KR20110059145A - Wafer carrier and apparatus for polishing double side of wafer having the same - Google Patents

Abstract

PURPOSE: A wafer carrier and an apparatus for polishing both sides of a wafer adopting the same are provided to improve flatness by changing the structure of a carrier mounting hole for mounting the wafer. CONSTITUTION: A polishing pad is attached to the upper side of a bottom surface plate. A polishing pad is attached to the lower side of a top surface plate. The top surface plate rotates and pressurizes the wafer. A wafer carrier(100) is interposed between the top surface plate and the bottom surface plate. A mounting hole(110) is formed on the wafer carrier.

Description

Wafer carrier and apparatus for polishing double side of wafer having the same}

The present invention relates to a wafer carrier and a wafer double-side polishing apparatus employing the same, and more particularly, to a wafer carrier and a wafer double-side polishing apparatus employing the same to improve the flatness by rotating the wafer during the double-side polishing of the wafer. It is about.

In general, in the process of manufacturing a silicon wafer, a polishing process for mirror-mirroring the surface of the silicon wafer (hereinafter referred to as "wafer") is performed. This polishing process is a process of controlling the nanotopography and roughness of the microsurface by performing a mechanical and chemical reaction in order to improve the flatness of the wafer.

The improved flatness of the wafer is due to the requirements for manufacturing highly integrated semiconductor devices in order to reduce production costs and improve product performance in semiconductor processes. In other words, as the design rules of semiconductor devices become smaller and smaller, the flatness specification of wafers required by semiconductor device manufacturers is becoming increasingly strict. Therefore, in order to manufacture a highly integrated semiconductor, securing flatness of the wafer surface has become an essential problem.

As described above, as a method for improving flatness, a double side polishing process (DSP) having excellent flatness of the wafer compared to the single side polishing step is being progressed.

In the double-side polishing process, a double-side polishing apparatus is usually used to polish both sides of a wafer. Here, the two-side polishing device is a four-way type (4-Way type) for rotating the four parts of the upper plate, the lower plate, the sun gear (Internal Gear) and internal gear (Internal Gear) to polish both sides of the wafer, It is divided into an oscillation type for polishing both sides of a wafer by a carrier rotated by a top plate, a bottom plate and a fixed trajectory.

These two types of double side polishing apparatus are made to perform mechanical and chemical polishing, as described above. That is, during polishing of the wafer, a slurry (hereinafter referred to as “polishing liquid”) mixed with abrasive particles and various additives is supplied onto the polishing surface of the wafer. Accordingly, the wafer is mechanically and chemically polished by frictional force due to close rotational motion with the polishing pads attached to the upper and lower plates and the reaction of the polishing liquid.

More specifically, as shown in FIGS. 1 and 2, the four-way type double-side polishing apparatus 10 includes an upper surface 15 attached to a lower surface of the polishing pad 15 ′ and an upper surface 15. ) And a lower surface plate 11 having a polishing pad 11 'attached to the upper surface and a wafer W, which is installed between the upper surface plate 15 and the lower surface plate 11, and is subjected to polishing. Configured to include a carrier 13.

Looking briefly at the operation and structural relationship of the four-way double-sided polishing apparatus 10, an inner gear 12 is provided on the outer circumference of the lower plate 11, and a sun gear is provided at the center of the upper plate. (sun gear) 14 is installed. Gears are formed on the outer circumferential surface of the carrier 13 on which the wafer W is mounted to be engaged with the sun gear 14 and the internal gear 13. Accordingly, the carrier 13 pressurized by the upper plate 15 and the lower plate 11 rotated in opposite directions to each other engages with the internal gear 12 and the sun gear 14 rotated in the opposite directions to revolve and Will rotate.

The thickness variation for each diameter of the wafer W polished through the above process is shown in FIG. 3. That is, as shown in FIG. 3, the shape of the wafer W is secured in a symmetrical shape. It becomes possible. This four-way type double side polishing apparatus 10 is used to polish a wafer W having a diameter of 300 mm.

Next, the assertion type double side polishing apparatus 20 is used to polish the wafer W, which is typically 200 mm in diameter.

