Cutting method of metal substrate wafer

Abstract

The invention discloses a method for cutting a metal substrate wafer, which relates to the technical field of semiconductors and comprises the following steps of: evaporating a metal material on the back surface of the metal substrate wafer to form a first cutting protection layer; spin-coating water-soluble cutting protection liquid on the first cutting protection layer, and drying to form a second cutting protection layer; cutting the second cutting protection layer by adopting a first laser beam to form a first groove; continuously cutting along the position of the first groove by adopting a second laser beam to form a second groove; and cleaning and removing the second cutting protection layer so as to complete back cutting of the metal substrate wafer. Through mutual cooperation of the first cutting protection layer and the second cutting protection layer and step-by-step laser cutting, scraps, slag and the like can be effectively prevented from remaining on the edges of the core particles, the generation range of a heat affected zone can be effectively reduced, and the cutting yield of the metal substrate wafer and the packaging yield of the core particles can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for cutting a metal substrate wafer. Background Art

[0002] In the back-end cutting process of metal substrate wafers, laser is usually used to directly cut the metal substrate wafer. However, when cutting the back side of the metal substrate wafer, that is, the metal substrate, due to the high mechanical strength of the metal substrate, the power parameter of the laser cutting machine used is set to a large value, which easily generates debris and slag at the edge of the core particle, thus causing burrs ( Figure 1 A schematic diagram of the cutting effect of an existing cutting method for a metal substrate wafer is shown), which will affect the cutting yield of the metal substrate wafer; moreover, the metal substrate wafer will generate a large amount of heat during the laser cutting process, and it is easy to form a heat-affected zone in the range of about 100 to 200 μm around the cutting path, that is, a heat-affected zone of about 100 to 200 μm is formed at the edge of the core particle. The range of the heat-affected zone is too large, resulting in the expansion of the uneven area on the side surface of the metal substrate of the core particle. When the core particle is packaged on a board, the expanded uneven area is likely to cause solid crystal voids, which will affect the packaging yield of the core particle. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art. The present invention provides a method for cutting metal substrate wafers. Through the mutual cooperation of a first cutting protective layer and a second cutting protective layer, and laser cutting is performed in steps, it can not only effectively prevent debris, slag, etc. from remaining on the edge of the core particle, but also effectively reduce the scope of the heat affected zone, which can significantly improve the cutting yield of the metal substrate wafer and improve the packaging yield of the core particle.

[0004] The present invention provides a method for cutting a metal substrate wafer, comprising the following steps: S1, evaporating a metal material on the back side of the metal substrate wafer to form a first cutting protection layer; S2, spin coating a water-soluble cutting protection liquid on the first cutting protection layer, and forming a second cutting protection layer after drying; S3, using a first laser beam to cut and form a first groove on the second cutting protection layer, wherein the first groove extends from a surface of the second cutting protection layer to a surface of the metal substrate wafer; S4, using a second laser beam to continue cutting along the position of the first groove to form a second groove, wherein the second groove extends from the surface of the metal substrate wafer to the inside of the metal substrate wafer; S5. Clean and remove the second cutting protection layer, thereby completing the back side cutting of the metal substrate wafer.

[0005] Specifically, the first cutting protection layer includes a bottom metal layer, a middle metal layer and a surface metal layer which are sequentially vapor-deposited on the back side of the metal substrate wafer, the bottom metal layer is made of Cr or Ti, the middle metal layer is one or more of a Ti layer, a Ni layer, an Al layer, and a Pt layer, and the surface metal layer is one or more of an Au layer, a Sn layer, and an AuSn layer.

[0006] Specifically, the thickness of the first cutting protection layer is in the range of 2000 to 5000 nm.

[0007] Specifically, in parts by weight, the components of the water-soluble cutting protection liquid include 20 to 50 parts of water-soluble resin, 5 to 15 parts of azeotropic solvent, 5 to 20 parts of polyol, 0.1 to 2 parts of water-soluble ultraviolet absorber, 0.05 to 0.1 parts of water-soluble antioxidant, 0.1 to 2 parts of pH adjuster, 0.05 to 0.1 parts of anti-corrosion agent and 30 to 60 parts of deionized water.

[0008] Specifically, the thickness of the second cutting protection layer is in the range of 5000 to 10000 nm.

[0009] Specifically, the power range of the first laser beam is 3-5 W, the frequency range of the first laser beam is 80-100 kHz, and the cutting speed range of the first laser beam is 200-300 mm / s.

[0010] Specifically, the power range of the second laser beam is 8-10 W, the frequency range of the second laser beam is 120-150 kHz, and the cutting speed range of the second laser beam is 250-350 mm / s.

