Method for stripping epitaxial layer

Abstract

The invention relates to a method for stripping an epitaxial layer. The method for stripping the epitaxial layer comprises the following steps: providing a sample to be stripped; wherein the to-be-stripped sample comprises a substrate and an epitaxial layer which are stacked in the thickness direction; the conduction types of the substrate and the epitaxial layer are opposite; soaking a to-be-stripped sample in the etching liquid, wherein the to-be-stripped sample is used as a working electrode; irradiating the to-be-stripped sample by adopting a light source with a preset wavelength, so that the to-be-stripped sample generates a hole-electron pair; and in the irradiation process, a preset constant forward potential is provided for the to-be-stripped sample. According to the invention, the repeated utilization rate of the monitoring chip can be effectively improved, so that the production cost of the chip is reduced.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for stripping an epitaxial layer. Background Art

[0002] The epitaxial process is an indispensable process in semiconductor chip manufacturing. In order to ensure the stability of chip quality, a large number of monitoring chips are usually consumed during process debugging and production.

[0003] However, the monitoring film cannot be reused after the epitaxial process. At present, the monitoring film can only be processed by thinning process and chemical mechanical polishing process, which is very expensive and consumes a lot of the original thickness of the monitoring film, resulting in a low reuse rate of the monitoring film.

[0004] Therefore, how to improve the reuse rate of monitoring chips and thus reduce the production cost of chips is an urgent problem to be solved. Summary of the invention

[0005] Based on this, an embodiment of the present application provides a method for stripping an epitaxial layer, which can effectively improve the reuse rate of the monitoring chip, thereby reducing the production cost of the chip.

[0006] According to some embodiments, the present application provides a method for stripping an epitaxial layer, comprising the following steps:

[0007] Providing a sample to be stripped; wherein the sample to be stripped comprises a substrate and an epitaxial layer stacked in a thickness direction; the substrate and the epitaxial layer have opposite conductivity types;

[0008] Immersing the sample to be stripped in an etching solution; wherein the sample to be stripped serves as a working electrode;

[0009] A light source with a preset wavelength is used to irradiate the sample to be stripped, so that hole-electron pairs are generated in the sample to be stripped;

[0010] During the irradiation process, a preset constant forward potential is provided to the sample to be peeled off.

[0011] According to some embodiments, a reference electrode and a counter electrode are provided in the etching solution. The reference electrode includes: a mercury / mercury oxide electrode. The counter electrode includes: a graphite electrode.

[0012] According to some embodiments, the etching solution includes an oxidant and a silicon oxide etching solution.

[0013] According to some embodiments, providing a preset constant forward potential to the sample to be stripped includes: providing a preset constant forward potential to the sample to be stripped, so that the electrons in the depletion region are transferred along the current to the counter electrode to react with the oxidant, and the silicon oxide etching solution selectively etches the depletion region with holes to achieve stripping of the epitaxial layer.

[0014] The depletion region is located in the contact area between the substrate and the epitaxial layer.

[0015] According to some embodiments, the range of the preset wavelength includes: 180nm ~ 380nm.

[0016] According to some embodiments, the etching solution further comprises: anhydrous ethanol. The oxidant comprises: a hydrogen peroxide solution. The silicon oxide etching solution comprises: a hydrofluoric acid solution.

[0017] The mass fraction of the hydrogen peroxide solution ranges from 3% to 30%. The mass ratio of the hydrofluoric acid solution to the anhydrous ethanol ranges from 1:0.5 to 1:2.

[0018] According to some embodiments, the thickness of the sample to be peeled off ranges from 2 inches to 12 inches. The size of the epitaxial layer ranges from 10 μm to 100 μm.

[0019] According to some embodiments, relative to the reference electrode, the preset constant forward potential range includes: 1 volt to 15 volts.

[0020] According to some embodiments, the shortest distance between the light source and the etching liquid surface ranges from 5 cm to 15 cm.

[0021] According to some embodiments, the flow rate range of the etching solution includes: 1 mL / min to 5 mL / min.

