Method for improving bonding interface quality of composite substrate and composite substrate

Abstract

The invention provides a method for improving bonding interface quality of a composite substrate and the composite substrate. The method comprises the following steps: providing two substrates to be bonded, growing a buffer layer on a to-be-bonded surface of at least one of the two substrates, and then carrying out bonding to obtain a composite substrate; the method for growing the buffer layer comprises the following steps: (1) pre-cleaning a reaction chamber, then placing a substrate in the pre-cleaned reaction chamber, and depositing the buffer layer on a to-be-bonded surface of the substrate; and (2) carrying out preliminary cleaning on the surface of the buffer layer obtained by deposition, then turning on radio frequency, introducing oxygen, and carrying out oxygen plasma cleaning. The process before and after deposition of the buffer layer is optimized, the number of particles in the buffer layer can be effectively reduced, and therefore the bonding interface quality of the composite substrate can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors and relates to a method for improving the bonding interface quality of a composite substrate and a composite substrate. Background Art

[0002] Wafer bonding technology is to closely bond two smooth and clean wafers together through different physical or chemical methods to assist semiconductor manufacturing processes or form heterogeneous composite wafers with specific functions. However, due to the mismatch of material properties such as lattice constant and thermal expansion coefficient, stress will be generated, reducing the bonding yield.

[0003] At this time, an intermediate layer is provided between the two different materials to improve the interface characteristics between them, reduce defects, and improve the stability of the overall structure. This intermediate layer is also called a buffer layer. When growing the buffer layer, it is particularly important to control the particles. Too many particles will affect the quality of the bonding interface.

[0004] Therefore, there is an urgent need to provide a solution that can reduce the number of particles in the buffer layer and thus improve the quality of the bonding interface. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for improving the bonding interface quality of a composite substrate and a composite substrate. The present invention optimizes the processes before and after depositing a buffer layer, which can effectively reduce the number of particles in the buffer layer, thereby effectively improving the bonding interface quality of the composite substrate.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for improving the quality of a composite substrate bonding interface, the method comprising:

[0008] Two substrates to be bonded are provided, a buffer layer is grown on the bonding surface of at least one of the two substrates, and then bonding is performed to obtain a composite substrate.

[0009] The method for growing the buffer layer comprises the following steps:

[0010] (1) Pre-cleaning the reaction chamber, then placing the substrate in the pre-cleaned reaction chamber, and depositing a buffer layer on the surface of the substrate to be bonded.

[0011] (2) Preliminary cleaning is performed on the surface of the deposited buffer layer, and then the radio frequency is turned on and oxygen is introduced to perform oxygen plasma cleaning.

[0012] It should be noted that, for two substrates to be bonded, a buffer layer may be grown on the surface to be bonded of any one of the substrates, or may be grown on the surfaces to be bonded of both substrates.

[0013] The present invention pre-cleans the reaction chamber before depositing the buffer layer to remove loose impurity particles in the reaction chamber; after depositing the buffer layer, the surface of the buffer layer is preliminarily cleaned to remove particles that fall on the surface of the buffer layer; after the preliminarily cleaning, the radio frequency is turned on and oxygen is introduced, and the oxygen is converted into oxygen plasma gas phase material under the action of the radio frequency, and the surface of the buffer layer is cleaned by the oxygen plasma gas phase material to remove organic pollutant particles on the surface. In summary, the present invention optimizes the pre- and post-processes of depositing the buffer layer, which can effectively reduce the number of particles in the buffer layer, thereby effectively improving the bonding interface quality of the composite substrate.

[0014] Preferably, the two substrates to be bonded independently include any one of a silicon substrate, an aluminum nitride substrate, a silicon carbide substrate, a polysilicon-on-silicon substrate, a lithium niobate substrate or a lithium tantalate substrate, or a combination of at least two thereof.

[0015] The polysilicon-on-silicon substrate refers to a polysilicon layer grown on a silicon substrate.

