Substrate processing method and substrate processing device

Abstract

A method for processing a substrate is a method for processing a substrate on which silicon layers and silicon germanium layers are alternately stacked, the method comprising the following steps: using a gas containing fluorine and oxygen that has been radicalized by remote plasma to selectively oxidize the surface of the exposed surface of the silicon germanium layer to form an oxide film; and removing the formed oxide film.

Description

Technical Field

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus. Background Art

[0002] Patent Document 1 discloses a method for etching a substrate comprising silicon and silicon germanium. According to the method described in Patent Document 1, the etching gas system is set to F2 gas and NH3 gas, and the ratio of F2 gas to NH3 gas is varied, thereby achieving selective etching of silicon germanium relative to silicon, and vice versa.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-143781 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The technology according to the present disclosure appropriately performs selective etching of a silicon germanium layer with respect to a silicon layer in processing a substrate in which a silicon layer and a silicon germanium layer are alternately stacked.

[0008] Solutions for solving problems

[0009] One embodiment of the present disclosure is a method for processing a substrate having alternately stacked silicon layers and silicon germanium layers, comprising the following steps: using a gas containing fluorine and oxygen that has been radicalized by remote plasma to selectively oxidize the surface of the exposed surface of the silicon germanium layer to form an oxide film; and removing the formed oxide film.

[0010] Effects of the Invention

[0011] According to the present disclosure, selective etching of the silicon germanium layer with respect to the silicon layer is appropriately performed in processing a substrate in which silicon layers and silicon germanium layers are alternately stacked. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is an explanatory diagram schematically showing a conventional wafer processing situation.

[0013] Figure 2 This is a flowchart showing the main steps of wafer processing according to this embodiment.

[0014] Figure 3 It is an explanatory diagram schematically showing a state of wafer processing according to this embodiment.

[0015] Figure 4 It is a longitudinal cross-sectional view showing an example of the structure of a plasma processing apparatus.

[0016] Figure 5 Graph showing the relationship between plasma oxidation treatment time and oxidation amount.

[0017] Figure 6 It is a longitudinal cross-sectional view showing an example of the structure of an etching processing apparatus.

[0018] Figure 7 It is an explanatory diagram showing an example of the result of wafer processing according to this embodiment.

[0019] Figure 8 It is an explanatory diagram schematically showing a state of wafer processing according to another method. DETAILED DESCRIPTION

[0020] In semiconductor devices, films containing silicon are widely used for various purposes. For example, silicon germanium (SiGe) films and silicon (Si) films are used for gate electrodes and channel materials. In addition, in the past, in the manufacturing process of GAA (Gate allaround) transistors such as nanosheets or nanowires, Figure 1 As shown, the following steps are performed sequentially: (a) stacking of a SiGe layer and a Si layer on a substrate (wafer W); (b) selective etching of the SiGe layer; (c) embedding of an inner spacer (IS) as an insulating film; and (d) etching of excess inner spacers. The insulating film embedded in step (c) serves to reduce parasitic capacitance between the metal gate and the source / drain electrodes, which will be embedded in a subsequent step.

[0021] The technology disclosed in Patent Document 1 is a method for selectively etching the (b) SiGe layer. Specifically, F2 gas and NH3 gas are supplied as etching gases to a substrate disposed in a chamber, and the volume ratio of the F2 gas and NH3 gas is controlled, thereby enabling selective etching of the SiGe layer relative to the Si layer.

[0022] Furthermore, in such selective etching of SiGe layers, it is necessary to uniformly control the etching amount of each stacked SiGe layer. However, in the etching method described in Patent Document 1, it is sometimes difficult to uniformly control the etching amount of each SiGe layer by adjusting the etching conditions. In other words, there is room for improvement in conventional selective etching methods for SiGe films.

[0023] The technology disclosed herein was developed in light of the above circumstances and, in processing a substrate having alternately stacked silicon and silicon germanium layers, appropriately performs selective etching of the silicon germanium layer relative to the silicon layer. The following describes wafer processing as a substrate processing method according to this embodiment with reference to the accompanying drawings. Elements having substantially the same functional structure are denoted by the same reference numerals throughout this specification and the accompanying drawings to omit repeated descriptions.

[0024] Figure 2 : is a flow chart showing the main steps of selective etching of the SiGe layer according to this embodiment. Figure 3 In the following description, the exposed end faces (side faces) of the alternately arranged SiGe and Si layers are sometimes referred to as "exposed faces" of the SiGe and Si layers.

[0025] like Figure 2 and Figure 3 As shown, in the selective etching of the SiGe layer according to this embodiment, the following steps are performed: an oxide film Ox ( Figure 2 Step T1); and removing the formed oxide film Ox ( Figure 2 Step T2). Figure 3 As shown in (e), these steps T1 and T2 are repeated in the depth direction from the exposed surface of the SiGe layer until the desired etching amount is obtained ( Figure 2 Branch C1).

