CN115716237A - A device and method for polishing a silicon wafer - Google Patents

Abstract

The embodiment of the present invention discloses a device and method for polishing a silicon wafer, the device includes: a rotary driver, the rotary driver is used to rotate the polishing head around its own central axis relative to the silicon wafer to Polishing the portion of the silicon wafer that is in contact with the polishing head; a translational drive, the translational drive is used to make the polishing head relative to the silicon wafer in a plane parallel to the neutral surface of the silicon wafer wafer translation to polish the entire major surface of the silicon wafer; a sensor for sensing the pressure exerted by the polishing head on the silicon wafer, wherein the pressure is due to the The main surface is uneven; the governor is used to reduce the translation speed of the polishing head when the pressure increases and/or increase the rotational speed of the polishing head rotation.

Description

A device and method for polishing a silicon wafer

technical field

The invention relates to the field of silicon wafer production, in particular to a device and method for polishing silicon wafers.

Background technique

Silicon wafers can be obtained from monocrystalline silicon rods produced by direct method through multi-wire cutting. Silicon wafers need to go through multiple processing processes to obtain finished silicon wafers. During the processing of silicon wafers, polishing equipment is usually required to polish the silicon wafers. , that is to improve the flatness of the surface of the silicon wafer through the chemical action of the polishing liquid and the mechanical action of the friction between the polishing pad and the silicon wafer surface, wherein the main components of the polishing liquid are colloidal silicon dioxide, organic bases and other organic matter.

In a conventional polishing method, the polishing head performs indiscriminate polishing on the silicon wafer through its own rotational movement and translational movement relative to the silicon wafer until the silicon wafer is polished to meet the requirements, for example, the flatness of the silicon wafer meets the requirements.

However, in such a polishing method, since the surface of the silicon wafer to be polished is uneven, for example, the concave part of the silicon wafer surface will be continuously polished and thinned, but obviously this is not the case for the silicon wafer. It is unfavorable in terms of the flatness of the surface, and it takes a long time to make the flatness of the silicon wafer meet the requirements.

Contents of the invention

In order to solve the above technical problems, the embodiments of the present invention expect to provide a device and method for polishing a silicon wafer, which can obtain better flatness of the silicon wafer in a shorter time.

Technical scheme of the present invention is realized like this:

In a first aspect, an embodiment of the present invention provides a device for polishing a silicon wafer, the device comprising:

a rotary driver, the rotary driver is used to rotate the polishing head around its own central axis relative to the silicon wafer to polish the part of the silicon wafer that is in contact with the polishing head;

a translation driver configured to translate the polishing head relative to the silicon wafer in a plane parallel to the neutral surface of the silicon wafer to polish the entire main surface of the silicon wafer;

a sensor for sensing the pressure exerted by the polishing head on the silicon wafer, wherein the pressure is different due to the unevenness of the main surface of the silicon wafer;

A speed governor for reducing the translation speed of the polishing head translation and/or increasing the rotational speed of the polishing head rotation when the pressure increases.

In a second aspect, an embodiment of the present invention provides a method for polishing a silicon wafer, the method comprising:

rotating the polishing head around its central axis relative to the silicon wafer to polish the portion of the silicon wafer that is in contact with the polishing head;

translating the polishing head relative to the silicon wafer in a plane parallel to the neutral surface of the silicon wafer to polish the entire major surface of the silicon wafer;

sensing the pressure exerted by the polishing head on the silicon wafer, wherein the pressure is different due to the unevenness of the major surface of the silicon wafer;

The translational velocity at which the polishing head is translated is reduced and/or the rotational velocity at which the polishing head is rotated is increased as the pressure increases.

The embodiment of the present invention provides a device and method for polishing a silicon wafer. The protruding parts and concave parts of the silicon wafer are reflected by the pressure, that is, the greater the pressure, the more the polishing head is polishing the silicon wafer. The protruding part of the wafer or the part with a greater thickness is polished. In addition, it can be that the translational speed of the polishing head relative to the silicon wafer is constant, but the rotational speed of the polishing head is faster when the pressure increases. It may be that the rotational speed of the polishing head relative to the wafer is constant, but the translational speed of the polishing head is slower as the pressure increases, or that the rotational speed of the polishing head is not only faster but also The translation speed of the polishing head is slower, and like this, unlike the indiscriminate polishing of silicon wafers in the prior art, the present invention realizes the targeted polishing of silicon wafers, or in other words, for the thicker parts of silicon wafers In other words, the polishing efficiency is higher, so that better flatness of the silicon wafer can be obtained within a certain period of time.

Description of drawings

Fig. 1 shows a schematic front view of a device for polishing a silicon wafer according to an embodiment of the present invention;

Fig. 2 shows a schematic front view of the arrangement of the sensor in the device according to an embodiment of the present invention;

Fig. 3 shows a schematic top view of a translation driver of a device according to an embodiment of the present invention;

FIG. 4 shows a schematic diagram of a method for polishing a silicon wafer according to an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention.

