Method for removing natural oxide layer from surface of silicon-based material and plasma treatment apparatus

Abstract

The application discloses a method for removing a natural oxide layer on a silicon-based material surface and a plasma processing device, and comprises the following steps: exciting He, NF3 and NH3 input into a first cavity to generate He metastable particles, F free radicals, NH2 free radicals and NH free radicals, and introducing the He metastable particles into a second cavity through a first ion filtering device; performing metastable excitation on H2 input into the second cavity by the He metastable particles to generate H free radicals, and reacting the H free radicals with the F free radicals to generate HF; and reacting the HF with NH2 free radicals, NH free radicals and H free radicals to generate NH4HF2, and then introducing the NH4HF2 into a third cavity through a second ion filtering device to react with the natural oxide layer on the silicon-based material surface to remove the natural oxide layer. The application can reduce and control the etching rate, and reduce physical sputtering damage to the silicon-based material surface.

Description

Technical Field

[0001] This application relates to the field of semiconductor processing technology, and in particular to a method for removing the natural oxide layer on the surface of silicon-based materials and a plasma processing apparatus. Background Technology

[0002] In semiconductor device manufacturing, silicon (Si)-based materials are highly susceptible to forming a native oxide layer (primarily composed of silicon dioxide (SiO2)) on their surface when exposed to air or oxygen-containing environments. The presence of this oxide layer severely impacts device performance. At advanced nodes, three-dimensional structures such as FinFETs and gate-all-around (GAA) transistors have become mainstream, placing stringent demands on native oxide removal processes for both low damage and high selectivity. Currently, mainstream native oxide removal technologies are mainly divided into wet etching and dry etching. Wet etching often uses diluted hydrofluoric acid (DHF) solution as the etchant. While it can achieve a certain etching selectivity, it suffers from complex operation, high chemical reagent consumption, and the need for extensive deionized water rinsing and drying. Furthermore, the treated Si surface only forms Si-H bonds, making it prone to re-oxidation and particle adsorption, failing to meet the requirements of high-precision processes. Dry etching, primarily using fluorine (F) plasma etching, can selectively remove the native oxide layer. However, the high-energy charges and ions generated during traditional plasma etching can easily cause physical sputtering damage to the Si substrate and introduce lattice defects and dislocations. Simultaneously, excessive F radicals can trigger excessive chemical corrosion of the Si substrate, resulting in insufficient etching selectivity and difficulty in meeting the damage control and etching precision requirements of advanced processes. Therefore, it is necessary to investigate a process method that can significantly improve these problems. Summary of the Invention

[0003] The purpose of this application is to overcome the aforementioned problems in the prior art and to provide a method and plasma treatment equipment for removing the natural oxide layer on the surface of silicon-based materials.

[0004] To achieve the above objectives, the technical solution of this application is as follows: According to a first aspect of this application, embodiments of this application provide a method for removing the natural oxide layer on the surface of a silicon-based material, comprising: He, NF3, and NH3 introduced into the first cavity are excited to generate He metastable particles, F radicals, NH2 radicals, and NH radicals; The He metastable particles, the F radicals, the NH2 radicals, and the NH radicals are introduced into the second cavity through a first ion filter, and the He metastable particles metastablely excite the H2 introduced into the second cavity to generate H radicals. In the second cavity, the H radical reacts with the F radical to generate HF, and the HF reacts with the NH2 radical, the NH radical and the H radical to generate NH4HF2; The NH4HF2 is introduced into the third chamber through the second ion filter device to chemically react with the natural oxide layer on the surface of the silicon-based material placed in the third chamber in order to remove the natural oxide layer. The first ion filter and the second ion filter are used to filter charged particles.

[0005] In some embodiments, NH4F is first generated by reacting the HF with the NH2 radical, the NH radical and the H radical, and then the NH4F is reacted with the HF to further generate NH4HF2.

[0006] In some embodiments, the content of the generated NH4F is controlled by adjusting the flow ratio of the NF3 and the NH3.

[0007] In some embodiments, the generation rate of HF is regulated by adjusting the flow rate of H2, thereby controlling the yield of NH4HF2.

[0008] In some embodiments, the concentration of NH4HF2 is controlled by adjusting the flow rate of He.

[0009] In some embodiments, the flow ratio of NF3 to NH3 is 1:1 to 1:2.5.

[0010] In some embodiments, the flow ratio of H2 to NF3 is 1:1 to 3:1.

[0011] In some embodiments, the flow rate of NF3 is 10 sccm to 200 sccm.

[0012] In some embodiments, the flow rate of NH3 is 10 sccm to 300 sccm.

[0013] In some embodiments, the flow rate of H2 is 50 sccm to 500 sccm.

[0014] In some embodiments, the flow rate of He is 50 sccm to 500 sccm.

[0015] In some embodiments, when the reaction removes the natural oxide layer, the source power is 800W to 2000W, the pressure is 5mTorr to 50mTorr, the temperature is 50℃ to 250℃, and the time is 30s to 120s.

[0016] In some embodiments, the first ion filtering device is provided with a single-layer filter plate, and the second ion filtering device is provided with a double-layer filter plate. The first pore density of the grid holes provided on the single-layer filter plate is less than the second pore density of the grid holes provided on the double-layer filter plate. The He metastable particles, the F free radicals, the NH2 free radicals, and the NH free radicals are introduced into the second cavity through the grid holes provided on the single-layer filter plate, and the NH4HF2 is introduced into the third cavity through the grid holes provided on the double-layer filter plate. The single-layer filter plate and the double-layer filter plate are used to filter charged particles.

