Etching method

Abstract

The purpose of the present invention is to provide a technique for etching SiGe with a high selectivity ratio for Ge.　One etching method according to the present invention is for etching a silicon germanium film as a processing target in a film structure including a germanium film and the silicon germanium film formed on a surface of a wafer, the method comprising: a step for forming a modified layer on the surface of the film structure by supplying hydrogen radicals to the film structure in a state where the wafer is heated; and a step for, after the step of forming the modified layer, cooling the wafer to a temperature between 0°C and room temperature, and etching the silicon germanium film by supplying sulfur hexafluoride or a gas containing sulfur hexafluoride and argon to the modified layer.

Description

Etching Method

[0001] The present invention relates to an etching method.

[0002] The miniaturization and high performance of electronic devices are being driven by the miniaturization and high integration of the semiconductor devices that make them up. In logic devices, the structure of field-effect transistors (FETs) has transitioned from two-dimensional planar to three-dimensional fin structures since the 14-nm node. To further improve integration, development of gate-all-around (GAA) FETs is currently underway. GAA FETs have a structure in which the entire channel is surrounded by a gate, and feature a vertically stacked structure of thin-film channels called nanosheets or thin-wire channels called nanowires. While silicon (Si) is currently used as the channel material, silicon germanium (SiGe) or germanium (Ge), which have higher mobility than Si, are considered promising for technology nodes beyond 5 nm.

[0003] For example, in Patent Document 1, when a structure in which Si layers and SiGe layers are alternately stacked is plasma etched, NF ３

[0003] Patent Literature 2 describes a method for selectively isotropically etching each SiGe layer relative to each Si layer using a pulse-modulated plasma using a gas. Patent Literature 2 describes a method for selectively etching the SiGe or Ge relative to the Si by supplying a process gas containing a fluorine-containing gas and a hydrogen-containing gas to a substrate having SiGe or Ge and Si on its surface. Patent Literature 3 also describes a technology for performing a plasma process on a semiconductor substrate having a Si layer and a SiGe layer formed on the Si layer to expose the SiGe layer, and then performing a hydrogen plasma process to form a Si segregation layer that protects the SiGe channel without damaging the SiGe channel.

[0004] JP 2015-76459 A JP 2020-53448 A JP 2020-170835 A

[0005] When a Ge channel, which is a channel made of Ge, is employed, the sacrificial layer is SiGe. In this case, considering the basic etching characteristics of SiGe, SiGe is a mixed crystal semiconductor made of Si and Ge, which are group IV semiconductors, and Si atoms and Ge atoms of different sizes are randomly distributed and covalently bonded, so its etching characteristics depend greatly on the composition ratio of the mixed crystal. When comparing the etching resistance of Si, SiGe, and Ge, Si is generally the most difficult to etch, and as the Ge composition increases, it becomes easier to etch. This is because the covalent bond energy is the largest in the Si-Si bond at 3.25 eV, the smallest in the Ge-Ge bond at 2.84 eV, and the intermediate energy of the Si-Ge bond at 3.12 eV. For this reason, CF ４ and Cl ２ When using plasma of a commonly used halogen-based single gas such as HBr, the etching rates often have a relationship of Si<SiGe<Ge. Therefore, it is difficult to achieve selective etching of SiGe relative to Ge. The present invention has been made in view of the above-mentioned problems, and aims to provide a technique for etching SiGe with a high selectivity relative to Ge.

[0006] In order to solve the above-mentioned problems, one representative etching method of the present invention is an etching method for etching a silicon germanium film, which is a processing target, of a film structure including a silicon germanium film and a germanium film formed on the surface of a wafer, and includes the steps of: supplying hydrogen radicals to the film structure while the wafer is heated, thereby forming a denatured layer on the surface of the film structure; and, after the step of forming the denatured layer, cooling the wafer to 0°C to room temperature, and supplying a gas containing sulfur hexafluoride or sulfur hexafluoride and argon to the denatured layer, thereby etching the silicon germanium film.

[0007] According to the present invention, it is possible to etch SiGe with a high selectivity to Ge. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiments.

