CN118116792A - Process method for adjusting warping and composite film - Google Patents
Process method for adjusting warping and composite film Download PDFInfo
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Abstract
The application provides a process method for adjusting warping and a composite film, wherein the method comprises the steps of preparing a substrate wafer and a donor wafer; preprocessing the substrate wafer, and bonding the substrate wafer and the donor wafer to form a composite film; thinning the front film layer of the composite film for one time by etching; performing secondary thinning on the back substrate wafer of the composite film; and (3) carrying out high-temperature annealing on the thinned composite film to remove residual stress. The front surface film layer of the composite film is thinned firstly through etching, in order to reduce uneven surface thickness caused by too fast etching rate, the back surface substrate surface of the composite film is thinned after the front surface thinning is finished, so as to offset surface residual stress generated by a thinning process on the process surface side, and further the composite film is thinned according to different application scenes, and the problem of obvious warping defect of the composite film is solved through controlling the thinning amount.
Description
Technical Field
The application relates to the technical field of semiconductor element preparation, in particular to a process method for adjusting warping and a composite film.
Background
The composite film material meets the requirements of electronic components on miniaturization, low power consumption and high performance development. A thin film structure material called a thin film on insulator, which mainly comprises an uppermost donor wafer, an intermediate insulating dielectric layer and a semiconductor substrate, is becoming more and more important in industry. The donor wafer may be a semiconductor film (e.g., si, ge, gaAs, siC), a piezoelectric film (lithium niobate and lithium tantalate), a ferroelectric film, or the like. The material has good application performance in CPU chips, memories, amplifiers, filters and modulators.
Composite film warpage is an important indicator in semiconductor fabrication. The warpage of the composite film refers to the degree of bending of the substrate wafer and the donor wafer during the processing and use of the composite film. The composite films have different shrinkage rates due to the action of unreeling tension and heating temperature when the films are compounded together, so that the composite films generate internal stress, and the distribution and the balance state of the internal stress determine the final curling degree and state of the composite films. Because of the heterogeneous bonding (films of two different materials are bonded together, the degree of shrinkage after heating is different due to the different coefficients of thermal expansion) there is some warpage, which can affect the subsequent device fabrication process. For example, if the substrate is warped too much, the lithography machine needs to refocus every step, which seriously affects the efficiency of the lithography process. Therefore, in the actual production process, the warping degree of the composite film needs to be controlled.
Disclosure of Invention
The application provides a process method for adjusting warping and a composite film, which are used for solving the problem of obvious warping defect of the composite film.
In a first aspect, the present application provides a method for adjusting warpage, comprising:
preparing a substrate wafer and a donor wafer; wherein the substrate wafer and the donor wafer are different in material;
preprocessing the substrate wafer, and bonding the substrate wafer and the donor wafer to form a composite film;
thinning the front film layer of the composite film for one time by etching;
Performing secondary thinning on the back substrate wafer of the composite film;
And (3) carrying out high-temperature annealing on the thinned composite film to remove residual stress.
In some possible implementations, the thickness of the composite film is H, the thinning amount of the film layer is H f, the thinning amount of the back substrate wafer is H s, and the total thinning amount H f+hs is less than 1/3H.
In some possible implementations, the thin film layer thinning amount h f accounts for 70-90% of the total thinning amount.
In some possible implementations, the thinning rate of the primary thinning and the secondary thinning is less than or equal to 0.25 μm/s.
In some possible implementations, when the front film layer of the composite film is thinned by etching, the etching method includes wet etching or dry etching.
In some possible implementations, pre-processing the substrate wafer, and bonding the substrate wafer and the donor wafer to form a composite film includes:
preparing an isolation layer on the substrate wafer;
and bonding the isolation layer on the substrate wafer with the donor wafer to form a composite film.
In some possible implementations, pre-processing the substrate wafer, and bonding the substrate wafer and the donor wafer to form a composite film includes:
Preparing a defect layer on the substrate wafer;
preparing an isolation layer on the defect layer;
and bonding the isolation layer on the substrate wafer with the donor wafer to form a composite film.
In some possible implementations, the thinned composite film is annealed at a high temperature of 100-600 ℃ for 1 min-48 h.