[0017] In some embodiments, the first pore density is 30 pores / cm². 2 ~100 pieces / cm 2 .

[0018] In some embodiments, the second pore density is 400 pores / cm². 2 ~600 pieces / cm 2 .

[0019] In some embodiments, the natural oxide layer is removed by chemically reacting the NH4HF2 with the natural oxide layer to generate volatile (NH4)2SiF6.

[0020] According to a second aspect of this application, embodiments of this application also provide a plasma processing device, including a first cavity, a second cavity, and a third cavity, wherein a first ion filtering device is provided between the first cavity and the second cavity, and a second ion filtering device is provided between the second cavity and the third cavity, and the plasma processing device is used to perform a method for removing the natural oxide layer on the surface of a silicon-based material as provided in any embodiment of the first aspect above.

[0021] The embodiments of this application may have, or at least have, the following advantages: (1) By introducing the He metastable particles, F radicals, NH2 radicals and NH radicals generated in the first cavity into the second cavity, and by using the He metastable particles to metastablely excite the H2 introduced into the second cavity to generate H radicals, the H radicals can be used to actively generate HF by reacting with the F radicals, thereby reducing the concentration of F radicals in the system and laying a foundation for achieving high selectivity etching of oxides and silicon at the chemical level. In the second cavity, the generated HF reacts with NH2 radicals, NH radicals and H radicals in a stepwise reaction to synthesize NH4HF2, which has a high selectivity to the natural oxide layer, and can also consume high-energy particles. When NH4HF2 finally reacts with the natural oxide layer, it basically achieves the fine removal of the natural oxide layer by chemical etching, thereby improving the etching selectivity and reducing etching damage.

[0022] (2) By adjusting the flow ratio of NF3 and NH3, as well as the flow rates of H2 and He, the yield and concentration of NH4HF2 can be controlled by regulating the content of NH4F and the generation rate of HF, thereby achieving precise control of the etching rate when removing the natural oxide layer and preventing damage to the surface of silicon-based materials caused by over-etching.

[0023] (3) By sequentially setting the first ion filter device and the second ion filter device, and making the ion filtering capacity of the second ion filter device higher than that of the first ion filter device, high-energy charges and ions can be effectively annihilated through stepwise filtration, and the reaction to synthesize NH4HF2 can be completed in the second cavity, which significantly reduces the physical sputtering damage to silicon-based materials.

[0024] In summary, the embodiments of this application can achieve chemical etching removal of the natural oxide layer on the surface of silicon-based materials with controllable rate and high selectivity, and can effectively avoid damage to the surface of silicon-based materials. Therefore, it well meets the requirements of advanced processes for damage control and etching accuracy.

[0025] Other advantages of this application will be described in the following detailed description. Attached Figure Description

[0026] Figure 1 This is a flowchart of a method for removing the natural oxide layer on the surface of a silicon-based material, provided as a preferred embodiment of this application.

[0027] Figure 2 This is a schematic diagram of the structure of a plasma processing device provided in a preferred embodiment of this application.

[0028] In the figure: 10. Processing object; 11. Third cavity; 12. Second cavity; 13. First cavity; 21. Second air inlet; 22. First air inlet; 31. First ion filter device; 32. Second ion filter device; 33. Grille hole. Detailed Implementation

[0029] To address the problems of existing techniques for removing native oxide layers, such as the complexity of wet etching, its susceptibility to re-oxidation and particle adsorption, and its inability to meet high-precision process requirements, and the issues of dry etching causing physical sputtering damage to the Si substrate, insufficient etching selectivity, and difficulty in meeting the damage control and etching precision requirements of advanced processes, this application provides a method for removing the native oxide layer on the surface of silicon-based materials, including: He, NF3, and NH3 introduced into the first cavity are excited to generate He metastable particles, F radicals, NH2 radicals, and NH radicals; The He metastable particles, the F radicals, the NH2 radicals, and the NH radicals are introduced into the second cavity through a first ion filter, and the He metastable particles metastablely excite the H2 introduced into the second cavity to generate H radicals. In the second cavity, the H radical reacts with the F radical to generate HF, and the HF reacts with the NH2 radical, the NH radical and the H radical to generate NH4HF2; The NH4HF2 is introduced into the third chamber through the second ion filter device to chemically react with the natural oxide layer on the surface of the silicon-based material placed in the third chamber in order to remove the natural oxide layer. The first ion filter and the second ion filter are used to filter charged particles.

[0030] This application embodiment generates H radicals by metastable excitation of introduced H2 in a second chamber with multi-channel ion filtration. The H radicals can react with F radicals to actively generate HF, reducing the concentration of F radicals in the system. Furthermore, the stepwise synthesis of NH4HF2 with high selectivity to the native oxide layer (mainly composed of silicon dioxide (SiO2)) in the second chamber can consume high-energy particles, enabling precise control of the etching rate when removing the native oxide layer and significantly reducing physical sputtering damage to silicon-based materials. Therefore, it well meets the requirements of advanced processes for damage control and etching precision.

