Force servo microstructure processing method based on semiconductor polycrystal surface grain boundary judgment

Abstract

The application relates to a force servo microstructure processing method based on semiconductor polycrystal surface grain boundary judgment, and belongs to the technical field of semiconductor surface ultra-precision cutting processing. The method comprises the following steps: building a force servo auxiliary cutting processing device, and configuring a force detection module for the device; scanning a semiconductor polycrystal workpiece in combination with the force servo auxiliary cutting processing device and the force detection module, obtaining a plurality of grain boundary points, fitting a grain boundary position line based on all the grain boundary points; setting different reference cutting forces for different crystal phases according to the grain boundary position line; and adjusting the cutting force to the reference cutting force to perform force servo microstructure processing on the polycrystal surface of the semiconductor polycrystal workpiece. The method can avoid the influence of crystal phase change on the accuracy of the cutting force and cutting depth relationship model, and achieves the purpose of precise processing.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision cutting and machining technology of semiconductor surfaces, and particularly relates to a force servo microstructure machining method based on the determination of grain boundaries on polycrystalline semiconductor surfaces. Background Technology

[0002] Single-point diamond ultra-precision cutting is an important technology for machining microstructured surfaces, widely used in optics, semiconductors, and aerospace. Polycrystalline materials are a class of workpiece materials widely used in ultra-precision cutting. With increasingly higher machining accuracy requirements, the demand for machining nanoscale and precision microstructures is growing. Semiconductor polycrystalline workpiece materials mainly include silicon, germanium, and compound semiconductor polycrystalline materials. Silicon is abundant, has controllable production costs, and stable semiconductor properties, making it a fundamental material for integrated circuits and power devices. Germanium, due to its high electron mobility, is used in some high-frequency and infrared devices. Compound semiconductor polycrystalline materials such as gallium arsenide, indium phosphide, and silicon carbide, with their special properties such as high temperature resistance, high frequency, and high power, are widely used in high-end applications such as radio frequency communication, optoelectronics, and new energy power devices, meeting performance requirements under different operating conditions.

[0003] Traditional machining devices rely on position control, but due to guide rail straightness errors and motion errors, achieving nanometer-level precision is difficult. Force servo machining is an effective method to improve the positional accuracy of machining devices. By controlling the cutting force during the machining process, the tool can automatically track the workpiece surface for microstructure machining, and it has the advantage of automatically compensating for guide rail straightness errors and motion errors. The high-precision realization of microstructures in force servo machining depends on an accurate model of the relationship between cutting force and depth of cut. However, polycrystalline materials have different crystal phases, and changes in crystal phases can affect the accuracy of the cutting force-depth-of-cut model, posing a challenge to high-precision force servo microstructure machining on polycrystalline surfaces. Summary of the Invention

[0004] The purpose of this invention is to provide a force servo microstructure machining method based on the determination of grain boundaries on the surface of semiconductor polycrystalline materials, so as to solve the problem that changes in the crystal phase affect the accuracy of the cutting force and cutting depth relationship model when machining polycrystalline materials with existing servo microstructures.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] This invention relates to a force-servo microstructure fabrication method based on the determination of grain boundaries on a semiconductor polycrystalline surface, comprising the following steps:

[0007] S1. Construct a force servo-assisted cutting machining device and configure it with a force detection module;

[0008] S2. Mount the semiconductor polycrystalline workpiece onto the force servo-assisted cutting processing device, and scan the semiconductor polycrystalline workpiece by combining the force servo-assisted cutting processing device and the force detection module to obtain multiple discrete grain boundary points. Fit the grain boundary position line based on all grain boundary points.

[0009] S3. Based on the grain boundary position lines, different reference cutting forces are set for different crystal phases;

[0010] S4. By using a servo-assisted cutting processing device in conjunction with a force detection module, the cutting force is adjusted to the reference cutting force, and force servo microstructure processing is performed on the polycrystalline surface of the semiconductor polycrystalline workpiece.

[0011] Preferably, the force servo-assisted cutting machining device constructed by S1 includes:

[0012] The Z-axis is used to move the tool along the Z-axis direction and initially feed the tool to the surface of the semiconductor polycrystalline workpiece.

[0013] The X-axis is used to move the tool along the X-axis direction;

[0014] The Y-axis is used to move the semiconductor polycrystalline workpiece along the Y-axis direction;

[0015] The micro-drive module is used to move the tool along the Z-axis, precisely feed the tool to the surface of the semiconductor polycrystalline workpiece, and precisely control the cutting force during scanning and force servo microstructure machining.

[0016] The cutting tool is mounted on the micro-drive module and is used for scanning and force servo microstructure machining.