[0008] FIG. 1 is a flow chart of an etching method according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the configuration of a plasma processing apparatus. FIG. 3 is a diagram showing a time chart of the etching method. FIG. 4 is a diagram showing the wafer temperature dependence of the SiGe to Ge etching selectivity during hydrogen plasma processing. FIG. 5 is a diagram showing the hydrogen plasma processing time dependence of the SiGe to Ge etching selectivity. FIG. 6 is a cross-sectional view illustrating an example of the structure of a device to which an embodiment of the present disclosure is applied and the state of the device after etching.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted. The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc., disclosed in the drawings.

[0010] A "film" refers to an object formed primarily through a film formation process. For example, when a film formation process is performed on a wafer (substrate), the film is formed uniformly and has a thickness smaller than that of the wafer. The term "film" can also be used interchangeably with "layer."

[0011] [Embodiment] (Procedure of Etching Method) Fig. 1 is a flow diagram of an etching method according to an embodiment of the present invention. Each step will be described below. The etching method of the present disclosure is a method for etching a silicon germanium film, which is a processing target, of a film structure including a SiGe film and a Ge film formed on the surface of a wafer.

[0012] Step S101 is a process of supplying hydrogen radicals to the film structure while the wafer is heated, to form a modified layer on the surface of the film structure. Specifically, in step S101, hydrogen gas is introduced into a processing chamber in which a wafer having a SiGe film and a Ge film on its surface side is placed. The hydrogen gas is H ２ gas and H ２The gas may be a mixture of a gas and a diluent gas such as Ar (argon) gas. The Ar gas may be He gas, or another rare gas or nitrogen gas. The wafer temperature in this step is adjusted to a temperature range of 100°C to 350°C by the temperature control function of the stage on which the wafer is placed. That is, the wafer is heated to 150°C to 350°C. In this case, the wafer temperature may be increased and maintained by irradiating it with electromagnetic waves using a lamp installed in the processing chamber. The hydrogen gas is activated by the plasma generated by the plasma source, and hydrogen radicals are separated and supplied to the film structure. A hydrogen-related modified layer of a thickness determined by specified conditions is formed.

[0013] Subsequently, in steps S102 to S104, after the step of forming the denatured layer, the wafer is cooled to 0° C. or room temperature, and SF is applied to the denatured layer. ６ or science fiction ６ This is a process of etching the SiGe film by supplying a gas containing hydrogen and Ar. Specifically, in step S102, the wafer is quickly cooled to a temperature of 100° C. or less. The temperature of 100° C. or less can be, for example, 0° C. to room temperature. The wafer is cooled via a stage on which the wafer is placed. To quickly cool the wafer, a rare gas such as Ar gas may be introduced at high pressure to accelerate the cooling by thermal substitution. Thereafter, the hydrogen gas is quickly exhausted, and the plasma treatment using hydrogen gas (hereinafter also referred to as "hydrogen plasma treatment") is terminated (step S103).

[0014] Next, in step S104, an F-based gas is introduced into the processing chamber. ６ (sulfur hexafluoride) gas or SF ６ Other examples of F-based gases include SF6 and SF7. ６ Gas and NF ３ The gas may be an inorganic gas or a halogen-containing hydrocarbon compound (CF ４ , CHF ３ , CCl ２ F ３, ...). Furthermore, like hydrogen gas, a mixed gas containing a dilution gas other than Ar in addition to the above-mentioned gas species may also be used. Subsequently, in step S105, the F-based gas is activated by plasma generated by the plasma source, and the SiGe film is selectively etched relative to the Ge film due to the effect of the hydrogen-related modified layer formed on the surface in step S101. Thereafter, the F-based gas is quickly exhausted from the processing chamber, and the etching process using the F-based gas is terminated (step S106).

[0015] Next, in step S107, after the etching step, the wafer is heated to remove hydrogen from the surface of the film structure. Specifically, in step S107, the wafer is heated as quickly as possible to 400°C or higher using a heating mechanism installed in the processing chamber to perform the heat treatment. The heating mechanism may be a stage-based heating mechanism, or may be a mechanism that heats the wafer by irradiating it with electromagnetic waves from a lamp such as an infrared lamp or a halogen lamp. The heat quickly discharges hydrogen gas remaining in the denatured layers of the SiGe film and the Ge film.

[0016] Thereafter, the temperature is quickly cooled to 100° C. or less (step S108).