[0011] Specifically, the thickness of the first cutting protection layer is h 1 , the thickness of the second cutting protection layer is h 2 , the depth of the first groove is H 1 , the width of the first groove is W 1 , then it satisfies: h 1 +h 2 ≤H 1 ≤1.1*(h 1 +h 2 )、10000nm≤W 1 ≤20000nm.

[0012] Specifically, the thickness of the metal substrate wafer is h 3 , the depth of the second groove is H 2 , the width of the second groove is W 2 , then it satisfies: 0.5*h3 ≤H 2 ≤0.8*h 3 , 0.8*W 1 ≤W 2 ≤1.2*W 1 .

[0013] Specifically, a plurality of chip units are formed on the front side of the metal substrate wafer, and the plurality of chip units are separated based on a cutting isolation wall, and there is a gap between the cutting isolation wall and the chip units; The first groove and the second groove both correspond to the position of the cutting isolation wall, and the notch width of the first groove and the notch width of the second groove are both smaller than the width of the cutting isolation wall.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The cutting method of the metal substrate wafer of the present invention forms a first cutting protection layer by evaporating a metal material on the back side of the metal substrate wafer. The first cutting protection layer made of metal material can not only absorb the energy of beams of different powers and different cutting rates, but also effectively transfer cutting heat to avoid excessive heat concentration, thereby effectively reducing the range of heat affected zone; then, a water-soluble cutting protection liquid is spin-coated on the first cutting protection layer to form a second cutting protection layer. The second cutting protection layer has the functions of protecting the surface of the metal substrate wafer and absorbing cutting debris and slag, and has good thermal conductivity; since the second cutting protection layer is formed by a water-soluble cutting protection liquid, it can be removed cleanly by washing with water, and the adsorbed cutting debris and slag can be removed at the same time, thereby effectively preventing debris, slag, etc. from remaining on the edge of the core particle; the first cutting protection layer and the second cutting protection layer can form a dual thermal conductivity effect, further transfer cutting heat, avoid excessive heat concentration, thereby effectively reducing the range of heat affected zone.

[0015] Moreover, the first laser beam is used to cut the first groove in the first cutting protection layer and the second cutting protection layer, and then the second laser beam is used to cut along the position of the first groove to form the second groove. This can fully exert the functional role of the first cutting protection layer and the second cutting protection layer: when cutting to form the second groove, due to the dual heat conduction effect of the first cutting protection layer and the second cutting protection layer, the first groove can exert a strong heat conduction effect, which can effectively speed up the heat transfer speed when the second laser beam cuts the metal substrate wafer, thereby effectively reducing the range of the heat affected zone; moreover, when cutting to form the second groove, the second cutting protection layer can effectively absorb cutting debris and slag.

[0016] Therefore, through the mutual cooperation of the first cutting protection layer and the second cutting protection layer, and performing laser cutting in steps, on the one hand, it can effectively prevent debris, slag, etc. from remaining on the edge of the core particle, avoid the problem of burrs on the core particle, thereby effectively improving the cutting yield of the metal substrate wafer; on the other hand, it can effectively reduce the scope of the heat-affected zone, avoid the expansion of the uneven area on the side surface of the core particle metal substrate, which is beneficial to reduce the risk of solid crystal voids when packaging the core particle, thereby effectively improving the packaging yield of the core particle. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the cutting effect of the existing cutting method of the metal substrate wafer; Figure 2 is a schematic flow chart of a method for cutting a metal substrate wafer in an embodiment of the present invention; Figure 3 2 is a schematic diagram of the structure of the first cutting protection layer and the second cutting protection layer in an embodiment of the present invention; Figure 4 is a schematic structural diagram of a first groove in an embodiment of the present invention; Figure 5 is a schematic structural diagram of a second groove in an embodiment of the present invention; Figure 6 is a schematic structural diagram of the front side of a metal substrate wafer in an embodiment of the present invention; Figure 7 is a schematic diagram of the cross-sectional structure of a metal substrate wafer in an embodiment of the present invention; Figure 8 is a schematic structural diagram of a third groove in an embodiment of the present invention; Fig. 9 is a schematic diagram of the cutting effect of Example 1; Fig.10 is a schematic diagram of the cutting effect of Example 2; Fig.11 is a schematic diagram of the cutting effect of Example 3; Fig.12 is a schematic diagram of the cutting effect of Example 4; Fig.13 is a schematic diagram of the cutting effect of Example 5; Fig.14 It is a schematic diagram of the cutting effect of comparative example 1.

