A method for thinning a semiconductor structure

Abstract

The present invention relates to a method for thinning a semiconductor structure. The method for thinning a semiconductor structure comprises: providing a semiconductor structure; the semiconductor structure comprises a front side and a back side to be thinned; providing a first substrate; bonding the front side of the semiconductor structure to one side of the first substrate, and thinning the back side of the semiconductor structure; providing a second substrate, wherein the second substrate has a first adsorption hole; arranging a buffer film on one side surface of the second substrate, wherein the buffer film has a second adsorption hole; using the second substrate to adsorb the semiconductor structure from one side of the buffer film; in the adsorption state, the first adsorption hole and the second adsorption hole are at least partially connected; and debonding the front side of the semiconductor structure from the first substrate. The method for thinning a semiconductor structure provided by the present invention can reduce defects and scratches that occur in the semiconductor structure during the debonding process.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for thinning a semiconductor structure. Background Art

[0002] During the wafer processing process of chip manufacturing, in order to prevent the wafer from being damaged during processing, the wafer needs to have a thicker thickness to maintain a certain mechanical strength. For III-V compound semiconductor wafers, the thickness is generally 350μm~700μm. After the wafer processing is completed, in order to facilitate cutting or cleavage into small individual chips, the wafer needs to be thinned to about 100μm to reduce its mechanical strength. However, the lower mechanical strength can easily cause the wafer to break during the thinning process. Therefore, during the thinning process of III-V compound semiconductor wafers, the front side of the wafer needs to be attached to a hard substrate, which is called bonding. Then put it into a fixture, grind it with standard grinding equipment, and polish it with standard polishing equipment. After polishing, the back of the wafer is very smooth without obvious defects and scratches. Finally, the wafer needs to be separated from the hard substrate, which is called debonding. The debonding process is to adsorb the back of the wafer on another hard substrate, which has a porous structure and is relatively rough. After that, the bonded adhesive layer is melted by heating, and then the hard substrate on the front of the wafer is pushed and pulled by external force to separate it from the hard substrate on the front. During the pushing and pulling process, the smooth back of the wafer will inevitably rub against the rough hard substrate. Since III-V wafers are relatively soft, this process will more easily cause more scratches and defects on the back of the wafer, resulting in a reduction in process yield. Therefore, a buffer film with lower hardness is set on the surface of the hard substrate. The superimposed porosity of the second substrate and the buffer film will affect the fixation of the semiconductor structure by the vacuum system, and will also affect the surface roughness of the buffer film. If the porosity is too small, the vacuum system will not be able to effectively fix the semiconductor structure. If the porosity is too large, the surface roughness of the buffer film will increase, which will scratch the semiconductor structure.

[0003] Therefore, a method for thinning a semiconductor structure is needed to protect the back side of the semiconductor structure during the debonding process, thereby reducing defects and scratches on the semiconductor structure during the debonding process. Summary of the invention

[0004] Therefore, the present invention provides a method for thinning a semiconductor structure to solve the problem in the prior art that defects and scratches are easily generated in the semiconductor structure after debonding during the thinning process.

[0005] The present invention provides a method for thinning a semiconductor structure, comprising:

[0006] Providing a semiconductor structure; the semiconductor structure comprises a front side and a back side to be thinned;

[0007] Providing a first substrate; bonding the front side of the semiconductor structure to one side of the first substrate, and thinning the back side of the semiconductor structure;

[0008] Providing a second substrate, wherein the second substrate has a first adsorption hole; disposing a buffer film on one side surface of the second substrate, wherein the buffer film has a second adsorption hole;

[0009] Adsorbing the semiconductor structure from one side of the buffer film using the second substrate; in the adsorbed state, the first adsorption hole and the second adsorption hole are at least partially connected;

[0010] The front side of the semiconductor structure is debonded from the first substrate.

[0011] Optionally, the step of using the second substrate to absorb the semiconductor structure from one side of the buffer film includes:

[0012] A vacuum adsorption unit is disposed on a side of the second substrate facing away from the buffer film. The vacuum adsorption unit evacuates air through the first adsorption holes and the second adsorption holes to provide negative pressure, so that the semiconductor structure is adsorbed and fixed by the second substrate.

