Polysilicon removal method and diffusion furnace

Abstract

The application provides a polysilicon removal method and a diffusion furnace, and relates to the technical field of semiconductors. First, a medium layer and polysilicon are grown on the surface of an epitaxial wafer, wherein the epitaxial wafer comprises a groove, and the medium layer and the polysilicon are located on the surface and in the groove of the epitaxial wafer. Then, the polysilicon on the surface of the epitaxial wafer is subjected to oxidation treatment, so that the polysilicon on the surface of the epitaxial wafer is converted into an oxide layer. Finally, the medium layer and the oxide layer are removed by using an etching solution, and the medium layer and the polysilicon in the groove are reserved. The polysilicon removal method and the diffusion furnace provided by the application have the advantages of fast removal rate, low cost, no damage to the polysilicon, and better uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular, to a polysilicon removal method and diffusion furnace. BACKGROUND

[0002] Polysilicon etching is an indispensable process step in semiconductor integrated circuit manufacturing, and is widely used in SGT (Split Gate Trench MOS) technology, for example.

[0003] The gate structure of an SGT device includes a shielding polysilicon and a polysilicon gate, both of which are formed in a trench after etching.

[0004] At present, conventional polysilicon etching is mostly performed by dry etching, wet etching, or a combination of dry and wet etching. Dry etching uses CL2, HBr, CF4, SF6, and O2 gases for the process, and the pressure, temperature, bias, speed, and other parameters during the process need to be controlled. Wet etching uses a mixed solution of HNO3:CH3COOH:HF with a ratio of 320:20:1.

[0005] However, the prior art has the problems of high cost of dry etching and poor isotropic uniformity of wet etching. SUMMARY

[0006] The present application aims to provide a polysilicon removal method and diffusion furnace to solve the problems of high cost of dry etching and poor isotropic uniformity of wet etching in the prior art.

[0007] To achieve the above-mentioned purpose, the technical solutions adopted by the embodiments of the present application are as follows:

[0008] On the one hand, the embodiments of the present application provide a polysilicon removal method, which comprises:

[0009] Based on an epitaxial wafer, a surface growth medium layer and polysilicon, wherein the epitaxial wafer includes a trench, and the medium layer and the polysilicon are located on the surface of the epitaxial wafer and in the trench;

[0010] Oxidizing the polysilicon located on the surface of the epitaxial wafer to convert the polysilicon located on the surface of the epitaxial wafer into an oxide layer;

[0011] Using an etching solution to remove the medium layer and the oxide layer, and retaining the medium layer and the polysilicon located in the trench.

[0012] Optionally, the step of oxidizing the polysilicon located on the surface of the epitaxial wafer comprises:

[0013] The epitaxial wafer with the growth medium layer and the polysilicon is placed in a diffusion furnace and heated;

[0014] The pressure in the diffusion furnace is controlled to increase, and then the oxidizing agent is introduced and maintained for a preset time, so that the polysilicon on the surface of the epitaxial wafer is converted into an oxide layer;

[0015] The pressure in the diffusion furnace is reduced.

[0016] Optionally, the step of placing the epitaxial wafer with the growth medium layer and the polysilicon in a diffusion furnace and heating includes:

[0017] The filling gas is introduced at a flow rate of 10-15 SLM, and the epitaxial wafer with the growth medium layer and the polysilicon is placed in a diffusion furnace at a temperature of 600-700°C;

[0018] The temperature in the diffusion furnace is increased at a rate of 5-10°C / min to 700-900°C.

[0019] Optionally, the step of controlling the pressure in the diffusion furnace to increase and then introducing the oxidizing agent and maintaining for a preset time includes:

[0020] The filling gas is introduced at a flow rate of 15-30 SLM until the pressure in the diffusion furnace increases to 5 atm;

[0021] The flow rate of the filling gas is increased so that the pressure in the diffusion furnace reaches 6-10 atm;

[0022] The flow rate of the filling gas is reduced, and the oxidizing agent is introduced, wherein the flow rate of the introduced oxidizing agent is equal to the reduced flow rate of the filling gas.

