CN100537149C - Polishing pad and chemical mechanical polishing method - Google Patents

Abstract

The invention provides a polishing pad, the polishing surface of the polishing pad has a plane area and a concave-convex area, the plane area is a flat surface with a roughness less than 20 μm, and is used for polishing wafers, and the concave-convex area has grooves and holes Or a combination of them, used to lift the wafer from the polished surface after polishing. Adopting the polishing pad provided by the present invention can make the wafer after chemical mechanical polishing have higher surface smoothness. After polishing, the wafer is moved to the concave-convex area of the polishing pad, and the wafer can be easily pulled out from the surface of the polishing pad. out.

Description

Polishing pad and chemical mechanical polishing method

technical field

The invention relates to a semiconductor chemical mechanical polishing process, in particular to a chemical mechanical polishing pad and a chemical mechanical polishing method for high flatness of the wafer surface.

Background technique

The chemical mechanical polishing (CMP) process was introduced into the integrated circuit manufacturing industry by IBM in 1984, and was first used in the planarization of the intermetallic insulating dielectric (IMD) in the subsequent process, and then used for tungsten (W) through the improvement of equipment and processes. planarization for shallow trench isolation (STI) and copper (Cu) planarization. Chemical Mechanical Polishing (CMP) is the fastest growing and most important technology in IC manufacturing process in recent years.

The CMP polishing process uses mechanical force to act on the surface of the wafer in the atmospheric environment of the clean room, and generates power to break and corrode the film layer on the surface of the wafer, and the polishing process must rely on the chemical substances in the polishing solution. Interacts with thin film layers to increase their etching efficiency. The two most important components in the CMP process are the slurry and the pad. Polishing fluid is usually made by dispersing some very fine oxide powders in aqueous solution. Polishing pads are mostly made of foamed porous polyurethane. In the CMP process, the polishing liquid is first filled in the gap of the polishing pad, and high-speed conditions are provided to allow the wafer to interact with the particles in the polishing pad and the polishing liquid under high-speed rotation, while controlling the downward pressure. parameters such as pressure.

The Chinese patent with the application number CN01814133 discloses a structure of a polishing pad, which has a polishing surface, which is a surface in direct contact with a wafer during chemical mechanical polishing. The polishing surface of the polishing pad has a three-dimensional structure, and the three-dimensional structure includes many regularly arranged three-dimensional elements with a predetermined shape, and the shape of a single three-dimensional element can be any one of various geometric solids, adjacent There are recesses between the three-dimensional elements. The three-dimensional element shown in FIG. 1 is a pyramid shape with a flat top surface formed by truncating the top to a predetermined height. The Chinese patent application number CN03140681 discloses another structure of a polishing pad, which has a recess formed on the side of the polishing surface and selected from at least one shape of lattice, ring and spiral. The pad can also be a concave part in one or more of a grid shape, a ring shape or a spiral shape, or a through hole running through the surface of the polishing pad. As shown in FIG. 2 , the polishing pad structure has a concentric circular concave structure on the polishing surface. At present, most of the polishing pads used in the chemical mechanical polishing process have the above-mentioned three-dimensional structure or a polishing surface with grid-shaped, ring-shaped and spiral concave parts. The polishing pad with this structure can better disperse the polishing liquid. However, since the polishing surfaces of these polishing pads all have recesses, chemical mechanical polishing will leave recesses similar to the structure of the polishing surface on the wafer surface, reducing the flatness of the wafer surface.

Practice has shown that for conventional semiconductor devices, the surface of the wafer is chemically mechanically polished with a polishing pad whose polishing surface is a concentric ring or a three-dimensional element of a predetermined shape, and the flatness of the wafer surface can meet the application requirements of the device. However, for some wafers used in optical instruments, such as wafers used in image transmission and image processing components, and products that require high wafer surface quality, due to particularly high requirements for wafer surface flatness, using this Most of the flatness of the wafer surface obtained by chemical mechanical polishing with a polishing pad with recesses cannot meet the application requirements of the device, and the product yield is very low. For example, using a chemical-mechanical polished wafer with an existing polishing pad for an image transmission device of a liquid crystal display may cause the surface of the liquid crystal display to look like stripes, which is due to the color difference caused by the unevenness of the wafer surface after chemical mechanical polishing. LCD surface results.

In order to obtain a better flatness of the wafer surface, the wafer used for image transmission cannot be treated by chemical mechanical polishing. Therefore, most of them are treated by chemical etching. However, the surface roughness of the wafer treated by this method is much greater than that of the surface treated by chemical mechanical polishing, and there will be oxide residues in some areas; the local flatness is not as good as that of chemical mechanical polishing. s surface.