[0013] Optionally, the buffer film includes a buffer main body film and a support film;

[0014] In the step of providing a buffer film on one side surface of the second substrate, the support film is located between the buffer main film and the second substrate; the buffer main film is located on a side of the support film facing away from the second substrate.

[0015] Optionally, the melting point of the buffer film material is 150° C. to 400° C.;

[0016] The thickness of the buffer film is 120 μm to 130 μm;

[0017] The thickness of the buffer main film is 15 μm to 20 μm, and the thickness of the support film is 105 μm to 110 μm;

[0018] The material of the buffer main body film includes polytetrafluoroethylene, polyethersulfone or expanded polytetrafluoroethylene.

[0019] Optionally, the overlapping porosity between the second substrate and the buffer film is greater than 21.5%.

[0020] Optionally, the porosity of the second substrate is 34.6% to 45.0%;

[0021] The porosity of the buffer film is 62.0% to 64.9%;

[0022] The pore size of the first adsorption hole is 10.7 μm to 15 μm; the pore size of the second adsorption hole is 1 μm to 3 μm;

[0023] The surface roughness of a side of the buffer film in contact with the semiconductor structure is less than 478 nm.

[0024] Optionally, the superposition porosity between the second substrate and the buffer film is 28.1%;

[0025] The porosity of the second substrate is 45.1%;

[0026] The porosity of the buffer film is 62.3%;

[0027] The pore size of the first adsorption hole is 11.7 μm; the pore size of the second adsorption hole is 1 μm;

[0028] The surface roughness of the side of the buffer film in contact with the semiconductor structure is 396 nm.

[0029] Optionally, before the step of bonding the front surface of the semiconductor structure to one side of the first substrate, the method further includes:

[0030] forming an adhesive layer on the front surface of the semiconductor structure, or forming an adhesive layer on a surface of the first substrate facing the semiconductor structure;

[0031] After the front surface of the semiconductor structure is bonded to one side of the first substrate, the adhesive layer is located between the first substrate and the front surface of the semiconductor structure.

[0032] Optionally, the step of debonding the front surface of the semiconductor structure from the first substrate includes:

[0033] The adhesive layer is heated and an external force is applied to separate the front surface of the semiconductor structure from the first substrate.

[0034] Optionally, after the step of debonding the front surface of the semiconductor structure from the first substrate, the method further includes:

[0035] separating the second substrate from the buffer film, and removing the second substrate;

[0036] Removing the buffer film by a solution immersion process;

[0037] The adhesive layer is removed by a solution soaking process.

[0038] The technical solution of the present invention has the following advantages:

[0039] (1) The semiconductor structure thinning method provided by the present invention, after thinning the back side of the semiconductor structure, places the semiconductor structure on the surface of the buffer film and is adsorbed by the second substrate, and then debonds the front side of the semiconductor structure from the first substrate, thereby avoiding direct contact between the back side of the semiconductor and the second substrate during the debonding process; in the process of pushing and pulling the first substrate, the buffer film protects the back side of the semiconductor structure, thereby reducing defects and scratches on the semiconductor structure during the debonding process.

[0040] (2) In the semiconductor structure thinning method provided by the present invention, since the second adsorption holes of the buffer film and the first adsorption holes of the second substrate have good connectivity, sufficient negative pressure is provided to adsorb the semiconductor structure, thereby avoiding relative sliding during the debonding process that may cause damage to the semiconductor structure.

[0041] (3) In the semiconductor structure thinning method provided by the present invention, the optimal range of technical parameter values ​​in the debonding process is specified, including the stacking porosity between the buffer film and the second substrate being greater than 21.5%, the surface roughness of the buffer film being less than 478nm, and the aperture of the second adsorption hole of the buffer film being 1μm to 3μm. Within these ranges, the vacuum adsorption capability of the semiconductor structure can be improved, the mutual friction between the semiconductor structure and the buffer film can be reduced, and the second substrate can firmly adsorb the semiconductor structure, thereby protecting the semiconductor structure from damage during the debonding process between the semiconductor structure and the first substrate.

[0042] (4) In the semiconductor structure thinning method provided by the present invention, the buffer film material can withstand high temperatures of 150°C to 400°C, which basically covers the melting point temperature of the bonding glue or bonding wax commonly used in the market. During the debonding process, the decomposition or denaturation of the buffer film itself is avoided to contaminate the semiconductor structure.

