Etching method

Abstract

An etching technique is provided that can improve the uniformity of the etching amount and increase the yield of the etching process. An etching method for etching a film layer containing titanium carbide disposed on a wafer surface includes: a process of supplying reactive particles containing fluorine and oxygen but not hydrogen to the surface of the film layer to form a reactive layer on the surface of the film layer; and a process of heating the film layer to remove the reactive layer.

Description

Technical Field

[0001] This disclosure relates to a method for etching a film layer, such as a titanium carbide film, containing metal carbides into a processed object using plasma. Prior Technology

[0002] Driven by the widespread adoption of mobile devices, exemplified by smartphones, the high integration of semiconductor components is progressing. In the field of recording semiconductor components, 3D NAND flash memory, which stacks memory cells in multiple layers in three-dimensional space, is in mass production. Furthermore, in the field of logic semiconductor components, the mainstream transistor structure is the fin field-effect transistor (FET), which has a fine three-dimensional structure. Currently, to further improve integration, stacked nano-linear FETs are entering the practical application stage.

[0003] As mentioned above, with the advancement of three-dimensional device structures and miniaturization of processing dimensions, the demand for etching techniques that combine isotropy and high dimensional control at the atomic level is constantly increasing in component manufacturing processes (methods for manufacturing semiconductor devices). Such isotropic etching techniques are widely employed in the prior art through silicon dioxide etching using a mixed aqueous solution of hydrofluoric acid and ammonium fluoride, silicon nitride etching using hot phosphoric acid, and wet etching techniques. However, a problem with these existing wet etching techniques using such solutions is that, with the miniaturization of patterns, pattern collapse due to the surface tension of the rinsing solution becomes significant.

[0004] For example, when using silicon patterns with high aspect ratios, it has been reported that as the pattern spacing narrows, the limit of the pattern spacing that begins to collapse due to surface tension during the drying of the rinsing solution increases proportionally to the square of the aspect ratio. Therefore, there is a strong desire to develop a process method for isotropic etching of various films without the use of chemical solutions.

[0005] On the other hand, in the aforementioned semiconductor components, titanium carbide and titanium aluminum carbide films are widely used as work function metals. Therefore, as a manufacturing process for next-generation semiconductor components, a titanium carbide etching technology that combines isotropic and atomic-level high dimensional control with high selectivity is required.

[0006] As a prior art technique for etching titanium carbide films using plasma without the use of chemical solutions, for example, Japanese Patent Application Publication No. 01-223733 (Patent Document 1) has been proposed.

[0007] As a method for etching to remove titanium carbide films, Patent Document 1 discloses a technique for etching using CF4 / O2 plasma. [Previous Technical Documents] [Patent Literature]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 01-223733 Summary of the Invention

[0009] [The problem the invention aims to solve] In the prior art disclosed in Patent Document 1, problems arise because the following points are not adequately considered.

[0010] In other words, although the technology for etching titanium carbide is disclosed in Patent Document 1, it does not consider the processing conditions for isotropic etching of a work function metal film that has already been patterned in the manufacturing process. Specifically, it does not consider the following problem: in the manufacturing process of work function metals such as finned FETs or stacked nanowire FETs, when conformal etching is required at the atomic level in the fine three-dimensional structure, the different etching rates at the top and bottom of the pattern cause vertical variations in the thickness of the processed film. Therefore, in the technology of Patent Document 1, the amount of etching in the processed film layer has a large distribution in the vertical (depth) direction of the pattern formed in the film structure, leading to a decrease in yield in the etching process (etching engineering) of semiconductor components.

[0011] Furthermore, in the technology of Patent Document 1, the etching of the titanium carbide film is performed continuously in accordance with the increase of etching time. In such a continuous etching process, the amount of etching can be adjusted by detecting and adjusting the time after the start of the etching process. In adjusting the amount of etching through such etching process time, it is difficult to adjust with high precision for the extremely fine amount of etching required for the manufacturing processes of next-generation semiconductor devices, such as when the etching depth (width) is at the atomic layer level. Therefore, there is a risk that the accuracy and yield of the etching process may be compromised.

[0012] As described above, in the continuous plasma etching technology of Patent Document 1, the etching amount becomes non-uniform due to its reflection of free radical distribution, resulting in reduced uniformity of the etching amount in the wafer plane or pattern depth direction. Furthermore, the etching amount must be controlled by the plasma processing time. Therefore, the application of the continuous plasma etching technology of Patent Document 1 is considered to be limited in the manufacturing processes of next-generation and beyond components that require high dimensional control at the atomic level.

[0013] The purpose of this disclosure is to provide an etching technique with high uniformity of etching amount and improved yield of etching process.

[0014] Other objects and novel features of this disclosure will become apparent from the description and drawings herein. [Problem-solving methods]

[0015] A brief summary of the representative features of this disclosure is given below.

[0016] The etching technique disclosed herein is an etching method for etching a film layer containing a metal carbide disposed on the surface of a wafer, comprising: supplying reactive particles containing fluorine and oxygen but not hydrogen to the surface of the film layer to form a reactive layer containing bonds between metal and fluorine on the surface of the film layer; and heating the film layer to detach the reactive layer. [Invention Effects]

[0017] The effects that can be obtained by the representative parties in this disclosure are briefly explained below.

[0018] According to the etching technology disclosed herein, the uniformity of the etching amount can be improved, and the yield of the etching process can be increased. For example, an isotropic atomic layer etching technology can be provided, which, when etching a film containing metal carbides, i.e., a titanium carbide film, can achieve a high uniformity of etching amount in both the in-plane direction and the pattern depth direction, and can perform the etching process with high dimensional control at the atomic layer level. Simple Explanation of the Diagram