[0026] After that, when the desired etching amount is obtained for the SiGe layer, the oxide film Ox remaining on the surface of the wafer W is removed. More specifically, the oxide film Ox remaining on the surface of the exposed surface of the Si layer and the SiGe layer is removed. Specifically, for example, the following treatment is performed: a COR (Chemical Oxide Removal) treatment is performed to transform the oxide film Ox to generate a reaction product. Figure 2 and PHT (Post Heat Treatment: post-heat treatment) treatment ( Figure 2 Step T4).

[0027] Next, Figure 2 and Figure 3 The detailed method of each step shown is described.

[0028] <Step T1: Formation of Oxide Film>

[0029] exist Figure 2 In step T1, the exposed surface of the SiGe layer is selectively oxidized using a plasma processing apparatus 1 as a plasma processing unit, thereby forming an oxide film Ox (eg, SiO2 film) in a depth direction from the exposed surface of the SiGe layer.

[0030] like Figure 4 As shown, the plasma processing apparatus 1 includes a sealed processing container 10 for accommodating wafers W. The processing container 10 is made of, for example, aluminum or an aluminum alloy, and has an open top. The top of the processing container 10 is sealed by a lid 10a, which serves as a top portion. A loading / unloading port (not shown) for the wafers W is provided on a side of the processing container 10. The loading / unloading port is connected to the exterior of the plasma processing apparatus 1 through the loading / unloading port. The loading / unloading port is freely openable and closable by a gate valve (not shown).

[0031] The interior of the processing container 10 is partitioned by a partition plate 11 into an upper plasma generation space P and a lower processing space S. That is, the plasma processing apparatus 1 according to this embodiment is configured as a remote plasma processing apparatus in which the plasma generation space P and the processing space S are separated.

[0032] The partition plate 11 includes at least two plate-like members 12 and 13 arranged to overlap with each other from the plasma generation space P toward the processing space S. The plate-like members 12 and 13 each have slits 12a and 13a formed therethrough in the overlapping direction. Furthermore, the slits 12a and 13a are arranged so as not to overlap when viewed from above. As a result, the partition plate 11 functions as a so-called ion trap, which prevents ions in the plasma from penetrating and reaching the processing space S when plasma is generated in the plasma generation space P. More specifically, the labyrinthine structure, in which the slits 12a and 13a are arranged so as not to overlap, prevents the movement of anisotropically migrating ions while allowing isotropically migrating radicals to pass through.

[0033] The plasma generating space P includes a gas supply unit 20 for supplying a processing gas into the processing container 10 and a plasma generating unit 30 for converting the processing gas supplied into the processing container 10 into plasma.

[0034] The gas supply unit 20 is connected to a plurality of gas supply sources (not shown) to supply process gases including a fluorine-containing gas (e.g., NF3 gas), an oxygen-containing gas (e.g., O2 gas), and a dilution gas (e.g., Ar gas) into the processing container 10. The type of process gas supplied to the gas supply unit 20 is not limited as long as it can form an oxide film Ox on the surface of the exposed surface of the SiGe layer.

[0035] The gas supply unit 20 is provided with a flow rate regulator (not shown) for regulating the supply amount of the processing gas to the plasma generation space P. The flow rate regulator includes, for example, an on-off valve and a mass flow controller.

[0036] The plasma generation unit 30 is configured as an inductively coupled device using an RF antenna. The lid 10a of the processing container 10 is formed, for example, from a quartz plate and serves as a dielectric window. An RF antenna 31 is formed above the lid 10a for generating inductively coupled plasma in the plasma generation space P of the processing container 10. The RF antenna 31 is connected to a high-frequency power supply 33 via a matching unit 32 having a matching circuit for matching the impedance between the power supply side and the load side. The high-frequency power supply 33 outputs high-frequency power at a fixed frequency (typically above 13.56 MHz) suitable for plasma generation at an arbitrary output value.

[0037] The processing space S includes a mounting table 40 on which the wafer W is mounted in the processing container 10 , and an exhaust unit 50 for exhausting a processing gas in the processing container 10 .

[0038] The mounting table 40 includes an upper table 41 for mounting the wafer W, and a lower table 42 fixed to the bottom surface of the processing container 10 and supporting the upper table 41. A temperature control mechanism 43 for controlling the temperature of the wafer W is provided inside the upper table 41.

[0039] The exhaust unit 50 is connected to an exhaust mechanism (not shown), such as a vacuum pump, via an exhaust pipe provided at the bottom of the processing container 10. Furthermore, an automatic pressure control valve (APC) is provided in the exhaust pipe. The pressure within the processing container 10 is controlled by the exhaust mechanism and the APC.

[0040] The plasma processing apparatus 1 described above is provided with a control device 60 serving as a control unit. The control device 60 is, for example, a computer equipped with a CPU, memory, etc., and includes a program storage unit (not shown). The program storage unit stores a program for controlling the processing of wafers W in the plasma processing apparatus 1. The program can be recorded on a computer-readable storage medium H and installed from the storage medium H into the control device 60.

[0041] The plasma processing apparatus 1 is configured as described above. Next, a description will be given of plasma oxidation processing (formation of an oxide film Ox) performed using the plasma processing apparatus 1. Si layers and SiGe layers are previously formed alternately on the wafer W loaded into the plasma processing apparatus 1.

