Method for manufacturing semiconductor device

Abstract

To provide a method for manufacturing a semiconductor device including an etching method having a higher etching rate.SOLUTION: With a method for manufacturing a semiconductor device, a surface layer is formed on an inner bottom surface of a recess formed on a surface of a workpiece cooled to temperature of 0°C or lower by introducing a first gas containing alcohol or a second gas containing the first gas and a halogen element, a second gas or a third gas containing a rare gas element is introduced, first plasma is generated from the second gas or the third gas, an inner bottom surface is processed by etching using the first plasma, and formation of the surface layer and processing of the inner bottom surface are alternately switched.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a method for manufacturing a semiconductor device. [Background technology]

[0002] BACKGROUND ART In a method for manufacturing a semiconductor device such as a three-dimensional memory, a technique is known in which a recess or an opening is formed in an object to be processed by etching using an etching gas containing a fluorinated hydrocarbon compound. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-019185 [Patent Document 2] International Publication No. 2018 / 220973 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a method for manufacturing a semiconductor device that includes an etching method having a higher etching rate. [Means for solving the problem]

[0005] A method for manufacturing a semiconductor device according to an embodiment includes: introducing a first gas containing alcohol or the first gas and a second gas containing a halogen element to form a surface layer on the inner bottom surface of a recess formed in the surface of an object to be processed that has been cooled to a temperature of 0°C or below; introducing a second gas or a third gas containing a rare gas element; generating a first plasma from the second gas or the third gas; processing the inner bottom surface by etching using the first plasma; and alternating between forming the surface layer and processing the inner bottom surface. [Brief explanation of the drawings]

[0006] [Figure 1] 4 is a flowchart illustrating an example of a method for manufacturing the semiconductor device according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating a structural example of an object to be processed. [Figure 3] FIG. 1 is a schematic diagram showing a configuration example of a semiconductor manufacturing apparatus. [Figure 4] 4 is a timing chart for explaining an example of an etching method according to the first embodiment. [Figure 5] FIG. 10 is a cross-sectional view illustrating the alcohol-containing gas introducing step (S2-1). [Figure 6] 10A and 10B are schematic cross-sectional views for explaining differences in the shape of a surface layer due to differences in the state of gas supplied to an object to be processed. [Figure 7] 10A and 10B are schematic cross-sectional views for explaining differences in the shape of a surface layer due to differences in the state of gas supplied to an object to be processed. [Figure 8] FIG. 10 is a cross-sectional view illustrating the etching step (S2-2). [Figure 9] FIG. 10 is a cross-sectional view illustrating a memory layer forming step. [Figure 10] 10 is a flowchart for explaining a modified example of the method for manufacturing the semiconductor device according to the first embodiment. [Figure 11] 6 is a timing chart for explaining an example of an etching method according to a modified example of the first embodiment. [Figure 12] 10 is a flowchart illustrating an example of a method for manufacturing a semiconductor device according to a second embodiment. [Figure 13] 10 is a timing chart for explaining an example of an etching method according to the second embodiment. [Figure 14] 10 is a flowchart illustrating an example of a method for manufacturing a semiconductor device according to a third embodiment. [Figure 15] FIG. 10 is a cross-sectional view illustrating the hydrophobic film forming step (S2-5) in the third embodiment. [Figure 16]FIG. 10 is a cross-sectional view illustrating the hydrophilization step (S2-6) in the third embodiment. [Figure 17] FIG. 10 is a cross-sectional view illustrating an etching step (S2-2) in the third embodiment. [Figure 18] 10 is a flowchart illustrating an example of a method for manufacturing a semiconductor device according to a fourth embodiment. [Figure 19] 10A to 10C are cross-sectional views illustrating an example of a method for manufacturing a semiconductor device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments will be described with reference to the drawings. The relationship between the thickness and planar dimensions of each component, the thickness ratio of each component, etc. shown in the drawings may differ from the actual product. Furthermore, in the embodiments, substantially identical components are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0008] First Embodiment 1 is a flowchart illustrating an example of a method for manufacturing a semiconductor device according to the first embodiment. The semiconductor device is, for example, a three-dimensional memory. The example of the method for manufacturing the semiconductor device includes a preparation step (S1), an etching step (S2), and a memory layer formation step (S3).

[0009] [Preparation process] In the preparation step, a workpiece to be etched in the etching step is prepared. FIG. 2 is a cross-sectional schematic diagram showing an example structure of the workpiece. FIG. 2 shows the X-axis, Y-axis, and Z-axis. The X-axis, Y-axis, and Z-axis are perpendicular to one another. FIG. 2 shows a part of the XZ cross section of the workpiece 10. The Z-axis is along the thickness direction of the workpiece 10.

[0010] The workpiece 10 includes a substrate 101, an underlayer 102 provided on the substrate 101, a stack having first layers 103 and second layers 104 alternately stacked on the underlayer 102, a mask layer 106 provided on the stack, and a recess H having an inner wall surface HA and an inner bottom surface HB that penetrates the mask layer 106 and exposes a portion of the stack. The underlayer 102, the first layer 103, the second layer 104, and the mask layer 106 are examples of a film to be processed provided on the substrate 101, and the film to be processed is not limited to the above configuration.