[0023] Optionally, before the step of reducing the pressure in the diffusion furnace, the method further includes:

[0024] The introduction of the oxidizing agent is stopped, and the flow rate of the filling gas is increased, wherein the amount of increase in the flow rate of the filling gas is equal to the amount of decrease in the oxidizing agent.

[0025] Optionally, the step of reducing the pressure in the diffusion furnace includes:

[0026] The step of reducing the flow rate of the filling gas in the diffusion furnace and stabilizing for 5-10 min is repeated until the pressure in the diffusion furnace decreases to 1 atm;

[0027] The temperature in the diffusion furnace is reduced at a rate of 2-3°C / min to 700-800°C.

[0028] Optionally, the step of removing the growth medium layer and the oxide layer using an etching solution includes:

[0029] The growth medium layer and the oxide layer are removed using a buffered oxide etching solution composed of hydrofluoric acid and ammonium fluoride.

[0030] Optionally, the medium layer comprises an oxide layer or a nitride layer, and the step of growing the medium layer and the polysilicon based on the surface of the epitaxial wafer comprises:

[0031] growing the oxide layer or the nitride layer based on the surface of the epitaxial wafer;

[0032] growing the polysilicon based on the surface of the oxide layer or the nitride layer.

[0033] In another aspect, the embodiments of the present application also provide a diffusion furnace for performing the oxidation process in the polysilicon removal method, the diffusion furnace comprising a furnace cavity and a protective sleeve, the protective sleeve being sleeved outside the furnace cavity and connected with the diffusion furnace.

[0034] Optionally, the protective sleeve comprises a stainless steel sleeve.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] The present application provides a polysilicon removal method and a diffusion furnace. First, a medium layer and a polysilicon are grown based on the surface of an epitaxial wafer, wherein the epitaxial wafer comprises a groove, the medium layer and the polysilicon are located on the surface and in the groove of the epitaxial wafer, then the polysilicon on the surface of the epitaxial wafer is subjected to an oxidation treatment so as to be converted into an oxide layer, and finally the medium layer and the oxide layer are removed by using an etching liquid, and the medium layer and the polysilicon in the groove are reserved. Since the polysilicon on the surface of the epitaxial wafer is oxidized and converted into an oxide layer before being etched, and then the oxide layer of the epitaxial wafer is removed by using an etching liquid, the polysilicon on the surface of the epitaxial wafer is quickly and efficiently removed, and the polysilicon in the groove is reserved, thereby reducing the cost. At the same time, no plasma is generated in the high-pressure oxidation polysilicon process, so that the polysilicon is not damaged, and the density and uniformity of the oxide layer are good.

[0037] In order to make the above objectives, characteristics and advantages of the present application more apparent and understandable, the following preferred embodiments are described in detail below, and the accompanying drawings are referred to, and the detailed description is as follows. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0039] Figure 1 The cross-sectional view of the prior art before etching of the polysilicon.

[0040] Figure 2 A cross-sectional view of a polysilicon etching process in the prior art.

[0041] Figure 3 An exemplary flow chart of a polysilicon removal method provided by an embodiment of the present application.

[0042] Figure 4 A first cross-sectional view of a polysilicon oxidation process provided by an embodiment of the present application.

[0043] Figure 5 A second cross-sectional view of a polysilicon oxidation process provided by an embodiment of the present application.

[0044] Figure 6 An exemplary flow chart of a sub-step of S104 provided by an embodiment of the present application.

[0045] Figure 7 A structural schematic diagram of a diffusion furnace provided by an embodiment of the present application. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work, fall within the scope of protection of the present application.

[0048] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0049] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0050] Some embodiments of the present application will be described in detail with reference to the drawings. The following examples and features in the examples can be combined with each other in the case of no conflict.

[0051] As described in the background, the prior art generally uses dry etching, wet etching or dry-wet mixed etching process when etching polysilicon. However, dry etching is high in cost, and wet etching is poor in isotropic uniformity.

