A high-precision chemical mechanical polishing apparatus for a compound semiconductor and a control method thereof

Abstract

This invention belongs to the technical field of high-precision parts processing equipment, specifically relating to a high-precision chemical mechanical polishing (CMP) device and its control method for compound semiconductors. The device includes a grinding and polishing machine, a workpiece carrier, and a vacuum pump. The workpiece carrier further includes a polishing head, a flexible membrane cavity disposed below the polishing head, and N independently partitioned pressure chambers. A nanoscale online monitoring system includes a fixed measurement unit, a rotating optical path unit, and an optical signal transmission unit. A closed-loop control system receives thickness data, calculates the removal rate deviation of the workpiece area corresponding to each pressure chamber, and dynamically adjusts the output pressure of each electro-proportional valve. An edge effect active compensation structure performs compensation actions through integrated microchannels based on edge pressure and thickness signals. This invention enables precise control of the grinding amount, achieves closed-loop control, and effectively solves problems such as uneven pressure distribution, edge effects, and thermal deformation coupling.

Description

Technical Field

[0001] This invention belongs to the technical field of high-precision parts processing equipment, specifically relating to a high-precision chemical mechanical polishing equipment for compound semiconductors and its control method. Background Technology

[0002] Precision grinding and polishing machines are specialized equipment for high-precision surface processing of parts. They can achieve surface smoothness and gloss at the nanometer to sub-nanometer level. The core principle is the synergistic effect of mechanical friction and chemical action. The electric motor drives the grinding disc (or polishing disc) to rotate at high speed. The abrasive particles (such as diamond, alumina, silicon dioxide, etc.) generate relative motion with the workpiece surface, achieving the removal of trace materials. The chemical components in the grinding fluid react with the workpiece surface, softening or oxidizing the surface material, making it easier to be removed by mechanical action.

[0003] Problems with existing technology:

[0004] Grinding amount is difficult to control precisely. Most existing precision grinding and polishing machines rely on manual adjustment or simple spring pressure, which has the defect of "blind adjustment" based solely on experience settings. At the same time, the lack of closed-loop feedback leads to poor sample thickness consistency and reduced yield, which is particularly evident in the poor uniformity of large-size wafers. Due to uneven pressure distribution on the wafer, edge pressure effect, and thermal deformation coupling, the thickness error of a 300mm wafer is >±1μm, indicating a serious lack of precision control capability. In addition, regarding the edge pressure effect, the retaining ring pressure causes the polishing fluid to stagnate and the pressure to concentrate at the edge. Traditional multi-zone pressure control technology is unable to dynamically correct the technical pain point of "fast at the edge and slow at the center". Summary of the Invention

[0005] The purpose of this invention is to provide a high-precision chemical mechanical polishing device and its control method for compound semiconductors, which can achieve precise control of grinding amount, realize closed-loop control, and effectively solve problems such as uneven pressure distribution, edge effect and thermal deformation coupling.

[0006] The specific technical solution adopted by this invention is as follows:

[0007] A high-precision chemical mechanical polishing device for compound semiconductors includes a grinding and polishing machine, a workpiece carrier, and a vacuum pump;

[0008] The workpiece carrier also includes a polishing head, a flexible membrane cavity disposed below the polishing head, and N independent pressure partition chambers formed by partitioning, wherein N≥4, the pressure partition chambers are distributed in a concentric ring shape, and each pressure partition chamber is connected to an electric proportional valve through an independent air pipe.

[0009] The nanoscale online monitoring system includes a fixed measurement unit, a rotating optical path unit, and an optical signal transmission unit. The optical paths of the fixed measurement unit and the rotating optical path unit pass through the flexible membrane cavity and point to the surface of the workpiece to be polished, enabling real-time acquisition of nanoscale thickness distribution data on the workpiece surface.

[0010] The closed-loop control system, electrically connected to the electro-proportional valve and the nanoscale online monitoring system, is configured to: receive nanoscale thickness distribution data, calculate the material removal rate deviation of the workpiece area corresponding to each pressure zone chamber, and dynamically adjust the output pressure of each electro-proportional valve according to the deviation to achieve real-time correction of the workpiece surface flatness.

[0011] The edge effect active compensation structure includes a rigid support ring, a flexible inner layer, and an integrated microchannel. Based on edge pressure and thickness signals, it performs air cushion depressurization / liquid flushing / morphological adaptive compensation actions through the integrated microchannel.

[0012] Furthermore, the workpiece carrier also includes a fixed carrier plate, with a fixed ring fixedly assembled at the bottom of the fixed carrier plate. The polishing head is lifted and assembled inside the fixed ring. The polishing head has an integrally formed inner compartment, and a pressure sensor for real-time monitoring of the pressure values ​​of the pressure zones in each flexible membrane cavity is installed inside the inner compartment.

[0013] Furthermore, the nanoscale online monitoring system adopts a split architecture, including:

[0014] The fixed measurement unit is installed on the non-rotating part of the top of the fixed carrier plate and includes a laser source, fiber optic coupler, photodetector and signal processing module;

[0015] A rotating optical path unit is integrated inside the polishing head and rotates synchronously with the polishing head. The rotating optical path unit contains N+ sets of independent optical measurement channels. The optical fiber, lens group and transparent window of each set of independent optical measurement channels are distributed in concentric circles along the radial direction of the polishing head. The lens group includes a collimating lens and a focusing lens. An optical fiber distribution disk is provided inside the polishing head and at the top of the circular axis. The optical fiber distribution disk is fixed to the tail end of the rotating optical fiber.

[0016] The optical signal transmission unit adopts a multi-channel optical fiber rotary connector. Its fixed end is connected to the optical fiber coupler through an optical fiber, and its rotating end is connected to the optical fiber distribution disk through a rotating optical fiber, so as to realize low-loss optical signal transmission in the rotating state.

