Wafer thinning equipment and thinning methods

Abstract

This invention provides a wafer thinning apparatus and a thinning method. The wafer thinning apparatus includes a wafer thinning grinding wheel with a grinding wheel substrate made of a metal composite sheet. The metal composite sheet is formed by alternating layers of first and second metal materials, the total number of the first and second metal material layers being odd. Adjacent first and second metal material layers are connected by a metallurgical bonding method. The top and bottom surfaces of the metal composite sheet, positioned opposite each other, serve as the top and bottom surfaces of the grinding wheel substrate. The first metal material layer uses an alloy or metal material with a CTE not exceeding 10 ppm / ℃ and a thermal conductivity not less than 130 W / m·K. The second metal material layer uses an iron-nickel-based alloy material with a CTE not exceeding 6.0 ppm / ℃. This wafer thinning apparatus can improve the thermal expansion matching between the grinding wheel substrate and the silicon wafer and the stability of the thinned TSV structure during the wafer thinning process, achieving high precision and low damage in 3D IC thinning.

Description

Technical Field

[0001] This invention belongs to the field of wafer grinding technology, specifically relating to a wafer thinning device and a wafer thinning method. Background Technology

[0002] Three-dimensional integrated circuits (3D ICs) are an important technological path for the semiconductor industry to continue Moore's Law and improve chip performance and integration. The core idea is to stack multiple chips or functional layers vertically and achieve interlayer electrical connections through interconnection technologies such as through-silicon vias (TSVs), thereby achieving higher functional density within a limited space.

[0003] Wafer thinning is a key supporting process in 3D IC manufacturing, its main purpose being to reduce the wafer's thickness from its original level to an ultra-thin state suitable for vertical integration. Ultra-thin wafers are the physical basis for 3D stacking and are crucial for optimizing electrical performance and thermal management. As the number of 3D IC stacking layers increases, the requirements for the thinning thickness of individual wafers become increasingly stringent. Simultaneously, 3D IC technology places extremely high demands on the surface quality of the thinned wafer, including excellent Total Thickness Variation (TTV) and extremely low Roughness Average (Ra), to ensure the accuracy, consistency, and stability of subsequent bonding processes.

[0004] To achieve the aforementioned thinning targets, wafer thinning equipment typically utilizes the physical grinding action of grinding wheels to process ultra-thin wafers. Such equipment must have its grinding structure and grinding process precisely designed and controlled to meet the requirements for ultra-thin wafer processing (such as thickness ≤10μm, TTV ≤1.5μm, and Ra ≤5nm) while also considering manufacturing costs and production efficiency.

[0005] Due to the mismatch in the coefficient of thermal expansion (CTE) between the grinding wheel substrate and the silicon wafer, non-uniform thermal deformation is induced in the temperature range (20-200℃) during the grinding process. Macroscopically, the thermal warping of the end face generates periodic fluctuations, resulting in uneven wafer thinning and edge stress concentration, which in turn increases the risk of alignment deviation and the probability of wafer cracking during subsequent stacking and bonding. Microscopically, thermal deformation can cause high-frequency vibrations during the grinding process, which can cause a sudden increase in local grinding force, thereby causing the interface separation (pull-out) between the copper pillars and the silicon substrate in the through silicon via (TSV) and generating subsurface cracks with a damage layer depth of about 2μm in the silicon substrate.

[0006] Meanwhile, during the wafer thinning process of 3D IC stacking, there is a significant hardness mismatch between the copper interconnect layer (hardness ≈ 2.5 GPa) and the silicon substrate (hardness ≈ 12 GPa) in the through silicon via (TSV) of the chip. When different materials are alternately ground, the abrasive grains of the grinding wheel are subjected to severe stress fluctuations, resulting in a decrease in grinding accuracy and a deterioration in surface quality.

[0007] In short, achieving high precision and low damage in 3D IC thinning has always been a challenge in the semiconductor wafer thinning process.

[0008] Currently, some new technologies have emerged in the industry in an effort to achieve high precision and low damage in 3D IC thinning.

[0009] For example, CN104114666A discloses a polishing article and its forming method, focusing on developing a bonded polishing article with low ΔCTE. By controlling the CTE difference between the binder material and the polishing particles and through high porosity design, the risk of fracture caused by thermal stress is reduced. A combination of a glassy inorganic binder and diamond abrasive grains is developed, controlling ΔCTE (the difference in CTE between the binder and the abrasive grains) ≤ 5.5 ppm / ℃ and porosity ≥ 50%. This is suitable for semiconductor wafer polishing, reducing the thermal deformation rate by 40%.

[0010] For example, CN102470505A discloses a grinding tool and manufacturing method for dressing CMP pads with a flat and consistent planar topography. The CTE mismatch is controlled by using a low-CTE substrate and a metal binder to connect the abrasive particles in the CMP dresser. Using Invar alloy (CTE≈1.0-1.5 ppm / ℃) or Kova alloy (CTE≈5.0-6.0 ppm / ℃) as the substrate, diamond abrasive particles are connected by a metal binder, controlling the total CTE mismatch range to 0.1-5.0 ppm / ℃. The CTE difference between the substrate and the abrasive particles is ≤20%, reducing warping caused by thermal stress, and the surface flatness is ≤70 μm.

[0011] However, these new technologies all have many problems and cannot effectively achieve high precision and low damage in 3D IC thinning, for example:

[0012] (1) Adaptation limitations: Incompatible with TSV / non-silicon substrate wafers, high porosity sacrifices strength;

[0013] (2) Insufficient dynamic accuracy: Under ultra-high speed conditions, the coupling effect of centrifugal force and thermal stress causes the end jump to still exceed ±3μm;

[0014] (3) Thermal stability bottleneck: Under high temperature conditions, the metal binder is prone to softening, which leads to abrasive grain shedding and limits the application of high-speed grinding.

[0015] In conclusion, new technological solutions are still needed to achieve high precision and low damage in 3D IC thinning. Summary of the Invention

[0016] The purpose of this invention is to provide a high-precision, low-damage technical solution for achieving 3D IC thinning.

[0017] To achieve the above objectives, the present invention provides a wafer thinning device and a wafer thinning method.

[0018] In the technical solution provided by the present invention, the wafer thinning equipment includes a wafer thinning grinding wheel, which is mounted on the grinding shaft of the wafer thinning equipment. The wafer thinning grinding wheel includes a grinding wheel base, an adhesive layer, and an abrasive layer. The abrasive layer is fixed to the grinding wheel base by the adhesive layer. The grinding wheel base is made of metal composite sheet (i.e., it is made of metal composite sheet).

[0019] The metal composite sheet is formed by alternating layers of a first metal material layer and a second metal material layer (i.e., by alternating and connecting layers of a first metal material layer and a second metal material layer), wherein the total number of layers of the first metal material layer and the second metal material layer is odd (thus ensuring that the top and bottom surfaces are both the first metal material layer or the second metal material layer), and adjacent sub-layers (i.e., adjacent first metal material layers and second metal material layers) are connected by metallurgical bonding.

[0020] The first metal material layer is made of alloy or metal material with a coefficient of thermal expansion (CTE, which refers to the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 10 ppm / ℃ and a thermal conductivity not less than 130 W / m·K.

[0021] The second metal material layer uses an iron-nickel based alloy material with a coefficient of thermal expansion (CTE, which refers to the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 6.0 ppm / ℃;

[0022] The top and bottom surfaces of the metal composite sheet, which are parallel to the first metal material layer, are used as the top and bottom surfaces of the grinding wheel substrate.

[0023] This thinning equipment uses a wafer thinning grinding wheel with a special structure. The grinding wheel uses a grinding wheel substrate made of a metal composite sheet with a special structure. By using the grinding wheel substrate made of a metal composite sheet with a special structure in the thinning grinding wheel, this thinning equipment improves the thermal expansion matching between the grinding wheel substrate and the silicon wafer and the stability of the thinned TSV structure during the wafer thinning process, thus achieving high precision and low damage in 3D IC thinning.

[0024] Specifically, the metal composite sheet with the special structure adopts an alternating stacked structure of a first metal material layer and a second metal material layer, specifically formed by stacking a first metal material layer / second metal material layer / ... / first metal material layer or by stacking a second metal material layer / first metal material layer / ... / second metal material layer. Upon heating, the expansion of the first metal material layer and the contraction of the second metal material layer create a self-balancing torque. Therefore, using a grinding wheel containing a grinding wheel substrate prepared from this metal composite sheet with the special structure in a thinning device can effectively solve the CTE mismatch problem between the grinding wheel substrate and the silicon wafer, effectively suppressing overall warpage (approaching zero curvature), thereby avoiding macroscopic end-face runout and microscopic contact fluctuations caused by thermal deformation. This plays a certain role in resisting the phenomenon of grinding force surge, and to a certain extent reduces interface damage between the TSV copper pillar and the silicon substrate during wafer thinning, improving the stability of the thinned TSV structure. When a grinding wheel containing a grinding wheel substrate made of a metal composite sheet with a special structure is used in a thinning equipment, the thermal expansion matching between the grinding wheel substrate and the silicon wafer can be achieved, and the stability of the thinned TSV structure can be improved to a certain extent, thereby achieving the goal of high precision and low damage in 3DIC thinning.

[0025] In some preferred technical solutions, the structure of the wafer thinning equipment may be, but is not limited to, the structure of an existing wafer thinning equipment equipped with a grinding wheel.

[0026] In some preferred technical solutions, the wafer thinning grinding wheel is provided with an adhesive layer and an abrasive layer. The adhesive layer is disposed between the grinding wheel substrate and the abrasive layer, and the grinding wheel substrate and the abrasive layer are bonded together by the adhesive layer.

[0027] In a more preferred embodiment, the adhesive layer is made of at least one of epoxy resin, polyimide, and phenolic resin.

[0028] In a more preferred technical solution, the abrasive particles of the abrasive layer are made of at least one of diamond, cubic boron nitride, and silicon carbide.

[0029] In some preferred technical solutions, the first metal material layer is made of Cu-W alloy, Mo-Cu alloy or molybdenum metal elemental material;

[0030] In a more preferred embodiment, the first metal material layer is made of Cu-W alloy material;

[0031] In a further preferred embodiment, taking the total mass of the Cu-W alloy as 100%, the mass content of Cu in the Cu-W alloy is 20%-15%, and the mass content of W is 80%-85%.

[0032] In some preferred technical solutions, the second metal material layer is made of Invar alloy material (i.e., Fe). 36 Ni alloy materials), Kovar alloy materials (i.e., Fe) 29 Ni 17 Co alloy material) or Alloy 42 alloy material (i.e., Fe) 42 Ni alloy materials);

[0033] In a more preferred embodiment, the second metal material layer is made of Invar alloy material.

[0034] In some preferred technical solutions, the first metal material layer is made of Cu-W alloy material, and the second metal material layer is made of Invar alloy material;

[0035] The thickness ratio of the first metal material layer to the second metal material layer is (1-2):1 (e.g., 1.5:2); this preferred technical solution can better ensure that the overall equivalent CTE of the metal composite sheet is close to that of silicon (≈2.6 ppm / ℃), and better reduce thermal mismatch stress.