[0043] (5) In the semiconductor structure thinning method provided by the present invention, the buffer film is an organic material of polytetrafluoroethylene, polyethersulfone or expanded polytetrafluoroethylene. Since the back side of the semiconductor structure is relatively soft, and polytetrafluoroethylene, polyethersulfone or expanded polytetrafluoroethylene, as a high molecular polymer material, has the characteristics of low hardness, strong plasticity and high ductility, adding a buffer film between the second substrate and the semiconductor structure can reduce scratches on the metal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 A schematic flow chart of a method for thinning a semiconductor structure according to an embodiment of the present invention;

[0046] Figure 2 A schematic diagram of a specific process of a semiconductor structure thinning method according to an embodiment of the present invention;

[0047] Figure 3-Figure 9 A schematic structural diagram of each step of a semiconductor structure thinning method according to an embodiment of the present invention;

[0048] Fig.10 and Fig.11 The relevant experimental data provided for Comparative Example 1 of the present invention;

[0049] Fig.12 This is a surface morphology of the semiconductor structure after thinning under the condition of superimposed porosity of 27.9% in Comparative Example 2 of the present invention;

[0050] Fig.13 and Fig.14 This is a surface morphology of the semiconductor structure after thinning under the conditions that the surface roughness of the buffer film is 843nm and 1429nm in Comparative Example 3 of the present invention.

[0051] Description of reference numerals:

[0052] 1-semiconductor structure; 2-adhesive layer; 3-first substrate; 4-support film; 5-buffer main film; 6-buffer film; 7-second substrate. DETAILED DESCRIPTION

[0053] In order to solve the problem in the prior art that semiconductor structures are prone to defects and scratches after debonding during the thinning process, the present invention provides a method for thinning a semiconductor structure, comprising: providing a semiconductor structure; the semiconductor structure comprising a front side and a back side to be thinned; providing a first substrate; bonding the front side of the semiconductor structure to one side of the first substrate, and thinning the back side of the semiconductor structure; providing a second substrate, wherein the second substrate has a first adsorption hole; providing a buffer film on one side surface of the second substrate, wherein the buffer film has a second adsorption hole; using the second substrate to adsorb the semiconductor structure from one side of the buffer film; in the adsorption state, the first adsorption hole and the second adsorption hole are at least partially connected; and debonding the front side of the semiconductor structure from the first substrate.

[0054] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0055] Example 1

[0056] like Figure 1 As shown, this embodiment provides a method for thinning a semiconductor structure, including steps S101-S105.

[0057] S101, providing a semiconductor structure; the semiconductor structure comprises a front side and a back side to be thinned.

[0058] In a specific implementation, the semiconductor structure may be a wafer, such as a III-V compound semiconductor wafer. The thickness of the semiconductor structure is 350 μm to 700 μm, such as 350 μm, 500 μm, 600 μm, 700 μm, etc. The semiconductor structure is thicker before thinning to maintain a certain mechanical strength.

[0059] S102, providing a first substrate; bonding the front side of the semiconductor structure to one side of the first substrate, and thinning the back side of the semiconductor structure.

[0060] In specific implementation, the first substrate may be sapphire, silicon carbide, etc. In one embodiment, the semiconductor structure is thinned to 90 μm to 110 μm, such as 90 μm, 95 μm, 100 μm, etc. The process of thinning the back side of the semiconductor structure includes mechanical grinding and chemical polishing.

[0061] S103, providing a second substrate, wherein the second substrate has first adsorption holes; and disposing a buffer film on one side surface of the second substrate, wherein the buffer film has second adsorption holes.

[0062] S104, using the second substrate to adsorb the semiconductor structure from one side of the buffer film; in the adsorbed state, the first adsorption hole and the second adsorption hole are at least partially connected.

[0063] S105 , debonding the front side of the semiconductor structure from the first substrate.

[0064] In a specific implementation, after the semiconductor structure is placed on a surface of the buffer film facing away from the second substrate and adsorbed by the second substrate, the front surface of the semiconductor structure is debonded from the first substrate.