[0022] The embodiments of the present application may or at least have the following advantages:

[0023] In the embodiment of the present application, the sample to be stripped includes a substrate and an epitaxial layer of opposite conductivity types, and the sample to be stripped is immersed in an etching solution containing an oxidant and a silicon oxide etching solution, and a three-electrode system is adopted, the sample to be stripped is used as a working electrode, and a reference electrode and a counter electrode are set in the etching solution. In this way, under the irradiation of a light source of a preset wavelength, the sample to be stripped generates a hole-electron pair, and then by providing a preset constant forward potential to the sample to be stripped, the electrons in the depletion region are transferred along the current to the counter electrode to react with the oxidant, and the silicon oxide etching solution selectively etches the depletion region with holes. That is, the embodiment of the present application utilizes the principle of selective etching of semiconductor conductivity types by photoelectrochemical corrosion to realize the stripping of the epitaxial layer from the substrate, and will not cause damage to the substrate surface, and the stripped substrate can be directly subjected to epitaxial growth. In this way, the embodiment of the present application improves the reuse rate of the substrate (i.e., the monitoring sheet used for the epitaxial process), simplifies the process flow, and thus reduces the production cost of the chip.

[0024] In addition, anhydrous ethanol can reduce the surface tension of the etching solution, which is beneficial for the etching solution to penetrate into the sample to be peeled off. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A schematic flow chart of a method for stripping an epitaxial layer provided in some embodiments;

[0027] Figure 2 A schematic cross-sectional view of a structure obtained when a depletion region is selectively etched in a method for stripping an epitaxial layer provided in some embodiments;

[0028] Figure 3 It is a schematic cross-sectional structure diagram of another structure obtained when the depletion region is selectively etched in a method for stripping an epitaxial layer provided in some embodiments.

[0029] Description of reference numerals:

[0030] 1-substrate; 10-depletion region; 11-epitaxial layer; 2-insulating layer; h-hole; e-electron. DETAILED DESCRIPTION

[0031] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0033] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers.

[0034] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0035] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, in this specification, the term "and / or" includes any and all combinations of the relevant listed items.

[0036] As used herein, a "deposition" process includes, but is not limited to, physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic layer deposition (ALD).

[0037] Embodiments of the invention are described herein with reference to cross-sectional views that are schematic representations of ideal embodiments (and intermediate structures) of the present application, such that variations in the shapes shown due to, for example, manufacturing techniques and / or tolerances are anticipated. Thus, embodiments of the present application should not be limited to the specific shapes of the regions shown herein, but include deviations in shapes due to, for example, manufacturing techniques. The regions shown in the figures are schematic in nature, and their shapes do not represent the actual shapes of the regions of the device, and do not limit the scope of the present application.

[0038] The epitaxial process is an indispensable process in semiconductor chip manufacturing. In order to ensure the stability of chip quality, a large number of monitoring chips are usually consumed during process debugging and production.

[0039] However, the monitoring chip cannot be reused after the epitaxial process. At present, the monitoring chip can only be processed by thinning process and chemical mechanical polishing process, which is very expensive. In addition, the above process consumes a lot of the original thickness of the monitoring chip, resulting in a low reuse rate of the monitoring chip. Therefore, how to improve the reuse rate of the monitoring chip and thus reduce the production cost of the chip is an urgent problem to be solved.

[0040] Based on this, an embodiment of the present application provides a method for stripping an epitaxial layer, which can effectively improve the reuse rate of the monitoring chip, thereby reducing the production cost of the chip.

[0041] See also Figure 1 Some embodiments of the present application provide a method for stripping an epitaxial layer, including steps S100 to S500.

[0042] S100, providing a sample to be stripped, wherein the sample to be stripped includes a substrate and an epitaxial layer stacked in a thickness direction; the substrate and the epitaxial layer have opposite conductivity types.

[0043] S200, immersing the sample to be stripped in an etching solution, wherein the sample to be stripped is used as a working electrode.

[0044] S300, using a light source of a preset wavelength to irradiate the sample to be stripped, so that the sample to be stripped generates hole-electron pairs.

[0045] S400, during the irradiation process, providing a preset constant forward potential to the sample to be peeled off.

[0046] In some embodiments, a reference electrode and a counter electrode are provided in the etching solution. The reference electrode includes: a mercury / mercury oxide electrode. The counter electrode includes: a graphite electrode.