In some possible implementations, the donor wafer selects at least one of a lithium niobate crystal, a lithium tantalate crystal, gallium arsenide, silicon, a ceramic, lithium tetraborate, gallium arsenide, potassium titanyl phosphate, rubidium titanyl phosphate crystal, or a thin film of quartz; the substrate wafer is made of at least one of silicon, sapphire, quartz, silicon carbide, silicon nitride, lithium niobate, lithium tantalate or quartz glass.
In a second aspect, the present application provides a composite film obtainable by the process of the first aspect.
From the foregoing, the present application provides a method for adjusting warpage and a composite film, the method comprising preparing a substrate wafer and a donor wafer; wherein the substrate wafer and the donor wafer are different in material; bonding the substrate wafer and the donor wafer to form a composite film; thinning the front film layer of the composite film for one time by etching; performing secondary thinning on the back substrate wafer of the composite film; and (3) carrying out high-temperature annealing on the thinned composite film to remove residual stress. The front surface film layer of the composite film is thinned firstly through etching, in order to reduce uneven surface thickness caused by too fast etching rate, the back surface substrate surface of the composite film is thinned after the front surface thinning is finished, so as to offset surface residual stress generated by a thinning process on the process surface side, and further the composite film is thinned according to different application scenes, and the problem of obvious warping defect of the composite film is solved through controlling the thinning amount.
Drawings
In order to more clearly illustrate the technical solution of the present application, the drawings that are needed in the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic view of a process for adjusting warpage in an embodiment of the present application;
fig. 2 is a schematic view of a second scenario of a process for adjusting warpage in an embodiment of the present application.
Detailed Description
Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The embodiments described in the examples below do not represent all embodiments consistent with the application. Merely exemplary of systems and methods consistent with aspects of the application as set forth in the claims.
The composite film material meets the requirements of electronic components on miniaturization, low power consumption and high performance development. A thin film structure material called a thin film on insulator, which mainly comprises an uppermost donor wafer, an intermediate insulating dielectric layer and a semiconductor substrate, is becoming more and more important in industry. The donor wafer may be a semiconductor film (e.g., si, ge, gaAs, siC), a piezoelectric film (lithium niobate and lithium tantalate), a ferroelectric film, or the like. The material has good application performance in CPU chips, memories, amplifiers, filters and modulators.
Composite film warpage is an important indicator in semiconductor fabrication. The warpage of the composite film refers to the degree of bending of the substrate wafer and the donor wafer during the processing and use of the composite film. The composite films have different shrinkage rates due to the action of unreeling tension and heating temperature when the films are compounded together, so that the composite films generate internal stress, and the distribution and the balance state of the internal stress determine the final curling degree and state of the composite films. Because of the heterogeneous bonding (films of two different materials are bonded together, the degree of shrinkage after heating is different due to the different coefficients of thermal expansion) there is some warpage, which can affect the subsequent device fabrication process. For example, if the substrate is warped too much, the lithography machine needs to refocus every step, which seriously affects the efficiency of the lithography process.
The factors that are currently believed to cause the warpage of the composite film are: 1) Materials: the wafer warpage degree of different materials is obviously different; 2) Size: the weight of the wafer can influence the warpage, and the larger the weight of the wafer is, the larger the corresponding warpage is; 3) Processing stress: stress in the processing process acts on the wafer, such as grinding, polishing, cutting, corrosion and the like, and the stress state of the wafer is changed, so that the wafer warpage is increased; 4) Temperature: during the heating process, the wafer is heated and expanded at a temperature which causes the wafer to bend.
Silicide layers are typically deposited on the wafer finished or substrate backside to improve films that have been warped, but if the warpage of the film has reached a level where silicide is deposited on the substrate backside, warpage tends to be more severe. In addition, silicide may be deposited using plasma chemical vapor deposition, but the temperature at the time of plasma chemical vapor deposition is high, and if silicide is deposited on the backside of the substrate using plasma chemical vapor deposition, the thin film on the wafer surface is easily damaged, and the performance of the electrode, semiconductor, etc. on the wafer surface may be affected. In addition, since the lithium niobate thin film has piezoelectricity, if silicide is redeposited on the back of the finished lithium niobate thin film, the silicide applies stress (compressive or tensile force) to the lithium niobate thin film, so that the refractive index of the lithium niobate thin film is changed, thereby affecting the performance of the lithium niobate thin film. Therefore, in the actual production process, the warping degree of the composite film needs to be controlled.