[0019] [Figure 1] is a schematic longitudinal sectional view illustrating the configuration of a plasma processing apparatus according to an embodiment of the present disclosure. [Figure 2] is a schematic flowchart illustrating the process of etching a titanium carbide-containing film pre-formed on a wafer using a plasma processing apparatus according to an embodiment of the present disclosure. [Figure 3] is a timing diagram showing the changes of multiple parameters included in the processing conditions in the wafer processing of the embodiment shown in Figure 1 over time. [Figure 4] is a schematic cross-sectional view illustrating the variation of the film structure, including a film containing titanium carbide, in the wafer processing of the embodiment shown in Figure 3. [Figure 5] is a graph showing the analysis results of the wafer surface of the embodiment shown in Figure 1. [Figure 6] is a graph showing the reaction time dependence of the amount of surface reaction layer generated in the embodiment shown in Figure 1. [Figure 7] is a graph showing the heating temperature dependence of the amount of surface reaction layer residue in the embodiment shown in Figure 1. [Figure 8] is a graph showing the relationship between the number of cycles and the amount of etching during the etching process performed by the plasma processing apparatus of the embodiment shown in Figure 1. [Figure 9] is a graph showing the relationship between the number of cycles and the amount of etching in the etching process performed by the plasma processing apparatus of the embodiment shown in Figure 1, and it is a graph showing the results when the wafer temperature is changed. [Figure 10] is a longitudinal cross-sectional view schematically showing the changes in the film structure when plasma etching is performed on a fine film structure with a high aspect ratio formed on a substrate such as a semiconductor wafer, using the technique of this disclosure. [Figure 11] is a longitudinal cross-sectional view schematically showing the changes in a film structure formed on a sample on a substrate such as a semiconductor wafer, when plasma etching is performed using existing technology. Implementation

[0020] Embodiments of the present disclosure are described below with reference to the accompanying drawings. In the following description, the same constituent elements may be represented by the same symbols, and repeated descriptions are omitted. Furthermore, to make the description clearer, the drawings may be shown more schematically than the actual aspects, but this is merely illustrative and does not limit the interpretation of the present disclosure.

[0021] In the process of forming functional metals in the manufacturing of semiconductor components such as finned FETs, a technique for isotropic and high-precision etching at the atomic level is considered necessary for titanium carbide films formed in fine fin structures with high aspect ratios. Therefore, as an example, the inventors reviewed the case of plasma etching of the structure shown in FIG11 using existing technology.

[0022] Figure 11 is a schematic longitudinal cross-sectional view showing the change of the film structure when a predetermined structure with multiple fin structures formed on adjacent sides is plasma etched using existing technology. The predetermined structure is formed on a sample such as a semiconductor wafer to be processed. Figures 11(a) to 11(c) show three stages of the shape of the film structure changing due to the etching process.

[0023] Figure 11(a) shows the film structure in the state before the etching process using plasma begins. This film structure is as follows: a titanium carbide film 903 to be processed and a mask 904 are formed on the surface of the fin structure 902 formed on the substrate structure 901. The mask 904 is used to protect the portion of the titanium carbide film 903 that is not to be processed. Figure 11(b) shows the state during the etching of the titanium carbide film 903. In Figure 11(b), a plasma is formed using tetrafluoromethane (CF4) and oxygen gas (O2) (hereinafter referred to as CF4 / O2 gas) to etch the titanium carbide film 903 having the film structure shown in Figure 11(a). Then, a fluorine-containing reactive species 905 in the plasma is supplied into the trench 911 of the film structure, reacting with the surface of the titanium carbide film 903 while maintaining the wafer temperature at room temperature. As a result, the reaction product 906 containing titanium fluoride is removed from above, and the etching of the titanium carbide film 903 is carried out. Figure 11(c) shows the state in which the etching of the titanium carbide film 903 is stopped using the above-mentioned plasma. In this example, the fin structure 902 is made of silicon and is pre-formed on the substrate structure 901, and its surface is coated with hafnium oxide or titanium nitride (not shown).

[0024] Based on the review by the present disclosers, the following was confirmed. Specifically, as shown in FIG11(b), in a structure where the surface of the fin structure 902 is covered by a titanium carbide film 903, an attempt was made to uniformly etch the titanium carbide film 903 only inside the high aspect ratio trench 911 constituting the sidewalls on both sides. However, since a low wafer temperature was not used to suppress the volatilization of the reaction product 906, the surface reaction layer did not remain on the surface of the titanium carbide film 903, and it was confirmed that continuous detachment due to the volatilization of the reaction product 906 resulted in continuous etching. On the other hand, the reaction seed 905 supplied from the plasma formed above the sample enters the inside of the trench 911 from above and is consumed by the titanium carbide film 903 formed near the opening at the upper end of the trench 911. Therefore, the amount of reaction seed 905 in the region reaching the lower part 9111 of the trench 911 (the bottom of the trench 911) is reduced. Therefore, as shown in Figure 11(c), the etching amount of the titanium carbide film 903 becomes uneven in the vertical direction of the trench 911. As a result, the etching amount of the titanium carbide film 903 is larger near the opening of the upper part 9112 of the trench 911, and smaller at the lower part 9111 of the trench 911. Consequently, when etching the titanium carbide film 903 using existing technology, the uneven distribution of the etching amount of the titanium carbide film 903 occurs, leading to a reduction in the yield of sample processing or semiconductor component manufacturing.

[0025] As described above, in existing plasma etching techniques, the etching amount of the titanium carbide film 903, which reflects the distribution of free radicals, becomes uneven, and the uniformity of the etching amount of the titanium carbide film 903 in the in-wafer plane direction and the pattern depth direction is reduced. Furthermore, the etching amount of the titanium carbide film 903 must be controlled by the plasma processing time. Therefore, the application of existing continuous plasma etching techniques is considered to be limited in the manufacturing processes of next-generation and beyond components that require high dimensional control at the atomic level.

[0026] The authors attempted to etch titanium carbide films using plasmas of various gases. As a result, they discovered the following (1) to (3). (1) By supplying plasma containing fluorine and oxygen but no hydrogen to the titanium carbide film, a surface reaction layer with titanium-fluorine (Ti-F) bonding as the main component is formed on its surface. (2) The amount of surface reaction layer generated has a self-saturating characteristic (self-limiting characteristic). (3) Remove the surface reaction layer by heating.

[0027] This disclosure is made based on the new findings ((1)-(3)). A method for etching titanium carbide films (film layers of the object being treated), specifically, the etching method involves the following process: The first process involves forming a plasma containing tetrafluoromethane (CF4) and oxygen (O2), supplying reactive particles containing fluorine and oxygen but no hydrogen from this plasma to the surface of a titanium carbide film to be etched, and forming a surface reaction layer on the surface of the titanium carbide film (also known as the surface reaction layer formation process). The second process involves removing the surface reaction layer by heating (or removing the surface reaction layer by heating) (also known as the surface reaction layer removal process).

[0028] Then, the two processes (the first process and the second process) are treated as a cycle, and the required amount of titanium carbide film is etched by repeating the cycle multiple times.