[0017] The process comprising the steps of forming the modified layer, etching, and removing hydrogen constitutes one cycle, and this cycle is repeated multiple times. Specifically, the process comprising steps S101 to S108 is repeated, and a termination condition is determined as to whether a desired etching amount has been obtained (step S109). The etching is terminated when the desired etching amount has been obtained for the SiGe film.

[0018] 1 is not limited to the order shown. For example, step S108 and step S109 may be interchanged. In this case, it is determined whether the desired etching amount has been obtained for the traces of step S107. If the desired etching amount has not been obtained, the wafer can be cooled in step S108 only to the processing temperature of step S101, rather than to a temperature of 100° C. or less. In this way, step S101 can be performed quickly, and the time required for repeating the process can be shortened.

[0019] (Configuration of Plasma Processing Apparatus) Next, an example of a plasma processing apparatus that can be used in the etching method for a film structure including a SiGe film and a Ge film according to the present embodiment will be described. Fig. 2 is a diagram showing an example of the configuration of a plasma processing apparatus 100. In Fig. 2, cross-sectional views are used for the processing chamber 1 and other locations where wafer processing is performed, and power supplies and the like are shown as block diagrams by function.

[0020] The processing chamber 1 is a space separated from the external environment by a base chamber 11 and configured to achieve a pressure lower than atmospheric pressure. A wafer stage 4 (hereinafter referred to as stage 4) is installed within the processing chamber 1, on which a wafer 2, a sample to be processed, is placed. A plasma source including a quartz chamber 12, an ICP coil 34, and a high-frequency power supply 20 is installed in a container 60 disposed above the base chamber 11. In this example, an ICP (Inductively Coupled Plasma) discharge method is used for the plasma source. The high-frequency power supply 20 for plasma generation is connected to the ICP coil 34 disposed outside the cylindrical quartz chamber 12 via a matching box 22. The frequency of the high-frequency power is within a frequency band of several tens of megahertz, such as 13.56 MHz.

[0021] A top plate 6 is installed on the top of the quartz chamber 12. A shower plate 5 is installed on the top plate 6, and a gas dispersion plate 17 is installed below the top plate 6. The processing gas is introduced into the processing chamber 1 from the outer periphery of the gas dispersion plate 17.

[0022] The supply flow rate of the processing gas is adjusted by mass flow controllers 50-1 to 50-3 installed for each gas type. ２ Gas, SF ６ Although the example shows the use of Ar gas, the gas species is not limited to these.

[0023] The lower part of the processing chamber 1 is connected to a pump 15 via a vacuum exhaust pipe 16 in order to reduce the pressure inside the processing chamber 1. The pump 15 is configured, for example, by at least one of a turbomolecular pump, a mechanical booster pump, and a dry pump. A pressure adjustment mechanism 14 is installed upstream of the pump 15 in order to adjust the pressure in the processing chamber 1 and the discharge region 3 inside the quartz chamber 12. The pressure adjustment mechanism 14, the pump 15, and the vacuum exhaust pipe 16 are collectively referred to as the exhaust mechanism. The stage 4 is fixed to the base chamber 11 with an O-ring 81 provided to create a vacuum seal between the stage 4 and the bottom surface of the base chamber 11.

[0024] An IR (Infrared) lamp unit for heating the wafer 2 is installed between the stage 4 and the quartz chamber 12 constituting the ICP plasma source. The IR lamp unit mainly includes an IR lamp 62, a reflector 63 for reflecting IR light, and an IR light-transmitting window 74. A circular lamp is used as the IR lamp 62. The light (electromagnetic waves) emitted from the IR lamp 62 is, for example, light mainly ranging from visible light to infrared light (herein referred to as IR light). In this example, three IR lamps 62-1, 62-2, and 62-3 are installed as the IR lamps 62, but two or four lamps may be installed. A reflector 63 is installed above the IR lamps 62 to reflect the IR light downward (toward the placement of the wafer 2).

[0025] An IR lamp power supply 64 is connected to the IR lamp 62, and a high frequency cut filter 25 is installed midway between the IR lamps 62 and 62 to prevent noise from the high frequency power for plasma generation generated by the high frequency power supply 20 from entering the IR lamp power supply 64. The IR lamp power supply 64 also has a function to independently control the power supplied to the IR lamps 62-1, 62-2, and 62-3, making it possible to adjust the radial distribution of the amount of heat applied to the wafer 2.