Based on the method, the front film layer of the composite film is thinned through etching, so that uneven surface thickness caused by too high etching rate is reduced, and after the front thinning is finished, the back substrate surface of the composite film is thinned, so that surface residual stress on the process surface side due to the thinning process is counteracted, the composite film is thinned according to different application scenes, and the problem of obvious warping defect of the composite film is solved through controlling the thinning amount.
As shown in fig. 1, in some embodiments, the present application provides a method for adjusting warpage, the method comprising:
s1: preparing a substrate wafer and a donor wafer; wherein the substrate wafer and the donor wafer are different in material.
S2: and preprocessing the substrate wafer.
The donor wafer is a base material with a certain thickness for obtaining a thin film layer. The donor wafer is selected from at least one of lithium niobate crystal, lithium tantalate crystal, gallium arsenide, silicon, ceramic, lithium tetraborate, gallium arsenide, potassium titanyl phosphate, rubidium titanyl phosphate crystal, and quartz thin film, which is not limited in the present application.
It should be noted that, in some embodiments, the substrate wafer includes the substrate layer 110, where the substrate layer 110 mainly plays a role of supporting, and the substrate layer 110 may be a single-layer substrate or a composite substrate. If the substrate layers 110 are composite substrates, the materials of each of the substrate layers 110 may be the same or different, as the application is not limited in this regard. For example: the substrate wafer is made of at least one of silicon, sapphire, quartz, silicon carbide, silicon nitride, lithium niobate, lithium tantalate or quartz glass.
In some possible embodiments, after preparing a substrate wafer, pre-processing the substrate wafer includes:
An isolation layer is prepared on the substrate wafer.
The isolation layer 120 may be formed by deposition or oxidation, and the deposition method is not limited, and may be Chemical Vapor Deposition (CVD), physical Vapor Deposition (PVD), magnetron sputtering, etc.
The isolation layer 120 can prevent signal crosstalk between adjacent films, and the isolation layer 120 is made of silicon dioxide, silicon nitride, aluminum oxide, or aluminum nitride. Specification selection for each layer: in some embodiments, the application is not limited to the substrate layer 110, the isolation layer 120. For example, the thickness of the substrate layer 110 may be 0.3 to 0.8mm, and the thickness of the isolation layer 120 may be 50nm to 1000nm.
Meanwhile, in order to prolong the life of PSC (parasitic surface conduction), a defect layer 100 may be added on the basis of the thin film of the current substrate wafer, and the substrate layer 110, the defect layer 100 and the isolation layer 120 are sequentially stacked; the defect layer 100 may be made of a semiconductor material, and the defect layer 100 has lattice defects for trapping parasitic carriers.
Thus, in some possible embodiments, after preparing a substrate wafer, pre-processing the substrate wafer comprises:
Preparing a defect layer on the substrate wafer;
and preparing an isolation layer on the defect layer.
The present application may further deposit a defect layer 100 on the isolation layer 120, and when the defect layer 100 is a polysilicon layer and the polysilicon layer is oxidized, the isolation layer 120 is silicon dioxide; the deposition method is not limited, and may be Chemical Vapor Deposition (CVD), physical Vapor Deposition (PVD), magnetron sputtering, or the like. The thickness of the isolation layer 120 may be 200nm to 3000nm; the isolation layer 120 is prepared by oxidation: oxidizing the polysilicon layer, wherein one side of the polysilicon layer far away from the substrate is oxidized to form a silicon dioxide layer, and one side of the polysilicon layer close to the substrate is not oxidized; the oxidation temperature is 900-1000 ℃;
The material of the defect layer 100 is at least one of polysilicon, amorphous silicon, or poly-germanium. The defect layer 100 may be formed by depositing polysilicon by deposition, amorphous silicon by deposition, polycrystalline germanium by deposition, etching a substrate wafer by etching, or implanting a substrate wafer by implantation to create implantation damage. Then, a deposition method or an oxidation method is used to manufacture an isolation layer 120 on the defect layer 100, and the isolation layer 120 is made of at least one of silicon dioxide, silicon oxynitride or silicon nitride.
The defect layer 100 has lattice defects with a certain density, and can capture carriers existing between the isolation layer 120 and the substrate layer 110, so as to avoid the carriers from causing the carrier aggregation at the interface of the isolation layer 120 and the substrate layer 110, and reduce the loss of the composite film. Illustratively, the defect layer 100 may have a thickness of 300nm to 5000nm.