[0016] Preferably, the material of the buffer layer includes any one of aluminum oxide, silicon dioxide or silicon nitride, or a combination of at least two of them.

[0017] Preferably, in step (1), before the pre-cleaning, the liner in the reaction chamber is sandblasted.

[0018] In the present invention, the liner in the reaction chamber is sandblasted to remove pollutants on the surface of the liner, thereby improving the bonding force between the buffer layer material and the liner, preventing the upper surface film on the liner from falling off, and further reducing the number of particles in the buffer layer. The surface film mainly refers to the material layer that is inevitably formed on the liner during the growth of the buffer layer.

[0019] Preferably, the abrasive used in the sandblasting process includes SiO2, Al2O3 and Fe.

[0020] Preferably, based on the total mass of the abrasive used in the sandblasting process as 100%, the mass fraction of SiO2 is 70-90%, for example, it can be 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88% or 90%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, based on the total mass of the abrasive used in the sandblasting process as 100%, the mass fraction of Al2O3 is 10-30%, for example, it can be 10%, 15%, 20%, 25% or 30%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, based on the total mass of the abrasive used in the sandblasting process as 100%, the mass fraction of Fe is 0.04-0.06%, for example, it can be 0.04%, 0.045%, 0.05%, 0.055%, 0.058% or 0.06%, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the particle size of the abrasive used in the sandblasting process is 5 to 200 meshes, for example, it can be 5 mesh, 10 mesh, 20 mesh, 50 mesh, 100 mesh, 120 mesh, 150 mesh, 180 mesh or 200 mesh, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, in step (1), the pre-cleaning comprises the following steps: introducing a cleaning gas into the reaction chamber and then evacuating the gas.

[0025] The present invention removes loose impurity particles in the reaction chamber by introducing a cleaning gas and then exhausting the gas.

[0026] Preferably, the cleaning gas comprises nitrogen and / or argon.

[0027] Preferably, the flow rate of the cleaning gas is 2000-4000sccm, for example, it can be 2000sccm, 2200sccm, 2500sccm, 2800sccm, 3000sccm, 3200sccm, 3500sccm, 3800sccm or 4000sccm, etc.; the time for introducing the cleaning gas is 20-40s, for example, it can be 20s, 25s, 30s, 35s or 40s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, during the pre-cleaning process, the steps of introducing the cleaning gas and exhausting the gas are cycled 3 to 5 times, for example, 3 times, 4 times or 5 times.

[0029] Preferably, the buffer layer is deposited by any one of PVD (physical vapor deposition), PECVD (plasma enhanced chemical vapor deposition) or LPCVD (low pressure chemical vapor deposition).

[0030] Exemplarily, one process in the PVD technology is DC sputtering. The present invention provides a method for depositing a buffer layer using DC sputtering, which specifically includes the following steps:

[0031] Under vacuum conditions, argon gas is introduced, and then the power supply of the target material is turned on to generate glow discharge on the target surface, so that the argon gas is ionized. The argon ions generated by the ionization bombard the target material, thereby sputtering and depositing a buffer layer on the surface to be bonded of the substrate.

[0032] Preferably, the vacuum degree of the vacuum condition is 5×10 -3 ~8×10 -3 Pa, for example, can be 5×10 -3 Pa, 6×10 -3 Pa, 7×10 -3 Pa or 8×10 -3 Pa, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, during the deposition of the buffer layer, the flow rate of the argon gas is 40 to 60 sccm, for example, 40 sccm, 45 sccm, 50 sccm, 55 sccm or 60 sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, during the deposition of the buffer layer, the argon gas is introduced until the vacuum degree reaches 3×10 -2 ~8×10 - 2 Pa, for example, can be 3×10 -2 Pa, 4×10 -2 Pa, 5×10 -2 Pa, 6×10 -2 Pa, 7×10 -2 Pa or 8×10 -2 Pa, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the power supply is a DC power supply, the voltage of the power supply is 300-600V, for example, it can be 300V, 400V or 600V, etc., the power of the power supply is 1100-2000W, for example, it can be 1100W, 1200W, 1500W, 1600W, 1800W or 2000W, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the thickness of the buffer layer is 100-2000 nm, for example, it can be 100 nm, 200 nm, 500 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm or 2000 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the preliminary cleaning in step (2) comprises the following steps: introducing a purge gas into the reaction chamber where the buffer layer is deposited to purge the surface of the buffer layer, and then evacuating the gas.