[0031] This application also provides a plasma processing apparatus for performing the above-described method for removing the natural oxide layer on the surface of a silicon-based material.

[0032] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0033] refer to Figure 1 In a first aspect, embodiments of this application provide a method for removing the natural oxide layer on the surface of a silicon-based material, which may sequentially include the following steps: Step S11: Excite He, NF3 and NH3 introduced into the first cavity to generate He metastable particles, F radicals, NH2 radicals and NH radicals.

[0034] refer to Figure 2 In some embodiments, a first cavity 13 may be used, and He (helium), NF3 (nitrogen trifluoride), and NH3 (ammonia) may be introduced into the first cavity 13 through a first air inlet 22 provided on the first cavity 13. Figure 2 The three vertical hollow arrows at point 22 of the first air intake point indicate this.

[0035] In some embodiments, a plasma processing device may be used to implement the method for removing the natural oxide layer on the surface of a silicon-based material provided in the embodiments of this application. The plasma processing device may be an inductively coupled plasma (ICP) processing device, etc., but is not limited thereto. The first cavity 13 may be a plasma generating cavity of the plasma processing device, such as an inductively coupled plasma (ICP) cavity.

[0036] In some embodiments, plasma is formed by exciting He, NF3, and NH3 introduced into the first cavity 13. After He, NF3, and NH3 are excited in the first cavity 13, the resulting plasma may contain He metastable particles (He(2...). 3 Neutral particles such as S (S), F radical (F·), NH2 radical (NH2·), and NH radical (NH·), as well as various ions and charged particles such as electrons. Among them, He metastable particles can be generated by excited He, F radicals can be generated by excited NF3, and NH2 radicals and NH radicals can be generated by excited NH3.

[0037] Step S12: Introduce He metastable particles, F radicals, NH2 radicals and NH radicals into the second chamber through the first ion filter device.

[0038] In some embodiments, a second cavity 12 may be provided below the first cavity 13, and the second cavity 12 may be an indirect reaction cavity of the plasma processing device. Furthermore, the plasma processing device may be equipped with an ion filtering device. The ion filtering device may include a first ion filtering device 31 disposed between the first cavity 13 and the second cavity 12. In other words, the first ion filtering device 31 constitutes the bottom surface of the first cavity 13, and simultaneously constitutes the top surface of the second cavity 12.

[0039] In some embodiments, the first ion filtering device 31 may be provided with a first filter plate, on the surface of which a plurality of grid holes 33 are provided at a certain distribution density. Thus, the first cavity 13 can be connected to the second cavity 12 through the grid holes 33 provided on the first filter plate. The first filter plate may be made of a metal material (e.g., aluminum) and grounded. Therefore, by providing a grounded first filter plate with grid holes 33, the first ion filtering device 31 has the function of filtering charged particles in the plasma and allowing neutral particles in the plasma to pass through when plasma (gas) passes through. Preferably, the first filter plate may be horizontally disposed between the first cavity 13 and the second cavity 12.

[0040] In some embodiments, the first filter plate may include a single-layer filter plate.

[0041] In some embodiments, a first ion filter device 31 (single-layer filter plate) can be used to ion filter the plasma formed in the first cavity 13. When the plasma passes through the grid holes 33 of the first ion filter device 31, at least a portion of the charged particles contained in the plasma will be filtered out by the metal grids on the first ion filter device 31 and will therefore not enter the second cavity 12. Neutral particles contained in the plasma, including He metastable particles, F radicals, NH2 radicals, and NH radicals, will be uniformly introduced into the second cavity 12 after passing through the grid holes 33 on the first ion filter device 31.

[0042] By providing a first ion filter 31 between the first cavity 13 and the second cavity 12, the plasma formed in the first cavity 13 is ion filtered. This filters out at least part of the high-energy ions and charges in the excited plasma, causing these high-energy ions and charges to annihilate on the surface of the metal grid, and uniformly dispersing the neutral particles in the plasma into the lower second cavity 12. By removing at least part of the high-energy ions and charges from the plasma beforehand, the concentration and kinetic energy of the high-energy ions and charges are greatly reduced, lowering the probability of these high-energy ions and charges moving to the surface of the object being processed (Si substrate / wafer), thereby reducing physical sputtering damage to the surface of the object being processed.

[0043] Step S13: Metastable excitation of H2 introduced into the second cavity is performed by He metastable particles to generate H free radicals.

[0044] In some embodiments, H2 (hydrogen gas) can be introduced into the second cavity 12 through a second air inlet 21 located on the side of the second cavity 12, such as... Figure 2 The horizontal hollow arrow at the second air intake 21 points to this location.

[0045] When He metastable particles enter the second chamber 12 from the first chamber 13 through the first ion filter 31, they come into contact with H2 introduced into the second chamber 12, a Penning ionization effect occurs. Through collisions between the He metastable particles and hydrogen molecules, the energy of the He metastable particles is transferred to the hydrogen molecules, causing ionization and generating H radicals. The He metastable particles then de-excite themselves after the energy transfer. Therefore, in the second chamber 12, the metastable state excitation of hydrogen molecules can be achieved by colliding He metastable particles with H2 introduced into the second chamber 12, thereby obtaining the desired active H radicals.