For example: when the defect layer 100 is a polysilicon layer, the polysilicon layer is oxidized, and the isolation layer 120 is made of silicon dioxide. The method of preparing the isolation layer 120 by deposition is not limited, and may be a Chemical Vapor Deposition (CVD), a Physical Vapor Deposition (PVD), a magnetron sputtering, or the like. The thickness of the isolation layer may be 200nm to 3000nm.
When the isolation layer 120 is prepared by an oxidation method, the polysilicon layer is subjected to an oxidation treatment. Wherein, the side of the polysilicon layer far away from the substrate wafer is oxidized to form a silicon dioxide layer, forming an isolation layer 120, and the side of the polysilicon layer near the substrate wafer is not oxidized; the oxidation temperature at which the spacer layer 120 is prepared by the oxidation process may be 900-1000 c.
S3: and bonding the substrate wafer and the donor wafer to form a composite film.
In some embodiments, the functional implantation wafer may be obtained by implanting ions into the process surface of the donor wafer based on an ion implantation method, where the functional implantation wafer sequentially includes a functional layer 130, an implantation layer, and a residual layer, the functional layer 130 of the implantation wafer is bonded to the substrate wafer to form a bonded body, the bonded body is annealed, and the annealed bonded body is broken at the implantation layer to peel off the residual layer from the bonded body along the implantation layer, so that the functional layer 130 of the donor wafer is transferred onto the substrate wafer to form a composite film.
The ion implantation method in the embodiment of the present application is not particularly limited, and any ion implantation method in the prior art may be used, and the implanted ions may be ions capable of generating gas by heat treatment, for example: the implanted ions may be hydrogen ions, helium ions, nitrogen ions, oxygen ions, or argon ions. For example: hydrogen ions or helium ions. When hydrogen ions are injected, the injection dosage can be 3 multiplied by 10 16ions/cm2～8×1016ions/cm2, and the injection energy can be 100 KeV-400 KeV; when helium ions are injected, the injection dose may be 1×10 16ions/cm2～1×1017ions/cm2 and the injection energy may be 50KeV to 1000KeV. For example, when hydrogen ions are injected, the injection dose may be 4×10 16ions/cm2 and the injection energy may be 180KeV; when helium ions are implanted, the implantation dose is 4×10 16ions/cm2 and the implantation energy is 200KeV. In the embodiment of the present application, the thickness of the thin film layer 130 may be adjusted by adjusting the ion implantation depth, specifically, the greater the ion implantation depth, the greater the thickness of the prepared thin film layer 130; conversely, the smaller the depth of ion implantation, the smaller the thickness of the prepared thin film layer 130. In the application, the diffusion width of the ion implantation layer can be adjusted by adjusting the ion implantation dosage, specifically, the larger the ion implantation dosage is, the wider the diffusion width of the ion implantation layer is; conversely, the smaller the dose of ion implantation, the narrower the diffusion width of the ion implantation layer.
The bonding method of the donor wafer and the processed substrate wafer is not particularly limited, and any bonding method of the donor wafer and the processed substrate wafer in the prior art can be adopted, for example, the bonding surface of the donor wafer is subjected to surface activation, the bonding surface of the processed substrate wafer is also subjected to surface activation, and then the two activated surfaces are bonded to obtain a bonded body. Specifically, the donor wafer surface and the substrate wafer are cleaned, and the thin film layer 130 of the cleaned donor wafer is bonded with the silicon dioxide layer by adopting a plasma bonding method to form a bonded body.
In some embodiments, the bond is heat treated at a temperature of 180-600 ℃, wherein the annealing includes a first annealing step to strip the excess layer at a temperature in the range of 180-300 ℃ and a second annealing step to separate the thin film layer 130 from the excess layer at a temperature in the range of 300-600 ℃ and to eliminate implantation damage. Annealing the bond for 1-100 hours at 180-600 ℃, forming bubbles in the implanted layer, e.g., H ions forming hydrogen, he ions forming helium, etc., along with the progress of the heat treatment, the bubbles in the implanted layer are connected into one piece, and finally the implanted layer is split to separate the residual layer from the thin film layer 130, thereby peeling the residual layer from the bond, and forming the thin film layer 130 on the top surface of the processed substrate.