[0038] Preferably, a purge gas outlet is provided in the reaction chamber, and the purge gas outlet is located above the edge of the buffer layer; the vertical distance between the purge gas outlet and the buffer layer is 2 to 5 mm, for example, it can be 2 mm, 3 mm, 4 mm or 5 mm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the purge gas comprises nitrogen and / or argon.

[0040] Preferably, the flow rate of the purge gas is 2000-4000sccm, for example, it can be 2000sccm, 2200sccm, 2500sccm, 2800sccm, 3000sccm, 3200sccm, 3500sccm, 3800sccm or 4000sccm, etc.; the time for introducing the purge gas is 20-40s, for example, it can be 20s, 25s, 30s, 35s or 40s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] Preferably, during the preliminary cleaning process, the steps of introducing the purge gas and the exhausting gas are cycled 3 to 5 times, for example, 3 times, 4 times or 5 times.

[0042] Preferably, during the oxygen plasma cleaning process, the RF power is 300-500 W, for example, 300 W, 320 W, 350 W, 380 W, 400 W, 420 W, 450 W, 480 W or 500 W, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, the flow rate of oxygen is 500-1000 sccm, for example, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm or 1000 sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the oxygen plasma cleaning time is 30 to 60 seconds, for example, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds or 60 seconds, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, after oxygen plasma cleaning, the radio frequency is kept turned on and a mixed gas of argon and nitrogen is introduced to perform surface passivation.

[0046] In the present invention, when the oxygen plasma cleaning step is performed, the oxygen plasma gas phase material will also clean the surface of the liner to remove organic pollutants on the surface, so that an oxide layer will be formed on the liner, which will affect the adhesion of the next deposited buffer layer film. To solve this problem, the present invention introduces a mixed gas of argon and nitrogen. The nitrogen is converted into nitrogen plasma under the action of radio frequency, which can nitride the oxide layer to form a nitrogen-containing layer, thereby achieving surface passivation and avoiding the next buffer layer deposition from being affected. At the same time, the introduced argon and nitrogen mixed gas can physically clean the surface of the buffer layer, which can further reduce the number of particles in the buffer layer.

[0047] Preferably, during the surface passivation process, the RF power is 1000-1400 W, for example, 1000 W, 1100 W, 1200 W, 1300 W or 1400 W, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] Preferably, the flow rate of the mixed gas of argon and nitrogen is 500-1000sccm, for example, it can be 500sccm, 600sccm, 700sccm, 800sccm, 900sccm or 1000sccm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, in the mixed gas of argon and nitrogen, the volume ratio of argon and nitrogen is (6-9):(1-4), wherein the selection range of argon (6-9) can be, for example, 6, 7, 8 or 9, and the selection range of nitrogen (1-4) can be, for example, 1, 2, 3 or 4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] Preferably, the surface passivation time is 20 to 40 seconds, for example, 20 seconds, 25 seconds, 30 seconds, 35 seconds or 40 seconds, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] In summary, the present invention optimizes the front and back processes of depositing the buffer layer, which include sandblasting, pre-cleaning, preliminary cleaning, oxygen plasma cleaning and surface passivation. With the joint action of these steps, the number of particles with a particle size greater than 0.2 μm in the buffer layer can be less than 50.

[0052] In a second aspect, the present invention provides a composite substrate, which is manufactured by the method described in the first aspect.

[0053] Preferably, the composite substrate comprises two stacked substrates, a buffer layer is provided between the two substrates, and the number of particles with a particle size greater than 0.2 μm in the buffer layer is less than 50 particles.