[0036] In some preferred technical solutions, the thickness of the first metal material layer is 0.1-0.5 mm, and the thickness of the second metal material layer is 0.1-0.5 mm.

[0037] In some preferred technical solutions, the total number of the first metal material layer and the second metal material layer is greater than or equal to 5 and less than 10.

[0038] In some preferred technical solutions, the metal composite sheet is arranged from bottom to top as a first small layer, a second small layer to an Nth small layer, with the i-th small layer and the (N-i+1)-th small layer being symmetrical with respect to the (N+1)-2-th small layer (including that the i-th small layer and the (N-i+1)-th small layer use the same material and thickness and are equidistant from the (N+1)-2-th small layer); where i is a natural number not less than 1 and not greater than N; that is, in the metal composite sheet, except for the (N+1)-2-th small layer located in the middle layer position, each of the remaining first metal material layers and each of the second metal material layers are symmetrically arranged with respect to the (N+1)-2-th small layer located in the middle layer position of the metal composite sheet;

[0039] This preferred technical solution can better ensure consistent thermal deformation behavior and avoid warping.

[0040] In some preferred technical solutions, the top and bottom layers of the metal composite sheet are both first metal material layers.

[0041] In some preferred technical solutions, the interlayer bonding strength between adjacent first metal material layers and second metal material layers is ≥200 MPa.

[0042] In some preferred technical solutions, the first metal material layer is made of Cu-W alloy material, and the second metal material layer is made of Invar alloy material; adjacent first metal material layers and second metal material layers are connected by forming a Cu3W2 and γ-FeNi composite interface layer between the first metal material layer and the second metal material layer;

[0043] In a more preferred embodiment, the Cu3W2 and γ-FeNi composite interface layer sequentially comprises a Cu3W2 and Cu solid solution mixed layer, a γ-FeNi and Cu3W2 mixed layer, and a γ-FeNi and FeNi3 mixed layer; wherein the Cu3W2 and Cu solid solution mixed layer is adjacent to the first metal material layer, and the γ-FeNi and FeNi3 mixed layer is adjacent to the second metal material layer.

[0044] In a further preferred embodiment, the thickness of the Cu3W2 and Cu solid solution mixed layer is 1-3 μm (e.g., 2 μm); the thickness of the γ-FeNi and Cu3W2 mixed layer is 1-1.5 μm (e.g., 1.2 μm); and the thickness of the γ-FeNi and FeNi3 mixed layer is 1-2 μm (e.g., 1.5 μm).

[0045] In this preferred technical solution, the strength of the Cu3W2 and Cu solid solution mixed layer is approximately 8 GPa, which helps maintain shape stability by resisting abrasive indentation; the strength of the γ-FeNi and Cu3W2 mixed layer is approximately 6 GPa, which plays a role in hardness gradient transition and stress relief; the strength of the γ-FeNi and FeNi3 mixed layer is approximately 4 GPa, which plays a role in superplastic deformation and absorbing impact energy. On the one hand, it can achieve hardness gradient adaptation, gradually changing from 8 GPa on the side of the first metal material layer (Cu-W alloy layer) (adapting to silicon grinding) to 4 GPa on the side of the second metal material layer (Invar alloy layer) (protecting the copper pillars in the TSV structure), mitigating sudden hardness changes, and better improving the stability of the thinned TSV structure, thereby further achieving the goal of high precision and low damage in 3D IC thinning; on the other hand, it can improve fracture toughness (up to 15 MPa·m¹ / ²), more effectively avoiding interface cracking caused by grinding stress, and further improving the durability of the grinding wheel.

[0046] In some preferred embodiments, the metal composite sheet is prepared by a method comprising the following steps:

[0047] 1) Obtain the first metallic material layer and the second metallic material layer;

[0048] 2) The first metal material layer and the second metal material layer are stacked alternately;

[0049] 3) The alternating first and second metal material layers are subjected to diffusion welding to achieve metallurgical bonding between adjacent first and second metal material layers, thereby preparing a metal composite sheet.

[0050] In a more preferred embodiment, the preparation method further includes:

[0051] 4) After diffusion welding in step 3), the metal composite sheet obtained is subjected to end face fine grinding to achieve an absolute thickness tolerance of no more than 0.005 mm and a flatness of ≤3 μm, thereby better meeting the installation accuracy requirements of TSV thinning.

[0052] In a more preferred embodiment, the diffusion welding of the alternately stacked first and second metal material layers includes:

[0053] Metallurgical bonding steps: The alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace and subjected to heat preservation and pressure treatment in a vacuum environment to allow atomic diffusion (bidirectional diffusion) at the interlayer interface to form a metallurgical bond.

[0054] Cooling process: The product obtained from the metallurgical bonding process is cooled to obtain a metal composite sheet.

[0055] In some preferred technical solutions, when the first metal material layer is made of Cu-W alloy and the second metal material layer is made of Invar alloy, the heat preservation and pressure treatment is carried out at 900-950℃ and 30-50MPa axial pressure.

[0056] In a more preferred technical solution, the metallurgical bonding step includes:

[0057] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum conditions, the temperature is increased from room temperature to 900-950℃ (below the eutectic temperature of Cu and W) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under heat preservation conditions, an axial pressure of 30-50MPa is applied for 1-3 hours (e.g., 2 hours) to allow interlayer atomic diffusion (bidirectional diffusion) to form a metallurgical bond.

[0058] In a more preferred technical solution, the metallurgical bonding step includes:

[0059] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum, the temperature is increased from room temperature to 830-870℃ (e.g., 850℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz), with a trough pressure of 25-35MPa (e.g., 30MPa) and a peak pressure of 45-55MPa (e.g., 50MPa) is applied for 0.5-1.5h (e.g., 1h). Atomic interdiffusion occurs between the first metal material layer (Cu-W alloy layer) and the second metal material layer (Invar alloy layer), forming a transition layer (typically about 5μm thick). The temperature is then further increased to 900-950℃ (e.g., 920℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Finally, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz) is applied. A sinusoidal axial pressure of 25-35 MPa (e.g., 30 MPa) at the trough and 45-55 MPa (e.g., 50 MPa) for 20-60 minutes (e.g., 40 minutes) triggers an in-situ reaction, thereby generating a metastable Cu3W2 phase (enhancing hardness) and a tough γ-FeNi phase (improving buffering capacity), forming a Cu3W2 and γ-FeNi composite interface layer.

[0060] In some preferred technical solutions, the vacuum environment is achieved by evacuating the vacuum diffusion welding furnace to a pressure in the gas phase that does not exceed 5 × 10⁻⁶. -4 Provided via Pa.

[0061] In some preferred technical solutions, the cooling of the product obtained in the metallurgical bonding step includes: naturally cooling the product obtained in the metallurgical bonding step to 150-250°C (e.g., 200°C) in the furnace, and then introducing inert gas to cool it to a temperature not higher than 40°C at a cooling rate of not less than 50°C / min; this cooling treatment method can effectively suppress the formation of brittle phases at the interface and better ensure that the interlayer bonding strength is ≥200MPa.

[0062] In some preferred technical solutions, the first and second metal material layers are first subjected to surface polishing before being alternately stacked, so that their surface roughness meets Ra≤0.8μm.

[0063] In some preferred technical solutions, the first and second metal material layers are cleaned before being alternately stacked, for example, by ultrasonic cleaning with anhydrous ethanol for 15 minutes and then drying at 80°C.

[0064] In the technical solution provided by the present invention, the wafer thinning method includes wafer thinning using the wafer thinning equipment provided by the technical solution of the present invention.

[0065] In some preferred technical solutions, wafer thinning refers to ultra-thinning of 3D IC wafers (ultra-thinning refers to thinning the wafer to a thickness of no more than 50μm).

[0066] In a more preferred technical solution, the 3D IC wafer is thinned to a thickness of no more than 10μm.

[0067] The technical solution provided by this invention can improve the thermal expansion matching between the grinding wheel substrate and the silicon wafer and the stability of the thinned TSV structure during wafer thinning, achieving high precision and low damage in 3D IC thinning. Compared with the prior art, the technical solution provided by this invention has the following beneficial effects:

[0068] (1) Improved the thermal expansion matching between the grinding wheel substrate and the silicon wafer during wafer thinning, thereby effectively controlling the macroscopic end face runout of the grinding wheel and ensuring that the flatness of the grinding wheel substrate remains good under heating conditions. Low and stable end face runout ensures the uniformity of grinding and reduces TTV. Using the technical solution provided by this invention for ultra-thin (<50μm) wafer thinning, the end face runout is <3μm and the TTV is less than 1μm. Under the same conditions, using the conventional technical solution (the grinding wheel substrate is made of aluminum alloy) for ultra-thin (<50μm) wafer thinning, the end face runout will reach 10μm and the TTV will reach 1.5μm.

[0069] (2) It suppresses the peak value of single grinding stress, thereby improving the stability of the thinned TSV structure, reducing the risk of copper pillar collapse and cracking in the dense TSV area, and improving the yield; in particular, the preferred technical solution of forming Cu3W2 and γ-FeNi composite interface layer between Cu-W alloy layer and Invar alloy layer provided by the present invention can reduce the risk of copper pillar collapse and cracking in the dense TSV area by more than 60% and improve the yield to more than 95% compared with the conventional technical solution (the grinding wheel substrate is made of aluminum alloy). Attached Figure Description

[0070] Figure 1 This is a three-dimensional structural diagram of a wafer thinning device.

[0071] Figure 2 This is a side view schematic diagram of the structure of a wafer thinning equipment.

[0072] Figure 3 This is a side view schematic diagram of the structure of the grinding wheel used for wafer thinning in Example 2.

[0073] Figure 4 This is a bottom view of the structure of the grinding wheel used for wafer thinning in Example 1.

[0074] Figure 5 This is a side view schematic diagram of the structure of the grinding wheel used for wafer thinning in Example 3.

[0075] Figure 6 The images show a comparison of grinding wheel end runout in Example 1 and Comparative Example 1.

[0076] Figure 7 This is a TTV diagram of Example 1.

[0077] Figure 8 This is the TTV diagram for Comparative Example 1.

[0078] Figure 9 This is a flowchart of the wafer thinning operation. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0080] A specific embodiment of the first aspect of the present invention provides a metal composite sheet, wherein the metal composite sheet is formed by alternatingly stacking a first metal material layer and a second metal material layer (i.e., by alternatingly stacking and connecting the first metal material layer and the second metal material layer), that is, the total number of the first metal material layer and the second metal material layer is an odd number (thereby ensuring that the top and bottom surfaces are both the first metal material layer or the second metal material layer), and the adjacent sub-layers (i.e., adjacent first metal material layers and second metal material layers) are connected by a metallurgical bonding method;

[0081] The first metal material layer is made of alloy or metal material with a coefficient of thermal expansion (CTE, which is the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 10 ppm / ℃ and a thermal conductivity not less than 130 W / m·K; the second metal material layer is made of iron-nickel based alloy material with a coefficient of thermal expansion (CTE, which is the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 6.0 ppm / ℃.