[0029] Based on the above configuration, since the formation and removal processes of the surface reactive layer have self-saturation characteristics, the non-uniformity of etching amount in the in-plane direction and the depth direction of the film structure pattern such as trenches or holes on the wafer can be suppressed. Furthermore, the thickness of the titanium carbide film removed in a single cycle can be adjusted with high precision at the atomic layer level, and the etching amount obtained by repeated cycles can be adjusted by the number of repeated cycles. Therefore, the dimensional accuracy of semiconductor devices formed by etching stacked titanium carbide films can be improved.

[0030] Figure 10 schematically shows a longitudinal cross-sectional view of the change in a fine film structure with a high aspect ratio formed on a sample on a substrate such as a semiconductor wafer, using the techniques of this disclosure for plasma etching. Figures 10(a) to 10(c) show three stages of the shape of the film structure changing due to the etching process.

[0031] Figure 10(a) shows the film structure in the state before the plasma etching process begins, and shows that a titanium carbide film 903 to be processed and a mask 904 are formed on the surface of the fin structure 902 formed on the substrate structure 901. The mask 904 is used to protect the portion of the titanium carbide film 903 that is not to be processed. In Figure 10(b), in order to etch the titanium carbide film 903 of the film structure of Figure 10(a), reactive particles containing fluorine and oxygen but no hydrogen are supplied from the plasma to the surface of the titanium carbide film 903 not covered by the mask 904 by forming a plasma containing a mixed gas of tetrafluoromethane (CF4) and oxygen (O2), thereby forming a surface reaction layer on the surface of the titanium carbide film 903 to be etched. Then, the surface reaction layer is removed by heating (removal). That is, the following processes are performed: the process of forming the surface reaction layer (first process); and the process of removing the surface reaction layer by heating (second process). Then, the two processes (the first process and the second process) are treated as a cycle, and the required amount of titanium carbide film is etched by repeating the cycle multiple times.

[0032] Therefore, as shown in FIG10(c), the titanium carbide film 903 of the etched object not covered by the mask 904 can be selectively removed by etching. Furthermore, since the gas of this disclosure does not contain hydrogen, it has the characteristic of not etching films of nitrides such as titanium nitride. In the gas of this disclosure, titanium oxynitride is generated on the surface of titanium nitride, thus stopping the etching process.

[0033] On the other hand, for example, when a mixed gas containing hydrogen trifluoromethane (CHF3) and oxygen (O2) is used, a surface reaction layer such as titanium ammonium fluoride is formed on the surface of titanium nitride, and during the heating step, the surface reaction layer such as titanium ammonium fluoride volatilizes, causing the titanium nitride to be etched. However, in this case, there is a problem: it cannot be applied to processes that selectively etch titanium carbide relative to titanium nitride, such as in the manufacturing process of work function metals. For a more detailed explanation of Figures 10(a) to 10(c), please refer to the description of Figures 4(a) to 4(c) below.

[0034] Furthermore, in the following embodiments, the etching process of repeatedly performing a set of processes (first process and second process) is referred to as atomic layer etching. This set of processes includes a process for forming a surface reaction layer (first process) with self-saturating characteristics in each process and a process for removing the surface reaction layer (second process). In this embodiment, "atomic layer" etching is not limited to atomic layer etching in the narrow sense, where the etching amount in one cycle is equal to the thickness of the layer composed of a single atom of the material constituting the film. For example, even if the etching amount in one cycle is at the nanometer or larger level, when each process has a tendency to self-saturate with respect to processing time, that is, to have a self-limiting characteristic, this process is also referred to as atomic layer etching. In addition, terms such as "digital etching," "self-limiting cycle etching," "atomic level etching," and "layer by layer etching" can also be used for equivalent processes.

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the figures. [Example]

[0036] The embodiments of this disclosure are described below using Figures 1 to 9. In this embodiment, the etching technique is described below. First, a surface reaction layer is formed on the surface of the titanium carbide film to be processed using a plasma formed by a mixed gas of tetrafluoromethane (CF4), oxygen (O2), and argon (Ar) (first process). Then, the surface reaction layer is removed by heating the wafer with an infrared lamp (second process). As a result, the titanium carbide film to be processed, which was previously formed on a semiconductor wafer such as silicon, is subjected to isotropic atomic layer etching.

[0037] Figure 1 is a schematic longitudinal sectional view illustrating the configuration of a plasma processing apparatus according to an embodiment of the present disclosure.

[0038] The processing chamber 1 consists of a substrate chamber 11, in which a wafer stage 4 (hereinafter referred to as stage 4) is provided for mounting a wafer 2 (hereinafter referred to as wafer 2) as the sample to be processed. The plasma source employs an ICP (Inductively Coupled Plasma) discharge method, and the plasma source, comprising a quartz chamber 12, an ICP coil 34, and a high-frequency power supply 20, is positioned above the processing chamber 1. Here, the ICP coil 34 is positioned outside the quartz chamber 12.

[0039] A high-frequency power supply 20 for generating plasma is connected to an ICP coil 34 via a matching adapter 22. Assume the frequency of the high-frequency power is in the tens of MHz band, such as 13.56 MHz. A top plate 6 is provided on the upper part of the quartz chamber 12. A spray plate 5 is provided on the top plate 6, and a gas dispersion plate 17 is provided below it. Processing gas is introduced into the processing chamber 1 from the outer periphery of the gas dispersion plate 17.

[0040] The flow rate of the supplied processing gas is adjusted by a mass flow controller 50, which is disposed within a mass flow controller control unit 51 and is configured for each gas. In Figure 1, at least tetrafluoromethane (CF4), oxygen (O2), and argon (Ar) are supplied as processing gases to the processing chamber 1, and mass flow controllers 50-2, 50-3, 50-4, and 50-6 are configured for each of these gases. However, the supplied gases are not limited to these. The mass flow controller control unit 51 is also equipped with a mass flow controller 50-7, which is used to adjust the flow rate of He gas supplied between the back side of the wafer 2 and the upper surface of the dielectric film on the mounting stage 4 on which it is mounted.