Referring to FIG. 1 , an embodiment of the present invention provides a device 1 for polishing a silicon wafer W. In FIG. 1 , the silicon wafer W is schematically shown by a box filled with dots. include:

A rotary drive 10 for rotating the polishing head H relative to the wafer W around its central axis HX shown by a dotted line in FIG. 1 , as in FIG. The curved arrow of the axis HX is schematically shown to polish the part of the silicon wafer W that is in contact with the polishing head H;

A translation driver 20, the translation driver 20 is used to make the polishing head H translate relative to the silicon wafer W in a plane parallel to the neutral plane WP of the silicon wafer W, so that the entire surface of the silicon wafer W The main surface WS is polished, and the neutral plane WP is shown by a double-dotted line in Fig. 1. The neutral plane WP here can be understood as, for example, for a silicon wafer with an uneven upper main surface shown in Fig. 1 As far as W is concerned, there is such a plane: this plane is located in the middle of the silicon wafer W or is neither closer to the upper main surface nor closer to the lower main surface, then this plane is the silicon wafer W. Neutral plane WP, additionally shown schematically in Fig. 1 by the bidirectional arrow translational movement of polishing head H, additionally, as shown in Fig. 1, translational drive 20 can carry out direct drive to rotary drive 10, and The polishing head H can be arranged to be rotatably fixed to the rotary driver 10, that is to say, the translational driver 20 drives the polishing head H indirectly;

A sensor 30, the sensor 30 is used to sense the pressure F exerted by the polishing head H on the silicon wafer W, wherein the pressure F is different due to the unevenness of the main surface WS of the silicon wafer W , as shown in Figure 1, when the polishing head H is in the position shown by the dotted line, the polishing head H corresponds to the concave position on the silicon wafer W, so the pressure exerted by the polishing head H on the silicon wafer W F will be relatively small, and when the polishing head H is at the position shown by the solid line, it corresponds to the protruding part on the silicon wafer W, so the pressure F exerted by the polishing head H on the silicon wafer W will be relatively small , in addition, the size of the pressure F is shown by the length of the grouped arrows schematically representing the pressure F in Figure 1, so that the size of the pressure F is more intuitive;

A governor 40, the governor 40 is used to reduce the translation speed V1 of the translation of the polishing head H and/or increase the rotation speed V2 of the rotation of the polishing head H when the pressure F increases, FIG. 1, the reference sign V1 is marked near the bidirectional arrow representing the translational movement of the polishing head H, and the reference sign V2 is marked near the curved arrow representing the rotational movement of the polishing head H, so that the translational velocity V1 and the rotation Velocity V2 is more intuitive, and in addition, in the specific case shown in FIG. 1 , polishing head H translates at a slower velocity V1 and/or rotates at a position indicated by a solid line than in a position indicated by a dotted line. Speed V2 is faster.

In the above-mentioned embodiment, the protruding part and the concave part of the silicon wafer W are reflected by the pressure F, that is, the greater the pressure F is, the more the polishing head is working on the protruding part of the silicon wafer W or the thickness is larger. In addition, it can be that the translational velocity V1 of the polishing head H relative to the silicon wafer W is constant, but the rotational velocity V2 of the polishing head H is faster when the pressure F increases. It can also be that the polishing The rotation speed V2 of the head H relative to the silicon wafer W is constant, but the translation speed V2 of the polishing head H is slower when the pressure F increases. It is also possible that when the pressure F increases, not only the rotation of the polishing head H The speed V2 is faster and the translation speed of the polishing head H is slower. In this way, unlike the indiscriminate polishing of silicon wafers in the prior art, the present invention realizes the targeted polishing of silicon wafer W, or in other words, for silicon wafers The polishing efficiency is higher for the thicker part of the W, so that better flatness of the silicon wafer W can be obtained within a certain period of time.

For some silicon wafers W, its flatness may be very poor. In order to further improve the polishing efficiency of such silicon wafers W, in a preferred embodiment of the present invention, when the pressure F detected by the sensor 30 When it is greater than the set critical value, that is to say, when the silicon wafer W has a very poor flatness and its large thickness part has caused the pressure F to be greater than a certain set value, the governor 40 can increase the translation speed V1 is reduced to zero, in this way, the polishing head H can only be polished for such a large-thickness part and no longer translates relative to the silicon wafer W, so that such a large-thickness part can be thinned faster and obtain faster Better flatness of wafer W.

In order to realize the above-mentioned sensing function of the sensor 30 in a simpler manner, in a preferred embodiment of the present invention, referring to FIG. 2 , the pressure F can be applied to the polishing head H by the sensor 30. F0 is generated, as shown schematically by the hollow arrow in Fig. 2, obviously, the pressure F is equal to the force F0, and the polishing head H will produce an equal reaction force on the sensor 30, thus, in When a force acts on the sensor 30, the sensor 30 can sense the force. In addition, referring back to FIG. 1, it can be understood that the sensor 30 shown in FIG. 2 can be arranged between the polishing head H and the rotary drive 10, for example, and the polishing head H can be arranged to be able to rotate relative to the center axis HX of itself. The movement of the driver 10 is easily realized by those skilled in the art through conventional technical means, and will not be repeated here.

