A PCD micro drill bit for processing brittle-hard materials in the semiconductor industry and a manufacturing method thereof

Abstract

The application provides a PCD micro drill bit for processing of brittle and hard materials in the semiconductor industry, comprising a drill handle and a drill rod connected in sequence, a spiral angle and a drill tip are arranged on the drill rod, a variable pitch spiral groove is arranged on the drill rod, the spiral angle of the variable pitch spiral groove is smoothly transitioned along the axial direction, the corresponding spiral angle is smoothly transitioned, the core diameter of the drill rod continuously increases from the drill tip to the drill handle, a positive taper structure with a small front and a large back is formed, the core diameter increasing rate of the drill rod is dynamically coupled with the absolute value of the spiral angle change rate, the outer diameter of the drill rod gradually decreases from the drill tip to the drill handle to form an inverted taper structure, and the problems of difficult chip removal, easy breaking of the drill, edge collapse at the inlet, edge collapse at the outlet, poor hole wall quality and short service life in the prior art can be solved.

Description

Technical Field

[0001] This application relates to the field of micro-hole drilling technology, specifically to a PCD micro drill bit for processing brittle and hard materials in the semiconductor industry and its manufacturing method. Background Technology

[0002] Monocrystalline silicon is the core substrate material for chip manufacturing, accounting for the largest proportion of brittle and hard materials in the semiconductor industry. It is characterized by high hardness, high elastic modulus, extremely low fracture toughness, and high thermal conductivity, making it a typical hard, brittle, and difficult-to-process material. In the semiconductor device manufacturing process, a large number of micro-holes with a diameter of less than 1 mm need to be processed on monocrystalline silicon wafers with a thickness of 0.3 mm to 1.0 mm for key processes such as through-silicon via interconnects, MEMS device structures, and chip heat dissipation.

[0003] Currently, the main cutting tools used for machining micro-holes in monocrystalline silicon are carbide drills and PCD (Polycrystalline Diamond) drills. Carbide drills have low hardness and poor wear resistance, resulting in extremely rapid wear when machining monocrystalline silicon. Their service life is typically only a few hundred holes, and machining accuracy is difficult to guarantee. PCD drills, on the other hand, have extremely high hardness and wear resistance, making them ideal tools for machining monocrystalline silicon.

[0004] Most existing PCD micro drills adopt a single-lead spiral flute design. Large-lead spiral flutes have a short chip removal distance and smooth chip removal, but they will reduce the sharpness of the drill bit's peripheral cutting edge and decrease the rigidity of the core. This makes them prone to bending deformation and breakage during high-speed drilling. On the other hand, small-lead spiral flutes have high peripheral cutting edge sharpness and good rigidity, but the chip removal distance is long. The single-crystal silicon chips are powdery and are very easy to accumulate and clog in the spiral flutes, which will lead to drill bit breakage and severe scratches on the hole wall. There is a technical problem of chip removal and rigidity: "large lead inevitably leads to a decrease in rigidity, and small lead inevitably leads to difficulty in chip removal."

[0005] Furthermore, while small-apex drill tips offer strong centering capabilities, they also generate significant cutting forces. Under these forces, monocrystalline silicon materials are prone to brittle fracture, leading to edge chipping at the inlet and collapse at the outlet. Conversely, large-apex drill tips have lower cutting forces and stronger resistance to edge chipping, but poorer centering capabilities, easily resulting in borehole deviation and out-of-tolerance diameter. This presents a technical problem where a large apex inevitably leads to decreased centering accuracy in terms of both centering and edge chipping resistance.

[0006] Current PCD micro drills all employ a cylindrical cutting edge design, with the cutting edge making surface contact with the hole wall. This large contact area results in significant radial cutting forces during cutting. For monocrystalline silicon, which has extremely low fracture toughness, these large radial forces can cause material chipping at the entry point and material collapse at the exit point, while also increasing hole wall roughness and potentially generating microcracks. While reducing the cutting edge width can decrease radial forces, it leads to poorer drill guidance and reduced machining stability.

[0007] Therefore, there is an urgent need to develop a PCD micro drill bit for semiconductor single-crystal silicon processing and its manufacturing method to solve the above-mentioned technical problems.

[0008] It should be noted that the above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is prior art. Summary of the Invention

[0009] This application aims to solve the above-mentioned technical problems and provide a PCD micro drill bit for processing brittle and hard materials in the semiconductor industry and its manufacturing method, which solves the problems of difficult chip removal, easy tool breakage, entry edge chipping, exit edge collapse, poor hole wall quality and short life in the prior art.

[0010] In a first aspect, this application relates to a PCD micro drill bit for processing brittle and hard materials in the semiconductor industry, comprising a drill shank and a drill rod connected in sequence, wherein the drill rod is provided with a helix angle and a drill tip, and the drill rod is provided with a variable lead helical groove, the helix angle of which smoothly transitions along the axial direction. The formula for the helix angle is: (z)= +( )·exp ; in, (z) is the helix angle at the axial position z. The initial helix angle of the drill tip. The helix angle at the end of the drill shank is given, k is the single-crystal silicon chip speed matching coefficient, and m is the smooth transition index. Let z be the total length of the variable lead spiral groove, and z be the axial distance from the drill tip. The core diameter of the drill rod continuously increases from the drill tip towards the drill shank, forming a parabolic structure that is smaller at the front and larger at the back. The rate of increase in the core diameter of the drill rod is dynamically coupled with the absolute value of the rate of change of the helix angle. The formula is: (z)= + · ; in, (z) is the core diameter at the axial position z. The initial core diameter of the drill tip. q is the basic parabolic coefficient, and q is the helix angle rigidity compensation coefficient. This is the absolute value of the rate of change of the helix angle; The outer diameter of the drill rod gradually decreases from the drill tip towards the drill shank. The formula for the outer diameter of the drill pipe is: (z)=D· ; in, (z) is the outer diameter of the drill pipe at the axial position z, and D is the diameter of the drill bit.

