TWI855563B - Polishing heads and polishing equipment - Google Patents

Abstract

The embodiment of the present invention discloses a polishing head and a polishing device, wherein the polishing head comprises: a head body; an adsorption port arranged on the lower surface of the head body, the adsorption port is used to adsorb a silicon wafer so that the silicon wafer can move together with the head body; a first discharge port arranged on the lower surface of the head body, the first discharge port is arranged on the outer side of the adsorption port along the radial direction, and is used to discharge gas on the circumferential outer side of the silicon wafer when the silicon wafer is polished, so as to reduce the amount of polishing liquid near the edge of the silicon wafer.

Description

Polishing heads and polishing equipment

The present invention belongs to the field of semiconductor manufacturing technology, and in particular to a polishing head and a polishing device.

In the process of producing silicon wafers, the final polishing (FP) process is the last step to control the flatness and roughness parameters of the silicon wafer. The final polishing process is to remove a certain amount of silicon wafer surface to remove front-end process defects and mirror-polish the silicon wafer surface.

During the FP operation, the most commonly used implementation scheme is the Chemical Mechanical Polishing (CMP) method. The chemical mechanical polishing process of silicon wafers is a complex multi-reaction process, which can be specifically divided into two kinetic processes: first, the kinetic process of oxidation-reduction of the oxidant, catalyst, etc. in the polishing liquid adsorbed on the polishing pad with the silicon atoms on the surface of the silicon wafer, and secondly, the decomposition process of the reactants on the polished surface of the silicon wafer, that is, the kinetic process of re-exposing the unreacted silicon atoms. The chemical mechanical polishing process is a combination of mechanical friction and chemical corrosion, taking into account the advantages of both, and can obtain a flat silicon wafer surface.

In the CMP method, the silicon wafer needs to be pressed onto a vibrating polishing table with a polishing pad by a polishing head, and the polishing liquid is supplied to the polishing pad at the same time. During the polishing process, the polishing head and the polishing table rotate relative to each other, and the polishing liquid is distributed on the polishing pad by the centrifugal force generated by the rotation of the polishing table. However, it is also because of the centrifugal force that the amount of slurry in the central area of the polishing pad is less than that in the edge area of the polishing pad, resulting in the polishing removal amount of the edge area of the silicon wafer surface being greater than the polishing removal amount of the central area of the silicon wafer surface, thereby causing the flatness of the silicon wafer surface to deteriorate.

In view of this, the embodiments of the present invention are intended to provide a polishing head and a polishing device that can polish a silicon wafer under a uniform working pressure, thereby improving the quality of the planarization of the silicon wafer.

The technical solution of the present invention is implemented as follows: In the first aspect, an embodiment of the present invention provides a polishing head, which includes: A head body; A suction port disposed on the lower surface of the head body, the suction port is used to adsorb a silicon wafer so that the silicon wafer can move with the head body; A first discharge port disposed on the lower surface of the head body, the first discharge port is disposed on the outer side of the suction port in the radial direction, and is used to discharge gas on the circumferential outer side of the silicon wafer when the silicon wafer is polished, so as to reduce the amount of polishing liquid near the edge of the silicon wafer.

In a second aspect, an embodiment of the present invention provides a polishing device, which includes a polishing head according to the first aspect.

The embodiment of the present invention provides a polishing head and a polishing device; the polishing head absorbs a silicon wafer through an absorption port provided on the lower surface of a head main body, so that the silicon wafer is fixed to the head main body and can move with the head main body; a first discharge port is also provided on the lower surface of the head main body of the polishing head, and the first discharge port is provided to be able to discharge the silicon wafer when the silicon wafer is polished. Gas is discharged on the circumferential outer side of the silicon wafer, thereby forming a gas barrier on the circumferential outer side of the silicon wafer. The gas barrier can prevent excessive polishing liquid from gathering on the edge of the silicon wafer, reduce the amount of polishing liquid polishing the edge of the silicon wafer, thereby avoiding excessive polishing of the edge of the silicon wafer and improving the flatness of the polished silicon wafer.

