamber 11 to perform, the process from timing t3 to timing t4 is a process of supplying HF gas, and the process from timing t4 to timing t5 is a process of supplying an oxygen-containing gas. Furthermore, among the processes that the control unit 10C causes the etching chamber 11 to perform, the process from timing t5 to timing t6 is a process of supplying active radicals, and the process from timing t6 to timing t7 is a process of supplying an inert gas.

[0045] That is, the process from timing t3 to timing t7 constitutes one cycle. The control unit 10C causes the etching chamber 11 to perform multiple cycles until the amount of etching of the silicon nitride film on the substrate S reaches a predetermined amount. The number of cycles that the control unit 10C causes the etching chamber 11 to perform may be set in advance.

[0046] [Etching method] The etching method will be described with reference to FIGS. The etching method disclosed herein is a method for selectively etching a silicon nitride film among etching targets including a silicon nitride film and a silicon oxide film or a polysilicon film. The etching method includes supplying HF gas and, after the supply of HF gas, supplying active radicals. The supply of HF gas includes supplying hydrogen fluoride gas to the etching target while heating the etching target so as to maintain the temperature of the etching target at a predetermined temperature that is equal to or higher than a first temperature and equal to or lower than a second temperature. The supply of active radicals includes supplying active radicals generated from a radical generating gas to the etching target while heating the etching target so as to maintain the temperature of the etching target at the predetermined temperature after the supply of HF gas.

[0047] According to the etching method of the present disclosure, HF gas and active radicals are supplied to an etching target heated to a predetermined temperature, reducing variations in HF adsorption in the etching target along the depth direction. Furthermore, since HF reacts with active radicals in an etching target heated to a predetermined temperature, ammonia (NH3), a by-product of etching a silicon nitride film, is easily desorbed from the etching target. This prevents the silicon oxide film or polysilicon film from being etched by the etchant generated from HF and NH3. As a result, it is possible to increase the selectivity of a silicon nitride film relative to a silicon oxide film or polysilicon film. The etching method will be described in more detail below with reference to FIGS. 4 to 7.

[0048] As shown in FIG. 4, an example of a substrate S may have a multilayer film. A silicon nitride film is the first silicon film S1. A silicon oxide film or a polysilicon film is the second silicon film S2. The substrate S, which is an example of an etching target, includes multiple first silicon films S1 and multiple second silicon films S2. In the substrate S, the first silicon films S1 and the second silicon films S2 are alternately stacked. The substrate S includes a support substrate S3. The multilayer film including the first silicon film S1 and the second silicon film S2 is formed on the support substrate S3.

[0049] The substrate S includes a hole SA extending in the thickness direction. The hole SA penetrates two or more first silicon films S1 and two or more second silicon films S2. Although only one hole SA is shown in FIGS. 4 to 7 for convenience of illustration, the substrate S has a plurality of holes SA. The substrate S may be, for example, a substrate for 3D NAND.

[0050] In the etching method, first, HF gas is supplied to the substrate S heated to a first temperature. As a result, the HF gas supplied to the substrate S is also supplied to the hole SA. In the etching method of the present disclosure, since the substrate S is heated when HF 31 is supplied, HF 31 is easily supplied to the inside of the hole SA. As a result, the first silicon film S1, which is a silicon nitride film that defines the hole SA, is also easily etched.

[0051] HF31 has a high adsorptivity to the substrate S. Therefore, the amount of HF31 adsorbed near the opening of the hole SA is likely to be greater than the amount of HF31 adsorbed at the bottom of the hole SA. In this regard, by heating the substrate S to the first temperature or higher, the HF31 supplied to the substrate S is less likely to be consumed near the opening of the hole SA, and as a result, HF31 is more likely to be introduced also at the bottom of the hole SA.

[0052] The first temperature may be 80°C, and the second temperature may be 400°C. Because the first temperature is 80°C, the effect of suppressing the variation in the adsorption of HF31 in the depth direction in the substrate S is enhanced. That is, energy is imparted to the HF31 adsorbed on the surface of the substrate S, and therefore the amount of HF31 adsorbed on the substrate S near the opening of the hole SA is prevented from becoming excessive. Moreover, because the second temperature is 400°C, the temperature of the substrate S is prevented from becoming excessively high, and thus, it is prevented that HF31 becomes less likely to be adsorbed on the substrate S. Note that, from the viewpoint of further suppressing the variation in the adsorption of HF31 on the substrate S, the first temperature may be 100°C, 120°C, or 140°C.