[0082] This metal composite sheet adopts an alternating stacked structure of a first metal material layer and a second metal material layer, specifically formed by stacking the first metal material layer / second metal material layer / first metal material layer / second metal material layer / ... / first metal material layer or by stacking the second metal material layer / first metal material layer / second metal material layer / first metal material layer / ... / second metal material layer. Upon heating, the expansion of the first metal material layer and the contraction of the second metal material layer create a self-balancing torque. Therefore, when used as a grinding wheel substrate material, it can effectively solve the CTE mismatch problem between the grinding wheel substrate and the silicon wafer, effectively suppressing overall warpage (approaching zero curvature), thereby avoiding macroscopic end-face runout and microscopic contact fluctuations caused by thermal deformation. This plays a certain role in resisting the phenomenon of grinding force surge and, to some extent, reducing interface damage between the TSV copper pillar and the silicon substrate during wafer thinning, improving the stability of the thinned TSV structure. When used as a grinding wheel substrate material, this metal composite sheet can achieve thermal expansion matching between the grinding wheel substrate and the silicon wafer, and can also improve the stability of the thinned TSV structure to a certain extent, thereby achieving the goal of high precision and low damage in 3D IC thinning.

[0083] Furthermore, the first metallic material layer is made of Cu-W alloy, Mo-Cu alloy, or molybdenum metal.

[0084] Furthermore, the first metal material layer is made of Cu-W alloy material;

[0085] Furthermore, taking the total mass of the Cu-W alloy as 100%, the mass content of Cu in the Cu-W alloy is 20%-15%, and the mass content of W is 80%-85%.

[0086] Furthermore, the second metal material layer is made of Invar alloy material (i.e., Fe). 36 Ni alloy materials), Kovar alloy materials (i.e., Fe) 29 Ni 17 Co alloy material) or Alloy 42 alloy material (i.e., Fe) 42 Ni alloy materials);

[0087] Furthermore, the second metal material layer is made of Invar alloy material.

[0088] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; the thickness ratio of the first metal material layer to the second metal material layer is (1-2):1 (e.g., 3:2).

[0089] Furthermore, the thickness of the second metal material layer is 0.1-0.5 mm, and the thickness of the first metal material layer is 0.1-0.5 mm.

[0090] Furthermore, the total number of the second metal material layer and the first metal material layer is greater than or equal to 5 and less than 10.

[0091] Furthermore, the metal composite sheet consists of a first small layer, a second small layer, and an Nth small layer from bottom to top. The i-th small layer and the (N-i+1)-th small layer are symmetrical with respect to the (N+1)-2-th small layer (including the fact that the i-th small layer and the (N-i+1)-th small layer use the same material and have the same thickness, and are equidistant from the (N+1)-2-th small layer). Here, i is a natural number that is not less than 1 and not greater than N. That is, all the first metal material layers and all the second metal material layers in the metal composite sheet, except for the (N+1)-2-th small layer located in the middle layer, are symmetrically arranged with respect to the (N+1)-2-th small layer located in the middle layer of the metal composite sheet.

[0092] Furthermore, both the top and bottom layers of the metal composite sheet are the first metal material layer.

[0093] Furthermore, the interlayer bonding strength of adjacent sublayers (i.e., adjacent first metal material layer and second metal material layer) is ≥200 MPa.

[0094] Furthermore, adjacent sub-layers (i.e., adjacent first metal material layer and second metal material layer) are connected by forming a composite interface layer between adjacent sub-layers (i.e., first metal material layer and second metal material layer);

[0095] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; adjacent first and second metal material layers are connected by forming a Cu3W2 and γ-FeNi composite interface layer between the first and second metal material layers.

[0096] Furthermore, the Cu3W2 and γ-FeNi composite interface layer sequentially includes a Cu3W2 and Cu solid solution mixed layer, a γ-FeNi and Cu3W2 mixed layer, and a γ-FeNi and FeNi3 mixed layer; wherein, the Cu3W2 and Cu solid solution mixed layer is adjacent to the first metal material layer, and the γ-FeNi and FeNi3 mixed layer is adjacent to the second metal material layer;

[0097] Furthermore, the thickness of the Cu3W2 and Cu solid solution mixed layer is 1-3 μm (e.g., 2 μm); the thickness of the γ-FeNi and Cu3W2 mixed layer is 1-1.5 μm (e.g., 1.2 μm); and the thickness of the γ-FeNi and FeNi3 mixed layer is 1-2 μm (e.g., 1.5 μm).

[0098] A specific embodiment of the second aspect of the present invention provides a method for preparing a metal composite sheet, used to prepare the metal composite sheet provided in the embodiments of the first aspect of the present invention, wherein the preparation method includes:

[0099] 1) Obtain the first metallic material layer and the second metallic material layer;

[0100] 2) The first metal material layer and the second metal material layer are stacked alternately;

[0101] 3) The alternating first and second metal material layers are subjected to diffusion welding to achieve metallurgical bonding between adjacent first and second metal material layers, thereby preparing a metal composite sheet.

[0102] Furthermore, the diffusion welding of the alternately stacked first and second metal material layers includes:

[0103] Metallurgical bonding steps: The alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace and subjected to heat preservation and pressure treatment in a vacuum environment to allow atomic diffusion (bidirectional diffusion) at the interlayer interface to form a metallurgical bond.

[0104] Cooling process: The product obtained from the metallurgical bonding process is cooled to obtain a metal composite sheet.

[0105] Furthermore, when the first metal material layer is made of Cu-W alloy and the second metal material layer is made of Invar alloy, the heat preservation and pressure treatment is carried out at 900-950℃ and 30-50MPa axial pressure.

[0106] Furthermore, the metallurgical bonding steps include:

[0107] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum conditions, the temperature is increased from room temperature to 900-950℃ (below the eutectic temperature of Cu and W) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under heat preservation conditions, an axial pressure of 30-50MPa is applied for 1-3 hours (e.g., 2 hours) to allow interlayer atomic diffusion (bidirectional diffusion) to form a metallurgical bond.

[0108] Furthermore, the metallurgical bonding steps include:

[0109] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum, the temperature is increased from room temperature to 830-870℃ (e.g., 850℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz), with a trough pressure of 25-35MPa (e.g., 30MPa) and a peak pressure of 45-55MPa (e.g., 50MPa) is applied for 0.5-1.5h (e.g., 1h). Atomic interdiffusion occurs between the first metal material layer (Cu-W alloy layer) and the second metal material layer (Invar alloy layer), forming a transition layer (typically about 5μm thick). The temperature is then further increased to 900-950℃ (e.g., 920℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Finally, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz) is applied. A sinusoidal axial pressure of 20-60 min (e.g., 40 min) with a trough pressure of 25-35 MPa (e.g., 30 MPa) and a peak pressure of 45-55 MPa (e.g., 50 MPa) triggers an in-situ reaction, thereby generating a metastable Cu3W2 phase (enhancing hardness) and a tough γ-FeNi phase (improving buffering capacity), forming a Cu3W2 and γ-FeNi composite interface layer.

[0110] Furthermore, the vacuum environment is achieved by evacuating the vacuum diffusion welding furnace to a pressure in the gas phase that does not exceed 5 × 10⁻⁶. - 4 Provided via Pa.

[0111] Furthermore, the cooling of the product obtained in the metallurgical bonding step includes: naturally cooling the product obtained in the metallurgical bonding step to 150-250°C (e.g., 200°C) in the furnace, and then introducing inert gas to cool it to a temperature not higher than 40°C at a cooling rate of not less than 50°C / min; this cooling treatment method can effectively suppress the formation of brittle phases at the interface and better ensure that the interlayer bonding strength is ≥200MPa.

[0112] Furthermore, the first and second metal material layers are subjected to surface polishing before being alternately stacked to ensure that their surface roughness meets the requirement of Ra≤0.8μm.

[0113] Furthermore, the first and second metal material layers are cleaned before being alternately stacked, for example, by ultrasonic cleaning with anhydrous ethanol for 15 minutes and then drying at 80°C.

[0114] Furthermore, the method for preparing the metal composite sheet also includes:

[0115] 4) After diffusion welding in step 3), the metal composite sheet obtained is subjected to end face fine grinding to achieve an absolute thickness tolerance of no more than 0.005 mm and a flatness of ≤3 μm, thereby better meeting the installation accuracy requirements of TSV thinning.

[0116] A specific embodiment of the third aspect of the present invention provides a grinding wheel substrate for a wafer thinning grinding wheel. The grinding wheel substrate is made of the metal composite sheet provided in the specific embodiment of the first aspect of the present invention. Specifically, the grinding wheel substrate is composed of a metal composite sheet, which is formed by alternating layers of a first metal material and a second metal material (i.e., by alternatingly stacking and connecting the first metal material layer and the second metal material layer). The total number of the first metal material layer and the second metal material layer is odd (thus ensuring that the top and bottom surfaces are both either the first metal material layer or the second metal material layer). Adjacent sublayers (i.e., adjacent first metal material layers and second metal material layers) are connected by a metallurgical bonding method. The first metal material layer uses an alloy or metal material with a coefficient of thermal expansion (CTE, the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 10 ppm / ℃ and a thermal conductivity not less than 130 W / m·K. The second metal material layer uses a coefficient of thermal expansion (CTE, the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 6.0. Iron-nickel based alloy material at ppm / ℃; the top and bottom surfaces of the metal composite sheet, which are parallel to the first metal material layer, are used as the top and bottom surfaces of the grinding wheel substrate (i.e., the top surface of the metal composite sheet is used as the top surface of the grinding wheel substrate and its bottom surface opposite to the top surface is used as the bottom surface of the grinding wheel substrate, or the bottom surface of the metal composite sheet is used as the top surface of the grinding wheel substrate and its bottom surface opposite to the top surface is used as the top surface of the grinding wheel substrate).

[0117] This grinding wheel substrate, with its special metal composite sheet material, improves the thermal expansion matching between the grinding wheel substrate and the silicon wafer and the stability of the thinned TSV structure during the wafer thinning process, achieving high precision and low damage in 3D IC thinning.

[0118] Furthermore, the first metallic material layer is made of Cu-W alloy, Mo-Cu alloy, or molybdenum metal.

[0119] Furthermore, the first metal material layer is made of Cu-W alloy material;

[0120] Furthermore, taking the total mass of the Cu-W alloy as 100%, the mass content of Cu in the Cu-W alloy is 20%-15%, and the mass content of W is 80%-85%.

[0121] Furthermore, the second metal material layer is made of Invar alloy material (i.e., Fe). 36 Ni alloy materials), Kovar alloy materials (i.e., Fe)29 Ni 17 Co alloy materials), Alloy 42 alloy materials (i.e., Fe) 42 Ni alloy materials);

[0122] Furthermore, the second metal material layer is made of Invar alloy material.

[0123] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; the thickness ratio of the first metal material layer to the second metal material layer is (1-2):1 (e.g., 3:2).

[0124] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; the thickness ratio of the first metal material layer to the second metal material layer is (1-2):1 (e.g., 3:2).

[0125] Furthermore, the thickness of the second metal material layer is 0.1-0.5 mm, and the thickness of the first metal material layer is 0.1-0.5 mm.

[0126] Furthermore, the total number of the second metal material layer and the first metal material layer is greater than or equal to 5 and less than 10.