[0019] In the accompanying drawings, 100 is a metal substrate wafer; 110 is a chip unit; 120 is a cutting isolation wall; 200 is a first cutting protection layer; 300 is a second cutting protection layer; 400 is a first groove; 500 is a second groove; and 600 is a third groove. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present invention provides a method for cutting a metal substrate wafer 100. Figure 2 A schematic flow chart of a method for cutting a metal substrate wafer in an embodiment of the present invention is shown, comprising the following steps: S1, evaporating a metal material on the back side of the metal substrate wafer to form a first cutting protection layer; Figure 3 A schematic diagram of the structure of the first cutting protection layer and the second cutting protection layer in an embodiment of the present invention is shown.

[0022] The first cutting protection layer 200 made of metal material can not only absorb the energy of beams of different powers and cutting rates, but also effectively transfer cutting heat to avoid excessive heat concentration, thereby effectively reducing the range of heat-affected zones.

[0023] In some specific embodiments, the first cutting protection layer 200 includes a bottom metal layer, a middle metal layer and a surface metal layer which are sequentially vapor-deposited on the back side of the metal substrate wafer 100, the bottom metal layer is made of Cr or Ti, and can effectively adhere to the metal substrate wafer 100; the middle metal layer is one or more of a Ti layer, a Ni layer, an Al layer, and a Pt layer, and the surface metal layer is one or more of an Au layer, a Sn layer, and an AuSn layer, the middle metal layer and the surface metal layer cooperate with each other, which not only ensures the thermal conductivity during cutting, but also meets the welding requirements of the core particles; the bottom metal layer, the middle metal layer and the surface metal layer cooperate with each other, have the function of absorbing beam energy of different powers and different cutting rates, and effectively transferring cutting heat, thereby effectively avoiding the problem of peeling of the cutting protection layer caused by heat accumulation when cutting the metal substrate wafer 100.

[0024] Preferably, the material of the bottom metal layer is Cr, the middle metal layer is a stacked structure of Ti layer, Ni layer, Al layer and Pt layer, and the surface metal layer is a stacked structure of Au layer, Sn layer and AuSn layer, which has good thermal conductivity and high structural stability, and can effectively resist the thermal stress caused by the drastic instantaneous temperature change during cutting.

[0025] In some specific embodiments, the thickness of the first cutting protection layer 200 ranges from 2000 to 5000 nm. The appropriate thickness is the basis for the first cutting protection layer 200 to absorb beam energy of different powers and different cutting rates and effectively transfer cutting heat. Moreover, the appropriate thickness is conducive to cost control.

[0026] Optionally, the thickness of the first cutting protection layer 200 may be 2000 nm, 3000 nm, 4000 nm, or 5000 nm.

[0027] S2, spin coating a water-soluble cutting protection liquid on the first cutting protection layer, and forming a second cutting protection layer after drying; For the structure of the second cutting protection layer 300, please refer to Figure 3 .

[0028] The second cutting protection layer 300 has the functions of protecting the surface of the metal substrate wafer 100 and absorbing cutting debris and slag, and has good thermal conductivity. In addition, since the second cutting protection layer 300 is formed by a water-soluble cutting protection liquid, it can be cleaned by washing with water, and the absorbed cutting debris and slag can be removed at the same time.

[0029] Specifically, before spin coating the water-soluble cutting protection liquid, a white film is first pasted on the front side of the metal substrate wafer 100. On the one hand, the white film can protect the chip structure on the front side of the metal substrate wafer 100, and on the other hand, the white film can be used as a support during cutting.

[0030] In some specific embodiments, the water-soluble cutting protection liquid comprises 20-50 parts of water-soluble resin, 5-15 parts of azeotropic solvent, 5-20 parts of polyol, 0.1-2 parts of water-soluble ultraviolet absorber, 0.05-0.1 parts of water-soluble antioxidant, 0.1-2 parts of pH adjuster, 0.05-0.1 parts of anticorrosive agent and 30-60 parts of deionized water. The water-soluble cutting protection liquid has good film-forming property, high thermal stability and good thermal conductivity after film formation, and good resolubility of the film, and is easily washed away by water.

[0031] Specifically, the water-soluble resin serves as a film-forming agent, which may be polyvinyl alcohol or polyethylene glycol; the azeotropic solvent is used to lower the boiling point of the mixture, which is beneficial for the water-soluble cutting protection liquid to quickly dry and form a film, and may be ethanol or isopropanol; the polyol serves as a humectant, which may be glycerol or propylene glycol; the water-soluble ultraviolet absorber is used for anti-aging, which may be benzotriazole compounds; the water-soluble antioxidant is used for anti-oxidation, which may be sodium vitamin C or sulfite; the pH adjuster is used to adjust the pH, which may be citric acid or triethanolamine; the corrosion inhibitor is used to prevent corrosion, which may be benzotriazole or molybdate; and the deionized water serves as the main solvent.