[0011] The substrate 101 may be, for example, a semiconductor substrate such as a silicon substrate or a silicon carbide substrate, an insulating substrate such as a glass substrate, a quartz substrate or a sapphire substrate, or a compound semiconductor substrate such as a GaAs substrate.

[0012] The base layer 102 can be, for example, an insulating film such as a silicon oxide film or a silicon nitride film, or a conductive layer between insulating films. The base layer 102 is not necessarily provided, but in that case, the first layer 103 is formed on the substrate 101. The first layer 103 may also be formed on the base layer 102.

[0013] The first layer 103 is a sacrificial layer. The sacrificial layer is a region where a conductive layer will be formed later. The first layer 103 may be, for example, a silicon nitride film.

[0014] The second layer 104 may be, for example, a silicon oxide film.

[0015] The mask layer 106 functions as a mask for etching a portion of the stacked layers. For example, an organic hard mask or the like can be used as the mask layer 106. Note that the mask layer 106 may be removed after etching a portion of the stacked layers.

[0016] The recess H is formed in the surface of the workpiece. The recess H extends in the Z-axis direction. Examples of the XY plane shape of the recess H include a circular shape, a polygonal shape, etc. The inner bottom surface HB is formed on the surface of the first layer 103 or the surface of the second layer 104.

[0017] [Etching process] (etching equipment) 3 is a schematic diagram showing an example of the configuration of a semiconductor manufacturing apparatus (etching apparatus) that can be used in the etching process. The etching apparatus 1 includes a processing chamber 2, an electrode 3, an electrode 4, a gas supply unit 5, a gas exhaust unit 6, a cooling unit 7, a power supply unit 8, and a control unit 9.

[0018] The processing chamber 2 is a space in which the workpiece 10 can be etched using plasma (plasma etching). The processing chamber 2 may have a door (gate) for carrying in and out the workpiece 10.

[0019] The electrode 3 is a lower electrode and functions as a mounting table for placing the workpiece 10. The electrode 3 has a surface 3a that is a mounting surface for the workpiece 10. The etching apparatus 1 may also have an electrostatic chuck for holding the workpiece 10.

[0020] The electrode 4 is an upper electrode. The electrode 4 has a surface 4a and an opening 4b for introducing a gas into the processing chamber 2 through the electrode 4. The opening 4b has a plurality of inlets on the surface 4a.

[0021] The gas supply unit 5 includes, for example, a gas supply source 51 that supplies a first gas, a gas supply source 52 that supplies a second gas, a gas supply source 53 that supplies a third gas, a gas supply source 54 that supplies a fourth gas, and a gas supply source 55 that supplies a fifth gas. The first to fifth gases are different from one another. Each of the gas supply sources 51 to 55 is connected to the processing chamber 2. The gas supply unit 5 further includes a flow rate adjustment unit 56 that includes multiple mass flow controllers, and the flow rates of the first to fifth gases can be controlled by the corresponding mass flow controllers. Examples of the gas supply sources 51 to 55 include a cylinder cabinet, etc. The gas supply unit 5 supplies gases from the gas supply sources 51 to 55 to the processing chamber 2.

[0022] The first gas is a gas containing alcohol. Alcohol can form a liquid phase region at a pressure lower than the pressure of the liquid phase region of the second gas and at a temperature higher than the temperature of the liquid phase region of the second gas. Furthermore, alcohol has a liquid phase region at a lower pressure and temperature than water (H2O). Examples of alcohol include methanol and ethanol. Methanol and ethanol are preferable because they have a liquid phase region at a pressure of 1 Pa to 10 Pa and a temperature of -75°C to -55°C. Water (H2O) becomes solid under the above conditions, so is not desirable as the first gas. The first gas may further contain a halogen element. Examples of halogen elements include fluorine. The first gas may include a fluorine-substituted alcohol, such as fluoromethanol. The first gas is not limited to alcohol, and may include a gas mixture of ethane or butane and water. The first gas may be formed, for example, by vaporizing the alcohol liquid.

[0023] The second gas is a gas containing a halogen element. Examples of halogen elements include fluorine. The second gas contains, for example, a fluoride gas. Examples of fluorides include hydrogen fluoride and fluorinated hydrocarbon compounds. Examples of fluorides include a gas represented by the composition formula C x H y F z (C represents carbon, H represents hydrogen, F represents fluorine, x represents an integer of 0 or more, y represents an integer of 0 or more, and z represents an integer of 2 or more).

[0024] The third gas is a gas that is in a gaseous state at a temperature equal to or lower than the liquefaction temperature of the first gas and contains a rare gas element. Examples of the gas containing a rare gas element include argon gas and krypton gas. The gas supply unit 5 does not necessarily have to include the gas supply source 53.

[0025] The fourth gas is a gas containing hydrogen. An example of a gas containing hydrogen is hydrogen gas. The fourth gas is not limited to this, and may be water vapor. The gas supply unit 5 does not necessarily have to include the gas supply source 54.