[0017] Furthermore, the closed-loop control system includes:

[0018] The data acquisition unit acquires nanometer-scale thickness distribution data with a sampling period of 1-10ms;

[0019] The error calculation unit compares the real-time thickness distribution data with the target thickness distribution and calculates the thickness deviation of the corresponding area of ​​each pressure zone.

[0020] The pressure compensation calculation unit calculates the pressure adjustment amount for each zone based on the improved Preston equation;

[0021] The pressure output unit converts the calculated pressure adjustment amount into a control voltage signal for the electro-proportional valve.

[0022] Furthermore, the rigid support ring is fixedly connected to the outer edge of the polishing head via a flange, the flexible inner layer is nested inside the rigid support ring, the integrated microchannel is disposed inside the flexible inner layer, and the interior of the flexible inner layer is filled with a micro heater.

[0023] Furthermore, the integrated microchannel includes annular air channels, radial branch channels, and a micropore array, with the outlet of the micropore array pointing obliquely at an angle of 30°-45°.

[0024] Furthermore, the gap between the inner edge of the flexible inner layer and the edge of the wafer is 0.5-2 mm, and the concentricity is ≤20 μm;

[0025] The flexible inner layer is made of a porous shape memory polymer with a compression deformation of 0.1-0.3 mm, a resilience of ≥95%, and a phase transition temperature of 35-45℃.

[0026] The porosity of the flexible inner layer is 30-50%.

[0027] A control method for a high-precision chemical mechanical polishing (CMP) device for compound semiconductors, comprising the following specific steps:

[0028] S1: Set the target thickness distribution Polishing time T, polishing head rotation speed Grinding disc rotation speed Read the initial pressure setpoint of each pressure zone chamber. ;

[0029] S2: Activate the nanoscale online monitoring system, with a sampling cycle. Capture the reflected light intensity signal from the wafer surface and calculate the instantaneous absolute thickness value. By introducing temperature drift compensation and vibration filtering algorithms, spatially resolved real-time thickness distribution data is output. Combine thickness data with polishing head rotation angle Perform timestamp alignment to generate a thickness stream with angle labels;

[0030] S3: Calculate the average thickness deviation of the corresponding area for each pressure zone. ;

[0031] S4: Calculate the pressure adjustment amount for each zone based on the improved PID control algorithm. The Preston equation correction term is introduced to perform inverse dynamic scaling of the adjustment amount and output. ;

[0032] S5: Calculate the pressure adjustment amount The compressed air is converted into the control voltage of the electric proportional valve and transmitted to the corresponding pressure zone chamber through the multi-channel rotary joint. The air pressure is converted into contact stress acting on the back of the wafer.

[0033] S6: Calculate the flatness index of the current workpiece surface. ,like If the set threshold or polishing time reaches T, then polishing ends; otherwise, return to step S2 to continue the loop.

[0034] S7: Store the process parameters, thickness evolution data, and final results of this polishing process in the process database.

[0035] A computer-readable storage medium having a computer program stored thereon, the computer program implementing a control method when executed by a processor.

[0036] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements a control method when executing the program.

[0037] The technical effects achieved by this invention are as follows:

[0038] This invention integrates a "multi-zone pressure-controlled polishing head" with nanoscale online monitoring technology. When the nanoscale online monitoring system detects that the wafer edge removal rate is too fast, the system reduces the gas pressure of the corresponding pressure zone in real time to correct the edge effect and achieve closed-loop control. This monitoring system not only performs monitoring but also commands the "multi-zone pressure-controlled polishing head" to achieve millisecond-level response.

[0039] In addition, nanosensors are cleverly arranged inside the rotating multi-zone air chamber. This structure provides the conditions for nanoscale monitoring, solves the signal interference problem of sensor cables during rotation, and at the same time utilizes the fluid dynamics of polishing fluid to protect the sensors, solving the problems of spatial interference and signal crosstalk that would arise when the two coexist.

[0040] Unlike existing multi-zone pressure control technologies that rely on "offline monitoring" or "macroscopic monitoring," this method employs "nanoscale" and "in-situ real-time detection" techniques. Compared to "micrometer-scale" monitoring, "nanoscale" monitoring is more effective at detecting local micro-protrusions. Furthermore, this combination of techniques addresses the shortcomings of traditional multi-zone pressure control, which relies on experience-based "blind adjustment," enabling precise "visual and adjustable" adjustments. In addition, it solves the problem that traditional online monitoring of multi-zone pressure cannot distinguish between "central depression" and "edge warping," achieving "localized point repair."

[0041] This invention breaks the traditional technical prejudice that "the retaining ring must be fully rigid" by designing a "rigid-flexible" coupling design with a double-layer retaining ring. The outer rigid ring provides macroscopic support, while the inner flexible layer achieves microscopic self-adaptation.

[0042] Gas forms an "air cushion" through micropores, and the flexible inner layer expands slightly under gas pressure to increase the contact area, jointly reducing the contact pressure at the edge and indirectly reducing the wafer edge pressure. In addition, gas can be sprayed obliquely through the micropores to flush the polishing fluid retention area at the edge, and the porous structure of the flexible inner layer helps the polishing fluid to penetrate evenly, further alleviating the polishing fluid retention problem. The temperature adaptive compensation design of the shape memory polymer utilizes the material phase change characteristics to achieve "passive" shape adaptation, eliminating the need for complex sensors and actuators in the closed loop, thus reducing system complexity.