[0017] The X-axis and Y-axis work together to control the scanning and cutting path.

[0018] Preferably, the force detection module is disposed between the tool and the micro-drive module, and is used to detect the cutting force of the tool during scanning and force servo microstructure machining.

[0019] Preferably, the driving resolution of the micro-driving module is better than 2 nm.

[0020] Preferably, the force detection module has a force detection resolution better than 1 mN.

[0021] Preferably, the specific method by which the S2 combined force servo assisted cutting processing device and force detection module scan the semiconductor polycrystalline workpiece to obtain multiple discrete grain boundary points is as follows: a scanning route is set, the scanning route is a column-by-column scan, during the scanning process, the force detection module controls the cutting force of the tool to be constant, and in each round of scanning, when the tool jumps, the position of the jump is regarded as a grain boundary point.

[0022] Preferably, the column interval during the column-by-column scan in S2 is 100 μm.

[0023] Preferably, during the S2 scanning process, the cutting force of the tool is kept constant and less than 1mN.

[0024] Preferably, S3 sets different reference cutting forces for different crystal phases based on the grain boundary position lines. Specifically, it sets reference cutting forces for different crystal phases according to the required cutting depth of the microstructure and the cutting force-cutting depth model curves of different crystal phases.

[0025] Preferably, the cutting force-depth model curves of different crystal phases in S3 are obtained by fitting the set cutting force with the depth of the groove in a constant-force cutting experiment using a force servo-assisted cutting device.

[0026] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0027] The force servo microstructure machining method based on the determination of grain boundaries on the surface of semiconductor polycrystalline material involved in this invention is to equip a force servo assisted cutting machining device with a force detection module. Before the force servo microstructure machining, the force servo assisted cutting machining device and the force detection module are combined to scan the semiconductor polycrystalline workpiece to obtain multiple grain boundary points. Based on all the grain boundary points, a grain boundary position line is fitted. According to the grain boundary position line, different reference cutting forces are set for different crystal phases to avoid the influence of crystal phase changes on the accuracy of the cutting force and cutting depth relationship model, thereby achieving the purpose of precise machining. Attached Figure Description

[0028] Figure 1 This is a flowchart of a force-servo microstructure fabrication method based on the determination of grain boundaries on a semiconductor polycrystalline surface.

[0029] Figure 2 This is a schematic diagram illustrating the working principle of the force servo-assisted cutting machining device of this method.

[0030] Figure 3 This is a schematic diagram of the grain boundary location lines obtained by constant force scanning.

[0031] Figure 4 A schematic diagram showing the setting of reference cutting force for microstructures with different crystal phases. Detailed Implementation

[0032] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments. The following embodiments are used to illustrate the invention, but are not intended to limit the scope of the invention.

[0033] See attached document Figure 1 As shown, the present invention relates to a force-servo microstructure fabrication method based on the determination of grain boundaries on a semiconductor polycrystalline surface, comprising the following steps:

[0034] S1. Construct a force servo-assisted cutting machining device and configure it with a force detection module:

[0035] See attached document Figure 2 As shown, the force servo-assisted cutting device includes an X-axis 1, a Y-axis 2, a Z-axis 3, a micro-drive module 4, and a cutting tool 6. The X-axis 1 is mounted on the Z-axis 3, the micro-drive module 4 is mounted on the X-axis 1, and the cutting tool 6 is mounted on the side of the micro-drive module 4 in the Z-axis direction close to the Y-axis via a force detection module 5. The movement direction of the micro-drive module 4 is parallel to the Z-axis 3.

[0036] The Y-axis 2 is used to mount the semiconductor polycrystalline workpiece 8 and move it along the Y-axis direction; the Z-axis 3 is used to move the tool 6 along the Z-axis direction, initially feeding the tool 6 to the surface of the semiconductor polycrystalline workpiece 8; the X-axis 1 is used to move the tool 6 along the X-axis direction; the micro-drive module 4 is used to move the tool 6 along the Z-axis direction, precisely feeding the tool 6 to the surface of the semiconductor polycrystalline workpiece and precisely controlling the cutting force during scanning and force servo microstructure machining; the tool 6 is used for scanning and force servo microstructure machining; the X-axis 1 and Y-axis 2 work together to control the cutting path during scanning and force servo microstructure machining. The force detection module 5 is used to detect the cutting force of the tool 6 during scanning and force servo microstructure machining.

[0037] The driving resolution of the micro-driving module 4 is required to be better than 2 nm; the force detection resolution of the force detection module 5 is required to be better than 1 mN.