[0026] The fifth gas is a gas containing oxygen. An example of the gas containing oxygen is oxygen gas. The gas supply unit 5 does not necessarily have to include the gas supply source 55.

[0027] The gas exhaust unit 6 has a function of reducing the pressure inside the processing chamber 2 to create a vacuum state, and can also exhaust gas inside the processing chamber 2. The gas exhaust unit 6 has a valve 61, a turbo molecular pump 62, and a dry pump 63.

[0028] The cooling unit 7 includes, for example, a chiller 71 and a refrigerant pipe 72 inside the electrode 3. The chiller 71 cools the work-piece 10 by circulating a refrigerant through the refrigerant pipe 72.

[0029] The power supply unit 8 has a power supply 81 that supplies an AC voltage, and a matching circuit 82 such as a matching box. The power supply unit 8 has a function of matching the impedance between the processing chamber 2 and the power supply 81 using the matching circuit 82, and supplying a radio frequency (RF) voltage to the processing chamber 2. The radio frequency voltage is an AC voltage having a frequency of, for example, 200 kHz or more and 200 MHz or less.

[0030] The control unit 9 controls the gas supply unit 5, the gas exhaust unit 6, the cooling unit 7, and the power supply unit 8. The control unit 9 is configured using hardware such as a processor. Note that each operation may be stored as an operation program in a computer-readable recording medium such as a memory, and each operation may be executed by the hardware appropriately reading out the operation program stored in the recording medium.

[0031] (etching method) As shown in FIG. 1, the etching process in the first embodiment includes a process of alternately switching between an alcohol-containing gas introduction step (S2-1) and an etching step (S2-2) for processing recesses H, for example, until the ratio of the depth to the width (aspect ratio) of the recesses H becomes equal to or greater than a desired value.

[0032] 4 is a timing chart illustrating an example of an etching method according to the first embodiment. In the alcohol-containing gas introduction step (S2-1), the control unit 9 controls the power supply unit 8 to stop applying a high-frequency voltage between the electrodes 3 and 4 in the processing chamber 2, and the control unit 9 controls the flow rate adjustment unit 56 to introduce the first gas and the second gas from the gas supply source 51 and the gas supply source 52 into the processing chamber 2 through the opening 4b (RF: OFF, GAS1: ON, GAS2: ON). After the alcohol-containing gas introduction step (S2-1), the control unit 9 controls the valve 61, the turbomolecular pump 62, and the dry pump 63 to discharge the introduced gases. In the alcohol-containing gas introduction step (S2-1), before the introduction of the first gas and the second gas, the control unit 9 controls the flow rate adjustment unit 56 to stop the introduction of the third gas into the processing chamber 2 (GAS3: OFF). Note that, in this description, it is assumed that the fourth gas and the fifth gas are not used.

[0033] 5 is a cross-sectional schematic diagram illustrating the alcohol-containing gas introduction step (S2-1). FIG. 5 shows a portion of the XZ cross section of the object 10. In the alcohol-containing gas introduction step (S2-1), a surface layer 11 is formed on the surface of the object 10 placed on the surface 3a of the electrode 3 in the processing chamber 2. The surface layer 11 has a region 11a extending along the inner wall surface HA of the recess H, a region 11b extending along the inner bottom surface HB of the recess H, and a region 11c extending along the upper surface of the mask layer 106 (the uppermost layer of the object 10).

[0034] Surface layer 11 is, for example, a liquid layer and contains elemental fluorine and alcohol. Surface layer 11 is formed by supplying a gas in a gaseous state that is not in a plasma or radical state, and cooling workpiece 10 at a temperature and pressure in the liquid phase region of the first gas by cooling unit 7. Region 11b may be formed not only by the gas directly reaching inner bottom surface HB, but also by the gas adhering to inner wall surface HA and changing into liquid, and the changed liquid accumulating on inner bottom surface HB due to gravity.

[0035] The liquefaction temperature of the mixed gas of the first gas and the second gas can be uniquely determined depending on the pressure in the processing chamber 2 and the vapor pressure curve of the mixed gas. The workpiece 10 is preferably cooled at a pressure of 1 Pa or more and 10 Pa or less and a temperature of -75°C or more and -55°C or less. The third gas is inactive at temperatures below the liquefaction temperature of the mixed gas of the first gas and the second gas.

[0036] 6 and 7 are cross-sectional schematic views illustrating differences in the shape of the surface layer 11 due to differences in the state of the gas supplied to the object 10. Fig. 6 and Fig. 7 show part of the XZ cross section of the object 10.

[0037] When a high frequency voltage is applied and plasma or radicals are generated from the second gas, C x H y F z Since the plasma and radicals have unpaired electrons, the steric hindrance around the unpaired electrons is small, and they easily adhere to the inner wall surface HA of the recess H, but are unlikely to reach the inner bottom surface HB. Furthermore, because the plasma and radicals have a high adhesion probability, they can be formed on the workpiece 10 regardless of the liquefaction temperature of the second gas (for example, -70°C). Therefore, as shown in FIG. 6, the surface layer 11 is formed thickly on the upper part of the inner wall surface HA, but is unlikely to be formed on the inner bottom surface HB. In this case, the inner bottom surface HB is unlikely to be etched, and the etching rate decreases.