If use the polishing pad that does not have the groove described in the Chinese patent of CN01814133 and CN03140681 to carry out chemical mechanical polishing on the surface, promptly use the polishing pad with flat surface to directly carry out chemical mechanical polishing, although can overcome wafer surface flatness can not satisfy Defects required, however, after chemical mechanical polishing using a polishing pad with a flat surface, the surface of the wafer and the polishing surface of the polishing pad are relatively flat, so the wafer and the polishing pad are tightly bonded, and it is difficult to pull the wafer out of the surface of the polishing pad .

Contents of the invention

The problem to be solved by the present invention is that the surface of the wafer polished by the polishing pad in the prior art cannot meet the application requirements of optical devices for image transmission and products with higher requirements on the surface quality of the wafer, while the existing flat surface After the polishing pad is polished, the wafer is difficult to pull out from the polishing surface.

In order to solve the above problems, the invention provides a polishing pad with a planar area and a concave-convex area on the polishing surface of the polishing pad, and the planar area is a flat surface with a roughness less than 20um for polishing wafers. The region has grooves, holes or a combination thereof for pulling the wafer from the polishing surface after polishing.

Further, the planar area surrounds the concave-convex area, and the geometric center of the concave-convex area coincides with the geometric center of the polishing surface. Further, the distance between any point on the outer contour of the concave-convex area and the geometric center of the polishing surface is 20.5 of the diameter of the polished wafer. % to 40%.

Furthermore, the distance between any two points on the inner and outer contour lines of the plane area is greater than 120% of the diameter of the polished wafer. Preferably, the shortest distance between any point on the inner contour line of the plane area and the outer contour line of the plane area Greater than 120% of the diameter of the polished wafer and less than or equal to 150% of the diameter of the polished wafer.

As an optimized technical solution, the concave-convex area and the polishing surface are distributed in a concentric circle, and the planar area is an annular area formed by removing the concave-convex area from the polishing surface. Wherein, the diameter of the polished surface is D ₁ , and 457.2mm≤D ₁ ≤711.2mm; the diameter of the concave-convex area is D ₂ , and 76.2mm≤D ₂ ≤152.4mm.

Wherein, the concave-convex area has more than two grooves, holes, or combinations thereof, and the arrangement of the grooves, holes, or combinations thereof in the concave-convex area is uniform or non-uniform.

Wherein, the groove in the concave-convex area is a single grid shape, ring shape, XY grid shape, spoke shape, spiral shape, or a combination of any two or more shapes, and the groove has a required width, depth and length.

Wherein, the cross-sectional shape of the hole in the concave-convex area is a single circle, ellipse, polygon, or a combination of any two or more shapes, and the hole has a required depth and cross-sectional area.

Optimally, the concavo-convex area has several annular grooves arranged in a concentric ring, wherein the distance between the annular grooves is 0.1 mm to 2 mm.

The width of the annular groove is 0.15mm-0.5mm, the depth of the groove is 0.25mm-0.5mm, and the minimum length between adjacent grooves is 0.1mm-10mm.

Optimally, the concavo-convex area has a number of circular holes arranged in concentric rings, the diameter of the holes is 5 mm to 12 mm, and the distance between the concentric rings is 0.1 mm to 2 mm.

Optimally, the concavo-convex area has several circular holes arranged in concentric rings and several circular holes arranged in concentric rings, and the distance between the concentric rings is 0.1 mm to 2 mm.

Furthermore, the polishing pad also has a lining layer arranged on the non-polishing surface.

Compared with the prior art, the present invention has the following advantages:

1. The polishing surface of the polishing pad provided by the present invention has a planar area and a concave-convex area. The flat area is a flat surface with a roughness less than 20um for polishing wafers. The concave-convex area has grooves, holes or a combination thereof for polishing after Pull the wafer off the polished surface. Using the planar area of the polishing pad during chemical mechanical polishing overcomes the defect that the wafer surface flatness caused by the polishing pad with grooves in the prior art is not high, and can make the wafer after chemical mechanical polishing have better High surface flatness can meet the needs of optical devices for image transmission and products with higher requirements on the surface quality of the wafer. After polishing, move the wafer to the concave-convex area of the polishing pad, and the wafer can be easily removed from the polishing pad. The surface of the pad is pulled out.

2. The distance between any point on the outer edge of the concave-convex area of the polishing pad provided by the present invention is 38.1 mm to 76.2 mm from the geometric center of the polishing surface, which can not only effectively ensure the area of the plane area for chemical mechanical polishing, but also prevent the crystal The circle enters the concave-convex area during the polishing process, and after polishing, it can also ensure that the wafer can be easily pulled out from the polishing pad after moving to the concave-convex area.

3. Set the concave-convex area, flat area and polishing surface of the polishing pad into the shape of concentric rings, and the grooves, holes and their combinations in the concave-convex area are also set into the shape of concentric rings, which can ensure that the wafer is polished during the polishing process. Will not go into bumpy areas.