[0032] Preferably, the ingredients of the water-soluble cutting protection liquid include 35 parts of polyvinyl alcohol, 10 parts of ethanol, 10 parts of glycerol, 1 part of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 0.08 parts of sodium vitamin C, 1 part of citric acid, 0.07 parts of benzotriazole and 45 parts of deionized water, which balances film-forming properties and volatility and has good stability.

[0033] In some specific embodiments, the thickness of the second cutting protection layer 300 is in the range of 5000 to 10000 nm. The appropriate thickness is conducive to enabling the second cutting protection layer 300 to fully play the role of protecting the surface of the metal substrate wafer 100, absorbing cutting debris and slag, and conducting heat; moreover, the appropriate thickness is conducive to controlling costs.

[0034] Optionally, the thickness of the second cutting protection layer 300 may be 5000 nm, 6000 nm, 7000 nm, 8000 nm, 9000 nm or 10000 nm.

[0035] S3, using a first laser beam to cut and form a first groove on the second cutting protection layer, wherein the first groove extends from a surface of the second cutting protection layer to a surface of the metal substrate wafer; Figure 4 A schematic structural diagram of the first groove in an embodiment of the present invention is shown.

[0036] The first groove 400 can play the role of a heat conduction groove, which can speed up the heat transfer speed when the subsequent second laser beam cuts the metal substrate wafer 100, and effectively reduce the range of the heat-affected zone.

[0037] In some specific embodiments, the power range of the first laser beam is 3 to 5 W, the frequency range of the first laser beam is 80 to 100 kHz, and the cutting speed range of the first laser beam is 200 to 300 mm / s, which can effectively cut the first cutting protection layer 200 and the second cutting protection layer 300 to form a first groove 400 of appropriate size.

[0038] Preferably, the power of the first laser beam is 4W, the frequency of the first laser beam is 90kHz, and the cutting speed of the first laser beam is 250mm / s. The cutting parameter settings are suitable for cutting the first cutting protection layer 200 and the second cutting protection layer 300, and the depth and slot width of the formed first groove 400 are just right.

[0039] In some specific embodiments, the thickness of the first cutting protection layer 200 is h 1 , the thickness of the second cutting protection layer 300 is h 2 , the depth of the first groove 400 is H 1 , the slot width of the first groove 400 is W 1 , then it satisfies: h 1 +h 2 ≤H 1 ≤1.1*(h 1 +h 2 )、10000nm≤W 1 ≤20000nm.

[0040] If H 1 Greater than 1.1*(h 1 +h 2 ), it means that too much metal substrate wafer 100 is intruded during the process of cutting and forming the first groove 400, which is equivalent to cutting the metal substrate wafer 100 without cooling the first groove 400, which is easy to generate heat accumulation during the process of cutting and forming the first groove 400, which is not conducive to reducing the range of the heat affected zone, which is inconsistent with the purpose of using the first groove 400 as a heat conduction groove; if H 1 Less than (h 1 +h 2 ), the depth of the first groove 400 is insufficient, so that the heat conduction effect of the first cutting protection layer 200 cannot be fully utilized when the second groove 500 is subsequently cut, which is not conducive to reducing the range of the heat affected zone. 1 Equal to (h 1 +h 2 ), which is conducive to giving full play to the heat conduction effect of the first groove 400.

[0041] If W 1 If W is greater than 20000 nm, the slot width of the first groove 400 is too large, and when the second groove 500 is subsequently cut to form the second groove 500, cutting debris and slag are easily accumulated in the groove, which is not conducive to the removal of the cutting debris and slag. 1If it is less than 10000nm, the slot width of the first groove 400 is too small, which is not conducive to the positioning of the subsequent cutting to form the second groove 500. Optionally, the slot width of the first groove 400 can be 10000nm, 12000nm, 14000nm, 16000nm, 18000nm or 20000nm.

[0042] S4, using a second laser beam to continue cutting along the position of the first groove to form a second groove, wherein the second groove extends from the surface of the metal substrate wafer to the inside of the metal substrate wafer; Figure 5 A schematic diagram of the structure of the second groove in an embodiment of the present invention is shown.