S4: and thinning the front film layer of the composite film once by etching.
The front film layer 130 of the composite film is thinned by etching to reduce uneven surface thickness caused by too fast etching rate. Wherein the etching is wet etching or dry etching.
The dry etching firstly cleans and surface-treats the substrate of the composite film, and removes surface impurities and oxide layers so as to ensure the etching quality and effect. The etching gas is typically a fluorine-containing compound gas such as Hydrogen Fluoride (HF) or fluoromethane (CHF 3), etc. The choice of etching gas takes into account factors such as etch rate, etch quality, and etch planarity.
After the substrate is pretreated, an etching device is used for introducing etching gas into an etching chamber, and the etching rate and the etching quality in the etching process are controlled by adjusting parameters such as the flow rate, the temperature and the like of the etching gas. The pretreated composite film is placed in an etching chamber and exposed to an etching gas. The fluoride in the etching gas can chemically react with the material on the surface of the composite film to generate a gas product, thereby realizing the etching effect. Wherein, according to actual need, the etching depth and the etching shape are controlled by adjusting parameters such as etching time, etching conditions and the like. After etching, cleaning and surface treatment are carried out on the etched composite film so as to remove etching products and residual etching gas, and the surface finish of the composite film meets the requirements.
The etching accuracy of the dry etching is higher, so that the etching to the silicon dioxide layer can be accurately controlled. In some embodiments, the dry etching may be performed by reactive ion etching Reactive Ion Etching or RIE, or by plasma etching, such as inductively coupled plasma etching (Inductively Coupled Plasma, ICP technique).
S5: and carrying out secondary thinning on the back substrate wafer of the composite film.
Thinning the back substrate surface of the composite film to offset the surface residual stress generated by the thinning process on the process side.
The thickness of the composite film is H, the thinning amount of the film layer is H f, the thinning amount of the back substrate wafer is H s, and the total thinning amount H f+hs is smaller than 1/3H. In some embodiments, the thinning amount h f of the film layer accounts for 70-90% of the total thinning amount.
In some embodiments, the thinning rate of the primary thinning and the secondary thinning is less than or equal to 0.25 μm/s.
S6: and (3) carrying out high-temperature annealing on the thinned composite film to remove residual stress.
The front film layer 130 of the composite film is thinned by etching, and after the front thinning is finished, the back substrate surface of the composite film is thinned to offset the surface residual stress generated by the thinning process on the process surface side, so as to reduce the uneven surface thickness caused by the excessively fast etching rate. Wherein, the wafer warpage after one thinning is 80-100 μm, and the warpage after double-sided thinning is reduced to 20-40 μm.
In some embodiments, the present application provides a composite film obtained by the above method.
In some embodiments, the present application provides an electronic component, including the above composite film.
The invention is further described below in connection with specific embodiments.
Example 1:
1. Preparing a silicon wafer and a lithium tantalate wafer of 6 inches, respectively fixing the silicon wafer or the lithium tantalate wafer on a porous ceramic sucker of polishing equipment, performing chemical mechanical polishing treatment to obtain a smooth surface, and then performing semiconductor RCA cleaning on the two wafers to obtain a clean surface.
2. Cleaning a lithium tantalate wafer and a silicon wafer, and bonding the cleaned technological surface of the lithium tantalate with the silicon wafer by adopting a plasma bonding method to form a composite film, wherein the thickness of the composite film is H=1025 mu m; the method for carrying out surface activation on the technical surface of the lithium tantalate is not particularly limited, and any method in the prior art for carrying out surface activation on the technical surface of the film can be adopted, for example, plasma activation, chemical solution activation and the like; similarly, the surface activation method of the bonding surface of the silicon wafer is not particularly limited, and any method of the prior art that can be used for surface activation of the bonding surface of the silicon wafer, such as plasma activation, can be used.
3. The front film layer 130 of the composite film is thinned for one time by etching, wherein the thickness of the first thinning is h f =270 mu m, the thinning is performed for 3 times, the thinning speed is 0.2 mu m/s, and the uneven surface thickness caused by the too fast etching speed is reduced.
4. Performing secondary thinning on the back substrate surface of the composite film, wherein the thickness of the secondary thinning is h S = 15 mu m, and the thinning speed is 0.2 mu m/s so as to offset the surface residual stress generated by the thinning process on the process surface side; wherein, the wafer warp 80 mu m after one thinning, and the warp is reduced to 20 mu m after double-sided thinning.
