KR100931197B1 - Head Assembly for Wafer Polishing Machine - Google Patents

Abstract

Disclosed is a wafer polishing apparatus that improves a thickness profile of a wafer and improves surface flatness. The head assembly for a wafer polishing apparatus includes a holder plate having a buffer portion and a membrane coupled to the buffer portion to pressurize the wafer as air flows into the buffer portion while being in surface contact with the wafer. On the surface of the holder plate to be formed a plurality of dimples for improving the response of the air flow in the buffer portion is formed. Therefore, since the air flow rate in the buffer portion is increased and the air pressure change is quickly transmitted to the edge portion, the thickness profile and the surface flatness of the edge portion of the wafer can be improved.

CMP, Polishing Head Assembly

Description

Head assembly for wafer polishing machine {APPARATUS FOR POLISHING WAFER HAVING HEAD ASSEMBLY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer chemical mechanical polishing apparatus, and more particularly, to a wafer polishing apparatus having a polishing head assembly for improving surface flatness after polishing a wafer.

The silicon substrate widely used today as a material for manufacturing a semiconductor device refers to a single crystalline silicon thin film made of polycrystalline silicon as a raw material.

The wafer manufacturing process includes a slicing process that cuts grown silicon single crystal ingots into wafer forms, a lapping process to uniformize and planarize the thickness of the wafer, and remove or mitigate damage caused by mechanical polishing. An etching process, a polishing process for mirror-mirroring the wafer surface, and a cleaning process for cleaning the polished wafer and removing foreign matter adhered to the surface.

Due to the high integration of semiconductor devices, the lapping process or the chemical mechanical double side polishing (DSP) process in the semiconductor substrate manufacturing process yields the yield of the device in the semiconductor manufacturing process such as flatness, scratch or defect of the semiconductor substrate. And it is recognized as one of the important factors that have a great influence on the productivity.

Chemical mechanical polishing (CMP) provides a slurry composed of abrasive particles and various chemical liquids to a substrate, and the surface of the substrate by chemical reaction between the slurry and the substrate and mechanical action of the abrasive particles and the polishing pad. It is a method of flattening by removing unevenness.

Typically, the polishing apparatus for performing the CMP process includes a surface plate having a polishing pad, a polishing head for fixing and pressing the wafer, and a driving unit for pressing and rotating the polishing head against the surface plate. In addition, a slurry is provided between the polishing pad and the wafer, which is a polishing agent including abrasive particles.

On the other hand, the conventional polishing head is provided with a membrane in contact with the wafer, a buffer portion is formed between the polishing head and the membrane. Therefore, as air is injected into the buffer part, the membrane expands and pressurizes the wafer.

Here, the air pressure supplied into the buffer unit is continuously changed according to the degree of polishing of the wafer. However, in the conventional polishing head, there is a problem in that the flow of air in the buffer unit does not respond quickly to a change in air pressure supplied. As a result, the pressing force acting on the surface of the wafer becomes nonuniform, resulting in poor polishing quality of the wafer. In particular, due to the surface friction between the inner surface of the buffer portion and air, the air flow responsiveness at the edge portion corresponding to the edge of the wafer is the slowest, which causes a problem that the polishing quality of the wafer edge is deteriorated. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a head assembly for a wafer polishing apparatus for preventing the deterioration of flatness at the edge of the wafer and improving the polishing quality.

According to embodiments of the present invention for achieving the above object of the present invention, a wafer assembly head assembly is coupled to the holder plate to seal the buffer portion and a holder plate formed with a buffer portion indented on one surface, the wafer And a membrane of a soft material pressurizing the wafer as air is introduced into the buffer portion in surface contact with the substrate. Here, a plurality of dimples are densely formed on the surface of the holder plate toward the buffer part.

In an embodiment, the dimple has a diameter of 0.01 to 1 μm in size. The dimples are densely formed such that neighboring dimples are continuous with each other to increase the density.

In an embodiment, the dimple may have a polygonal shape. For example, the dimple has a hexagonal shape. Alternatively, the dimples may have a circular shape.

In an embodiment, an inlet hole for introducing air into the buffer part is formed through the central portion of the holder plate.

In an embodiment, the membrane is formed of a flexible and soft material such that the membrane is in surface contact with the wafer and does not cause damage to the wafer surface. The membrane has elasticity to uniformly pressurize the wafer by air introduced into the buffer portion. For example, the membrane is formed of a rubber material.

According to the present invention, first, by forming a plurality of dimples on the inner surface of the buffer portion in which air is introduced from the head assembly to pressurize the membrane, thereby stabilizing the air flow in the buffer portion and increasing the flow rate, thereby responsiveness of the air flow Can improve.

Second, the pressure is uniformly applied to the wafer due to the increased response in the buffer unit, thereby improving the polishing flatness of the wafer. In particular, the flatness of the edge portion of the wafer can be improved.

Although the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, the present invention is not limited or restricted by the embodiments.