[0026] In this example, a gas flow path 75 is formed in the center of the IR lamp unit so that gas supplied into the quartz chamber 12 flows into the processing chamber 1. This gas flow path 75 is provided with a slit plate (ion shielding plate) 78 with multiple holes that shields ions and electrons generated in the plasma generated inside the quartz chamber 12 and allows only neutral gases and neutral radicals to pass through and irradiate the wafer 2.

[0027] Meanwhile, a coolant flow path 39 for cooling the stage 4 is formed inside the stage 4, and a coolant is circulated and supplied by a chiller 38. Furthermore, in order to fix the wafer 2 to the stage 4 by electrostatic attraction, electrostatic attraction electrodes 30, which are plate-shaped electrodes, are embedded in the stage 4, and a DC power supply 31 for electrostatic attraction is connected to each of them.

[0028] Furthermore, in order to efficiently cool the wafer 2, He gas (cooling gas) can be supplied between the stage 4 and the backside of the wafer 2 placed on the stage 4. The amount of He gas supplied is adjusted by a mass flow controller 50-4. Furthermore, to prevent scratches on the backside of the wafer 2 even when heating and cooling are performed while the electrostatic attraction electrode 30 is activated and the wafer 2 is electrostatically attracted, the surface of the stage 4 (wafer-mounting surface) is coated with a resin such as polyimide. Furthermore, a thermocouple 70 for measuring the temperature of the stage 4 is installed inside the stage 4, and this thermocouple 70 is connected to a thermocouple thermometer 71.

[0029] In addition, optical fibers 92-1 and 92-2 for measuring the temperature of the wafer 2 are installed at three locations: near the center of the wafer 2 placed on the stage 4, near the middle in the radial direction of the wafer 2, and near the outer periphery of the wafer 2. The optical fiber 92-1 guides IR light from an external IR light source 93 to the back surface of the wafer 2 and irradiates the back surface of the wafer 2. On the other hand, the optical fiber 92-2 collects IR light that has been transmitted through and reflected by the wafer 2 out of the IR light irradiated by the optical fiber 92-1, and transmits it to a spectroscope 96.

[0030] Specifically, external IR light generated by the external IR light source 93 is transmitted to an optical path switch 94 for turning the optical path on and off. The light is then split into multiple beams (three in this case) by an optical distributor 95 and irradiated onto the respective positions on the backside of the wafer 2 via three optical fibers 92-1. The IR light absorbed and reflected by the wafer 2 is transmitted to a spectrometer 96 via an optical fiber 92-2, where a detector 97 obtains data on the wavelength dependence of the spectral intensity. The wavelength dependence data on the spectral intensity obtained by the detector 97 is sent to the calculation unit 41 of the control unit 40, where the absorption wavelength is calculated. The temperature of the wafer 2 can be calculated based on this data. An optical multiplexer 98 is installed midway along the optical fiber 92-2, allowing the light to be spectroscopically measured at one of the measurement points—the wafer center, wafer middle, or wafer periphery—to be switched. This allows the calculation unit 41 to determine the respective temperatures of the wafer center, wafer middle, and wafer periphery.

[0031] The control unit 40 controls each mechanism constituting the plasma processing apparatus 100. Specifically, it controls the high-frequency power supply 20 to turn on and off the high-frequency power supply to the ICP coil 34. It also controls the gas supply unit 51 to adjust the type and flow rate of gas supplied from each of the mass flow controllers 50-1 to 50-3 to the inside of the quartz chamber 12. While the etching gas is being supplied, the control unit 40 operates the pump 15 and controls the pressure adjustment mechanism 14 to adjust the inside of the processing chamber 1 to a desired pressure (vacuum level). Note that a configuration may be adopted in which a complexing gas supply unit and a corresponding mass flow controller are provided, and the flow rate of the complexing gas supplied from the mass flow controller to the inside of the quartz chamber 12 is adjusted.

[0032] Furthermore, the control unit 40 operates the DC power supply 31 for electrostatic adsorption to electrostatically adsorb the wafer 2 onto the stage 4, and operates the mass flow controller 50-4 that supplies He gas between the wafer 2 and the stage 4. Based on the temperature distribution information of the wafer 2 calculated by the calculation unit 41 based on the temperature inside the stage 4 measured by the thermocouple thermometer 71 and the spectral intensity information measured by the detector 97 near the center, near the radial middle portion, and near the outer periphery of the wafer 2, the control unit 40 controls the IR lamp power supply 64 and the chiller 38 so that the temperature of the wafer 2 falls within a predetermined temperature range.