[0038] In contrast, when a second gas that is neither plasma nor radicals is introduced without supplying a high-frequency voltage, the second gas can be made to reach the inner bottom surface HB in a gaseous state, as shown in Fig. 2. Furthermore, by cooling the workpiece 10 to a temperature below the liquefaction temperature of the second gas (for example, -150°C), the gas that reaches the inner wall surface HA or the inner bottom surface HB becomes liquid or solid, and the surface layer 11 is formed. This makes it easier to form the surface layer 11 on the inner bottom surface HB. In this case, the inner bottom surface HB is more easily etched by the region 11b, improving the etching rate.

[0039] However, because the second gas has a high triple point pressure and a low triple point temperature, it is necessary to cool the workpiece 10 at a high pressure and a low temperature to form a liquid phase. For example, the liquid phase of CHF3 exists under a pressure of 450 mTorr, and a pressure of 5 Torr or more is required to cool the CHF3 to a temperature of -135°C or lower to form the liquid phase. This reduces the productivity of semiconductor devices.

[0040] Therefore, in the alcohol-containing gas introduction step (S2-1), a first gas containing alcohol is introduced together with a second gas. For example, the first gas has a lower triple point pressure and a higher triple point temperature than the second gas, and therefore can form a liquid phase at a pressure of 1 Pa to 10 Pa and a temperature of -75°C to -55°C. This can improve the productivity of semiconductor devices.

[0041] In the alcohol-containing gas introduction step (S2-1), the first gas and the second gas are introduced separately and mixed, but they may be introduced after the first gas and the second gas are mixed. Mixing them in advance facilitates uniform mixing and makes it easier to adjust the ratio of the first gas to the second gas. The ratio of the second gas in the mixed gas is higher than that of the first gas. Furthermore, an etchant with a low vapor pressure can be used, allowing for a higher liquefaction temperature. Furthermore, clusters of the mixed gas can be formed, making it easier to introduce the mixed gas into the recess H.

[0042] In the etching step (S2-2), the control unit 9 controls the flow rate adjustment unit 56 to introduce a third gas from the gas supply source 51 into the processing chamber 2 through the opening 4b, and the control unit 9 controls the power supply 81 to apply a high-frequency voltage between the electrode 3 and the electrode 4 in the processing chamber 2 by the power supply unit 8 (RF: ON, GAS3: ON). Before introducing the third gas, the control unit 9 controls the flow rate adjustment unit 56 to stop the introduction of the first gas and the second gas into the processing chamber 2 (GAS1: OFF, GAS2: OFF). The control unit 9 controls the valve 61, the turbomolecular pump 62, and the dry pump 63, and the introduced gas is discharged after the etching step (S2-2).

[0043] Fig. 8 is a cross-sectional schematic diagram for explaining the etching step (S2-2). Fig. 8 shows a part of the XZ cross section of the object 10. In the etching step (S2-2), plasma is generated from the third gas, and the object 10 and the surface layer 11 are etched by etching using the plasma (argon plasma in Fig. 8).

[0044] Ions in the plasma are accelerated toward the electrode 3. Therefore, the first layer 103 and the second layer 104 are etched mainly along with the regions 11b and 11c in the etching step (S2-2). Furthermore, the etching step (S2-2) processes the inner bottom surface HB of the recess H, thereby increasing the aspect ratio of the recess H.

[0045] In the alcohol-containing gas introduction step (S2-1), only the first gas may be introduced to form the surface layer 11, and in the etching step (S2-2), the second gas may be introduced instead of the third gas, and the inner bottom surface HB of the recess H may be processed by etching using plasma generated from the second gas.

[0046] The duration of the alcohol-containing gas introduction step (S2-1), the duration of the etching step (S2-2), and the timing of switching between the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2) may be controlled in accordance with data obtained by, for example, in-situ monitoring the thickness of the surface layer 11 using a measuring device such as an ellipsometer, and acquiring data showing the relationship between the thicknesses of the regions 11a to 11c. For example, it is preferable to switch between the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2) in accordance with the data before etching stops due to insufficient thickness of the surface layer 11.

[0047] As described above, by alternately switching between the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2), the etching rate can be improved and high-speed etching can be achieved even when forming recesses H with a high aspect ratio.

[0048] (Memory layer formation process) 9 is a cross-sectional view illustrating a memory layer forming step. Fig. 9 shows a portion of an XZ cross section of the object 10. In the memory layer forming step, a memory film 203 including a block insulating film 233, a charge storage layer 232, and a tunnel insulating film 231, a semiconductor channel layer 202, and a core insulating film 201 are formed in this order in the recess H. The core insulating film 201, the semiconductor channel layer 202, and the memory film 203 function as a memory layer that constitutes a memory cell.

[0049] The core insulating film 201 may be, for example, a silicon oxide film. The semiconductor channel layer 108 may be, for example, a polysilicon layer. The tunnel insulating film 231 may be, for example, a stacked film having a silicon oxide film and a silicon oxynitride film. The charge storage layer 232 may be, for example, a silicon nitride film. The block insulating film 233 may be, for example, a silicon oxide film.