[0065] The semiconductor structure thinning method provided in an embodiment of the present invention thins the back side of the semiconductor structure, places the semiconductor structure on the surface of a buffer film and is adsorbed by a second substrate, and then debonds the front side of the semiconductor structure from the first substrate, thereby avoiding direct contact between the back side of the semiconductor and the second substrate during the debonding process; in the process of pushing and pulling the first substrate, the buffer film protects the back side of the semiconductor structure, thereby reducing defects and scratches on the semiconductor structure during the debonding process.

[0066] Furthermore, in some embodiments, the step of using the second substrate to absorb the semiconductor structure from one side of the buffer film includes:

[0067] A vacuum adsorption unit is disposed on a side of the second substrate facing away from the buffer film. The vacuum adsorption unit evacuates air through the first adsorption holes and the second adsorption holes to provide negative pressure, so that the semiconductor structure is adsorbed and fixed by the second substrate.

[0068] In specific implementation, since the second adsorption holes of the buffer film and the first adsorption holes of the second substrate have good connectivity, the vacuum adsorption unit provides sufficient negative pressure to firmly adsorb the semiconductor structure, thereby avoiding damage to the semiconductor structure caused by relative sliding during the debonding process.

[0069] Further, in some embodiments, the buffer film includes a buffer body film and a support film;

[0070] In the step of providing a buffer film on one side surface of the second substrate, the support film is located between the buffer main film and the second substrate; the buffer main film is located on a side of the support film facing away from the second substrate.

[0071] In a specific implementation, the buffer film includes a buffer main film and a support film, wherein the buffer main film covers the surface of the support film, wherein the main film is relatively thin, with a thickness of 15μm to 20μm, such as 15μm, 18μm, 20μm, etc.; the support film is relatively thick, with a thickness of 105μm to 110μm, such as 105μm, 108μm, 110μm, etc. The second adsorption hole penetrates both the buffer main film and the support film, and the surface of the main film directly contacts the back of the wafer during the debonding process.

[0072] Further, in some embodiments, the melting point of the buffer film material is 150°C to 400°C;

[0073] The thickness of the buffer film is 120 μm to 130 μm, for example, 120 μm, 125 μm, 130 μm;

[0074] The thickness of the buffer main film is 15 μm to 20 μm, for example, 15 μm, 18 μm, 20 μm; the thickness of the support film is 105 μm to 110 μm, for example, 105 μm, 107 μm, 110 μm;

[0075] The material of the buffer main body film includes polytetrafluoroethylene, polyethersulfone or expanded polytetrafluoroethylene.

[0076] In specific implementation, since the buffer film material can withstand high temperatures of 150°C to 400°C, which basically covers the melting point temperature of commonly used bonding glues or bonding waxes on the market, during the debonding process, the decomposition or denaturation of the buffer film itself is avoided to contaminate the semiconductor structure.

[0077] In some embodiments, the material of the buffer main film includes polytetrafluoroethylene, polyethersulfone or expanded polytetrafluoroethylene. Since the back of the semiconductor structure is generally Ti-Pt-Au alloy, it is relatively soft (Mohs hardness is only 2.5-3). Polytetrafluoroethylene, polyethersulfone or expanded polytetrafluoroethylene, as a high molecular polymer material, has the characteristics of low hardness, strong plasticity and high ductility. Adding a buffer film between the second substrate and the semiconductor structure can reduce scratches on the metal surface.

[0078] In one example, the buffer film has a thickness of 130 μm, the buffer main film has a thickness of 20 μm, and the support film has a thickness of 110 μm.

[0079] In addition, the diameter of the buffer film is generally selected according to the size of the semiconductor structure. For example, if the diameter of the semiconductor structure is 6 inches, the diameter of the buffer film is 150 mm.

[0080] Furthermore, in some embodiments, the superimposed porosity between the first adsorption pores and the second adsorption pores is greater than 21.5%.

[0081] In a specific implementation, the superposition porosity between the second substrate and the buffer film = the buffer film porosity × the second substrate porosity. When the superposition porosity is greater than 21.5%, the second adsorption hole and the first adsorption hole have good connectivity, which can improve the ability of the semiconductor structure to absorb vacuum, so that the second substrate can firmly absorb the semiconductor structure, avoiding relative sliding during the debonding process and causing damage to the semiconductor structure.