[0127] Furthermore, the metal composite sheet is named sequentially from bottom to top as the first small layer, the second small layer to the Nth small layer, and the i-th small layer and the (N-i+1)-th small layer are symmetrical with respect to the (N+1)-2-th small layer (including the fact that the i-th small layer and the (N-i+1)-th small layer use the same material and thickness and are equidistant from the (N+1)-2-th small layer); where i is a natural number not less than 1 and not greater than N; that is, in the metal composite sheet, except for the (N+1)-2-th small layer located in the middle layer position, each of the first metal material layers and each of the second metal material layers are symmetrically arranged with respect to the (N+1)-2-th small layer located in the middle layer position of the metal composite sheet.

[0128] Furthermore, both the top and bottom layers of the metal composite sheet are the first metal material layer.

[0129] Furthermore, the interlayer bonding strength of adjacent sublayers (i.e., adjacent first metal material layer and second metal material layer) is ≥200 MPa.

[0130] Furthermore, adjacent sub-layers (i.e., adjacent first metal material layer and second metal material layer) are connected by forming a composite interface layer between adjacent sub-layers (i.e., first metal material layer and second metal material layer);

[0131] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; adjacent first and second metal material layers are connected by forming a Cu3W2 and γ-FeNi composite interface layer between the first and second metal material layers.

[0132] Furthermore, the Cu3W2 and γ-FeNi composite interface layer sequentially includes a Cu3W2 and Cu solid solution mixed layer, a γ-FeNi and Cu3W2 mixed layer, and a γ-FeNi and FeNi3 mixed layer; wherein, the Cu3W2 and Cu solid solution mixed layer is adjacent to the first metal material layer, and the γ-FeNi and FeNi3 mixed layer is adjacent to the second metal material layer;

[0133] Furthermore, the thickness of the Cu3W2 and Cu solid solution mixed layer is 1-3 μm (e.g., 2 μm); the thickness of the γ-FeNi and Cu3W2 mixed layer is 1-1.5 μm (e.g., 1.2 μm); and the thickness of the γ-FeNi and FeNi3 mixed layer is 1-2 μm (e.g., 1.5 μm).

[0134] Furthermore, the structure of the grinding wheel substrate can be, but is not limited to, the structure of the grinding wheel substrate of an existing wafer thinning grinding wheel.

[0135] A specific embodiment of the fourth aspect of the present invention provides a method for preparing a grinding wheel substrate for a wafer thinning grinding wheel to prepare the grinding wheel substrate for a wafer thinning grinding wheel provided in the third aspect of the present invention. The method utilizes the metal composite sheet provided in the first aspect of the present invention to prepare the grinding wheel substrate, including preparing a metal composite sheet using the metal composite sheet provided in the second aspect of the present invention, and then preparing the grinding wheel substrate for the wafer thinning grinding wheel using the metal composite sheet; specifically including:

[0136] A. Preparation of metal composite sheets;

[0137] 1) Obtain the first metallic material layer and the second metallic material layer;

[0138] 2) The first metal material layer and the second metal material layer are stacked alternately;

[0139] 3) The alternating first and second metal material layers are subjected to diffusion welding to achieve metallurgical bonding between adjacent first and second metal material layers, thereby preparing a metal composite sheet.

[0140] B. Using metal composite sheets to prepare the grinding wheel substrate for wafer thinning grinding wheels.

[0141] Furthermore, the diffusion welding of the alternately stacked first and second metal material layers includes:

[0142] Metallurgical bonding steps: The alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace and subjected to heat preservation and pressure treatment in a vacuum environment to allow atomic diffusion (bidirectional diffusion) at the interlayer interface to form a metallurgical bond.

[0143] Cooling process: The product obtained from the metallurgical bonding process is cooled to obtain a metal composite sheet.

[0144] Furthermore, when the first metal material layer is made of Cu-W alloy and the second metal material layer is made of Invar alloy, the heat preservation and pressure treatment is carried out at 900-950℃ and 30-50MPa axial pressure.

[0145] Furthermore, the metallurgical bonding steps include:

[0146] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum conditions, the temperature is increased from room temperature to 900-950℃ (below the eutectic temperature of Cu and W) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under heat preservation conditions, an axial pressure of 30-50MPa is applied for 1-3 hours (e.g., 2 hours) to allow interlayer atomic diffusion (bidirectional diffusion) to form a metallurgical bond.

[0147] Furthermore, the metallurgical bonding steps include:

[0148] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum, the temperature is increased from room temperature to 830-870℃ (e.g., 850℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz), with a trough pressure of 25-35MPa (e.g., 30MPa) and a peak pressure of 45-55MPa (e.g., 50MPa) is applied for 0.5-1.5h (e.g., 1h). Atomic interdiffusion occurs between the first metal material layer (Cu-W alloy layer) and the second metal material layer (Invar alloy layer), forming a transition layer (typically about 5μm thick). The temperature is then further increased to 900-950℃ (e.g., 920℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Finally, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz) is applied. A sinusoidal axial pressure of 20-60 min (e.g., 40 min) with a trough pressure of 25-35 MPa (e.g., 30 MPa) and a peak pressure of 45-55 MPa (e.g., 50 MPa) triggers an in-situ reaction, thereby generating a metastable Cu3W2 phase (enhancing hardness) and a tough γ-FeNi phase (improving buffering capacity), forming a Cu3W2 and γ-FeNi composite interface layer.

[0149] Furthermore, the vacuum environment is achieved by evacuating the vacuum diffusion welding furnace to a pressure in the gas phase that does not exceed 5 × 10⁻⁶. - 4 Provided via Pa.

[0150] Furthermore, the cooling of the product obtained in the metallurgical bonding step includes: naturally cooling the product obtained in the metallurgical bonding step to 150-250°C (e.g., 200°C) in the furnace, and then introducing inert gas to cool it to a temperature not higher than 40°C at a cooling rate of not less than 50°C / min; this cooling treatment method can effectively suppress the formation of brittle phases at the interface and better ensure that the interlayer bonding strength is ≥200MPa.

[0151] Furthermore, the first and second metal material layers are subjected to surface polishing before being alternately stacked to ensure that their surface roughness meets the requirement of Ra≤0.8μm.

[0152] Furthermore, the first and second metal material layers are cleaned before being alternately stacked, for example, by ultrasonic cleaning with anhydrous ethanol for 15 minutes and then drying at 80°C.

[0153] Furthermore, the step of preparing the metal composite sheet also includes:

[0154] 4) After diffusion welding in step 3), the metal composite sheet obtained is subjected to end face fine grinding to achieve an absolute thickness tolerance of no more than 0.005 mm and a flatness of ≤3 μm, thereby better meeting the installation accuracy requirements of TSV thinning.

[0155] A specific embodiment of the fifth aspect of the present invention provides a wafer thinning grinding wheel, which is provided with a grinding wheel substrate of the wafer thinning grinding wheel provided in the embodiment of the third aspect of the present invention. Specifically, the wafer thinning grinding wheel includes a grinding wheel substrate, an adhesive layer, and an abrasive layer. The abrasive layer is fixed to the grinding wheel substrate by the adhesive layer. The grinding wheel substrate is made of a metal composite sheet (i.e., it is made of metal composite sheet). The metal composite sheet is formed by alternatingly stacking a first metal material layer and a second metal material layer (i.e., by alternatingly stacking and connecting the first metal material layer and the second metal material layer). The total number of the first metal material layer and the second metal material layer is odd (thereby ensuring that the top and bottom surfaces are both the first metal material layer or the second metal material layer). Adjacent sublayers (i.e., adjacent first metal material layers and second metal material layers) are connected by a metallurgical bonding method. The first metal material layer has a coefficient of thermal expansion (CTE) (meaning the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 10. The second metal material layer is made of an alloy or metal material with a thermal conductivity of not less than 130 W / m·K and a coefficient of thermal expansion (CTE) of not more than 6.0 ppm / ℃. The top and bottom surfaces of the metal composite sheet, which are parallel to the first metal material layer, are used as the top and bottom surfaces of the grinding wheel substrate (i.e., the top surface of the metal composite sheet is used as the top surface of the grinding wheel substrate and the bottom surface opposite to the top surface is used as the bottom surface of the grinding wheel substrate, or the bottom surface of the metal composite sheet is used as the top surface of the grinding wheel substrate and the bottom surface opposite to the top surface is used as the top surface of the grinding wheel substrate).

[0156] This wafer thinning grinding wheel improves the thermal expansion matching between the grinding wheel substrate and the silicon wafer and the stability of the thinned TSV structure by using a special material grinding wheel substrate, thus achieving high precision and low damage in 3D IC thinning.

[0157] Furthermore, the first metallic material layer is made of Cu-W alloy, Mo-Cu alloy, or molybdenum metal.

[0158] Furthermore, the first metal material layer is made of Cu-W alloy material;

[0159] Furthermore, taking the total mass of the Cu-W alloy as 100%, the mass content of Cu in the Cu-W alloy is 20%-15%, and the mass content of W is 80%-85%.

[0160] Furthermore, the second metal material layer is made of Invar alloy material (i.e., Fe). 36 Ni alloy materials), Kovar alloy materials (i.e., Fe) 29 Ni 17 Co alloy materials), Alloy 42 alloy materials (i.e., Fe) 42 Ni alloy materials);

[0161] Furthermore, the second metal material layer is made of Invar alloy material.

[0162] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; the thickness ratio of the first metal material layer to the second metal material layer is (1-2):1 (e.g., 3:2).

[0163] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; the thickness ratio of the first metal material layer to the second metal material layer is (1-2):1 (e.g., 3:2).

[0164] Furthermore, the thickness of the second metal material layer is 0.1-0.5 mm, and the thickness of the first metal material layer is 0.1-0.5 mm.

[0165] Furthermore, the total number of the second metal material layer and the first metal material layer is greater than or equal to 5 and less than 10.

[0166] Furthermore, the metal composite sheet is named sequentially from bottom to top as the first small layer, the second small layer to the Nth small layer, and the i-th small layer and the (N-i+1)-th small layer are symmetrical with respect to the (N+1)-2-th small layer (including the fact that the i-th small layer and the (N-i+1)-th small layer use the same material and thickness and are equidistant from the (N+1)-2-th small layer); where i is a natural number not less than 1 and not greater than N; that is, in the metal composite sheet, except for the (N+1)-2-th small layer located in the middle layer position, each of the first metal material layers and each of the second metal material layers are symmetrically arranged with respect to the (N+1)-2-th small layer located in the middle layer position of the metal composite sheet.

[0167] Furthermore, both the top and bottom layers of the metal composite sheet are the first metal material layer.

[0168] Furthermore, the interlayer bonding strength of adjacent sublayers (i.e., adjacent first metal material layer and second metal material layer) is ≥200 MPa.

[0169] Furthermore, adjacent sub-layers (i.e., adjacent first metal material layer and second metal material layer) are connected by forming a composite interface layer between adjacent sub-layers (i.e., first metal material layer and second metal material layer);

[0170] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; adjacent first and second metal material layers are connected by forming a Cu3W2 and γ-FeNi composite interface layer between the first and second metal material layers.