5. And (3) carrying out high-temperature annealing on the composite film to remove residual stress, wherein the annealing temperature is 100-600 ℃, and the annealing time is 1 min-48 hours.
Example 2
Fig. 1 is a schematic view of a process for adjusting warpage according to the present embodiment.
1. Preparing a silicon wafer and a lithium niobate wafer of 6 inches, respectively fixing the silicon wafer or the lithium niobate wafer on a porous ceramic sucker of polishing equipment, performing chemical mechanical polishing treatment to obtain a smooth surface, and then cleaning the two wafers by using semiconductor RCA (industry standard wet cleaning process) to obtain a clean surface.
2. Depositing a silicon dioxide layer on the cleaned silicon wafer by adopting an LPCVD (low pressure chemical vapor deposition) process, adopting an LPCVD process (including but not limited to sputtering, evaporation, electroplating and the like), then carrying out chemical mechanical polishing to a thickness of 100nm to obtain a smooth surface, and cleaning RCA to obtain a clean surface; the silicon wafer is sequentially provided with a substrate layer 110 and the isolation layer 120 from bottom to top.
3. Cleaning a lithium niobate wafer and a silicon dioxide layer, and bonding the process surface of the cleaned lithium niobate thin film layer with the silicon dioxide layer by adopting a plasma bonding method to form a composite thin film, wherein the thickness H=1025 mu m of the composite thin film; the method for carrying out surface activation on the technical surface of the lithium niobate is not particularly limited, and any method for carrying out surface activation on the technical surface of the film in the prior art can be adopted, for example, plasma activation, chemical solution activation and the like; in the same manner, the surface activation method of the silica bonding surface is not particularly limited, and any method that can be used for surface activation of the silica bonding surface in the prior art, for example, plasma activation, can be used.
4. The front film layer 130 of the composite film is thinned for one time by etching, wherein the thickness of the first thinning is h f =260 mu m, the thinning is performed for 4 times, the thinning speed is 0.2 mu m/s, and the uneven surface thickness caused by the too fast etching speed is reduced.
5. Performing secondary thinning on the back substrate surface of the composite film, wherein the thickness of the secondary thinning is h S = 20 mu m, and the thinning speed is 0.2 mu m/s so as to offset the surface residual stress generated by the thinning process on the process surface side; wherein, the wafer warp 90 mu m after one thinning, and the warp is reduced to 30 mu m after double-sided thinning.
6. And (3) carrying out high-temperature annealing on the composite film to remove residual stress, wherein the annealing temperature is 100-600 ℃, and the annealing time is 1 min-48 hours.
Example 3
Fig. 2 is a schematic view of a process for adjusting warpage according to the present embodiment.
1. Preparing a 3-inch silicon wafer and a lithium niobate wafer, respectively fixing the silicon wafer or the lithium niobate wafer on a porous ceramic sucker of polishing equipment, performing chemical mechanical polishing treatment to obtain a smooth surface, and then performing semiconductor RCA cleaning on the two wafers to obtain a clean surface.
2. A polysilicon layer is formed on the cleaned silicon wafer by PECVD (including but not limited to sputtering, evaporation, electroplating, etc.), and the polysilicon layer has a thickness of 1 μm.
3. A silicon dioxide layer is formed on the polysilicon layer by LPCVD (including but not limited to sputtering, evaporation, electroplating, etc.), and then chemical mechanical polishing is performed to obtain a smooth surface, a thickness of 1 μm, and RCA cleaning is performed to obtain a clean surface. The silicon wafer is sequentially provided with a substrate layer 110, the defect layer 100 and the isolation layer 120 from bottom to top.
4. Cleaning a lithium niobate wafer and a silicon dioxide layer, and bonding the cleaned technological surface of the lithium niobate with the silicon dioxide layer by adopting a plasma bonding method to form a composite film, wherein the thickness H=650 mu m; the method for carrying out surface activation on the technical surface of the lithium niobate thin film is not particularly limited, and any method in the prior art for carrying out surface activation on the technical surface of the thin film can be adopted, for example, plasma activation, chemical solution activation and the like; in the same manner, the surface activation method of the silica bonding surface is not particularly limited, and any method that can be used for surface activation of the silica bonding surface in the prior art, for example, plasma activation, can be used.