[0082] Further, in some embodiments, the porosity of the second substrate is 34.6% to 45.0%;

[0083] The porosity of the buffer film is 62.0% to 64.9%;

[0084] The pore size of the first adsorption hole is 10.7 μm to 15 μm; the pore size of the second adsorption hole is 1 μm to 3 μm;

[0085] The surface roughness of a side of the buffer film in contact with the semiconductor structure is less than 478 nm.

[0086] In a specific implementation, when the surface roughness of the buffer film is less than 478 nm and the pore size of the second adsorption hole of the buffer film is 1 μm to 3 μm, the mutual friction between the semiconductor structure and the buffer film can be reduced, so that the second substrate can firmly adsorb the semiconductor structure, thereby protecting the semiconductor structure from damage during the debonding process of the semiconductor structure and the first substrate.

[0087] Further, in some embodiments, the stacking porosity between the second substrate and the buffer film is 28.1%;

[0088] The porosity of the second substrate is 45.1%;

[0089] The porosity of the buffer film is 62.3%;

[0090] The pore size of the first adsorption hole is 11.7 μm; the pore size of the second adsorption hole is 1 μm;

[0091] The surface roughness of the side of the buffer film in contact with the semiconductor structure is 396 nm.

[0092] Furthermore, in some embodiments, before the step of bonding the front surface of the semiconductor structure to one side of the first substrate, the step further includes:

[0093] forming an adhesive layer on the front surface of the semiconductor structure, or forming an adhesive layer on a surface of the first substrate facing the semiconductor structure;

[0094] After the front surface of the semiconductor structure is bonded to one side of the first substrate, the adhesive layer is located between the first substrate and the front surface of the semiconductor structure.

[0095] Further, in some embodiments, the step of debonding the front surface of the semiconductor structure from the first substrate includes:

[0096] The adhesive layer is heated and an external force is applied to separate the front surface of the semiconductor structure from the first substrate.

[0097] In a specific implementation, during the process of pushing and pulling the first substrate, the buffer film protects the back surface of the semiconductor structure, thereby reducing defects and scratches on the semiconductor structure during the debonding process.

[0098] In one embodiment, during the process of debonding the front side of the semiconductor structure from the first substrate, the adhesive layer is heated to 150±3° C., and an external force is applied by a push arm to horizontally push the first substrate to separate the semiconductor structure from the first substrate.

[0099] Furthermore, in some embodiments, after the step of debonding the front surface of the semiconductor structure from the first substrate, the method further includes:

[0100] separating the second substrate from the buffer film, and removing the second substrate;

[0101] Removing the buffer film by a solution immersion process;

[0102] The adhesive layer is removed by a solution soaking process.

[0103] In a specific implementation, by closing the vacuum adsorption unit and the negative pressure, the second substrate no longer adsorbs the semiconductor structure, so that the semiconductor structure can be separated from the second substrate.

[0104] In some embodiments, in the step of removing the buffer film by a solution immersion process, the buffer film and the semiconductor structure can be placed in a standard basket with an organic solution for heating and immersion to separate the buffer film from the semiconductor structure. The temperature of the organic solution is 20° C. to 26° C., and the organic solution can be an acetone solution.

[0105] In the step of removing the adhesive layer by solution soaking process, the adhesive layer can be removed by first soaking in 45°C~50°C acetone solution for 30 minutes, then soaking in 35~40°C isopropanol for 15 minutes, and finally soaking in pure water overflow for 5 minutes.

[0106] Example 2

[0107] refer to Figure 2 This embodiment provides a specific process of a semiconductor structure thinning method, including steps S201-S209.

[0108] S201, providing a semiconductor structure 1; the semiconductor structure 1 comprises a front surface and a back surface to be thinned. The thickness of the semiconductor structure before thinning is 700 μm.

[0109] S202 , providing a first substrate 3 ; forming an adhesive layer 2 on the front surface of the semiconductor structure 1 , or forming an adhesive layer 2 on a surface of the first substrate facing the semiconductor structure 1 .