[0043] The three-dimensional coupled compensation control design, which combines gas "cushion" depressurization, liquid directional flushing, and material adaptive deformation, achieves a three-dimensional coupled compensation effect that far surpasses the superposition of single methods. Attached Figure Description

[0044] Figure 1 This is an integrated perspective view of the grinding and polishing machine provided in an embodiment of the present invention;

[0045] Figure 2 This is a three-dimensional structural diagram of the workpiece carrier provided in an embodiment of the present invention;

[0046] Figure 3 This is a bottom view of the workpiece carrier provided in an embodiment of the present invention;

[0047] Figure 4 This is a cross-sectional view of the polishing head at the bottom of the workpiece carrier provided in an embodiment of the present invention;

[0048] Figure 5 This is a bottom sectional view of the polishing head provided in an embodiment of the present invention;

[0049] Figure 6 yes Figure 4 A magnified view of the structure at point A in the middle;

[0050] Figure 7 yes Figure 4 A magnified view of the structure at point B in the middle;

[0051] Figure 8 yes Figure 4 A magnified view of the structure at point C in the middle;

[0052] Figure 9 This is a structural diagram of the flexible inner layer provided in an embodiment of the present invention;

[0053] Figure 10 This is a cross-sectional plan view of the rotary joint provided in an embodiment of the present invention;

[0054] Figure 11 This is a simplified diagram of the nanoscale online monitoring system provided in an embodiment of the present invention;

[0055] Figure 12 This is a connection diagram of the vacuum pump provided in an embodiment of the present invention;

[0056] Figure 13 This is a flowchart of the control method provided in an embodiment of the present invention.

[0057] The attached diagram lists the components represented by each number as follows:

[0058] 1. Grinding and polishing machine; 2. Rocker arm drive rod; 3. Mechanical rocker arm;

[0059] 4. Workpiece carrier; 401. Fixed carrier plate; 402. Connecting rod one; 403. Fixing ring; 404. Gravity pressurization assembly; 405. Connecting plate; 406. Connecting rod two; 407. Polishing head; 4071. Inner compartment; 4072. Adsorption air passage; 4073. Suction cup groove; 4074. Flexible membrane cavity; 4075. Air tube one; 408. Pressure gauge; 409. Rigid tube; 4091. Inner tube one; 4092. Inner air chamber; 4093. Inner tube two; 410. Miniature air pump; 411. Rigid support ring; 412. Flexible inner layer; 4121. Interference fit; 4122. Adhesion area; 4123. Air inlet; 4124. Annular air passage; 4125. Radial branch passage; 4126. Micropore;

[0060] 5. Vacuum pump; 501. Solenoid valve; 502. Inlet pipe one; 503. Inlet pipe two; 504. Outlet pipe one; 505. Outlet pipe two;

[0061] 6. Pressure sensor; 7. Electro-proportional valve; 701. Air tube 2;

[0062] 8. Rotary joint; 801. Housing; 802. Fluid pipe; 803. Connector 1; 804. Connector 2;

[0063] 9. Multi-channel fiber optic rotary connector;

[0064] 10. Fixed measurement unit; 1001. Laser source; 1002. Fiber optic coupler; 1003. Photodetector; 1004. Signal processing module;

[0065] 11. Rotating optical path unit; 1101. Fiber optic distribution plate; 1102. Independent optical measurement channel; 1103. Collimating lens; 1104. Focusing lens; 1105. Transparent window;

[0066] 12. Rotating optical fiber; 13. Optical fiber. Detailed Implementation

[0067] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0068] like Figures 1-12 As shown, a high-precision chemical mechanical polishing device for compound semiconductors includes a grinding and polishing machine 1, a workpiece carrier 4, and a vacuum pump 5. Rocker arm drive rods 2 are assembled on both sides of the grinding and polishing machine 1 through an internal power mechanism, and a mechanical rocker arm 3 is assembled on the surface of the grinding and polishing machine 1, which is detachably assembled with the rocker arm drive rods 2. The workpiece carrier 4 is placed inside the open end of the mechanical rocker arm 3, and the workpiece carrier 4 swings on the surface of the grinding disc through the mechanical rocker arm 3.

[0069] See attached document Figure 2 The workpiece carrier 4 also includes a fixed carrier plate 401. A fixed ring 403 is fixedly assembled at the bottom of the fixed carrier plate 401 via a connecting rod 402 arranged in an edge array. The polishing head 407 is assembled in a lifting manner on the inner side of the fixed ring 403. A connecting plate 405 is fixedly assembled at the top of the polishing head 407 via a connecting rod 406 arranged in an edge array. The connecting plate 405 and the connecting rod 402 form a sliding assembly relationship. A gravity pressure component 404 for adjusting the downward pressure of the polishing head 407 on the wafer is provided at the center of the surface of the fixed carrier plate 401. A pressure gauge 408 is assembled on one side of the gravity pressure component 404. A rigid tube 409 is fixedly connected at the center of the surface of the polishing head 407.

[0070] Example 1:

[0071] See attached document Figures 3-5 The workpiece carrier 4 also includes a polishing head 407, a flexible membrane cavity 4074 disposed below the polishing head 407, and N independent pressure partition chambers formed by partitioning, wherein N≥4, the pressure partition chambers are distributed in a concentric ring shape, and each pressure partition chamber is connected to the electric proportional valve 7 through an independent air pipe 4075.

[0072] See attached document Figure 5 , Figure 6 and Figure 8 The polishing head 407 has an integrally integrated inner compartment 4071, and a pressure sensor 6 is installed inside the inner compartment 4071 for real-time monitoring of the pressure values ​​of the pressure zones in each flexible membrane cavity 4074; the bottom of the rigid tube 409 has an inner air chamber 4092, and an inner tube 2 4093 is integrally integrated on one side inside the rigid tube 409, and the inner tube 2 4093 communicates with the inner air chamber 4092. The inner air chamber 4092 is connected to each electro-proportional valve 7 through an air tube 2 701.

