A method for grinding a relaxor ferroelectric single crystal wafer

Abstract

The application provides a grinding method of a relaxor ferroelectric single crystal ultrathin wafer, and belongs to the technical field of ultrathin wafer processing.The grinding method comprises the following steps: placing a relaxor ferroelectric single wafer to be ground and a supporting wafer in a working hole of a star wheel, and grinding to obtain a relaxor ferroelectric single crystal ultrathin wafer; and the supporting wafer has a Mohs hardness of 5-8.The relaxor ferroelectric single wafer to be ground and the supporting wafer with a larger hardness are ground together, so that the internal stress of the wafer can be effectively reduced, wafer cracking or breaking after grinding can be avoided, the grinding efficiency is improved, the processing cost is reduced, and the wafer grinding precision is improved.

Description

Technical Field

[0001] This invention belongs to the field of ultrathin wafer processing technology, specifically relating to a grinding method for relaxor ferroelectric single crystal ultrathin wafers. Background Technology

[0002] Relaxor ferroelectric single crystals are currently recognized internationally as the material system with the best piezoelectric properties and have been successfully commercialized in high-definition medical ultrasound. However, due to the relatively low strength and hardness of relaxor ferroelectric single crystals, their processing becomes more difficult. To meet the practical application requirements of medical ultrasound, it is necessary to develop a low-cost, high-efficiency, high-precision wafer grinding process to further thin the wafers.

[0003] Traditional grinding methods primarily involve placing the wafer to be ground directly onto a flexible planetary wheel for grinding. However, this often results in wafer cracking or breakage after grinding. Therefore, improving the grinding method to avoid wafer cracking or breakage after grinding has become a challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a grinding method for ultrathin relaxor ferroelectric single crystal wafers. The grinding method provided by this invention can obtain ultrathin wafers, and the wafers will not crack or break after grinding.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for grinding relaxor ferroelectric single-crystal ultrathin wafers, comprising: The relaxor ferroelectric single crystal wafer to be ground and the support wafer are placed in the working hole of the planetary wheel and ground to obtain a relaxor ferroelectric single crystal ultrathin wafer. The supporting wafer has a Mohs hardness of 5 to 8.

[0006] Preferably, the number of relaxor ferroelectric single crystal wafers to be ground is 4 to 7.

[0007] Preferably, the number of supporting wafers is 3 to 6.

[0008] Preferably, the thickness of the planetary wheel is 0.15~0.45mm.

[0009] Preferably, the planetary wheel is made of blued steel.

[0010] Preferably, the planetary wheel is circular in shape.

[0011] Preferably, the working hole in the planetary wheel is rectangular in shape.

[0012] Preferably, the number of working holes in the planetary gear is the same as the total number of the relaxor ferroelectric single crystal wafer to be ground and the support wafer.

[0013] Preferably, the grinding speed is 10~30 rpm, the pressure is 0.01~0.03 MPa, and the time is 10~30 min.

[0014] Preferably, the thickness of the relaxor ferroelectric single crystal ultrathin wafer is ≤0.2mm.

[0015] This invention provides a method for grinding a relaxor ferroelectric single-crystal ultrathin wafer, comprising: placing the relaxor ferroelectric single-crystal wafer to be ground and a support wafer in the working hole of a planetary gear, and grinding to obtain the relaxor ferroelectric single-crystal ultrathin wafer; the support wafer has a Mohs hardness of 5-8. This invention grinds the relaxor ferroelectric single-crystal wafer to be ground and the support wafer with higher hardness together, which can effectively reduce the internal stress of the wafer, thereby avoiding cracking or breakage after grinding, improving grinding efficiency, reducing processing costs, and improving wafer grinding accuracy. The results of the embodiments show that after grinding using the grinding method provided by this invention, the thickness of the relaxor ferroelectric single-crystal ultrathin wafer is ≤0.2mm, the parallelism reaches ±0.003mm, and the relaxor ferroelectric single-crystal ultrathin wafer does not crack or break. Attached Figure Description

[0016] Figure 1 A schematic diagram showing one placement position of the relaxor ferroelectric single crystal wafer to be ground and the support wafer in the working hole of the planetary gear in the grinding method provided by the present invention. Figure 2 This is a schematic diagram showing another placement position of the relaxor ferroelectric single crystal wafer to be ground and the support wafer in the working hole of the planetary gear in the grinding method provided by the present invention. Detailed Implementation

[0017] This invention provides a method for grinding relaxor ferroelectric single-crystal ultrathin wafers, comprising: The relaxor ferroelectric single crystal wafer to be ground and the support wafer are placed in the working hole of the planetary wheel and ground to obtain a relaxor ferroelectric single crystal ultrathin wafer.

