A photocatalytic and electrochemical assisted diamond cmp polishing device

Abstract

The application belongs to the technical field of semiconductor manufacturing, and particularly relates to a kind of diamond CMP The polishing device is characterized in that the negative electrode, the boron-doped diamond positive electrode and the polishing liquid form an electrolytic loop to realize high-efficiency electrochemical auxiliary polishing. The ultraviolet light source is designed in an immersion mode to directly irradiate the polishing liquid and the wafer, thereby significantly improving the effect of the ultraviolet light. The device has the advantages of high efficiency of hydroxyl radical generation, stable chemical reaction, strong controllability of the reaction and the like, and effectively solves the technical problems of low polishing efficiency and poor consistency of the diamond.

Description

Technical Field

[0001] This invention belongs to the technical field of semiconductor manufacturing, specifically relating to a photocatalytic and electrochemically assisted diamond... CMP Polishing device. Background Technology

[0002] Diamond possesses extremely high thermal conductivity, excellent dielectric breakdown strength, outstanding electron mobility, ultra-wide bandgap, and extremely low coefficient of thermal expansion, making it a promising material for semiconductor applications and an ideal material for manufacturing electronic and optical devices. Diamond wafer materials require extremely high surface integrity, including low surface roughness and freedom from surface or subsurface damage such as scratches, microcracks, dislocations, and residual stress, to ensure superior operational performance. However, the extremely high carbon-carbon bond energy between diamond atoms means it hardly reacts with any acids or bases at room temperature. Combined with its extremely high hardness, this makes surface treatment of diamond wafers quite challenging.

[0003] Chemical mechanical polishing (CMP) CMP This is currently a mature process for obtaining ultra-smooth, ultra-low-damage surfaces in semiconductor materials. It primarily utilizes the strong oxidizing effect of hydroxyl radicals. These radicals are typically generated through chemical reactions, such as the Fenton reaction, Fenton-like reactions, or ultraviolet photocatalysis, or directly through chemical reagents, such as hydrogen peroxide or oxidant decomposition. (See publication number...) CN113334242B A Chinese patent describes a method that uses hydrogen peroxide decomposition to generate hydroxyl radicals and then uses ultraviolet light irradiation to promote the oxidation of diamond wafer surfaces. However, this method suffers from problems such as low generation efficiency, poor reaction persistence, and difficulty in controlling the rate of hydroxyl radical generation, leading to instability in the chemical reaction. In addition, the ultraviolet light source of this device is located outside the polishing disc. The ultraviolet light needs to pass through the rotating quartz glass polishing disc, then through the polishing liquid, before it can act on the diamond surface. The ultraviolet light has a long propagation path and passes through many media, which weakens the effect. For diamond wafers, which have high hardness, brittleness, strong chemical inertness, and are difficult to oxidize, the existing polishing process has a technical bottleneck of low efficiency. Summary of the Invention

[0004] This invention provides a photocatalytic and electrochemically assisted diamond CMPThe polishing device sets a step groove on the top of the polishing table, sets the negative electrode and the polishing pad on the upper step surface of the step groove, uses boron-doped diamond material to make the positive electrode, connects with the external power supply to form an electrolysis loop, electrolyzes the polishing liquid, and benefits from the unique sp3 hybrid structure of the boron-doped diamond electrode and the hole conduction characteristics introduced by boron doping, so that it can still maintain stable electrochemical activity in a strong oxidative environment, and it can realize efficient and stable generation of hydroxyl radicals in the electrocatalytic process without relying on other chemical additives. In addition, by adjusting the applied potential and current density, the generation rate of hydroxyl radicals can be accurately controlled. In addition, by setting the ultraviolet light source on the lower step surface of the step groove, the ultraviolet light source is immersed in the polishing liquid, and the polishing liquid and the diamond wafer are directly irradiated, which greatly reduces the loss of ultraviolet light and improves the effect of ultraviolet light. Moreover, the device realizes precise control of process parameters through optimized design, ensures that each diamond wafer obtains equal process conditions in the processing process, and through the control of the rotation speed and pressure of the polishing head, the ultraviolet light irradiation time of all wafers can be strictly consistent. Based on the design of the electrolysis loop, the uniformity of the electrochemical reaction time of each wafer is realized. This multi-parameter cooperative control mechanism significantly improves the quality consistency of the diamond wafer surface treatment, effectively solving the processing consistency problem existing in the traditional polishing process.