[0050] After forming the memory film 203, the first layer 103 is removed, a cavity is formed between the first layer 103 and the second layer 104, and a plurality of conductive films are stacked in the cavity to form the conductive layer 110. The conductive layer 110 functions as, for example, a gate electrode (word line). Furthermore, contact plugs, wiring, interlayer insulating films, etc. are formed on the substrate 101. This allows the semiconductor device to be manufactured.

[0051] Although a memory hole in which a memory layer is formed is exemplified as an example of the recess H in this embodiment, the application of this embodiment is not limited to the memory hole. For example, this embodiment can be applied to various recesses such as a trench (ST) for replacing a sacrificial layer with a conductive layer 110, a hole for forming a contact plug connected to the conductive layer 110, etc.

[0052] <Modification of the first embodiment> 10 is a flowchart for explaining a modified example of the method for manufacturing a semiconductor device in the first embodiment. This other example of the method for manufacturing a semiconductor device includes a preparation step (S1), an etching step (S2), and a memory layer formation step (S3). Note that the preparation step and the memory layer formation step are the same as those in the first embodiment, and therefore will not be described in this embodiment.

[0053] [Etching process] The etching step in the modified example of the first embodiment can be performed using an etching apparatus 1 shown in Fig. 3. As shown in Fig. 10, the etching step includes a step of alternately switching between an alcohol-containing gas introduction step (S2-1) and an etching step (S2-2) until, for example, the aspect ratio of the recess H reaches a desired value, and a plasma treatment step (S2-3) of performing plasma treatment between the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2) after the step of alternately switching between the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2), for example, when the thickness of the region 11b in the surface layer 11 is equal to or greater than a predetermined value.

[0054] 11 is a timing chart for explaining an example of an etching method according to a modification of the first embodiment. The alcohol-containing gas introduction step (S2-1) and the etching step (S2-2) are performed by alternately switching between them, similar to the example of the etching method described with reference to FIG. 4. Therefore, the description of the first embodiment will be used as appropriate.

[0055] In the plasma processing step (S2-3), the control unit 9 controls the flow rate adjustment unit 56 to introduce a fifth gas from the gas supply source 55 into the processing chamber 2 through the opening 4b, and the control unit 9 controls the power supply 81 to apply a high-frequency voltage between the electrode 3 and the electrode 4 in the processing chamber 2 by the power supply unit 8 (RF: ON, GAS5: ON). Alternatively, in the plasma processing step (S2-3), the control unit 9 controls the flow rate adjustment unit 56 to introduce a third gas from the gas supply source 53 into the processing chamber 2 through the opening 4b, and the control unit 9 controls the power supply 81 to apply a high-frequency voltage between the electrode 3 and the electrode 4 in the processing chamber 2. After the alcohol-containing gas introduction step (S2-1), the control unit 9 controls the valve 61, the turbomolecular pump 62, and the dry pump 63 to discharge the introduced gas.

[0056] If the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2) are repeatedly switched, the region 11b substantially perpendicular to the direction of plasma movement may become too thick, and the alcohol may inhibit etching.

[0057] On the other hand, in the plasma treatment step (S2-3), plasma is generated from the third gas or the fifth gas, and part of the carbon or part of the alcohol contained in the region 11b can be removed by etching using the plasma.

[0058] The duration of the plasma treatment step (S2-3) may be controlled in accordance with data obtained by, for example, monitoring the thickness of the surface layer 11 in situ using a measuring instrument such as an ellipsometer to obtain data showing the relationship between the thicknesses of the regions 11a to 11c. For example, it is preferable to perform the plasma treatment step (S2-3) when the thickness of the region 11b is between 10 nm and 20 nm.

[0059] As described above, in the modification of the first embodiment, by performing the plasma treatment step (S2-3) between the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2), it is possible to prevent a part of the alcohol contained in the surface layer 11 from being removed and hindering the processing of the inner bottom surface HB. Note that if the aspect ratio of the recess H is less than the desired value after the plasma treatment step (S2-3), the process of alternately switching between the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2) may be performed again.

[0060] <Second embodiment> 12 is a flowchart for explaining an example of a method for manufacturing a semiconductor device according to the second embodiment. The example of the method for manufacturing a semiconductor device according to the second embodiment includes a preparation step (S1), an etching step (S2), and a memory layer formation step (S3). Note that the preparation step and the memory layer formation step are the same as those in the first embodiment, and therefore will not be described in this embodiment.

[0061] [Etching process] The etching step in the second embodiment can be performed using an etching apparatus 1 shown in Fig. 3. As shown in Fig. 12, the etching step does not include the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2), but includes an alcohol-containing gas introduction / etching step (S2-4) instead.

