A method for electrospark machining of P-type single crystal silicon workpiece

Abstract

The invention discloses an electrospark machining method for a P-type monocrystalline silicon workpiece, relates to the technical field of electrospark machining, and comprises the following steps: S1, connecting the positive electrode of a pulse power supply to the P-type monocrystalline silicon workpiece, and connecting the negative electrode to a tool electrode; S2, using an electrospark machining fluid containing N-type monocrystalline silicon powder to completely immerse the P-type monocrystalline silicon workpiece; S3, turning on the pulse power supply to perform positive polarity machining; S4, after the positive polarity machining is completed, turning off the pulse power supply, completely discharging the electrospark machining fluid containing N-type monocrystalline silicon powder, and then using an electrospark machining fluid without N-type monocrystalline silicon powder to completely immerse the P-type monocrystalline silicon workpiece; S5, connecting the negative electrode of the pulse power supply to a recast layer formed on the surface of the P-type monocrystalline silicon workpiece, and connecting the positive electrode to the tool electrode; S6, turning on the pulse power supply to perform negative polarity machining; S7, after the recast layer is completely removed, turning off the pulse power supply. The recast layer on the surface of the workpiece can be effectively removed.

Description

Technical Field

[0001] The invention relates to the technical field of electric spark machining, and in particular to an electric spark machining method for a P-type single crystal silicon workpiece. Background Art

[0002] Electrospark machining refers to a method of machining a workpiece by electro-erosion through pulse discharge between the tool electrode and the workpiece electrode in a certain medium. Its basic principle is to use pulse current to produce continuous discharge between the tool electrode and the workpiece. Each short and intense spark discharge will instantly melt and vaporize a very small part of the material on the workpiece surface, thereby achieving material removal.

[0003] In the field of EDM technology, there are unique challenges and limitations, especially when processing semiconductor materials such as P-type monocrystalline silicon. As an important semiconductor material, P-type monocrystalline silicon is widely used in integrated circuits, microelectronic devices, photovoltaics and other fields, and its processing quality directly affects the performance and reliability of these products. However, the electrical properties of P-type monocrystalline silicon determine that it only exhibits good conductivity when connected to the positive pole of the power supply, which greatly limits the process flexibility and efficiency of EDM, especially when trying to remove the recast layer formed after processing, traditional methods are difficult to deal with effectively.

[0004] The recast layer is an inevitable byproduct of the EDM process. It is formed by the rapid cooling and solidification of the molten material on the workpiece surface, affecting the surface quality and subsequent finishing operations. P-type single crystal silicon workpieces refer to the parts to be processed made of P-type single crystal silicon materials. For P-type single crystal silicon workpieces, since the recast layer cannot be effectively removed simply by changing the polarity, finding innovative solutions has become the key to improving processing quality and efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide an electrospark machining method for a P-type single crystal silicon workpiece, so as to solve the problems existing in the above-mentioned prior art and effectively remove the recast layer formed on the P-type single crystal silicon during the electrospark machining process.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides an electrospark machining method for a P-type single crystal silicon workpiece, comprising the following steps:

[0008] S1. Fix a P-type single crystal silicon workpiece on an electric spark machining machine, and install a tool electrode on a spindle of the machine through a fixture; connect the positive electrode of a pulse power supply to the P-type single crystal silicon workpiece, and connect the negative electrode of the pulse power supply to the tool electrode;

[0009] S2, adding N-type single crystal silicon powder to the electrospark machining fluid and stirring evenly to obtain an electrospark machining fluid containing N-type single crystal silicon powder; using the electrospark machining fluid containing N-type single crystal silicon powder to completely immerse the P-type single crystal silicon workpiece;

[0010] S3, turning on the pulse power supply to perform positive polarity processing;

[0011] S4, after the positive polarity machining is completed, the pulse power supply is turned off, the electrospark machining fluid containing the N-type single crystal silicon powder is completely discharged, and then the P-type single crystal silicon workpiece is completely immersed in the electrospark machining fluid without the N-type single crystal silicon powder;

[0012] S5, disconnecting the negative electrode of the pulse power supply from the tool electrode, and disconnecting the positive electrode of the pulse power supply from the P-type single crystal silicon workpiece; connecting the negative electrode of the pulse power supply to the recast layer formed on the surface of the P-type single crystal silicon workpiece, and connecting the positive electrode of the pulse power supply to the tool electrode;

[0013] S6, turning on the pulse power supply to perform negative polarity processing;

[0014] S7, after the recast layer is completely removed, the pulse power supply is turned off.

[0015] Preferably, in the electrospark machining fluid containing N-type single crystal silicon powder, the weight ratio of N-type single crystal silicon powder to the electrospark machining fluid is 1:10.