1 is a side cross-sectional view illustrating a wafer polishing apparatus and a head assembly according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating the head assembly in FIG. 1, and FIG. 3 is a plan view of the holder plate of FIG. 2. 4 is a cross-sectional view for describing an operation of the head assembly of FIG. 2.

Hereinafter, a wafer polishing apparatus and a head assembly according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4.

The wafer polishing apparatus 100 includes a surface plate 150 and a polishing head 130.

The surface plate 150 rotates while being in contact with one surface of the wafer W to planarize the surface of the wafer W. FIG. A surface of the surface 150 in contact with the wafer W is provided with a polishing pad (not shown) for polishing the surface of the wafer (W).

The polishing head 130 is provided on the surface plate 150 to fix the other surface of the wafer (W). The polishing head 130 polishes the wafer W by pressing and rotating the wafer W against the surface plate 150.

The polishing head 130 is a head assembly 110 to which the wafer W is fixed, a template assembly 131 to fix the wafer W, and a driving unit 135 for rotation and movement of the polishing head 130. ).

The driving unit 135 rotates and linearly moves the polishing head 130. That is, the polishing head 130 is pressed against the surface plate 150 while the wafer W is fixed to the head assembly 110, and the wafer is rotated as the polishing head 130 rotates. (W) is polished. After the polishing of the wafer W is completed, the wafer W is moved to be separated from the polishing head 130 and the surface plate.

The template assembly 131 is coupled around the outer circumference of the wafer W to fix the position of the wafer W, and has a ring shape corresponding to the diameter of the wafer W.

The head assembly 110 includes a holder plate 111, a buffer portion 113, and a membrane 120.

The holder plate 111 is coupled to the polishing head 130 and is formed to fix one surface of the wafer (W). For example, the holder plate 111 has a disk-shaped plate of a predetermined thickness. The holder plate 111 is made of aluminum.

Here, a plurality of fixing holes 115 are formed along the outer periphery of the holder plate 111. The fixing hole 115 is a portion for coupling the holder plate 111 to the polishing head 130 and is formed through the holder plate 111 to be bolted.

One surface of the holder plate 111 is recessed in a predetermined depth to form a buffer portion 113. In addition, an inlet hole 114 is formed through the center of the holder plate 111 to allow air to flow into the buffer unit 113.

The buffer part 113 is a part for expanding the membrane 120 to press the wafer W. That is, as air flows into the buffer unit 113, the membrane 120 expands and the wafer W is pressurized.

The membrane 120 is coupled to the opened upper portion of the buffer 113. The membrane 120 serves to press the wafer W against the surface plate 150 in a state of being directly in surface contact with the wafer W. In particular, the membrane 120 allows the pressure to be uniformly applied to the wafer (W).

Here, since the surface state of the wafer W is continuously changed during the polishing process of the wafer W, the air pressure flowing into the buffer portion 113 is continuously changed according to the surface state of the wafer W. . In addition, the membrane 120 should be able to react quickly to the air pressure change in the buffer unit 113 and to quickly transmit the air pressure change of the buffer unit 113 to the wafer (W).

In detail, the membrane 120 has a sufficiently thin thickness and elasticity so as to quickly react to a change in air pressure in the buffer unit 113. In addition, since the membrane 120 is in direct surface contact with the wafer W, the membrane 120 is formed of a soft material. For example, the membrane 120 is formed of a rubber material.

In addition, the membrane 120 is opened of the buffer part 113 to completely seal the buffer part 113 so that the air pressure change in the buffer part 113 can be accurately transmitted to the membrane 120. It is provided to completely cover the top.

On the other hand, in order to improve the surface flatness of the wafer W, the air flow in the buffer portion 113 should be uniform at both the center and the edge. In addition, the variation of the air pressure flowing through the inlet hole 114 should be quickly transmitted to the edge of the buffer unit 113.

In the present embodiment, in order to uniformize the flow of air introduced into the buffer unit 113 and to increase the flow rate, a plurality of dimples are formed on the concave surface forming the buffer unit 113 in the holder plate 111. A dimple face 112 on which the 112a is formed is formed.

By reducing the frictional force of the surface by forming the dimple surface 112, it is possible to eliminate the turbulence caused by the frictional force on the surface of the holder plate 111 and the membrane 120, the air flow rate Can improve. The flow on the dimple face 112 is described in detail with reference to FIG. 5B.

The dimple surface 112 has a plurality of dimples 112a formed densely. In particular, the dimple 112a is formed to a nano size of 1 μm or less.

The dimple 112a is densely formed on the dimple surface 112. For example, the dimples 112a are formed in a polygonal shape, and neighboring dimples 112a are formed to be continuous with each other. For example, the dimples 112a have a hexagonal shape and are continuously formed in a honeycomb form.

In addition, the dimple surface 112 is formed to minimize the friction or resistance of the air flow. For example, the dimple surface 112 is formed by recessing a predetermined depth from the surface of the holder plate 111, the recessed surface is formed as a smooth curved surface having a predetermined curvature.