[0073] See attached document Figures 5-8 The polishing head 407 has concentric ring-shaped adsorption channels 4072 inside, and the lower surface of the polishing head 407 has a suction cup groove 4073 corresponding to the bottom of each ring of adsorption channels 4072; an inner tube 4091 is integrally provided on one side inside the rigid tube 409, and the inner tube 4091 extends into the polishing head 407 and communicates with all the adsorption channels 4072.

[0074] See attached document Figure 10 A rotary joint 8 is assembled at the top end of the rigid tube 409. The fixed end of the rotary joint 8 is the housing 801, and the rotating end is the fluid tube 802. The fluid tube 802 is rotatably assembled inside the housing 801. The top end of the rigid tube 409 is connected to the bottom end of the fluid tube 802. The fluid tube 802 has two channels, one and two, which communicate with the inner tube 4091 and the inner tube 4093, respectively. The outer wall of the housing 801 is provided with two connecting pipes, one 803 and the other 804, which communicate with the channels 1 and 2, respectively.

[0075] See attached document Figure 12 The vacuum pump 5 is equipped with solenoid valves 501 at both the input and output ends. One solenoid valve 501 has two other ports with inlet pipe 1 502 and inlet pipe 2 503 respectively. The other solenoid valve 501 has two other ports with outlet pipe 1 504 and outlet pipe 2 505 respectively. Inlet pipe 1 502 is connected to pipe 1 803 through a pipe, and outlet pipe 1 504 is connected to pipe 2 804 through a pipe.

[0076] According to the above structure, the pressure sensor 6 collects the pressure value of the internal chamber of each flexible membrane cavity 4074 in real time, and transmits it to the control system CPU through A / D conversion. The CPU compares the measured value with the set value, calculates the pressure deviation, and outputs a control signal through D / A conversion to adjust the opening of the electro-proportional valve 7. Each flexible membrane cavity 4074 converts the air pressure into pressure on the back side of the wafer, and acts directly on the back side of the wafer through the flexible membrane at the bottom. This adjustment and control process is continuously cyclical to keep the pressure of each zone stable at the set value. Each flexible membrane cavity 4074 corresponds to an annular zone of the wafer and can independently apply different pressures. By adjusting the pressure of different areas, the edge effect and the difference in center-edge removal rate during the polishing process can be compensated. Since this "multi-zone pressure control polishing head" is a public technology, it will not be described in detail here.

[0077] It is worth noting that when the wafer is fixed to the lower surface of the polishing head 407 by vacuum adsorption, the vacuum pump 5 operates and, through the inlet pipe 502 and the connecting pipe 803, keeps the inner pipe 4091 and all the adsorption air channels 4072 under negative pressure, thereby achieving the effect of adsorbing and fixing the wafer. When it is necessary to inject gas into the corresponding flexible membrane cavity 4074 to increase the chamber pressure, one of the solenoid valves 501 controls the inlet pipe 503 to be connected to the input end of the vacuum pump 5, and closes the inlet pipe 502 to maintain the negative pressure state. The other solenoid valve 501 controls the outlet pipe 504 to be connected to the output end of the vacuum pump 5. When the vacuum pump 5 is operating, it can draw in outside air and pass it through the outlet pipe 504, the connecting pipe 804, the inner pipe 4093, and the inner air chamber 4092 in sequence, and finally inject it into the corresponding flexible membrane cavity 4074 through the corresponding air pipe 701 to increase the air pressure.

[0078] See attached document Figure 4 , Figure 5 as well as Figure 11 The nanoscale online monitoring system includes a fixed measurement unit 10, a rotating optical path unit 11, and an optical signal transmission unit. The optical paths of the fixed measurement unit 10 and the rotating optical path unit 11 pass through the flexible membrane cavity 4074 and point to the surface of the workpiece to be polished, which can acquire nanoscale thickness distribution data of the workpiece surface in real time.

[0079] The nanometer-scale online monitoring system adopts a split architecture, including:

[0080] The fixed measurement unit 10 is installed on the top non-rotating part of the fixed carrier plate 401 and includes a laser source 1001, an optical fiber coupler 1002, a photodetector 1003 and a signal processing module 1004.

[0081] The rotating optical path unit 11 is integrated inside the polishing head 407 and rotates synchronously with the polishing head 407. The rotating optical path unit 11 includes N+1 sets of independent optical measurement channels 1102. The optical fiber, lens group and transparent window 1105 of each set of independent optical measurement channels 1102 are distributed in concentric circles along the radial direction of the polishing head 407. The lens group includes a collimating lens 1103 and a focusing lens 1104. Except for the independent optical measurement channel 1102 located at the center, it is aligned with the radial geometric center line of the corresponding pressure partition chamber to ensure that the measurement spot falls in the area where the pressure of the partition is most uniform. The independent optical measurement channel 1102 and the flexible membrane cavity 4074 do not overlap radially to achieve "pressure measurement without interference". The polishing head 407 is provided with an optical fiber distribution disk 1101 at the top of the circular axis, and the optical fiber distribution disk 1101 is fixed to the tail end of the rotating optical fiber 12.

[0082] The optical signal transmission unit adopts a multi-channel optical fiber rotary connector 9. Its fixed end is connected to the optical fiber coupler 1002 through optical fiber 13, and its rotating end is connected to the optical fiber distribution disk 1101 through rotating optical fiber 12, so as to realize low-loss optical signal transmission in the rotating state.