[0047] In some embodiments, the etching solution includes an oxidant and a silicon oxide etching solution.

[0048] In some embodiments, providing a preset constant forward potential to the sample to be stripped includes: providing a preset constant forward potential to the sample to be stripped, so that electrons in the depletion region are transferred along the current to the counter electrode to react with the oxidant, and the silicon oxide etching solution selectively etches the depletion region with holes to achieve stripping of the epitaxial layer.

[0049] The depletion region is located in the contact area between the substrate and the epitaxial layer.

[0050] In some embodiments, the preset wavelength range includes: 180nm to 380nm. For example, the preset wavelength can be 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm or 380nm, etc.

[0051] In step S300, using a light source of a preset wavelength to irradiate the sample to be stripped includes: using a 400W xenon lamp as the light source under room temperature conditions, and using an ultraviolet reflecting lens or filter so that the wavelength of the light irradiating the sample to be stripped meets the preset wavelength.

[0052] In some embodiments, the etching solution further comprises: anhydrous ethanol. The oxidant comprises: a hydrogen peroxide solution. The silicon oxide etching solution comprises: a hydrofluoric acid solution.

[0053] The mass fraction of the hydrogen peroxide solution ranges from 3% to 30%. For example, the mass fraction of the hydrogen peroxide solution can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27% or 30%, etc.

[0054] The mass ratio of the hydrofluoric acid solution to the anhydrous ethanol ranges from 1:0.5 to 1:2. For example, the mass ratio of the hydrofluoric acid solution to the anhydrous ethanol can be 1:0.5, 1:1, 1:1.5 or 1:2, etc.

[0055] In some embodiments, the thickness of the sample to be peeled includes: 2 inches to 12 inches. For example, the thickness of the sample to be peeled can be 2 inches, 4 inches, 6 inches, 8 inches, 10 inches or 12 inches, etc.

[0056] The thickness of the epitaxial layer ranges from 10 μm to 100 μm. For example, the thickness of the epitaxial layer can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm or 100 μm, etc.

[0057] In some embodiments, relative to the reference electrode, the preset constant forward potential range includes: 1 volt to 15 volts. For example, the preset constant forward potential can be: 1 volt, 3 volts, 5 volts, 7 volts, 9 volts, 11 volts, 13 volts or 15 volts, etc.

[0058] In some embodiments, the shortest distance between the light source and the etching liquid surface ranges from 5 cm to 15 cm. For example, the shortest distance between the light source and the etching liquid surface can be 5 cm, 7 cm, 9 cm, 11 cm, 13 cm or 15 cm.

[0059] In some embodiments, while providing a preset constant forward potential to the sample to be stripped, step S400 also includes: stirring the etching solution. For example, a stirrer may be used to stir the etching solution.

[0060] The speed range of the stirrer includes: 300r / min-500r / min. For example, the speed of the stirrer can be: 300r / min, 320r / min, 340r / min, 360r / min, 380r / min, 400r / min, 420r / min, 440r / min, 460r / min, 480r / min or 500r / min, etc.

[0061] The flow rate of the etching solution ranges from 1 mL / min to 5 mL / min. For example, the flow rate of the etching solution may be 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min or 5 mL / min.

[0062] In some embodiments, the substrate includes: a P-type substrate. The epitaxial layer includes: an N-type epitaxial layer.

[0063] In step S300, a light source of a preset wavelength is used to irradiate the sample to be stripped so that the sample to be stripped generates hole-electron pairs, including: a light source of a preset wavelength is used to vertically irradiate a P-type substrate, and the P-type substrate absorbs the light emitted by the light source and generates hole-electron pairs.

[0064] In step S400, providing a preset constant forward potential to the sample to be stripped includes: providing a preset constant forward potential to the N-type epitaxial layer.

[0065] Accordingly, in some embodiments, the silicon oxide etching solution selectively etches the depletion region having holes to achieve stripping of the epitaxial layer, including: the holes react with the silicon oxide etching solution on the side of the depletion region close to the P-type substrate to achieve stripping of the N-type epitaxial layer.

[0066] In some other embodiments, the substrate includes: an N-type substrate. The epitaxial layer includes: a P-type epitaxial layer.