[0052] Taking the manufacture of an SGT device as an example, refer to Figure 1 The common process of the SGT device is to grow an epitaxial layer on a substrate to form an epitaxial wafer, etch trenches (for example, two trenches are shown in the figure, but the number of trenches is not limited in actual application, for example, it can be five or ten) on the epitaxial wafer, and grow a dielectric layer based on the surface of the epitaxial wafer, wherein the dielectric layer is grown on the surface of the epitaxial wafer and the inner wall of the trench. Then, the polysilicon is deposited based on the surface of the dielectric layer, at this time, the polysilicon is located on the surface of the epitaxial wafer and in the trench. It should be noted that the polysilicon described in the present application refers to polysilicon, which will not be described below.

[0053] In subsequent processes, the polysilicon on the surface of the epitaxial wafer needs to be removed and the polysilicon in the trench is retained. The structure after the polysilicon on the surface of the epitaxial wafer is removed is shown in Figure 2 In the prior art, the polysilicon on the surface of the epitaxial wafer is generally removed by dry and / or wet process.

[0054] However, in order to ensure that the polysilicon fills the trench, the thickness of the polysilicon is generally thick, and the thickness is generally ≥8000A. Therefore, when dry etching is used, there are problems of high material consumption, long single wafer process time, high cost, and easy to cause plasma damage. The HNO3:CH3COOH:HF liquid medicine is mixed at a ratio of 320:20:1, but the wafer surface uniformity after etching process is poor, and isotropic, and the trench side etching is difficult to control.

[0055] Therefore, the present application provides a polysilicon removal method, which can quickly remove the polysilicon on the surface of the epitaxial wafer by oxidizing the polysilicon on the surface of the epitaxial wafer and then removing it by etching liquid, and the removal effect is better.

[0056] The polysilicon removal method provided by the present application will be described below:

[0057] As an optional implementation, refer to Figure 3 The polysilicon removal method comprises:

[0058] S102, growing a dielectric layer and polysilicon based on the surface of the epitaxial wafer, wherein the epitaxial wafer comprises a trench, and the dielectric layer and the polysilicon are located on the surface of the epitaxial wafer and in the trench.

[0059] S104, the polycrystalline silicon on the surface of the epitaxial wafer is subjected to oxidation treatment to convert the polycrystalline silicon on the surface of the epitaxial wafer into an oxide layer.

[0060] S106, the medium layer and the oxide layer are removed by using an etching solution, and the medium layer and the polycrystalline silicon in the trench are retained.

[0061] For example, taking the manufacture of an SGT device as an example, please refer to Figure 1 After etching the trench on the epitaxial wafer, the medium layer and the polycrystalline silicon can be grown based on the surface of the epitaxial wafer. At this time, the medium layer and the polycrystalline silicon are located on the surface and in the trench of the epitaxial wafer. The medium layer can be a SiO2 layer, and of course other materials such as a nitride layer can also be used, which is not limited here.

[0062] In this application, the polycrystalline silicon on the surface of the epitaxial wafer is not directly removed by dry and / or wet method, but the polycrystalline silicon is first subjected to oxidation treatment, and then the oxide layer is removed by using an etching solution.

[0063] In this application, the polycrystalline silicon is subjected to oxidation treatment by using a high-temperature diffusion furnace tube under the conditions of high temperature, high pressure and oxidizing agent to convert the polycrystalline silicon on the surface of the epitaxial wafer into a SiO2 layer (SiO2 is easily removed by BOE solution), and then the SiO2 layer is removed by using BOE. By using the high-pressure oxidation polycrystalline silicon method, the polycrystalline silicon can be quickly and efficiently removed, and the polycrystalline silicon in the trench is retained. In the process of high-pressure oxidation of polycrystalline silicon, there is no plasma, so the polycrystalline silicon will not be damaged, and the density and uniformity of the oxide layer are good. In addition, the high-pressure oxidation polycrystalline silicon process greatly reduces the oxidation temperature, inhibits the generation of layer faults, reduces the pinholes of the oxide film, reduces the warping of the silicon wafer, reduces the displacement of the previous diffusion junction, and prevents impurity back diffusion.

[0064] Please refer to Figure 4 It should be noted that in this application, when the medium layer is a SiO2 layer, the oxide layer converted by the oxidation treatment of the polycrystalline silicon is also a SiO2 layer. At this time, the materials of the medium layer and the oxide layer are both SiO2, as described in Figure 4 At this time, the medium layer is also part of the oxide layer, and the oxide layer on the epitaxial wafer is removed by using an etching solution, and the polycrystalline silicon in the trench is retained after removal.