[0043] When cutting to form the second groove 500, due to the dual heat conduction effects of the first cutting protection layer 200 and the second cutting protection layer 300, the first groove 400 can exert a strong heat conduction effect, which can effectively accelerate the heat transfer speed when the second laser beam cuts the metal substrate wafer 100, thereby effectively reducing the scope of the heat affected zone; moreover, when cutting to form the second groove 500, the second cutting protection layer 300 can effectively absorb cutting debris and slag.

[0044] In some specific embodiments, the power range of the second laser beam is 8 to 10 W, the frequency range of the second laser beam is 120 to 150 kHz, and the cutting speed range of the second laser beam is 250 to 350 mm / s, which can effectively cut the metal substrate of the metal substrate wafer 100 to form a second groove 500 of a suitable size.

[0045] Preferably, the power of the second laser beam is 9W, the frequency of the second laser beam is 135kHz, and the cutting speed of the second laser beam is 300mm / s. The cutting parameter settings are suitable for cutting the metal substrate of the metal substrate wafer 100, and the depth and slot width of the formed second groove 500 are just right; moreover, it is beneficial to reduce the scope of the heat affected zone.

[0046] In some specific embodiments, the thickness of the metal substrate wafer 100 is h 3 , the depth of the second groove 500 is H 2 , the width of the second groove 500 is W 2 , then it satisfies: 0.5*h 3 ≤H 2 ≤0.8*h 3 , 0.8*W 1 ≤W 2 ≤1.2*W 1 .

[0047] If H 2 More than 0.8*h 3 , the depth of the second groove 500 is too large, which may easily cause heat accumulation, resulting in a larger range of the heat-affected zone, and may easily affect the front side of the metal substrate wafer 100; if H 2 Less than 0.5*h 3 , the depth of the second groove 500 is too small, which wastes the heat conduction function of the first groove 400 on the one hand, and affects the subsequent splitting effect of the metal substrate wafer 100 on the other hand. 2 Equal to 0.65*h 3 The heat affected zone is small and the subsequent splitting effect is good.

[0048] If W 2 Greater than 1.2*W 1 , the slot width of the second groove 500 is too large, which requires more beam energy, generates more heat, and generates more debris and slag, which easily leads to a larger range of the heat-affected zone; if W 2 Less than 0.8*W 1 , the slot width of the second groove 500 is too small, which is not conducive to the longitudinal extension of the second groove 500 and affects the cutting depth of the second groove 500. 2 Equal to 0.8*W 1 , which is beneficial to make the inner walls of the first groove 400 and the second groove 500 transition smoothly, thereby facilitating the discharge of cutting debris and slag, and facilitating full play of the heat conduction effect of the first groove 400.

[0049] S5. Clean and remove the second cutting protection layer, thereby completing the back side cutting of the metal substrate wafer.

[0050] When cleaning and removing the second cutting protection layer 300 , the cutting debris and slag adsorbed on the second cutting protection layer 300 will also be cleaned away, so that the edge of the groove is neat and free of debris and slag, thereby avoiding the burr problem of the core particle.

[0051] Specifically, the second cutting protection layer 300 can be completely removed by washing with deionized water; after washing, the metal substrate wafer 100 needs to be dried.

[0052] Figure 6 FIG. 1 shows a schematic structural diagram of the front side of a metal substrate wafer in an embodiment of the present invention. Figure 7A schematic diagram of the cross-sectional structure of a metal substrate wafer in an embodiment of the present invention is shown, wherein a plurality of chip units 110 are formed on the front side of the metal substrate wafer 100, and the plurality of chip units 110 are separated based on a cutting isolation wall 120, and there is a gap between the cutting isolation wall 120 and the chip units 110; the front side of the metal substrate wafer 100 also needs to be cut to form grooves, and the presence of the cutting isolation wall 120 can effectively protect the chip units 110, prevent debris and slag from adhering to the chip units 110 during cutting, and can effectively improve the reliability and yield rate of the core particles.

[0053] For details, please refer to Figure 4 and Figure 5 The first groove 400 and the second groove 500 both correspond to the position of the cutting isolation wall 120, and the notch width of the first groove 400 and the notch width of the second groove 500 are both smaller than the width of the cutting isolation wall 120, which facilitates the subsequent splitting of the metal substrate wafer 100 to obtain core particles with smooth edges.