[0067] In step S300, a light source with a preset wavelength is used to irradiate the sample to be stripped, so that the sample to be stripped generates hole-electron pairs, including: using a light source with a preset wavelength to vertically irradiate the P-type epitaxial layer, and the P-type epitaxial layer absorbs the light emitted by the light source and generates hole-electron pairs.

[0068] In step S400, providing a preset constant forward potential to the sample to be stripped includes: providing a preset constant forward potential to the N-type substrate.

[0069] Accordingly, in some embodiments, the silicon oxide etching solution selectively etches the depletion region having holes to achieve stripping of the epitaxial layer, including: the holes react with the silicon oxide etching solution on the side of the depletion region close to the P-type epitaxial layer to achieve stripping of the P-type epitaxial layer.

[0070] In the embodiment of the present application, the sample to be stripped includes a substrate and an epitaxial layer of opposite conductivity types, and the sample to be stripped is immersed in an etching solution containing an oxidant and a silicon oxide etching solution, and a three-electrode system is adopted, the sample to be stripped is used as a working electrode, and a reference electrode and a counter electrode are set in the etching solution. In this way, under the irradiation of a light source of a preset wavelength, the sample to be stripped generates a hole-electron pair, and then by providing a preset constant forward potential to the sample to be stripped, the electrons in the depletion region are transferred along the current to the counter electrode to react with the oxidant, and the silicon oxide etching solution selectively etches the depletion region with holes. That is, the embodiment of the present application utilizes the principle of selective etching of semiconductor conductivity types by photoelectrochemical corrosion to realize the stripping of the epitaxial layer from the substrate, and will not cause damage to the substrate surface, and the stripped substrate can be directly subjected to epitaxial growth. In this way, the embodiment of the present application improves the reuse rate of the substrate (i.e., the monitoring sheet used for the epitaxial process), simplifies the process flow, and thus reduces the production cost of the chip.

[0071] In order to more clearly illustrate the method for stripping the epitaxial layer provided in the above embodiment, Figure 2 and Figure 3 The preparation method is described in detail.

[0072] In some embodiments, the substrate 1 includes: a P-type substrate. The epitaxial layer 11 includes: an N-type epitaxial layer.

[0073] In step S100, refer to Figure 2 , providing a sample to be peeled off, wherein the sample to be peeled off comprises a P-type substrate 1 and an N-type epitaxial layer 11 stacked along a thickness direction (eg, a Y direction).

[0074] In some examples, the material of the P-type substrate 1 can be any suitable substrate material known in the art, for example, it can be at least one of the following materials: silicon (Si), germanium (Ge), red phosphorus, silicon germanium (SiGe), silicon carbide (SiC), carbon germanium silicon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or it can also be double-sided polished silicon wafers (Double Side Polished Wafers, referred to as DSP), or it can be a ceramic substrate such as alumina, a quartz or glass substrate, etc., and the embodiments of the present application are not limited here.

[0075] In some examples, the material of the N-type epitaxial layer 11 may include, but is not limited to, silicon carbide (SiC).

[0076] In some embodiments, the size of the sample to be peeled includes: 2 inches to 12 inches. For example, the size of the sample to be peeled can be 2 inches, 4 inches, 6 inches, 8 inches, 10 inches or 12 inches, etc.

[0077] The thickness of the N-type epitaxial layer 11 ranges from 10 μm to 100 μm. For example, the thickness of the epitaxial layer 11 may be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm or 100 μm, etc.

[0078] In step S200, please continue to refer to Figure 2 , immerse the sample to be stripped in an etching solution (not shown in the figure). The sample to be stripped serves as a working electrode (i.e., anode).

[0079] In some embodiments, the etching solution includes an oxidant and a silicon oxide etching solution.

[0080] In some embodiments, the oxidant includes: a hydrogen peroxide solution. The silicon oxide etching solution includes: a hydrofluoric acid solution.

[0081] The mass fraction of the hydrogen peroxide solution ranges from 3% to 30%. For example, the mass fraction of the hydrogen peroxide solution can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27% or 30%, etc.

[0082] In some embodiments, the etching solution further includes: anhydrous ethanol.