[0065] Of course, if the material of the medium layer is not SiO2, for example, the material of the medium layer is nitride, please refer to Figure 5 The surface of the epitaxial wafer includes the medium layer and the oxide layer on the medium layer, and the material of the oxide layer is SiO2. At the same time, the etching solution can also achieve the effect of removing the oxide layer and the medium layer on the surface of the epitaxial wafer.

[0066] On this basis, the steps of S102 include:

[0067] S1021, growing an oxide layer or a nitride layer on the surface of the epitaxial wafer.

[0068] S1022, growing polysilicon on the surface of the oxide layer or the nitride layer.

[0069] As an optional implementation, please refer to Figure 6 , S104 includes:

[0070] S1041, placing the epitaxial wafer after growing the medium layer and the polysilicon in a diffusion furnace and heating.

[0071] S1042, after increasing the pressure in the diffusion furnace, introducing an oxidizing agent and maintaining for a preset time, so that the polysilicon on the surface of the epitaxial wafer is converted into an oxide layer.

[0072] S1043, reducing the pressure and temperature of the diffusion furnace.

[0073] Optionally, the application adopts an oxidation treatment on the polysilicon under high temperature and high pressure. First, the epitaxial wafer after growing the medium layer and the polysilicon is placed in a diffusion furnace and heated, then the pressure is increased, and an oxidizing agent is introduced. Under high temperature and high pressure, the polysilicon on the surface of the epitaxial wafer is completely oxidized, and the polysilicon in the trench is not oxidized. Then, after reducing the pressure and temperature of the diffusion furnace, the epitaxial wafer in the furnace is taken out, and finally the medium layer and the oxide layer are removed by using an etching liquid, and the polysilicon removal process on the surface of the epitaxial wafer is completed.

[0074] As an implementation, S1041 includes:

[0075] S1041-1, introducing a filling gas at a flow rate of 10-15 SLM, and placing the epitaxial wafer after growing the medium layer and the polysilicon in a diffusion furnace at a temperature of 600-700℃.

[0076] S1041-2, increasing the temperature in the diffusion furnace to 700-900℃ at a rate of 5-10℃ / min.

[0077] Wherein, SLM is a flow unit, which represents standard liters per minute (0℃, 1atm) to prevent the time from 0℃ to 700-900℃ from being too long, which will keep the diffusion furnace at a certain temperature. Generally, the temperature is 600-700℃, so that when the epitaxial wafer is placed in the diffusion furnace, the time required for heating is shortened.

[0078] In addition, when the epitaxial wafer is placed in the diffusion furnace, the filling gas can be introduced at a small flow rate to gradually increase the pressure in the furnace. It should be noted that the present application does not limit the type of filling gas, as long as it does not react with the polysilicon and does not affect the polysilicon oxidation process. For example, the filling gas can be nitrogen or an inert gas such as helium or argon.

[0079] After the epitaxial wafer is placed in the high-temperature diffusion furnace, the temperature in the furnace can be increased to 700-900°C, with a heating rate of 5-10°C / min and a stabilization period. It should be noted that in order to ensure the stability of the polysilicon oxidation at high temperature and high pressure, the furnace door position can be detected at this time to ensure that the furnace door is tightly closed to prevent accidents in subsequent processes.

[0080] As an implementation manner, S1042 includes:

[0081] S1042-1, the filling gas is introduced at a flow rate of 15-30 SLM until the pressure in the diffusion furnace increases to 5 atm.

[0082] S1042-2, the flow rate of the filling gas is increased to make the pressure in the diffusion furnace reach 6-10 atm.

[0083] S1042-3, the flow rate of the filling gas is reduced, and an oxidizing agent is introduced, wherein the flow rate of the introduced oxidizing agent is equal to the reduced flow rate of the filling gas.