[0018] In one embodiment, the material of the relaxor ferroelectric single crystal wafer to be ground can specifically be lead magnesium niobate-lead titanate (PMNT), with a chemical composition of (1-x)Pb(Mg) 1 / 3 Nb 2 / 3 )O3-xPbTiO3, where x is 0.2~0.45; it can also be specifically lead indium niobate-lead magnesium niobate-lead titanate (PIMNT), with the chemical composition x[Pb(In 1 / 2 Nb 1 / 2 )O3]-y[Pb(Mg 1 / 3 Nb 2 / 3 The ferroelectric single crystal wafer to be ground has a Mohs hardness of 3.5. The ferroelectric single crystal wafer is 0.2~0.4, y is 0.2~0.6, and x+y+z=1.

[0019] In this invention, the number of relaxor ferroelectric single-crystal wafers to be ground is preferably 4 to 7. As one embodiment, the number of relaxor ferroelectric single-crystal wafers to be ground can specifically be 4, 5, 6, or 7.

[0020] In this invention, the shape of the relaxor ferroelectric single crystal wafer to be ground is preferably rectangular; the length of the relaxor ferroelectric single crystal wafer to be ground is preferably 22.2~22.7mm; and the width of the relaxor ferroelectric single crystal wafer to be ground is preferably 15.3~15.8mm.

[0021] This invention does not impose any special requirements on the thickness of the relaxor ferroelectric single crystal wafer to be ground; it can be selected according to actual needs. As one embodiment, the thickness of the relaxor ferroelectric single crystal wafer to be ground can be 0.2~0.6mm, or specifically 0.5mm or 0.25mm.

[0022] In this invention, the supporting wafer has a Mohs hardness of 5-8. As one embodiment, the supporting wafer can be made of crystal. This invention uses a supporting wafer with higher hardness to be ground along with the relaxor ferroelectric single-crystal wafer for joint grinding, which effectively reduces internal stress in the wafer, prevents cracking or breakage after grinding, and improves the grinding accuracy of the wafer.

[0023] In this invention, the number of supporting wafers is preferably 3 to 6. As one embodiment, the number of supporting wafers may specifically be 3, 4, 5, or 6.

[0024] In this invention, the shape of the supporting wafer is preferably rectangular; the length of the supporting wafer is preferably 22.2~22.7mm; and the width of the supporting wafer is preferably 15.3~15.8mm.

[0025] In this invention, the thickness of the supporting wafer is preferably the same as the thickness of the relaxor ferroelectric single wafer to be ground.

[0026] In this invention, the planetary wheel is preferably made of blued steel. The use of a rigid planetary wheel in this invention further reduces the risk of the wafer deforming and cracking or breaking due to deformation of the planetary wheel during the grinding process.

[0027] In this invention, the thickness of the planetary wheel is preferably 0.15~0.45mm. This invention does not impose a specific limitation on the thickness of the planetary wheel; it can be selected according to actual needs. As one embodiment, the thickness of the planetary wheel can specifically be 0.45mm, 0.2mm, or 0.15mm.

[0028] In this invention, the planetary wheel is preferably circular in shape; a working hole is provided in the planetary wheel; the working hole is preferably rectangular in shape; and the radius of the planetary wheel is preferably 150 mm.

[0029] In this invention, the working hole forms a clearance fit with the relaxor ferroelectric single crystal wafer to be ground and the supporting wafer; the tolerance of the clearance fit is preferably 0.3~0.5mm. The clearance fit between the wafer and the working hole in this invention can avoid or reduce cracking or breakage caused by wafer movement during the grinding process.

[0030] In this invention, the number of working holes in the planetary gear is preferably the same as the total number of the relaxor ferroelectric single crystal wafer to be ground and the support wafer.

[0031] In this invention, the working holes in the planetary wheel are preferably symmetrically distributed along the axis of symmetry of the center of the planetary wheel.