[0083] For example, the mass ratio of the hydrofluoric acid solution to the anhydrous ethanol ranges from 1:0.5 to 1:2. For example, the mass ratio of the hydrofluoric acid solution to the anhydrous ethanol can be 1:0.5, 1:1, 1:1.5 or 1:2, etc.

[0084] In the embodiment of the present application, anhydrous ethanol can reduce the surface tension of the etching solution, which is beneficial for the etching solution to penetrate into the sample to be peeled off.

[0085] In some embodiments, a three-electrode system is used, the sample to be stripped is used as the working electrode (ie, the anode), and a reference electrode and a counter electrode are placed in the etching solution.

[0086] In some embodiments, the reference electrode comprises: a mercury / mercury oxide electrode. The counter electrode comprises: a graphite electrode.

[0087] Here, it should be noted that the three-electrode system is an electronic device consisting of a working electrode, a reference electrode and a counter electrode. The working principle of the three-electrode system is based on the electrochemical reaction occurring at the electrode interface. In the three-electrode system, the working electrode is the main electrode used to trigger the electrochemical reaction; the reference electrode provides a stable potential reference for measuring the potential of the working electrode; the counter electrode is used to provide current to promote the electrochemical reaction. A major advantage of the three-electrode system is that it can achieve potential control and measurement accuracy. The reference electrode provides a stable and reproducible potential reference, and by connecting to the working electrode, it can provide an accurate potential measurement benchmark. In this way, by measuring the potential difference between the working electrode and the reference electrode, the electrochemical reaction can be accurately calculated and controlled. In addition, the presence of the counter electrode can provide additional current to promote the electrochemical reaction.

[0088] In some embodiments, an insulating layer 2 is further disposed on a side of the N-type epitaxial layer 11 away from the depletion region 10 .

[0089] In some examples, the material of the insulating layer 2 may include, but is not limited to, silicon oxide.

[0090] In step S300, please continue to refer to Figure 2 , a light source with a preset wavelength is used to vertically illuminate the P-type substrate, and the P-type substrate absorbs the light emitted by the light source and generates hole h-electron e pairs.

[0091] In some embodiments, the light source includes a xenon lamp, a mercury lamp, or an LED ultraviolet lamp.

[0092] In some embodiments, step S300 uses a light source of a preset wavelength to vertically irradiate the P-type substrate 1, and the P-type substrate 1 absorbs the light emitted by the light source and generates hole h-electron e pairs, including: under room temperature conditions, using a 400W xenon lamp as the light source, and using an ultraviolet reflecting lens or filter, so that the wavelength of the light irradiating the sample to be stripped meets the preset wavelength.

[0093] In some embodiments, the preset wavelength range includes: 180nm to 380nm. For example, the preset wavelength can be 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm or 380nm, etc.

[0094] In some embodiments, the shortest distance between the light source and the etching liquid surface ranges from 5 cm to 15 cm. For example, the shortest distance between the light source and the etching liquid surface can be 5 cm, 7 cm, 9 cm, 11 cm, 13 cm or 15 cm.

[0095] In step S400, please continue to refer to Figure 2During the irradiation process, a preset constant forward potential is provided to the N-type epitaxial layer 11, and the etching solution is stirred, so that the electrons e in the depletion region 10 are transferred to the counter electrode along the current to react with the oxidant, and the holes h react with the silicon oxide etching solution on the side of the depletion region 10 close to the P-type substrate 1 to achieve the stripping of the N-type epitaxial layer 11. Among them, the depletion region 10 is located in the contact area between the P-type substrate 1 and the N-type epitaxial layer 11.

[0096] In some embodiments, relative to the reference electrode, the preset constant forward potential range includes: 1 volt to 15 volts. For example, the preset constant forward potential can be: 1 volt, 3 volts, 5 volts, 7 volts, 9 volts, 11 volts, 13 volts or 15 volts, etc.

[0097] In some embodiments, while providing a preset constant forward potential to the sample to be stripped, step S400 also includes: stirring the etching solution. For example, a stirrer may be used to stir the etching solution.

[0098] The speed range of the stirrer includes: 300r / min-500r / min. For example, the speed of the stirrer can be: 300r / min, 320r / min, 340r / min, 360r / min, 380r / min, 400r / min, 420r / min, 440r / min, 460r / min, 480r / min or 500r / min, etc.