[0171] Furthermore, the Cu3W2 and γ-FeNi composite interface layer sequentially includes a Cu3W2 and Cu solid solution mixed layer, a γ-FeNi and Cu3W2 mixed layer, and a γ-FeNi and FeNi3 mixed layer; wherein, the Cu3W2 and Cu solid solution mixed layer is adjacent to the first metal material layer, and the γ-FeNi and FeNi3 mixed layer is adjacent to the second metal material layer;

[0172] Furthermore, the thickness of the Cu3W2 and Cu solid solution mixed layer is 1-3 μm (e.g., 2 μm); the thickness of the γ-FeNi and Cu3W2 mixed layer is 1-1.5 μm (e.g., 1.2 μm); and the thickness of the γ-FeNi and FeNi3 mixed layer is 1-2 μm (e.g., 1.5 μm).

[0173] Furthermore, the structure of the grinding wheel substrate can be, but is not limited to, the structure of the grinding wheel substrate of an existing wafer thinning grinding wheel.

[0174] Furthermore, the wafer thinning grinding wheel is provided with an adhesive layer and an abrasive layer. The adhesive layer is disposed between the grinding wheel substrate and the abrasive layer, and the grinding wheel substrate and the abrasive layer are bonded together by the adhesive layer.

[0175] The adhesive layer may, but is not limited to, use existing adhesive layer materials for wafer thinning grinding wheels. For example, the adhesive layer may use at least one of epoxy resin, polyimide, and phenolic resin.

[0176] The abrasive layer may, but is not limited to, using existing abrasive layer materials for wafer thinning grinding wheels. For example, the abrasive grains of the abrasive layer may be made of at least one of diamond, cubic boron nitride, and silicon carbide.

[0177] A specific embodiment of the sixth aspect of the present invention provides a method for preparing a wafer thinning grinding wheel to prepare the wafer thinning grinding wheel provided in the fifth aspect of the present invention. The method involves bonding the grinding wheel substrate and the abrasive layer provided in the third aspect of the present invention together using an adhesive layer, thereby preparing the wafer thinning grinding wheel. Specifically, the method includes preparing the grinding wheel substrate using the method for preparing the grinding wheel substrate provided in the fourth aspect of the present invention, and then bonding the grinding wheel substrate and the abrasive layer together using an adhesive layer to prepare the wafer thinning grinding wheel. More specifically, the method for preparing the wafer thinning grinding wheel includes:

[0178] A. Preparation of metal composite sheets;

[0179] 1) Obtain the first metallic material layer and the second metallic material layer;

[0180] 2) The first metal material layer and the second metal material layer are stacked alternately;

[0181] 3) The alternating first and second metal material layers are subjected to diffusion welding to achieve metallurgical bonding between adjacent first and second metal material layers, thereby preparing a metal composite sheet.

[0182] B. Using metal composite sheets to prepare the grinding wheel substrate for wafer thinning grinding wheels;

[0183] C. The grinding wheel for wafer thinning is prepared by bonding the grinding wheel substrate and the abrasive layer together using an adhesive layer.

[0184] Furthermore, the diffusion welding of the alternately stacked first and second metal material layers includes:

[0185] Metallurgical bonding steps: The alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace and subjected to heat preservation and pressure treatment in a vacuum environment to allow atomic diffusion (bidirectional diffusion) at the interlayer interface to form a metallurgical bond.

[0186] Cooling process: The product obtained from the metallurgical bonding process is cooled to obtain a metal composite sheet.

[0187] Furthermore, when the first metal material layer is made of Cu-W alloy and the second metal material layer is made of Invar alloy, the heat preservation and pressure treatment is carried out at 900-950℃ and 30-50MPa axial pressure.

[0188] Furthermore, the metallurgical bonding steps include:

[0189] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum conditions, the temperature is increased from room temperature to 900-950℃ (below the eutectic temperature of Cu and W) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under heat preservation conditions, an axial pressure of 30-50MPa is applied for 1-3 hours (e.g., 2 hours) to allow interlayer atomic diffusion (bidirectional diffusion) to form a metallurgical bond.

[0190] Furthermore, the metallurgical bonding steps include:

[0191] Alternating layers of first and second metal materials are placed in a vacuum diffusion welding furnace. Under vacuum, the temperature is increased from room temperature to 830-870℃ (e.g., 850℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Then, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz), with a trough pressure of 25-35MPa (e.g., 30MPa) and a peak pressure of 45-55MPa (e.g., 50MPa) is applied for 0.5-1.5h (e.g., 1h). Atomic interdiffusion occurs between the first metal material layer (Cu-W alloy layer) and the second metal material layer (Invar alloy layer), forming a transition layer (typically about 5μm thick). The temperature is then further increased to 900-950℃ (e.g., 920℃) at a heating rate of 3-7℃ / min (e.g., 5℃ / min). Finally, under holding conditions, a sinusoidal axial pressure of 8-12Hz (e.g., 10 Hz) is applied. A sinusoidal axial pressure of 20-60 min (e.g., 40 min) with a trough pressure of 25-35 MPa (e.g., 30 MPa) and a peak pressure of 45-55 MPa (e.g., 50 MPa) triggers an in-situ reaction, thereby generating a metastable Cu3W2 phase (enhancing hardness) and a tough γ-FeNi phase (improving buffering capacity), forming a Cu3W2 and γ-FeNi composite interface layer.

[0192] Furthermore, the vacuum environment is achieved by evacuating the vacuum diffusion welding furnace to a pressure in the gas phase that does not exceed 5 × 10⁻⁶. - 4 Provided via Pa.

[0193] Furthermore, the cooling of the product obtained in the metallurgical bonding step includes: naturally cooling the product obtained in the metallurgical bonding step to 150-250°C (e.g., 200°C) in the furnace, and then introducing inert gas to cool it to a temperature not higher than 40°C at a cooling rate of not less than 50°C / min; this cooling treatment method can effectively suppress the formation of brittle phases at the interface and better ensure that the interlayer bonding strength is ≥200MPa.

[0194] Furthermore, the first and second metal material layers are subjected to surface polishing before being alternately stacked to ensure that their surface roughness meets the requirement of Ra≤0.8μm.

[0195] Furthermore, the first and second metal material layers are cleaned before being alternately stacked, for example, by ultrasonic cleaning with anhydrous ethanol for 15 minutes and then drying at 80°C.

[0196] Furthermore, the step of preparing the metal composite sheet also includes:

[0197] 4) After diffusion welding in step 3), the metal composite sheet obtained is subjected to end face fine grinding to achieve an absolute thickness tolerance of no more than 0.005 mm and a flatness of ≤3 μm, thereby better meeting the installation accuracy requirements of TSV thinning.

[0198] A seventh aspect of the present invention provides a wafer thinning apparatus, which is equipped with a wafer thinning grinding wheel provided in a fifth aspect of the present invention; specifically, the wafer thinning apparatus includes a wafer thinning grinding wheel mounted on a grinding shaft of the wafer thinning apparatus, the wafer thinning grinding wheel including a grinding wheel substrate, an adhesive layer and an abrasive layer, the abrasive layer being fixed to the grinding wheel substrate by the adhesive layer; the grinding wheel substrate is constructed of a metal composite sheet (i.e., made of a metal composite sheet), the metal composite sheet being formed by alternating layers of a first metal material layer and a second metal material layer. This is formed by alternating and connecting first and second metal material layers, named sequentially from bottom to top as the first sublayer, second sublayer, up to the Nth sublayer, where N (the sum of the number of first and second metal material layers) is an odd number (ensuring that the top and bottom surfaces are both first or second metal material layers). Adjacent sublayers (i.e., adjacent first and second metal material layers) are connected by metallurgical bonding. The first metal material layer has a coefficient of thermal expansion (CTE, the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 10ppm / ℃ and a thermal conductivity not less than 130. The alloy or metallic material has a W / m·K ratio; the second metallic material layer uses an iron-nickel based alloy material with a coefficient of thermal expansion (CTE, which refers to the average coefficient of thermal expansion in the range of 20-200℃) not exceeding 6.0 ppm / ℃; the top and bottom surfaces of the metal composite sheet, which are parallel to the first metallic material layer, are used as the top and bottom surfaces of the grinding wheel substrate (i.e., the top surface of the metal composite sheet is used as the top surface of the grinding wheel substrate and its bottom surface opposite to the top surface is used as the bottom surface of the grinding wheel substrate, or the bottom surface of the metal composite sheet is used as the top surface of the grinding wheel substrate and its bottom surface opposite to the top surface is used as the top surface of the grinding wheel substrate).

[0199] This metal composite sheet adopts an alternating stacked structure of a first metal material layer and a second metal material layer, specifically formed by stacking the first metal material layer / second metal material layer / first metal material layer / second metal material layer / ... / first metal material layer or by stacking the second metal material layer / first metal material layer / second metal material layer / first metal material layer / ... / second metal material layer. Upon heating, the expansion of the first metal material layer and the contraction of the second metal material layer create a self-balancing torque. Therefore, when used as a grinding wheel substrate material, it can effectively solve the CTE mismatch problem between the grinding wheel substrate and the silicon wafer, effectively suppressing overall warpage (approaching zero curvature), thereby avoiding macroscopic end-face runout and microscopic contact fluctuations caused by thermal deformation. This plays a certain role in resisting the phenomenon of grinding force surge and, to some extent, reducing interface damage between the TSV copper pillar and the silicon substrate during wafer thinning, improving the stability of the thinned TSV structure. When used as a grinding wheel substrate material, this metal composite sheet can achieve thermal expansion matching between the grinding wheel substrate and the silicon wafer, and can also improve the stability of the thinned TSV structure to a certain extent, thereby achieving the goal of high precision and low damage in 3D IC thinning.

[0200] Furthermore, the first metallic material layer is made of Cu-W alloy, Mo-Cu alloy, or molybdenum metal.

[0201] Furthermore, the first metal material layer is made of Cu-W alloy material;

[0202] Furthermore, taking the total mass of the Cu-W alloy as 100%, the mass content of Cu in the Cu-W alloy is 20%-15%, and the mass content of W is 80%-85%.

[0203] Furthermore, the second metal material layer is made of Invar alloy material (i.e., Fe). 36 Ni alloy materials), Kovar alloy materials (i.e., Fe) 29 Ni 17 Co alloy materials), Alloy 42 alloy materials (i.e., Fe) 42 Ni alloy materials);

[0204] Furthermore, the second metal material layer is made of Invar alloy material.

[0205] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; the thickness ratio of the first metal material layer to the second metal material layer is (1-2):1 (e.g., 3:2).

[0206] Furthermore, the thickness of the second metal material layer is 0.1-0.5 mm, and the thickness of the first metal material layer is 0.1-0.5 mm.

[0207] Furthermore, the total number of the second metal material layer and the first metal material layer is greater than or equal to 5 and less than 10.

[0208] Furthermore, both the first metal material layer and the second metal material layer are arranged symmetrically with the middle layer of the metal composite sheet as the axis of symmetry.

[0209] Furthermore, both the top and bottom layers of the metal composite sheet are the first metal material layer.

[0210] Furthermore, the interlayer bonding strength between adjacent first and second metal material layers is ≥200 MPa.

[0211] Furthermore, adjacent first metal material layers and second metal material layers are connected by forming a composite interface layer between the first metal material layer and the second metal material layer;

[0212] Furthermore, the first metal material layer is made of Cu-W alloy, and the second metal material layer is made of Invar alloy; adjacent first and second metal material layers are connected by forming a Cu3W2 and γ-FeNi composite interface layer between the first and second metal material layers.