[0042] First, if Figure 3As shown in (a), a wafer W having Si layers and SiGe layers formed thereon in an alternating manner is placed on a mounting table 40. When the wafer W is loaded into the plasma processing apparatus 1, as shown in FIG. Figure 3 As shown in (b), an oxide film Ox is formed on the surface of the exposed surface of the SiGe layer.

[0043] Specifically, when a wafer W is placed on the mounting table 40, a processing gas (NF3 gas, O2 gas, and Ar gas in this embodiment) is supplied from the gas supply unit 20 to the plasma generation space P, and high-frequency power is supplied to the RF antenna 31, thereby generating inductively coupled plasma, i.e., plasma containing oxygen and fluorine. In other words, the generated plasma contains oxygen radicals (O*) and fluorine radicals (F*).

[0044] Here, it is preferred that the flow rate of the processing gas supplied to the plasma generation space P is O2:NF3 = 100-2500 sccm:1-20 sccm. More preferably, the volume ratio of NF3 gas to O2 gas is greater than or equal to 0.1 vol% and less than or equal to 1.0 vol%. Furthermore, it is preferred that the output of the high-frequency power in the plasma generation space P is 100 W to 1000 W, and the internal pressure (vacuum level) of the plasma generation space P is 6.67 Pa to 266.6 Pa (50 mTorr to 2000 mTorr). Furthermore, at this time, the temperature of the wafer W placed on the mounting table 40 is preferably controlled to 0°C to 120°C, and more preferably to 15°C to 100°C.

[0045] The plasma generated in the plasma generation space P is supplied to the processing space S via the partition plate 11. Here, since a maze structure is formed on the partition plate 11 as described above, only the free radicals generated in the plasma generation space P pass through and reach the processing space S. When the free radicals pass through and reach the processing space S, the impurities attached to the surface of the wafer W are removed by F*. Next, by acting on the SiGe layer with O*, the exposed surface of the SiGe layer is oxidized, thereby forming an oxide film Ox (SiO2 film) on the exposed surface. Here, in the oxidation of the SiGe layer, O2 replaces Ge to combine with Si, whereby Ge is vaporized (for example, Ge2F4, GeOF2) and scattered. The vaporized Ge is transported to the exhaust section 50 by, for example, F* or Ar* and recovered.

[0046] In the plasma oxidation process according to this embodiment, oxidation occurs not only on the exposed surface of the SiGe layer but also on the exposed surface of the Si layer, forming an oxide film Ox (SiO2 film). However, the inventors of the present invention conducted extensive research and discovered that the oxidation rate of the SiGe layer is faster than that of the Si layer (e.g., approximately 10 times). In other words, in the plasma oxidation process according to this embodiment, the thickness of the oxide film Ox formed relative to the Si layer is smaller (e.g., approximately 1 / 10) than the thickness of the oxide film Ox formed relative to the SiGe layer, thereby enabling appropriate selective oxidation of the SiGe layer.

[0047] Furthermore, in the plasma oxidation process according to this embodiment, as described above, only isotropically migrating radicals are allowed to pass through and reach the processing space S. Therefore, the thickness of the oxide film Ox formed by the plasma oxidation process is uniform within the surface of the wafer W and uniform across each stacked SiGe layer. In other words, it is possible to reduce variations in the thickness of the formed oxide film Ox, and in particular, it is possible to reduce variations in the thickness of the oxide film Ox formed on the exposed surface of each stacked SiGe layer.

[0048] In addition, the plasma oxidation process involved in this embodiment is a process in which the amount of oxidation of the SiGe layer within the processing time of the plasma processing device 1, in other words, the thickness of the formed oxide film Ox from the exposed surface is saturated. Figure 5 As shown, the thickness of the oxide film Ox formed by one plasma oxidation treatment is, for example, approximately 10 nm.

[0049] also, Figure 5 The saturated oxidation amount of the SiGe layer (the saturated thickness of the oxide film Ox formed) is determined by the depth at which free radicals reach the SiGe layer. In other words, by controlling the internal pressure of the plasma processing apparatus 1 to control the depth at which free radicals reach the SiGe layer, the saturated oxidation amount of the SiGe layer can be controlled. Specifically, for example, by increasing the internal pressure of the plasma processing apparatus 1, the saturated oxidation amount, i.e., the thickness of the formed oxide film Ox, can be increased. Alternatively, by decreasing the internal pressure of the plasma processing apparatus 1, the saturated oxidation amount, i.e., the thickness of the formed oxide film Ox, can be reduced.

[0050] Furthermore, when the plasma processing apparatus 1 is operated for a long time, there is a risk that the radicals supplied to the processing space S will have a greater effect on the Si layer, thereby increasing the amount of Si layer oxidation, that is, the thickness of the oxide film Ox formed on the surface of the exposed surface. As will be described later, the selective etching of the SiGe layer according to this embodiment is performed by removing the formed oxide film Ox. However, when the amount of Si layer oxidation increases in this manner, the selectivity of the SiGe layer (the ratio of the amount of SiGe layer oxidation to the amount of Si layer oxidation) decreases because the saturation of the SiGe layer oxidation does not depend on the processing time as described above.