[0046] The H radicals obtained by the above steps are an important raw material for synthesizing etching precursors with high selectivity for SiO2.

[0047] By indirectly exciting H2 using He metastable particles, the energy of the generated H radicals can be reduced. This decreases the kinetic energy of the H radicals, thus minimizing physical sputtering damage even if H radicals escape from the second cavity 12 and reach the surface of the object being treated. Furthermore, the excited H2 also acts to consume high-energy particles.

[0048] Step S14: In the second chamber, H radicals react with F radicals to generate HF, and HF reacts with NH2 radicals, NH radicals and H radicals to generate NH4HF2.

[0049] In some embodiments, H2 is indirectly excited by He metastable particles in the second cavity 12 to generate H radicals. These H radicals then react with F radicals from the first cavity 13 in the second cavity 12 to further generate HF. The reaction formula is as follows: H· + F· → HF HF, obtained by reacting H radicals and F radicals in the second cavity 12, is used as an intermediate reactant in the synthesis of an etching precursor with high selectivity for SiO2.

[0050] By actively generating HF through the reaction of H radicals and F radicals, the concentration of F radicals in the system can be significantly reduced. At the same time, some high-energy particles are consumed, avoiding the direct etching effect of F radicals on the silicon material on the surface of the object being treated. This lays a foundation for achieving high selectivity etching of oxides (SiO2) and silicon at the chemical level.

[0051] In some embodiments, after obtaining HF through the reaction, it can be further reacted with NH2 radicals, NH radicals and H radicals in the second chamber 12 to generate NH4HF2 (ammonium hydrogen fluoride). NH4HF2 is the desired etching precursor with high selectivity for SiO2.

[0052] In some embodiments, NH4F (ammonium fluoride) is first generated by reacting HF with NH2 radicals, NH radicals, and H radicals, and then NH4F is reacted with HF to further generate the desired NH4HF2. NH2 radicals and NH radicals, as active intermediates, can react rapidly with the generated HF when entering the second chamber 12 from the first chamber 13, accelerating the formation rate of NH4F.

[0053] The reaction of HF with NH2 radicals, NH radicals, and H radicals can include the following stepwise reaction process: HF reacts with NH2 radicals and H radicals to produce NH4F, as shown in the following reaction equation: HF + NH2· + H· → NH4F HF reacts with NH radicals and H radicals to produce NH4F, as shown in the following reaction formula: HF + NH· + 2H· → NH4F NH4F reacts with HF to further generate the desired NH4HF2, as shown in the following reaction formula: NH4F + HF → NH4HF2 In the second cavity 12, NH4HF2 is synthesized by stepwise reaction of the generated HF with NH2 radicals, NH radicals and H radicals. This process can consume high-energy particles and avoid the direct etching effect of these high-energy particles on the silicon material on the surface of the object being treated.

[0054] The above-mentioned process of NH4F reacting with HF to generate NH4HF2 is an equilibrium reaction in the gas phase. When the concentrations of HF and NH4F are high enough, NH4HF2 can be homogeneously generated in the gas phase within the second chamber 12.

[0055] In some embodiments, the etching rate during the removal of the native oxide layer can be precisely controlled by controlling the amount of NH4HF2 generated.

[0056] In some embodiments, the ratio of NF3 and NH3 introduced into the first cavity 13 can be adjusted to regulate the proportion of F free radicals, NH2 free radicals and NH free radicals generated by the excitation, thereby controlling the content of NH4F generated in the second cavity 12, so as to control the amount of NH4HF2 generated.

[0057] In some embodiments, the generation rate of HF can be controlled by adjusting the flow rate of H2 introduced into the second cavity 12, thereby controlling the yield of NH4HF2. The higher the HF generation rate, the faster the reaction to generate NH4F, and the higher the yield of NH4HF2.

[0058] In some embodiments, the flow rate of He introduced into the first cavity 13 can be adjusted so that He serves as both a metastable excitation gas and a dilution carrier gas, thereby controlling the concentration of each intermediate reactant and the final concentration of NH4HF2 before the reaction.

[0059] In some embodiments, the internal temperature of the second cavity 12 can be independently adjusted by providing a temperature control device on the second cavity 12, so as to control the generation of NH4HF2 through temperature control (NH4HF2 is more likely to condense or be generated at lower temperatures).

[0060] In some embodiments, the flow ratio of NF3 to NH3 is 1:1 to 1:2.5. For example, the flow ratio of NF3 to NH3 may be 1:1, 1:1.1, 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2, 1:2.1, 1:2.3 or 1:2.5, or any flow ratio between any two of the aforementioned flow ratios.

[0061] In some embodiments, the flow ratio of H2 to NF3 is 1:1 to 3:1. For example, the flow ratio of H2 to NF3 may be 1:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 1.9:1, 2:1, 2.1:1, 2.3:1, 2.5:1, 2.7:1, 2.9:1, or 3:1, or any flow ratio between any two of the aforementioned flow ratios.

[0062] In some embodiments, the flow rate of NF3 is 10 sccm to 200 sccm. For example, the flow rate of NF3 can be 10 sccm, 30 sccm, 50 sccm, 70 sccm, 90 sccm, 100 sccm, 130 sccm, 150 sccm, 170 sccm, 190 sccm or 200 sccm, or any value between any two of the aforementioned flow rate values.