[0053] In the step of supplying HF gas to the substrate S, the pressure in the processing space 11S, which accommodates the substrate S and to which the HF gas is supplied, may be 500 Pa or more. When the pressure in the processing space 11S is 500 Pa or more, HF 31 is more likely to be adsorbed to the substrate S, and as a result, the first silicon film S1 is more likely to be etched.

[0054] As shown in FIG. 5, after HF gas is supplied to the substrate S, the HF gas is switched to a radical generating gas. As described above, the radical generating gas may be a gas containing oxygen atoms. This makes it possible to obtain active radicals that are difficult to inactivate and function as an oxidation source. As described above, the gas containing oxygen atoms may be O2 gas, a mixed gas of O2 gas and H2 gas, or N x O y The gas may be at least one selected from the group consisting of:

[0055] The gas containing oxygen atoms may be, for example, O2 gas. When O2 gas is supplied to the substrate S, the affinity of O232 to the second silicon film S2 is higher than the affinity of HF31, so HF31 adsorbed to the second silicon film S2 defining the hole SA is replaced by O232. However, because O232 has low adsorption, O232 is unlikely to remain on the second silicon film S2.

[0056] It should be noted that if a radical generating gas is supplied to the substrate S between the supply of HF gas to the substrate S and the supply of active radicals to the substrate S, at least a portion of the unnecessary HF 31 located on the substrate S can be removed from the substrate S by the flow of fluid generated by the radical generating gas.

[0057] 6, active radicals 33 generated from the radical generating gas are supplied to the substrate S. As a result, an etchant 34 that etches the first silicon film S1 is generated from the HF 31 adsorbed on the first silicon film S1 that defines the hole SA and the active radicals 33. In this way, the surface reaction between the HF 31 and the active radicals 33 progresses on the substrate S, and the first silicon film S1 is etched. Etching of the first silicon film S1 progresses in a direction perpendicular to the depth direction of the hole SA.

[0058] When the radical generating gas is O2 gas, the active radicals 33 are particularly difficult to inactivate, and therefore the active radicals 33 are easily supplied to the interior of the hole SA. This makes it possible to proceed with etching of the first silicon film S1 even inside the hole SA. Furthermore, when the second silicon film S2 is a silicon oxide film and the active radicals 33 are generated from a gas containing oxygen atoms, it is possible to repair the surface of the second silicon film S2 with the active radicals 33. This further increases the selectivity of the first silicon film S1 to the second silicon film S2.

[0059] 7, after the active radicals 33 are supplied to the substrate S, the active radicals 33 are switched to an inert gas. The inert gas may be, for example, N2 gas, as described above. As described above, in the etching method, one cycle includes supplying HF gas to the substrate S and supplying active radicals 33 to the substrate S. The etching method may include repeating a plurality of cycles. A cycle includes supplying an inert gas to the substrate S after supplying active radicals 33 to the substrate S.

[0060] As a result, the active radicals supplied to the etching target in the nth cycle are less likely to be present in the vicinity of the substrate S at the start of the (n+1)th cycle. Therefore, when HF gas is supplied in the (n+1)th cycle, etching of portions of the substrate S other than the first silicon film S1 is suppressed.

[0061] By supplying nitrogen gas to the substrate S, nitrogen 35 is supplied into the holes SA, and as a result, the HF 31, the active radicals 33, and the etchant 34 remaining in the holes SA are replaced with nitrogen 35.

[0062] When etching of the substrate S is repeated multiple times, the temperature of the substrate S is maintained at a predetermined value between the first temperature and the second temperature from the first cycle to the end of the final cycle.

[0063] [Test example] A test example will be described with reference to FIG. [Test Example 1] A first silicon substrate having a silicon nitride film formed thereon and a second silicon substrate having a silicon oxide film formed thereon were prepared. The HF gas supplying process, oxygen gas supplying process, oxygen radical supplying process, and nitrogen gas supplying process were carried out under the following conditions. The first silicon substrate and the second silicon substrate were etched by repeating a cycle including these four processes 400 times. The temperature of each substrate was set to 120°C.