[0054] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] The present invention pre-cleans the reaction chamber before depositing the buffer layer to remove loose impurity particles in the reaction chamber; after depositing the buffer layer, the surface of the buffer layer is preliminarily cleaned to remove particles that fall on the surface of the buffer layer; after the preliminarily cleaning, the radio frequency is turned on and oxygen is introduced, and the oxygen is converted into oxygen plasma gas phase material under the action of the radio frequency, and the surface of the buffer layer is cleaned by the oxygen plasma gas phase material to remove organic pollutant particles on the surface. In summary, the present invention optimizes the pre- and post-processes of depositing the buffer layer, which can effectively reduce the number of particles in the buffer layer, thereby effectively improving the bonding interface quality of the composite substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic structural diagram of a buffer layer growth device provided in an embodiment of the present invention.

[0058] Figure 2 A schematic diagram of the process of growing a buffer layer and bonding provided in an embodiment of the present invention.

[0059] Among them, 1-reaction chamber; 2-lining plate; 3-high voltage power supply introduced into cathode; 4-target material; 5-substrate electrode; 6-argon gas pipeline; 7-nitrogen gas pipeline; 8-oxygen gas pipeline; 9-exhaust port; 10-first substrate; 11-buffer layer; 12-second substrate. DETAILED DESCRIPTION

[0060] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0061] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0062] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0063] In one embodiment, the present invention provides a buffer layer growth device having a structure as follows: Figure 1 As shown, it includes a reaction chamber 1, in which a lining plate 2 is arranged, and the lining plate 2 is a U-shaped structure, with a horizontal bottom plate and a side plate connected to the horizontal bottom plate; the interior of the lining plate 2 is provided with a high-voltage power supply introduction cathode 3 and a substrate electrode 5 for placing a substrate from top to bottom, and a target material 4 is connected to the bottom surface of the high-voltage power supply introduction cathode 3; the bottom surface of the reaction chamber 1 is provided with a gas exhaust port 9, and the horizontal bottom plate is provided with an opening, and the orthographic projection of the opening on the bottom surface of the reaction chamber 1 is located in the area where the gas exhaust port 9 is located.

[0064] The buffer layer growth device also includes gas pipelines, namely an oxygen pipeline 8 , a nitrogen pipeline 7 and an argon pipeline 6 , and the gas outlets of the oxygen pipeline 8 , the nitrogen pipeline 7 and the argon pipeline 6 are all located inside the liner 2 .

[0065] In one embodiment, the present invention provides a method for improving the quality of a composite substrate bonding interface, the method comprising:

[0066] Two substrates to be bonded are provided, which are respectively referred to as a first substrate 10 and a second substrate 12. A buffer layer 11 is grown on the surface to be bonded of the first substrate 10. Then, the first substrate 10 and the second substrate 12 with the buffer layer 11 grown thereon are bonded to obtain a composite substrate (the process is as follows). Figure 2As shown); wherein, the buffer layer is grown by using the buffer layer growth device provided in the above embodiment, and the specific growth steps include:

[0067] (1) The liner in the reaction chamber is sandblasted.

[0068] (2) Pre-cleaning the reaction chamber, then placing the first substrate on the substrate electrode in the pre-cleaned reaction chamber, and depositing a buffer layer on the surface to be bonded of the first substrate.

[0069] (3) The surface of the deposited buffer layer is preliminarily cleaned, and then the radio frequency is turned on, oxygen is introduced, and oxygen plasma cleaning is performed; thereafter, the radio frequency is kept turned on, and a mixed gas of argon and nitrogen is introduced to perform surface passivation.

[0070] Example 1

[0071] This embodiment provides a method for improving the bonding interface quality of a composite substrate, the method comprising the following steps:

[0072] (1) providing two substrates to be bonded, which are respectively referred to as a first substrate and a second substrate, wherein the first substrate is a silicon substrate and the second substrate is an aluminum nitride substrate; using the buffer layer growth device provided in the above embodiment, growing a SiO2 buffer layer on the surface to be bonded of the first substrate, the specific growth steps are as follows:

[0073] S1. Use abrasives to sandblast the liner in the reaction chamber; wherein the abrasives include SiO2, Al2O3 and Fe, and based on the total mass of the abrasives being 100%, the mass fraction of SiO2 is 80%, the mass fraction of Fe is 0.05%, and the remainder is Al2O3; the particle size of the abrasive is 100 mesh.