[0011] In one specific implementation, the helix angle includes an initial helix angle on the drill rod near the drill tip, an end helix angle on the drill rod near the drill shank, and a first helix angle and a second helix angle disposed between the initial helix angle and the end helix angle, wherein the initial helix angle is 35° and the end helix angle is 15°.

[0012] In one specific feasible implementation, the initial core diameter of the drill tip The relationship with the drill bit diameter D is 0.30D≤ ≤0.35D, the core diameter at the end of the drill pipe The value of the drill bit diameter D is 0.40D≤ ≤0.45D.

[0013] In one specific implementation, the drill rod includes a PCD cutter head, which includes a first cutting edge, a thinning chisel edge, a second cutting edge connected to the first cutting edge, and a peripheral cutting edge. The first cutting edge forms a central apex angle with the drill tip, and the central apex angle is 150°. The thickness of the thinning chisel edge is 5%-8% of the drill diameter D, and the angle between the second cutting edges is 85°-90°.

[0014] In one specific implementation, the peripheral cutting edge includes a plurality of prismatic cutting strips, each of the prismatic cutting strips including at least one plane, the width of each plane being 2%-3% of the drill bit diameter D.

[0015] In one specific implementation, the drill pipe is provided with an axial inverted cone, the length of which is 2-3 times the diameter of the drill bit from the drill tip, and the inverted cone amount is 0.005-0.01mm / 10mm.

[0016] In one specific implementation scheme, the drill tip includes multiple cutting edge diameters, as shown in the formula: =D· ; in, Let D be the diameter of the nth cutting edge, and D be the drill bit diameter. This refers to the critical edge-breaking cutting force for monocrystalline silicon. This is the total axial cutting force; The axial length of each cutting edge satisfies: · ,in, =0.

[0017] In one specific implementation, the PCD cutter head includes three cutting edges: the first cutting edge has a diameter of 0.26 mm, the second cutting edge has a diameter of 0.36 mm, the peripheral cutting edge has a diameter of 0.45 mm, and an arc transition portion is provided between the second cutting edge and the peripheral cutting edge, the radius of the arc transition portion being 0.1 mm-0.2 mm.

[0018] In one specific implementation, the variable lead spiral groove includes a first set of spiral grooves near the drill tip and a second set of spiral grooves near the drill shank. The peripheral cutting edge includes a first set of cutting edge bands near the drill tip and a second set of cutting edge bands near the drill shank. The ratio of the width w1 of the first set of spiral grooves to the width h1 of the first set of cutting edge bands is w1:h1 = 1.2:1, and the ratio of the width w2 of the second set of spiral grooves to the width h2 of the second set of cutting edge bands is w2:h2 = 1:1. The ratio of the width w1 of the first set of spiral grooves to the width h1 of the first set of cutting edge bands gradually changes from 1.2:1 from the drill tip to the drill shank, to a ratio of 1:1 for the width w2 of the second set of spiral grooves to the width h2 of the second set of cutting edge bands.

[0019] Secondly, this application provides a method for manufacturing PCD micro drill bits for processing brittle and hard materials in the semiconductor industry, comprising the following steps: S1: Prepare WC-Co carbide drill rod substrate and PCD cylindrical cutter head by cutting and preparing the drill rod substrate in sequence, including rough grinding of the shank, end face grinding to fixed length, tail chamfering, fine grinding of the shank, end face flattening, and fine grinding of the welded step at the end of the cutter rod. S2: After cleaning and laser marking the drill pipe base, the PCD cylindrical cutter head is welded to the end of the drill pipe base at the welding step using a vacuum high-frequency welding process. S3: The outer diameter of the PCD cutter head and the working section of the drill rod is machined by laser turning, and then the outer diameter and transition cone are finely ground. S4: Use a five-axis CNC diamond tool grinder to process variable lead spiral grooves, spiral angle coupled parabolic core diameters, equal stiffness continuous variable diameter structures, three-stage stepped drill tips, multi-faceted cutting edges and segmented axial clearance inverted cones to the finished size; S5: The drill tip back angle and peripheral cutting edge are subjected to a composite precision treatment of copper wheel electrolytic cutting edge and ultrasonic polishing. After completion inspection, it is packaged and put into storage.

[0020] This application provides a PCD micro drill bit for processing brittle and hard materials in the semiconductor industry, which has at least the following beneficial effects: The helix angle of this application adopts an exponential function for smooth transition, which ensures both the sharpness of the large helix angle and the large chip space in the near-tip region, while avoiding chip jamming and stress concentration at the segmentation points. At the same time, the core diameter increase rate is dynamically coupled with the helix angle change rate. In areas with larger helix angles, i.e., areas with weaker rigidity, the core diameter increases faster, accurately compensating for the rigidity loss caused by large helix angles and solving the problem of chip removal and rigidity balance. In addition, the drill rod outer diameter gradually decreases as the helix angle decreases. Unlike the traditional stepped clearance design, the diameter change of this application is continuous and smooth, avoiding stress concentration at the steps. At the same time, the diameter change range is positively correlated with the helix angle. In areas with smaller helix angles, i.e., areas with higher rigidity, the drill rod outer diameter is smaller, and there is more clearance, further reducing the friction between the drill rod and the hole wall, and achieving a balance between rigidity and clearance. Attached Figure Description

[0021] Figure 1 This application provides a schematic diagram of the structure of a PCD micro drill bit for processing brittle and hard materials in the semiconductor industry. Figure 2 : A side view of a drill pipe according to an embodiment of this application; Figure 3 : A cross-sectional view of the drill pipe according to an embodiment of this application; Figure 4 Another cross-sectional view of the drill pipe according to an embodiment of this application; Figure 5 : A cross-sectional view of a PCD drill bit according to an embodiment of this application; Figure 6 : A three-dimensional structural diagram of the drill pipe according to an embodiment of this application; Figure 7 : A side view of the drill pipe in an embodiment of this application.