More specifically, the assertion type double-sided polishing apparatus 20 is, as shown in Figure 4, the upper plate 25 for rotating and pressing the wafer (W) from the upper side, the opposite direction to the upper plate 25 Carrier which is mounted between the lower platen 21 and the upper plate 25 and the lower platen 21 to rotate and pressurize the wafer W from below. And (23). At this time, polishing pads 25 'and 21' are attached to the lower surface of the upper surface plate 25 and the upper surface of the lower surface plate 21, respectively.

The carrier 23 has a radius larger than the radius of the upper plate 25 and the lower plate 21, and a plurality of mounting holes 23 ′ on which the wafers W are mounted are formed along the circumference. The center of the carrier 23 and the center of the upper plate 25 and the lower plate 21 are positioned at regular intervals apart. Thus, the carrier 23 has an eccentric rotation with a constant eccentricity with respect to the rotation axis of the upper plate 25 and the lower plate 21 while the upper plate 25 and the lower plate 21 rotate about the rotation axis, respectively. do.

In this assertion type double-sided polishing apparatus 20, the top plate 25 and the bottom plate 21 rotate at the same rotation speed as the four-way type double-side polishing apparatus 10, but the carrier ( There is no rotating and revolving of 23 and does not contact the entire upper plate 25 and lower plate 21 to which the polishing pads 25 'and 21' are attached, but as shown in FIG. It is done by exercising only.

In addition, the assertion-type double-sided polishing apparatus 20 can use less abrasive than the 4-way type double-sided polishing apparatus 10, which is advantageous for polishing wafers W having a diameter of 200 mm or less. The simple structure has the advantage of easy equipment operation and maintenance.

However, when the large-diameter wafer W having a diameter of 300 mm is polished using the assertion-type double-sided polishing apparatus 20, it is difficult to uniformly polish the entire wafer W due to the use of a small amount of abrasive. After double-side polishing, the shape of the wafer W is polished in an inclined shape rather than in the form of left and right symmetry. In addition, when the amount of the abrasive used is increased, the removal of defects in the wafer tends to be reduced due to the water film phenomenon, which acts as a cause of deteriorating the overall flatness of the wafer (W).

That is, the amount of change in thickness for each radius of the wafer W in which the wafer W having a diameter of 300 mm is polished by the asserting type double-side polishing apparatus 20 is shown in FIG. 6. As shown in FIG. 6, it can be seen that the wafer W is inclined. Here, 'wafer 1' shown in FIG. 6 is polished using less abrasive, and 'wafer 2' indicates that polishing is performed by increasing the amount of abrasive used.

That is, the currently used assertion-type double-sided polishing apparatus 20 has no rotation and idle of the wafer W during polishing as compared to the four-way type double-sided polishing apparatus 10, and thus rotates only in a predetermined track. A decrease in the contact area between the polishing pads 25 'and 21' and the wafer W is shown. Accordingly, there is a problem in that the wafer W is unevenly polished, so that the inclination of the wafer W occurs after polishing, and the flatness is deteriorated.

In order to solve this problem, it is necessary to modify the assertion-type double-side polishing apparatus 20 to have a structure that rotates and revolves like the 4-way type double-side polishing apparatus 10, but the modification cost is the purchase cost of the double-side polishing apparatus. The problem is that the cost is not effective in terms of cost.

The present invention has been made to solve the above problems, and an object thereof is to provide a wafer carrier having an improved structure of a wafer mounting hole so that the wafer rotates when polishing both sides of the wafer, and a wafer double side polishing apparatus employing the same.

It is still another object of the present invention to provide a wafer carrier capable of smoothly polishing a large diameter wafer using an acceleration type double side polishing apparatus and a wafer double side polishing apparatus employing the same.

In order to achieve the above object, the wafer carrier of the present invention is a wafer carrier formed by penetrating a mounting hole for mounting a wafer for polishing both sides of the wafer, and the diameter of the mounting hole is gradually increased from the top to the bottom of the mounting hole. Characterized in that formed to shrink.

Preferably, the diameter of the top of the mounting hole is 301.5mm or more and 301.6mm or less, and the diameter of the bottom is 300.15mm or more and 300.25mm or less.

Wafer double-side polishing apparatus for achieving the above object, the lower surface plate attached to the polishing pad on the upper surface; An upper plate attached to a lower surface of the upper surface to rotate and pressurize the wafer from the upper surface; And a wafer carrier interposed between the lower plate and the upper plate, the wafer carrier having a mounting hole for receiving and mounting a wafer, wherein the cross section of the mounting hole is formed such that the diameter of the mounting hole is gradually reduced from the top to the bottom. do.