In the case that the sensor 30 is arranged in the above-mentioned manner, in a preferred embodiment of the present invention, the sensor 30 can be a piezoresistive pressure sensor. For this type of pressure sensor, the resistance value of the element will vary with Changes due to mechanical strain generated by mechanical pressure are applicable to the above-mentioned situation and can respond promptly and quickly to changes in mechanical pressure.

In order to make the polishing head H complete the above-mentioned translational movement, in a preferred embodiment of the present invention, referring to FIG. The guide rail 22 rotates, as shown schematically by arrow A1 in FIG. , it can be easily understood in conjunction with FIG. 1 that in this case the pivot 21 is perpendicular to the neutral plane WP or the linear guide 22 is parallel to the neutral plane WP. In addition, as shown in FIG. 3 , the straight line The guide rail 22 rotates from the position shown by the dotted line to the position shown by the solid line, and the polishing head H moves from the position shown by the dotted line to the position shown by the solid line through the rotation of the linear guide rail 22 and the movement on the linear guide rail 22 .

Preferably, referring back to FIG. 1 , the polishing head H may include a body H1 and a polishing pad H2 fixed to the body H1 and in contact with the silicon wafer W to polish the silicon wafer W. When the polishing pad H2 is rigid but flexible, the difference in the pressure F is actually caused by the difference in the degree of deformation or compression of the polishing pad H2.

Preferably, the rotary driver 10 may be a rotary motor.

Referring to FIG. 4 in combination with FIG. 1 , an embodiment of the present invention also provides a method for polishing a silicon wafer W, the method may include:

S401: Rotate the polishing head H around its own central axis HX relative to the silicon wafer W to polish the portion of the silicon wafer W that is in contact with the polishing head H;

S402: Translate the polishing head H relative to the silicon wafer W in a plane parallel to the neutral plane WP of the silicon wafer W to polish the entire main surface WS of the silicon wafer W;

S403: Sensing the pressure F exerted by the polishing head H on the silicon wafer W, wherein the pressure F is different due to the unevenness of the main surface WS of the silicon wafer W;

S404: Decrease the translation velocity V1 of the translation of the polishing head H and/or increase the rotation velocity V2 of the polishing head H when the pressure increases.

In the above method, preferably, when the sensed pressure F is greater than a set threshold, the translation velocity V1 may be reduced to zero.

In the above method, preferably, it is easy to understand with reference to FIG. 3 that the translation of the polishing head H can be performed by rotating the polishing head H around the axis and rotating the polishing head H along the axis in the same manner. The straight line is moved to achieve.

It should be noted that: the technical solutions described in the embodiments of the present invention can be combined arbitrarily if there is no conflict.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (10)

1. An apparatus for polishing a silicon wafer, the apparatus comprising:

a rotary driver for rotating the polishing head around its central axis relative to the silicon wafer to polish a portion of the silicon wafer in contact with the polishing head;

a translation driver for translating the polishing head relative to the silicon wafer in a plane parallel to a neutral surface of the silicon wafer to polish the entire major surface of the silicon wafer;

a sensor for sensing a pressure applied by the polishing head on the silicon wafer, wherein the pressure is different due to unevenness of the main surface of the silicon wafer;

a speed governor to reduce a translational speed of translation of the polishing head and/or to increase a rotational speed of rotation of the polishing head when the pressure increases.

2. The apparatus of claim 1, wherein the governor reduces the translational velocity to zero when the pressure sensed by the sensor is greater than a set threshold.

3. An apparatus as defined in claim 1 or 2, wherein the pressure is generated by a force applied to the polishing head by the sensor.

4. The device of claim 3, wherein the sensor is a piezoresistive pressure sensor.

5. The apparatus of claim 1, wherein the translation actuator comprises a pivot and a linear guide, the pivot configured to guide the linear guide to rotate, and the linear guide configured to guide the polishing head to move in a straight line.

6. An apparatus as set forth in claim 1 wherein the polishing head comprises a body and a polishing pad secured to the body and in contact with the silicon wafer to polish the silicon wafer.

7. The device of claim 1, wherein the translation drive is a rotary motor.

8. A method for polishing a silicon wafer, the method comprising:

rotating a polishing head around a central axis of the polishing head relative to the silicon wafer to polish a part of the silicon wafer, which is in contact with the polishing head;

translating the polishing head relative to the silicon wafer in a plane parallel to a neutral surface of the silicon wafer to polish the entire major surface of the silicon wafer;

sensing a pressure exerted by the polishing head on the silicon wafer, wherein the pressure is different due to unevenness of the main surface of the silicon wafer;

reducing a translation speed of the polishing head translation and/or increasing a rotation speed of the polishing head rotation when the pressure increases.

9. The method of claim 8, wherein the translation speed is reduced to zero when the sensed pressure is greater than a set threshold.

10. A method as set forth in claim 8 wherein translating the polishing head is accomplished by rotating the polishing head about an axis and moving the polishing head along a straight line that rotates in the same manner about the axis.

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