[0213] Furthermore, the Cu3W2 and γ-FeNi composite interface layer sequentially includes a Cu3W2 and Cu solid solution mixed layer, a γ-FeNi and Cu3W2 mixed layer, and a γ-FeNi and FeNi3 mixed layer; wherein, the Cu3W2 and Cu solid solution mixed layer is adjacent to the first metal material layer, and the γ-FeNi and FeNi3 mixed layer is adjacent to the second metal material layer;

[0214] Furthermore, the thickness of the Cu3W2 and Cu solid solution mixed layer is 1-3 μm (e.g., 2 μm); the thickness of the γ-FeNi and Cu3W2 mixed layer is 1-1.5 μm (e.g., 1.2 μm); and the thickness of the γ-FeNi and FeNi3 mixed layer is 1-2 μm (e.g., 1.5 μm).

[0215] Furthermore, the structure of the grinding wheel substrate can be, but is not limited to, the structure of the grinding wheel substrate of an existing wafer thinning grinding wheel.

[0216] Furthermore, the wafer thinning grinding wheel is provided with an adhesive layer and an abrasive layer, and the adhesive layer is used to bond the grinding wheel substrate and the abrasive layer together.

[0217] The adhesive layer may, but is not limited to, use existing adhesive layer materials for wafer thinning grinding wheels. For example, the adhesive layer may use at least one of epoxy resin, polyimide, and phenolic resin.

[0218] The abrasive layer may, but is not limited to, using existing abrasive layer materials for wafer thinning grinding wheels. For example, the abrasive grains of the abrasive layer may be made of at least one of diamond, cubic boron nitride, and silicon carbide.

[0219] Furthermore, the structure of the wafer thinning equipment can be, but is not limited to, the structure of existing wafer thinning equipment equipped with grinding wheels.

[0220] An embodiment of the eighth aspect of the present invention provides a wafer thinning method, which includes wafer thinning using the wafer thinning equipment provided by the seventh aspect of the present invention.

[0221] Furthermore, the wafer thinning method described in this wafer thinning method is 3D IC thinning.

[0222] Example 1

[0223] This embodiment provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for the wafer thinning grinding wheel, and a metal composite sheet.

[0224] The metal composite sheet provided in this embodiment is prepared by the following method:

[0225] (1) Obtain three Cu-W alloy layers with a thickness of 0.3 mm (Cu mass content is 10%, W mass content is 90%) and two Invar alloy layers with a thickness of 0.2 mm; grind the surfaces of each Cu-W alloy layer and Invar alloy layer with 2000-mesh sandpaper until Ra≤0.8μm, then ultrasonically clean with anhydrous ethanol for 15 minutes and dry at 80℃ for later use; wherein, the coefficient of thermal expansion of the Cu-W alloy layer is CTE=5.5×10 -6 / ℃, Invar alloy's coefficient of thermal expansion CTE = 1.2 × 10⁻⁶ -6 / ℃;

[0226] (2) The Cu-W alloy layers and Invar alloy layers obtained in step (1) are stacked alternately in the order of Cu-W alloy layer / Invar alloy layer / Cu-W alloy layer / Invar alloy layer / Cu-W alloy layer, and the total number of Cu-W alloy layers and Invar alloy layers is 5.

[0227] (3) Place the alternately stacked Cu-W alloy layers and Invar alloy layers in a vacuum diffusion welding furnace, and evacuate to a pressure not exceeding 5×10⁻⁶. -4After Pa, the temperature was increased from room temperature to 950℃ at a heating rate of 5℃ / min, and then an axial pressure of 50MPa was applied for 2 hours under heat preservation conditions. The interlayer interface atomic diffusion (bidirectional diffusion) achieved metallurgical bonding of Cu-W alloy layer and Invar alloy layer. The metallurgically bonded product was naturally cooled to 200℃ in the furnace, and inert gas (argon) was introduced and cooled at a cooling rate of 15℃ / min until the furnace temperature dropped to room temperature (25℃) to obtain metal composite sheet.

[0228] The interlayer bonding strength between the Cu-W alloy layer and the Invar alloy layer is ≥200MPa;

[0229] (4) The metal composite sheet prepared in step (3) is finely ground on the end face so that the absolute value of the thickness tolerance does not exceed 0.005 mm and the flatness is ≤3 μm, thereby obtaining the metal composite sheet provided in this embodiment.

[0230] The grinding wheel substrate for wafer thinning provided in this embodiment is prepared using the metal composite sheet provided in this embodiment. The top surface (Cu-W alloy layer) of the metal composite sheet is used as the top surface of the grinding wheel substrate, and the bottom surface (Cu-W alloy layer) opposite to the top surface is used as the bottom surface of the grinding wheel substrate. The structure of the grinding wheel substrate for wafer thinning adopts the structure of a cup-shaped grinding wheel substrate.

[0231] The wafer thinning grinding wheel provided in this embodiment, such as Figure 3 , Figure 4 As shown, a grinding wheel substrate 100 and an adhesive layer ( Figure 3 , Figure 4 (Not shown in the image) Abrasive layer 200; Grinding wheel substrate 100 adopts the grinding wheel substrate of the wafer thinning grinding wheel provided in this embodiment, the adhesive layer is made of epoxy resin, and the abrasive layer 200 is made of diamond; the structure of the wafer thinning grinding wheel adopts a cup-shaped grinding wheel structure. The abrasive layer 200 includes multiple grinding blocks 2001, each grinding block 2001 being a rounded rectangle. Each grinding block 2001 is composed of diamond abrasive grains and a porous ceramic binder. The diamond abrasive grains are the cutting body and perform the grinding function, while the porous ceramic binder serves as a skeleton to fix the diamond abrasive grains. An annular groove is formed in the middle of the annular bottom surface of the grinding wheel substrate 100 along the circumference of the grinding wheel. The grinding blocks 2001 are inserted into the groove of the grinding wheel substrate 100 and arranged at intervals along the circumference of the grinding wheel. The adhesive layer is disposed between the bottom of the annular groove and the grinding blocks 2001 to connect the grinding blocks 2001 to the grinding wheel substrate 100. The preparation method includes the following steps:

[0232] 1. Prepare the metal composite sheet according to the preparation method of the metal composite sheet in this embodiment; then use the grinding wheel substrate 100 of the wafer thinning grinding wheel provided in this embodiment;

[0233] 2. Clean and roughen the mating surfaces of the grinding wheel substrate 100 and the abrasive layer 200 respectively;

[0234] 3. Apply epoxy resin adhesive evenly to the mating surface of the grinding wheel substrate 100;

[0235] 4. Preheat and gel the coated grinding wheel substrate 100, and then align and bond the abrasive layer 200.

[0236] 5. Under a pressure of 0.5-1.0MPa, the adhesive is fully cured by a step-by-step heating program, specifically by heating to 80℃ and holding at 80℃ for 2 hours, then heating to 120℃ and holding at 120℃ for 4 hours;

[0237] 6. After the furnace is naturally cooled to room temperature, the wafer thinning grinding wheel is obtained after the pressure is released.

[0238] The structure of the wafer thinning equipment provided in this embodiment is as follows: Figure 1 , Figure 2 As shown, it includes a grinding device 2 and an adsorption platform 3. The adsorption platform 3 is used to support the wafer and drive the wafer to rotate. The grinding device 2 is raised and lowered above the adsorption platform 3. The lower part of the grinding device 2 has a grinding wheel 23 that can rotate circumferentially to grind the back of the wafer.

[0239] The grinding wheel 23 is the wafer thinning grinding wheel provided in this embodiment.

[0240] The grinding device 2 includes a feed assembly 21, a rotating shaft 22, and a grinding wheel 23. The grinding block 232 in the grinding wheel 23 is used to grind the wafer. The grinding wheel 23 is mounted at the lower end of the rotating shaft 22. The rotating shaft 22 is used to rotate the grinding wheel 23 around its axis of rotation. The feed assembly 21 can drive the rotating shaft 22 and the grinding wheel 23 to move up and down synchronously. When the wafer needs grinding, the grinding wheel 23 moves down to its bottom surface and contacts the back side of the wafer under the drive of the feed assembly 21. At this time, both the grinding wheel 23 and the wafer are rotating in the same direction but at different speeds. The grinding wheel 23 is used to grind the back side of the wafer. The feed assembly 21 includes a linear guide that guides the movement direction of the rotating shaft 22 and a ball screw-slider mechanism that moves the rotating shaft 22 up and down.

[0241] The adsorption platform 3 has a chuck spindle 31, a worktable 32, and an adsorption disk 33. The chuck spindle 31 moves along the axis of rotation. The adsorption disk 33, made of porous alumina material, is embedded in the upper surface of the worktable 32. The adsorption platform 3 has a conduit that penetrates its interior and extends to its surface. The conduit is connected to a vacuum source, a compressed air source, or a water supply source via a rotary joint. When the vacuum source is activated, the wafer placed on the adsorption platform 3 is adsorbed by the adsorption disk 33. When the compressed air source or water supply source is activated, the adsorption between the wafer and the adsorption disk 33 is released. The adsorption platform 3 is provided with a tilting device that tilts relative to the grinding wheel 23, and the grinding device 2 is provided with a tilting structure that tilts the rotation axis 22. Thus, the contact between the grinding wheel 23 and the wafer can be adjusted to grind the wafer into the desired shape.

[0242] The operation of the grinding device 2 is controlled by a control device. The control device controls each component of the grinding device 2. The control device includes a CPU, memory, etc. The functions of the control device can be implemented through software control or hardware operation. The control device can control the movement of the feed assembly 21, the rotary axis 22, and the chuck spindle 31 according to preset grinding process parameters, such as feed rate and rotational speed, to achieve an automated grinding process. Simultaneously, the control device also has fault diagnosis and alarm functions, capable of monitoring the operating status of each part of the equipment in real time. When abnormalities occur, it promptly issues alarms and takes corresponding protective measures to ensure the safety of the equipment and operators. In this embodiment, the control device used in existing wafer thinning equipment for controlling the operation of the grinding device can be employed.

[0243] The wafer thinning method provided in this embodiment thins a wafer formed by bonding two 775μm wafers, aiming to reduce the upper (to be thinned) wafer to 10μm. While keeping the bottom wafer thickness constant at 775μm, the total thickness of the bonded wafer will decrease from the initial 1550μm to 785μm. Specifically, it includes:

[0244] First, a coarse grinding wafer thinning device (the only difference from the wafer thinning device provided in this embodiment of the application is that the grinding wheel is a coarse grinding wheel) is used to coarsely grind and thin the stacked wafers; wherein, the coarse grinding wheel and the adsorption platform (i.e., the platform used to adsorb and fix the wafer to be processed) rotate in the same direction, the rotation speed of the coarse grinding wheel is 4800 rpm, and the rotation speed of the adsorption platform is 300 rpm; while the coarse grinding wheel is rotating, it is fed downwards at feed speeds of 5μm / s, 4μm / s, and 3μm / s in sequence; the flow rate of cooling water during the grinding process is 4L / min;

[0245] After rough grinding to a total thickness of 825 μm for the stacked wafers, fine grinding is performed using the wafer thinning equipment provided in this embodiment. The grinding wheel and the adsorption platform (i.e., the platform used to adsorb and fix the wafers to be processed) rotate in the same direction. The grinding wheel rotates at 4800 rpm, and the adsorption platform rotates at 300 rpm. While rotating, the grinding wheel is fed downwards sequentially at feed rates of 0.5 μm / s, 0.4 μm / s, and 0.3 μm / s. The cooling water flow rate during grinding is 4 L / min.