[0083] According to the above structure, the laser emission path is as follows: a laser with excellent monochromaticity is emitted by the laser source 1001 as the reference wavelength for interferometric measurement. The incident light is then split into reference light and measurement light by the fiber coupler 1002 and directed onto the wafer surface. The splitting ratio is set to 1:N+1. The reference light is directly reflected back to the photodetector 1003. Each measurement light beam enters N+1 rotating optical fibers 12 through the multi-channel fiber optic rotary connector 9 and finally enters the corresponding independent optical measurement channel 1102. The collimating lens 1103 in each lens group converts the diverging fiber-emitting light into parallel light to ensure that the light spot does not spread during long-distance transmission. The focusing lens 1104 slightly focuses the parallel light onto the wafer surface to improve the return light energy density and enhance the signal-to-noise ratio. In addition, the transparent window 1105 is made of high-hardness quartz glass or sapphire material and is vulcanized and bonded to the flexible film or mechanically pressed to ensure that the window area maintains optical flatness when the airbag is deformed by pressure and does not interfere with the deformation of the pressure chamber.

[0084] Each set of measurement beams is ultimately directed uniformly toward the interface between the thin film and the substrate on the wafer surface;

[0085] The path for receiving reflected light is as follows: the reflected light from the wafer surface passes sequentially through the transparent window 1105 → corresponding lens group → corresponding rotating optical fiber 12 → multi-channel optical fiber rotary connector 9 → optical fiber coupler 1002 → photodetector 1003. The photodetector 1003 receives the interference light signal reflected from the wafer surface and converts the light intensity change into an analog electrical signal. The signal processing module 1004 includes ADC conversion, FFT spectrum analysis, and phase calculation circuits, and outputs thickness data in real time.

[0086] The closed-loop control system, electrically connected to the electro-proportional valve 7 and the nanoscale online monitoring system, is configured to: receive nanoscale thickness distribution data, calculate the material removal rate deviation of the workpiece area corresponding to each pressure zone chamber, and dynamically adjust the output pressure of each electro-proportional valve according to the deviation to achieve real-time correction of the workpiece surface flatness.

[0087] The closed-loop control system includes: a data acquisition unit that acquires nanometer-level thickness distribution data with a sampling period of 1-10ms; an error calculation unit that compares the real-time thickness distribution data with the target thickness distribution and calculates the thickness deviation of the corresponding area of ​​each pressure zone; a pressure compensation calculation unit that calculates the pressure adjustment amount of each zone based on the improved Preston equation; and a pressure output unit that converts the calculated pressure adjustment amount into a control voltage signal for an electro-proportional valve.

[0088] Based on the above structure, for details regarding the specific operation process of this embodiment one, please refer to the following control method for a high-precision chemical mechanical polishing device for compound semiconductors.

[0089] The working principle and typical application scenarios of this invention:

[0090] Scenario 1: Global planarization, aiming to achieve uniform thin film removal across the entire wafer surface, can be achieved using a polishing strategy with slightly higher pressure in the central area and decreasing pressure at the edges; Scenario 2: Targeted correction, aiming to correct morphological defects in specific areas, can be achieved by adjusting the pressure zones corresponding to the defective areas to achieve precise local correction; Scenario 3: Multi-material composite polishing, aiming to polish different materials simultaneously, such as copper + dielectric layer, can be achieved by applying different pressures to different material areas to balance the differences in removal rates;

[0091] By integrating a "multi-zone pressure-controlled polishing head" with nanoscale online monitoring technology, when the nanoscale online monitoring system detects that the wafer edge removal rate is too fast, the system reduces the inflation pressure of the corresponding pressure zone in real time to correct the edge effect and achieve closed-loop control. This monitoring system not only performs monitoring but also commands the "multi-zone pressure-controlled polishing head," achieving millisecond-level response. In addition, nanoscale sensors are cleverly arranged inside the rotating multi-zone air chamber. This structure provides the conditions for nanoscale monitoring, solves the signal interference problem of sensor cables during rotation, and utilizes the fluid dynamics of polishing fluid to protect the sensors, solving the problems of spatial interference and signal crosstalk that would arise when the two coexist.

[0092] Example 2

[0093] See attached document Figures 4-6The edge effect active compensation structure includes a rigid support ring 411, a flexible inner layer 412, and an integrated microchannel. Based on the edge pressure and thickness signals, it performs air cushion depressurization / liquid flushing / morphological adaptive compensation actions through the integrated microchannel.

[0094] The rigid support ring 411 is fixedly connected to the outer edge of the polishing head 407 via a flange. The flexible inner layer 412 is nested inside the rigid support ring 411. The surface of the flexible inner layer 412 is integrally formed with an array of interference fit bodies 4121. The interference fit bodies 4121 and the interior of the rigid support ring 411 form a fitted interference fit assembly relationship. The surface of the flexible inner layer 412 without the interference fit bodies 4121 is bonded to the inner wall of the rigid support ring 411 through the adhesive area 4122. The interior of the flexible inner layer 412 is filled with a micro heater.

[0095] The integrated microchannel is disposed inside the flexible inner layer 412 and includes an annular air channel 4124, radial branch channels 4125 and an array of micropores 4126. The interference fit body 4121 has an air inlet channel 4123 for supplying air to the integrated microchannel. The radial branch channels 4125 communicate with the annular air channel 4124 and the micropores 4126 are disposed at the end of the radial branch channels 4125.

[0096] The outlet of the microporous 4126 array is obliquely pointed at an angle of 30°-45°. The gap between the inner edge of the flexible inner layer 412 and the edge of the wafer is 0.5-2mm, and the concentricity is ≤20μm. The flexible inner layer 412 is made of a porous shape memory polymer with a compression deformation of 0.1-0.3mm and a resilience of ≥95%. The phase transition temperature of the shape memory polymer is 35-45℃, and the porosity of the flexible inner layer 412 is 30-50%.