[0022] Reference numerals: 1. Drill shank; 2. Drill rod; 21. PCD cutter head; 210. Drill tip; 211. Chisel edge; 212. First cutting edge; 213. Second cutting edge; 214. Circumferential cutting edge; 215. Arc transition section; 22. Drill body; 221. First set of cutting edges; 222. Second set of cutting edges; 23. Spiral groove; 231. First set of spiral grooves; 232. Second set of spiral grooves; Initial helix angle; First helix angle; Second helix angle; End helix angle; Width of the first set of spiral grooves; The width of the second set of spiral grooves; The width of the first set of cutting edges; The second set of cutting edge width; D, drill bit diameter; D1, outer diameter at the middle position; D2, outer diameter at the end position; Initial core diameter of the drill tip; Core diameter at the end of the drill pipe; The angle between the second and third cutting edges; θ; the center apex angle. Detailed Implementation

[0023] Preferred embodiments of this application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0024] It should be noted that, in the description of this application, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and should not be construed as indicating or implying relative importance. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] The following is in conjunction with the appendix Figures 1-7 This application will be described in further detail.

[0027] This application provides a PCD (Polycrystalline Diamond) micro drill bit for processing brittle and hard materials in the semiconductor industry, comprising a drill shank 1 and a drill rod 2 connected in sequence. The drill rod 2 has a helix angle and a drill tip 210, and a variable lead helical groove 23. The helix angle of the variable lead helical groove 23 smoothly transitions along the axial direction. The corresponding formula for the helix angle is: (z)= +( )·exp ; in, (z) is the helix angle at the axial position z. The initial helix angle of the drill tip. The helix angle at the end of the drill shank is given by , k is the single-crystal silicon chip velocity matching coefficient, and m is the smooth transition index. Let z be the total length of the variable lead helical groove, and z be the axial distance from the drill tip at 210°. The lead of the variable lead helical groove is derived from the helix angle formula and satisfies... (z)=π· , (z) represents the lead of the helical groove at the axial position z. In this embodiment, z=0 at the drill tip. (0)≈2mm, z=7mm at the drill shank (7)≈4.1mm.

[0028] The core diameter of drill pipe 2 increases continuously from drill tip 210 towards drill shank 1, forming a parabolic structure that is smaller at the front and larger at the back. The rate of increase in core diameter of drill pipe 2 is dynamically coupled with the absolute value of the rate of change of helix angle. The formula is: (z)= + · ; in, (z) is the core diameter at the axial position z. The initial core diameter of the drill tip. q is the basic parabolic coefficient, and q is the helix angle rigidity compensation coefficient. This is the absolute value of the rate of change of the helix angle; The outer diameter of drill pipe 2 gradually decreases from drill tip 210 towards drill shank 1, adopting the principle of equal stiffness design, and the diameter is proportional to the fourth root of the helix angle. The formula for the outer diameter of drill pipe 2 is: (z)=D· ; in, (z) is the outer diameter of the drill pipe at the axial position z, and D is the diameter of the drill bit.

[0029] This application provides a method for manufacturing PCD micro drill bits for processing brittle and hard materials in the semiconductor industry, including the following steps: S1: Prepare WC-Co (tungsten carbide-cobalt) cemented carbide drill rod 2 base and PCD cylindrical cutter head by cutting and preparing the drill rod 2 base in sequence by rough grinding of the shank, end face grinding to fixed length, tail chamfering, fine grinding of the shank, end face flattening, and fine grinding of the welded step at the end of the cutter rod. S2: After cleaning and laser marking the drill pipe base, the PCD cylindrical cutter head is welded to the end of the drill pipe 2 base at the welding step using a vacuum high-frequency welding process. S3: The outer diameter of the working section of the PCD cutter head 21 and the drill rod 2 is machined by laser turning, and then the outer diameter and transition cone are finely ground. S4: Use a five-axis CNC diamond tool grinder to process variable lead spiral grooves, spiral angle coupled parabolic core diameters, equal stiffness continuous variable diameter structures, three-stage stepped drill tips, multi-faceted cutting edges and segmented axial clearance inverted cones to the finished size; S5: The drill tip 210 back angle and peripheral cutting edge 214 are subjected to a combination of copper wheel electrolytic cutting edge and ultrasonic polishing for precision treatment. After completion inspection, they are packaged and put into storage.

[0030] The helix angle in this application adopts an exponential function for smooth transition, ensuring maximum chip space in the near-tip 210 region with large helix angles while avoiding chip jamming and stress concentration at segmentation points. Simultaneously, the core diameter increase rate is dynamically coupled with the helix angle change rate; the larger the helix angle, the weaker the rigidity, and the faster the core diameter increases, precisely compensating for the rigidity loss caused by large helix angles and solving the problem of chip removal and rigidity balance. Furthermore, the outer diameter of drill rod 2 gradually decreases as the helix angle decreases. Unlike traditional stepped clearance designs, the diameter change in this application is continuous and smooth, avoiding stress concentration at steps. The diameter change amplitude is positively correlated with the helix angle; the region with a smaller helix angle has higher rigidity, resulting in a smaller outer diameter of drill rod 2 and more clearance, further reducing friction between drill rod 2 and the hole wall, achieving a balance between rigidity and clearance. At the same time, multi-stage progressive cutting is employed, with the cutting load released step by step, suppressing edge chipping. Combined with a 150° large apex angle, a thinned transverse cutting edge 211, and a multi-faceted cutting edge band, the problem of edge chipping in monocrystalline silicon is solved.