5a to 6b are graphs for explaining the effect of the head assembly according to an embodiment of the present invention.

5B and 6B are graphs of a head assembly according to the present invention (hereinafter referred to as an embodiment), and FIGS. 5A and 6A are comparative examples of an embodiment, and a head assembly according to the prior art ( Hereinafter, it is a graph for 'comparative example'.

First, FIGS. 5A and 5B are graphs showing air flow in a buffer unit in Examples and Comparative Examples, respectively.

5A and 5B, it is understood that the embodiment forms a plurality of dimples 112a such that the air flow in the buffer portion 113 becomes uniform along the vertical cross-sectional direction of the buffer portion 113. Can be. In addition, the maximum flow rate in the comparative example is about 1.5, the maximum flow rate in the embodiment is about 1.8, it can be seen that the flow rate on the surface of the membrane 120 is increased in the embodiment compared to the comparative example. In addition, such an increase in the flow rate improves the response of the air flow in the buffer unit 113.

In addition, in the embodiment, it can be seen that the flow rates of the central portion and the edge portion of the buffer unit 113 are also uniform. Therefore, according to the embodiment, since the air pressure change in the buffer unit 113 is rapidly transmitted to the edge of the buffer unit 113, pressure is uniformly applied to the surface of the wafer W, and the wafer ( Since the pressure applied to the wafer W is quickly changed according to the polishing state of W), the flatness of the wafer W can be improved.

6A and 6B are graphs showing the degree of improvement in polishing quality of a wafer by using a head assembly according to an embodiment of the present invention. In detail, FIGS. 6A and 6B measure the quality of the wafer before polishing and after polishing, and show the difference (delta (Δ) value), respectively, indicating that the higher the value, the better the polishing result.

FIG. 6A is a graph showing the results of measuring edge roll-offs of wafer edge portions before and after polishing in Examples and Comparative Examples, respectively. FIG.

Looking at the thickness profile of the wafer W, a slope occurs at the edge portion of the wafer W. For example, the edge portion is bent in a roll-up or roll-off form. Such inclination of the edge portion deteriorates the flatness of the wafer W and causes a defect in a subsequent process.

Referring to FIG. 6A, it can be seen that the Example has a larger delta (Δ) value than the Comparative Example. Thus, it can be seen that the embodiment has a small size of edge roll-off, which is the thickness profile of the edge portion.

FIG. 6B is a graph showing the delta (Δ) value of site flatness (SFQR) site front flatness (SFQR) polished using Examples and Comparative Examples.

Referring to FIG. 6B, when the SFQR value is high, the flatness is deteriorated. When the SFQR value is low, the flatness is good. In the comparative example, the surface flatness is -0.75, whereas in the example, the flatness is -0.65. It can be seen that the polished surface flatness is improved compared to the comparative example.

As described above, although described with reference to the preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

1 is a side view of a wafer polishing apparatus according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view illustrating a head assembly in the wafer polishing apparatus of FIG. 1; FIG.

3 is a plan view of a holder plate in the head assembly of FIG. 2;

4 is a cross-sectional view for explaining the operation of the head assembly of FIG.

Figure 5a is a graph showing the air flow in the buffer portion in the comparative example;

5B is graphs showing air flow in the buffer portion in the embodiment;

6A and 6B are graphs showing the results of polishing a wafer using Comparative Examples and Examples, respectively, and FIG. 6A is an edge roll-off profile of a wafer edge portion before and after polishing in Comparative Examples and Examples. 6B is a graph showing the difference in flatness of the wafer surface before and after polishing in Comparative Examples and Examples.

<Explanation of symbols for the main parts of the drawings>

100: wafer polishing apparatus 110: head assembly

111: holder plate 112: dimple surface

112a: dimple 113: buffer portion

114: inflow hole 115: fixing hole

120: membrane 130: polishing head

131: template assembly 135: drive unit

150: surface plate W: wafer

Claims (7)

A holder plate having a buffer portion inserted into one surface thereof; And A membrane of a flexible material coupled to the holder plate to seal the buffer part and pressurizing the wafer as air is introduced into the buffer part in surface contact with the wafer; Including, And a plurality of dimples are densely formed on a surface of the holder plate facing inwardly of the buffer part. The method of claim 1, The size of the dimple is a head assembly for a wafer polishing apparatus, characterized in that 0.01 to 1 ㎛. The method of claim 2, The dimple is a head assembly for a wafer polishing apparatus, characterized in that the adjacent dimples are formed continuously with each other. The method of claim 3, The dimple is a head assembly for a wafer polishing apparatus, characterized in that the shape of the recessed portion has a polygonal shape. delete The method of claim 1, An inlet hole is formed through the central portion of the holder plate for injecting air into the buffer portion. The method of claim 1, The membrane assembly of claim 1, wherein the membrane is formed of a rubber material.

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