Chemical mechanical polishing abrasive particle trajectory optimization method

Abstract

The application discloses a chemical mechanical polishing abrasive particle trajectory optimization method, relates to the technical field of chemical mechanical polishing, and solves the problem of performance reduction of optical elements caused by regular abrasive particle trajectories in the prior art. The method is characterized in that: a trajectory model of abrasive particles is constructed, simulation research is carried out by adopting a large proportional speed ratio of 1:2 of the element / spindle speed ratio, the trajectory of the abrasive particles under different spindle swing speeds is simulated, and the process parameters with the minimum regularity coefficient are selected as indexes by taking the trajectory regularity coefficient (represented by calculating the parallel degree proportion of the trajectory tangent) as an index. Experiments show that when the swing speed is 3 mm / s, the regularity degree of the abrasive particle trajectory is the lowest and the abrasive particle trajectory is uniformly distributed, and the risk of local thermal accumulation damage of the element under strong laser conditions can be reduced. The method realizes accurate optimization of the abrasive particle trajectory and improves the machining quality of medium and large caliber optical elements.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing technology, and more specifically to a method for optimizing the trajectory of abrasive particles in chemical mechanical polishing. Background Technology

[0002] Large-scale high-power laser devices for inertial confinement fusion require a large number of medium-to-large aperture planar optical components. When these components are irradiated by nanosecond pulse megajoule-level lasers, if there are regular polishing grain trajectories on their surfaces, they will induce phase nonlinear growth and near-field modulation, leading to local heat accumulation and damage.

[0003] Existing chemical mechanical polishing technology disrupts the abrasive grain trajectory by oscillating the spindle relative to the component, but there is insufficient research on the correlation between oscillation parameters and the degree of trajectory regularity, and there is a lack of quantitative trajectory characterization methods, making it difficult to achieve precise trajectory optimization. Summary of the Invention

[0004] To address the problem of reduced optical component performance caused by regular abrasive grain trajectories in existing technologies, this invention provides a method for optimizing abrasive grain trajectories in chemical mechanical polishing. By defining a characterization method for the degree of trajectory regularity, and conducting simulation studies using a large ratio of rotational speeds, the spindle oscillation speed parameters are optimized to reduce the degree of regularity in the abrasive grain trajectory.

[0005] A method for optimizing abrasive particle trajectories in chemical mechanical polishing, which is implemented through the following steps:

[0006] Step 1: Construct a chemical mechanical polishing abrasive trajectory model;

[0007] Step 2: Based on the abrasive trajectory model constructed in Step 1, a large ratio of rotational speed is used for simulation. Based on the preset process parameters, the abrasive trajectory under the spindle oscillation speed is simulated to obtain the trajectory regularity coefficients corresponding to each oscillation speed.

[0008] Step 3: Compare the trajectory regularity coefficients obtained in Step 2, and select the oscillation speed with the smallest regularity coefficient as the optimal process parameter;

[0009] Step 4: Perform chemical mechanical polishing on the workpiece based on the optimal process parameters determined in Step 3 to optimize the abrasive grain trajectory.

[0010] The beneficial effects of this invention are:

[0011] I. The trajectory optimization method described in this invention introduces a trajectory regularity coefficient as a quantitative indicator. By calculating the parallelism ratio of trajectory tangents, the degree of trajectory regularity is accurately characterized, thus avoiding subjective judgment errors.

[0012] Second, the trajectory optimization method described in this invention uses a large ratio of 1:2 for component / spindle speed to conduct simulation studies, which eliminates the interference of speed ratio on the degree of trajectory regularity and ensures the reliability of the research results.

[0013] Third, the trajectory optimization method described in this invention specifically optimizes the spindle oscillation speed parameters, significantly reduces the regularity of the abrasive grain trajectory, reduces the risk of component damage under strong laser conditions, and improves processing quality. Attached Figure Description

[0014] Figure 1 This is a flowchart of the chemical mechanical polishing abrasive trajectory optimization method described in this invention;

[0015] Figure 2 For the surface profile information of the workpiece to be measured;

[0016] Figure 3 This is a two-dimensional information diagram of the surface shape of the workpiece to be measured;

[0017] Figure 4 This is a schematic diagram of the motion principle of a polishing machine.

[0018] Figure 5 A schematic diagram of the motion trajectory of a point on a component;

[0019] Figure 6 Simulation results of abrasive particle trajectory model;

[0020] Figure 7 The images show the abrasive grain trajectory at various processing speeds; among them, (a), (b), (c), (d), (e), and (f) are simulation results when the oscillation speed is set to 0.5 mm / s, 1 mm / s, 1.5 mm / s, 2 mm / s, 2.5 mm / s, and 3 mm / s, respectively.

[0021] Figure 8 This is a schematic diagram showing the relationship between the regularity coefficient and the oscillation velocity; where (a) represents the radius P at different oscillation velocities. i (b) is the standard deviation of the P value and the P value for each radius at different swing velocities.