[0051] Therefore, in order to suppress the influence of these radicals on the Si layer, the plasma oxidation process according to this embodiment preferably stops the supply of process gas to the processing container 10 before the oxidation amount of the SiGe layer reaches the saturation oxidation amount. This can appropriately suppress a decrease in the selectivity of the SiGe layer. Furthermore, even in the case where the supply of process gas is stopped before the oxidation amount of the SiGe layer reaches the saturation oxidation amount, the oxidation of the SiGe layer can still progress due to the process gas (plasma) remaining in the processing container 10, thereby allowing the oxidation amount of the SiGe layer to appropriately approach the saturation oxidation amount.

[0052] <Step T2: Removal of Oxide Film>

[0053] When the oxide film Ox is formed on the surface layer of the exposed surface of the SiGe layer, the oxide film Ox formed in step T1 is then removed by, for example, gas etching using the etching apparatus 101 as a removal unit. Figure 6 1 is a longitudinal sectional view schematically showing the structure of an etching processing apparatus 101 for removing the oxide film Ox.

[0054] like Figure 6 As shown, the etching processing apparatus 101 includes a sealed processing container 110 for accommodating wafers W. A processing space S is formed within the processing container 110. A loading / unloading port (not shown) for the wafers W is provided on the side of the processing container 110, and the loading / unloading port is connected to the outside of the etching processing apparatus 101 through the loading / unloading port. The loading / unloading port is configured to be freely openable and closable by a gate valve (not shown). In addition, the etching processing apparatus 101 is provided with a loading table 120 for placing the wafers W in the processing container 110, a supply unit 130 for supplying etching gas into the processing space S, and an exhaust unit 140 for exhausting the etching gas in the processing container 110.

[0055] The mounting table 120 is fixedly mounted on the bottom surface of the processing container 110 , and has a wafer holding surface formed on its upper surface for holding the wafer W. A temperature control mechanism 121 is provided inside the mounting table 120 for controlling the temperature of the wafer W held on the wafer holding surface.

[0056] The supply unit 130 includes a plurality of gas supply sources 131 for supplying fluorine-containing gas (e.g., HF gas), ammonia (NH 3 ) gas, diluent gas (e.g., Ar gas), and inert gas (e.g., N 2 gas) as etching gases into the interior of the processing container 110, and a shower head 132 disposed on the top of the processing container 110 and having a plurality of nozzles for spraying the processing gases into the processing space S. The gas supply sources 131 are connected to the interior of the processing container 110 via supply pipes connected to the shower head 132.

[0057] Furthermore, the supply unit 130 is provided with a flow rate regulator 133 for regulating the amount of etching gas supplied to the interior of the processing container 110. The flow rate regulator 133 includes, for example, an on-off valve and a mass flow controller.

[0058] The exhaust unit 140 is connected to an exhaust mechanism (not shown), such as a vacuum pump, via an exhaust pipe disposed at the bottom of the processing container 110. An automatic pressure control valve (APC) is also provided in the exhaust pipe. The pressure within the processing container 110 is controlled by the exhaust mechanism and the APC.

[0059] The etching apparatus 101 is provided with a control device 150 as a control unit. The control device 150 is, for example, a computer equipped with a CPU, memory, etc., and includes a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the wafer W in the etching apparatus 101. The program can be recorded on a computer-readable storage medium H and installed from the storage medium H into the control device 150.

[0060] Furthermore, the control device 150 provided in the etching apparatus 101 may be shared with the control device 60 provided in the plasma processing apparatus 1 . That is, the etching apparatus 101 may be connected to the control device 60 provided in the plasma processing apparatus 1 instead of being connected to the control device 150 .

[0061] The etching apparatus 101 is configured as described above. Next, the gas etching process (removal of the oxide film Ox) performed using the etching apparatus 101 will be described. Furthermore, the wafer W loaded into the etching apparatus 101 has an oxide film Ox formed on the exposed surface of the SiGe layer in advance in step T1 described above.

[0062] First, if Figure 3 As shown in FIG. 1 (b), a wafer W having an oxide film Ox formed on the surface of the exposed surface of the SiGe layer is placed on the mounting table 120. Figure 3 As shown in (c), the oxide film Ox of the wafer W loaded into the etching processing apparatus 101 is removed.

[0063] Specifically, when wafer W is placed on mounting table 120 and the interior of processing container 110 is sealed, a dilution gas (Ar gas) and an inert gas (N2 gas) are first supplied to processing space S. At this time, the internal pressure of processing space S is controlled to, for example, 30 mTorr to 5000 mTorr, and the temperature of wafer W on mounting table 120 is controlled to, for example, 0°C to 150°C.

[0064] When the internal pressure of the processing space S and the temperature of the wafer W reach the desired state, fluorine-containing gas (HF gas) and NH3 gas are then supplied to the processing space S. At this time, the flow rates of the HF gas and NH3 gas supplied to the processing space S are controlled to, for example, 10 to 1000 sccm, respectively, and the flow rates of the Ar gas and N2 gas are controlled to, for example, 0 sccm to 1000 sccm, respectively. Furthermore, by supplying HF gas and NH3 gas to the processing space S in this manner, gas etching of the oxide film Ox formed on the surface layer of the exposed surface of the SiGe layer begins.