[0099] The flow rate of the etching solution ranges from 1 mL / min to 5 mL / min. For example, the flow rate of the etching solution may be 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min or 5 mL / min.

[0100] Here, it should be noted that in the three-electrode system, by adding an external potential to the working electrode, the ions in the etching solution will undergo a redox reaction under the action of the potential. The potential difference between the reference electrode and the working electrode is called the potential between the working electrode and the reference electrode, and the current caused by the potential difference between the reference electrode and the counter electrode is called the reference electrode current. In this system, the current generated by the working electrode is obtained by measuring the potential difference between the working electrode and the reference electrode.

[0101] In some examples, when a constant forward potential is provided to the N-type epitaxial layer 11, there is an internal electric field in the depletion region at the interface between the P-type substrate 1 and the N-type epitaxial layer 11, with the N-type pointing to the P-type (for example, in the Y direction), and there is an electric field in the solid-liquid interface between the P-type substrate 1 and the etching liquid, with the etching liquid pointing to the P-type silicon substrate (for example, in the X direction). The holes h in the depletion region move toward the P-type substrate 1, and the holes h inside the P-type substrate 1 also move to the depletion region 10. On the side of the depletion region 10 close to the P-type substrate, an oxidation reaction occurs: Si+H 2 O 2 +2H + →SiO 2 +2H + The electrons e in the depletion region 10 will move to the side of the N-type epitaxial layer 11 and transfer along the current to the counter electrode to undergo a reduction reaction: 2H + +H 2 O 2 +2e - -→2H 2 O. Among them, SiO 2 The chemical formula for the reaction with hydrofluoric acid solution is: SiO 2 +6HF→(SiF 6 ) 2- +2H 2 O+2H + .

[0102] In some other embodiments, the substrate 1 includes: an N-type substrate. The epitaxial layer 11 includes: a P-type epitaxial layer.

[0103] In step S100, refer to Figure 3 , providing a sample to be peeled off, wherein the sample to be peeled off comprises an N-type substrate 1 and a P-type epitaxial layer 11 stacked along a thickness direction (eg, a Y direction).

[0104] In some examples, the material of the N-type substrate 1 can be any suitable substrate material known in the art, for example, it can be at least one of the following materials: silicon (Si), germanium (Ge), red phosphorus, silicon germanium (SiGe), silicon carbide (SiC), carbon germanium silicon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or it can also be double-sided polished silicon wafers (Double Side Polished Wafers, referred to as DSP), or it can be a ceramic substrate such as alumina, a quartz or glass substrate, etc., and the embodiments of the present application are not limited here.

[0105] In some examples, the material of the P-type epitaxial layer 11 may include, but is not limited to, silicon carbide (SiC).

[0106] In some embodiments, the size of the sample to be peeled includes: 2 inches to 12 inches. For example, the size of the sample to be peeled can be 2 inches, 4 inches, 6 inches, 8 inches, 10 inches or 12 inches, etc.

[0107] The thickness of the P-type epitaxial layer 11 ranges from 10 μm to 100 μm. For example, the thickness of the epitaxial layer 11 may be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm or 100 μm, etc.

[0108] In step S200, please continue to refer to Figure 3 , immerse the sample to be stripped in an etching solution (not shown in the figure). The sample to be stripped serves as a working electrode (i.e., anode).

[0109] In some embodiments, the etching solution includes an oxidant and a silicon oxide etching solution.

[0110] In some embodiments, the oxidant includes: a hydrogen peroxide solution. The silicon oxide etching solution includes: a hydrofluoric acid solution.

[0111] The mass fraction of the hydrogen peroxide solution ranges from 3% to 30%. For example, the mass fraction of the hydrogen peroxide solution can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27% or 30%, etc.

[0112] In some embodiments, the etching solution further includes: anhydrous ethanol.

[0113] For example, the mass ratio of the hydrofluoric acid solution to the anhydrous ethanol ranges from 1:0.5 to 1:2. For example, the mass ratio of the hydrofluoric acid solution to the anhydrous ethanol can be 1:0.5, 1:1, 1:1.5 or 1:2, etc.

[0114] In the embodiment of the present application, anhydrous ethanol can reduce the surface tension of the etching solution, which is beneficial for the etching solution to penetrate into the sample to be peeled off.