5. The front film layer 130 of the composite film is thinned once by etching, the thickness of the once thinning is h f =180 μm, the thinning is performed twice, the thinning speed is 0.2 μm/s, and the uneven surface thickness caused by the too fast etching speed is reduced.
6. Performing secondary thinning on the back substrate surface of the composite film, wherein the thickness of the secondary thinning is h S = 15 mu m, and the thinning speed is 0.2 mu m/s so as to offset the surface residual stress generated by the thinning process on the process surface side; wherein, the wafer warp 100 mu m after one thinning, and the warp is reduced to 40 mu m after double-sided thinning.
7. And (3) carrying out high-temperature annealing on the composite film to remove residual stress, wherein the annealing temperature is 100-600 ℃, and the annealing time is 1 min-48 hours.
Example 4
1. Preparing a 4-inch silicon wafer and a lithium niobate wafer, respectively fixing the silicon wafer or the lithium niobate wafer on a porous ceramic sucker of polishing equipment, performing chemical mechanical polishing treatment to obtain a smooth surface, and then performing semiconductor RCA cleaning on the two wafers to obtain a clean surface.
2. A polysilicon layer is formed on the cleaned silicon wafer by PECVD (including but not limited to sputtering, evaporation, electroplating, etc.), and the polysilicon layer has a thickness of 1 μm.
3. A silicon dioxide layer is formed on the polysilicon layer by LPCVD (including but not limited to sputtering, evaporation, electroplating, etc.), and then chemical mechanical polishing is performed to obtain a smooth surface, a thickness of 1 μm, and RCA cleaning is performed to obtain a clean surface. The silicon wafer is sequentially provided with a substrate layer 110, the defect layer 100 and the isolation layer 120 from bottom to top.
4. And (2) injecting He + into the lithium niobate wafer processed in the step (1) by adopting a stripping ion injection method, so that the lithium niobate wafer is sequentially divided into a residual layer, a separation layer and a film layer 130 from an injection surface, and the injected He + ions are distributed on the separation layer to obtain the single crystal lithium niobate wafer injection sheet.
When He + is injected by a stripping ion implantation method, the implantation dose parameters are as follows: the depth of ion implantation was 840nm, the implantation energy was 250kev, and the implantation dose was 2×10 16ions/cm2.
5. Cleaning a film layer 130 of the monocrystalline lithium niobate wafer injection sheet and a silicon dioxide layer, and bonding the process surface of the cleaned lithium niobate film layer and the silicon dioxide layer by adopting a plasma bonding method to form a bonding body; the method for carrying out surface activation on the technical surface of the lithium niobate thin film is not particularly limited, and any method in the prior art for carrying out surface activation on the technical surface of the thin film can be adopted, for example, plasma activation, chemical solution activation and the like; in the same manner, the surface activation method of the silica bonding surface is not particularly limited, and any method that can be used for surface activation of the silica bonding surface in the prior art, for example, plasma activation, can be used.
6. The bond is then annealed at high temperature in a heating apparatus until the remainder of the layer separates from the bond to form a lithium niobate composite film, h=1025 μm. The heat preservation process is carried out in a vacuum environment or in a protective atmosphere formed by at least one gas of nitrogen and inert gas, the annealing temperature is 100-600 ℃, the annealing time (1 min-48 h) comprises a first annealing and a second annealing, the first annealing is carried out at 100-300 ℃ to strip off the residual layer, the film layer 130 is separated from the residual layer, and the second annealing is carried out at 300-600 ℃ to eliminate injection damage. The link can promote bonding force to be more than 10MPa, and can recover damage of ion implantation to the film layer 130, so that the obtained lithium niobate film layer 130 approximates to the property of a lithium niobate wafer. The bonded body is placed in a heating apparatus to be held at a predetermined temperature for a predetermined time. In this process, ions in the separation layer chemically react to become gas molecules or atoms, and minute bubbles are generated, and as the heating time is prolonged or the heating temperature is increased, the bubbles become more and more, and the volume is also gradually increased. When these bubbles are connected together, separation of the residual material layer from the separation layer is achieved, thereby transferring the thin film layer 130 to the separation layer and forming a composite structure. Then, the composite structure may be placed in a heating apparatus to be held at a predetermined temperature for a predetermined time, thereby eliminating damage caused by the ion implantation process. Then, the thin film layer 130 on the isolation layer may be ground and polished to a predetermined thickness, and a composite thin film may be obtained.