[0041] The lower part of the processing chamber 1 is connected to the exhaust means 15 through a vacuum exhaust pipe 16 to depressurize the interior of the processing chamber 1. The exhaust means 15 is composed of, for example, a turbomolecular pump, a mechanical booster pump, or a dry pump. In addition, a pressure adjustment means 14 is provided upstream of the exhaust means 15. The pressure adjustment means 14 is adjusted by increasing or decreasing the flow rate of internal gas discharged from the processing chamber 1 by the operation of the exhaust means 15, or by increasing or decreasing the flow rate of plasma 10 particles, using the cross-sectional area of ​​the flow path in a plane perpendicular to the axial direction of the vacuum exhaust pipe 16. In order to adjust the pressure of the processing chamber 1 and the discharge region 3, the pressure adjustment means 14 is composed of multiple plate-shaped vanes or plate members. The multiple plate-shaped vanes are arranged in a direction that cuts through the flow path and have an axis and rotate about the axis. The plate members move transversely along their axial direction inside the flow path.

[0042] An infrared lamp unit for heating wafer 2 is disposed between the stage 4 and the quartz chamber 12 constituting the ICP plasma source. The infrared lamp unit mainly comprises an infrared lamp 62, a reflector 63 for reflecting infrared light, and a light-transmitting window 74. The infrared lamp 62 is a circular (ring-shaped) lamp. Furthermore, the light emitted from the infrared lamp 62 is primarily light within the visible light to infrared range. Here, this light is referred to as infrared light. In the configuration shown in Figure 1, three infrared lamps 62-1, 62-2, and 62-3 are provided as infrared lamps 62, but two, four, etc., can also be used. A reflector 63 is disposed above the infrared lamp 62 to reflect the infrared light downwards.

[0043] Infrared lamp power supply 64 is connected to infrared lamp 62, and high-frequency cutoff filter 25 is disposed between them to prevent noise from the high-frequency power generated by high-frequency power supply 20 for plasma generation from flowing into infrared lamp power supply 64. In addition, infrared lamp power supply 64 has the function of independently controlling the power supplied to infrared lamps 62-1, 62-2, and 62-3, and can adjust the radial distribution of heating amount on wafer 2.

[0044] A gas flow path 75 is formed in the center of the infrared lamp unit to direct the gas supplied from the mass flow controller 50 to the inside of the quartz chamber 12 toward the processing chamber 1. A slit plate (ion shielding plate) 78 with multiple holes is provided in the gas flow path 75 to shield ions and electrons generated in the plasma generated inside the quartz chamber 12, allowing only neutral gases and neutral free radicals to pass through and irradiate the wafer 2.

[0045] A coolant flow path 39 for cooling the stage 4 is formed inside the stage 4, and the coolant is circulated and supplied by the cooler 38. In addition, in order to fix the wafer 2 on the stage 4 by electrostatic adsorption, a plate-shaped electrode plate, namely an electrostatic adsorption electrode 30, is embedded in the stage 4. The electrostatic adsorption electrode 30 is connected to a DC (Direct Current) power supply 31 for electrostatic adsorption.

[0046] Furthermore, to effectively cool the wafer 2, He gas can be supplied between the back side of the wafer 2 and the mounting stage 4. Additionally, to prevent scratches on the back side of the wafer 2 even when the electrostatic adsorption electrode 30 is activated and the wafer 2 is heated or cooled in an electrostatic adsorption state, the wafer mounting surface of the mounting stage 4 is coated with a resin such as polyimide. Furthermore, a thermocouple 70 for measuring the temperature of the mounting stage 4 is installed inside the mounting stage 4, and this thermocouple 70 is connected to a thermocouple thermometer 71.

[0047] In addition, optical fibers 92-1 and 92-2, used for measuring the temperature of wafer 2, are positioned at three locations: near the center of wafer 2 (also known as the wafer center), near the radial center of wafer 2 (also known as the wafer center), and near the outer periphery of wafer 2 (also known as the wafer outer periphery). Optical fiber 92-1 guides infrared light from an external infrared light source 93 to the back side of wafer 2 and illuminates it. On the other hand, optical fiber 92-2 collects IR light transmitted through or reflected from the wafer 2 from the infrared light irradiated by optical fiber 92-1 and transmits it to beam splitter 96.

[0048] The external infrared light generated in the external infrared light source 93 is transmitted to the optical path switch 94 for turning the optical path on / off. Then, it is branched into multiple (three in the case of FIG1) by the light distributor 95 and illuminated to individual positions on the back side of the wafer 2 via the optical fibers 92-1 of the three systems.

[0049] Infrared light absorbed / reflected by wafer 2 is transmitted to spectrometer 96 via optical fiber 92-2, and wavelength dependence data on spectral intensity is obtained in detector 97. This wavelength dependence data is then transmitted to calculation unit 41 of control unit 40 to calculate the absorption wavelength, and the temperature of wafer 2 is determined based on this absorption wavelength. Furthermore, an optical multiplexer 98 is provided in the middle of optical fiber 92-2, allowing switching between measurement points at the wafer center, wafer center, and wafer periphery for the light to be spectrometered. As a result, calculation unit 41 can determine the temperatures at the wafer center, wafer center, and the periphery of each wafer.

[0050] In Figure 1, 60 is a container covering the quartz chamber 12, and 81 is an O-ring for vacuum sealing between the stage 4 and the bottom surface of the base chamber 11.

[0051] The control unit 40 controls the switching on / off of the high-frequency power supplied from the high-frequency power supply 20 to the ICP coil 34. Additionally, it controls the mass flow controller control unit 51 to adjust the type and flow rate of the gas supplied from each mass flow controller 50 to the interior of the quartz chamber 12. In this state, the control unit 40 further activates the exhaust means 15 and controls the pressure adjustment means 14 to adjust the pressure inside the processing chamber 1 to the desired pressure.

[0052] Furthermore, the control unit 40 activates the DC power supply 31 for electrostatic adsorption to electrostatically adsorb the wafer 2 onto the stage 4. While the mass flow controller 50-7 supplying He gas between the wafer 2 and the stage 4 is activated, the control unit 40 controls the infrared lamp power supply 64 and the cooler 38 to ensure that the temperature of the wafer 2 falls within a predetermined temperature range. At this time, the calculation unit 41 calculates the temperature distribution information of the wafer 2 based on the internal temperature of the stage 4 measured by the thermocouple thermometer 71 and the spectral intensity information near the center, the radial middle, and the outer periphery of the wafer 2 measured by the detector 97. The control unit 40 controls the infrared lamp power supply 64 and the cooler 38 based on this temperature distribution information to ensure that the temperature of the wafer 2 falls within the predetermined temperature range. The preferred temperature range is -40°C to 0°C. A representative temperature is -20°C. Here, if the wafer temperature is below -40°C, the time required to lower the wafer temperature to that temperature and the etching process itself become longer during the temperature cycling process, resulting in a decrease in the number of wafers processed per unit time, i.e., throughput, which is undesirable. On the other hand, when the wafer temperature reaches above 0°C, the titanium fluoride contained in the surface reaction layer generated during plasma processing continues to volatilize, thus preventing the self-saturation characteristic of the reaction from being achieved.