[0031] Reference Figure 1This application discloses a PCD micro drill bit for machining brittle and hard materials in the semiconductor industry. The drill rod 2 has a PCD cutting head 21 welded to its front end. The drill rod 2 is equipped with a variable lead helical groove 23, a parabolic core diameter (smaller at the front and larger at the rear), a helical angle-coupled continuous diameter structure, a three-stage stepped drill tip 210, a multi-faceted cutting edge, and a segmented axial clearance tapered section. During high-speed machining, the axial force on the cutting edge is decomposed along the x and y coordinate axes to obtain a smaller radial force, effectively controlling entry edge chipping and exit edge collapse. This ensures machining accuracy and surface quality while maintaining high-speed drilling, and improves tool life.

[0032] Reference Figure 2 In this application, the helix angle of the variable lead helical groove 23 smoothly transitions along the axial direction as an exponential function, and the lead continuously changes with the helix angle and outer diameter. Satisfy the following formula: (z)= +( )·exp ; in, The initial helix angle of the drill tip. The helix angle at the end of the drill shank is given by , k is the single-crystal silicon chip velocity matching coefficient, and m is the smooth transition index. The variable lead helical groove 23 represents the total length, and z is the axial distance from the drill tip 210, in mm. In the embodiments of this application, the initial helix angle of the drill tip is... =35°, helix angle at the end of the drill shank =15°, single crystal silicon chip cutting speed matching coefficient k=2.8, smooth transition index m=1.5, variable lead spiral groove 23 total length =7mm. It is determined by the total length of drill pipe 2 and the length of drill shank 1.

[0033] The single-crystal silicon chip speed matching coefficient k is the overall rate at which the helix angle decreases from the large angle at the drill tip to the small angle at the drill shank 1. It matches the axial discharge speed gradient of the single-crystal silicon chip in the helical groove 23, ensuring that after the chip is generated from the drill tip, its axial speed is consistent with the rate of change of the lead of the helical groove 23 as it moves along the helical groove 23 towards the drill shank 1, thus avoiding the chip being squeezed, accumulated, or blocked in the groove.

[0034] The formula for calculating k is: Where Δβ is the maximum allowable deviation of the helix angle, which is taken as 0.5°~1° in this application. =0.3 0.5 , is the cutting and removal speed of single-crystal silicon. =10m / min~50m / min, which is the cutting speed for single-crystal silicon micro-drilling. For semiconductor single-crystal silicon machining, k=2.0 3.5. Through orthogonal experimental optimization, using chip removal efficiency and drill bit life as indicators, multiple sets of experiments verified that the optimal value for k was 2.8. The principle for adjusting k is that when the drill bit diameter decreases or the depth-to-diameter ratio increases, the k value needs to be increased; when the drill bit is a high-purity single-crystal silicon or diamond-coated drill bit, the k value needs to be decreased. k=2.8 is the optimal value verified by cutting experiments and is suitable for drilling single-crystal silicon holes with diameters of 0.1~1mm and depth-to-diameter ratios of 3~10.

[0035] The smooth transition index *m* controls the curvature shape of the helix angle transition curve, determining the distribution of the helix angle change rate at different axial positions. This achieves a continuous and smooth transition of the helix angle from the drill tip 210 to the drill shank 1, avoiding chip jamming and stress concentration problems associated with segmented variable lead. *m*=1 represents a standard exponential decay curve with a uniformly decreasing rate of change. *m*>1 represents a convex curve transition, with a slow change near the drill tip 210 and a fast change near the drill shank 1. *m*<1 represents a concave curve transition, with a fast change near the drill tip 210 and a slow change near the drill shank 1. Through finite element simulation and experimental optimization, in the embodiments of this application, the optimal value is *m*=1.5, which forms a smooth distribution while ensuring the most uniform stress distribution and minimal stress concentration in the drill bit.

[0036] The helix angle includes the initial helix angle 210 on drill pipe 2 near the drill tip. The helix angle at the end of drill pipe 2 near drill shank 1 and set at the initial helix angle With end helix angle The first helix angle between Second helix angle Initial helix angle The first helix angle is 35°. The second helix angle is 27°. It is 19°, with a terminal helix angle of 19°. The helix angle is 15°. The single-crystal silicon chip velocity matching coefficient k=2.8 is specifically designed for the flow characteristics of single-crystal silicon powder chips, ensuring that the chips are discharged from the helical groove 23 at the fastest speed. The helix angle transitions smoothly along the axial direction in an exponential function, naturally transitioning to the first helix angle of 27° at an axial position z≈2.1mm, naturally transitioning to the second helix angle of 19° at z≈4.5mm, and finally reaching the final helix angle of 15° at the end of the drill shank. This smooth transition of the helix angle allows the flow velocity of the chips in the helical groove 23 to change continuously without jamming at the boundary. At the same time, the stress distribution of the drill bit is more uniform, avoiding fatigue fracture caused by stress concentration.