[0074] S2. Argon gas is introduced into the reaction chamber at a flow rate of 3000 sccm for 30 seconds, and then the reaction chamber is evacuated. The steps of introducing argon gas and evacuating the gas are repeated 4 times to achieve pre-cleaning of the reaction chamber.

[0075] S3, placing the first substrate on the substrate electrode in the pre-cleaned reaction chamber, first evacuating the chamber to a vacuum of 6.5×10 -3 Pa, and then argon gas is introduced with an argon flow rate of 50 sccm. At this time, the vacuum reaches 5.5×10 -2 Pa, turn on the target power supply, wherein the target material is a silicon dioxide target, the voltage is 400V, the power is 1500W, glow discharge is generated on the target surface, the argon gas is ionized, and the argon ions bombard the target surface under the attraction of the electric field applied by the cathode target material, sputtering the target material atoms, thereby depositing a 500nm thick SiO2 buffer layer on the surface to be bonded of the first substrate.

[0076] S4. Use the outlet of the argon gas pipeline as the purge gas outlet, and introduce purge gas into the reaction chamber where the buffer layer is deposited through the purge gas outlet to purge the surface of the buffer layer, wherein the purge gas outlet is located above the edge of the buffer layer, and the vertical distance between the purge gas outlet and the buffer layer is 3 mm. The purge gas is argon, and the flow rate of argon is 3000 sccm. The time for introducing argon is 30 s; then evacuate the gas; the steps of introducing the purge gas and evacuating the gas are repeated 4 times to achieve preliminary cleaning of the surface of the buffer layer.

[0077] S5. Turn on the radio frequency to set the radio frequency power to 400 W, introduce oxygen with a flow rate of 750 sccm, and perform oxygen plasma cleaning on the surface of the buffer layer and the surface of the liner for 50 seconds.

[0078] S6. Keep the RF on, set the RF power to 400 W, introduce a mixed gas of argon and nitrogen in a volume ratio of 8:2, and a flow rate of 750 sccm for 40 seconds of surface passivation.

[0079] (2) Bonding the first substrate on which the SiO2 buffer layer is grown and the second substrate to obtain a composite substrate.

[0080] Example 2

[0081] This embodiment provides a method for improving the bonding interface quality of a composite substrate, the method comprising the following steps:

[0082] (1) providing two substrates to be bonded, which are respectively referred to as a first substrate and a second substrate, wherein the first substrate is a silicon substrate and the second substrate is a silicon carbide substrate; using the buffer layer growth device provided in the above embodiment to grow a SiO2 buffer layer on the surface to be bonded of the first substrate, the specific growth steps are as follows:

[0083] S1. Use abrasives to sandblast the liner in the reaction chamber; wherein the abrasives include SiO2, Al2O3 and Fe, and based on the total mass of the abrasives being 100%, the mass fraction of SiO2 is 85%, the mass fraction of Fe is 0.04%, and the remainder is Al2O3; the particle size of the abrasive is 120 mesh.

[0084] S2. Nitrogen gas is introduced into the reaction chamber at a flow rate of 2500 sccm for 40 seconds, and then the reaction chamber is evacuated. The steps of introducing nitrogen gas and evacuating the gas are repeated 4 times to achieve pre-cleaning of the reaction chamber and the target.