[0053] Referring to FIG2, the processing flow of wafer 2 performed in the plasma processing apparatus 100 of this embodiment will be described. FIG2 is a schematic flowchart showing the process of etching a titanium carbide-containing film pre-formed on a wafer through the plasma processing apparatus of this embodiment.

[0054] In Figure 2, before the wafer 2 is processed, the wafer 2 with a pre-configured film structure is placed on the stage 4 in the processing chamber 1. The film structure includes: a film layer containing a titanium carbide film disposed on the surface of the object to be processed. DC power from DC power supply 31 is supplied to the electrostatic adsorption electrode 30, and the wafer is held on the stage 4 by the generated electrostatic force.

[0055] After the processing begins, in step S201, a gas containing fluorine and oxygen but no hydrogen is introduced into the processing chamber 1. Here, the gas containing fluorine and oxygen but no hydrogen can be tetrafluoromethane (CF4) / oxygen (O2), nitrogen trifluoride (NF3) / oxygen (O2), etc. Alternatively, a mixed gas obtained by diluting these gases with argon (Ar), nitrogen (N2), etc., can be used. Furthermore, the wafer temperature in step S201 is kept constant by the temperature adjustment function of the mounting stage 4 on which the wafer 2 is placed. Additionally, when using nitrogen trifluoride (NF3) or nitrogen (N2), mass flow controllers 50-1 and 50-8 for nitrogen (N2) and mass flow controller 50-5 for nitrogen trifluoride (NF3) can be used.

[0056] Next, in step S202, the above-mentioned gas is used to generate plasma 10 inside the discharge region 3, and the atoms or molecules of the gas containing fluorine and oxygen but not hydrogen in plasma 10 are activated to generate reactive particles (also called reactive particles) with free radicals (active species) such as fluorine (F).

[0057] Furthermore, in step S203, reactive particles are supplied to the surface of wafer 2 through the gas flow path 75 and the through-hole of the slit plate 78, causing the reactive particles to adhere to the surface of the film layer containing the titanium carbide film. The reactive particles react with the material on the surface of the film layer to form a surface reaction layer, the thickness of which is determined by processing conditions such as the conditions for generating plasma 10 and the temperature of the mounting stage 4. At this time, the surface reaction layer formed on the surface of the film layer containing the titanium carbide film contains at least titanium-fluorine (Ti-F) bonds.

[0058] Subsequently, in step S204, in the control unit 40, after confirming that a surface reaction layer with a predetermined thickness has been formed using a film thickness detector (not shown), or by detecting whether a predetermined time has elapsed, the pressure adjustment means 14 increases the flow path cross-sectional area of ​​the vacuum exhaust pipe 16 to increase the exhaust volume, thereby significantly reducing the pressure inside the processing chamber 1. Then, the gas containing fluorine and oxygen but not hydrogen supplied to the processing chamber 1 is rapidly discharged. This completes the surface reaction layer formation process. At this time, supplying an inert gas such as Ar into the processing chamber 1 to replace the gas containing fluorine and oxygen but not hydrogen in the processing chamber 1 can promote the discharge of the gas containing fluorine and oxygen but not hydrogen.

[0059] Next, in step S205, infrared lamp 62 is turned on, and the surface of wafer 2 is heated in a vacuum state by the light emitted from infrared lamp 62 (infrared light). The irradiation time of infrared light at this time is, for example, 20 seconds, and the maximum temperature reached on the surface of wafer 2 at this time is, for example, 120°C. The pressure of the processing chamber 1 during heating is, for example, set to 1×10⁻³ Pa. At this time, as the irradiation time of infrared lamp increases, the temperature of wafer 2 rises at a rate of, for example, about 7°C / second, and the surface reaction layer evaporates from the surface through this temperature rise. After the temperature of wafer 2 has been confirmed to have risen to the predetermined temperature by temperature detection mechanisms (92-97, 41), or after the predetermined time has been confirmed by controller 40, infrared lamp 62 is turned off.

[0060] Examples of volatile reaction products include titanium fluoride (TiF4) and carbon dioxide (CO2). These reaction product particles detaching from wafer 2 are discharged from the interior of processing chamber 1 to the exterior through the action of pressure adjustment means 14 or exhaust means 15 to ventilate the interior of processing chamber 1, or through the resulting airflow of particles moving within processing chamber 1. Next, in step S206, the gas containing the reaction products is discharged from the interior of processing chamber 1 to the exterior of processing chamber 1.

[0061] This completes one cycle, treating steps S201-S206 as a group. Through this cycle, the surface reaction layer formed on the titanium carbide film surface due to the reaction with the plasma is removed (removed). Therefore, the thickness of the titanium carbide film is reduced only by removing the surface reaction layer. The amount of this change in film thickness is the etching amount for each cycle described above.

[0062] Subsequently, the control unit 40 receives the output from the film thickness detector (not shown) and determines, based on the obtained result, whether the desired etching amount has been reached, or whether the termination condition, including the number of times the above-mentioned cycle has been executed, is met. This termination condition is derived from pre-set tests, etc., to obtain the desired etching amount (step S207). If the condition is met (S207: Yes), the etching process of the film layer including the titanium carbide film ends; if the condition is not met (S207: No), the process returns to step 201 and executes the cycle again (S201-S206). As described above, in this embodiment, the above-mentioned cycle (S201-S206) is repeated until the desired etching amount is obtained.

[0063] Hereinafter, Figures 3 and 4 will be used to describe the sequence of operations when etching a titanium carbide film layer on wafer 2 using the plasma processing apparatus 100 of this embodiment with CF4 / O2 / Ar as the gas for forming the reaction layer. Figure 3 is a timing diagram showing the changes over time of multiple parameters included in the processing conditions of the wafer processing in the embodiment shown in Figure 1. In Figure 3, the parameters shown in sequence from top to bottom are gas supply flow rate, high-frequency power supply power, infrared lamp power, electrostatic adsorption, and wafer surface temperature.