[0037] Reference Figure 3 and Figure 4To compensate for the rigidity loss caused by the large helix angle, this application designs a helix angle rigidity compensation type modified parabolic core diameter structure, in which the rate of increase of the core diameter of drill pipe 2 is dynamically coupled with the absolute value of the rate of change of the helix angle. The formula is: (z)= + · , (z) is the core diameter at the axial position z. The initial core diameter of the drill tip. q is the basic parabolic coefficient, and q is the helix angle rigidity compensation coefficient. The absolute value of the rate of change of the helix angle is used in the embodiments of this application, where the initial core diameter of the drill tip is... The relationship with the drill bit diameter D is 0.30D≤ ≤0.35D, core diameter at the end of the drill pipe The relationship with the drill bit diameter D is 0.40D≤ ≤0.45D. In this embodiment, a further optimization is that the drill bit diameter is 0.45mm, that is, the initial core diameter is 0.135mm ≤ ≤0.1575mm, core diameter at the drill pipe end is 0.18mm≤ ≤0.2025mm. Initial core diameter of the drill tip. =0.15mm, which is 33.3% of the drill bit diameter. The modified parabolic core diameter of this application achieves dynamic adjustment of the core diameter increase rate by introducing the absolute value of the helix angle change rate. In the front large helix angle region, the helix angle change rate is large, the core diameter increase rate is faster, and more chip space compensation is provided; in the rear small helix angle region, the helix angle change rate is small, the core diameter increase rate is slower, ensuring sufficient rigidity compensation. The parabolic distribution has more uniform rigidity and less stress concentration than the linear distribution.

[0038] Basic parabolic coefficients To ensure the basic rate of increase in the core diameter of drill pipe 2 along the axial direction without considering changes in the helix angle, and to maintain the basic increasing trend of rigidity of drill pipe 2 from drill tip 210 to drill shank 1, providing basic compensation for the rigidity loss caused by changes in the helix angle, the basic parabolic coefficient is derived using the theory of equal-strength beams. The drill bit can be considered as a cantilever beam fixed at one end, and the core diameter of the equal-strength beam follows a parabolic distribution, as shown in the formula: = In the embodiments of this application, the basic parabolic coefficient =0.0012 It is used for drill bits with a diameter of 0.45mm.

[0039] The helix angle rigidity compensation coefficient q is a coefficient that quantifies the influence of the helix angle change rate on the core diameter increase rate, realizing the dynamic coupling between the core diameter increase rate and the helix angle change rate. The faster the helix angle changes, i.e., the greater the rigidity loss, the faster the core diameter increases, thus accurately compensating for the rigidity loss caused by a large helix angle. The helix angle rigidity compensation coefficient q is calibrated through finite element simulation. Finite element models of drill bits with different helix angles (15°-35°) are established, the same load is applied, the bending deformation is calculated, and the relationship curve of the helix angle change rate, deformation, and core diameter compensation is obtained by fitting. In the embodiment of this application, the helix angle rigidity compensation coefficient q = 0.0008 mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·mm·m ... .

[0040] The absolute value of the rate of change of the helix angle The absolute value of the change in helix angle per unit axial length is obtained by differentiating the helix angle formula. Since the helix angle decreases along the axial direction, the rate of change is negative. Taking the absolute value ensures that the rate of increase in core diameter is always positive. The increase in core diameter is adjusted in real time to follow the change in helix angle, achieving precise compensation for large rigidity loss and rapid increase in core diameter.

[0041] Reference Figure 3 The drill pipe 2 of this application adopts a helical angle coupling type continuous variable diameter design and uses the equal stiffness design principle to keep the bending stiffness EI(z) of the drill pipe constant. For thin-walled circular pipes, since the change in core diameter is very small relative to the change in outer diameter, about 1 / 5 of the change in outer diameter, it can be approximately considered in engineering to be proportional to the fourth power of the outer diameter, with an error of less than 5%. This satisfies the following formula: (z)=D· Where the drill bit diameter D = 0.45 mm, and when the drill tip z = 0, =35°, (z) = 0.45 mm. When in the middle position, take z = 2.1 mm. (z) = 27°, (2.1)≈0.94D, that is, D1=0.43mm. When the end position is [missing information], take z=7mm. (z) = 15°, (7)≈0.78D, that is, D2=0.35mm.

[0042] That is, the larger the helix angle, the weaker the rigidity of the drill bit, requiring a larger outer diameter of the drill pipe 2 to ensure rigidity; the smaller the helix angle, the stronger the rigidity of the drill bit, allowing for a smaller outer diameter of the drill pipe 2 to increase clearance and reduce friction. Unlike traditional stepped diameter reduction, the continuous smooth diameter reduction of this application has no abrupt step points, eliminating stress concentration at the steps and achieving a balance between rigidity and chip space.

[0043] The PCD cutter head 21 of this application adopts a three-stage stepped structure with single-crystal silicon critical cutting force distribution, and the diameter of each cutting edge satisfies the following formula: =D· Among them, the critical edge-breaking cutting force of single-crystal silicon =0.35N, total axial cutting force =1.1N, substituting into the calculation, we can obtain: the diameter of the first-stage cutting edge 212 is ≈0.26mm; Second-stage cutting edge diameter 213 ≈0.36mm, which can be optimized to 0.4mm in this embodiment; the diameter of the third-stage cutting edge ≈0.44mm. In this embodiment, the third-stage cutting edge is the peripheral cutting edge 214, that is, the diameter of the peripheral cutting edge 214 is equal to the drill bit diameter D=0.45mm; the axial length of each cutting edge satisfies: · ,in, =0. The axial length of the first-stage cutting edge is approximately 0.04 mm, and the axial length of the second-stage cutting edge is approximately 0.015 mm.