[0032] As one implementation, when the number of working holes in the planetary wheel is 10, the distribution of the working holes in the planetary wheel is as follows: Figure 1 As shown, it includes 8 outer ring working holes and 2 inner ring working holes; the 8 outer ring working holes are evenly distributed along the circumference; the length direction of each outer ring working hole is perpendicular to the direction of the line connecting the center point of the outer ring working hole and the center point of the planetary wheel; the 2 inner ring working holes are located in the central area of ​​the planetary wheel and are evenly arranged along the same straight line with the two outer ring working holes located opposite each other in the outer ring working holes.

[0033] In this invention, the relaxor ferroelectric single crystal wafer to be ground and the support wafer are preferably arranged in a cross pattern in the planetary wheel, or the support wafer is located in the working hole of the outer ring of the planetary wheel.

[0034] In one implementation, when the number of relaxor ferroelectric single-crystal wafers to be ground is 4 and the number of support wafers is 6, the placement positions of the relaxor ferroelectric single-crystal wafers to be ground and the support wafers are as follows: Figure 1 As shown, the relaxor ferroelectric single crystal wafer to be ground is located in two inner working holes and two outer working holes arranged in the same straight line as the outer working holes.

[0035] In one implementation, when there are 5 relaxor ferroelectric single-crystal wafers to be ground and 5 support wafers, the placement positions of the relaxor ferroelectric single-crystal wafers to be ground and the support wafers are as follows: Figure 2 As shown, four support wafers are evenly placed in the outer working hole, and the remaining support wafer is placed in the inner working hole.

[0036] In this invention, the preferred grinding speed is 10-30 rpm; the preferred grinding pressure is 0.01-0.03 MPa; and the preferred grinding time is 10-30 min. As one embodiment, the grinding speed can specifically be 10 rpm, 12 rpm, 15 rpm, 18 rpm, 20 rpm, 22 rpm, 25 rpm, 28 rpm, or 30 rpm; the grinding pressure can specifically be 0.02 MPa; and the grinding time can specifically be 10 min, 15 min, 20 min, 25 min, or 30 min.

[0037] In this invention, the grinding is preferably double-sided grinding.

[0038] In this invention, when the thickness of the relaxor ferroelectric single crystal wafer to be ground is greater than 0.45 mm, it is preferable to first perform a first grinding with a planetary wheel of 0.35~0.45 mm thickness, and then perform a second grinding with a planetary wheel of the target grinding thickness. Using the above-described grinding method of this invention can further reduce or avoid wafer cracking or breakage, and further improve grinding accuracy.

[0039] In this invention, the thickness of the relaxor ferroelectric single crystal ultrathin wafer is preferably ≤0.2mm.

[0040] This invention employs a wafer-on-disk method, the core of which lies in combining the relaxor ferroelectric single wafer to be ground with other support wafers of higher hardness. This effectively reduces internal stress in the wafer, reduces or avoids wafer cracking or breakage after grinding, and improves the grinding precision of the wafer, meeting the requirements of wafer thickness ≤0.2mm and parallelism ±0.003mm after grinding. This provides high-quality wafers for subsequent coating processes. At the same time, it improves the grinding efficiency by 60% compared to traditional wafer grinding methods and significantly reduces processing costs.

[0041] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] Example 1 A grinding method for relaxor ferroelectric single-crystal ultrathin wafers, such as... Figure 1 As shown, four relaxor ferroelectric single-layer crystal wafers (PMNT, (1-x)Pb(Mg)) to be ground are used. 1 / 3 Nb 2 / 3The sample consists of O3-xPbTiO3 (where x is 0.3, length 22.2mm, width 15.3mm, thickness 0.5mm, polished surface 15.3*22.2mm crystal plane, hardness 3.5) and six support wafers (made of crystal, length 22.2mm, width 15.3mm, thickness 0.5mm, hardness 7). These wafers are first placed in the working hole of a 0.45mm thick planetary gear (made of blued steel, hardness 6.5). The working hole and the wafer form a clearance fit with a tolerance of 0.4mm. A domestically produced X61 microcontroller is used. The first grinding (leveling) is performed using a D6S-2 double-sided grinding machine at a pressure of 0.02 MPa, a speed of 30 rpm, and a grinding time of 20 minutes. Then, the wafer after the first grinding is placed in the working hole of a 0.15 mm thick planetary wheel (made of blued steel with a hardness of 6.5) in the same position, and a second grinding is performed at 0.01 MPa and 20 rpm for 15 minutes to obtain a relaxor ferroelectric single crystal ultrathin wafer with a thickness of 0.2 mm ± 0.003 mm.