[0033] (Time Chart of Etching Method) FIG. 3 is a diagram showing a time chart of the etching method. Specifically, FIG. 3 is a time chart of one cycle (S101 to S108) when a wafer containing SiGe and Ge in its upper layer is etched using plasma processing apparatus 100 according to the flowchart of FIG. 1. The time chart includes a "gas supply" chart 200, a "discharge power" chart 210, a "lamp power" chart 220, a "electrostatic adsorption and rear surface He pressure" chart 230, and a "wafer temperature" chart 240. The five charts are shown with a common horizontal axis (time axis). In the following description, when referring to "gas supply" chart 200, for example, it will be written as "chart 200."

[0034] First, a wafer 2 containing SiGe and Ge in its upper layer to be etched is loaded into the processing chamber 1 through a transfer port (not shown) provided in the processing chamber 1 and mounted on the stage 4. As shown in chart 230, the control unit 40 activates the DC power supply 31 to electrostatically adsorb the wafer 2 to the stage 4 and fix the wafer 2 to the stage 4 (time t0). The control unit 40 also controls the gas supply unit 51 to supply He gas for wafer cooling between the rear surface of the wafer 2 and the stage 4 from the He gas-compatible mass flow controller 50-4, thereby setting the He gas pressure (hereinafter also referred to as "rear surface He pressure") 230 between the rear surface of the wafer 2 and the stage 4 to a predetermined pressure 231. Note that, because the DC power supply 31 is activated when the pressure 231 is set, the electrostatic adsorption and rear surface He pressure are shown on the vertical axis of chart 230 to facilitate conceptual understanding.

[0035] Next, as shown in chart 200, the control unit 40 adjusts the flow rate of hydrogen gas supplied into the processing chamber 1 using the mass flow controller 50-3. The control unit 40 also adjusts the flow rate of Ar gas supplied into the processing chamber 1 using the mass flow controller 50-1 (time t1). In addition to adjusting the hydrogen gas and Ar gas, the control unit 40 also adjusts the aperture of the pressure regulation mechanism 14 to set the pressure inside the processing chamber 1 and the quartz chamber 12 to the target pressure. In this state, as shown in chart 210, the control unit 40 turns on the high-frequency power supply 20 to apply discharge power 211, which is high-frequency power, to the discharge region 3, thereby initiating plasma discharge inside the quartz chamber 12 and generating plasma 10 inside the quartz chamber 12. As shown in chart 220, the control unit 40 also turns on the output of the IR lamp power supply 64 to light the IR lamp 62 (power 221). The IR light emitted from the IR lamp 62 passes through the IR light transmission window 74 and heats the wafer 2. As a result, the wafer temperature rises as shown by temperature 241 in chart 240. In this embodiment, the wafer temperature 241 reaches 200°C 30 seconds after the start of the temperature rise (i.e., corresponding to the time from time t2 to time t1). In this example, the wafer temperature to be reached is set to 200°C, but the wafer temperature 241 to be reached may be set in the range of 100°C to 350°C.

[0036] When the wafer temperature reaches 200° C. (wafer temperature 241), the control unit 40 reduces the output of the IR lamp power supply 64 to power 222 as shown in chart 220, thereby maintaining the temperature of the wafer 2 at a constant temperature 241 for a certain period of time. In this manner, the plasma processing using hydrogen gas is continued with the temperature of the wafer 2 maintained at 200° C. The internal pressure of the processing chamber 1 is 50 Pa, Ar / H ２ The gas flow rate was set to 700 / 200 ccm.

[0037] In this state, H ２A portion of the gas is ionized and dissociated. Neutral gas and radicals that are not ionized in the region and period where the plasma 10 is generated pass through the slit plate 78 and are irradiated onto the wafer 2. The irradiated radicals penetrate into the wafer 2 from the surface of the wafer 2, and a hydrogen-modified layer (hereinafter also referred to as a "surface-modified layer") is generated near the surface of the SiGe film and the Ge film. Due to the effect of the slit plate 78, almost no ions generated in the plasma 10 are incident on the wafer 2. Therefore, the formation of the hydrogen-modified surface layer progresses isotropically, mainly by hydrogen radicals. The thickness of the hydrogen-modified surface layer generated increases depending on the duration of the plasma treatment using hydrogen gas (hereinafter also referred to as the "plasma treatment time"), but it was found that the thickness of the surface-modified layer saturates after 500 seconds. For this reason, H ２ The plasma processing time using the gas was set to, for example, 500 seconds.