[0062] 13 is a timing chart illustrating an example of an etching method according to the second embodiment. In the alcohol-containing gas introduction / etching step (S2-4), the control unit 9 controls the power supply unit 8 to apply a high-frequency voltage between the electrodes 3 and 4 in the processing chamber 2, and the control unit 9 controls the flow rate adjustment unit 56 to introduce the first gas and the second gas from the gas supply source 51 into the processing chamber 2 through the opening 4b (RF: ON, GAS1: ON, GAS2: ON). The third to fifth gases are not used. The control unit 9 controls the valve 61, turbomolecular pump 62, and dry pump 63 to discharge the introduced gases after the alcohol-containing gas introduction / etching step (S2-4). The explanations for the alcohol-containing gas introduction step (S2-1) and the etching step (S2-2) can be used for other explanations of the alcohol-containing gas introduction / etching step (S2-4), as appropriate.

[0063] In the alcohol-containing gas introduction / etching step (S2-4), the workpiece 10 is cooled to a temperature of 0°C or below by the cooling unit 7 at a temperature and pressure in the liquid phase region of the first gas. The first and second gases are then introduced, and plasma is generated from the mixed gas. When the plasma reaches the inner wall surface HA and the inner bottom surface HB, it liquefies, forming a surface layer 11. Furthermore, a mixture of the second gas dissolved in the liquid alcohol and ions derived from the second gas adheres to the inner wall surface HA and the inner bottom surface HB. The mixture adhered to the inner wall surface HA accumulates on the inner bottom surface HB due to gravity, forming the surface layer 11. This facilitates the formation of a region 11b on the inner bottom surface HB. In this case, the inner bottom surface HB is more easily etched by the region 11b, making it easier to process the inner bottom surface HB and improving the etching rate.

[0064] <Third embodiment> 14 is a flowchart for explaining an example of a method for manufacturing a semiconductor device according to the third embodiment. The example of the method for manufacturing a semiconductor device according to the third embodiment includes a preparation step (S1), an etching step (S2), and a memory layer formation step (S3). Note that the preparation step and the memory layer formation step are the same as those in the first embodiment, and therefore will not be described in this embodiment.

[0065] [Etching process] The etching step in the third embodiment can be performed using an etching apparatus 1 shown in Fig. 3. As shown in Fig. 14, the etching step does not include an alcohol-containing gas introduction step (S2-1), but includes an etching step (S2-2), a hydrophobic film formation step (S2-5), and a hydrophilization step (S2-6).

[0066] Fig. 15 is a cross-sectional view illustrating the hydrophobic film forming step (S2-5) in the third embodiment. Fig. 15 shows a part of the XZ cross section of the object 10. In the hydrophobic film forming step (S2-5), a hydrophobic film 107 is formed on the inner wall surface HA and the inner bottom surface HB of the recess H.

[0067] The hydrophobic film 107 has a region 107a in contact with the inner wall surface HA and a region 107b in contact with the inner bottom surface HB. The surface of the hydrophobic film 107 does not have any hydrophilic groups.

[0068] The hydrophobic film 107 contains carbon elements and may be, for example, a fluorocarbon film.

[0069] The hydrophobic film 107 may be formed by supplying a silylating agent to the recess H. The silylating agent is, for example, a silane compound containing silicon, hydrogen, and carbon. The silylating agent may have a Si-N bond. Examples of the silylating agent include aminosilane compounds, chlorosilane compounds, methoxysilane compounds, and cyclic silane compounds. The silylating agent may be supplied, for example, by controlling the power supply unit 8 with the control unit 9 to apply no high-frequency voltage between the electrodes 3 and 4 of the processing chamber 2, and then controlling the flow rate adjustment unit 56 with the control unit 9 to introduce a gas containing the silylating agent into the processing chamber 2 through the opening 4b from a gas supply source other than the gas supply sources 51 to 55.

[0070] Examples of aminosilane compounds include N-(trimethylsilyl)dimethylamine (TMSDMA), hexamethyldisilazane (HMDS), n-octyldimethyl(dimethylamino)silane (ODMDMAS), etc. The silylating agent is C n H 2n+2 (n is a natural number of 2 or more), and the like.

[0071] Examples of chlorosilane compounds include octadecyltrichlorosilane (ODTC), examples of methoxysilane compounds include octadecyltrimethoxysilane (ODMS), etc. Examples of cyclic silane compounds include N-methyl-aza-2,2,4-methylsilacyclopentane (CAZ), etc.

[0072] For example, when the silylation agent is TMSDMA, when TMSDMA is supplied to recess H, a silylation reaction breaks the Si-N bonds in the TMSDMA molecules, and trimethylsilyl groups bond to oxygen and nitrogen elements on the surfaces of inner wall surface HA and inner bottom surface HB, thereby forming hydrophobic film 107 having silicon, oxygen, carbon, and hydrogen elements.

[0073] Fig. 16 is a cross-sectional schematic view illustrating the hydrophilization step (S2-6) in the third embodiment. Fig. 16 shows a part of the XZ cross section of the object 10. In the hydrophilization step (S2-6), the region 107b is removed while leaving at least a part of the region 107a remaining, thereby exposing the inner bottom surface HB and making the inner bottom surface HB hydrophilic.