[0110] S203, bonding the front side of the semiconductor structure 1 to one side of the first substrate 3, thinning the back side of the semiconductor structure 1, and the adhesive layer 2 is located between the first substrate 3 and the front side of the semiconductor structure 1. Figure 3 The semiconductor structure 1 is thinned by mechanical grinding and chemical polishing, and the thickness of the semiconductor structure 1 after thinning is 100 μm. Figure 4 shown.

[0111] S204, providing a second substrate 7, wherein the second substrate 7 has a first adsorption hole; disposing a buffer film 6 on one side surface of the second substrate 7, wherein the buffer film 6 has a second adsorption hole; the buffer film 6 comprises a buffer main body film 5 and a support film 4, wherein the support film 4 is located between the buffer main body film 5 and the second substrate 7, and the buffer main body film 5 is located on the side of the support film 4 facing away from the second substrate 7, such as Figure 5 shown.

[0112] Among them, the material of the second substrate 7 is microporous SiC material, the porosity of the second substrate 7 is 45.1%, the aperture of the first adsorption hole is 11.7μm, the diameter of the second substrate 7 is 156mm, and the thickness is 950μm. The material of the buffer main film 5 is polytetrafluoroethylene, the thickness of the buffer film 6 is 0.13mm, the porosity of the buffer film 6 is 62.3%, the aperture of the second adsorption hole is 1μm, and the surface roughness of the side of the buffer film 6 in contact with the semiconductor structure 1 is 396nm.

[0113] S205, a vacuum adsorption unit is provided on the side of the second substrate 7 facing away from the buffer film 6, and the vacuum adsorption unit evacuates air through the first adsorption hole and the second adsorption hole to provide negative pressure, so that the semiconductor structure 1 is adsorbed and fixed by the second substrate 7. Figure 6 As shown; in the adsorption state, the first adsorption hole and the second adsorption hole are at least partially connected.

[0114] S206, heating the adhesive layer 2 and applying external force to separate the front surface of the semiconductor structure 1 from the first substrate 3. In the process of debonding the front surface of the semiconductor structure 1 from the first substrate 3, the adhesive layer 2 is heated to 150±3°C, and an external force is applied by a film pusher arm to horizontally push the first substrate 3 to separate the semiconductor structure 1 from the first substrate 3. Figure 7 During the separation of the semiconductor structure 1 from the first substrate 3 , the buffer film 6 protects the back surface of the semiconductor structure 1 , thereby reducing defects and scratches on the semiconductor structure 1 during the debonding process.

[0115] S207, separating the second substrate 7 from the buffer film 6, and removing the second substrate 7. Figure 8 As shown, the vacuum adsorption unit is turned off, the negative pressure is turned off, and the second substrate 7 no longer adsorbs the semiconductor structure 1 , so that the semiconductor structure 1 can be separated from the second substrate 7 .

[0116] S208, removing the buffer film 6 by using a solution immersion process. The buffer film 6 and the semiconductor structure 1 are placed in a standard basket with acetone solution for heating and immersion to separate the buffer film 6 from the semiconductor structure 1. The temperature of the acetone solution is 20°C to 26°C.

[0117] S209, removing the adhesive layer 2 by using a solution soaking process: first soaking in 45°C-50°C acetone solution for 30 minutes, then soaking in 35°C-40°C isopropanol for 15 minutes, and finally soaking in pure water overflow for 5 minutes to remove the adhesive layer 2.

[0118] In addition, the present invention also provides comparative examples 1 to 3. Comparative example 1 compares the scratching of the semiconductor structure by the porosity and roughness of the hard substrate without a buffer film; comparative example 2 determines the optimal range of the stacking porosity that can effectively fix the semiconductor; and comparative example 3 determines the appropriate roughness of the buffer film to reduce the impact on the debonding scratch.

[0119] Comparative Example 1

[0120] The difference between Comparative Example 1 and Example 2 is that no buffer film is provided during the implementation process, and the other steps are the same. Comparative Example 1 selects six SIC substrates with different porosities for debonding, in order to observe the effect of the porosity and roughness of the hard substrate on the scratching of the semiconductor structure.