[0005] The device comprises a polishing table and a polishing head, the polishing head is rotatably arranged above the polishing table; the top of the polishing table is provided with a step groove, the step groove contains polishing liquid, the upper step surface of the step groove is sequentially provided with a negative electrode and a polishing pad from bottom to top, and an ultraviolet light source is arranged on the lower step surface of the step groove; the bottom of the polishing head is provided with a boron-doped diamond positive electrode and a plurality of diamond wafers to be polished, the plurality of diamond wafers to be polished are distributed on a circular track and can be in frictional contact with the polishing pad, the circular track, the boron-doped diamond positive electrode and the polishing head are coaxially arranged, and part of the circular track is located directly above the ultraviolet light source; the negative electrode and the boron-doped diamond positive electrode are connected with the external power supply through the conductive slip ring, and form an electrolysis loop with the polishing liquid; the ultraviolet light source is also connected with the external power supply through the conductive slip ring to form a power supply circuit.

[0006] In a specific embodiment, the polishing table is a cylinder, the step groove is a ring-shaped step groove with a low center and a high periphery, the negative electrode is a ring-shaped negative electrode matched with the upper step surface of the ring-shaped step groove, the polishing pad is a ring-shaped polishing pad matched with the upper step surface of the ring-shaped step groove, and the polishing table is rotatable.

[0007] In a specific embodiment, a bottom plate and a support column are further included, the bottom plate is provided with a first motor, the first motor is in transmission connection with the polishing table, the support column is provided with a second motor, the second motor is in transmission connection with the polishing head, and the support column is arranged on the bottom plate.

[0008] In a specific embodiment, the polishing liquid contains an electrically conductive medium and a composite photocatalyst, the electrically conductive medium is hydrochloric acid or sodium hydroxide, and the composite photocatalyst is PS / CeO 2 -TiO 2 、 ZIF-8 、 CNTs-TiO 2 、 PMMA / SiO 2 - B 、 PS / CeO 2 a combination of one or more of the materials.

[0009] In a specific embodiment, the negative electrode is fixed on the upper step surface of the step groove through a screw, and the negative electrode is a platinum electrode.

[0010] In a specific embodiment, the polishing pad is bonded to the negative electrode, and the polishing pad is provided with a plurality of through holes.

[0011] In a specific embodiment, the plurality of through holes are arranged in a honeycomb array.

[0012] In a specific embodiment, a transparent lampshade is further arranged on the lower step surface of the step groove, and the ultraviolet light source is arranged in the transparent lampshade.

[0013] In a specific embodiment, the boron-doped diamond positive electrode is bonded to the bottom of the polishing head through conductive glue.

[0014] In a specific embodiment, the diamond wafer to be polished is bonded to the bottom of the polishing head through paraffin wax.

[0015] The present application has at least the following beneficial effects:

[0016] 1. The boron-doped diamond is used as an anode material to electrolyze the polishing liquid, compared with other ordinary positive electrodes, the use of the boron-doped diamond positive electrode can continuously and stably generate a large amount of hydroxyl radicals, so that the hydroxyl radical generation efficiency is high, the reaction sustainability is good, and the reaction rate is easy to control.

[0017] 2. By setting a stepped groove on the top of the polishing table, the ultraviolet light source can be integrated into the polishing table and immersed in the polishing slurry to directly irradiate the polishing slurry and diamond wafers, which greatly reduces the loss of ultraviolet light and improves the effect of ultraviolet light.

[0018] 3. By distributing several diamond wafers to be polished along a circular path coaxial with the polishing head, with a portion of the circular path directly above the ultraviolet light source, the diamond wafers undergo alternating mechanical polishing and ultraviolet photocatalysis as the polishing head rotates. This ensures that each diamond wafer receives consistent ultraviolet light irradiation time, mechanical polishing time, and electrolytic reaction time, significantly improving the consistency of the diamond wafer surface treatment effect. Furthermore, the ultraviolet light can irradiate the entire diamond wafer, enhancing the effectiveness of the ultraviolet light.

[0019] 4. By combining electric field, light field and chemical mechanical polishing, and working synergistically, the efficient, stable and controllable generation of hydroxyl radicals is achieved, which improves the surface treatment efficiency and quality of diamond wafers. Attached Figure Description

[0020] Figure 1 This is a partial cross-sectional schematic diagram of an embodiment of the present invention.

[0021] Figure 2 This is an overall structural diagram of an embodiment of the present invention.

[0022] Figure 3 This is a partial structural diagram of an embodiment of the present invention.

[0023] Figure 4 This is a structural diagram of the annular polishing pad in an embodiment of the present invention.

[0024] Figure 5 This is an electron microscope image of the diamond wafer surface before processing in an embodiment of the present invention.

[0025] Figure 6 This is an electron microscope image of the processed diamond wafer surface in an embodiment of the present invention.