[0074] The hydrophilization step (S2-6) is performed, for example, by controlling the power supply unit 8 with the control unit 9 to apply a high-frequency voltage between the electrodes 3 and 4 in the processing chamber 2 with the power supply unit 8, controlling the flow rate adjustment unit 56 with the control unit 9 to introduce a fourth gas and a fifth gas from the gas supply sources 54 and 55 into the processing chamber 2 through the opening 4b, and treating the hydrophobic film 107 with plasma treatment using plasma generated from a mixed gas of the fourth gas and the fifth gas. Because the plasma treatment removes the region 107b more easily than the region 107a, the region 107b can be removed while leaving at least a portion of the region 107a remaining.

[0075] The hydrophilization is achieved by forming hydroxyl groups and amino groups on the surface of the inner bottom surface HB through the plasma treatment. That is, the hydrophilized surface of the inner bottom surface HB has hydrophilic groups containing hydrogen elements.

[0076] 17 is a cross-sectional view illustrating the etching step (S2-2) in the third embodiment. The etching step (S2-2) is performed after the hydrophilization step (S2-6). The cooling unit 7 cools the workpiece 10 to a temperature of 0°C or less at a temperature and pressure in the liquid phase region of the first gas. The control unit 9 controls the power supply unit 8 to apply a high-frequency voltage between the electrodes 3 and 4 in the processing chamber 2. The control unit 9 controls the flow rate regulator 56 to introduce the second gas, the third gas, or the fourth gas from the gas supply source 52, the gas supply source 53, or the gas supply source 54 into the processing chamber 2 through the opening 4b. Plasma is generated from the second gas, the third gas, or the fourth gas. The hydrophilized inner bottom surface HB is then etched using the plasma. The workpiece 10 may be cooled to a temperature below 30°C, for example. Other explanations of the etching step (S2-2) in the third embodiment can be appropriately applied to the etching step (S2-2) in the first embodiment.

[0077] In the etching step (S2-2), the recess H tends to taper from its top to its bottom. This is because the generated plasma has difficulty reaching the lower part of the inner wall surface of the recess H or the closer it is to the inner bottom surface of the recess H, and etching tends to progress at the upper part of the inner wall surface of the recess H. As a result, a dimensional difference tends to occur from the top to the bottom of the recess H.

[0078] In contrast, in the third embodiment, by forming a hydrophobic film 107 on the inner wall surface HA of the recess H, the adsorption of hydrogen fluoride, water vapor, etc. to the inner wall surface HA is suppressed, thereby suppressing the progress of etching, and the adsorption of hydrogen fluoride, water vapor, etc. to the inner bottom surface HB is increased, allowing the inner bottom surface HB to be etched. Therefore, even when forming recess H having a high aspect ratio, the processing accuracy of the recess H can be improved. As a result, it becomes possible to control the dimensions of the recess H uniformly from the top to the bottom of the recess H.

[0079] <Fourth embodiment> The first to third embodiments can be combined as appropriate. Fig. 18 is a flowchart for explaining an example of a method for manufacturing a semiconductor device in the fourth embodiment. Another example of the method for manufacturing a semiconductor device includes a preparation step (S1), an etching step (S2), and a memory layer formation step (S3). Note that the preparation step and the memory layer formation step are the same as those in the first embodiment, and therefore will not be described in this embodiment.

[0080] [Etching process] The etching process in the fourth embodiment can be performed using an etching apparatus 1 shown in Fig. 3. As shown in Fig. 12, the etching process includes an alcohol-containing gas introduction step (S2-1), an etching step (S2-2), a hydrophobic film formation step (S2-5), and a hydrophilization step (S2-6). Since each step is the same as in the first to third embodiments, a description thereof will be omitted in this embodiment.

[0081] 19 is a cross-sectional view illustrating an example of a method for manufacturing a semiconductor device according to the fourth embodiment. FIG. 19 shows a portion of an XZ cross section of an object 10 to be processed. In the etching process according to the fourth embodiment, a hydrophobic film 107 is formed in a hydrophobic film forming step (S2-5), and the inner bottom surface HB is hydrophilized in a hydrophilization step (S2-6). Then, a surface layer 11 is formed on the hydrophobic film 107 and the hydrophilized inner bottom surface HB in an alcohol-containing gas introduction step (S2-1), and the inner bottom surface HB is processed in an etching step (S2-2). In this case, the inner wall surface HA is less susceptible to etching due to the hydrophobic film 107, and the hydrophilized inner bottom surface HB is more susceptible to etching due to the surface layer 11. This makes it easier to process the inner bottom surface HB, improving the etching rate.

[0082] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0083] 1...etching apparatus, 2...processing chamber, 3...electrode, 3a...surface, 4...electrode, 4a...surface, 4b...opening, 5...gas supply section, 6...gas exhaust section, 7...cooling section, 8...power supply section, 9...control section, 10...object to be processed, 11...surface layer, 11a...region, 11b...region, 11c...region, 51...gas supply source, 52...gas supply source, 53...gas supply source, 54...gas supply source, 55...gas supply source, 56...flow rate adjustment section, 61...valve, 62...turbomolecular pump, 63...driving pump, 71...chiller, 72...refrigerant pipe, 81...power supply, 82...matching circuit, 101...substrate, 102...underlying layer, 103...first layer, 104...second layer, 106...mask layer, 107...hydrophobic film, 107a...region, 107b...region, 110...conductive layer, 201...core insulating film, 202...semiconductor channel layer, 203...memory film, 231...tunnel insulating film, 232...charge storage layer, 233...block insulating film, H...recess, HA...inner wall surface, HB...inner bottom surface.