In order to help you understand the technical features, contents and advantages of the present invention and the effects it can achieve, the present invention is described in detail as follows with the accompanying drawings and appendices in the form of embodiments. The drawings used therein are only for illustration and auxiliary description, and may not be the true proportions and precise configurations after the implementation of the present invention. Therefore, the proportions and configurations of the attached drawings should not be interpreted to limit the scope of application of the present invention in actual implementation.

In the description of the embodiments of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. 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.

The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention.

After the double-sided polishing process, the silicon wafer usually has slight scratches on the surface. In order to remove the scratches, make the silicon wafer into a mirror surface and continuously improve the flatness, the FP operation is usually performed. The conventional FP operation is to put the polishing head loaded with the silicon wafer in contact with the surface of the polishing pad attached to the lower platen, and the colloidal slurry supplied by the slurry tube and the chemical react chemically, and the surface of the silicon wafer is polished due to the physical reaction caused by mechanical pressure.

Specifically, the silicon wafer that has completed the double-sided polishing process will be placed in the cleaning machine, and then the FP operation will be performed after it is discharged from the cleaning machine. The complete FP operation process includes three polishing operations, as follows: First, the silicon wafer is subjected to the first FP step, which can also be called the rough polishing (Stock Polishing) step. This step is used to remove the surface defects caused by the previous step of the silicon wafer and make it into a mirror state; this step is used to adjust the abrasive particles (Particles) in the operation process and the flatness of the entire silicon wafer surface. After the rough polishing step, the second FP step is performed, which adjusts the abrasive particles and adjusts the roughness of the silicon wafer surface by using the minimum grinding amount. After the second FP step is completed, the third FP step will be carried out, which is used to adjust the micro roughness and fine particles on the surface of the silicon wafer and complete the finishing work. After the silicon wafer completes the above three steps of FP operation, it will undergo a simple surface cleaning in the equipment and finally be placed in the unloading cassette. After the unloading cassette is full of silicon wafers, the waiting process will be carried out.

For the first FP step in the above operation flow, i.e., the rough polishing step, during the operation, the final polishing (Finish Polishing, FP) FP device 100 that can implement the technical solution of the embodiment of the present invention is shown in FIG. 1 . The FP device 100 may specifically include: a polishing head 101, an adsorption pad 102, a polishing liquid supply pipeline 103, a polishing disc 104, a polishing pad 105 attached to the polishing disc 104, a first drive shaft 106, and a second drive shaft 107. When the FP device 100 is used to perform the final polishing on the silicon wafer W, when the adsorption pad 102 is adsorbed on the back of the silicon wafer W, a certain supply flow rate of polishing liquid is supplied to the polishing pad 105 through the polishing liquid supply pipeline 103. After the polishing liquid is supplied to the polishing pad 105 and contacts the silicon wafer W, the first driving shaft 106 and the second driving shaft 107 are used to drive the polishing disc 104 and the polishing head 101 to rotate relative to each other, and pressure is applied to the silicon wafer W through the polishing head 101 to complete the final polishing operation of the silicon wafer W. By performing the final polishing operation on the silicon wafer W, the damaged surface of the silicon wafer W generated in the previous mechanical processing process can be removed. These damaged surfaces are chemically softened by the polishing liquid in the final polishing process, and the chemically softened damaged surface can be removed by mechanical movement with the polishing pad 105. After repeatedly performing the above-mentioned final polishing process, the damaged surface on the surface of the silicon wafer W is completely removed, and finally the surface of the silicon wafer W is flattened.

When the FP device 100 is used for final polishing, the silicon wafer and the polishing pad are always in a relative rotating state, and the centrifugal effect caused by the rotation often causes the polishing liquid to gather at the edge of the silicon wafer, which makes the polishing removal amount of the edge area of the silicon wafer surface greater than the polishing removal amount of the central area of the silicon wafer surface. The uneven polishing removal amount ultimately leads to the deterioration of the flatness of the silicon wafer surface.

In this regard, the embodiments of the present invention provide a polishing head and a polishing device, which can improve the flatness level of the polished silicon wafer by intervening in the distribution and composition of the polishing liquid in the polishing area of the silicon wafer.