[0022] Figure 9 This is a diagram showing the actual processing effect after process optimization. Detailed Implementation

[0023] Specific Implementation Method 1: Combination Figures 1 to 9 This embodiment describes a method for optimizing the abrasive trajectory in chemical mechanical polishing, which is implemented through the following steps:

[0024] Step 1: Construct abrasive particle trajectory model;

[0025] The processing principle of a chemical mechanical polishing (CMP) machine is analyzed. The machine consists of a frame, a spindle, and a component disk (sub-diameter polishing equipment). The component disk drives the component to rotate, while the spindle simultaneously rotates and oscillates along a swing beam (spindle oscillation speed v1, spindle speed ω2, component speed ω1, spindle oscillation range, and processing time; the spindle and component rotate in the same direction). The abrasive grain trajectory is considered as the motion trajectory of a point on the spindle tool relative to the component. A mathematical model is constructed based on the machine's motion parameters (oscillation speed, speed, oscillation range, etc.), and the trajectory is generated by calculating the real-time position of the abrasive grain in the component coordinate system.

[0026] Step 2: Simulate the trajectory of abrasive particles with different oscillation speeds;

[0027] A large speed ratio of 1:2 for the component / spindle speed ratio is used for simulation to avoid interference from the speed ratio on the regularity of the trajectory.

[0028] The preset process parameters are: component size 430×430mm, component speed 5rad / min, spindle speed 10rad / min, processing time 2h, oscillation range 0~20mm, and simulation time interval 0.1s.

[0029] like Figure 7 As shown, oscillation speeds of 0.5 mm / s, 1 mm / s, 1.5 mm / s, 2 mm / s, 2.5 mm / s, and 3 mm / s were set to simulate abrasive grain trajectories and calculate the regularity coefficients. The results show that the regularity coefficient is the smallest (0.077) at 3 mm / s, and the trajectory is evenly distributed on the component surface.

[0030] Step 3: Determine the optimal process parameters;

[0031] Based on the results of steps two and three, a swing speed of 3 mm / s with uniform swing speed is selected as the optimal process parameter.

[0032] Step 4: Implement the processing;

[0033] Chemical mechanical polishing of components is performed based on optimal process parameters to optimize abrasive grain trajectory.

[0034] Specific Implementation Method Two: Combination Figures 1 to 9 This embodiment describes an example of the chemical mechanical polishing abrasive trajectory optimization method described in Specific Embodiment 1. The method is implemented through the following steps:

[0035] Step 1: Detect the surface information of the component under test and convert it into actual two-dimensional feature representation.

[0036] In this embodiment, the surface shape of the component under test is regarded as extending from the center of the component to the periphery and consisting of a series of average surface heights. The features are represented in a two-dimensional coordinate system; the x-axis is the distance from the center of the component, and the y-axis is the vertical height feature. After representing the surface height from the center to the periphery in the above method, a complete two-dimensional surface feature representation can be obtained, and the feature reflected is the current surface feature.

[0037] like Figure 2 and Figure 3 As shown, the surface profile information obtained by detecting the component under test includes: the average height difference (PV value) and the component size; the heat map generated from the above surface profile information is shown in the figure. Figure 2 As shown, it is converted into an actual two-dimensional surface feature representation, such as Figure 3 As shown.

[0038] Step Two, Equipment Selection: Select chemical mechanical polishing equipment (full-diameter machining equipment), including a spindle oscillation mechanism, a self-rotation drive mechanism, and component fixing devices. A polyurethane polishing pad is adhered to the spindle surface. Figure 4 As shown, a polishing slurry containing cerium oxide abrasive is used. In the figure, the spindle oscillation speed v1, spindle speed ω2, and component speed ω1 all rotate in the same direction.

[0039] Step 3: Constructing the abrasive trajectory model (constructing the abrasive trajectory model for full-diameter machining equipment): Calculate the real-time position of the abrasive particles, such as... Figure 5 As shown, the square represents the position of the square component. The origin of the x and y axes is located at the center O1 of the component. The main spindle swing axis passes through the origin O1, and its initial position coincides with the x-axis. The two main spindle swing limit points A and B are located on the main spindle swing axis. The initial position of the abrasive grain is located at P1 on the x-axis, and the initial position of the main spindle is located at O1. After a period of motion, the main spindle swing axis rotates around the center origin O1 by an angle θ1, and the main spindle swings to point O2 on the main spindle swing axis. After rotating by an angle θ2, the abrasive grain moves to point P2. The trajectory of the abrasive grain is fitted by P1 and P2, as shown below. Figure 6 As shown.