[0246] After the grinding process reduces the total thickness of the stacked wafers to 785μm, the grinding wheel and adsorption platform stop rotating. The feed assembly then moves the grinding wheel upwards until it separates from the wafer. The adsorption platform releases the wafer from the wafer, and the wafer is transferred for testing.

[0247] The specific operation process for wafer thinning is as follows: Figure 9 As shown, it includes:

[0248] A100. Vacuum adsorption fixes the wafer onto the adsorption platform.

[0249] In this embodiment, before performing the wafer thinning operation, the surface of the adsorption platform 3 is wiped clean with a lint-free cloth dampened with an appropriate amount of alcohol to ensure that the surface of the adsorption platform 3 is clean and free of impurities, so as to avoid impurities affecting the adsorption effect and grinding quality of the wafer. The wafer to be thinned is placed on the adsorption platform 3 using a vacuum suction pen, ensuring that the center of the wafer is aligned with the center of the adsorption platform 3. The vacuum source connected to the adsorption platform 3 is activated by the control device. The porous structure inside the adsorption platform 3 forms a negative pressure under the action of vacuum, adsorbing the wafer onto its surface. To ensure a firm adsorption, the vacuum degree of the adsorption platform 3 is monitored in real time by the control device. When the vacuum degree reaches a preset value, it indicates that the wafer has been stably adsorbed and the next operation can be carried out.

[0250] A200, the grinding wheel moves down to contact the back side of the wafer under the drive of the feed assembly.

[0251] In this embodiment, the control feed assembly 21 drives the rotating shaft 22 and the grinding wheel 23 to move vertically downwards until the grinding surface of the grinding wheel contacts the back side of the wafer. Specifically, the target position parameter of the grinding wheel 23 is input into the control device. This parameter is determined based on factors such as the wafer thickness, grinding allowance, and the initial position of the grinding wheel 23. The control device sends a command to the feed assembly 21 to precisely control the movement direction of the feed assembly 21, ensuring that it moves vertically downwards. The feed assembly 21 drives the grinding wheel 23 to move downwards smoothly at a set speed. During the movement, the control device monitors the position information of the feed assembly 21 in real time and compares it with the preset target position. When it approaches the target position, the feed speed is reduced to achieve precise alignment.

[0252] The A300, grinding wheel, and adsorption platform rotate in the same direction, while the grinding wheel feeds downwards to grind the back side of the wafer as it rotates.

[0253] In this embodiment, the grinding wheel 23 and the adsorption platform 3 rotate in the same direction, while the grinding wheel 23 is fed downwards. The rotational speed of the grinding wheel 23 is greater than that of the adsorption platform 3 to grind the back side of the wafer. Specifically, the control device starts the grinding wheel 23 and the adsorption platform 3 at the same time. The grinding wheel 23 rotates at a set speed, while the adsorption platform 3 and the wafer adsorbed on it rotate in the same direction at a relatively low speed. After the grinding wheel 23 and the adsorption platform 3 reach a stable rotational state, the control device continues to control the feed assembly 21 to feed the grinding wheel 23 to the back side of the wafer to grind the wafer surface.

[0254] A400: Once the wafer has been ground to the target thickness, stop the rotation and feed of the grinding wheel and the adsorption platform, and move the grinding wheel upwards to reset and detach it from the wafer surface.

[0255] In this embodiment, a non-contact thickness sensor installed near the grinding wheel 23 is used to continuously monitor the thickness change of the wafer. When the thickness data received by the control device shows that the wafer has been ground to the target thickness, the grinding is determined to be complete. After the wafer is ground to the target thickness, the grinding wheel 23 and the adsorption platform 3 stop rotating. Subsequently, the control device starts the feed assembly 21 to drive the grinding wheel 23 to move upward at a set speed, so that the grinding wheel 23 is quickly separated from the wafer, avoiding unnecessary damage caused by prolonged contact between the grinding wheel 23 and the wafer surface after the grinding wheel stops rotating.

[0256] A500 releases the vacuum adsorption of the wafer by the adsorption platform and transfers the wafer.

[0257] In this embodiment, the control device shuts off the vacuum source and switches to a compressed air source or a water source; compressed air or water enters the adsorption platform 3, disrupting the negative pressure state between the adsorption platform 3 and the wafer, thereby releasing the adsorption force; using a vacuum pen or other precision gripping tool, the thinned wafer is removed from the adsorption platform 3, completing the entire wafer thinning process.

[0258] The results are as follows Figure 6 , Figure 7 As shown in Table 1.

[0259] Comparative Example 1

[0260] This comparative example provides a wafer thinning device, two wafer thinning methods, a wafer thinning grinding wheel, and a grinding wheel substrate for the wafer thinning grinding wheel.

[0261] The difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this comparative example and the grinding wheel substrate of the wafer thinning grinding wheel provided in Example 3 is that the material is aluminum alloy.

[0262] The difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the grinding wheel substrate of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0263] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0264] The difference between the first wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 lies only in the use of the wafer thinning equipment provided in this comparative example. The results are as follows... Figure 6 , Figure 8 .

[0265] Depend on Figure 6 , Figure 8 It can be seen that using the technical solution provided in Example 1 for ultra-thin (<50µm) wafer thinning achieves a reduction in edge jump and TTV. Specifically, using the technical solution provided in Example 1 for ultra-thin (<50µm) wafer thinning results in edge jump of <3µm and TTV of less than 1µm. Under the same conditions, using the technical solution provided in Comparative Example 1 for ultra-thin (<50µm) wafer thinning results in edge jump of approximately 10µm and TTV of approximately 1.5µm.

[0266] The wafer thinning method provided in this comparative example differs from that in Example 1 only in that it is performed using the wafer thinning equipment provided in this comparative example. The results are shown in Table 2.

[0267] Comparative Example 2

[0268] This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer grinding wheel substrate for the wafer thinning grinding wheel.

[0269] The difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this comparative example and the grinding wheel substrate of the wafer thinning grinding wheel provided in Example 1 is that the material used is a Cu-W alloy with a thickness of 1.5 mm (the same composition as the Cu-W alloy in Example 1).

[0270] The difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the grinding wheel substrate of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0271] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0272] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 is only that the wafer thinning equipment provided in this comparative example is used. The results are shown in Table 1.

[0273] Comparative Example 3

[0274] This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer grinding wheel substrate for the wafer thinning grinding wheel.

[0275] The difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this comparative example and the grinding wheel substrate of the wafer thinning grinding wheel provided in Example 1 is that the material used is an Invar alloy with a thickness of 1.5 mm (the same composition as the Invar alloy in Example 1).

[0276] The difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the grinding wheel substrate of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0277] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0278] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 is only that the wafer thinning equipment provided in this comparative example is used. The results are shown in Table 1.

[0279] Comparative Example 4

[0280] This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for a wafer thinning grinding wheel, and a metal composite sheet.

[0281] The only difference between the metal composite sheet provided in this comparative example and the metal composite sheet provided in Example 1 is that:

[0282] The following method was used to prepare four Cu-W alloy layers and one Invar alloy layer, with each Cu-W alloy layer and Invar alloy layer being stacked alternately in the manner of Cu-W alloy layer / Invar alloy layer / Cu-W alloy layer / Cu-W alloy layer / Cu-W alloy layer / Cu-W alloy layer.

[0283] The only difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this comparative example and the grinding wheel substrate of the wafer thinning grinding wheel provided in Example 1 is that the material used is the metal composite sheet provided in this comparative example.

[0284] The difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the grinding wheel substrate of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0285] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0286] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 is only that the wafer thinning equipment provided in this comparative example is used. The results are shown in Table 1.

[0287] Comparative Example 5

[0288] This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for a wafer thinning grinding wheel, and a metal composite sheet.

[0289] The only difference between the metal composite sheet provided in this comparative example and the metal composite sheet provided in Example 1 is that (3) is not performed, but instead a bolt connection is used instead of diffusion welding.

[0290] The only difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this comparative example and the grinding wheel substrate of the wafer thinning grinding wheel provided in Example 1 is that the material used is the metal composite sheet provided in this comparative example.

[0291] The difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the grinding wheel substrate of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0292] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0293] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 is only that the wafer thinning equipment provided in this comparative example is used. The results are shown in Table 1.

[0294] Table 1

[0295]

[0296] Example 2

[0297] This embodiment provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for the wafer thinning grinding wheel, and a metal composite sheet.

[0298] The difference between the metal composite sheet provided in this embodiment and the metal composite sheet provided in Embodiment 1 is as follows:

[0299] Preparation step (3) involves a different diffusion welding method, specifically: alternating Cu-W alloy layers and Invar alloy layers are placed in a vacuum diffusion welding furnace, and a vacuum is drawn until the pressure does not exceed 5×10⁻⁶. -4 After Pa, the temperature is increased from room temperature to 850℃ at a heating rate of 5℃ / min. Then, under holding conditions, a sinusoidal axial pressure with a frequency of 10Hz, a trough pressure of 30MPa, and a peak pressure of 50MPa is applied for 1 hour. Atomic interdiffusion occurs between the Cu-W alloy layer and the Invar alloy layer to form a transition layer (typically about 5μm thick). The temperature is then further increased to 920℃ at a heating rate of 5℃ / min, and then under holding conditions, a sinusoidal axial pressure with a frequency of 10Hz, a trough pressure of 30MPa, and a peak pressure of 50MPa is applied for 1 hour. A sinusoidal axial pressure of 50 MPa for 40 minutes triggered an in-situ reaction, generating a metastable Cu3W2 phase (enhancing hardness) and a tough γ-FeNi phase (improving buffering capacity), forming a Cu3W2 and γ-FeNi composite interface layer, achieving metallurgical bonding between the Cu-W alloy layer and the Invar alloy layer; the metallurgically bonded product was naturally cooled to 200°C in the furnace, and then naturally cooled at a cooling rate of 15°C / min until the furnace temperature dropped to 25°C, yielding a metal composite sheet;

[0300] The metal composite sheet provided in this embodiment connects adjacent Cu-W alloy layers and Invar alloy layers by forming a Cu3W2 and γ-FeNi composite interface layer between the Cu-W alloy layer and the Invar alloy layer. The Cu3W2 and γ-FeNi composite interface layer sequentially includes a Cu3W2 and Cu solid solution mixed layer, a γ-FeNi and Cu3W2 mixed layer, and a γ-FeNi and FeNi3 mixed layer. The Cu3W2 and Cu solid solution mixed layer is adjacent to the Cu-W alloy layer, and the γ-FeNi and FeNi3 mixed layer is adjacent to the Invar alloy layer. The thickness of the Cu3W2 and Cu solid solution mixed layer is approximately 2 μm; the thickness of the γ-FeNi and Cu3W2 mixed layer is approximately 1.2 μm; and the thickness of the γ-FeNi and FeNi3 mixed layer is approximately 1.5 μm.