Referring to FIG. 2 , in the first aspect, the embodiment of the present invention proposes a polishing head 200, which includes: A head body 201; An adsorption port 202 disposed on the lower surface 201a of the head body 201, the adsorption port 202 is used to adsorb the silicon wafer W so that the silicon wafer W can move with the head body 201; A first discharge port 203 disposed on the lower surface 201a of the head body 201, the first discharge port 203 is disposed on the outer side of the adsorption port 202 in the radial direction, and is used to discharge gas on the circumferential outer side of the silicon wafer W when the silicon wafer W is polished, so as to reduce the amount of polishing liquid near the edge of the silicon wafer W.

As shown in FIG. 2 , the head body 201 has a pipeline LL running through the center thereof in the longitudinal direction. The pipeline LL leads to the suction port 202 so that a negative pressure can be formed at the suction port 202 to suction the silicon wafer W to the polishing head 200, so that the polishing head 200 can drive the silicon wafer W to move along with it. A first discharge port 203 is also provided on the outside. The first discharge port 203 is also located on the circumferential outer side of the silicon wafer W adsorbed to the polishing head 200, and is used to discharge gas on the circumferential outer side of the silicon wafer W to disperse the polishing liquid gathered near the edge of the silicon wafer W, reduce the amount of polishing liquid near the edge of the silicon wafer W, thereby reducing the polishing amount of the silicon wafer edge and improving the surface flatness of the polished silicon wafer.

The embodiment of the present invention provides a polishing head 200; the polishing head 200 adsorbs a silicon wafer W through an adsorption port 202 disposed on a lower surface 201a of a head main body 201, so that the silicon wafer W is fixed to the head main body 201 and can move with the head main body 201; a first discharge port 203 is also disposed on the lower surface 201a of the head main body 201 of the polishing head 200, and the first discharge port 203 is disposed on the lower surface 201a of the head main body 201 of the polishing head 200. Port 203 is configured to discharge gas on the circumferential outer side of the silicon wafer W when the silicon wafer W is polished, thereby forming a gas barrier on the circumferential outer side of the silicon wafer W. The gas barrier can prevent excessive polishing liquid from gathering on the edge of the silicon wafer, thereby reducing the amount of polishing liquid used to polish the edge of the silicon wafer, thereby avoiding excessive polishing of the edge of the silicon wafer and improving the flatness of the polished silicon wafer.

In order to further reduce the polishing of the edge portion of the silicon wafer, optionally, as shown in Figures 2 and 3, the polishing head 200 also includes a second discharge port 204 arranged on the lower surface 201a of the head body 201, and the second discharge port 204 is located between the suction port 202 and the first discharge port 203 along the radial direction, and is used to discharge liquid on the circumferential outer side of the silicon wafer W when the silicon wafer W is polished, so as to reduce the concentration of the polishing liquid near the edge of the silicon wafer W.

As shown in FIG. 2 and FIG. 3 , a second discharge port 204 is provided between the suction port 202 and the first discharge port 203 along the radial direction of the lower surface 201a of the head body 201. The second discharge port 204 is used to discharge liquid on the circumferential outer side of the silicon wafer W to dilute the polishing liquid near the edge of the silicon wafer and reduce its concentration, thereby avoiding over-polishing of the edge of the silicon wafer.

In order to dilute the polishing liquid without bringing other negative effects to the polishing liquid, optionally, the liquid is deionized water or a strong alkaline solution, wherein the pH value of the strong alkaline solution is greater than 11, and particularly optionally, the pH value of the strong alkaline solution is about 12. The strong alkaline solution can react chemically with the grinding components in the grinding liquid, such as silicon dioxide, to form a colloidal solution, so as to effectively reduce the polishing ability of the polishing liquid.

For the implementation form of the first discharge port, for example, it can be formed as a circular opening. In order to discharge the gas more evenly, optionally, as shown in FIG3 , the polishing head 200 includes a plurality of the first discharge ports 203 arranged along the circumferential direction of the lower surface 201a of the head body 201, that is, a plurality of discrete first discharge ports 203, each of which can be evenly spaced from each other. In the embodiment shown in FIG3 , each first discharge port is rectangular, and it is conceivable that the first discharge port can be in other shapes, such as circular, oblong, etc.