[0038] S2. See Appendix Figure 2 and Figure 3 As shown, the semiconductor polycrystalline workpiece 8 is mounted on the Y-axis 2 of the force servo-assisted cutting machining device. The device and force detection module scan the workpiece, setting a scanning path. The scanning path is column-by-column, with each column spaced 100 μm apart. Excessive spacing will result in large distances between adjacent grain boundary points, leading to significant errors in the final fitted grain boundary position lines. During the scanning process, the force detection module 5 controls the cutting force of the tool 6 to remain constant and below 1 mN. Under this contact force, the surface scratch depth is less than 5 nm, which can be measured using a white light interferometer or an atomic force microscope.

[0039] During each scan cycle, the current coordinates (x, y) of the cutting device are read in real time and mapped one-to-one with the micro-drive position signal. When the tool changes direction, i.e., the position signal obtained by the position signal sensor changes direction, the position of the change is regarded as a grain boundary point. After obtaining multiple discrete grain boundary points, a grain boundary position line is fitted based on all grain boundary points. The fitting process is common knowledge in the art and is not protected by this invention.

[0040] Because the diamond tool tip has a circular arc feature, the spatial trajectory of the tool scanning the workpiece surface does not perfectly coincide with the workpiece surface shape. The smaller the tool arc, the higher the degree of coincidence between the tool spatial trajectory and the workpiece surface shape. To improve the accuracy of scanning and measuring grain boundary positions, the tool tip arc is compensated. Two adjacent measurement points are randomly selected, and the distance between the measurement points is taken as 10 nanometers. The trajectory between the measurement points can be regarded as a straight line. Let the tool position coordinates of the two measurement points be ( y t1 , z t1 )and( y t2 , z t2 The radius of the tool tip arc is... r The slope angle is θ Then the Z-axis position of the workpiece surface between these two measurement points z w1 It can be calculated as follows:

[0041] θ = arctan[( z t2 - z t1 ) / ( y t2 - y t1 )],

[0042] y w1 = 0.5 ( y t1 + y t2 ) + r· sin θ ,

[0043] z w1 = 0.5 ( z t1 + z t2 ) - r· cos θ ,

[0044] To avoid Z-axis jump y w1 Uneven change, therefore y w1 It can be calculated as y w1 =0.5 ( y t1 + y t2Thus, a corresponding workpiece surface point position can be calculated for every two adjacent tool scanning point positions, and connecting all workpiece surface point positions is considered as the scanning tool tip point position.

[0045] S3. Based on the grain boundary line and the required cutting depth for the microstructure, and according to the cutting force-cut depth model curves for different crystal phases, different reference cutting forces are set for different crystal phases. F (x,y) As attached Figure 4 As shown, microstructures of the same depth need to be machined on both crystal phase 1 and crystal phase 2. However, the cutting force required on crystal phase 1 is less than that required on crystal phase 2. Therefore, based on the grain boundary position lines obtained in S2, the position of the crystal phases can be accurately determined, and a precisely matched reference cutting force can be planned. F (x,y) .

[0046] The cutting force-depth model curves for different crystal phases need to be obtained through pre-calibrated cutting experiments before microstructure machining. To maximize time savings, the pre-calibrated cutting experiments can be performed on the current sample. After steps S1 and S2, a series of constant-force cutting depth groove machining experiments are performed on different crystal phases using a force servo-assisted cutting machining device. Then, the workpiece is removed and the groove depth is measured using a white light interferometer. Finally, the cutting force and groove depth are correlated one-to-one to establish the cutting force-depth model curves. For ease of understanding, this invention conducted pre-calibrated cutting experiments on silicon surfaces along the

[100] and

[110] crystal phases: constant cutting forces of 12, 24, 36, 48, 60, 72, and 84 mN were set, resulting in average cutting depths of 22.1, 42.3, 57.2, 71.5, 83.4, 94.0, and 104.1 nm along the

[110] direction; and average cutting depths of 26.5, 50.8, 68.6, 85.8, 112.8, and 124.9 nm along the

[100] direction. First, a polynomial fitting was performed on the cutting force-cutting depth model along the

[110] direction. The standard deviations after fitting the first, second, and third order polynomials were 3.1 nm, 0.7 nm, and 0.3 nm, respectively. The second order polynomial with the first standard deviation less than 1 nm was selected as:

[0047] ,

[0048] Similarly, polynomial fitting was performed on the cutting force-depth model along the

[100] direction. The standard deviations of the first, second, and third order polynomials were 3.8 nm, 0.8 nm, and 0.4 nm, respectively. The second order polynomial with the first standard deviation less than 1 nm was selected as:

[0049] ,

[0050] Suppose that the crystal phases are located at

[110] and

[100] ( x, y The required cutting depths at each point are respectively rDep Si-110-(x,y) and rDep Si-100-(x,y) The reference cutting force is:

[0051] F

[110] -(x,y) =f 1 -1 (rDep Si-110-(x,y) ),

[0052] F

[100] -(x,y) =f 2 -1 (rDep Si-100-(x,y) ).