[0115] In some embodiments, a three-electrode system is used, the sample to be stripped is used as the working electrode (ie, the anode), and a reference electrode and a counter electrode are placed in the etching solution.

[0116] In some embodiments, the reference electrode comprises: a mercury / mercury oxide electrode. The counter electrode comprises: a graphite electrode.

[0117] Here, it should be noted that the three-electrode system is an electronic device consisting of a working electrode, a reference electrode and a counter electrode. The working principle of the three-electrode system is based on the electrochemical reaction occurring at the electrode interface. In the three-electrode system, the working electrode is the main electrode used to trigger the electrochemical reaction; the reference electrode provides a stable potential reference for measuring the potential of the working electrode; the counter electrode is used to provide current to promote the electrochemical reaction. A major advantage of the three-electrode system is that it can achieve potential control and measurement accuracy. The reference electrode provides a stable and reproducible potential reference, and by connecting to the working electrode, it can provide an accurate potential measurement benchmark. In this way, by measuring the potential difference between the working electrode and the reference electrode, the electrochemical reaction can be accurately calculated and controlled. In addition, the presence of the counter electrode can provide additional current to promote the electrochemical reaction.

[0118] In some embodiments, an insulating layer 2 is further disposed on a side of the N-type substrate 1 facing away from the depletion region 10 .

[0119] In some examples, the material of the insulating layer 2 may include, but is not limited to, silicon oxide.

[0120] In step S300, please continue to refer to Figure 3 A light source with a preset wavelength is used to vertically illuminate the P-type epitaxial layer 11, and the P-type epitaxial layer 11 absorbs the light emitted by the light source and generates hole h-electron e pairs.

[0121] In some embodiments, the light source includes a xenon lamp, a mercury lamp, or an LED ultraviolet lamp.

[0122] In some embodiments, step S300 uses a light source of a preset wavelength to vertically irradiate the P-type epitaxial layer 11, and the P-type epitaxial layer 11 absorbs the light emitted by the light source and generates hole h-electron e pairs, including: under room temperature conditions, using a 400W xenon lamp as the light source, and using an ultraviolet reflecting lens or filter, so that the wavelength of the light irradiating the sample to be stripped meets the preset wavelength.

[0123] In some embodiments, the preset wavelength range includes: 180nm to 380nm. For example, the preset wavelength can be 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm or 380nm, etc.

[0124] In some embodiments, the shortest distance between the light source and the etching liquid surface ranges from 5 cm to 15 cm. For example, the shortest distance between the light source and the etching liquid surface can be 5 cm, 7 cm, 9 cm, 11 cm, 13 cm or 15 cm.

[0125] In step S400, please continue to refer to Figure 3 During the irradiation process, a preset constant forward potential is provided to the N-type substrate 1, and the etching solution is stirred, so that the electrons e in the depletion region 10 are transferred to the counter electrode along the current to react with the oxidant, and the holes h react with the silicon oxide etching solution on the side of the depletion region 10 close to the P-type epitaxial layer 11 to achieve the stripping of the P-type epitaxial layer 11. Among them, the depletion region 10 is located in the contact area between the N-type substrate 1 and the P-type epitaxial layer 11.

[0126] In some embodiments, relative to the reference electrode, the preset constant forward potential range includes: 1 volt to 15 volts. For example, the preset constant forward potential can be: 1 volt, 3 volts, 5 volts, 7 volts, 9 volts, 11 volts, 13 volts or 15 volts, etc.

[0127] In some embodiments, while providing a preset constant forward potential to the sample to be stripped, step S400 also includes: stirring the etching solution. For example, a stirrer may be used to stir the etching solution.

[0128] The speed range of the stirrer includes: 300r / min-500r / min. For example, the speed of the stirrer can be: 300r / min, 320r / min, 340r / min, 360r / min, 380r / min, 400r / min, 420r / min, 440r / min, 460r / min, 480r / min or 500r / min, etc.

[0129] The flow rate of the etching solution ranges from 1 mL / min to 5 mL / min. For example, the flow rate of the etching solution may be 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min or 5 mL / min.