[0065] Here, in the gas etching process according to this embodiment, the oxide film Ox formed in step T1 is selectively removed based on the difference in etching rate between the oxide film Ox (SiO2 film) and the Si layer and the SiGe layer. In other words, in step T1, the oxide film Ox is selectively formed on the SiGe layer due to the difference in oxidation rate between the Si layer and the SiGe layer. Therefore, in the gas etching process according to this embodiment, the SiGe layer can be selectively etched and removed appropriately.

[0066] Furthermore, as described above, in the plasma oxidation process in step T1, the thickness of the oxide film Ox can be made uniform within the surface of the wafer W and uniform in each stacked SiGe layer. In other words, in the gas etching process according to this embodiment, the SiGe layer can be removed uniformly within the surface of the wafer W and uniformly in each stacked SiGe layer.

[0067] In addition, in the plasma oxidation treatment in step T1, as Figure 5As shown, the saturation of the thickness of the oxide film Ox formed by a single plasma oxidation process does not depend on the process time. In other words, the etching amount of the SiGe layer in a single gas etching process saturates in accordance with the formed thickness of the oxide film Ox, making it easy to control the etching amount of the SiGe layer. In addition, in this case, the thickness of the oxide film Ox can be controlled by the internal pressure of the plasma processing apparatus 1 as described above, so the etching amount of the SiGe layer can be more appropriately controlled.

[0068] <Branch C1: Repeated Processing of Oxide Film Formation and Removal>

[0069] The formation of the oxide film Ox involved in this embodiment (step T1) and the removal of the oxide film Ox (step T2), that is, the removal of the SiGe layer, are performed as described above. Figure 5 As shown, the saturation of the SiGe layer oxidation amount (SiGe layer etching amount) involved in this embodiment does not depend on the plasma processing time. In other words, the desired SiGe layer etching amount may not be achieved by forming and removing the oxide film Ox in one step. Therefore, in the selective etching method of the SiGe layer involved in this embodiment, the SiGe layer is etched and removed to the desired depth by repeating a wafer processing cycle including forming (step T1) and removing (step T2) the oxide film Ox.

[0070] In other words, in this embodiment, the number of cycles of wafer processing to be repeated is determined based on the total etching amount of the required SiGe layer.

[0071] In this manner, even when a series of wafer processing cycles are repeated, the SiGe layer etching amount in each cycle is consistent with the saturated oxidation amount of the SiGe film, making it easy to control the total SiGe layer etching amount. Furthermore, in this case, the saturated oxidation amount of the SiGe film is controlled by the internal pressure of the plasma processing apparatus 1 as described above, thereby enabling more appropriate control of the total SiGe layer etching amount. Furthermore, since the total SiGe layer etching amount can be appropriately controlled in this manner, the line width of the SiGe layer after the selective etching of the SiGe layer, i.e., the channel width formed in the subsequent process, can be controlled to any desired size.

[0072] When the desired total etching amount of the SiGe layer is achieved by repeating the cycle of oxide film formation and removal, the oxide film Ox remaining on the surface of the wafer W is removed before the wafer W is transferred to the next process. More specifically, the oxide film Ox remaining on the exposed surface of the Si layer and SiGe layer is removed. The method for removing the oxide film Ox is not particularly limited, and can be performed, for example, by dry etching or wet etching. However, the following description uses the case where the wafer W is subjected to a COR process and a PHT process in sequence as an example.

[0073] <Step T3: Deterioration of Oxide Film (Formation of Reaction Products)>

[0074] exist Figure 2 In step T3, a COR treatment apparatus as a removal unit is used to allow etching gas to act on the oxide film Ox remaining on the exposed surface of the Si layer and the SiGe layer, thereby degenerating the oxide film Ox to generate a reaction product (COR treatment).

[0075] The COR processing device (not shown) has, for example, Figure 6 The COR processing apparatus 101 shown in FIG. 1 has a similar structure to the etching apparatus 101 shown in FIG. Specifically, the COR processing apparatus includes, for example, a processing container having a processing space S formed therein, a loading table for loading wafers W within the processing container, a supply unit for supplying etching gas to the processing space S, and an exhaust unit for exhausting the processing gas within the processing container. In other words, the COR processing according to this embodiment can also be performed in the etching apparatus 101 performing the gas etching process in step T2.

[0076] In the COR process of this embodiment, wafer W, after selective etching of the SiGe layer in steps T1 and T2, is first placed on a mounting table. Next, a dilution gas (Ar gas) and an inert gas (N2 gas) are supplied into a sealed processing container. The pressure within the processing container is controlled to, for example, 30 mTorr to 5000 mTorr. The temperature of wafer W on the mounting table is controlled to, for example, 0°C to 150°C.