[0026] Attached diagram labels: Base plate 1, Support column 2. L 3. Shaped support plate, 4. First motor, 5. Polishing table, 6. Right-angle support plate, 7. Second motor, 8. Polishing head, 9. Annular negative electrode, 10. Annular polishing pad, 11. Through hole, 13. Ultraviolet light source, 14. Boron-doped diamond positive electrode, 15. Diamond wafer, 16. Conductive slip ring, 18. Polishing fluid, 19. Power supply. Detailed Implementation

[0027] Please see Figures 1-4 This invention provides a photocatalytic and electrochemically assisted diamond... CMPThe polishing device comprises a base plate 1 and a supporting column 2, an L-shaped supporting plate 3 is arranged on the base plate 1, L A first motor 4 is arranged on the L-shaped supporting plate 3, the output shaft of the first motor 4 is connected with a stepped shaft through an elastic coupling, the stepped shaft is connected with a conical roller bearing through a bearing bush, LThe first motor 4 is connected with the support plate 3 through a rotating connection, and a polishing table 5 is installed on the step shaft, so that the polishing table 5 can be driven to rotate by the first motor 4. The support column 2 is arranged on the bottom plate 1, and a right-angle support plate 6 is detachably connected to the support column 2 through bolts. A second motor 7 is arranged on the right-angle support plate 6, and the output shaft of the second motor 7 is rotatably connected with the right-angle support plate 6 through a tapered roller bearing and is connected with a polishing head 8 through an elastic coupling. The polishing head 8 is arranged above the polishing table 5, so that the polishing head 8 can be driven to rotate by the second motor 7, thereby realizing the rotation of the polishing head 8 relative to the polishing table 5. The polishing table 5 is in the shape of a cylinder, and the top of the polishing table 5 is provided with an annular stepped groove with a low center and a high periphery. An external polishing liquid nozzle sprays polishing liquid 18 into the annular stepped groove. An annular negative electrode 9 and an annular polishing pad 10 are sequentially arranged on the upper step surface of the annular stepped groove from bottom to top. The annular negative electrode 9 is fixed on the upper step surface of the annular stepped groove through screws to ensure its stability, and the annular negative electrode 9 is made of platinum. The annular polishing pad 10 is bonded to the annular negative electrode 9 for convenient disassembly, and the annular polishing pad 10 is provided with a plurality of through holes 11 arranged in a honeycomb array. A transparent lampshade (not shown in the figure) is arranged on the lower step surface of the annular stepped groove, and a ultraviolet light source 13 is arranged in the transparent lampshade. The transparent lampshade is made of quartz glass. A boron-doped diamond positive electrode 14 and a plurality of diamond wafers 15 to be polished are arranged at the bottom of the polishing head 8. The boron-doped diamond positive electrode 14 is bonded to the center of the bottom of the polishing head 8 through conductive glue. The plurality of diamond wafers 15 to be polished are arranged on a circular track, are bonded to the bottom of the polishing head 8 through paraffin wax, and can be in frictional contact with the annular polishing pad 10 to realize multi-station simultaneous processing. The right-angle support plate 6 on the support column 2 is detachably connected through bolts, so that the right-angle support plate 6, the second motor 7 and the polishing head 8 can be integrally disassembled, thereby realizing the disassembly of the diamond wafers 15 to be polished. The circular track, the boron-doped diamond positive electrode 14 and the polishing head 8 are coaxially arranged, and part of the circular track is located directly above the ultraviolet light source 13. The polishing liquid 18 completely immerses the annular negative electrode 9, the annular polishing pad 10, the transparent lampshade, the ultraviolet light source 13, the boron-doped diamond positive electrode 14 and the diamond wafers 15. The annular negative electrode 9 and the boron-doped diamond positive electrode 14 are connected with an external power supply 19 through a conductive slip ring 16 connected with a conductive wire and form an electrolytic loop with the polishing liquid 18. The ultraviolet light source 13 is also connected with the external power supply 19 through the conductive slip ring 16 connected with the conductive wire to form a power supply loop. The polishing liquid 18 contains a conductive medium and a composite photocatalyst. The conductive medium is hydrochloric acid, so that the annular negative electrode 9 and the boron-doped diamond positive electrode 14 can be conducted through the polishing liquid 18 to form an electrolytic loop. The composite photocatalyst is PS / CeO 2 -TiO 2The material can strengthen the ultraviolet light catalysis and produce hydroxyl radicals more efficiently by adding the composite photocatalyst with the high specific surface area porous material. The hydroxyl radicals generated by electrolysis can quickly reach and act on the surface of the diamond wafer by setting the annular polishing pad 10 to be perforated.