[0085] S3, placing the first substrate on the substrate electrode in the pre-cleaned reaction chamber, first evacuating the chamber to a vacuum of 6.5×10 -3Pa, and then argon gas is introduced with an argon flow rate of 50 sccm. At this time, the vacuum reaches 5.5×10 -2 Pa, turn on the target power supply, wherein the target material is a silicon dioxide target, the voltage is 400V, the power is 1500W, glow discharge is generated on the target surface, the argon gas is ionized, and the argon ions bombard the target surface under the attraction of the electric field applied by the cathode target material, sputtering the target material atoms, thereby depositing a 500nm thick SiO2 buffer layer on the surface to be bonded of the first substrate.

[0086] S4, using the outlet of the nitrogen pipeline as the purge gas outlet, introducing the purge gas into the reaction chamber where the buffer layer is deposited through the purge gas outlet to purge the surface of the buffer layer, wherein the purge gas outlet is located above the edge of the buffer layer, the vertical distance between the purge gas outlet and the buffer layer is 4 mm, the purge gas is nitrogen, the flow rate of nitrogen is 2500 sccm, and the time for introducing nitrogen is 40 s; then evacuating; the steps of introducing the purge gas and evacuating are repeated 4 times, thereby achieving preliminary cleaning of the surface of the buffer layer;

[0087] S5. Turn on the radio frequency to set the radio frequency power to 450 W, introduce oxygen with a flow rate of 800 sccm, and perform oxygen plasma cleaning on the surface of the buffer layer and the surface of the liner for 40 seconds.

[0088] S6. Keep the RF on, set the RF power to 450 W, introduce a mixed gas of argon and nitrogen in a volume ratio of 8:2, and a flow rate of 800 sccm for 35 seconds of surface passivation.

[0089] (2) Bonding the first substrate on which the SiO2 buffer layer is grown and the second substrate to obtain a composite substrate.

[0090] Example 3

[0091] The difference between this embodiment and embodiment 1 is that step S6 is omitted, that is, the surface passivation step is not performed.

[0092] The remaining steps and parameters remain the same as those in Example 1.

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 1 is that step S1, step S5 and step S6 are omitted, that is, the sandblasting, oxygen plasma cleaning and surface passivation steps are not performed.

[0095] The remaining steps and parameters remain the same as those in Example 1.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that step S4 and step S5 are omitted, that is, the preliminary cleaning of the buffer layer surface and the oxygen plasma cleaning steps are not performed.

[0098] The remaining steps and parameters remain the same as those in Example 1.

[0099] Test: A defect tester was used to perform particle tests on the SiO2 buffer layers finally grown in the above-mentioned embodiment and comparative example.

[0100] The test results are shown in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] analyze:

[0105] It can be seen from Example 1 and Example 2 that the present invention optimizes the front and back processes of depositing the buffer layer. Under the joint action of sandblasting, pre-cleaning, preliminary cleaning, oxygen plasma cleaning and surface passivation, the number of particles in the buffer layer can be effectively reduced, and the number of particles with a particle size greater than 0.2 μm in the buffer layer can be achieved to be less than 50 particles, thereby effectively improving the bonding interface quality of the composite substrate.

[0106] It can be seen from Examples 1 and 3 that if the surface passivation step is not performed, the first deposition of the buffer layer is not affected, and the number of particles is less than 50; however, after being recycled for 3 times, the number of particles will be greater than 10,000.

[0107] It can be seen from Example 1 and Comparative Example 1 that if sandblasting, oxygen plasma cleaning and surface passivation steps are not performed, when depositing the buffer layer, the material sputtered on the liner has poor bonding with the liner, resulting in excessive particles in the chamber, causing the number of particles in the buffer layer to be greater than 10,000, which is not conducive to bonding.

[0108] It can be seen from Example 1 and Comparative Example 2 that if the preliminary cleaning and oxygen plasma cleaning steps of the buffer layer surface are not performed, the number of particles in the buffer layer will be too large, which is not conducive to bonding.

[0109] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for improving the bonding interface quality of a composite substrate, characterized in that: The method comprises: Providing two substrates to be bonded, growing a buffer layer on the bonding surface of at least one of the two substrates, and then bonding them to obtain a composite substrate; The method for growing the buffer layer comprises the following steps: (1) pre-cleaning the reaction chamber, then placing the substrate in the pre-cleaned reaction chamber, and depositing a buffer layer on the surface to be bonded of the substrate; (2) Preliminary cleaning is performed on the surface of the deposited buffer layer, and then the radio frequency is turned on and oxygen is introduced to perform oxygen plasma cleaning.