[0064] [HF gas supply process] HF gas flow rate: 5000sccm Processing space pressure 3500Pa ·Supply time 30 seconds

[0065] [Oxygen gas supply process] Oxygen gas flow rate: 5500sccm Processing space pressure 500Pa ·Supply time 6 seconds

[0066] [Active radical supply process] Oxygen gas flow rate: 5500sccm Processing space pressure 500Pa ·Supply time 1 second Microwave irradiation intensity: 2800W

[0067] [Inert gas supply process] Nitrogen gas flow rate: 60,000 sccm Processing space pressure 60Pa ·Supply time 6 seconds

[0068] [Test Example 2] Each substrate was etched in the same manner as in Test Example 1, except that the temperature of each substrate was set to 140°C.

[0069] [Test Example 3] Each substrate was etched in the same manner as in Test Example 1, except that the temperature of each substrate was set to 150°C.

[0070] [Test Example 4] Each substrate was etched in the same manner as in Test Example 1, except that the temperature of each substrate was set to 160°C.

[0071] [Test Example 5] Each substrate was etched in the same manner as in Test Example 1, except that the temperature of each substrate was set to 170°C.

[0072] [Evaluation method] In each test example, the thickness of the silicon nitride film on the first substrate and the thickness of the silicon oxide film on the second substrate before etching were measured using an ellipsometer (RE-3500, manufactured by SCREEN Holdings Co., Ltd.). In addition, the thickness of the silicon nitride film on the first substrate and the thickness of the silicon oxide film on the second substrate after etching were measured using the same ellipsometer (same as above).

[0073] The etching amount of the silicon nitride film was calculated by subtracting the thickness of the silicon nitride film after etching from the thickness of the silicon nitride film before etching, and the etching amount of the silicon oxide film was calculated by subtracting the thickness of the silicon oxide film after etching from the thickness of the silicon nitride film before etching.

[0074] For each test example, the etching amount of the silicon nitride film was divided by the etching amount of the silicon oxide film to calculate the selectivity of the silicon nitride film to the silicon oxide film.

[0075] [Evaluation results] 8, it was confirmed that the selectivity of Test Example 1 was 0, the selectivity of Test Example 2 was 18, the selectivity of Test Example 3 was 25, the selectivity of Test Example 4 was 42, and the selectivity of Test Example 5 was 63. As such, it was confirmed that the selectivity of the silicon nitride film relative to the silicon oxide film was significantly increased by setting the substrate temperature to 140° C. or higher.

[0076] As described above, according to one embodiment of the etching method and etching apparatus, the following effects can be obtained. (1) Since HF gas and active radicals are supplied to the substrate S heated to a predetermined temperature, variations in the adsorption of HF31 on the substrate S are less likely to occur. Furthermore, since HF31 reacts with active radicals 33 on the substrate S heated to a predetermined temperature, NH3, a by-product produced when the first silicon film S1 is etched, is more likely to be desorbed from the substrate S. This prevents the second silicon film S2 from being etched by the etchant generated from HF31 and NH3. As a result, it is possible to increase the selectivity of the first silicon film S1 to the second silicon film S2.

[0077] (2) When the first temperature is 80°C, it is possible to more reliably suppress variations in the adsorption of HF on the substrate S. Furthermore, when the second temperature is 400°C, it is possible to prevent the temperature of the substrate S from becoming excessively high, thereby preventing the substrate S from being easily adsorbed with HF 31.

[0078] (3) When the pressure in the processing space 11S is 500 Pa or higher, the HF 31 is more likely to be adsorbed onto the substrate S, and as a result, the first silicon film S1 is more likely to be etched. (4) When the radical generating gas contains oxygen, it is possible to obtain active radicals 33 that are difficult to inactivate and function as an oxidation source.

[0079] (5) When the etching method includes a radical generating gas supply step, at least a portion of the unnecessary HF located on the substrate S can be removed from the substrate S by the flow of the fluid generated by the radical generating gas.

[0080] (6) When the etching method includes an inert gas supply step, the active radicals 33 supplied to the substrate S in the nth cycle are less likely to be present in the vicinity of the substrate S at the start of the (n+1)th cycle. Therefore, when HF gas is supplied in the (n+1)th cycle, etching of portions of the substrate S other than the first silicon film S1 is suppressed.