[0301] The only difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this embodiment and the grinding wheel substrate of the wafer thinning grinding wheel provided in Embodiment 1 is that the material used is the metal composite sheet provided in this embodiment.

[0302] The difference between the wafer thinning grinding wheel provided in this embodiment and the wafer thinning grinding wheel provided in Embodiment 1 is only that the grinding wheel substrate of the wafer thinning grinding wheel uses the grinding wheel substrate of the wafer thinning grinding wheel provided in this embodiment. For the specific structure, please refer to [link / reference]. Figure 5 As shown.

[0303] The only difference between the wafer thinning equipment provided in this embodiment and the wafer thinning equipment provided in Embodiment 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this embodiment.

[0304] The wafer thinning method provided in this embodiment differs from the wafer thinning method provided in Embodiment 1 only in that the wafer thinning equipment provided in this embodiment is used. The results are shown in Tables 2 and 3.

[0305] Table 2

[0306]

[0307] As shown in Table 2, the technical solution provided in Example 2 can effectively suppress the peak value of single grinding stress, reduce the risk of copper pillar collapse / cracks in the TSV dense area by more than 60%, and improve the yield to 95%.

[0308] Comparative Example 6

[0309] This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for a wafer thinning grinding wheel, and a metal composite sheet.

[0310] The difference between the metal composite sheet provided in this comparative example and the metal composite sheet provided in Example 2 is that the number of Cu-W alloy layers is 4 and the number of Invar alloy layers is 1.

[0311] The difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this comparative example and the grinding wheel substrate of the wafer thinning grinding wheel provided in Example 2 is that the material used is the metal composite sheet provided in this example.

[0312] The difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 2 is that the grinding wheel substrate of the wafer thinning grinding wheel adopts the grinding wheel substrate of the wafer thinning grinding wheel provided in this example.

[0313] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 2 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this example.

[0314] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 2 is only that the wafer thinning equipment provided in this comparative example is used. The results are shown in Table 3.

[0315] Comparative Example 7

[0316] This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for a wafer thinning grinding wheel, and a metal composite sheet.

[0317] The difference between the metal composite sheet provided in this comparative example and the metal composite sheet provided in Example 2 is that the number of Cu-W alloy layers is 5 and the number of Invar alloy layers is 0. The Cu-W alloy layers are stacked instead of stacking the Cu-W alloy layers and Invar alloy layers in the order of Cu-W alloy layer / Invar alloy layer / Cu-W alloy layer / Cu-W alloy layer / Cu-W alloy layer / Cu-W alloy layer.

[0318] The difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this comparative example and the grinding wheel substrate of the wafer thinning grinding wheel provided in Example 2 is that the material used is the metal composite sheet provided in this example.

[0319] The difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 2 is that the grinding wheel substrate of the wafer thinning grinding wheel adopts the grinding wheel substrate of the wafer thinning grinding wheel provided in this example.

[0320] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 2 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this example.

[0321] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 2 is only that the wafer thinning equipment provided in this comparative example is used. The results are shown in Table 3.

[0322] Example 3

[0323] This embodiment provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for the wafer thinning grinding wheel, and a metal composite sheet.

[0324] The difference between the metal composite sheet provided in this embodiment and the metal composite sheet provided in Embodiment 2 is as follows:

[0325] Preparation step (3) involves a different diffusion welding method, specifically: alternating Cu-W alloy layers and Invar alloy layers are placed in a vacuum diffusion welding furnace, and a vacuum is drawn until the pressure does not exceed 5×10⁻⁶. -4After Pa, the temperature is increased from room temperature to 920℃ at a heating rate of 5℃ / min, and then an axial pressure of 40MPa is applied for 100min under heat preservation conditions. The interlayer atomic diffusion (bidirectional diffusion) achieves metallurgical bonding between the Cu-W alloy layer and the Invar alloy layer. The metallurgically bonded product is naturally cooled to 200℃ in the furnace, and then cooled at a cooling rate of 15℃ / min until the furnace temperature drops to 25℃ to obtain a metal composite sheet. The interlayer bonding strength between the Cu-W alloy layer and the Invar alloy layer is ≥200MPa.

[0326] The only difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this embodiment and the grinding wheel substrate of the wafer thinning grinding wheel provided in Embodiment 2 is that the material used is the metal composite sheet provided in this embodiment.

[0327] The difference between the wafer thinning grinding wheel provided in this embodiment and the wafer thinning grinding wheel provided in Embodiment 2 is that the grinding wheel substrate of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this embodiment.

[0328] The difference between the wafer thinning equipment provided in this embodiment and the wafer thinning equipment provided in Embodiment 2 is only that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this embodiment.

[0329] The difference between the wafer thinning method provided in this embodiment and the wafer thinning method provided in Embodiment 2 lies only in the use of the wafer thinning equipment provided in this comparative example. The results are shown in Table 3.

[0330] Example 4

[0331] This embodiment provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, an adhesive layer grinding wheel substrate for the wafer thinning grinding wheel, and a metal composite sheet.

[0332] The difference between the metal composite sheet provided in this embodiment and the metal composite sheet provided in Embodiment 2 is as follows:

[0333] The method of applying pressure in preparation step (3) is different. An axial pressure of 40 MPa is applied instead of a sinusoidal axial pressure with a frequency of 10 Hz, a trough pressure of 30 MPa, and a peak pressure of 50 MPa.

[0334] The only difference between the grinding wheel substrate of the wafer thinning grinding wheel provided in this embodiment and the grinding wheel substrate of the wafer thinning grinding wheel provided in Embodiment 2 is that the material used is the metal composite sheet provided in this embodiment.

[0335] The difference between the wafer thinning grinding wheel provided in this embodiment and the wafer thinning grinding wheel provided in Embodiment 2 is that the grinding wheel substrate of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this embodiment.

[0336] The difference between the wafer thinning equipment provided in this embodiment and the wafer thinning equipment provided in Embodiment 2 is only that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this embodiment.

[0337] The difference between the wafer thinning method provided in this embodiment and the wafer thinning method provided in Embodiment 2 lies only in the use of the wafer thinning equipment provided in this comparative example. The results are shown in Table 3.

[0338] Table 3

[0339]

[0340] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wafer thinning device, characterized in that, The wafer thinning device comprises a grinding wheel for wafer thinning, which is installed on a grinding shaft of the wafer thinning device, and comprises a grinding wheel base, an adhesive layer and an abrasive layer, wherein the abrasive layer is fixed to the grinding wheel base through the adhesive layer; The grinding wheel base is made of a metal composite sheet; The metal composite sheet is formed by alternately stacking a first metal material layer and a second metal material layer, the number of layers of the first metal material layer and the second metal material layer is an odd number, and adjacent first metal material layers and second metal material layers are connected by a metallurgical bonding method; wherein the first metal material layer is made of an alloy material or a metal material with a coefficient of thermal expansion CTE of not more than 10 ppm / ℃ and a thermal conductivity of not less than 130 W / m·K; and the second metal material layer is made of an iron-nickel-based alloy material with a coefficient of thermal expansion CTE of not more than 6.0 ppm / ℃. The top and bottom surfaces of the metal composite sheet, which are oppositely arranged and parallel to the first metal material layer, are used as the top and bottom surfaces of the grinding wheel base.

2. The wafer thinning device according to claim 1, wherein The first metal material layer is made of a Cu-W alloy material, a Mo-Cu alloy material or a molybdenum metal material; The second metal material layer is made of an Invar alloy material, a Kovar alloy material or an Alloy 42 alloy material.

3. The wafer thinning device according to claim 2, wherein The first metal material layer is made of a Cu-W alloy material; The second metal material layer is made of an Invar alloy material.

4. The wafer thinning apparatus according to claim 3, wherein The mass content of Cu in the Cu-W alloy is 20%-15%, and the mass content of W is 80%-85%, based on the total mass of the Cu-W alloy being 100%.

5. The wafer thinning apparatus according to claim 3, wherein The first metal material layer is made of a Cu-W alloy material, and the second metal material layer is made of an Invar alloy material; the thickness ratio of the first metal material layer to the second metal material layer is (1-2):

1.

6. The wafer thinning apparatus of claim 1, wherein The thickness of the second metal material layer is 0.1-0.5 mm, and the thickness of the first metal material layer is 0.1-0.5 mm.

7. The wafer thinning apparatus of claim 1, wherein The number of layers of the first metal material layer and the second metal material layer is greater than or equal to 5 and less than 10.

8. The wafer thinning apparatus of claim 1, wherein, The metal composite sheet comprises a first sub-layer, a second sub-layer and an Nth sub-layer from bottom to top, the ith sub-layer and the N-i+1 sub-layer are symmetrical with respect to the (N+1)÷2 sub-layer; wherein i is a natural number not less than 1 and not greater than N.

9. The wafer thinning apparatus of claim 1, wherein, The interlayer bonding strength of adjacent first metal material layers and second metal material layers is ≥200 Mpa.

10. The wafer thinning apparatus of claim 1, wherein Adjacent first metal material layers and second metal material layers are connected by forming a composite interface layer between the first metal material layer and the second metal material layer.

11. The wafer thinning apparatus of claim 1, wherein The first metal material layer is made of a Cu-W alloy material, and the second metal material layer is made of an Invar alloy material; adjacent first metal material layers and second metal material layers are connected by forming a Cu3W2 and γ-FeNi composite interface layer between the first metal material layer and the second metal material layer.

12. The wafer thinning apparatus of claim 11, wherein, The Cu3W2 and gamma-FeNi composite interface layer comprises, in sequence, a Cu3W2 and Cu solid solution mixed layer, a gamma-FeNi and Cu3W2 mixed layer, and a gamma-FeNi and FeNi3 mixed layer; wherein the Cu3W2 and Cu solid solution mixed layer is immediately adjacent to the first metal material layer, and the gamma-FeNi and FeNi3 mixed layer is immediately adjacent to the second metal material layer.

13. The wafer thinning apparatus of claim 12, wherein, The thickness of the Cu3W2 and Cu solid solution mixed layer is 1-3 mu m; the thickness of the gamma-FeNi and Cu3W2 mixed layer is 1-1.5 mu m; and the thickness of the gamma-FeNi and FeNi3 mixed layer is 1-2 mu m.

14. The wafer thinning apparatus of claim 1, wherein, The grinding wheel for wafer thinning is provided with a glue layer and an abrasive layer, and the glue layer is arranged between the grinding wheel base body and the abrasive layer. The glue layer is made of at least one of epoxy resin, polyimide and phenolic resin. The abrasive grains of the abrasive layer are made of at least one of diamond, cubic boron nitride and silicon carbide.

15. A wafer thinning method, characterized by, The wafer thinning method comprises using the wafer thinning device of any one of claims 1-14 to perform wafer thinning.

16. The wafer thinning method of claim 15, wherein, Wafer thinning refers to ultra-thinning of a 3D IC wafer, and ultra-thinning refers to thinning the wafer to a thickness of not more than 50 mu m.

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