Polishing method based on edge area online monitoring and dynamic pressure compensation

Abstract

The invention relates to a polishing method based on edge area online monitoring and dynamic pressure compensation, which belongs to the technical field of semiconductor wafer processing, and comprises the following operation steps of: 1, adsorbing a wafer under a partitioned pressure-controllable polishing head; and 2, enabling the surface of the wafer to be in contact with a polishing pad, supplying a polishing solution, and starting a polishing process. And thirdly, in the polishing process, the edge optical monitor is used for conducting real-time and in-situ measurement on the thickness of the film in the edge area of the wafer. And 4, transmitting the film thickness data, measured in real time, of the edge area to a control machine. 5, the control machine carries out data comparison, if the removal rate of the edge area is lower than a target value, a control instruction is generated, and the applied pressure of the edge pressure area is dynamically increased; otherwise, the pressure is correspondingly reduced. And sixthly, the third step to the fifth step are repeated till the main polishing end point is reached. Through a real-time monitoring-decision-execution closed-loop control loop, insufficient polishing of the wafer edge is actively and dynamically compensated.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer processing technology, and more specifically to a polishing method based on online monitoring of edge regions and dynamic pressure compensation. Background Technology

[0002] In semiconductor CMP processes, the polishing rate at the wafer edges is typically lower than that at the center, resulting in excessive residual material at the edges after polishing—a phenomenon known as the "edge effect" or "edge collapse." This problem stems from: 1. Mechanical factors: During the polishing process, insufficient rigid support at the wafer edge and reduced effective contact pressure due to edge deformation of the polishing pad.

[0003] 2. Hydrodynamic factors: Polishing fluid is difficult to retain at the edge of a high-speed rotating wafer, resulting in insufficient chemical reaction and lubrication in this area.

[0004] 3. Monitoring blind zone: Traditional endpoint detection systems based on motor current or optical interference mainly originate from the main area of ​​the wafer and are not sensitive to changes in the edge area.

[0005] Edge effects can lead to: 1. Defocusing occurs in subsequent photolithography processes, affecting the accuracy of pattern transfer.

[0006] 2. This results in uneven film thickness, affecting the consistency of device electrical parameters.

[0007] 3. Reduce the final yield of the chip, especially in the wafer edge area. Summary of the Invention

[0008] This invention primarily addresses the shortcomings of existing technologies by providing a polishing method based on online monitoring and dynamic pressure compensation of the edge region. Through a closed-loop control circuit of "real-time monitoring-decision-execution," it actively and dynamically compensates for insufficient polishing at the wafer edge, fundamentally solving the edge effect problem. It achieves closed-loop control of edge polishing, representing a technological leap from "feedforward" to "feedback." It also solves the problem of uneven material removal rate (MRR) in the wafer edge region during chemical mechanical polishing.

[0009] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions: A polishing method based on online edge region monitoring and dynamic pressure compensation, wherein the chemical mechanical polishing apparatus includes a lower frame, an upper frame at the upper end of the lower frame, a control unit placed on the upper end of the lower frame inside the upper frame, a wafer at the upper end of the control unit, a polishing pad between the control unit and the wafer, an edge optical monitor at the upper end of the wafer that is electrically connected and fixed to the upper frame, and a zoned controllable pressure polishing head at the lower end of the edge optical monitor.

[0010] The polishing method based on online edge region monitoring and dynamic pressure compensation includes the following steps: Step 1: Place the wafer under the partitioned controllable pressure polishing head.

[0011] Step 2: Make the wafer surface come into contact with the polishing pad and supply polishing fluid to begin the polishing process.

[0012] Step 3: During the polishing process, the thin film thickness in the wafer edge area is measured in real time and in situ using an edge optical monitor integrated into the edge of the polishing pad stage.

[0013] Step 4: Transmit the real-time measured film thickness data of the edge area to the control unit.

[0014] Step 5: The control unit compares the real-time film thickness data with the preset ideal removal rate curve. If the removal rate in the edge region is lower than the target value, a control command is generated to dynamically increase the pressure applied to the edge pressure zone; otherwise, the pressure is reduced accordingly.

[0015] Step 6: Repeat steps 3 through 5 until the main polishing endpoint is reached.

[0016] Preferably, the polishing pad stage is provided with a machine base guard plate that is snapped into and connected to the control machine base, and the machine base guard plate is made of transparent material.

[0017] Preferably, the polishing pad stage is equipped with a spectrometer fixedly connected to the machine base guard plate on its side, and the partitioned controllable pressure polishing head is equipped with a light source lamp on its side.

[0018] Preferably, the edge optical monitor is located in the outer 1 / 4 area of ​​the polishing pad stage, corresponding to the edge position of the wafer during polishing; the edge optical monitor works in conjunction with the light source lamp and the spectrometer to measure the film thickness on the lower surface of the wafer that it passes through through the transparent machine guard plate.