[0044] Critical edge chipping cutting force of single crystal silicon To determine the minimum axial cutting force required to induce brittle fracture and chipping in monocrystalline silicon, experiments and force measurements were conducted. Micro-drilling experiments were performed on monocrystalline silicon specimens, gradually increasing the axial force until visible chipping (width > 0.01 mm) was observed at the hole entrance. The axial force at this point was recorded. This process was repeated multiple times, and the average value was taken. The minimum axial cutting force required for monocrystalline silicon (100 crystal orientation) was determined. Approximately 0.3N-0.4N, and 0.35N in the embodiments of this application, for monocrystalline silicon. Approximately 0.3N~0.4N. Total axial cutting force. The total axial force experienced by the drill bit during drilling of single-crystal silicon is the total cutting load of the drill bit under specific machining conditions. It forms the basis for cutting force distribution and is a measured value for a feed rate of 0.0008 mm / r and a rotational speed of 18000 r / min. Through finite element simulation and cutting experiments, a coefficient of 0.15 was obtained. When the coefficient is <0.15, the cutting edge is too short, resulting in stress concentration and easy edge chipping; when the coefficient is >0.15, the cutting edge is too long, leading to high cutting resistance.

[0045] Reference Figure 1 , Figures 4-7The drill rod 2 includes a PCD cutter head 21, which includes a first cutting edge 212, a thinning chisel edge 211, a second cutting edge 213 connected to the first cutting edge 212, and a peripheral cutting edge 214. The first cutting edge 212 and the drill tip 210 form a central apex angle θ, which is 150°. The thickness of the thinning chisel edge 211 is 5%-8% of the drill diameter D, that is, the thickness of the chisel edge 211 is 0.0225mm-0.036mm, preferably 0.03mm in this embodiment. The angle between the second cutting edges 213 is 85°-90°. In the embodiments of this application, the PCD cutter head 21 includes three cutting edges: the first cutting edge 212 has a diameter of 0.26 mm, the second cutting edge 213 has a diameter of 0.36 mm, and the peripheral cutting edge 214 has a diameter of 0.45 mm. An arc transition portion 215 is provided between the second cutting edge 213 and the peripheral cutting edge 214. The radius of the arc transition portion 215 is 0.1 mm to 0.2 mm, and is preferably 0.1 mm in this embodiment.

[0046] The total cutting force is evenly distributed across the three cutting edges, ensuring that the cutting force borne by each cutting edge does not exceed the critical chipping cutting force of 0.35N for monocrystalline silicon, thus avoiding brittle fracture of the monocrystalline silicon material. Combined with a large 150° center apex angle, the axial cutting force is reduced; the thinned chisel edge with a thickness of 0.03mm enhances centering capability; and the 0.1mm radius rounded transition avoids stress concentration. Furthermore, improved drill tip penetration solves the problems of chipping at the entrance and collapse at the exit. The drill tip 210 of this application achieves a good balance between centering accuracy, cutting force, and anti-chipping capability.

[0047] The peripheral cutting edge 214 includes multiple prismatic cutting edges, that is, multiple prismatic cutting edges are machined on the surface of the peripheral cutting edge 214. There is a groove between two prismatic cutting edges. Each prismatic cutting edge includes at least one plane. The width of each plane is 2%-3% of the drill diameter D. In the embodiments of this application, the peripheral cutting edge 214 adopts a 3-prismatic cutting edge design. The width of each plane is 2.2% of the drill diameter D, that is, 0.01mm. The contact area between the multi-prismatic cutting edge and the hole wall is reduced and the radial cutting force is reduced, thereby reducing the chipping at the inlet and the collapse at the outlet. Meanwhile, this application designs an axial clearance cone. The length range of the axial clearance cone is 2-3 times the drill bit diameter from the drill tip, and the clearance amount is 0.005-0.01mm / 10mm. At a distance of 2.5 times the drill tip diameter, that is, within a length range of 1.125mm, the clearance amount is 0.008mm / 10mm. After this length, a full clearance design is adopted, with a clearance amount of 0.025mm. This can reduce axial cutting force and friction, and also ensure the overall rigidity of the drill bit.

[0048] Reference Figure 2The variable lead spiral groove 23 includes a first set of spiral grooves 231 near the drill tip 210 and a second set of spiral grooves 232 near the drill shank 1. The drill body 22 includes a first set of cutting edges 221 near the drill tip 210 and a second set of cutting edges 222 near the drill shank 1. The ratio of the width w1 of the first set of spiral grooves to the width h1 of the first set of cutting edges is w1:h1 = 1.2:1, and the ratio of the width w2 of the second set of spiral grooves to the width h2 of the second set of cutting edges is w2:h2 = 1:1. The ratio of the width w1 of the first set of spiral grooves to the width h1 of the first set of cutting edges gradually changes from 1.2:1 from the drill tip to the drill shank, to a ratio of 1:1 for the width w2 of the second set of spiral grooves to the width h2 of the second set of cutting edges.

[0049] Increasing the width w1 of the first set of spiral grooves in the front section to 1.2 times the width h1 of the first set of cutting edge bands increases the chip space in the front section by more than 20% compared to the traditional proportional design. Newly generated powder chips can immediately enter the wide spiral grooves, preventing accumulation near the cutting edge. Combined with the high-speed chip removal effect of the 35° large spiral angle in the front section, the chip residence time in the groove is shortened by 30%, and the chip removal resistance is reduced by 18%, significantly reducing chip clogging during high-speed drilling. It also avoids chip compression and scraping between the cutting edge and the hole wall, reducing the hole wall roughness from the traditional Ra≤0.2μm to Ra≤0.12μm. Combined with the progressive cutting of a 150° large center apex angle and a three-stage stepped drill tip 210, the entry edge chipping is stably controlled within 0.01mm. Setting the width h2 of the second set of cutting edges in the rear section to be equal to the width w2 of the second set of cutting edges enhances the guiding support force, reduces the radial runout of the drill bit, and the uniform guiding contact prevents the drill bit from shaking during high-speed drilling and within the drill hole, reducing the radial force at the exit and lowering the exit burrs.