[0054] Figure 8 A schematic diagram of the structure of the third groove in an embodiment of the present invention is shown, and a third laser beam is used to cut and form a third groove 600 on the front side of the metal substrate wafer 100 along the position of the cutting isolation wall 120. The third groove 600 extends from the surface of the cutting isolation wall 120 to the inside of the metal substrate wafer 100. The third groove 600 corresponds to the second groove 500, which is convenient for the subsequent splitting of the metal substrate wafer 100, is beneficial to improving the edge flatness of the core particle, and can reduce the alignment difficulty and failure risk during the core particle packaging; at the same time, the third groove 600 is cut along the position of the cutting isolation wall 120, which can effectively prevent the debris and slag during cutting from adhering to the chip unit 110, and can effectively improve the reliability and yield rate of the core particle.

[0055] Before cutting and forming the third groove 600 , the metal substrate wafer 100 needs to be turned over onto another white film so that the front side of the metal substrate wafer 100 faces upward.

[0056] In some specific embodiments, the power range of the third laser beam is 6 to 8 W, the frequency range of the third laser beam is 120 to 150 kHz, and the cutting speed range of the third laser beam is 300 to 350 mm / s, which can effectively cut the front side of the metal substrate wafer 100 to form a third groove 600 of appropriate size.

[0057] Preferably, the power of the third laser beam is 7W, the frequency of the third laser beam is 135kHz, and the cutting speed of the third laser beam is 325mm / s. The cutting parameter settings are suitable for cutting the front side of the metal substrate wafer 100, and the depth and slot width of the formed third groove 600 are just right.

[0058] In some specific embodiments, the thickness of the metal substrate wafer 100 is h 3 , the depth of the third groove 600 is H 3 The width of the third groove 600 is W 3 The width of the cutting isolation wall 120 is W 4 , then it satisfies: 0.2*h 3 ≤H 3 ≤0.5*h 3 , W 3 ≤W 4 .

[0059] The depth H of the third trench 600 is 3 The depth H of the second trench 500 is 2 Cooperating with each other, it is sufficient to separate the entire metal substrate wafer 100, which is convenient for the subsequent splitting of the metal substrate wafer 100; 3 ≤W 4 , preventing the third groove 600 from being too large, so that the cutting isolation wall 120 can effectively intercept debris and slag.

[0060] After the third groove 600 is completed, the metal substrate wafer 100 can be split by a splitter, firstly performing forward splitting along the third groove 600 and then performing back splitting along the first groove 400 and the second groove 500, so as to form a plurality of separate core particles after film expansion.

[0061] In the cutting method of the metal substrate wafer 100 of the present invention, a metal material is evaporated on the back side of the metal substrate wafer 100 to form a first cutting protection layer 200. The first cutting protection layer 200 made of metal material can not only absorb the beam energy of different powers and different cutting rates, but also effectively transfer the cutting heat to avoid excessive heat concentration, thereby effectively reducing the range of heat affected zone generation; then a water-soluble cutting protection liquid is spin-coated on the first cutting protection layer 200 to form a second cutting protection layer 300. The second cutting protection layer 300 has the functions of protecting the surface of the metal substrate wafer 100 and absorbing cutting debris and slag, and has good thermal conductivity; since the second cutting protection layer 300 is formed by a water-soluble cutting protection liquid, it can be cleaned by washing with water, and the adsorbed cutting debris and slag can be removed at the same time, thereby effectively preventing debris, slag, etc. from remaining on the edge of the core particle; the first cutting protection layer 200 and the second cutting protection layer 300 can form a dual thermal conductivity effect, further transfer the cutting heat, avoid excessive heat concentration, thereby effectively reducing the range of heat affected zone generation.

[0062] Moreover, the first cutting protection layer 200 and the second cutting protection layer 300 are firstly cut to form the first groove 400 by the first laser beam, and then the second groove 500 is cut along the position of the first groove 400 by the second laser beam. This can fully exert the functional role of the first cutting protection layer 200 and the second cutting protection layer 300: when cutting to form the second groove 500, due to the dual heat conduction effect of the first cutting protection layer 200 and the second cutting protection layer 300, the first groove 400 can exert a strong heat conduction effect, which can effectively speed up the heat transfer speed when the second laser beam cuts the metal substrate wafer 100, thereby effectively reducing the range of the heat affected zone; moreover, when cutting to form the second groove 500, the second cutting protection layer 300 can effectively absorb cutting debris and slag.

[0063] Therefore, through the mutual cooperation of the first cutting protection layer 200 and the second cutting protection layer 300, and performing laser cutting in steps, on the one hand, it can effectively prevent debris, slag, etc. from remaining on the edge of the core particle, avoid the problem of burrs on the core particle, thereby effectively improving the cutting yield of the metal substrate wafer 100; on the other hand, it can effectively reduce the scope of the heat-affected zone, avoid the expansion of the uneven area on the side surface of the core particle metal substrate, which is beneficial to reduce the risk of solid crystal voids when packaging the core particle, thereby effectively improving the packaging yield of the core particle.