[0063] In some embodiments, the flow rate of NH3 is 10 sccm to 300 sccm. For example, the flow rate of NH3 can be 10 sccm, 20 sccm, 60 sccm, 100 sccm, 120 sccm, 160 sccm, 190 sccm, 200 sccm, 210 sccm, 250 sccm, 280 sccm or 300 sccm, or any value between any two of the aforementioned flow rate values.

[0064] In some embodiments, the flow rate of H2 is 50 sccm to 500 sccm. For example, the flow rate of H2 can be 50 sccm, 70 sccm, 90 sccm, 100 sccm, 120 sccm, 150 sccm, 180 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, or 500 sccm, or any value between any two of the aforementioned flow rate values.

[0065] In some embodiments, the flow rate of He is 50 sccm to 500 sccm. For example, the flow rate of He can be 50 sccm, 80 sccm, 100 sccm, 130 sccm, 160 sccm, 185 sccm, 205 sccm, 255 sccm, 305 sccm, 355 sccm, 405 sccm, 455 sccm or 500 sccm, or any value between any two of the aforementioned flow rate values.

[0066] Thus, by coordinating the above-mentioned flow ratio and flow rate, the amount of NH4HF2 generated can be controlled, and the etching rate during the removal of the natural oxide layer can be precisely controlled, preventing damage to the silicon-based material surface caused by over-etching.

[0067] Step S15: NH4HF2 is introduced into the third chamber through the second ion filter device to chemically react with the natural oxide layer on the surface of the silicon-based material placed in the third chamber, thereby removing the natural oxide layer.

[0068] In some embodiments, a third cavity 11 may be provided below the second cavity 12, and the third cavity 11 may be a process chamber of a plasma processing device. Furthermore, the ion filtering device may also include a second ion filtering device 32 disposed between the second cavity 12 and the third cavity 11. In other words, the second ion filtering device 32 constitutes the bottom surface of the second cavity 12, and simultaneously constitutes the top surface of the third cavity 11.

[0069] The processing object 10 is placed in the third cavity 11 to undergo processing. The processing object 10 can be a silicon substrate or a wafer. The silicon substrate or wafer can be placed horizontally on a stage in the third cavity 11. The silicon substrate or wafer may have a silicon-based material surface, or a device structure (e.g., a fin structure) of silicon-based material may be formed on the silicon substrate or wafer, thus the device structure has a silicon-based material surface. When a natural oxide layer is formed on the surface of the silicon-based material, the silicon substrate or wafer becomes the processing object 10 from which the natural oxide layer needs to be removed. The method for removing the natural oxide layer on the surface of a silicon-based material provided in this application embodiment can be used to remove the natural oxide layer formed on the surface of the silicon-based material of the processing object 10 (silicon substrate or wafer).

[0070] In some embodiments, the second ion filtering device 32 may be provided with a second filter plate, on the surface of which a plurality of grid holes 33 are provided at a certain distribution density. Thus, the second cavity 12 can be connected to the third cavity 11 through the grid holes 33 provided on the second filter plate. The second filter plate may be made of a metal material (e.g., aluminum) and grounded. Therefore, by providing a grounded second filter plate with grid holes 33, the second ion filtering device 32 has the function of filtering charged particles in the gas passing through the second cavity 12, while allowing neutral particles in the gas to pass through. Preferably, the second filter plate may be horizontally disposed between the second cavity 12 and the third cavity 11.

[0071] In some embodiments, the second filter plate may include a double-layer filter plate arranged in parallel. That is, the second filter plate includes two single-layer filter plates arranged in parallel, and each filter plate (each single-layer filter plate) may have multiple grid holes 33 arranged on its surface at a certain distribution density. Preferably, the grid holes 33 on the two filter plates (two single-layer filter plates) of the second filter plate are staggered vertically, such as... Figure 2 As shown.

[0072] In some embodiments, a second ion filter device 32 (double-layer filter plate) can be used to ion filter the gas in the second chamber 12. When the gas in the second chamber 12 passes through the grid holes 33 of the second ion filter device 32, the charged particles contained therein can be basically filtered out by the double-layer metal grid on the second ion filter device 32, and therefore will not enter the third chamber 11. The NH4HF2, which is a reaction product, and the remaining small amount of neutral particles that did not participate in the reaction will be uniformly introduced into the third chamber 11 after passing through the double-layer grid holes 33 on the second ion filter device 32. The NH4HF2 generated by the controlled reaction will then undergo a chemical reaction with the natural oxide layer on the surface of the silicon-based material of the object being processed 10, and the etching rate can be precisely controlled.

[0073] By setting a second ion filter 32 between the second chamber 12 and the third chamber 11, the residual high-energy ions and charges in the second chamber 12 can be further filtered and removed, causing these residual high-energy ions and charges to annihilate on the surface of the metal grid. This allows the generated NH4HF2 to be uniformly dispersed in the lower third chamber 11, achieving a uniform removal reaction. Through two-step ion filtration, almost all high-energy ions and charges in the plasma can be effectively removed. Furthermore, by synthesizing NH4HF2 in a stepwise reaction in the second chamber 12, high-energy particles are further consumed. Through these measures, when NH4HF2 finally reacts with the native oxide layer, the removal of the native oxide layer is achieved primarily through chemical etching, resulting in a fine and controllable removal. This not only improves the etching selectivity but also significantly reduces etching damage.