[0064] Figure 4 is a cross-sectional view schematically illustrating the changes in the film structure during wafer processing in the embodiment shown in Figure 3. The film structure is a film structure comprising layers of titanium carbide films. In particular, Figure 4 schematically shows the structure near the surface of the titanium carbide film 402 and its changes, which is a film structure in which titanium carbide films 402 are stacked adjacently on the substrate film 401 of wafer 2.

[0065] First, at time t0 in the process shown in Figure 3, in response to a command signal from the control unit 40, a wafer 2 with a pre-formed film structure is transported into the processing chamber 1 via a transfer port (not shown) and placed on the mounting stage 4. This film structure includes a base film 401 as shown in Figure 4(a) and an etched film layer, namely a titanium carbide film 402. Then, power from the DC power supply 31 is supplied to the electrostatic adsorption electrode 30, and the wafer 2 is electrostatically adsorbed and held on the dielectric film on the mounting stage 4. Furthermore, in response to a command signal from the control unit 40, the flow rate of He gas used for cooling the wafer is adjusted via the mass flow controller 50-7 corresponding to He gas in the mass flow controller control unit 51, and supplied to the gap between the back side of the wafer 2 and the mounting stage 4. The pressure of the He gas in this gap is also adjusted to a value within a predetermined range. As a result, heat transfer between the stage 4 and the wafer 2 is facilitated, and the surface temperature of the wafer 2 is set to a value T1 close to the temperature of the stage 4, which is supplied with refrigerant pre-set to a predetermined temperature by the cooler 38 and circulated in the refrigerant flow path 39. In this embodiment, the surface temperature T1 of the wafer 2 is set, for example, to -20°C.

[0066] Next, at time t1 shown in Figure 3, in response to the command signal from the control unit 40, the supply flow rate is adjusted in each of the mass flow controllers 50-3 or 50-6 for adjusting CF 4, 50-2 for adjusting O 2, and 50-4 for adjusting Ar. Thus, a mixed gas of these various substances is supplied to the processing chamber 1 as the processing gas at a flow rate within a predetermined range. Simultaneously, the opening of the pressure adjustment means 14 is adjusted so that the pressure inside the processing chamber 1 and in the discharge region 3 inside the quartz chamber 12 is set to a value within a desired range.

[0067] In this state, at time t2 shown in Figure 3, in response to the command signal from the control unit 40, a predetermined value W of high-frequency power is supplied from the high-frequency power supply 20 to the ICP coil 34, and plasma discharge begins in the discharge region 3 inside the quartz chamber 12, generating plasma 10 inside the quartz chamber 12. At this time, no power is supplied to the infrared lamp 62 to maintain the temperature of the wafer 2 during plasma 10 generation at the same temperature as before plasma 10 generation.

[0068] In this state, at least a portion of the CF4 / O2 / Ar gas particles are excited, dissociated, or ionized in plasma 10, forming charged particles such as ions or reactive particles such as active species. The reactive particles such as active species and neutral gas formed in discharge region 3 are introduced into processing chamber 1 through slits or through-holes formed in slit plate 78 and supplied to the surface of wafer 2. As shown in FIG4(b), active species 403 containing fluorine radicals (F) are adsorbed onto the surface of titanium carbide film 402 of wafer 2, interacting with the material of titanium carbide film 402 to form a surface reaction layer 404. That is, reactive particles 403 containing fluorine and oxygen but not hydrogen are supplied to the surface of titanium carbide film 402, and a surface reaction layer 404 is formed on the surface of titanium carbide film 402.

[0069] The surface reaction layer 404 is a reaction product containing Ti-F bonds as the main component. When measured using X-ray photoelectron spectroscopy with aluminum Kα rays, its most prominent characteristic is that the binding energy of titanium 2p peaks near 462±2 eV (2p 3 / 2) and near 467±2 eV (2p 1 / 2). Figure 5 shows the photoelectron spectrum of the titanium carbide film 402 with the surface reaction layer 404 formed, analyzed using X-ray photoelectron spectroscopy with aluminum Kα rays. The peaks observed in the binding energy (eV) near 462±2 eV and 467±2 eV due to the surface reaction layer 404 indicate the presence of Ti-F bonds. The composition of the surface reaction layer depends on the composition of the gas used and the reaction time. It can be monomeric fluorine, or a mixture of carbon, fluorine, and titanium in various bond states, such as fluorocarbons and titanium fluoride. In some cases, it may also include oxides of titanium carbide and oxides of carbon. The binding energy value expressed here is a corrected value assuming that the position of the carbon 1s peak due to surface contamination carbon observed on the initial sample surface is 284.5 eV.

[0070] Figure 6 is a graph showing the dependence of the intensity of the titanium 2p peak caused by the surface reaction layer 404 on the plasma treatment time. The plasma treatment time represents the time elapsed since the start of high-frequency power supply. As shown in Figure 6, the intensity of the titanium 2p peak generated by the surface reaction layer 404 increases with the passage of plasma treatment time and shows a saturation trend, becoming almost constant when the plasma treatment time is 60 seconds or more. Thus, the amount of reaction product generated has a self-saturating property, which is very similar to the natural oxidation phenomenon of metal and silicon surfaces. Therefore, since the formation of the surface reaction layer has a self-saturating property, the amount of surface reaction layer 404 generated in each cycle can be kept constant by performing plasma treatment for a time longer than required for saturation. In this embodiment, it takes 60 seconds for the amount of surface reaction layer 404 generated to reach saturation; however, the time required to reach saturation varies depending on device parameters such as the distance between the plasma source (12, 34) and the wafer 2, and the substrate temperature.

[0071] After the plasma treatment time required for the surface reaction layer to reach saturation is completed, at time t3 as shown in Figure 3, in response to the command signal from the control unit 40, the output of high-frequency power from the high-frequency power supply 20 is stopped, and the supply of processing gas to the discharge region 3 is also stopped. As a result, the plasma 10 in the discharge region 3 disappears. In addition, between time t3 and time t4, the processing gas and reactive particles in the processing chamber 1 are discharged to the outside of the processing chamber 1 through the vacuum exhaust pipe 16, whose opening is adjusted by the pressure adjustment means 14, and the exhaust means 15.