[0097] A miniature air pump 410 is fixedly installed in the middle of the surface of the polishing head 407. The air outlet of the miniature air pump 410 is connected to the inside of the rigid support ring 411 through a pipe.

[0098] Based on the above structure, in scenario 1: the pressure sensor 6 monitors the distribution of wafer contact pressure in real time. When the wafer edge pressure is detected to be too high, the micro air pump 410 is turned on to inject low-pressure gas into the integrated microchannel. The gas forms an "air cushion" through the micropores 4126, which locally reduces the contact pressure at the edge. At the same time, the flexible inner layer 412 expands slightly under the air pressure, increasing the contact area and indirectly reducing the wafer edge pressure, while the rigid support ring 411 provides macroscopic support.

[0099] Scenario 2: When polishing slurry is found to be stuck at the edge of the wafer, the micro air pump 410 can be activated to inject low-pressure gas into the integrated microchannel. The gas is sprayed obliquely through the micropores 4126 to flush the stuck edge area. The porous structure of the flexible inner layer 412 helps the polishing slurry to penetrate evenly, further alleviating the problem of polishing slurry stuck.

[0100] Scenario 3: Achieving micro-adaptation. When an abnormal edge morphology is detected by a nanoscale online monitoring system, a micro heater is activated to heat up the shape memory polymer. After the material softens, it adapts to the edge morphology of the wafer and re-establishes uniform contact, thus achieving micro-adaptation.

[0101] Based on the above, a "rigid-flexible" coupling design with a double-layer retaining ring is designed. The outer rigid ring provides macroscopic support, while the inner flexible layer achieves microscopic self-adaptation, breaking the traditional technical prejudice that "the retaining ring must be fully rigid." The "ring + radial" topology design of the annular air passage 4124 and micropores 4126 ensures balanced flow, while the radial branch passages 4125 achieve precise spatial coverage. The oblique injection angle of the micropores 4126 maximizes the edge scouring effect. The temperature adaptive compensation design of the shape memory polymer utilizes the material's phase change characteristics to achieve "passive" morphological adaptation, eliminating the need for complex sensors and actuators in the closed loop, thus reducing system complexity. The three-dimensional coupling compensation and control design combines gas "cushion" depressurization, liquid directional scouring, and material adaptive deformation, with three-dimensional coupling compensation, resulting in effects far exceeding the superposition of single methods.

[0102] like Figure 13 As shown, a control method for a high-precision chemical mechanical polishing (CMP) device for compound semiconductors includes the following specific steps;

[0103] S1: Initialization and Baseline Establishment Phase

[0104] The upper control system reads the process formula file and sets the target thickness distribution matrix. Preset polishing time T, polishing head rotation speed Grinding disc rotation speed Load real-time control memory;

[0105] Send an initial voltage command to the electro-proportional valve 7 to establish the reference air pressure for each pressure zone chamber. Where i=1,2,...,N, and the actual value is fed back through pressure sensor 6 to complete the zero-point calibration of the actuator;

[0106] Initialize PID controller parameters ( , , Clear the Preston coefficient K and the integrator / differentiator history status register, and clear the thickness deviation accumulation queue.

[0107] Furthermore, confirm that the laser source 1001 has stable power, the photodetector 1003 has a signal-to-noise ratio that meets the standard, and the fiber optic rotary connector 9 has a smooth communication link. If any hardware status is abnormal, the security interception logic is triggered, and entry into the polishing cycle is refused. If all are ready, the "run allowed" flag is set, and the process jumps to S2.

[0108] S2: High-frequency data acquisition and signal preprocessing stage

[0109] Nanoscale online monitoring system with a fixed sampling rate (≥1kHz) The reflected light intensity signal from the wafer surface is captured. The analog voltage signal is converted by a high-speed ADC and then enters the digital signal processing unit. The processing unit performs a fast Fourier transform (FFT) on the time-domain interference fringes to extract the phase change and combine it with the laser wavelength. Solving for instantaneous absolute thickness value ;

[0110] By introducing temperature drift compensation and vibration filtering algorithms, environmental noise is eliminated, and spatially resolved real-time thickness distribution data is output. The data resolution is locked at ≤0.1nm; the spindle encoder signal is acquired synchronously, and the thickness data is compared with the polishing head rotation angle. Perform timestamp alignment to generate a thickness stream with angle labels;

[0111] Furthermore, if the signal-to-noise ratio is below the threshold or an outlier occurs for three consecutive sampling cycles, the "data resampling" logic is triggered, pausing the pressure adjustment command output to prevent malfunctions; after preprocessing is completed, the cleaned thickness dataset is pushed to the error calculation module, triggering S3.

[0112] S3: Spatial Error Mapping and Deviation Calculation Stage

[0113] The control system is based on 407N pressure zones of the polishing head. To determine the geometric coverage area, establish a spatial mask matrix. Real-time thickness map Multiply point-by-point with each partition mask and in the corresponding region Perform area integral calculations to calculate the average thickness deviation of each zone:

[0114] ;

[0115] Output N-dimensional error vector And cache it in the sliding time window for use in integration and differentiation operations;

[0116] Furthermore, since the wafer continuously rotates relative to the measurement spot, the system performs a circumferential average of multiple measurements at the same spatial coordinates within a single cycle, eliminating instantaneous local fluctuations and extracting the true radial thickness gradient; among which, A value greater than 0 indicates that there is excess material in the area (which needs to be removed by applying pressure). <0 indicates that the material has been excessively removed (removal needs to be suppressed by decompression), providing directional instructions for S4.