[0038] After the plasma processing time required to form a hydrogen surface modified layer has elapsed (time t3), the control unit 40 stops the plasma discharge by turning off the high frequency power supply 20 (discharge power 212), as shown in chart 210. The control unit 40 also stops heating the wafer 2 by turning off the output of the IR lamp power supply 64 (power 223), as shown in chart 220. The control unit 40 also exhausts any gas remaining in the processing chamber 1 using the exhaust mechanism.

[0039] Subsequently, the control unit 40 controls the mass flow controller 50-2 to supply SF 5 into the processing chamber 1 as shown in the chart 200. ６ The flow rate of the gas is adjusted (time t4). The control unit 40 also adjusts the flow rate of the Ar gas supplied into the processing chamber 1 using the mass flow controller 50-1. The control unit 40 also adjusts the opening of the pressure adjustment mechanism 14 to set the pressure inside the processing chamber 1 and the quartz chamber 12 to the target pressure. In this state, the control unit 40 turns on the high frequency power supply 20 and inputs the discharge power 213, as shown in the chart 210, to start a plasma discharge inside the quartz chamber 12, thereby generating a plasma 10 inside the quartz chamber 12. Such SF ６In the plasma processing using gas, the pressure inside the processing chamber 1 and the quartz chamber 12 is 25 Pa, Ar / SF ６ The gas flow rate was set to 800 / 10 ccm.

[0040] In this state, SF ６ A part of the gas is ionized and dissociated. Neutral gas and radicals that are not ionized in the region where the plasma 10 is generated pass through the slit plate 78 and are irradiated onto the wafer 2. These radicals, mainly F radicals, etch the SiGe film and Ge film from the surface of the wafer 2. Due to the effect of the slit plate 78, most of the ions generated in the plasma 10 do not impinge on the wafer 2. Therefore, SF ６ Etching using gas proceeds isotropically mainly by radicals. Due to the effect of the hydrogen-modified layer, etching of SiGe proceeds faster than etching of Ge. The etching amount is SF ６ It was found that the etching selectivity of SiGe to Ge increases depending on the plasma treatment time using the gas, but after a certain time has passed, the etching selectivity of SiGe to Ge begins to decrease. ６ The plasma processing time using the gas was set to, for example, 20 seconds.

[0041] As shown in chart 210, after the plasma processing time required for etching has elapsed (time t5), the control unit 40 turns off the high frequency power supply 20 (discharge power 214) to stop the plasma discharge. The control unit 40 also exhausts gas remaining in the processing chamber 1 using the exhaust mechanism.

[0042] Next, as shown in chart 220, the control unit 40 turns on the output of the IR lamp power supply 64 (time t6), lighting the IR lamp 62 (power 224). The IR light emitted from the IR lamp 62 passes through the IR light transmission window 74 and heats the wafer 2. This causes the wafer temperature to rise to temperature 242, as shown in chart 240. Twenty seconds after the start of the temperature rise, it was detected that the wafer temperature 242 had reached 500°C (time t7). In this example, the wafer temperature 242 was set to 500°C, but the wafer temperature 242 may be 400°C or higher.

[0043] Although the wafer 2 has been described as being heated while placed on the stage 4, the wafer 2 may be raised from the stage 4 using lift pins or the like and irradiated with IR light (electromagnetic waves) while not in thermal contact with the stage 4. This suppresses heat transfer from the wafer 2 to the stage 4, thereby enabling the wafer 2 to be heated to the desired temperature in a shorter time. In this case, the temperature of the wafer 2 may be measured using light emitted from the IR lamp 62, transmitted through the wafer 2, and reaching the optical fiber 92-2. The power ratio of the IR lamps 62-1, 62-2, and 62-3 may be controlled based on the radial temperature distribution within the surface of the wafer 2. As shown in chart 220, the lamp power is maintained at power 224, but the power 224 may be changed to maintain the wafer temperature 242.

[0044] Thereafter, the control unit 40 turns off the output of the IR lamp power supply 64 (power 225, time t8) as shown in the chart 220, thereby stopping the heating of the wafer 2.