[0081] (7) Even when the substrate S has a hole SA, the substrate S is heated, so that HF ​​is easily supplied to the inside of the hole SA, which makes it easier to etch the first silicon film S1 that defines the hole SA.

[0082] The above-described embodiment can be modified as follows. [Etching method] A cycle included in the etching method does not have to include at least one of the radical generating gas supply step and the inert gas supply step. That is, a cycle only needs to include at least the HF gas supply step and the active radical supply step. Even in this case, the effect equivalent to the above-mentioned (1) can be obtained.

[0083] [Radical generating gas] The radical-generating gas does not need to contain oxygen atoms. The radical-generating gas may be, for example, an inert gas. The inert gas may be, for example, Ar gas.

[0084] [substrate] The substrate S may have a first silicon film S1 and a second silicon film S2 on the same surface. Even in this case, the effect equivalent to the above-mentioned (1) can be obtained. [Explanation of symbols]

[0085] 10...Etching equipment 10C...Control unit 11...Etching chamber 11S...Processing space 11A…Heating part 21...Oxygen-containing gas supply unit 22...Hydrogen fluoride gas supply unit 23...Plasma supply unit 24...Inert gas supply section 31...Hydrogen fluoride 32...Oxygen 33... Active radicals 34...Etchant 35...Nitrogen S...Substrate S1: First silicon film S2: Second silicon film

Claims

1. A method for selectively etching a silicon nitride film among etching targets including a silicon nitride film, a silicon oxide film, and a polysilicon film, comprising: supplying hydrogen fluoride gas to the etching object while heating the etching object so as to maintain the temperature of the etching object at a predetermined temperature included in the range of a first temperature to a second temperature; supplying active radicals generated from a radical generating gas to the etching target while heating the etching target so as to maintain the temperature of the etching target at the predetermined temperature after the hydrogen fluoride gas is supplied. Etching method.

2. the first temperature is 80°C; The second temperature is 400°C. The etching method according to claim 1 .

3. supplying the hydrogen fluoride gas to the etching target, The pressure in the processing space in which the etching target is accommodated and to which the hydrogen fluoride gas is supplied is 500 Pa or more. The etching method according to claim 1 or 2.

4. The radical generating gas is a gas containing oxygen atoms. The etching method according to claim 1 or 2.

5. The gas containing oxygen atoms is at least one selected from the group consisting of oxygen gas, a mixed gas of oxygen gas and hydrogen gas, and nitrogen oxide gas. The etching method according to claim 4.

6. supplying the radical generating gas to the etching target between supplying the hydrogen fluoride gas to the etching target and supplying the active radicals to the etching target. The etching method according to claim 1 or 2.

7. One cycle includes supplying the hydrogen fluoride gas to the etching target and supplying the activated radicals to the etching target, The etching method includes repeating the cycle a plurality of times, The cycle includes supplying the active radicals to the etching target and then supplying an inert gas to the etching target. The etching method according to claim 1 or 2.

8. the silicon nitride film is a first silicon film, the silicon oxide film or the polysilicon film is a second silicon film, the etching target includes a plurality of the first silicon films and a plurality of the second silicon films, the first silicon film and the second silicon film are alternately stacked in the etching target, the etching target includes a hole extending along a thickness direction, The hole penetrates two or more layers of the first silicon film and two or more layers of the second silicon film. The etching method according to claim 1 or 2.

9. a vacuum chamber defining a processing space for accommodating an etching target including a silicon nitride film and a silicon oxide film or a polysilicon film; a heating unit that heats the etching target; a hydrogen fluoride gas supply unit that supplies hydrogen fluoride gas into the processing space; a radical supply unit that supplies active radicals generated from a gas containing oxygen atoms into the processing space; a control unit that controls driving of the heating unit, the hydrogen fluoride gas supply unit, and the radical supply unit, The control unit controls the heating unit to heat the etching target so as to maintain the target at a predetermined temperature in the range of a first temperature to a second temperature, and then controls the hydrogen fluoride gas supply unit to supply the hydrogen fluoride gas, and then controls the radical supply unit to supply the active radicals. Etching equipment.

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