[0117] S4: Core Control Algorithm Calculation Stage

[0118] Error vector The input is fed into an improved PID controller, which calculates the proportional, integral, and derivative terms respectively, and synthesizes the base pressure adjustment.

[0119] ;

[0120] Introducing Preston material to remove kinetic corrections: Reading the current relative linear velocity distribution Calculate the velocity weighting factor for each partition and perform inverse dynamic scaling on the base adjustment amount: This ensures an equivalent material removal response in both high-speed and low-speed regions.

[0121] Furthermore, execute the gain scheduling logic: based on The amplitude is automatically switched using PID parameter groups (large gain for fast convergence with large deviations, and small gain for overshoot suppression with small deviations), outputting the final pressure compensation instruction set. ;

[0122] Furthermore, the integral term eliminates steady-state thickness shifts, the differential term suppresses surface ripples caused by sudden pressure changes, and Preston corrects the nonlinear effect of the decoupled velocity field on the removal rate; the calculated... If the physical limits of the equipment are exceeded (such as the upper limit of air pressure or the yield threshold of the flexible membrane), saturation cutoff is performed and the limiting event is recorded for analysis by S7; after the calculation is completed, the digital pressure command is packaged and sent to the D / A conversion module, triggering S5.

[0123] S5: Pressure Command Output and Actuator Drive Stage

[0124] D / A converter will Convert to high-precision analog voltage Superimposed on the reference voltage The voltage signal drives the corresponding proportional valve 7 of the partition, adjusting the valve core opening and changing the air flow rate. Compressed air is transmitted losslessly through the multi-channel rotary joint to the corresponding pressure partition chamber at the rotating end. The flexible membrane chamber 4074 is pressurized and generates a micron-level normal displacement, converting the air pressure into contact stress acting on the back of the wafer. The internal compartment 4071 has a built-in pressure sensor 6 that reads back the actual air pressure in real time. This forms a valve-controlled inner loop;

[0125] Furthermore, comparison If the deviation from the command value is greater than 0.1 kPa, the proportional valve will perform fine-tuning compensation to ensure that the assumptions of the outer loop control algorithm are met.

[0126] Furthermore, control cycle It must match the time constant of the pneumatic system to avoid system oscillation caused by phase lag. If pressure step response overshoot is detected, a damping filter is automatically inserted.

[0127] S6: Convergence Determination and State Transition Stage

[0128] The control system for the current period thickness distribution Statistical analysis was performed to calculate the intra-slice non-uniformity index: ;in Standard deviation, The global average thickness is calculated, while the total polishing time is also accumulated. Compare WIWNU with a preset convergence threshold (e.g., 1.5%) and check. Has the upper limit T been reached?

[0129] Furthermore, when WIWNU ≤ threshold or When T is greater than or equal to T, the polishing is determined to be up to standard or timed out. The dynamic adjustment of pressure is stopped, a "polishing complete" signal is output, and the process jumps to S7 (data archiving). Otherwise, the process is determined to be non-converged, the integrator saturation state is cleared, the PID history queue is refreshed, and the process is forced to return to S2 to start the next control cycle.

[0130] S7: Process Data Accumulation and Model Self-Evolution Stage

[0131] The entire polishing cycle data (initial morphology, pressure adjustment trajectory, thickness evolution curve, final WIWNU, surface defect map) was packaged, encrypted, and written into the process database. A background learning engine was then activated, employing recursive least squares (RLS) or a lightweight neural network to fit the residuals between the actual removal behavior and the Preston model. The Preston coefficient K was corrected, and the PID gain group was optimized. Generate a new generation of process formula index;

[0132] Furthermore, when replacing with new materials or wafers of new sizes, the system automatically retrieves historical similar operating conditions, loads pre-trained weights, and can quickly converge to the optimal control parameters with only ≤5 trial throws. This step does not block the main control loop and runs in an asynchronous thread, achieving an adaptive manufacturing capability that becomes more accurate with use.

[0133] The working principle of this method is as follows: Based on nanometer monitoring data and combined with the pressure distribution map of multiple zones, a dynamic real-time thickness map that changes over time is constructed. Unlike the existing "offline monitoring" or "macro monitoring" technologies for multi-zone pressure control, this method uses "nanoscale" (e.g., resolution <1nm) and "in-situ real-time detection" techniques. "Nanometer-scale" monitoring is more likely to detect local micro-protrusions than "micrometer-scale" monitoring. Moreover, this combination of techniques solves the defect of traditional multi-zone pressure control based on experience-based "blind adjustment" and achieves precise "visual and adjustable" adjustment. In addition, it also solves the problem that traditional online monitoring of multi-zone pressure cannot distinguish between "central depression" and "edge warping" and achieves "local fixed-point repair".

[0134] A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the above-described control method.

[0135] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the control method described above when executing the program.

[0136] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A high-precision chemical mechanical polishing device for compound semiconductors, comprising a grinding and polishing machine (1), a workpiece carrier (4), and a vacuum pump (5), characterized in that: The workpiece carrier (4) also includes a polishing head (407), a flexible membrane cavity (4074) disposed below the polishing head (407), and N independent pressure partition chambers formed by partitioning, wherein N≥4, the pressure partition chambers are distributed in a concentric ring shape, and each pressure partition chamber is connected to an electric proportional valve (7) through an independent air pipe (4075). The nanoscale online monitoring system includes a fixed measurement unit (10), a rotating optical path unit (11), and an optical signal transmission unit. The optical paths of the fixed measurement unit (10) and the rotating optical path unit (11) pass through the flexible membrane cavity (4074) and point to the surface of the workpiece to be polished, which can acquire nanoscale thickness distribution data of the workpiece surface in real time. The closed-loop control system, electrically connected to the electro-proportional valve (7) and the nanoscale online monitoring system, is configured to: receive nanoscale thickness distribution data, calculate the material removal rate deviation of the workpiece area corresponding to each pressure zone chamber, and dynamically adjust the output pressure of each electro-proportional valve according to the deviation to realize real-time correction of the workpiece surface flatness; The edge effect active compensation structure includes a rigid support ring (411), a flexible inner layer (412), and an integrated microchannel. Based on the edge pressure and thickness signals, it performs air cushion depressurization / liquid flushing / morphological adaptive compensation actions through the integrated microchannel.