[0050] In the embodiments of this application, the drill bit is divided into two functional sections along the axial direction: a drill tip cutting area and a drill shank guiding area. Specifically, the first set of spiral grooves 231 and the first set of cutting edges 221 form the drill tip cutting area, and the second set of spiral grooves 232 and the second set of cutting edges 222 form the drill shank guiding area. This segmented design of the PCD micro-drill, combining the drill tip cutting area and the drill shank guiding area with the variable lead spiral grooves 23, maximizes chip removal efficiency through the wide grooves and large helix angle of the front section, while maximizing rigidity through the narrow grooves and small helix angle of the rear section. The segmented design, combined with the parabolic core diameter, maximizes the sharpness of the PCD micro-drill through the narrow cutting edges and small core diameter of the front section, while maximizing rigidity through the wide cutting edges and large core diameter of the rear section. Finally, the segmented design, combined with the continuously variable diameter drill pipe, achieves a balance between borehole support and rigidity through the wide cutting edges and small outer diameter of the rear section.

[0051] The PCD micro drill bit for processing brittle and hard materials in the semiconductor industry, as described in this embodiment, is manufactured using the following steps: Material preparation: WC-8%Co cemented carbide drill rod matrix is ​​prepared using tungsten carbide rod material, and PCD cylindrical cutter blank with an average particle size of 2μm and a cobalt content of 11% is prepared by high temperature and high pressure synthesis method.

[0052] Drill rod pretreatment: The shank is coarsely ground with a centerless grinder, the end face is ground to a fixed length, the tail is chamfered, the shank is finely ground with a centerless grinder, the end face is rotated to flatten the head, and the end of the drill rod is finely ground with NP5 and then welded to a step.

[0053] Laser marking and cleaning: Product markings are engraved on the drill rod shank using a fiber laser marking machine, and then cleaned with anhydrous ethanol.

[0054] Vacuum high-frequency welding: The PCD cylindrical cutter head is fitted with the welding step of drill rod 2 and welded in a vacuum high-frequency welding furnace at a temperature of 750-780℃ and a vacuum degree of ≤5×10⁻⁶. - The temperature is 3Pa, held for 10-15 seconds, and the solder is Ag-Cu-Ti. This application features an arc-shaped welding design, which increases the axial force load and facilitates mass production. Using vacuum high-frequency welding with specific parameters, the welding strength is increased by more than 50% compared to traditional planar welding. This solves the problems of tool tip detachment and breakage during high-speed drilling with small-diameter PCD drills, reducing the breakage rate in batch processing.

[0055] Laser turning of outer diameter: A picosecond laser processing system with a wavelength of 532nm, a power of 10-20W, and a scanning speed of 50-100mm / s is used to turn the outer diameter of the PCD cutter head 21 and the working section of the drill rod 2, producing a continuous variable diameter structure with an outer diameter tolerance of ±1.2μm.

[0056] Transition cone for grinding: The transition cone between the working section and the shank of the drill rod is ground using an NP5 CNC tool grinder, with a cone angle of 30°.

[0057] Finished product machining: Using a five-axis CNC diamond tool grinder, the variable lead spiral groove 23, the corrected parabolic core diameter, the three-stage stepped drill tip, the multi-faceted cutting edge, and the segmented axial clearance tapered section are machined sequentially to the finished dimensions. The composite machining performed on the five-axis CNC diamond tool grinder achieves a machining accuracy of ±1.5μm, ensuring that the drill bit's surface finish, edge roughness, and passivation value meet the drawing requirements.

[0058] Composite cutting edge treatment: First, the back angle of the drill tip 210 is treated with copper wheel electrolysis using a 12% sodium phosphate solution as the electrolyte, a current density of 4-6 A / dm², and a treatment time of 25-30 seconds. Then, the peripheral cutting edge 214 is ultrasonically polished using a diamond micro-powder suspension with a particle size of W0.25, a frequency of 30 kHz, a power of 80 W, and a polishing time of 5 minutes. This composite cutting edge treatment process of copper wheel electrolysis and ultrasonic polishing removes microscopic burrs from the cutting edge and reduces surface roughness, resulting in better sharpness and smoothness, reduced cutting force, and stable chipping at the entry point of single-crystal silicon machining within 0.01 mm.

[0059] The PCD micro drill manufactured using this method has a service life of over 8,000 holes when machining monocrystalline silicon, which is 3-4 times that of existing technology products. The hole diameter tolerance is ±0.005mm, the exit burr is <0.015mm, the drilling is stable, and no tool breakage has occurred.

[0060] Inspection and Packaging: Full inspection is carried out using a super depth-of-field microscope and a coordinate measuring machine. Qualified products are vacuum-packed and put into storage.

[0061] Comparison data of blade structure:

[0062] Three-generation product iteration comparison experiment: To further demonstrate the synergistic effect of the various technical features of this application, iterative testing was conducted on three generations of products, and the results are shown in the table below:

[0063] A two-stage stepped drill tip structure was adopted, but the cutting force borne by the second-stage cutting edge exceeded the critical edge chipping cutting force of monocrystalline silicon, with edge chipping at the entrance reaching more than 0.02mm. It was improved to a three-stage stepped structure, which evenly distributed the total cutting force to the three-stage cutting edges, and the cutting force of each stage was controlled below 0.35N, and the edge chipping at the entrance was successfully reduced to within 0.01mm.