[0053] S4. See Appendix Figure 2 As shown, the cutting force is adjusted to the reference cutting force by the servo-assisted cutting machining device in conjunction with the force detection module. That is, during the force servo microstructure machining process, the force detection module 5 performs online force detection and sends the detection data to the controller 7 of the servo-assisted cutting machining device. The controller 7 compares the online detection data with the input current machining coordinates. x , y Reference cutting force F (x,y) When the online detection value is less than the reference cutting force, the controller 7 drives the micro-drive module 4 to feed the tool closer to the semiconductor polycrystalline workpiece 8 to increase the cutting force; conversely, when the online detection value is greater than the reference cutting force, the controller 7 drives the micro-drive module 4 to feed the tool away from the semiconductor polycrystalline workpiece 8 to reduce the cutting force. After the cutting force is adjusted to the reference cutting force, the linkage between the Y-axis 2 and the X-axis 1 ensures that the movement trajectory of the tool 6 relative to the semiconductor polycrystalline workpiece 8 conforms to the designed cutting trajectory, thereby performing force servo microstructure machining on the polycrystalline surfaces of the semiconductor polycrystalline workpiece.

[0054] The present invention has been described in detail above with reference to the embodiments, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A force-servo microstructure fabrication method based on grain boundary judgment of semiconductor polycrystalline surfaces, characterized in that, It includes the following steps: S1. Construct a force servo-assisted cutting machining device and configure it with a force detection module; S2. Mount the semiconductor polycrystalline workpiece onto the force servo-assisted cutting processing device, and scan the semiconductor polycrystalline workpiece by combining the force servo-assisted cutting processing device and the force detection module to obtain multiple discrete grain boundary points. Fit the grain boundary position line based on all grain boundary points. S3. Based on the grain boundary position lines, different reference cutting forces are set for different crystal phases; S4. By using a servo-assisted cutting processing device in conjunction with a force detection module, the cutting force is adjusted to the reference cutting force, and force servo microstructure processing is performed on the polycrystalline surface of the semiconductor polycrystalline workpiece.

2. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 1, characterized in that: The force servo-assisted cutting device constructed by S1 includes: The Z-axis is used to move the tool along the Z-axis direction and initially feed the tool to the surface of the semiconductor polycrystalline workpiece. The X-axis is used to move the tool along the X-axis direction; The Y-axis is used to move the semiconductor polycrystalline workpiece along the Y-axis direction; The micro-drive module is used to move the tool along the Z-axis, precisely feed the tool to the surface of the semiconductor polycrystalline workpiece, and precisely control the cutting force during scanning and force servo microstructure machining. The cutting tool is mounted on the micro-drive module and is used for scanning and force servo microstructure machining. The X-axis and Y-axis work together to control the scanning and cutting path.

3. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 2, characterized in that: The force detection module is located between the tool and the micro-drive module and is used to detect the cutting force of the tool during scanning and force servo microstructure machining.

4. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 3, characterized in that: The driving resolution of the micro-driving module is better than 2 nm.

5. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 3, characterized in that: The force detection module described above has a force detection resolution better than 1 mN.

6. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 1, characterized in that: The specific method by which the S2 combined force servo assisted cutting processing device and force detection module scan semiconductor polycrystalline workpieces to obtain multiple discrete grain boundary points is as follows: a scanning route is set, the scanning route is a column-by-column scan, during the scanning process, the force detection module controls the cutting force of the tool to be constant, and in each round of scanning, when the tool jumps, the position of the jump is regarded as a grain boundary point.

7. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 6, characterized in that: In S2, the interval between each column during the column-by-column scan is 100 μm.

8. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 6, characterized in that: During the S2 scanning process, the cutting force of the tool is kept constant and below 1mN.

9. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 1, characterized in that: S3 sets different reference cutting forces for different crystal phases based on the grain boundary position lines. Specifically, it sets reference cutting forces for different crystal phases according to the required cutting depth of the microstructure and the cutting force-cutting depth model curves of different crystal phases.

10. The force-servo microstructure fabrication method based on semiconductor polycrystalline surface grain boundary judgment according to claim 9, characterized in that: The cutting force-depth model curves of different crystal phases in S3 were obtained by fitting the set cutting force with the depth of the groove in a constant-force cutting experiment using a force servo-assisted cutting device.

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