2. The high-precision CMP apparatus for a compound semiconductor according to claim 1, characterized by: The workpiece carrier (4) also includes a fixed carrier plate (401), and a fixed ring (403) is fixedly assembled at the bottom of the fixed carrier plate (401). The polishing head (407) is assembled in a lifting manner on the inner side of the fixed ring (403). The polishing head (407) has an integrally provided inner compartment (4071), and a pressure sensor (6) is installed inside the inner compartment (4071) for real-time monitoring of the pressure value of the pressure zone chamber in each flexible membrane cavity (4074).

3. The high-precision chemical mechanical polishing equipment for compound semiconductors according to claim 2, characterized in that: The nanoscale online monitoring system adopts a split architecture, including: The fixed measurement unit (10) is installed on the non-rotating part of the top of the fixed carrier plate (401) and includes a laser source (1001), an optical fiber coupler (1002), a photodetector (1003) and a signal processing module (1004). A rotating optical path unit (11) is integrated inside the polishing head (407) and rotates synchronously with the polishing head (407). The rotating optical path unit (11) includes N+1 independent optical measurement channels (1102). The optical fiber, lens group and transparent window (1105) of each independent optical measurement channel (1102) are arranged in concentric circles along the radial direction of the polishing head (407). The lens group includes a collimating lens (1103) and a focusing lens (1104). An optical fiber distribution disk (1101) is provided inside the polishing head (407) and located at the top of the circular axis. The optical fiber distribution disk (1101) is fixed to the tail end of the rotating optical fiber (12). The optical signal transmission unit adopts a multi-channel optical fiber rotary connector (9), with its fixed end connected to the optical fiber coupler (1002) via optical fiber (13) and its rotating end connected to the optical fiber distribution disk (1101) via rotating optical fiber (12), thereby realizing low-loss optical signal transmission in the rotating state.

4. The high-precision chemical mechanical polishing equipment for compound semiconductors according to claim 3, characterized in that: The closed-loop control system includes: The data acquisition unit acquires nanometer-scale thickness distribution data with a sampling period of 1-10ms; The error calculation unit compares the real-time thickness distribution data with the target thickness distribution and calculates the thickness deviation of the corresponding area of ​​each pressure zone. The pressure compensation calculation unit calculates the pressure adjustment amount for each zone based on the improved Preston equation; The pressure output unit converts the calculated pressure adjustment amount into a control voltage signal for the electro-proportional valve.

5. The high-precision chemical mechanical polishing equipment for compound semiconductors according to claim 1, characterized in that: The rigid support ring (411) is fixedly connected to the outer edge of the polishing head (407) by a flange. The flexible inner layer (412) is nested inside the rigid support ring (411). The integrated microchannel is disposed inside the flexible inner layer (412), and the interior of the flexible inner layer (412) is filled with a micro heater.

6. The high-precision chemical mechanical polishing equipment for compound semiconductors according to claim 5, characterized in that: The integrated microchannel includes an annular air channel (4124), radial branch channels (4125), and a micropore (4126) array, with the outlet of the micropore (4126) array pointing obliquely at an angle of 30°-45°.

7. The high-precision chemical mechanical polishing equipment for compound semiconductors according to claim 6, characterized in that: The gap between the inner edge of the flexible inner layer (412) and the edge of the wafer is 0.5-2mm, and the concentricity is ≤20μm; The flexible inner layer (412) is made of a porous shape memory polymer with a compression deformation of 0.1-0.3 mm, a resilience of ≥95%, and a phase transition temperature of 35-45℃. The flexible inner layer (412) has a body porosity of 30-50%.

8. A control method for a high-precision chemical mechanical polishing (CMP) apparatus for compound semiconductors, using the high-precision CMP apparatus as described in any one of claims 1-7, characterized in that, The specific steps are as follows: S1: Set the target thickness distribution Polishing time T, polishing head rotation speed Grinding disc rotation speed Read the initial pressure setpoint of each pressure zone chamber. ; S2: Activate the nanoscale online monitoring system, with a sampling cycle. Capture the reflected light intensity signal from the wafer surface and calculate the instantaneous absolute thickness value. By introducing temperature drift compensation and vibration filtering algorithms, spatially resolved real-time thickness distribution data is output. Combine thickness data with polishing head rotation angle Perform timestamp alignment to generate a thickness stream with angle labels; S3: Calculate the average thickness deviation of the corresponding area for each pressure zone. ; S4: Calculate the pressure adjustment amount for each zone based on the improved PID control algorithm. The Preston equation correction term is introduced to perform inverse dynamic scaling of the adjustment amount and output. ; S5: Calculate the pressure adjustment amount The compressed air is converted into the control voltage of the electric proportional valve (7), and the compressed air is transmitted to the corresponding pressure partition chamber through the multi-channel rotary joint. The air pressure is converted into contact stress acting on the back of the wafer. S6: Calculate the flatness index of the current workpiece surface. ,like If the set threshold or polishing time reaches T, then polishing ends; otherwise, return to step S2 to continue the loop. S7: Store the process parameters, thickness evolution data, and final results of this polishing process in the process database.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the control method as described in claim 8.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the control method as described in claim 8.

Images