[0084] After the temperature reaches the reaction temperature, the furnace needs to be pressurized. It should be noted that in order to prevent the diffusion furnace from exploding, the furnace needs to be pressurized slowly to ensure stable transition of the furnace pressure. On this basis, the present application uses a small flow rate to add filling gas to the furnace at the initial stage of pressurization, for example, the filling gas is introduced at a flow rate of 15-30 SLM until the pressure in the diffusion furnace increases to 5 atm. Of course, the 5 atm mentioned in the present application can have some errors, for example, within the range of 4.9-5.1 atm, the pressure in the diffusion furnace is considered to reach 5 atm.

[0085] When the pressure in the diffusion furnace reaches 5 atm, the flow rate of the filling gas needs to be increased correspondingly as the pressure in the furnace increases to continuously input the filling gas into the furnace until the pressure in the diffusion furnace reaches 6-10 atm, reaching the high-temperature and high-pressure environment for polysilicon oxidation. At this time, the valve is closed, and the airtightness of the diffusion furnace is detected to see if it meets the requirements.

[0086] When the pressure reaches the process requirement, the pressure, gas, and temperature also need to be detected and stabilized to ensure the stability of the polysilicon oxidation process. If the pressure, gas, and temperature are stable, the oxidizing agent can be introduced to realize the polysilicon oxidation process.

[0087] Wherein, in order to ensure the stability of the furnace pressure, the flow of the filling gas needs to be reduced at this time, and the oxidant is introduced at the same time, wherein the flow of the introduced oxidant is equal to the reduced flow of the filling gas, and a dynamic balance process is formed, the furnace pressure will not change too much, and the oxidation process of the polysilicon is more stable.

[0088] Of course, in order to stabilize the oxidation of the polysilicon, the pressure, gas, and temperature can also be detected at this time, and real-time adjustment is made to stabilize the environment in the furnace, for example, when the gas pressure in the furnace is low, the flow of the introduced filling gas can be increased, and the environment in the furnace is always in a dynamic balance.

[0089] At this time, in order to generate a SiO2 layer with a target thickness (i.e. the thickness of the polysilicon on the surface of the epitaxial wafer) on the surface of the epitaxial wafer, the duration of maintaining the above high-temperature and high-pressure environment needs to be >0.5h to ensure that the polysilicon on the surface of the epitaxial wafer is completely converted into SiO2. Alternatively, the thickness of the SiO2 layer is 1um-3um;

[0090] It should be noted that the oxidant is used to provide oxygen elements to ensure that the polysilicon is oxidized. The type of oxidant is not limited in the present application, for example, the oxidant can be water vapor, or dry oxygen, etc.

[0091] When the oxidant is water vapor, a water vapor device is also included in the process equipment, for example, the water vapor device can be a thickened quartz tube, the thickened quartz tube contains water, and the water vapor can be heated by a bulb. The inlet of the diffusion furnace includes two, one of which is used for filling gas input, and the other is used for connecting the water vapor device to input water vapor.

[0092] And, under high temperature and high pressure, a replacement reaction is actually carried out in the diffusion furnace, i.e. Si+oxidant (H2O)→SiO2+H2, so that the polysilicon is converted into SiO2.

[0093] When the oxidant is dry oxygen, only 1-10 SLM oxygen can be introduced, the oxygen is in a compressed state in the source bottle, the pipeline pressure is much >10atm, and the oxygen can be directly introduced into the furnace tube.

[0094] Alternatively, the oxidant adopts dry oxygen+chlorine-doped oxidation, 5-12 SLM oxygen is introduced, the chlorine source can be DCE or HCL, and the chlorine source gas ratio is controlled to be <3%. Alternatively, the oxidant adopts wet oxygen, and the hydrogen-oxygen gas ratio is <1.8. Of course, the oxidant can also adopt wet oxygen+chlorine-doped oxidation, the chlorine source can be DCE or HCL, and the chlorine source gas ratio is controlled to be <3%.

[0095] After the polysilicon is oxidized, the epitaxial wafer needs to be taken out and etched with an etching liquid. Alternatively, before the step of S1043, the method further comprises:

[0096] Stop the input of oxidant, and increase the flow rate of the filling gas, wherein the increase in the flow rate of the filling gas is equal to the decrease in the oxidant.