According to another optional embodiment of the present invention, as shown in Fig. 3, the polishing head 200 includes a plurality of second discharge ports 204 arranged along the circumferential direction of the lower surface 201a of the head body 201. In the embodiment shown in Fig. 3, the second discharge ports 204 are circular, and of course, the second discharge ports 204 can also be formed in other shapes, such as rectangle, triangle, etc.

The discharge start time and duration of the first discharge port 203 and the second discharge port 204 can be selected according to the actual production situation. For a polishing operation, in the initial stage of polishing, neither the first discharge port 203 nor the second discharge port 204 performs discharge, so that the silicon wafer can fully contact with the polishing liquid and obtain the necessary polishing. In the middle stage of polishing, the first discharge port 203 can be intermittently discharged gas and the second discharge port 204 can be intermittently discharged liquid to avoid over-polishing of the edge of the silicon wafer.

In order to accurately control the first discharge port 203 and the second discharge port 204 according to actual production needs, optionally, referring to FIG. 2 , the polishing head further includes a controller 205 , which is used to control the discharge of the first discharge port 203 and the second discharge port 204 .

In order to realize the rotational motion of the polishing head around its own axis and the translational motion on the polishing pad, optionally, as shown in FIG. 2 , the polishing head 200 further includes a driver 206 for driving the polishing head to move.

In order not to contaminate the polishing liquid, the gas is optionally an inert gas, for example, the gas may be nitrogen.

In the second aspect, referring to FIG. 4 , an embodiment of the present invention provides a polishing device 300, which includes the polishing head 200 according to the first aspect.

It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict.

In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in an appropriate manner. The above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. If the present invention is modified or replaced by an equivalent without departing from the spirit and scope of the present invention, it should be included in the protection scope of the patent application of the present invention.

100: FP device 101: polishing head 102: adsorption pad 103: polishing liquid supply pipeline 104: polishing plate 105: polishing pad 106: first drive shaft 107: second drive shaft 200: polishing head 201: head body 201a: lower surface 202: adsorption port 203: first discharge port 204: second discharge port 205: controller 206: driver 300: polishing equipment W: silicon wafer LL: pipeline

Figure 1 is a schematic diagram of the structure of a conventional polishing device provided in an embodiment of the present invention; Figure 2 is a front view of a polishing head provided in an embodiment of the present invention; Figure 3 is a bottom view of a polishing head provided in an embodiment of the present invention; Figure 4 is a schematic diagram of the structure of a polishing device provided in an embodiment of the present invention.

200: Polished head

201: Head body

201a: Lower surface

202: Adsorption port

203: First discharge port

204: Second discharge port

205: Controller

206:Driver

W: Silicon wafer

LL: Pipeline

Claims (9)

A polishing head includes: a head body; a suction port disposed on the lower surface of the head body, the suction port being used to suction a silicon wafer so that the silicon wafer can move together with the head body; a first discharge port disposed on the lower surface of the head body, the first discharge port being disposed on the outer side of the suction port in a radial direction, and being used to discharge gas on the circumferential outer side of the silicon wafer when the silicon wafer is polished, so as to reduce the amount of polishing liquid near the edge of the silicon wafer. A polishing head as described in claim 1, wherein the polishing head further includes a second discharge port arranged on the lower surface of the head body, and the second discharge port is located between the adsorption port and the first discharge port in the radial direction, and is used to discharge liquid on the circumferential outer side of the silicon wafer when the silicon wafer is polished to reduce the concentration of the polishing liquid near the edge of the silicon wafer. A polishing head as described in claim 2, wherein the liquid is deionized water or a strong alkaline solution, wherein the pH value of the strong alkaline solution is greater than 11. A polishing head as described in claim 1, wherein the polishing head includes a plurality of first discharge ports arranged in a circumferential direction along the lower surface of the head body. A polishing head as described in claim 2, wherein the polishing head includes a plurality of second discharge ports arranged in a circumferential direction along the lower surface of the head body. A polishing head as described in any one of claim 2, 3 or 5, wherein the polishing head further includes a controller for controlling the discharge of the first discharge port and the second discharge port. A polishing head as described in any one of claims 1 to 5, wherein the polishing head also includes a driver for driving the polishing head to move. A polishing head as described in any one of claims 1 to 5, wherein the gas is an inert gas. A polishing device, comprising the polishing head as described in any one of claims 1 to 8.

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