[0077] When the internal pressure of the processing space S and the temperature of the wafer W reach the desired state, a fluorine-containing gas (HF gas) and NH3 gas are then supplied to the processing space S. At this time, the flow rates of the HF gas and NH3 gas supplied into the processing space S are controlled to, for example, 50 sccm to 500 sccm, respectively, and the flow rates of the Ar gas and N2 gas are controlled to, for example, 100 sccm to 600 sccm, respectively. Furthermore, by allowing the HF gas and NH3 gas supplied to the processing space S to act on the oxide film Ox remaining on the surface of the wafer W, the oxide film Ox is transformed into an ammonium fluoride-based compound as a reaction product.

[0078] <Step T4: Sublimation of Reaction Product>

[0079] When the oxide film Ox is altered in step T3 , a PHT treatment apparatus serving as a removal unit is then used to sublime a reaction product (ammonium fluoride-based compound) generated by the alteration of the oxide film Ox (PHT treatment).

[0080] The PHT processing apparatus (not shown) has, for example, a structure similar to that of a COR processing apparatus. Specifically, the PHT processing apparatus includes, for example, a processing container defining a processing space S, a loading platform for placing wafers W within the processing container, a supply unit for supplying etching gas to the processing space S, and an exhaust unit for exhausting the processing gas from the processing container. In other words, the PHT processing according to this embodiment can also be performed in the same COR processing apparatus that performs the COR processing in step T3. Alternatively, the removal of the oxide film Ox in step T2, the COR processing in step T3, and the PHT processing in step T4 can also be performed separately in the same etching processing apparatus 101.

[0081] In the PHT process involved in this embodiment, first, the wafer W that has been subjected to the COR process in step T3 is placed on the mounting table. Then, an inert gas (N2 gas) is supplied as a processing gas to the interior of the sealed processing container, and the temperature of the wafer W on the mounting table is controlled to, for example, above 85°C. The ammonium fluoride-based compound, which is a reaction product generated in the COR process, is heated and sublimated. That is, by raising the temperature of the wafer W in this way, the ammonium fluoride-based compound generated in the COR process of step T3, that is, the oxide film Ox after deterioration, can be sublimated and removed. In addition, the sublimated reaction product is recovered in the exhaust unit 50, for example, together with the processing gas (N2 gas).

[0082] Furthermore, the modification of the oxide film Ox in step T3 and the sublimation of the reaction product generated by the modification of the oxide film Ox in step T4 can be repeated until the ammonium fluoride-based compound as the reaction product is removed. Furthermore, when the oxide film Ox remaining on the surface of the wafer W, particularly on the exposed surface of the Si layer and the SiGe layer, is removed in this manner, the series of selective etching of the SiGe layer according to this embodiment is completed.

[0083] <Effects of Wafer Processing According to the Present Embodiment>

[0084] According to this embodiment, by using a process gas that has been radicalized by remote plasma, an oxide film Ox can be formed uniformly on the SiGe layer within the surface of the wafer W and uniformly across each stacked SiGe layer. Furthermore, by removing the oxide film Ox thus formed and etching the SiGe layer, the etching amount of the SiGe layer can be made uniform within the surface of the wafer W and uniform across each stacked SiGe layer. In other words, it is possible to reduce variations in the etching amount of each stacked SiGe layer.

[0085] According to this embodiment, the SiGe layer can be selectively oxidized by utilizing the difference in oxidation rate between the Si layer and the SiGe layer, and the oxide film Ox can be selectively etched by utilizing the difference in etching rate between the oxide film Ox (SiO2 film) and the Si layer and the SiGe layer. In other words, according to this embodiment, the SiGe layer can be selectively etched appropriately.

[0086] Furthermore, according to the plasma oxidation process of this embodiment, the saturation of the thickness of the oxide film Ox is not dependent on the processing time, making it possible to easily control the amount of SiGe layer etched as the oxide film Ox is removed. Furthermore, in this case, the thickness of the oxide film Ox is controlled by the internal pressure of the plasma processing apparatus performing the plasma oxidation process, thereby enabling more appropriate control of the amount of SiGe layer etched.

[0087] Furthermore, according to this embodiment, by repeating the formation of the oxide film Ox on the surface of the exposed surface of the SiGe layer and the removal of the formed oxide film Ox, the SiGe layer can be easily removed with a desired total etching amount. In addition, by controlling the thickness of the oxide film Ox by the internal pressure of the plasma processing device performing the plasma oxidation process, the total etching amount of the SiGe layer can be more appropriately controlled.

[0088] Furthermore, in the above embodiment, the oxide film Ox (SiO2 film) formed on the surface of the exposed surface of the SiGe layer is removed by gas etching using a fluorine-containing gas (HF gas) and ammonia (NH3) gas. However, the method for removing the oxide film Ox is not limited to this. For example, the oxide film Ox formed on the surface of the exposed surface of the SiGe layer may be removed by wet etching or by performing the aforementioned COR treatment or PHT treatment.

[0089] Here, in Figure 7 An example of the processing result when the selective etching of the SiGe layer involved in this embodiment is performed is shown in FIG. In this example, first, as described above, the processing gas that has been radicalized by remote plasma is used to selectively form an oxide film Ox on the surface of the exposed surface of the SiGe layer. Figure 7(a) shows the processing result when the oxide film Ox is removed by gas etching using fluorine-containing gas (HF gas) and ammonia (NH 3 ) gas as shown in the above embodiment. Figure 7 (b) shows the processing result when the oxide film Ox is removed by wet etching.