7. The front film layer 130 of the composite film is thinned once by etching, the thickness of the once thinning is h f =270 mu m, the thinning is performed three times, the thinning speed is 0.2 mu m/s, and the uneven surface thickness caused by the too fast etching speed is reduced.
8. Performing secondary thinning on the back substrate surface of the composite film, wherein the thickness of the secondary thinning is h S = 20 mu m, and the thinning speed is 0.2 mu m/s so as to offset the surface residual stress generated by the thinning process on the process surface side; wherein, the wafer warp 80 mu m after one thinning, and the warp is reduced to 30 mu m after double-sided thinning.
9. And (3) carrying out high-temperature annealing on the composite film to remove residual stress, wherein the annealing temperature is 100-600 ℃, and the annealing time is 1 min-48 hours.
As can be seen from the above embodiments, the present application provides a method for adjusting warpage and a composite film, the method comprising preparing a substrate wafer and a donor wafer; wherein the substrate wafer and the donor wafer are different in material; bonding the substrate wafer and the donor wafer to form a composite film; thinning the front film layer of the composite film for one time by etching; performing secondary thinning on the back substrate wafer of the composite film; and (3) carrying out high-temperature annealing on the thinned composite film to remove residual stress. The front surface film layer of the composite film is thinned firstly through etching, in order to reduce uneven surface thickness caused by too fast etching rate, the back surface substrate surface of the composite film is thinned after the front surface thinning is finished, so as to offset surface residual stress generated by a thinning process on the process surface side, and further the composite film is thinned according to different application scenes, and the problem of obvious warping defect of the composite film is solved through controlling the thinning amount.
The above-provided detailed description is merely a few examples under the general inventive concept and does not limit the scope of the present application. Any other embodiments which are extended according to the solution of the application without inventive effort fall within the scope of protection of the application for a person skilled in the art.
Claims (10)
1. A process for adjusting warpage comprising:
preparing a substrate wafer and a donor wafer; wherein the substrate wafer and the donor wafer are different in material;
preprocessing the substrate wafer, and bonding the substrate wafer and the donor wafer to form a composite film;
thinning the front film layer of the composite film for one time by etching;
Performing secondary thinning on the back substrate wafer of the composite film;
And (3) carrying out high-temperature annealing on the thinned composite film to remove residual stress.
2. The method of claim 1, wherein the composite film has a thickness H, the film layer thinning amount is H f, the backside substrate wafer thinning amount is H s, and the total thinning amount is H f+hs < 1/3H.
3. The method of claim 2, wherein the film layer thinning h f is 70-90% of the total thinning.
4. The method of claim 1, wherein the thinning rate of the primary thinning and the secondary thinning is less than or equal to 0.25 μm/s.
5. The method according to claim 1, wherein when the front surface film layer of the composite film is thinned by etching, the etching method includes wet etching or dry etching.
6. The method of claim 1, wherein pre-processing the substrate wafer and bonding the substrate wafer and the donor wafer to form a composite film comprises:
preparing an isolation layer on the substrate wafer;
and bonding the isolation layer on the substrate wafer with the donor wafer to form a composite film.
7. The method of claim 1, wherein pre-processing the substrate wafer and bonding the substrate wafer and the donor wafer to form a composite film comprises:
Preparing a defect layer on the substrate wafer;
preparing an isolation layer on the defect layer;
and bonding the isolation layer on the substrate wafer with the donor wafer to form a composite film.
8. The method according to claim 1, wherein the thinned composite film is annealed at a high temperature of 100 to 600 ℃ for 1min to 48h.
9. The method of claim 1, wherein the donor wafer selects at least one of a lithium niobate crystal, a lithium tantalate crystal, gallium arsenide, silicon, ceramic, lithium tetraborate, gallium arsenide, potassium titanyl phosphate, rubidium titanyl phosphate crystal, or a thin film of quartz; the substrate wafer is made of at least one of silicon, sapphire, quartz, silicon carbide, silicon nitride, lithium niobate, lithium tantalate or quartz glass.
10. A composite film, characterized in that it is obtained by the method according to any one of claims 1 to 9.
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