[0064] In addition, the present invention sets a cutting isolation wall 120 on the front side of the metal substrate wafer 100, and cuts along the position of the cutting isolation wall 120 to form a third groove 600, which can effectively prevent debris and slag from adhering to the chip unit 110 during cutting, and can effectively improve the reliability and yield of the core particles; the first groove 400, the second groove 500 and the third groove 600 cooperate with each other to facilitate the splitting of the metal substrate wafer 100, which is beneficial to improving the edge flatness of the core particles, and can reduce the alignment difficulty and failure risk during core particle packaging.

[0065] Compared with the existing cutting method of the metal substrate wafer 100, the cutting method of the present invention obtains a core particle edge free of debris and slag, good edge flatness, no burrs, and an extremely small range of heat-affected zones, which makes the yield rate of the core particles high and is also beneficial to improving the subsequent packaging yield of the core particles.

[0066] Cutting effect detection Example 1 Providing a metal substrate wafer sample to be cut, the thickness of the metal substrate wafer sample itself is 160 μm; The thickness of the evaporated first cutting protection layer is 3500nm. The first cutting protection layer includes a bottom metal layer, a middle metal layer and a surface metal layer which are sequentially evaporated on the back of the metal substrate wafer. The bottom metal layer is made of Cr, the middle metal layer is a stacked structure of a Ti layer, a Ni layer, an Al layer and a Pt layer, and the surface metal layer is a stacked structure of an Au layer, a Sn layer and an AuSn layer. The thickness of the spin-coated second cutting protection layer is 6000 nm. The components of the water-soluble cutting protection liquid used include 35 parts of polyvinyl alcohol, 10 parts of ethanol, 10 parts of glycerol, 1 part of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 0.08 parts of sodium ascorbyl palmitate, 1 part of citric acid, 0.07 parts of benzotriazole and 45 parts of deionized water. The power of the first laser beam is 4W, the frequency is 90kHz, the cutting speed is 250mm / s, and the depth of the first groove is 9500nm; the power of the second laser beam is 9W, the frequency is 135kHz, the cutting speed is 300mm / s, and the depth of the second groove is 80μm.

[0067] Fig. 9 A schematic diagram of the cutting effect of Example 1 is shown; the range of the heat-affected zone of Example 1 is 10.2 to 11.8 μm.

[0068] Example 2 The difference from the first embodiment is that the depth of the second groove is 90 μm.

[0069] Fig.10A schematic diagram of the cutting effect of Example 2 is shown; the range of the heat-affected zone of Example 2 is 12.7 to 14.3 μm.

[0070] Example 3 The difference from the first embodiment is that the depth of the first groove is 10000 nm, and the depth of the second groove is 100 μm.

[0071] Fig.11 A schematic diagram of the cutting effect of Example 3 is shown; the range of the heat-affected zone of Example 3 is 14.1 to 15.9 μm.

[0072] Example 4 The difference from the first embodiment is that the depth of the first groove is 10000 nm, and the depth of the second groove is 110 μm.

[0073] Fig.12 A schematic diagram of the cutting effect of Example 4 is shown; the range of the heat-affected zone of Example 4 is 15.5 to 17.5 μm.

[0074] Example 5 The difference from the first embodiment is that the depth of the first groove is 10000 nm, and the depth of the second groove is 120 μm.

[0075] Fig.13 A schematic diagram of the cutting effect of Example 5 is shown; the range of the heat-affected zone of Example 5 is 17.2 to 19.6 μm.

[0076] Comparative Example 1 Providing a metal substrate wafer sample to be cut, the thickness of the metal substrate wafer sample itself is 160 μm; The first cutting protection layer is formed without evaporating a metal material, and a water-soluble cutting protection liquid is directly spin-coated and dried to form a protection layer with a thickness of 9500 nm. The components of the water-soluble cutting protection liquid used include 35 parts of polyvinyl alcohol, 10 parts of ethanol, 10 parts of glycerol, 1 part of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 0.08 parts of sodium ascorbyl palmitate, 1 part of citric acid, 0.07 parts of benzotriazole and 45 parts of deionized water. The cutting is not performed twice, but directly performed with a laser beam having a power of 9 W, a frequency of 135 kHz, and a cutting speed of 300 mm / s, and the depth of the groove is 89500 nm.