[0043] Example 2 A grinding method for relaxor ferroelectric single-crystal ultrathin wafers, such as... Figure 2 As shown, five relaxor ferroelectric single-crystal wafers (PIMNT, x[Pb(In)) to be ground are used. 1 / 2 Nb 1 / 2 )O3]-y[Pb(Mg 1 / 3 Nb 2 / 3 A ferroelectric single-crystal ultrathin wafer (PbTiO3) with x = 0.3, y = 0.5, z = 0.2, length 22.2 mm, width 15.3 mm, thickness 0.25 mm, and a grinding surface of 15.3*22.2 mm crystal plane with a hardness of 3.5 and 5 support wafers (made of crystal, length 22.2 mm, width 15.3 mm, thickness 0.25 mm, hardness 7) and 5 support wafers (made of crystal, length 22.2 mm, width 15.3 mm, thickness 0.25 mm, hardness 7) were placed in the working hole of a 0.15 mm thick planetary wheel (made of blued steel with a hardness of 6.5). The working hole and the wafer formed a clearance fit with a clearance fit tolerance of 0.4 mm. The wafer was ground using a domestic X61 D6S-2 double-sided grinding machine with a grinding pressure of 0.01 MPa, a rotation speed of 20 rpm, and a grinding time of 15 min to obtain a relaxor ferroelectric single-crystal ultrathin wafer with a thickness of 0.2 mm ± 0.003 mm.

[0044] Comparative Example 1 The material of the planetary wheel in Example 1 was replaced with a tough material (epoxy resin + glass fiber, hardness 4), and everything else was the same as in Example 1.

[0045] In Comparative Example 1, after grinding, all four PMNT wafers were broken because the planetary wheel deformed and stuck to the upper grinding disc.

[0046] Comparative Example 2 A 0.15mm thick planetary wheel made of blue steel (the same material as in Example 1) was used to grind 10 PMNT wafers with a thickness of 0.3mm on both sides. No support wafers were added. All 10 working holes were filled with PMNT wafers. The grinding pressure was 0.01MPa, the rotation speed was 20rpm, and the grinding time was 20min.

[0047] The wafers were polished multiple times using the method of Comparative Example 2. After each polishing, 4 to 5 wafers cracked.

[0048] As can be seen from the comparison of the embodiments and comparative examples, the grinding method provided by the present invention can avoid the wafer from cracking or breaking after grinding.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for grinding a relaxor ferroelectric single-crystal ultrathin wafer, comprising: The relaxor ferroelectric single crystal wafer to be ground and the support wafer are placed in the working hole of the planetary wheel and ground to obtain a relaxor ferroelectric single crystal ultrathin wafer. The supporting wafer has a Mohs hardness of 5 to 8.

2. The grinding method according to claim 1, characterized in that, The number of relaxor ferroelectric single crystal wafers to be ground is 4 to 7.

3. The grinding method according to claim 1, characterized in that, The number of supporting wafers is 3 to 6.

4. The grinding method according to claim 1, characterized in that, The thickness of the planetary wheel is 0.15~0.45mm.

5. The grinding method according to claim 1, characterized in that, The planetary wheel is made of blued steel.

6. The grinding method according to claim 1, characterized in that, The planetary wheel is circular in shape.

7. The grinding method according to claim 1, characterized in that, The working hole in the planetary wheel is rectangular in shape.

8. The grinding method according to claim 1, characterized in that, The number of working holes in the planetary gear is the same as the total number of the relaxor ferroelectric single crystal wafer to be ground and the support wafer.

9. The grinding method according to claim 1, characterized in that, The grinding speed is 10~30 rpm, the pressure is 0.01~0.03 MPa, and the time is 10~30 min.

10. The grinding method according to claim 1, characterized in that, The thickness of the relaxor ferroelectric single crystal ultrathin wafer is ≤0.2mm.

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