Preferably, the diameter of the top of the mounting hole is 301.5mm or more and 301.6mm or less, and the diameter of the bottom is 300.15mm or more and 300.25mm or less.

The wafer carrier and the wafer double-side polishing apparatus employing the same according to the present invention have the following effects.

First, by changing the structure of the mounting hole of the carrier on which the wafer is mounted, the wafer is rotated to improve flatness.

Second, by using a carrier having an improved structure of the mounting hole in the assertion type double-side polishing apparatus, it is possible to smoothly polish a large diameter wafer having a diameter of 300 mm. Therefore, the cost of improving the structure of the assertion-type double-side polishing apparatus to the structure of the 4-way double-side polishing apparatus can be drastically reduced.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

7 is a cross-sectional view showing a wafer carrier according to a preferred embodiment of the present invention.

The wafer carrier 100 according to the present invention is interposed between the lower plate 21 and the upper plate 25 of the assertion type double-side polishing apparatus 20 shown in FIG. It is for polishing both sides. Since the above-described assertion type double-side polishing apparatus 20 has been described above, a detailed description thereof will be omitted.

Hereinafter, the wafer carrier 100 will be described as being polished by the assertion type double-side polishing apparatus 20. In this case, the diameter of the wafer W mounted on the wafer carrier 100 is 300 mm.

Referring to FIG. 7, the wafer carrier 100 is formed by passing through a mounting hole 110 for mounting a wafer (W).

The cross section of the mounting hole 110 is formed such that the diameter of the mounting hole 110 gradually decreases from the upper end to the lower end. The mounting holes 110 are formed in plural along the circumference of the wafer carrier 100. For example, the wafer carrier 100 is generally mounted with five wafers W at one time, but is not limited thereto. The number of wafers W mounted at one time may be selectively increased or decreased.

More specifically, the diameter of the top of the mounting hole 110 is 301.5mm, the diameter of the bottom is 300.15mm. Here, the tolerance for the diameter of the upper end of the mounting hole 110 is more than 0mm 0.1mm or less. Similarly, the tolerance for the diameter of the lower end of the mounting hole 110 is more than 0mm 0.1mm or less. That is, the diameter of the upper end of the mounting hole 110 is 301.5mm or more and 301.6mm or less, and the diameter of the lower end is 300.15mm or more and 300.25mm or less. In this case, '-0 / + 0.1mm' illustrated in FIG. 7 should be understood to mean 'more than 0 mm and less than 0.1 mm'.

The wafer W mounted in the mounting hole 110 is formed to be spaced apart from the upper end of the mounting hole 110 by a predetermined interval and is supported by the lower end of the mounting hole 110. That is, since the diameter of the lower end of the mounting hole 110 is almost the same as the diameter of the wafer W, the lower side of the wafer W is supported by this effect. Accordingly, when the wafer carrier 100 on which the mounting holes 110 are formed is double-sided, the wafer W is rotated by the upper plate 25.

More specifically, the rotational force of the upper platen 25 is rotated about three times faster than the rotational force of the lower platen 21 and pressurizes the wafer W. That is, the wafer W pressed by the polishing pad 25 ′ of the top plate 25 is smoothly rotated by receiving the rotational force of the top plate 25 while being supported by the lower end of the mounting hole 110. Rotation) occurs.

On the other hand, with respect to the numerical range, if the diameter of the upper end of the mounting hole 110 to which the tolerance range is applied exceeds the upper limit or less than the lower limit, the rotation of the wafer (W) in the mounting hole 110 of the carrier 100 This is not desirable because it does not occur.

In addition, when the diameter of the lower end of the mounting hole 110 to which the tolerance range is applied exceeds the upper limit or falls below the lower limit, the rotation of the wafer W in the mounting hole 110 of the carrier 100 does not occur. Can not do it.

Then, in order to prove that the flatness is improved when the wafer W is polished by the wafer carrier 100 of the present invention as described above, it will be described in comparison with the conventional wafer carrier 23 shown in FIG. do.