[0072] At time t4, the infrared lamp 62 is turned on in response to a command signal from the control unit 40, as shown in FIG4(c), and the surface of the wafer 2 is vacuum heated by the light (infrared light) 405 emitted from the infrared lamp 62. At this time, the pressure of the processing chamber 1 is set to, for example, 1×10⁻³ Pa, and the irradiation time of the infrared lamp 62 is set to, for example, 20 seconds. The maximum temperature reached on the surface of the wafer 2 is, for example, 120°C. This process is a reaction that decomposes the surface reaction layer 404 into reaction products 406 containing titanium fluoride and volatilizes or detaches them. This detachment reaction is more advantageous at higher temperatures and lower pressures. The inventors have found that in order to induce this detachment reaction, the surface temperature of the wafer 2 needs to be 50°C or higher, and the pressure of the processing chamber 1 is preferably 10 Pa or lower.

[0073] In this embodiment, the maximum reachable temperature of wafer 2 is set to 120°C, and the vacuum level of processing chamber 1 is set to 1×10⁻³ Pa. The maximum reachable temperature can be set to an appropriate value within a temperature range above 50°C. A typical temperature range is 50~150°C, and a typical pressure range for processing chamber 1 during heating is 1×10⁻⁵~10 Pa. If the heating temperature is set to 150°C, the heating time becomes longer, resulting in a decrease in the number of wafers that can be processed per unit time, i.e., the production output. Therefore, it is preferable to set the wafer heating temperature below 150°C.

[0074] Figure 7 is a graph showing the change in the titanium 2p peak intensity caused by the surface reaction layer 404 relative to the heating temperature when the surface reaction layer 404 is removed by vacuum heating at a vacuum level of 1×10⁻⁴ Pa. As a result, the intensity of the titanium 2p peak, representing the residual amount of surface reaction layer 404, decreases with increasing heating temperature. At a heating temperature of 50°C, the surface reaction layer 404 is significantly reduced, and it completely disappears at a heating temperature of 100°C. Therefore, the suitable heating temperature range is 50°C to 150°C. That is, the wafer temperature in the process of removing the surface reaction layer 404 (second process) is preferably in the range of 50°C to 150°C. When the heating temperature is below 50°C, there is a problem that the surface reaction layer 404 is not fully volatilized and remains. Furthermore, if the heating temperature is above 150°C, the heating and cooling temperature range becomes larger, and the time required for heating and cooling becomes longer, resulting in a decrease in wafer processing yield, which is therefore not preferred. Furthermore, in this heating process, only the surface reaction layer 404 formed on the surface of wafer 2 is decomposed and volatilized, while the unreacted titanium carbide film 402 existing beneath the surface reaction layer 404 remains completely unchanged. Therefore, only a portion of the surface reaction layer 404 can be removed. Thus, in addition to the process of forming the surface reaction layer 404, the process of removing the surface reaction layer 404 also possesses self-saturating characteristics.

[0075] Additionally, during this heating process, wafer 2 is placed on wafer stage 4, but the supply of helium gas to improve thermal conductivity on the back side of wafer 2 is stopped, causing the surface temperature of wafer 2 to rise rapidly. In this embodiment, processing is performed with wafer 2 placed on wafer stage 4, but infrared light can also be irradiated while wafer 2 is not in thermal contact with wafer stage 4 using a lifting pin (not shown). After the heating time required to remove the surface reaction layer 404, the infrared lamp 62 is turned off, and the residual gas in processing chamber 1 is exhausted to the outside of processing chamber 1 using exhaust means 15. Thereafter, the supply of helium gas is restarted to improve thermal conductivity between wafer 2 and wafer stage 4, and the wafer temperature is cooled to -20°C by cooler 38, ending the first cycle of processing.

[0076] In response to a command signal from the control unit 40, the infrared lamp 62 is turned off at time t5 as shown in Figure 3. Furthermore, the gas containing reaction product particles and the like within the processing chamber 1 is discharged to the outside of the processing chamber 1 through the vacuum exhaust pipe 16, whose opening is adjusted by the pressure adjustment means 14, and the exhaust means 15. Additionally, as illustrated in Figure 2, after time t5, it is determined whether the etching amount or residual film thickness of the titanium carbide film 402 on the wafer 2 has reached the desired value (corresponding to step S207), and based on the determination result, the next cycle (S201-S206) begins, or the processing of the wafer 2 ends.

[0077] When the next cycle begins, at any time t6 after time t5, in response to a command signal from control unit 40, CF4 / O2 / Ar gas is supplied to discharge region 3 in the same manner as the operation since time t1. That is, as the next cycle, the process of forming the surface reaction layer 404 as illustrated in FIG4(b) and the process of removing the surface reaction layer by heating as illustrated in FIG4(c) are performed again. When the processing of wafer 2 is completed, at time t6, the supply of He gas to the gap between the back side of wafer 2 and the top surface of stage 4 is stopped, and valve 52 is opened to discharge He gas from the gap, so that the pressure in the gap is approximately the same as the pressure in processing chamber 1, and a process including removing static electricity to remove electrostatic adsorption from wafer 2 is performed. This completes the etching process of titanium carbide film 402.

[0078] In this embodiment, when an etching depth of 6 nm is required, the above cycle is repeated five times to complete the etching. Figure 8 is a graph showing the relationship between the number of cycles and the etching depth in the etching process performed by the plasma processing apparatus 100 of this embodiment shown in Figure 1, and the results are shown when the target film is titanium carbide and titanium nitride. The pressure is 50 Pa. In Figure 8, the horizontal axis represents the number of cycles, and the vertical axis represents the etching depth (etch depth) detected by in-situ ellipsometry (polarized light analysis) after the end of each cycle and before the start of the next cycle.

[0079] As shown in Figure 8, in this example, the etching amount changes almost linearly with the increase of the number of cycles. As can be seen from Figure 8, the etching amount of the titanium carbide film in this embodiment per cycle is, for example, 1.2 nm / cycle. Furthermore, in this embodiment, titanium nitride etching is not performed, allowing for selective etching of titanium carbide relative to titanium nitride. Therefore, when a film layer containing titanium carbide and other films containing titanium nitride are disposed on the surface of wafer 2, the etching process performed by the plasma processing apparatus 100 of this embodiment means that the etching of titanium nitride in other films is not performed, allowing for selective etching of titanium carbide in the film layer containing titanium nitride relative to titanium nitride. This is due to the hydrogen-free gas of this disclosure. In the plasma processing process, the gas contains fluorine and oxygen but no hydrogen, therefore no surface reaction layer such as titanium ammonium fluoride is formed on the surface of titanium nitride, and titanium nitride etching is not performed.