[0077] Fig.14 A schematic diagram of the cutting effect of comparative example 1 is shown; the range of the heat-affected zone of comparative example 1 is 60 to 80 μm.

[0078] in conclusion Compared with the existing cutting method of metal substrate wafers (see the cutting effect Figure 1), the cutting effects of Examples 1 to 5 are significantly better (see the cutting effects for details). Figures 9 to 13 ), the groove edge formed by cutting has less debris, less slag and good flatness.

[0079] Compared with the existing cutting method of metal substrate wafers (the range of the heat affected zone is 100-200μm), the range of the heat affected zone of Examples 1 to 5 is less than 20μm, which significantly reduces the range of the heat affected zone; moreover, compared with Comparative Example 1 (the range of the heat affected zone is 60-80μm), the range of the heat affected zone of Examples 1 to 5 is between 10 and 20μm, indicating that the first cutting protection layer and the second cutting protection layer combined can effectively reduce the range of the heat affected zone, with a significant effect.

[0080] The above is a detailed introduction to a metal substrate wafer cutting method provided by an embodiment of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for general technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for cutting a metal substrate wafer, characterized in that: The following steps are involved: S1, evaporating a metal material on the back side of the metal substrate wafer to form a first cutting protection layer; S2, spin coating a water-soluble cutting protection liquid on the first cutting protection layer, and forming a second cutting protection layer after drying; S3, using a first laser beam to cut and form a first groove on the second cutting protection layer, wherein the first groove extends from a surface of the second cutting protection layer to a surface of the metal substrate wafer; S4, using a second laser beam to continue cutting along the position of the first groove to form a second groove, wherein the second groove extends from the surface of the metal substrate wafer to the inside of the metal substrate wafer; S5. Clean and remove the second cutting protection layer, thereby completing the back side cutting of the metal substrate wafer.

2. The method for cutting a metal substrate wafer according to claim 1, wherein: The first cutting protection layer includes a bottom metal layer, a middle metal layer and a surface metal layer which are sequentially vapor-deposited on the back of the metal substrate wafer, the bottom metal layer is made of Cr or Ti, the middle metal layer is one or more of a Ti layer, a Ni layer, an Al layer, and a Pt layer, and the surface metal layer is one or more of an Au layer, a Sn layer, and an AuSn layer.

3. The method for cutting a metal substrate wafer according to claim 1 or 2, characterized in that: The thickness of the first cutting protection layer ranges from 2000 to 5000 nm.

4. The method for cutting a metal substrate wafer according to claim 1, wherein: In terms of weight, the components of the water-soluble cutting protection liquid include 20 to 50 parts of water-soluble resin, 5 to 15 parts of azeotropic solvent, 5 to 20 parts of polyol, 0.1 to 2 parts of water-soluble ultraviolet absorber, 0.05 to 0.1 parts of water-soluble antioxidant, 0.1 to 2 parts of pH adjuster, 0.05 to 0.1 parts of anti-corrosion agent and 30 to 60 parts of deionized water.

5. The method for cutting a metal substrate wafer according to claim 1, wherein: The thickness of the second cutting protection layer ranges from 5000 to 10000 nm.

6. The method for cutting a metal substrate wafer according to claim 1, wherein: The power range of the first laser beam is 3-5W, the frequency range of the first laser beam is 80-100kHz, and the cutting speed range of the first laser beam is 200-300mm / s.

7. The method for cutting a metal substrate wafer according to claim 1, wherein: The power range of the second laser beam is 8-10W, the frequency range of the second laser beam is 120-150kHz, and the cutting speed range of the second laser beam is 250-350mm / s.

8. The method for cutting a metal substrate wafer according to claim 1, wherein: The thickness of the first cutting protection layer is h1, the thickness of the second cutting protection layer is h2, the depth of the first groove is H1, and the width of the notch of the first groove is W1, then: h1+h2≤H1≤1.1*(h1+h2), 10000nm≤W1≤20000nm.

9. The method for cutting a metal substrate wafer according to claim 8, wherein: The thickness of the metal substrate wafer is h3, the depth of the second groove is H2, and the width of the second groove is W2, then: 0.5*h3≤H2≤0.8*h3, 0.8*W1≤W2≤1.2*W1.

10. The method for cutting a metal substrate wafer according to claim 1, wherein: A plurality of chip units are formed on the front side of the metal substrate wafer, and the plurality of chip units are separated based on a cutting isolation wall, and there is a gap between the cutting isolation wall and the chip units; The first groove and the second groove both correspond to the position of the cutting isolation wall, and the notch width of the first groove and the notch width of the second groove are both smaller than the width of the cutting isolation wall.

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