Referring to FIG. 8, the mounting hole 23 ′ formed in the wafer carrier 23 has a diameter of 300.15 mm. This wafer carrier 23 was polished under the same conditions as in the embodiment of the present invention. That is, the wafer W having a diameter of 300 mm is mounted on the wafer carrier 23, and the rotational force of the upper platen 25 is rotated about three times faster than the rotational force of the lower platen 21 so that the assertion type polishing device is rotated. Polished at 20. In addition, the tolerance for the mounting hole 23 'was satisfied to satisfy the condition of -0mm / + 0.1mm (more than 0mm and less than 0.1mm).

9 shows the results of measuring the flatness of the polished wafer using the wafer carrier of the present invention and the conventional wafer carrier. The flatness of the wafer indicates the degree of flatness of the wafer. The flatness measurement is performed by Site Backside Reference Indicate Reading (SBIR), Edge sector Site Frontside Reference (Site least square plane) range (ESFQR), and Site Frontside Reference (SFQR). Q (Site Least Square Plane) Range (3)

The SBIR is obtained as the maximum value of the thicknesses measured by dividing the wafer surface into sites of constant size. In this case, '26 * 33 'means that the wafer having a diameter of 300mm is divided by a site of 26mm × 33mm, and E / E 3mm means removing 3mm from the edge of the wafer.

ESFQRs are designed for radially equal sites at constant angles (typically 5 degrees), moving from a point (usually 1 mm or 2 mm) away from the edge of the wafer by a predetermined length (15 mm) toward the center of the wafer. It measures and calculates | requires by the thickness difference of the highest point and the lowest point. In other words, 'R _L = 15mm' means that the process proceeds by 15mm from the portion moved to the center of the wafer. The ESFQR thus calculated usually has a value of nm level.

SFQR represents a local flatness, and the wafer surface is divided into sites of a certain size, and the height of the mountain and the depth of the valley are calculated based on the reference plane of each area. In addition, the SFQR value of the site with the largest SFQR value is represented by the representative SFQR value of the wafer.

The smaller the values represented by the SBIR, ESFQR, and SFQR, the better the flatness.

That is, it can be seen that the conventional wafer flatness value for SBIR is 291 nm, and the wafer flatness value of the present invention is 168 nm. It can also be seen that the conventional wafer flatness value for ESFQR is 268 nm and the wafer flatness value of the present invention is 248 nm. In addition, it can be seen that the conventional wafer flatness value for SFQR is 76 nm, and the wafer flatness value of the present invention is 50 nm. As a result, it can be seen that the flatness value is improved.

On the other hand, as a result of polishing the wafer using the wafer carrier 100 as described above, as shown in FIG. 10, it is possible to secure a stable shape in which the left and right sides of the wafer W are symmetrical.

Unexplained reference numerals 'A', 'B', 'C', 'D', and 'E' indicate the amount of thickness change for each wafer diameter by grinding the respective wafers W. FIG.

As a result, as the level difference between the center section and the edge section of the wafer W is reduced, the flatness of the wafer is improved, thereby improving quality and yield.

Additionally, in order to prove that the wafer carrier 100 according to the present invention does not occur as described above by merely expanding the diameter of the top of the mounting hole 110, the mounting hole 110 according to the present invention. It will be described in comparison with a wafer carrier having an extended mounting hole that is different from the structure of the.

11 and 12, a mounting hole 33 ′ having a diameter of 301.5 mm is formed in the wafer carrier 33 of Comparative Example 1, and a mounting hole 43 ′ is formed in the wafer carrier 43 of Comparative Example 2. The mounting hole 43 is formed so that the diameter of the gradually increases from the top to the bottom. That is, the diameter of the upper end of the mounting hole 43 of the comparative example 2 is 300.15 mm, and the diameter of the lower end is 301.5 mm.

The mounting holes 33 'and 43' of each of the wafer carriers 33 and 43 were made to satisfy the condition that the tolerance was -0 mm / + 0.1 mm (more than 0 mm and less than 0.1 mm).

Hereinafter, in the comparative example, the wafer W was polished under the same conditions as in the embodiment of the present invention. That is, the wafer W having a diameter of 300 mm is mounted on the wafer carriers 33 and 43, and the rotational force of the upper plate ('25' in FIG. 4) is approximately larger than that of the lower plate ('21' in FIG. 4). The wafer W was polished in an assertion type polishing apparatus ('20' of FIG. 4) by rotating at a speed three times faster.