Claims

1. a first gas containing an alcohol or a combination of the first gas and a second gas containing a halogen element is introduced to form a surface layer on an inner bottom surface of a recess formed in a surface of an object cooled to a temperature of 0°C or less; introducing the second gas or a third gas containing a rare gas element, generating a first plasma from the second gas or the third gas, and processing the inner bottom surface by etching using the first plasma; The formation of the surface layer and the processing of the inner bottom surface are alternately switched. A method for manufacturing a semiconductor device.

2. a first gas containing an alcohol and a second gas containing a halogen element are introduced, a second plasma is generated from a mixed gas of the first gas and the second gas, and a surface layer is formed on an inner bottom surface of a recess formed in a surface of an object cooled to a temperature of 0°C or less, while the inner bottom surface is processed by etching using the second plasma; A method for manufacturing a semiconductor device.

3. forming a hydrophobic film having a first region in contact with an inner wall surface of a recess formed in a surface of an object cooled to a temperature of 0°C or less and a second region in contact with an inner bottom surface of the recess; removing the second region while leaving at least a portion of the first region remaining to expose the inner bottom surface, and making the inner bottom surface hydrophilic; introducing a second gas containing a halogen element, a third gas containing a rare gas element, or a fourth gas containing a hydrogen element, generating a third plasma from the second gas, the third gas, or the fourth gas, and processing the hydrophilized inner bottom surface by etching using the third plasma; The hydrophilization of the inner bottom surface and the processing of the inner bottom surface are alternately switched. A method for manufacturing a semiconductor device.

4. Before forming the surface layer, forming a hydrophobic film having a first region in contact with an inner wall surface of the recess and a second region in contact with the inner bottom surface; removing the second region while leaving at least a portion of the first region remaining to expose the inner bottom surface, and making the inner bottom surface hydrophilic; The method for manufacturing a semiconductor device according to claim 1 .

5. the surface layer is formed by introducing the first gas and the second gas. The method for manufacturing a semiconductor device according to claim 1 .

6. the first gas does not contain the halogen element, the surface layer is formed by introducing the first gas. The method for manufacturing a semiconductor device according to claim 1 .

7. between the formation of the surface layer and the processing of the inner bottom surface, a third gas containing a rare gas element or a fifth gas containing an oxygen element is introduced, a fourth plasma is generated from the third gas or the fifth gas, and a part of the carbon contained in the surface layer or a part of the alcohol is removed by etching using the fourth plasma; 5. The method for manufacturing a semiconductor device according to claim 1, claim 2, or claim 4.

8. the surface layer is formed by separately introducing the first gas and the second gas.

5. The method for manufacturing a semiconductor device according to claim 1, claim 2, or claim 4.

9. the surface layer is formed by mixing the first gas and the second gas and then introducing the gas.

5. The method for manufacturing a semiconductor device according to claim 1, claim 2, or claim 4.

10. The workpiece is cooled at a temperature and pressure in a liquid phase region of the first gas.

5. The method for manufacturing a semiconductor device according to claim 1, claim 2, or claim 4.

11. The first gas is a gas represented by the composition formula C ｘ H ｙ F ｚ (C represents carbon, H represents hydrogen, F represents fluorine, x represents an integer of 0 or more, y represents an integer of 0 or more, and z represents an integer of 2 or more), 5. The method for manufacturing a semiconductor device according to claim 1, claim 2, or claim 4.

12. the first gas contains methanol, ethanol, or an alcohol containing the halogen element; 5. The method for manufacturing a semiconductor device according to claim 1, claim 2, or claim 4.

13. The surface of the hydrophobic membrane does not have any hydrophilic groups.

5. The method for manufacturing a semiconductor device according to claim 3.

14. the hydrophilized surface of the inner bottom surface has a hydrophilic group containing a hydrogen atom; 5. The method for manufacturing a semiconductor device according to claim 3.

15. The hydrophobic film contains a carbon element.

5. The method for manufacturing a semiconductor device according to claim 3.

16. The hydrophobic membrane is a silylating agent is supplied to the recess, 5. The method for manufacturing a semiconductor device according to claim 3.

17. the second region is removed by introducing a fourth gas containing hydrogen and a fifth gas containing oxygen, and treating the second region with a fifth plasma generated from a mixed gas of the fourth gas and the fifth gas; the inner bottom surface is made hydrophilic by being treated with the fifth plasma; 5. The method for manufacturing a semiconductor device according to claim 3.

18. the object to be processed has a stacked layer including a silicon oxide film and a silicon nitride film, the inner bottom surface is formed on the surfaces of the silicon oxide film and the silicon nitride film.

5. The method for manufacturing a semiconductor device according to claim 1.

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