[0040] Step 4: Simulation Experiment and Data Processing: Simulate the abrasive grain trajectory at different oscillation speeds under high rotational speed ratios, such as... Figure 7 As shown in the figure, (a), (b), (c), (d), (e), and (f) are simulation results with oscillation speeds of 0.5 mm / s, 1 mm / s, 1.5 mm / s, 2 mm / s, 2.5 mm / s, and 3 mm / s, respectively. The results show that the regularity coefficient is the smallest (0.077) at 3 mm / s, and the trajectory is evenly distributed on the component surface. The regularity of the abrasive trajectory is calculated and the data is organized, as follows: Figure 8 As shown in the figure, (a) represents the radius P at different oscillation velocities. i(b) is the standard deviation of the P value and the P value of each radius under different swing speeds; Calculation of regularity coefficient: Select 6 evenly distributed radii (P1, P2, P3, P4, P5, P6) on the surface of the component, calculate the proportion of the tangent angle of the trajectory on each radius that is close to 0° or 180°, and take the average value as the regularity coefficient.

[0041] The process parameters were optimized by selecting the oscillation speed with the lowest degree of abrasive grain trajectory regularity. When the oscillation speed was 3 mm / s and the oscillation was uniform, the trajectory regularity coefficient was minimized, the trajectory distribution on the component surface was uniform, and the requirements for use under extreme working conditions were met. The specific process is as follows:

[0042] First, select six evenly distributed radii on the surface of the component. Draw a straight line from the center of the ring of each radius. This straight line intersects the abrasive grain trajectory to form a series of intersection points. Calculate the parallelism of the trajectory tangents at all intersection points.

[0043] Secondly, for any two tangents, the included angle α mn Statistical analysis is performed on (m,n=1,2,…,k,m≠n), where k is the number of intersection points between the straight line and the abrasive grain trajectory. Let χ(a mn ) is the indicator function, expressed as χ(a mn )=1 when |a mn |≤ε or|a mn -180°|≤ε, otherwise χ(a) mn ) = 0, where ε is a very small positive number (0.02°) that measures how close the angle is to 0 degrees or 180°;

[0044] Finally, the regularity coefficient P for each radius i =(1 / k(k-1))×Σχ(a mn The trajectory regularity coefficient P is the average of the six radius regularity coefficients; the closer the regularity coefficient P is to 1, the more regular the trajectory; the closer P is to 0, the lower the degree of trajectory regularity.

[0045] Step 5: Actual processing;

[0046] Set the parameters as follows: component size 430×430×10mm, component speed 10.1rad / min, spindle speed 10rad / min (speed ratio 1:1), oscillation speed 3mm / s, machining time 2h, oscillation range 0~20mm. Perform actual machining and output the optimized machining results, such as... Figure 9 As shown, the regularity of the processing results is reduced.

[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for optimizing abrasive particle trajectories in chemical mechanical polishing, characterized by: The method includes the following steps: Step 1: Construct a chemical mechanical polishing abrasive trajectory model; Step 2: Based on the abrasive trajectory model constructed in Step 1, a large ratio of rotational speed is used for simulation. Based on the preset process parameters, the abrasive trajectory under the spindle oscillation speed is simulated to obtain the trajectory regularity coefficients corresponding to each oscillation speed. Step 3: Compare the trajectory regularity coefficients obtained in Step 2, and select the oscillation speed with the smallest regularity coefficient as the optimal process parameter; The trajectory regularity coefficient is represented by a method for characterizing the degree of trajectory regularity: Step 3: Select six evenly distributed radii on the surface of the component. Draw a straight line from the center of the ring of each radius. This straight line intersects the abrasive grain trajectory to form a series of intersection points. Calculate the parallelism of the trajectory tangents at all intersection points. Step 3.2: The angle between any two tangents Statistical analysis was conducted to determine the regularity coefficient of each radius. ,in, It is an indicator function; The number of intersection points when the straight line intersects the abrasive grain trajectory; trajectory regularity coefficient. The average of the six radius regularity coefficients; regularity coefficients The closer it is to 1, the more regular the trajectory; The closer to 0, the lower the regularity of the trajectory; Step 4: Perform chemical mechanical polishing on the workpiece based on the optimal process parameters determined in Step 3 to optimize the abrasive grain trajectory.

2. The method for optimizing abrasive particle trajectories in chemical mechanical polishing according to claim 1, characterized in that: In step one, the motion parameters of the abrasive trajectory model include the spindle oscillation speed. Spindle speed Component rotation speed The spindle swing range and processing time, wherein the spindle and the component rotate in the same direction.

3. The method for optimizing abrasive particle trajectories in chemical mechanical polishing according to claim 1, characterized in that: In step two, the simulated range of the swing speed is 0.5 mm / s to 3 mm / s, and at least six different speed values ​​are set at intervals of 0.5 mm / s.

4. The method for optimizing abrasive particle trajectories in chemical mechanical polishing according to claim 1, characterized in that: In step three, the criteria for determining the optimal process parameters are: the trajectory regularity coefficient is the smallest, and the abrasive grain trajectory is evenly distributed on the surface of the component.

5. The method for optimizing abrasive particle trajectories in chemical mechanical polishing according to claim 1, characterized in that: The optimal process parameter is selected as the optimal oscillation speed of 3 mm / s.

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