[0090] like Figure 7 (a) and Figure 7 As shown in (b), by forming the oxide film Ox using a process gas that has been radicalized by remote plasma as shown in this embodiment, the etching amount (EA: Etching Amount) from the exposed surface of the SiGe layer can be uniformly controlled. Specifically, Figure 7 The variation in etching amount of each stacked SiGe layer as shown is about 2.2%. As described above, according to the selective etching method of the SiGe layer according to this embodiment, the variation in the total etching amount of each stacked SiGe layer can be appropriately reduced.

[0091] Furthermore, in the above embodiment, the plasma oxidation process in step T1 and the etching removal process of the oxide film Ox in step T2 are performed separately in the plasma processing apparatus 1 and the etching processing apparatus 101. However, these plasma oxidation processes and etching removal processes may also be performed in the same processing vessel. In other words, for example, as long as the plasma processing apparatus 1 is configured to supply HF gas and NH3 gas as etching gases to the processing space S, the oxide film Ox can be etched and removed in the plasma processing apparatus 1.

[0092] Furthermore, as described above, the etching removal process in step T2, the COR process in step T3, and the PHT process in step T4 can be performed in the same processing container (etching processing apparatus 101). In other words, if the plasma processing apparatus 1 is configured to be able to perform etching removal of the oxide film Ox as described above, then the etching removal process in step T2, the COR process in step T3, and the PHT process in step T4 can be performed in the same processing container. Figure 2 A series of wafer processing involving steps T1 to T4.

[0093] Furthermore, in the above embodiment, the selective etching of the SiGe layer is performed. Figure 3 The case where the surface layer of the SiGe layer is removed to a desired depth as shown in the example is described, but it can also be Figure 8The SiGe layer is completely removed as shown. Even in this case, the selective etching of the SiGe layer can be appropriately performed by applying the method of this embodiment. In addition, in this case, the supply of the processing gas to the processing container is stopped before the oxidation amount of the SiGe layer reaches the saturation oxidation amount as described above, and the time of the plasma oxidation processing is controlled so that the oxidation amount of the SiGe layer reaches the saturation oxidation amount by the processing gas remaining in the processing container. This can appropriately shorten the time required for the repeated wafer processing cycle.

[0094] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive, and the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope of the appended claims and the spirit thereof.

[0095] In addition, the following structures also belong to the technical scope of the present disclosure.

[0096] (1) A substrate processing method is a method for processing a substrate having alternately stacked silicon layers and silicon germanium layers, the substrate processing method comprising the following steps: using a gas containing fluorine and oxygen that has been radicalized by remote plasma to selectively oxidize the surface of the exposed surface of the silicon germanium layer to form an oxide film; and removing the formed oxide film.

[0097] According to (1) above, by using a gas radicalized by remote plasma, an oxide film can be uniformly formed on each stacked silicon germanium layer. Furthermore, by removing the oxide film thus formed, the silicon germanium layer is removed, thereby reducing the variation in the etching amount in each stacked silicon germanium layer.

[0098] (2) The substrate processing method according to (1), wherein the gas used to form the oxide film includes O2 gas and fluorine-containing gas, and the volume ratio of the fluorine-containing gas to the O2 gas is greater than or equal to 0.1 vol% and less than or equal to 1.0 vol%.

[0099] (3) The substrate processing method according to (1) or (2), wherein the thickness of the formed oxide film is controlled by the internal pressure of a plasma oxidation processing unit that forms the oxide film.

[0100] (4) A substrate processing method according to any one of (1) to (3), wherein the saturation of the thickness of the formed oxide film does not depend on the processing time of the process of forming the oxide film, and in the process of forming the oxide film, the supply of gas to the plasma oxidation processing part that forms the oxide film is stopped before the formation thickness of the oxide film is saturated.

[0101] (5) The substrate processing method according to any one of (1) to (4), wherein a cycle including a step of forming the oxide film and a step of removing the oxide film is repeated.

[0102] According to (5) above, by repeating the formation and removal of the oxide film, the total amount of etching on the silicon germanium layer can be appropriately controlled.

[0103] (6) A substrate processing method according to any one of (1) to (5), wherein the step of removing the oxide film includes the steps of: transforming the oxide film into a reaction product; and heating the substrate to sublime the reaction product generated by the transformation of the oxide film.

[0104] (7) The substrate processing method according to any one of (1) to (6), wherein the step of removing the oxide film is performed using a gas containing at least HF gas and NH 3 gas.

[0105] (8) A substrate processing device for processing a substrate having alternately stacked silicon layers and silicon germanium layers, the substrate processing device comprising: a plasma processing unit that uses a gas containing fluorine and oxygen that has been radicalized by remote plasma to selectively oxidize the surface of the exposed surface of the silicon germanium layer to form an oxide film; a removal unit that removes the formed oxide film; and a control unit that controls the operations of the plasma processing unit and the removal unit.