[0074] In some embodiments, when performing the method for removing the natural oxide layer on the surface of silicon-based materials, the source power, pressure, temperature, time, etc. can be adjusted by plasma processing equipment, and the pore density of the grid holes 33 of the ion filter device can be set at different levels. In conjunction with the flow rate adjustment of NF3, NH3, He, and H2, better and more precise control over the generation amount of NH4HF2 and the etching rate can be achieved.

[0075] In some embodiments, when the plasma treatment device removes the native oxide layer, the source power is set to 800W to 2000W. For example, the source power can be 800W, 900W, 1000W, 1200W, 1500W, 1700W, 1900W, or 2000W, or any value between any two of the aforementioned power values.

[0076] In some embodiments, when the plasma treatment device removes the native oxide layer, the pressure is set to 5 mTorr to 50 mTorr. For example, the pressure can be 5 mTorr, 6 mTorr, 8 mTorr, 10 mTorr, 15 mTorr, 20 mTorr, 25 mTorr, 30 mTorr, 35 mTorr, 40 mTorr, 45 mTorr, or 50 mTorr, or any value between any two of the aforementioned pressure values.

[0077] In some embodiments, when the plasma treatment device is used to remove the natural oxide layer, the temperature is set to 50°C to 250°C. For example, the temperature may be 50°C, 70°C, 90°C, 100°C, 110°C, 130°C, 150°C, 180°C, 200°C, 230°C, or 250°C, or any value between any two of the aforementioned temperature values.

[0078] In some embodiments, the plasma treatment device is set to a time of 30s to 120s when the reaction removes the natural oxide layer. For example, the time can be 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, or 120s, or any value between any two of the aforementioned time values.

[0079] In some embodiments, the grid holes 33 on the single-layer filter plate of the first ion filter device 31 have a first pore density, and the grid holes 33 on each layer of the double-layer filter plate of the second ion filter device 32 have a second pore density, wherein the first pore density is less than the second pore density. This achieves stepwise filtration and removal of high-energy charged particles in the plasma without affecting the synthesis of NH4HF2 in the second cavity 12.

[0080] In some embodiments, the first pore density is 30 pores / cm³. 2~100 pieces / cm 2 For example, the density of the first pore can be 30 pores / cm³. 2 40 pieces / cm 2 50 pieces / cm 2 60 pieces / cm 2 70 pieces / cm 2 80 pieces / cm 2 90 pieces / cm 2 Or 100 pieces / cm 2 etc., or any value between any two of the aforementioned pore density values.

[0081] In some embodiments, the second pore density is 400 pores / cm³. 2 ~600 pieces / cm 2 For example, the density of the second pore can be 400 pores / cm³. 2 410 pieces / cm 2 450 pieces / cm 2 480 pieces / cm 2 500 pieces / cm 2 520 pieces / cm 2 550 pieces / cm 2 580 pieces / cm 2 Or 600 pieces / cm 2 etc., or any value between any two of the aforementioned pore density values.

[0082] By synergistically controlling the source power, pressure, temperature, time, pore density, etc., and adjusting the flow rates of NF3, NH3, He, and H2, it is possible to achieve better and more precise control over the generation amount and etching rate of NH4HF2, thereby achieving high selectivity etching of SiO2 / Si at the chemical level, while reducing physical sputtering damage to the Si substrate.

[0083] In some embodiments, by setting the second pore density to be greater than the first pore density, not only can the ion filtration capacity of the second ion filter device 32 be higher than that of the first ion filter device 31, so as to effectively annihilate high-energy charges and ions through stepwise filtration, but also a pressure difference can be formed between the first ion filter device 31 and the second ion filter device 32, forming a gas storage space in the second cavity 12, which can slow down the rate of gas outflow from the second cavity 12, effectively promoting the reaction of synthesizing NH4HF2 to be fully completed in the second cavity 12, and the yield is controllable, thereby helping to reduce the content of unreacted high-energy particles and minimizing the physical sputtering damage to silicon-based materials.

[0084] In some embodiments, by providing the second ion filter device 32 with a double-layer filter plate, a fourth cavity can be formed between the two filter plates, and the grid holes 33 on the two filter plates are staggered vertically, which can disturb the NH4HF2 passing through the double-layer filter plate, thereby playing a role in uniform gas distribution, further improving the reaction uniformity of NH4HF2, thereby improving the uniformity of removal of the natural oxide layer and preventing the occurrence of local over-etching.

[0085] In some embodiments, the natural oxide layer on the surface of the silicon-based material is removed by causing NH4HF2 entering the third chamber 11 to undergo a controlled chemical reaction with the native oxide layer on the surface of the silicon-based material placed in the third chamber 11, generating volatile (NH4)2SiF6. The reaction formula is as follows: SiO2 + 2NH4HF2 → (NH4)2SiF6 +2H2O In summary, this embodiment of the application efficiently reduces the concentration of F radicals by setting up a second cavity 12 and generating a large amount of HF in situ after exciting H2 with metastable He particles within the second cavity 12. Simultaneously, high-selectivity etching of the natural oxide layer on the silicon-based material surface is achieved through stepwise synthesis of NH4HF2 within the second cavity 12. Furthermore, by using an ion filter device with a metal grid for graded filtration, high-energy charges / ions are almost completely annihilated along their path from the top of the cavity (first cavity 13) to the bottom of the cavity (third cavity 11), essentially avoiding physical sputtering damage. Therefore, this embodiment of the application is distinctly different from traditional techniques that use plasma as the direct reactant or employ remote plasma methods to remove the natural oxide layer.