[0080] Figure 9 is a graph showing the relationship between the number of cycles and the amount of etching in the etching process performed by the plasma processing apparatus 100 of this embodiment shown in Figure 1. It shows the results when the wafer temperature is varied to -20°C, 0°C, and 20°C. The pressure is 50 Pa. The plasma irradiation time was varied as a parameter to 60 seconds, 90 seconds, and 120 seconds. As shown in Figure 9, when the wafer temperature is as low as -20°C, the amount of etching per cycle does not change even when the plasma irradiation time is changed, indicating that the amount of etching has a self-saturating characteristic relative to the plasma irradiation time. On the other hand, when the wafer temperature is higher, such as 0°C or 20°C, the amount of etching per cycle increases with the increase of the plasma irradiation time, and the amount of etching does not have a self-saturating characteristic relative to the plasma irradiation time. This is because when the wafer temperature is above 0°C, titanium fluoride and other reaction products continue to volatilize during plasma irradiation. From the above results, it can be seen that the wafer temperature range suitable for the process of this disclosure is -40°C to 0°C. That is, the wafer temperature in the process of forming the surface reaction layer 404 is preferably in the range of -40°C to 0°C. The reason for setting the lower limit of the wafer temperature to -40°C is that if the wafer temperature is below -40°C, the temperature range for heating and cooling will expand, the process time will increase, and therefore the wafer throughput will decrease, which is undesirable. In addition, the appropriate range of pressure in the plasma irradiation process is 0.1 Pa to 1000 Pa, and more specifically, the high efficiency of this disclosure has been confirmed in the range of 1 Pa to 100 Pa.

[0081] As described above, both the process of forming the surface reaction layer 404 (first process) and the process of removing the surface reaction layer 404 (second process) in this embodiment have the property of ending in a self-saturating manner. Therefore, in this embodiment, when etching the wafer 2 with the pre-formed circuit pattern film structure, the etching amount on the surface of the titanium carbide film 402 at the end of one cycle can be made more uniform, and the variation in the in-plane direction and depth direction of the wafer 2 is reduced.

[0082] Because of the aforementioned self-saturation characteristic, even if the density of reactive particles such as free radicals supplied to wafer 2 varies depending on their position in the horizontal or depth direction on the upper surface of wafer 2, it is possible to prevent the etching amount from becoming excessive or insufficient, and to reduce variations in the etching amount. Furthermore, the total etching amount can be adjusted by increasing or decreasing the number of repetitions of a cycle (first process and second process) including the aforementioned first and second processes. In this embodiment, the etching amount is a multiple of the etching amount in each cycle or the sum of the number of repetitions. As a result, in this embodiment, compared to etching using conventional continuous plasma processing, the dimensional controllability and yield of the etched product are improved.

[0083] As described above, according to this embodiment, an isotropic atomic layer etching technology can be provided, which can achieve high uniformity in the wafer plane and pattern depth direction for titanium carbide films, and can perform etching processing with high processing size control at the atomic layer level.

[0084] Furthermore, in this embodiment, a titanium carbide film is used as an example of a film layer containing metal carbides. This disclosure is also applicable to titanium carbide films containing other constituent elements, such as oxygen, nitrogen, or both oxygen and nitrogen. Specifically, it applies not only to TiC, but also to films of TiCO, TiCN, TiCNO, etc.

[0085] In the plasma processing apparatus 100 shown in Figure 1 above, the infrared lamp 62 is disposed outside the vacuum container above the processing chamber 1, which surrounds the quartz chamber 12 of the discharge region 3. However, it may also be disposed inside the quartz chamber 12 or the vacuum container. Furthermore, the above examples have been described in detail to illustrate this disclosure in an easily understandable manner, but it is not necessarily limited to having all the configurations described.

[0086] 1: Processing Room 2: Wafer 3: Discharge Region 4: Placement platform 5: Sprayer board 6: Top Slab 10: Plasma 11: Basal compartment 12: Quartz Chamber 14: Pressure Adjustment Methods 15: Exhaust methods 16: Vacuum exhaust pipe 17: Gas Dispersion Plate 20: High-frequency power supply 22: Matcher 25: High-frequency cutoff filter 30: Electrostatic adsorption electrode 31: DC power supply 34: ICP coil 38: Cooler 39: Refrigerant flow path 40: Control Department 41: Calculation Department 50: Mass Flow Controller 51: Mass Flow Controller Control Section 52: Valve 60: Container 62: Infrared Lamp 63: Reflector 64: Power supply for infrared lamps 70: Thermocouple 71: Thermocouple Thermometer 74: Light-transmitting window 75: Gas Flow Path 78: Slotted Plate 81: O-ring 92: Fiber optic 93: External infrared source 94: Optical circuit switch 95: Optical distributor 96: Spectrometer 97: Detector 98: Optical wave combiner 100: Plasma treatment device 401: Basement membrane 402: Titanium carbide film 403: Active strain 404: Surface Reaction Layer 406: Reaction products 901: Substrate Structure 902: Fin Structure 903: Titanium carbide film 904: Mask 905: Reaction species 906: Reaction products

Claims

1. An etching method for etching a film layer containing titanium carbide disposed on a wafer surface, the etching method comprising: supplying reactive particles containing fluorine and oxygen but not hydrogen to the surface of the film layer to form a reactive layer on the surface of the film layer; and heating the film layer to remove the reactive layer.

2. The etching method of claim 1, wherein the reactive particles containing the aforementioned fluorine and oxygen but not hydrogen are formed from a gas composed of tetrafluoromethane and oxygen.

3. The etching method of claim 1, wherein when the aforementioned film layer containing the aforementioned titanium carbide and other film layers containing titanium nitride are disposed on the aforementioned wafer surface, the aforementioned other film layers containing the aforementioned titanium nitride are not etched.

4. The etching method of claim 1, wherein the amount of the aforementioned reactive layer formed has self-saturating characteristics.

5. The etching method of claim 1, wherein a cycle is formed of the process of forming the aforementioned reactive layer and the process of removing the aforementioned reactive layer, and the aforementioned cycle is repeated multiple times.

6. The etching method of claim 1, wherein the wafer temperature during the process of forming the aforementioned reactive layer is in the range of -40°C to 0°C.

7. The etching method of claim 1, wherein the wafer temperature in the process of removing the aforementioned reactive layer is in the range of 50°C to 150°C.

Images