[0130] Here, it should be noted that in the three-electrode system, by adding an external potential to the working electrode, the ions in the etching solution will undergo a redox reaction under the action of the potential. The potential difference between the reference electrode and the working electrode is called the potential between the working electrode and the reference electrode, and the current caused by the potential difference between the reference electrode and the counter electrode is called the reference electrode current. In this system, the current generated by the working electrode is obtained by measuring the potential difference between the working electrode and the reference electrode.

[0131] In some examples, when a constant forward potential is provided to the N-type substrate 1, there is an internal electric field in the depletion region 10 at the interface between the P-type epitaxial layer 11 and the N-type substrate 1, with the N-type pointing to the P-type (for example, in the Y direction), and there is an electric field in the solid-liquid interface between the P-type epitaxial layer 11 and the etching liquid, with the etching liquid pointing to the P-type epitaxial layer 11 (for example, in the X direction). The holes h in the depletion region 10 move toward the P-type epitaxial layer 11, and the holes h inside the P-type epitaxial layer 11 also move to the depletion region 10. On the side of the depletion region 10 close to the P-type epitaxial layer 11, an oxidation reaction occurs: Si+H 2 O 2 +2h + →SiO 2 +2H + The electrons e in the depletion region 10 will move to the side of the N-type substrate 1 and transfer along the current to the counter electrode to undergo a reduction reaction: 2H++H 2 O 2 +2e - -→2H 2 O. Among them, SiO 2 The chemical formula for the reaction with hydrofluoric acid solution is: SiO 2 +6HF→(SiF 6 ) 2- +2H 2 O+2H + .

[0132] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features of the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0133] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for stripping an epitaxial layer, characterized in that: include: Providing a sample to be peeled off; wherein the sample to be peeled off comprises a substrate and an epitaxial layer stacked in a thickness direction; the conductivity types of the substrate and the epitaxial layer are opposite; Immersing the sample to be stripped in an etching solution; wherein the sample to be stripped serves as a working electrode; Using a light source of a preset wavelength to irradiate the sample to be stripped, so that the sample to be stripped generates hole-electron pairs; During the irradiation process, a preset constant forward potential is provided to the sample to be peeled off.

2. The method for stripping an epitaxial layer according to claim 1, characterized in that: A reference electrode and a counter electrode are arranged in the etching solution; the reference electrode comprises a mercury / mercury oxide electrode; and the counter electrode comprises a graphite electrode.

3. The method for stripping an epitaxial layer according to claim 2, characterized in that: The etching solution includes an oxidant and a silicon oxide etching solution.

4. The method for stripping an epitaxial layer according to claim 3, characterized in that: The providing a preset constant forward potential to the sample to be stripped comprises: providing a preset constant forward potential to the sample to be stripped, so that electrons in the depletion region are transferred to the counter electrode along the current to react with the oxidant, and the silicon oxide etching solution selectively etches the depletion region having holes, thereby achieving stripping of the epitaxial layer; Wherein, the depletion region is located in the contact area between the substrate and the epitaxial layer.

5. The method for stripping an epitaxial layer according to claim 3, characterized in that: The etching solution also includes anhydrous ethanol; the oxidant includes a hydrogen peroxide solution; the silicon oxide etching solution includes a hydrofluoric acid solution; Wherein, the mass fraction range of the hydrogen peroxide solution includes: 3% to 30%; the mass ratio range of the hydrofluoric acid solution and anhydrous ethanol includes: 1:0.5 to 1:

2.

6. The method for stripping an epitaxial layer according to claim 2, wherein: Relative to the reference electrode, the preset constant forward potential range includes: 1 volt to 15 volts.

7. The method for stripping an epitaxial layer according to claim 1, characterized in that: The preset wavelength range includes: 180nm~380nm.

8. The method for stripping an epitaxial layer according to claim 1, wherein: The size range of the sample to be peeled off includes: 2 inches to 12 inches; the thickness range of the epitaxial layer includes: 10 μm to 100 μm.

9. The method for stripping an epitaxial layer according to claim 1, wherein: The shortest distance between the light source and the etching liquid surface ranges from 5 cm to 15 cm.

10. The method for stripping an epitaxial layer according to claim 1, wherein: The flow rate range of the etching solution includes: 1 mL / min to 5 mL / min.

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