2. The method according to claim 1, characterized in that: The two substrates to be bonded independently include any one of a silicon substrate, an aluminum nitride substrate, a silicon carbide substrate, a polysilicon-on-silicon substrate, a lithium niobate substrate or a lithium tantalate substrate, or a combination of at least two thereof; Preferably, the material of the buffer layer includes any one of aluminum oxide, silicon dioxide or silicon nitride, or a combination of at least two of them.

3. The method according to claim 1 or 2, characterized in that: In step (1), before the pre-cleaning, the liner in the reaction chamber is sandblasted; Preferably, the abrasive used in the sandblasting process includes SiO2, Al2O3 and Fe; Preferably, the mass fraction of SiO2 is 70-90% based on the total mass of the abrasive used in the sandblasting process as 100%; Preferably, based on the total mass of the abrasive used in the sandblasting process being 100%, the mass fraction of Al2O3 is 10 to 30%; Preferably, based on the total mass of the abrasive used in the sandblasting process being 100%, the mass fraction of Fe is 0.04 to 0.06%; Preferably, the particle size of the abrasive used in the sandblasting process is 5 to 200 meshes.

4. The method according to any one of claims 1 to 3, characterized in that: In step (1), the pre-cleaning comprises the following steps: introducing a cleaning gas into the reaction chamber and then evacuating the gas; Preferably, the cleaning gas comprises nitrogen and / or argon; Preferably, the flow rate of the cleaning gas is 2000-4000 sccm; the time for passing the cleaning gas is 20-40s; Preferably, during the pre-cleaning process, the steps of introducing the cleaning gas and exhausting the gas are cycled 3 to 5 times.

5. The method according to any one of claims 1 to 4, characterized in that: The buffer layer may be deposited by any one of PVD, PECVD or LPCVD.

6. The method according to any one of claims 1 to 5, characterized in that: The preliminary cleaning in step (2) comprises the following steps: introducing a purge gas into the reaction chamber where the buffer layer is deposited to purge the surface of the buffer layer, and then evacuating the gas; Preferably, a purge gas outlet is provided in the reaction chamber, and the purge gas outlet is located above the edge of the buffer layer; the vertical distance between the purge gas outlet and the buffer layer is 2 to 5 mm; Preferably, the purge gas comprises nitrogen and / or argon; Preferably, the flow rate of the purge gas is 2000-4000 sccm; the time for passing the purge gas is 20-40s; Preferably, during the preliminary cleaning process, the steps of introducing the purge gas and the exhausting gas are cycled 3 to 5 times.

7. The method according to any one of claims 1 to 6, characterized in that: During the oxygen plasma cleaning process, the power of the radio frequency is 300 to 500 W; Preferably, the flow rate of the oxygen is 500 to 1000 sccm; Preferably, the oxygen plasma cleaning time is 30 to 60 seconds.

8. The method according to any one of claims 1 to 7, characterized in that: After oxygen plasma cleaning, keep the RF on and introduce a mixture of argon and nitrogen to passivate the surface; Preferably, during the surface passivation process, the radio frequency power is 1000-1400W; Preferably, the flow rate of the mixed gas of argon and nitrogen is 500 to 1000 sccm; Preferably, in the mixed gas of argon and nitrogen, the volume ratio of argon and nitrogen is (6-9):(1-4); Preferably, the surface passivation time is 20 to 40 seconds.

9. A composite substrate, characterized in that: The composite substrate is prepared by the method according to any one of claims 1 to 8.

10. The composite substrate according to claim 9, characterized in that The composite substrate comprises two stacked substrates, a buffer layer is arranged between the two substrates, and the number of particles with a particle size greater than 0.2 μm in the buffer layer is less than 50 particles.

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