[0121] refer to Fig. 9 , which is different from Example 2, is that Example 1 does not provide a buffer film 6, the back of the semiconductor structure is directly in contact with the second substrate, the second substrate is made of microporous SIC material, and six SIC substrates with different porosities are selected. The SIC substrates used are double-sided polished, and the porosities are 13.3%, 18.0%, 22.5%, 34.7%, 41.2%, and 45.0%, respectively. The scratch sizes at nine points of the semiconductor structure are counted from left to right and the average value is calculated. Fig.10 The average scratch size of the semiconductor structure shows a trend of first decreasing and then increasing with the increase of the porosity of the SIC substrate. The corresponding semiconductor scratch width is 17.6μm when the porosity is 13.3%. When the porosity increases to 22.5%, the average scratch width of the semiconductor structure decreases to 5.6μm. As the porosity increases to 45.0%, the scratch width rises again to 22.5μm.

[0122] According to the experimental results, the porosity of the second substrate will seriously affect the adsorption of the vacuum system on the semiconductor. The reduced porosity leads to the deterioration of the penetration of the second substrate. The vacuum system cannot effectively fix the semiconductor structure through the micropores of the SiC substrate. The external force of heating and debonding causes relative movement between the second substrate and the semiconductor structure. The friction between the second substrate and the semiconductor structure scratches the back of the semiconductor structure.

[0123] Increasing the porosity of the second substrate is beneficial to the fixation of the semiconductor structure by the vacuum system, but the increase in porosity will increase the roughness of the surface of the second substrate. Fig.11 The surface roughness of the second substrate increases with the increase of porosity, which causes more serious scratches on the semiconductor structure in contact. Fig.10 By adjusting the porosity of the second substrate, the damage to the semiconductor structure can be reduced but it cannot be completely eliminated.

[0124] Comparative Example 2

[0125] The difference between Comparative Example 2 and Example 2 is that a buffer film with the smallest roughness is provided, the porosity of the buffer film is 62.3%, and the pore size is 1 μm. Comparative Example 2 selects six SIC substrates with different porosities for debonding, in order to determine the optimal range of superimposed porosities that can effectively fix the semiconductor. The other steps are the same.

[0126] Six SIC substrates with different porosities were selected respectively. The SIC substrates used were double-sided polished, and the porosities were 13.3%, 18.0%, 22.5%, 34.7%, 41.2%, and 45.0%, respectively. A buffer film was set on the second substrate. The pore size of the buffer film was 1.00μm, and the porosity was 62.3%. The porosities after superimposing with the six SiC substrates were 8.2%, 11.2%, 14.0%, 21.5%, 25.5%, and 27.9%, respectively. Superimposed porosity = porosity of second substrate × porosity of buffer film. When the superimposed porosity was 8.2%, 11.2%, and 14%, the average scratch sizes were 6.6μm, 6.4μm, and 4.8μm, respectively. However, the scratches completely disappeared when the superimposed porosity reached more than 21.5%. For example, Fig.12 The surface morphology is shown when the superposition porosity is 27.9%. According to the experimental results, when the superposition porosity of the second substrate and the buffer film is greater than 21.5% during the debonding process, scratches on the semiconductor structure can be completely avoided.

[0127] Comparative Example 3

[0128] The difference between Comparative Example 3 and Example 2 is that a SiC substrate with a porosity of 45.0% is selected as the second substrate, and six buffer films with different roughness are selected, in order to select a suitable roughness to reduce the impact on debonding scratches. The other steps are the same.

[0129] The same semiconductor structure and thinning and polishing method as in Example 2 were selected, and a SiC substrate with a porosity of 45.0% was selected as the second substrate to ensure that the porosity after superposition was large enough to ensure that the semiconductor structure could be effectively fixed. Buffer films with pore sizes of 1.00μm, 3.00μm, 5.00μm, and 10.00μm were selected, and the surface roughness was 396nm, 478nm, 843nm, and 1429nm, respectively. The effect of roughness on debonding scratches was studied by comparison. The porosities after superposition were 27.9%, 29.2%, 31.2%, and 33.2%, respectively. The results showed that the buffer films with a roughness of 396nm and 478nm did not scratch the semiconductor structure after debonding. Under the conditions of the buffer film roughness of 843nm and 1429nm, the sizes of scratches on the surface of the semiconductor structure after debonding were 4.5μm and 6.4μm, respectively. Fig.13 and Fig.14 The surface morphologies of the buffer films after debonding are 843nm and 1429nm respectively. Fig.13 When the roughness of the buffer film is 843nm, a scratch with a width of 4.5μm is generated on the surface of the semiconductor structure after debonding; according to Fig.14 When the roughness of the buffer film is 1429nm, a scratch with a width of 6.4μm is generated on the surface of the semiconductor structure after debonding. According to the experimental results, during the debonding process, the surface roughness of the buffer film is ≤478nm, the pore size of the buffer film is 1μm~3μm, and the porosity of the buffer film is 62.0%~64.9% to completely avoid scratching the semiconductor structure.