[0045] Next, the control unit 40 controls the mass flow controller 50-1 for supplying Ar gas and the mass flow controller 50-4 for supplying He gas to supply Ar gas into the processing chamber 1, while supplying He gas between the backside of the wafer 2 and the stage 4 as shown in chart 230. The pressure of the He gas between the backside of the wafer 2 and the stage 4 is set to a predetermined pressure 232. As shown in chart 240, the cooled wafer temperature 243 (time t9) is cooled to 100°C or below, and the cooling time is 30 seconds. The supply of He gas to the backside of the wafer is then stopped, and the valve 52 is opened to make the pressure on the backside of the wafer 2 approximately the same as the pressure in the processing chamber 1. By venting the He gas from the backside of the wafer 2, the pressure of the He gas between the backside of the wafer 2 and the stage 4 in FIG. 3 becomes pressure 233. This completes the process. In this embodiment, both the hydrogen plasma process and the etching by plasma process using an F-based gas proceed isotropically.

[0046] 1 and 3, step S101 in FIG. 1 corresponds to the process performed between time t0 and time t3 in FIG. 3. Steps S102 and S103 in FIG. 1 correspond to the process performed between time t3 and time t4 in FIG. 3. Steps S104 and S105 in FIG. 1 correspond to the process performed between time t4 and time t5 in FIG. 3. Step S106 in FIG. 1 corresponds to the process performed between time t5 and time t6 in FIG. 3. Step S107 in FIG. 1 corresponds to the process performed between time t6 and time t8 in FIG. 3. Step S108 in FIG. 1 corresponds to the process performed between time t8 and time t9 in FIG. 3. The cycle from time t1 to time t9 is repeated until a desired etching amount is obtained for the SiGe film.

[0047] FIG. 4 shows the results of etching SiGe and Ge according to the process flow shown in FIGS. 1 and 3 . FIG. 4 is a graph showing the dependence of the SiGe-to-Ge etching selectivity on wafer temperature during hydrogen plasma processing. The wafer temperature was varied in step S101 of FIG. 1 . The horizontal axis represents the wafer temperature during the hydrogen gas plasma processing, and the vertical axis represents the etching selectivity. Here, the etching selectivity refers to the ratio of the amount of SiGe etched to the amount of Ge etched. The hydrogen gas plasma processing time was 500 seconds. When the wafer temperature during hydrogen gas plasma processing was 50° C. or 400° C., the etching selectivity was less than 10. However, when the wafer temperature was 100° C. or higher and 350° C. or lower, the etching selectivity was 10 or higher.

[0048] Figure 5 shows another result of etching SiGe and Ge according to the process flow shown in Figures 1 and 3. Figure 5 is a graph showing the dependence of the SiGe to Ge etching selectivity on hydrogen plasma processing time. The processing was performed by varying the plasma processing time using hydrogen gas in step S101 of Figure 1. The horizontal axis shows the plasma processing time using hydrogen gas, and the vertical axis shows the etching selectivity. The wafer temperature was fixed at 200°C. The maximum etching selectivity of 25 was achieved when the plasma processing time using hydrogen gas was 500 seconds, and the etching selectivity decreased whether the processing time was shorter or longer.

[0049] 6A and 6B are cross-sectional views illustrating an example of a device structure to which an embodiment of the present disclosure is applied, and a state in which the device has been etched. Fig. 6A shows the state of a wafer 2 before etching, and Fig. 6B shows the state of the wafer 2 after etching. Selective etching of SiGe relative to Ge is applied to a device having a structure such as that shown in Fig. 6A. That is, as shown in Fig. 6A, in the state before etching, Ge films 302 and SiGe films 303 are alternately stacked on a wafer 2, and SiO ２ A hard mask layer 301 made of a SiGe film or the like is formed on the wafer 2. A trench Tr is also formed in advance. The hard mask layer 301 is used as an etching mask. When the etching method of this embodiment is performed on the wafer 2, it becomes possible to selectively etch the SiGe film 303 relative to the Ge film 302. As shown in FIG. 6B, the SiGe film 303 facing the trench Tr is selectively etched, resulting in a state in which so-called side etching has been performed.

[0050] (Operations and Effects) As described above, according to the present invention, it becomes possible to etch SiGe with a high selectivity to Ge.