[0086] In a second aspect, embodiments of this application also provide a plasma processing apparatus for performing a method for removing the natural oxide layer on the surface of a silicon-based material as provided in any of the embodiments of the first aspect above.

[0087] refer to Figure 2 In some embodiments, the plasma processing apparatus may include, from top to bottom, a first cavity 13, a second cavity 12, and a third cavity 11, and is provided with an ion filtering device. The ion filtering device may include a first ion filtering device 31 disposed between the first cavity 13 and the second cavity 12, and a second ion filtering device 32 disposed between the second cavity 12 and the third cavity 11. The plasma processing apparatus may be an inductively coupled plasma (ICP) processing apparatus, etc., but is not limited to this.

[0088] The first cavity 13 can be a plasma generation cavity of a plasma processing device, such as an inductively coupled plasma (ICP) cavity. A first air inlet 22 is provided on the top of the first cavity 13 for introducing He (helium), NF3 (nitrogen trifluoride), and NH3 (ammonia) into the first cavity 13 through the first air inlet 22. By activating the plasma generation function of the plasma processing device, the He, NF3, and NH3 introduced into the first cavity 13 are excited to form He metastable particles (He(2... 3 The plasma consists of neutral particles such as S radicals (F·), F radicals (F·), NH2 radicals (NH2·), and NH radicals (NH·), as well as various ions and charged particles such as electrons.

[0089] The second chamber 12 can be an indirect reaction chamber of a plasma processing device. A second air inlet 21 can be provided on the side of the second chamber 12 for introducing H2 (hydrogen gas) into the second chamber 12 through the second air inlet 21, and generating H free radicals by metastable He particles exciting H2 in a metastable state, so as to synthesize NH4HF2 (ammonium hydrogen fluoride), an etching precursor with high selectivity for the natural oxide layer (SiO2) on the surface of the silicon-based material on the object being processed 10, in the second chamber 12.

[0090] The third chamber 11 can be a process chamber of a plasma processing apparatus, in which the object to be processed 10 is placed to receive process processing. When performing a method for removing the natural oxide layer on the surface of a silicon-based material, the plasma processing apparatus can remove the natural oxide layer generated on the surface of the silicon-based material of the object to be processed 10 (silicon substrate or wafer).

[0091] The first ion filtering device 31 can be equipped with a grounded metal single-layer filter plate. Multiple grid holes 33 can be arranged on the surface of the single-layer filter plate at a certain distribution density for ion filtering of the plasma formed in the first cavity 13. This can at least partially filter out high-energy ions and charges in the excited plasma, causing these high-energy ions and charges to annihilate on the metal grid surface. Neutral particles such as He metastable particles, F radicals, NH2 radicals, and NH radicals in the plasma are uniformly dispersed into the lower second cavity 12. By pre-removing at least a portion of the high-energy ions and charges in the plasma, the concentration and kinetic energy of the high-energy ions and charges are greatly reduced, lowering the probability of these high-energy ions and charges moving to the surface of the object being processed 10 (Si substrate / wafer), thereby reducing physical sputtering damage to the surface of the object being processed 10.

[0092] The second ion filtering device 32 may be equipped with a grounded metal double-layer filter plate. Multiple grid holes 33 may be arranged on the surface of the double-layer filter plate at a certain distribution density for ion filtering of the gas in the second chamber 12. This filters out charged particles and allows neutral particles, including NH4HF2, to pass through and enter the lower third chamber 11. By setting up the second ion filtering device 32, residual high-energy ions and charges in the second chamber 12 can be further filtered and removed, and the generated NH4HF2 can be uniformly dispersed in the lower third chamber 11, achieving a uniform removal reaction.

[0093] The first ion filter 31 has a single-layer filter plate with a grid hole density 33 having a first pore density, while the second ion filter 32 has a double-layer filter plate with a grid hole density 33 having a second pore density, where the first pore density is less than the second pore density. This allows for the stepwise filtration and removal of high-energy charged particles from the plasma without affecting the synthesis of NH4HF2 in the second chamber 12. It effectively promotes the complete completion of the NH4HF2 synthesis reaction in the second chamber 12 with controllable yield, reducing the content of unreacted high-energy particles, minimizing physical sputtering damage to silicon-based materials, improving the reaction uniformity of NH4HF2, and preventing localized over-etching.

[0094] Therefore, through two-step ion filtration, almost all high-energy ions and charges in the plasma can be effectively removed. Furthermore, by synthesizing NH4HF2 through stepwise reaction in the second chamber 12, high-energy particles are further consumed. This allows NH4HF2 to achieve a fine and controllable removal of the natural oxide layer by means of chemical etching when it finally reacts with the natural oxide layer. This not only improves the etching selectivity but also significantly reduces etching damage.