As a result of polishing under the above conditions, in Comparative Example 1, the diameter of the upper end and the lower end of the mounting hole 33 'was expanded, but the rotation of the wafer W occurred almost as in the conventional wafer carrier 23. It was confirmed not to. This is judged to be a result of the adhesion between the polishing pad pressing the wafer W and the wafer W during polishing of the wafer W being stronger than the platen (upper plate and lower plate) rotational force for rotating the wafer W.

In Comparative Example 2, the lower end of the mounting hole 43 'and the wafer W are spaced apart, but the diameter of the upper end of the mounting hole 43' is substantially the same as the diameter of the wafer W. It was confirmed that rotation of W) hardly occurred. This is a result of the upper end of the mounting hole 43 'does not make a space for rotation by supporting the wafer (W).

That is, even when the mounting holes 33 'and 43' on which the wafers W are mounted are expanded or partially expanded, as in Comparative Examples 1 and 2, rotation (rotation) of the wafer W occurs according to the expanded structure. You will not. Thus, as in the mounting hole 110 of the present invention, the diameter of the mounting hole 110 from the upper end to the lower should be formed gradually.

The wafer carrier 100 having the above configuration may be employed and used in the wafer double-side polishing apparatus 20 shown and described with reference to FIG. 4. In addition, it should be understood that the wafer double side polishing apparatus of another configuration can be employed. Therefore, the description of the specific configuration and operation of the polishing apparatus will be omitted.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto, and the technical spirit of the present invention and the following will be understood by those skilled in the art to which the present invention pertains. Various modifications and variations are possible, of course, within the scope of equivalents of the claims to be described.

The present invention will be described in detail with reference to the following drawings, but these drawings illustrate preferred embodiments of the present invention, and the technical concept of the present invention is not limited to the drawings and should not be interpreted.

1 is a side cross-sectional view schematically showing a two-way polishing device of a four-way type.

FIG. 2 is a plan view showing a state in which a wafer is rotated and processed by a four-way double-side polishing apparatus shown in FIG.

Figure 3 is a graph showing the amount of change in thickness for each diameter of the wafer after the wafer is polished by a two-way polishing device of the four-way type.

4 is a perspective view schematically showing a double-side polishing apparatus of the assertion type.

FIG. 5 is a plan view illustrating a state in which a carrier provided in the asserting type double-side polishing apparatus shown in FIG. 1 is rotated in a predetermined trajectory. FIG.

Fig. 6 is a graph showing the thickness change of each wafer after the wafer is polished by the asserting type double-side polishing apparatus.

7 is a sectional view showing a wafer carrier according to a preferred embodiment of the present invention.

8 is a cross-sectional view showing a conventional wafer carrier.

9 is a graph showing a state in which a flatness is compared after polishing a wafer using a conventional carrier and a carrier of the present invention.

10 is a graph showing the thickness change of each wafer diameter after polishing the wafer using the wafer carrier according to the present invention.

11 and 12 are cross-sectional views showing another wafer carrier to be compared with the wafer carrier shown in FIG. 7, respectively.

Claims (4)

In the wafer carrier formed by passing through the mounting holes for mounting the wafer for polishing both sides of the wafer, The cross section of the mounting hole is a wafer carrier, characterized in that the diameter of the mounting hole is gradually reduced from the top to the bottom. The method of claim 1, The diameter of the upper end of the mounting hole is 301.5mm or more and 301.6mm or less, and the diameter of the bottom is 300.15mm or more and 300.25mm or less. A lower plate with an abrasive pad attached to an upper surface thereof; An upper plate attached to a lower surface of the upper surface to rotate and pressurize the wafer from the upper surface; And And a wafer carrier interposed between the lower and upper plates, the wafer carrier having a mounting hole for receiving and mounting the wafer. Cross-section of the mounting hole is a wafer double-side polishing apparatus, characterized in that formed to gradually reduce the diameter of the mounting hole from the top to the bottom. The method of claim 3, The diameter of the upper end of the mounting hole is 301.5mm or more and 301.6mm or less, the diameter of the bottom is 300.15mm or more 300.25mm or less wafer, characterized in that.

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