[0106] (9) A substrate processing device according to (8), wherein the gas used to form the oxide film includes O2 gas and fluorine-containing gas, and the control unit controls the operation of the plasma processing unit so that the volume ratio of the fluorine-containing gas to the O2 gas is greater than 0.1 vol% and less than 1.0 vol%.

[0107] (10) The substrate processing apparatus according to (8) or (9), wherein the control unit controls the thickness of the formed oxide film by the internal pressure of the plasma processing unit.

[0108] (11) A substrate processing device according to any one of (8) to (10), wherein the saturation of the thickness of the formed oxide film does not depend on the processing time of the plasma processing unit, and before the formation thickness of the oxide film is saturated, the control unit controls the operation of the plasma processing unit to stop supplying gas to the plasma processing unit.

[0109] (12) A substrate processing device according to any one of (8) to (11), wherein the control unit controls the actions of the plasma processing unit and the removal unit to repeat a cycle including the formation of the oxide film in the plasma processing unit and the removal of the oxide film in the removal unit.

[0110] (13) A substrate processing device according to any one of (8) to (12), wherein the control unit controls the action of the removal unit so as to heat the substrate after the oxide film is transformed into a reaction product to sublime the reaction product generated by the transformation of the oxide film.

[0111] (14) The substrate processing apparatus according to any one of (8) to (13), wherein the control unit controls the operation of the removal unit so as to remove the oxide film using a gas containing at least HF gas and NH 3 gas.

[0112] Description of Reference Numerals

[0113] Ox: oxide film; Si: silicon; SiGe: silicon germanium; W: wafer.

Claims

1. A substrate processing method, comprising the following steps: supplying a gas containing fluorine and oxygen radicalized by remote plasma to the substrate, and selectively oxidizing the surface layer of the exposed surface of the silicon germanium layer by utilizing the difference in oxidation rate between the silicon layer and the silicon germanium layer to form an oxide film; and removing the formed oxide film, The gas used to form the oxide film includes O 2 gas and fluorine-containing gas, and the volume ratio of the fluorine-containing gas to the O 2 gas is greater than or equal to 0.1 vol % and less than or equal to 1.0 vol %.

2. The substrate processing method according to claim 1, wherein: The thickness of the oxide film to be formed is controlled by the internal pressure of the plasma oxidation processing unit in which the oxide film is formed.

3. The substrate processing method according to claim 1 or 2, wherein: The saturation of the thickness of the formed oxide film does not depend on the processing time of the step of forming the oxide film. In the step of forming the oxide film, supply of gas to the plasma oxidation processing unit performing the oxide film formation is stopped before the oxide film reaches a saturated thickness.

4. The substrate processing method according to claim 1 or 2, wherein: A cycle including the step of forming the oxide film and the step of removing the oxide film is repeated.

5. The substrate processing method according to claim 1 or 2, wherein: The process of removing the oxide film includes the following steps: transforming the oxide film into a reaction product; and The substrate is heated to sublime a reaction product generated by the degradation of the oxide film.

6. The substrate processing method according to claim 1 or 2, wherein: The step of removing the oxide film is performed using a gas containing at least HF gas and NH 3 gas.

7. A substrate processing apparatus for processing a substrate having silicon layers and silicon germanium layers alternately stacked, the substrate processing apparatus comprising: a plasma processing unit that supplies a gas containing fluorine and oxygen, which has been radicalized by remote plasma, to the substrate, and selectively oxidizes the surface layer of the exposed surface of the silicon germanium layer by utilizing the difference in oxidation rate between the silicon layer and the silicon germanium layer to form an oxide film; a removing portion for removing the formed oxide film; as well as a control unit that controls the operations of the plasma processing unit and the removal unit, The gas used to form the oxide film includes O2 gas and fluorine-containing gas, The control unit controls the operation of the plasma processing unit so that the volume ratio of the fluorine-containing gas to the O 2 gas is greater than or equal to 0.1 vol % and less than or equal to 1.0 vol %.

8. The substrate processing apparatus according to claim 7, wherein: The control unit controls the thickness of the formed oxide film by adjusting the internal pressure of the plasma processing unit.

9. The substrate processing apparatus according to claim 7 or 8, wherein: The saturation of the thickness of the formed oxide film does not depend on the processing time of the plasma processing part. The control unit controls the operation of the plasma processing unit to stop supplying gas to the plasma processing unit before the oxide film reaches a saturated thickness.

10. The substrate processing apparatus according to claim 7 or 8, wherein: The control unit controls the operations of the plasma processing unit and the removal unit to repeat a cycle including forming the oxide film in the plasma processing unit and removing the oxide film in the removal unit.

11. The substrate processing apparatus according to claim 7 or 8, wherein: The control unit controls the operation of the removal unit so that, after transforming the oxide film into a reaction product, the substrate is heated to sublime the reaction product generated by the transformation of the oxide film.

12. The substrate processing apparatus according to claim 7 or 8, wherein: The control unit controls the operation of the removal unit so as to remove the oxide film using a gas containing at least HF gas and NH 3 gas.

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