[0051] Furthermore, when a halogen-based single gas is used, the etching rates have a relationship of Si<SiGe<Ge, so when attempting to selectively etch a SiGe film, pretreatment to protect the Ge film is required. In contrast, the technology disclosed herein can achieve a large etching selectivity (SiGe film / Ge film), making it possible to perform efficient etching without the need for treatment to protect the Ge film.

[0052] The following are some non-limiting aspects of the present invention. (Aspect 1) A sample processing method comprising: placing a substrate to be processed, which includes silicon germanium and germanium, with the germanium content being greater than that of silicon, in a processing chamber inside a container; processing the substrate by supplying a processing gas containing H2 gas in an excited state while maintaining the temperature of the substrate at 100°C or higher and 350°C or lower; and then selectively etching the silicon germanium relative to the germanium using a processing gas containing F. (Aspect 2) A sample processing method according to Aspect 1, wherein the processing gas containing F contains any of SF6, CF4, and NF3. (Aspect 3) A sample processing method according to any of Aspects 1 and 2, wherein the etching process using the processing gas containing F is performed at a temperature of the substrate at 100°C or lower. (Aspect 4) A method for processing a sample according to any one of Aspects 1 to 3, characterized in that after the etching process, the sample is heated to 400°C or higher by electromagnetic waves irradiated from an infrared lamp or a halogen lamp arranged in the processing chamber. (Aspect 5) A method for processing a sample according to any one of Aspects 1 to 4, characterized in that the processing gas containing F contains SF. (Aspect 6) A method for processing a sample according to any one of Aspects 1 to 5, characterized in that the processing gas containing excited H gas contains hydrogen radicals. (Aspect 7) A method for processing a sample according to any one of Aspects 1 to 6, characterized in that in the processing step, the sample is placed on an upper surface of a refrigerant flow channel arranged at a lower part of the processing chamber, through which a refrigerant at a predetermined temperature flows, and the temperature is regulated.

[0053] 1: Processing chamber, 2: Wafer, 3: Discharge area, 4: Wafer stage, 5: Shower plate, 6: Top plate, 10: Plasma, 11: Base chamber, 12: Quartz chamber, 14: Pressure adjustment mechanism, 15: Pump, 16: Vacuum exhaust piping, 17: Gas dispersion plate, 20: High frequency power supply, 22: Matching box, 25: High frequency cut filter, 30: Electrostatic adsorption electrode, 31: DC power supply for electrostatic adsorption, 34: ICP coil, 38: Chiller, 40: Control unit, 41: Calculation unit, 45: Tank, 46: Heater, 47: Complexing gas supplier, 50: Ma flow controller, 51: gas supply unit, 52, 53, 54: valve, 60: container, 62: IR lamp, 63: reflector, 64: IR lamp power supply, 70: thermocouple, 71: thermocouple thermometer, 74: IR light transmission window, 75: gas flow path, 78: slit plate, 81: O-ring, 92: optical fiber, 93: external IR light source, 94: optical path switch, 95: optical distributor, 96: spectroscope, 97: detector, 98: optical multiplexer, 100: plasma processing apparatus, hard mask layer: 301, Ge film: 302, SiGe film: 303

Claims

1. An etching method for etching a silicon germanium film of a film structure including a silicon germanium film and a germanium film formed on a surface of a wafer, the method comprising: a step of supplying hydrogen radicals to the film structure while the wafer is heated, and forming a denatured layer on the surface of the film structure; and a step of cooling the wafer to 0°C or room temperature after the step of forming the denatured layer, and supplying a gas including sulfur hexafluoride or sulfur hexafluoride and argon to the denatured layer, thereby etching the silicon germanium film.

2. An etching method according to claim 1, further comprising the step of heating the wafer after the etching step to remove hydrogen from the surface of the film structure.

3. The etching method according to claim 2, wherein in the step of removing hydrogen, the wafer is heated by irradiating it with electromagnetic waves from a lamp.

4. An etching method according to any one of claims 1 to 3, wherein the wafer is heated to 150°C to 350°C in the step of forming the modified layer.

5. An etching method according to any one of claims 2, 3, claim 4 which cites claim 2, and claim 4 which cites claim 3, wherein a cycle including the steps of forming the denatured layer, the etching step, and the step of removing hydrogen is repeated a number of times.