[0097] In order to ensure the stability of the pressure in the furnace, when the input of the oxidant is stopped after the oxidation is completed, the flow rate of the filling gas can also be increased, wherein the increase in the flow rate of the filling gas is equal to the decrease in the oxidant, so that a dynamic balance is reached, and the stability of the pressure and temperature in the furnace is ensured. The process can be maintained for 5-10 minutes.

[0098] After the input of the oxidant is stopped, the diffusion furnace needs to be depressurized and cooled to take out the entire wafer (i.e., the epitaxial wafer with SiO2). S1043 includes:

[0099] S1043-2, repeatedly performing the steps of reducing the flow rate of the filling gas in the diffusion furnace and stabilizing for 5-10 minutes until the pressure in the diffusion furnace is reduced to 1 atm. S1043-1, reducing the temperature in the diffusion furnace to 700-800°C at a rate of 2-3°C / min.

[0100] In order to avoid the problem of wafer warping caused by rapid cooling of the epitaxial wafer under high pressure, the present application adopts the method of first reducing the pressure and then reducing the temperature during the process of reducing the temperature and pressure, thereby ensuring that the epitaxial wafer does not warp during the process of reducing the temperature. The present application reduces the temperature at a rate of 2-3°C / min to reduce the temperature in the diffusion furnace to 700-800°C.

[0101] After the temperature is reduced, the furnace door can be opened, and the oxidized epitaxial wafer can be taken out. It can be understood that although the epitaxial wafer is described in the above description, it can be understood that the epitaxial wafer is grown based on the wafer substrate, so the wafer taken out from the furnace is actually the wafer after the oxidation process.

[0102] After the wafer is taken out, the thickness of the SiO2 layer can be tested, and then the oxide layer on the surface of the epitaxial wafer can be etched.

[0103] As an implementation manner, S106 includes:

[0104] The buffer oxide etching solution composed of hydrofluoric acid and ammonium fluoride is used to remove the dielectric layer and the oxide layer.

[0105] The buffer oxide etching solution can be a solution of 40% NH4F and 49% HF mixed by volume ratio, wherein HF is used as an etchant to remove all the oxidized polysilicon by the chemical reaction of SiO2+HF→H2+SiF+H2O, and the unoxidized polysilicon is reserved, and NH4F is used as a buffer. Of course, the buffer oxide etching solution can also be replaced by other etching solutions, for example, a solution of 49% HF, which is not limited herein.

[0106] Based on the above implementation mode, the application further provides a diffusion furnace for performing the oxidation process in the polysilicon removal method. Since the reaction environment in the above oxidation process is as high as 6-10 atm, the diffusion furnace needs to bear a larger pressure.

[0107] Therefore, as an implementation mode, referring to Figure 7 The diffusion furnace includes a furnace cavity and a protective sleeve, the protective sleeve is sleeved outside the furnace cavity, and the protective sleeve is connected with the diffusion furnace. Of course, inlets 1 and 2 are arranged for inputting the filling gas and the oxidant, and an outlet is further arranged to realize pressure reduction and temperature reduction. Of course, the wafer can be placed in the furnace cavity and oxidized with silicon nitride at high temperature and high pressure.

[0108] As an implementation mode, the protective sleeve can be a stainless steel sleeve, the furnace cavity can be a quartz process cavity, the filling gas enters the furnace tube from the inlet 1 to make the pressure in the quartz process cavity reach the process high pressure, the quartz process cavity is sleeved with a stainless steel outer sleeve for protection to prevent the pressure in the cavity from being too high and the quartz process cavity from exploding.

[0109] In summary, the application provides a polysilicon removal method and a diffusion furnace. First, a surface medium layer and polysilicon are grown based on an epitaxial wafer, wherein the epitaxial wafer includes a groove, and the medium layer and the polysilicon are located on the surface and in the groove of the epitaxial wafer. Then, the polysilicon on the surface of the epitaxial wafer is subjected to oxidation treatment to convert the polysilicon on the surface of the epitaxial wafer into an oxide layer. Finally, the medium layer and the oxide layer are removed by using an etching solution, and the medium layer and the polysilicon in the groove are reserved. Since the polysilicon on the surface of the epitaxial wafer is oxidized first to convert it into an oxide layer, and then the oxide layer of the epitaxial wafer is removed by using an etching solution, the polysilicon on the surface of the epitaxial wafer is quickly and efficiently removed, and the polysilicon in the groove is reserved, thereby reducing the cost. At the same time, there is no plasma in the high-pressure polysilicon oxidation process, which will not damage the polysilicon, and the density and uniformity of the oxide layer are good.