[0028] In operation, the power supply 19, the first motor 4, the second motor 7 and the ultraviolet light source 13 are started, the annular negative electrode 9 and the boron-doped diamond positive electrode 14 are conducted through the polishing liquid 18, the polishing liquid 18 is electrolyzed to generate a large amount of hydroxyl radicals, at the same time, the polishing head 8 and the polishing table 5 rotate in opposite directions, a plurality of diamond wafers 15 to be polished are driven by the second motor 7 to rub against the polishing pad for mechanical polishing, the diamond wafer 15 rotates to be directly above the ultraviolet light source 13 and is irradiated by the ultraviolet light to further promote the generation of hydroxyl radicals. By combining the electric field, the light field and the chemical mechanical polishing and synergistically acting, the efficient, stable and controllable generation of hydroxyl radicals is realized, and the surface treatment efficiency and quality of the diamond wafer 15 are improved. Compared with other ordinary positive electrodes, the use of the boron-doped diamond positive electrode 14 can realize the continuous and stable generation of a large amount of hydroxyl radicals, so that the generation efficiency of hydroxyl radicals is high, the reaction sustainability is good, the reaction rate is easy to control, and the boron-doped diamond material itself is basically not consumed. By setting the annular step groove on the top of the polishing table 5, the ultraviolet light source 13 can be integrated on the polishing table 5 and immersed in the polishing liquid 18 to directly irradiate the polishing liquid 18 and the diamond wafer 15, thereby greatly reducing the loss of ultraviolet light and improving the effect of ultraviolet light. By distributing a plurality of diamond wafers 15 to be polished on a circular track coaxial with the polishing head 8, and part of the circular track is directly above the ultraviolet light source 13, the plurality of diamond wafers 15 to be polished can alternately perform mechanical polishing and ultraviolet light catalysis when the polishing head 8 rotates, so that each diamond wafer 15 is irradiated by the ultraviolet light for the same time, mechanically polished for the same time, and electrolyzed for the same time, thereby greatly improving the consistency of the surface treatment effect of the diamond wafer 15. Moreover, the ultraviolet light can irradiate the whole diamond wafer 15, thereby improving the effect of the ultraviolet light.

[0029] Please refer to Figures 5-6 , Figure 5 The surface electron microscope image of the diamond wafer before processing in the embodiment of the present application is shown in FIG. 1. Figure 6 The surface electron microscope image of the diamond wafer after processing in the embodiment of the present application is shown in FIG. 2. From the comparison of the two images, the surface treatment quality of the diamond wafer processed by the device is higher and the treatment effect is better.

[0030] Of course, in other embodiments, the polishing table 5 can also be set to be fixed, i.e. the first motor 4 is not started, or the first motor 4 is directly omitted. The polishing head 8 can be provided in plurality, and the plurality of polishing heads 8 are uniformly arranged along the circumferential direction of the polishing table 5, so as to realize one-time processing of more diamond wafers 15, greatly improve the processing efficiency, and ensure that the polishing table 5 is uniformly stressed without deviation. The conductive medium in the polishing liquid 18 can be sodium hydroxide, and the composite photocatalyst in the polishing liquid 18 can be ZIF- 8 、 CNTs-TiO 2 、 PMMA / SiO 2 -B 、 PS / CeO 2 A combination of one or more of the materials can also achieve the purpose of the present application.

[0031] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple deductions and substitutions can be made without departing from the concept of the present application, and all of them should be regarded as falling within the protection scope of the present application.

Claims

1. A photocatalytic and electrochemically assisted diamond CMP A polishing apparatus characterized by, CMP 2. The photocatalytic and electrochemical assisted diamond according to claim 1. CMP A polishing apparatus characterized by comprising: CMP 3. The photocatalytic and electrochemical assisted diamond of claim 2. PS / CeO A polishing apparatus characterized by comprising: -TiO 4. The photocatalytic and electrochemical assisted diamond according to claim 1 or 3 ZIF-8 A polishing apparatus characterized by comprising: The conductive medium is hydrochloric acid or sodium hydroxide, and the composite photocatalyst is CNTs-TiO 2 PMMA / SiO 2 、 PS / CeO 、 CMP 2 、 CMP 2 -B 、 CMP 2 a combination of one or more of the materials.

5. The photocatalytic and electrochemical assisted diamond of claim 3. CMP A polishing apparatus characterized by comprising: CMP 6. The photocatalytic and electrochemical assisted diamond of claim 3. CMP A polishing apparatus characterized by comprising: CMP 7. The photocatalytic and electrochemical assisted diamond of claim 6. CMP A polishing apparatus characterized by comprising: CMP 8. The photocatalytic and electrochemical assisted diamond of claim 1 or 3 CMP A polishing apparatus characterized by comprising: CMP 9. The photocatalytic and electrochemical assisted diamond of claim 1 CMP A polishing apparatus characterized by comprising: ​ 10. The photocatalytic and electrochemical assisted diamond of claim 1. ​ A polishing apparatus characterized by comprising: ​

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