[0016] Preferably, in step S3, the N-type single crystal silicon powder in the electrospark machining fluid containing N-type single crystal silicon powder will gradually deposit on the surface of the P-type single crystal silicon workpiece, so that the recast layer formed on the surface of the P-type single crystal silicon workpiece contains N-type single crystal silicon powder.

[0017] Preferably, during the negative polarity processing, the recast layer on the surface of the P-type single crystal silicon workpiece is gradually removed.

[0018] Compared with the prior art, the present invention has achieved the following technical effects:

[0019] The electrospark machining method for P-type single crystal silicon workpieces of the present invention successfully overcomes the difficulty of removing the recast layer in the electrospark machining of P-type single crystal silicon, and significantly improves the machining quality and efficiency. Through a carefully designed two-stage machining strategy (i.e., a positive polarity machining stage and a negative polarity machining stage), the cavity is efficiently and accurately made on the P-type single crystal silicon workpiece, and the recast layer formed during the machining process is effectively removed.

[0020] Specific:

[0021] First, the present invention uses an electrospark machining fluid containing N-type single crystal silicon powder to immerse a P-type single crystal silicon workpiece in positive polarity electrospark machining, and machines a required cavity on the surface of the P-type single crystal silicon. In this process, the N-type single crystal silicon powder is deposited on the surface of the workpiece due to the action of the electrospark, forming a recast layer containing N-type single crystal silicon, which plays a key role in subsequent processing.

[0022] Subsequently, the conductive properties of N-type single crystal silicon are cleverly utilized through the conversion of reverse polarity EDM. When the workpiece surface (covered with a recast layer containing N-type single crystal silicon) is connected to the negative electrode, the recast layer becomes the main body of the EDM discharge and can be accurately removed without damaging the P-type single crystal silicon substrate underneath. This step not only removes the uneven recast layer, but also significantly improves the surface finish of the workpiece and reduces the surface roughness, achieving a processing quality that is difficult to achieve with traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of positive polarity machining in the electrospark machining method for a P-type single crystal silicon workpiece according to the present invention;

[0025] Figure 2 It is a schematic diagram of forming a recast layer on a P-type single crystal silicon workpiece in the electric spark machining method for a P-type single crystal silicon workpiece according to the present invention;

[0026] Figure 3 It is a schematic diagram of negative polarity machining in the electrospark machining method for a P-type single crystal silicon workpiece according to the present invention;

[0027] Figure 4 It is a schematic diagram of the electrospark machining method for a P-type single crystal silicon workpiece according to the present invention after all the recast layers on the P-type single crystal silicon workpiece are removed;

[0028] Among them, 1. pulse power supply; 2. machine tool spindle; 3. tool electrode; 4. P-type single crystal silicon workpiece; 5. EDM fluid; 6. N-type single crystal silicon powder; 7. recast layer. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide an electrospark machining method for a P-type single crystal silicon workpiece, so as to solve the problems existing in the above-mentioned prior art and effectively remove the recast layer formed on the P-type single crystal silicon during the electrospark machining process.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figures 1 to 4 As shown, this embodiment provides an electrospark machining method for a P-type single crystal silicon workpiece 4, comprising the following steps:

[0033] S1, fix the P-type single crystal silicon workpiece 4 on the electric spark machining machine, and install the tool electrode 3 on the machine tool spindle 2 through a fixture; connect the positive electrode of the pulse power supply 1 to the P-type single crystal silicon workpiece 4, and connect the negative electrode of the pulse power supply 1 to the tool electrode 3;

[0034] S2, adding N-type single crystal silicon powder 6 to the electrospark machining fluid 5 and stirring evenly to obtain the electrospark machining fluid 5 containing the N-type single crystal silicon powder 6; using the electrospark machining fluid 5 containing the N-type single crystal silicon powder 6 to completely immerse the P-type single crystal silicon workpiece 4;

[0035] S3, turn on the pulse power supply 1, perform positive polarity processing, and process the required cavity on the surface of the P-type single crystal silicon;

[0036] The N-type single crystal silicon powder 6 in the EDM fluid 5 containing the N-type single crystal silicon powder 6 will gradually deposit on the surface of the P-type single crystal silicon workpiece 4, so that the recast layer 7 formed on the surface of the P-type single crystal silicon workpiece 4 contains the N-type single crystal silicon powder 6;

[0037] S4, after the positive polarity machining is completed, the pulse power supply 1 is turned off, the electrospark machining fluid 5 containing the N-type single crystal silicon powder 6 is completely discharged, and then the P-type single crystal silicon workpiece 4 is completely immersed in the electrospark machining fluid 5 without the N-type single crystal silicon powder 6;