[0019] Preferably, the partitioned controllable pressure polishing head consists of a central pressure zone and an edge pressure zone, with the edge pressure zone forming a ring structure surrounding the central pressure zone.

[0020] Preferably, the control unit is connected to the edge optical monitor and the partitioned controllable pressure polishing head by a signal connection. It is configured to receive film thickness data, calculate the pressure adjustment amount based on a preset algorithm, and send pressure control commands to the edge pressure zone.

[0021] As a preferred option, the control algorithm of the control machine is proportional-integral-derivative (PID) control, with the goal of making the measured removal rate of the edge region track the preset ideal rate curve.

[0022] The present invention can achieve the following effects: This invention provides a polishing method based on online edge region monitoring and dynamic pressure compensation. Compared with existing technologies, it is an enhancement based on existing advanced partitioned pressure polishing head technology, requiring no radical changes to the main polishing head structure. The main improvements are the integrated edge monitoring module and corresponding control software, which are easily implemented on existing equipment platforms. It can automatically compensate for process drift caused by factors such as polishing pad aging, polishing slurry performance fluctuations, or differences in wafer thickness, resulting in a wider process window and higher stability.

[0023] Online monitoring: Using optical methods to measure the film thickness at the wafer edge in real time and in situ.

[0024] Dynamic comparison: The real-time measured thickness data is compared with the preset ideal removal rate to determine whether the current polishing state is too fast or too slow.

[0025] Dynamic compensation: Based on the comparison results, the polishing pressure applied to the edge region of the wafer is adjusted independently and dynamically to precisely control its removal rate. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the present invention.

[0027] In the diagram: 1. Upper rack, 2. Wafer, 3. Edge optical monitor, 4. Partition controllable pressure polishing head, 5. Light source lamp, 6. Spectrometer, 7. Machine guard plate, 8. Control machine, 9. Polishing pad stage, 10. Lower rack. Detailed Implementation

[0028] The technical solution of the invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0029] Example: Figure 1As shown, a polishing method based on online edge region monitoring and dynamic pressure compensation is disclosed. The chemical mechanical polishing apparatus includes a lower frame 10, with an upper frame 1 at the upper end of the lower frame 10. A control platform 8 is placed on the upper end of the lower frame 10 within the upper frame 1. A wafer 2 is placed on the upper end of the control platform 8. A polishing pad 9 is placed between the control platform 8 and the wafer 2. An edge optical monitor 3, electrically connected and fixed to the upper frame 1, is located on the upper end of the wafer 2. A zoned controllable pressure polishing head 4 is located below the edge optical monitor 3. The zoned controllable pressure polishing head 4 consists of a central pressure zone and an edge pressure zone, with the edge pressure zone forming a ring structure surrounding the central pressure zone. A machine base plate 7, made of transparent material, is snap-fitted to the control platform 8 around the polishing pad 9. A spectrometer 6, fixedly connected to the machine base plate 7, is located on the side of the polishing pad 9. A light source 5 is located on the side of the zoned controllable pressure polishing head 4.

[0030] The polishing method based on online edge region monitoring and dynamic pressure compensation includes the following steps: Step 1: Place wafer 2 under the partitioned controllable pressure polishing head 4.

[0031] Step 2: Make the surface of wafer 2 contact with the polishing pad and supply polishing fluid to start the polishing process.

[0032] Step 3: During the polishing process, the edge optical monitor 3 integrated into the edge of the polishing pad stage 9 is used to measure the film thickness in real time and in situ in the edge region of the wafer 2.

[0033] The edge optical monitor 3 is located in the outer 1 / 4 area of ​​the polishing pad stage 9, corresponding to the edge position of the wafer 2 during polishing. The edge optical monitor 3 works in conjunction with the light source lamp 5 and the spectrometer 6 to measure the film thickness on the lower surface of the wafer 2 that it passes through through the transparent machine guard plate 7.

[0034] Step 4: Transmit the real-time measured film thickness data of the edge area to the control unit 8.

[0035] The control unit 8 is connected to the edge optical monitor 3 and the zoned controllable pressure polishing head 4 by a signal connection. It is configured to receive film thickness data, calculate the pressure adjustment amount based on a preset algorithm, and send pressure control commands to the edge pressure zone.

[0036] The control algorithm of the control unit 8 is proportional-integral-derivative (PID) control, with the goal of making the measured removal rate of the edge region track the preset ideal rate curve.

[0037] Step 5: The control unit 8 compares the real-time film thickness data with the preset ideal removal rate curve. If the removal rate in the edge region is lower than the target value, a control command is generated to dynamically increase the pressure applied to the edge pressure zone; otherwise, the pressure is reduced accordingly.

[0038] Step 6: Repeat steps 3 through 5 until the main polishing endpoint is reached.