[0130] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for thinning a semiconductor structure, It is characterized in that include: Providing a semiconductor structure; The semiconductor structure comprises a front side and a back side to be thinned; providing a first substrate; Bonding the front side of the semiconductor structure to one side of the first substrate, and thinning the back side of the semiconductor structure; Providing a second substrate, wherein the second substrate has a plurality of first adsorption holes; A buffer film is disposed on one side surface of the second substrate, wherein the buffer film has a plurality of second adsorption holes; Adsorbing the semiconductor structure from one side of the buffer film using the second substrate; in the adsorbed state, the first adsorption hole and the second adsorption hole are at least partially connected; debonding the front side of the semiconductor structure from the first substrate; Wherein, the stacking porosity between the second substrate and the buffer film is greater than 21.5%; The porosity of the second substrate is 34.6% to 46.0%; The porosity of the buffer film is 62.0% to 64.9%; The pore size of the first adsorption hole is 10.7 μm to 15 μm; the pore size of the second adsorption hole is 1 μm to 3 μm; The surface roughness of a side of the buffer film in contact with the semiconductor structure is less than 478 nm.

2. The method for thinning a semiconductor structure according to claim 1, It is characterized in that The step of using the second substrate to absorb the semiconductor structure from one side of the buffer film comprises: A vacuum adsorption unit is disposed on a side of the second substrate facing away from the buffer film. The vacuum adsorption unit evacuates air through the first adsorption holes and the second adsorption holes to provide negative pressure, so that the semiconductor structure is adsorbed and fixed by the second substrate.

3. The method for thinning a semiconductor structure according to claim 2, It is characterized in that The buffer film comprises a buffer main body film and a support film; In the step of providing a buffer film on one side surface of the second substrate, the support film is located between the buffer main film and the second substrate; the buffer main film is located on a side of the support film facing away from the second substrate.

4. The method for thinning a semiconductor structure according to claim 3, It is characterized in that The melting point of the buffer film material is 150°C to 400°C; The thickness of the buffer film is 120 μm to 130 μm; The thickness of the buffer main film is 15 μm to 20 μm, and the thickness of the support film is 105 μm to 110 μm; The material of the buffer main body film includes polytetrafluoroethylene, polyethersulfone or expanded polytetrafluoroethylene.

5. The method for thinning a semiconductor structure according to claim 1, It is characterized in that The stacking porosity between the second substrate and the buffer film is 28.1%; The porosity of the second substrate is 45.1%; The porosity of the buffer film is 62.3%; The pore size of the first adsorption hole is 11.7 μm; the pore size of the second adsorption hole is 1 μm; The surface roughness of the side of the buffer film in contact with the semiconductor structure is 396 nm.

6. The method for thinning a semiconductor structure according to claim 1, It is characterized in that Before the step of bonding the front surface of the semiconductor structure to one side of the first substrate, the method further includes: forming an adhesive layer on the front surface of the semiconductor structure, or forming an adhesive layer on a surface of the first substrate facing the semiconductor structure; After the front surface of the semiconductor structure is bonded to one side of the first substrate, the adhesive layer is located between the first substrate and the front surface of the semiconductor structure.

7. The method for thinning a semiconductor structure according to claim 6, It is characterized in that The step of debonding the front surface of the semiconductor structure from the first substrate comprises: The adhesive layer is heated and an external force is applied to separate the front surface of the semiconductor structure from the first substrate.

8. The method for thinning a semiconductor structure according to claim 7, It is characterized in that After the step of debonding the front surface of the semiconductor structure from the first substrate, the method further includes: separating the second substrate from the buffer film, and removing the second substrate; removing the buffer film by a solution immersion process; The adhesive layer is removed by a solution soaking process.

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