[0038] S5, disconnecting the negative electrode of the pulse power supply 1 from the tool electrode 3, and disconnecting the positive electrode of the pulse power supply 1 from the P-type single crystal silicon workpiece 4; connecting the negative electrode of the pulse power supply 1 to the recast layer 7 formed on the surface of the P-type single crystal silicon workpiece 4, and connecting the positive electrode of the pulse power supply 1 to the tool electrode 3;

[0039] S6, turning on the pulse power supply 1 to perform negative polarity processing; during the negative polarity processing, the recast layer 7 on the surface of the P-type single crystal silicon workpiece 4 is gradually removed;

[0040] S7, after all the recast layer 7 is removed, the pulse power supply 1 is turned off.

[0041] In the optional scheme of this embodiment, it is more preferred that the weight ratio of the N-type single crystal silicon powder 6 to the electrospark machining fluid 5 in the electrospark machining fluid 5 containing the N-type single crystal silicon powder 6 is 1:10.

[0042] In this embodiment, an electrospark machining fluid 5 containing N-type single crystal silicon powder 6 is used to immerse a P-type single crystal silicon workpiece 4 in positive polarity electrospark machining, and a required cavity is machined on the surface of the P-type single crystal silicon. In this process, the N-type single crystal silicon powder 6 is deposited on the surface of the workpiece due to the action of the electrospark, forming a recast layer 7 containing N-type single crystal silicon, and this recast layer 7 plays a key role in subsequent processing.

[0043] Subsequently, the conductive properties of N-type single crystal silicon are cleverly utilized through the conversion of reverse polarity EDM. When the workpiece surface (covered with the recast layer 7 containing N-type single crystal silicon) is connected to the negative electrode, the recast layer 7 becomes the main body of the EDM discharge and can be accurately removed without damaging the P-type single crystal silicon substrate underneath. This step not only removes the uneven recast layer 7, but also significantly improves the surface finish of the workpiece and reduces the surface roughness, achieving a processing quality that is difficult to achieve with traditional methods;

[0044] During the negative polarity machining process, the electrospark machining fluid 5 that does not contain N-type single crystal silicon powder 6 is immersed in the P-type single crystal silicon workpiece 4 , thereby preventing the N-type single crystal silicon powder 6 from being deposited on the surface of the tool electrode 3 .

[0045] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An electrospark machining method for a P-type single crystal silicon workpiece, characterized in that: The following steps are involved: S1. Fix a P-type single crystal silicon workpiece on an electric spark machining machine, and install a tool electrode on a spindle of the machine through a fixture; connect the positive electrode of a pulse power supply to the P-type single crystal silicon workpiece, and connect the negative electrode of the pulse power supply to the tool electrode; S2, adding N-type single crystal silicon powder to the electrospark machining fluid and stirring evenly to obtain an electrospark machining fluid containing N-type single crystal silicon powder; using the electrospark machining fluid containing N-type single crystal silicon powder to completely immerse the P-type single crystal silicon workpiece; S3, turning on the pulse power supply to perform positive polarity processing; S4, after the positive polarity machining is completed, the pulse power supply is turned off, the electrospark machining fluid containing the N-type single crystal silicon powder is completely discharged, and then the P-type single crystal silicon workpiece is completely immersed in the electrospark machining fluid without the N-type single crystal silicon powder; S5, disconnecting the negative electrode of the pulse power supply from the tool electrode, and disconnecting the positive electrode of the pulse power supply from the P-type single crystal silicon workpiece; connecting the negative electrode of the pulse power supply to the recast layer formed on the surface of the P-type single crystal silicon workpiece, and connecting the positive electrode of the pulse power supply to the tool electrode; S6, turning on the pulse power supply to perform negative polarity processing; S7, after the recast layer is completely removed, the pulse power supply is turned off.

2. The electrospark machining method for a P-type single crystal silicon workpiece according to claim 1, characterized in that: The weight ratio of the N-type single crystal silicon powder to the electrospark machining fluid in the electrospark machining fluid containing the N-type single crystal silicon powder is 1:

10.

3. The electrospark machining method for a P-type single crystal silicon workpiece according to claim 1, characterized in that: In step S3, the N-type single crystal silicon powder in the EDM fluid containing N-type single crystal silicon powder will gradually deposit on the surface of the P-type single crystal silicon workpiece, so that the recast layer formed on the surface of the P-type single crystal silicon workpiece contains N-type single crystal silicon powder.

4. The electrospark machining method for a P-type single crystal silicon workpiece according to claim 1, characterized in that: During the negative polarity processing, the recast layer on the surface of the P-type single crystal silicon workpiece is gradually removed.

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