[0064] The technical solutions of this application have been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A PCD micro drill bit for processing brittle and hard materials in the semiconductor industry, characterized in that, The system includes a drill shank and a drill rod connected in sequence. The drill rod has a helix angle and a drill tip. The drill rod also has a variable lead helical groove, the helix angle of which smoothly transitions axially. The formula for the helix angle is: (z)= +( )·exp ; in, (z) is the helix angle at the axial position z. The initial helix angle of the drill tip. The helix angle at the end of the drill shank is given, k is the single-crystal silicon chip speed matching coefficient, and m is the smooth transition index. Let z be the total length of the variable lead spiral groove, and z be the axial distance from the drill tip. The core diameter of the drill rod continuously increases from the drill tip towards the drill shank, forming a parabolic structure that is smaller at the front and larger at the back. The rate of increase in the core diameter of the drill rod is dynamically coupled with the absolute value of the rate of change of the helix angle. The formula is: (z)= + · ; in, (z) is the core diameter at the axial position z. The initial core diameter of the drill tip. q is the basic parabolic coefficient, and q is the helix angle rigidity compensation coefficient. This is the absolute value of the rate of change of the helix angle; The outer diameter of the drill rod gradually decreases from the drill tip towards the drill shank. The formula for the outer diameter of the drill pipe is: (z)=D· ; in, (z) is the outer diameter of the drill pipe at the axial position z, and D is the diameter of the drill bit.

2. The PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 1, characterized in that, The helix angle includes an initial helix angle near the drill tip, an end helix angle near the drill shank, and a first helix angle and a second helix angle located between the initial helix angle and the end helix angle. The initial helix angle is 35°, and the end helix angle is 15°.

3. The PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 1, characterized in that, The initial core diameter of the drill tip The relationship with the drill bit diameter D is 0.30D≤ ≤0.35D, the core diameter at the end of the drill pipe The value of the drill bit diameter D is 0.40D≤ ≤0.45D.

4. A PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 1, characterized in that, The drill rod includes a drill body and a PCD cutter head. The PCD cutter head includes a first cutting edge, a thinning chisel edge, a second cutting edge connected to the first cutting edge, and a peripheral edge. The first cutting edge forms a central apex angle with the drill tip, and the central apex angle is 150°. The thickness of the thinning chisel edge is 5%-8% of the drill diameter D. The angle between the second cutting edges is 85°-90°.

5. A PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 4, characterized in that, The peripheral cutting edge includes multiple prismatic cutting edges, each of which includes at least one plane, and the width of each plane is 2%-3% of the drill bit diameter D.

6. A PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 1, characterized in that, The drill pipe is provided with an axial inverted cone, the length of which is 2-3 times the diameter of the drill bit from the drill tip, and the inverted cone amount is 0.005-0.01mm / 10mm.

7. A PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 4, characterized in that, The PCD tool head includes multiple cutting edge diameters, as shown in the formula: =D· ; in, Let D be the diameter of the nth cutting edge, and D be the drill bit diameter. This refers to the critical edge chipping cutting force for single-crystal silicon materials. This is the total axial cutting force; The axial length of each cutting edge satisfies: · ,in, =0.

8. A PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 7, characterized in that, The PCD cutter head includes three cutting edges: the first cutting edge has a diameter of 0.26 mm, the second cutting edge has a diameter of 0.36 mm, and the peripheral cutting edge has a diameter of 0.45 mm. An arc transition portion with a radius of 0.1 mm to 0.2 mm is provided between the second cutting edge and the peripheral cutting edge.

9. A PCD micro drill bit for processing brittle and hard materials in the semiconductor industry according to claim 4, characterized in that, The variable lead spiral groove includes a first set of spiral grooves near the drill tip and a second set of spiral grooves near the drill shank. The drill body includes a first set of cutting edges near the drill tip and a second set of cutting edges near the drill shank. The ratio of the width w1 of the first set of spiral grooves to the width h1 of the first set of cutting edges is w1:h1 = 1.2:1, and the ratio of the width w2 of the second set of spiral grooves to the width h2 of the second set of cutting edges is w2:h2 = 1:

1. The ratio of the width w1 of the first set of spiral grooves to the width h1 of the first set of cutting edges gradually changes from 1.2:1 from the drill tip to the drill shank, and then to a ratio of 1:1 for the width w2 of the second set of spiral grooves to the width h2 of the second set of cutting edges.

10. A method for manufacturing a PCD micro drill bit for processing brittle and hard materials in the semiconductor industry, comprising manufacturing a PCD micro drill bit for processing brittle and hard materials in the semiconductor industry as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: Prepare WC-Co carbide drill rod substrate and PCD cylindrical cutter head by cutting and preparing the drill rod substrate in sequence, including rough grinding of the shank, end face grinding to fixed length, tail chamfering, fine grinding of the shank, end face flattening, and fine grinding of the welded step at the end of the cutter rod. S2: After cleaning and laser marking the drill pipe base, the PCD cylindrical cutter head is welded to the end welding step of the drill pipe base using a vacuum high-frequency welding process; S3: The outer diameter of the PCD cutter head and the working section of the drill rod is machined by laser turning, and then the outer diameter and transition cone are finely ground. S4: Use a five-axis CNC diamond tool grinder to process variable lead spiral grooves, spiral angle coupled parabolic core diameters, equal stiffness continuous variable diameter structures, three-stage stepped drill tips, multi-faceted cutting edges and segmented axial clearance inverted cones to the finished size; S5: The drill tip back angle and peripheral cutting edge are subjected to a composite precision treatment of copper wheel electrolytic cutting edge and ultrasonic polishing. After completion inspection, it is packaged and put into storage.

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