[0095] When performing the method of removing the natural oxide layer on the surface of silicon-based materials, the source power, pressure, temperature, time, etc. can be controlled by plasma processing equipment, and the pore density of the grid holes 33 of the ion filter device can be differentiated at different levels. Combined with the flow rate adjustment of NF3, NH3, He, and H2, better and more precise control of the amount of NH4HF2 generated and the etching rate can be achieved, realizing high selectivity etching of SiO2 / Si at the chemical level, while reducing physical sputtering damage to the Si substrate.

[0096] In summary, this embodiment of the application introduces the He metastable particles, F radicals, NH2 radicals, and NH radicals generated in the first cavity 13 into the second cavity 12. The He metastable particles metastablely excite the H2 introduced into the second cavity 12 to generate H radicals. The H radicals react with the F radicals to actively generate HF, reducing the concentration of F radicals in the system. This lays the foundation for achieving high selectivity etching of oxides and silicon at the chemical level. In the second cavity 12, the generated HF reacts with NH2 radicals, NH radicals, and H radicals in a stepwise reaction to synthesize NH4HF2, which has a high selectivity to the native oxide layer, and can also consume high-energy particles. Through stepwise filtration, high-energy charges and ions are effectively annihilated, and the reaction to synthesize NH4HF2 can be completed in the second cavity 12, significantly reducing physical sputtering damage to silicon-based materials. This allows the generated NH4HF2 to achieve a fine removal of the natural oxide layer primarily through chemical etching when it reacts with the natural oxide layer. It also enables precise control of the etching rate during the removal of the natural oxide layer, ultimately improving the etching selectivity and reducing etching damage, thus well meeting the requirements of advanced processes for damage control and etching precision.

[0097] The above are merely preferred embodiments of this application. These embodiments are not intended to limit the scope of protection of this application. Therefore, any equivalent changes made based on the description and drawings of this application should also be included within the scope of protection of this application.

Claims

1. A method for removing the natural oxide layer from the surface of a silicon-based material, characterized in that, include: He, NF3, and NH3 introduced into the first cavity are excited to generate He metastable particles, F radicals, NH2 radicals, and NH radicals; The He metastable particles, the F radicals, the NH2 radicals, and the NH radicals are introduced into the second cavity through a first ion filter, and the He metastable particles metastablely excite the H2 introduced into the second cavity to generate H radicals. In the second cavity, the H radical reacts with the F radical to generate HF, and the HF reacts with the NH2 radical, the NH radical and the H radical to generate NH4HF2; The NH4HF2 is introduced into the third chamber through the second ion filter device to chemically react with the natural oxide layer on the surface of the silicon-based material placed in the third chamber in order to remove the natural oxide layer. The first ion filter and the second ion filter are used to filter charged particles.

2. The method of claim 1, wherein the method further comprises: By reacting the HF with the NH2 radical, the NH radical, and the H radical, NH4F is first generated, and then the NH4F is reacted with the HF to further generate NH4HF2.

3. The method of claim 2, wherein the method further comprises: The content of NH4F generated is controlled by adjusting the flow rate ratio of NF3 and NH3; and / or the generation rate of HF is regulated by adjusting the flow rate of H2 to control the yield of NH4HF2; and / or the concentration of NH4HF2 is controlled by adjusting the flow rate of He.

4. The method of claim 3, wherein the method further comprises: The flow rate ratio of NF3 to NH3 is 1:1 to 1:2.5; and / or, the flow rate ratio of H2 to NF3 is 1:1 to 3:

1.

5. The method of claim 3, wherein the method further comprises: The flow rate of NF3 is 10 sccm to 200 sccm; and / or, the flow rate of NH3 is 10 sccm to 300 sccm; and / or, the flow rate of H2 is 50 sccm to 500 sccm; and / or, the flow rate of He is 50 sccm to 500 sccm.

6. The method of claim 1, wherein the method further comprises: When the reaction removes the natural oxide layer, the source power is 800W to 2000W, the pressure is 5mTorr to 50mTorr, the temperature is 50℃ to 250℃, and the time is 30s to 120s.

7. The method of claim 1, wherein the method further comprises: The first ion filtration device is provided with a single-layer filter plate, and the second ion filtration device is provided with a double-layer filter plate. The first pore density of the grid holes provided on the single-layer filter plate is less than the second pore density of the grid holes provided on the double-layer filter plate. The He metastable particles, the F free radicals, the NH2 free radicals and the NH free radicals are introduced into the second cavity through the grid holes provided on the single-layer filter plate, and the NH4HF2 is introduced into the third cavity through the grid holes provided on the double-layer filter plate. The single-layer filter plate and the double-layer filter plate are used to filter charged particles.

8. The method of removing a natural oxide layer from a surface of a silicon-based material of claim 7, wherein, the first hole density is 30 / cm 2 ~ 100 / cm 2 ; and / or, the second hole density is 400 / cm 2 ~ 600 / cm 2 .

9. The method of claim 1, wherein the method further comprises: The natural oxide layer is removed by chemically reacting the NH4HF2 with the natural oxide layer to generate volatile (NH4)2SiF6.

10. A plasma processing apparatus, characterized by, The plasma treatment equipment includes a first cavity, a second cavity, and a third cavity. A first ion filter is provided between the first cavity and the second cavity, and a second ion filter is provided between the second cavity and the third cavity. The plasma treatment equipment is used to perform the method for removing the natural oxide layer on the surface of silicon-based materials as described in any one of claims 1-9.

Images