[0039] In summary, this polishing method based on online edge region monitoring and dynamic pressure compensation actively and dynamically compensates for insufficient polishing at wafer edges through a closed-loop control circuit of "real-time monitoring-decision-execution," fundamentally solving the edge effect problem. It achieves closed-loop control of edge polishing, representing a technological leap from "feedforward" to "feedback." It improves global flatness and yield: by ensuring that the edge and center regions reach the polishing endpoint synchronously, it significantly improves the film uniformity across the entire wafer surface, thereby directly improving the yield of chips, especially edge chips.

[0040] This solution addresses a key industry pain point: the "edge effect" in CMP (Chip Motion Processing) is a prevalent problem that leads to poor wafer edge flatness, impacting chip yield.

[0041] This solution achieves true "in-situ" control: traditional methods involve "offline measurement followed by adjustment," which is inefficient and inaccurate. This solution implements real-time closed-loop control by "polishing, measuring, and adjusting simultaneously," significantly improving control accuracy and efficiency.

[0042] The structure is ingeniously designed: through the layout of the transparent protective plate, edge light source and spectrometer, an effective optical measurement path is opened up without interfering with the core polishing process, demonstrating excellent system integration design capabilities.

[0043] The control strategy is mature and reliable: It adopts the PID control algorithm, which is technically mature, easy to implement, and has a stable and reliable control effect, reducing technical risks.

[0044] Improve product yield and consistency: By precisely controlling the edge removal rate, the flatness and uniformity of the entire wafer can be significantly improved, thereby improving the yield and performance consistency of the final chip.

[0045] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A polishing method based on online monitoring and dynamic pressure compensation of edge regions, characterized in that: The chemical mechanical polishing apparatus includes a lower frame (10), an upper frame (1) is provided at the upper end of the lower frame (10), a control platform (8) is provided in the upper frame (1) and placed at the upper end of the lower frame (10), a wafer (2) is provided at the upper end of the control platform (8), a polishing pad (9) is provided between the control platform (8) and the wafer (2), an edge optical monitor (3) is provided at the upper end of the wafer (2) and is electrically connected and fixed to the upper frame (1), and a partitioned controllable pressure polishing head (4) is provided at the lower end of the edge optical monitor (3). The polishing method based on online edge region monitoring and dynamic pressure compensation includes the following steps: Step 1: Place the wafer (2) under the partitioned controllable pressure polishing head (4); Step 2: Make the surface of the wafer (2) contact the polishing pad and supply polishing fluid to start the polishing process; Step 3: During the polishing process, the thin film thickness in the edge region of the wafer (2) is measured in real time and in situ using an edge optical monitoring instrument (3) integrated into the edge of the polishing pad stage (9); Step 4: Transmit the real-time measured film thickness data of the edge area to the control unit (8). Step 5: The control unit (8) compares the real-time film thickness data with the preset ideal removal rate curve. If the removal rate of the edge area is lower than the target value, a control command is generated to dynamically increase the pressure applied to the edge pressure area; otherwise, the pressure is reduced accordingly. Step 6: Repeat steps 3 through 5 until the main polishing endpoint is reached.

2. The polishing method based on online edge region monitoring and dynamic pressure compensation according to claim 1, characterized in that: The polishing pad (9) is surrounded by a machine guard plate (7) that is snapped into the control machine (8). The machine guard plate (7) is made of transparent material.

3. The polishing method based on online edge region monitoring and dynamic pressure compensation according to claim 2, characterized in that: The polishing pad stage (9) is equipped with a spectrometer (6) fixedly connected to the machine base guard plate (7) on its side, and the partitioned controllable pressure polishing head (4) is equipped with a light source lamp (5) on its side.

4. The polishing method based on online edge region monitoring and dynamic pressure compensation according to claim 3, characterized in that: The edge optical monitor (3) is located in the outer 1 / 4 area of ​​the polishing pad stage (9), corresponding to the edge position of the wafer (2) during polishing. The edge optical monitor (3) works in conjunction with the light source lamp (5) and the spectrometer (6) to measure the film thickness on the lower surface of the wafer (2) through which the transparent machine guard plate (7) rotates.

5. The polishing method based on online edge region monitoring and dynamic pressure compensation according to claim 1, characterized in that: The partitioned controllable pressure polishing head (4) consists of a central pressure zone and an edge pressure zone, with the edge pressure zone forming a ring structure surrounding the central pressure zone.

6. The polishing method based on online edge region monitoring and dynamic pressure compensation according to claim 5, characterized in that: The control unit (8) is connected to the edge optical monitor (3) and the partition controllable pressure polishing head (4) by a signal connection. It is configured to receive film thickness data, calculate the pressure adjustment amount based on a preset algorithm, and send pressure control commands to the edge pressure zone.

7. The polishing method based on online edge region monitoring and dynamic pressure compensation according to claim 6, characterized in that: The control algorithm of the control machine (8) is proportional-integral-derivative (PID) control, with the goal of making the measured removal rate of the edge region track the preset ideal rate curve.

Images