[0110] The above only describes the preferred embodiments of the application and is not used to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

[0111] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference herein to any prior art is to be taken as an admission that the application is not entitled to antedate such prior art by virtue of prior application. No reference to any prior art in this specification is intended to be, nor should it be taken as, an acknowledgement or any form of suggestion that such prior art is accepted as relevant prior art against the present application. Any citation of any prior art in this specification is solely provided on the basis of relevance to the disclosure of the application.

Claims

1. A method for removing polycrystalline silicon, characterized in that, The polysilicon removal method includes: A dielectric layer and polysilicon are grown on the surface of an epitaxial wafer, wherein the epitaxial wafer includes trenches, and the dielectric layer and the polysilicon are located on the surface of the epitaxial wafer and within the trenches; The polysilicon located on the surface of the epitaxial wafer is subjected to an oxidation treatment to transform the polysilicon located on the surface of the epitaxial wafer into an oxide layer; The dielectric layer and oxide layer are removed using an etching solution, while the dielectric layer and polysilicon located in the trench are retained; The step of oxidizing the polycrystalline silicon on the surface of the epitaxial wafer includes: introducing a filling gas at a flow rate of 10 to 15 SLM, and placing the epitaxial wafer after growing the dielectric layer and polycrystalline silicon in a diffusion furnace at 600 to 700°C. The temperature inside the diffusion furnace is increased to 700-900℃ at a rate of 5-10℃ / min; The filling gas is introduced at a flow rate of 15-30 SLM until the pressure inside the diffusion furnace increases to 5 atm; Increase the flow rate of the filling gas so that the pressure inside the diffusion furnace reaches 6-10 atm; The flow rate of the filling gas is reduced, and an oxidant is introduced, wherein the flow rate of the introduced oxidant is equal to the reduced flow rate of the filling gas, and this is maintained for a preset time, so that the polycrystalline silicon located on the surface of the epitaxial wafer is transformed into an oxide layer. After polysilicon oxidation, the oxidant is stopped and the flow rate of the filling gas is increased, wherein the increase in the flow rate of the filling gas is equal to the decrease in the oxidant. The pressure and temperature of the diffusion furnace are reduced.

2. The polycrystalline silicon removal method as described in claim 1, characterized in that, The steps of depressurizing and cooling the diffusion furnace include: Repeat the steps of reducing the flow rate of the filling gas in the diffusion furnace and stabilizing it for 5 to 10 minutes until the pressure in the diffusion furnace drops to 1 atm; The temperature inside the diffusion furnace is reduced to 700-800℃ at a rate of 2-3℃ / min.

3. The polycrystalline silicon removal method as described in claim 1, characterized in that, The steps for removing the dielectric layer and oxide layer using an etchant include: The dielectric layer and oxide layer are removed using a buffer oxide etching solution composed of hydrofluoric acid and ammonium fluoride.

4. The polycrystalline silicon removal method as described in claim 1, characterized in that, The dielectric layer includes an oxide layer or a nitride layer, and the step of growing the dielectric layer and polysilicon based on the epitaxial wafer includes: An oxide layer or a nitride layer is grown on the surface of the epitaxial wafer; Polycrystalline silicon is grown on the surface of the oxide layer or nitride layer.

5. A diffusion furnace, characterized in that, The diffusion furnace is used to perform the oxidation process in the polysilicon removal method as described in any one of claims 1 to 4. The diffusion furnace includes a furnace cavity and a protective sleeve, the protective sleeve being fitted outside the furnace cavity and connected to the diffusion furnace.

6. The diffusion furnace as described in claim 5, characterized in that, The protective sleeve includes a stainless steel sleeve.

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