4. The diameter of the hole contained in the concave-convex area is set at 5 mm to 12 mm, so that there is enough space in the concave-convex area, so that the wafer can be easily pulled out from the polishing pad after moving to the concave-convex area.

5. By adopting the polishing pad and the polishing method of the present invention, the yield rate of the chemical mechanical wafer polishing process is improved. The chromatic aberration caused by the roughness of the wafer surface after polishing using the existing polishing pad and chemical mechanical polishing method will lead to a 40% to 80% drop in the yield rate. After polishing with the polishing pad and the polishing method of the present invention, the yield rate has increased by 40% % to 80%.

6. Compared with the wafer surface roughness of the chemical etching process, the wafer surface polished by the polishing pad of the present invention and the polishing method is lower than 10 nanometers, so the wafer surface has higher surface reflectivity and Better optoelectronic properties.

Description of drawings

Fig. 1 is the structural representation of the polishing pad of the pyramidal shape of existing polishing surface;

Fig. 2 is a schematic structural view of a polishing pad whose polishing surface is a concentric annular recess;

Fig. 3 is the microtopography figure of soft polishing pad surface in the prior art;

Figure 4 is a topographical view of the wafer surface after chemical mechanical polishing using a polishing pad with a concave portion;

5 is a schematic diagram of the three-dimensional state of the wafer surface after chemical mechanical polishing using a polishing pad with a concave portion;

Figure 6 is a topographical view of the wafer surface after chemical mechanical polishing using a polishing pad with a concave portion;

7 to 9 are schematic structural views of the polishing surface in the preferred embodiment provided by the present invention;

FIG. 10 is a topographical view of the wafer surface after the chemical mechanical polishing method provided by the present invention is polished;

Fig. 11 is a comparison of the occurrence rate of wafer defects after chemical mechanical polishing with the polishing pad used in the prior art and the present invention.

Detailed ways

The specific implementation of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The polishing pads currently used in the chemical mechanical polishing process are all polishing pads with grooves on the polishing surface. After polishing the wafer with a polishing pad with grooves on the polishing surface, the flatness of the wafer surface cannot be applied to the device used for image transmission. In order to obtain a better flatness on the wafer surface, the present invention studies the reasons for the concaves on the wafer surface after chemical mechanical polishing. The polishing pad with the concave portion on the polishing surface was observed through an electron microscope, and it was found that the microstructure of the concave portion on the polishing surface is shown in FIG. 3 , and the concave portion can be clearly seen from the figure.

After the wafer is chemically mechanically polished with a polishing pad having a polishing surface as shown in Figure 2, the surface morphology of the wafer is found to be concentric rings as shown in Figure 4 by irradiation with polarized light, and The concentric rings on the wafer also had recesses that matched the shape of the polishing pad recesses. Fig. 4 is the surface morphology of a wafer illuminated by polarized light taken by a digital camera.

Fig. 5 is a three-dimensional view of the concentric rings on the wafer surface after chemical mechanical polishing, from which the concentric rings on the wafer surface and the concavities on the concentric rings can be seen more intuitively.

The present invention analyzes and researches the size of the various types of polishing pad grooves commonly used in semiconductor manufacturing and the wafer surface groove width after polishing, and the results are as shown in Table 1. The width of each concentric ring on the wafer surface after polishing Exactly the same width as the concentric rings on the polishing surface of the polishing pad being used. The width of each ring of the polishing pad is the sum of the widths of the grooved portion and the non-grooved portion, and the width of each concentric ring on the wafer surface is also the sum of the widths of the grooved portion and the non-grooved portion.

Table 1 Comparison of the width of each ring of different polishing pads and the width of each ring on the polished wafer surface

Polishing pad model The width of each ring of the polishing pad The width of each ring on the wafer surface IC1010 polishing pad (LAM polishing machine) 1.4mm 1.4mm IC1010 polishing pad (MIRRAMESA polishing machine) 3mm 3mm Politex reg polishing pad (MIRRAMESA polishing machine table) 2.5mm 2.5mm

The IC1010 polishing pad (LAM polishing machine) in Table 1 refers to the IC1010 hard polishing pad produced by Rohmhass (Rohmhass) assembled on the polishing machine produced by Lam Technology Co., Ltd. (LAM).

The IC1010 polishing pad (MIRRA MESA polishing machine) in Table 1 refers to the MIRRA MESA polishing machine produced by American Applied Materials (AMAT) equipped with the IC1010 hard polishing pad produced by Rohmhass (Rohmhass).

The Politex reg polishing pad (MIRRA MESA polishing machine) in Table 1 refers to the MIRRA MESA polishing machine produced by American Applied Materials (AMAT) equipped with the Politex reg soft polishing pad produced by Rohmhass (Rohmhass).

，如图6所示。Further studies have found that the concave portion produced on the wafer surface after chemical mechanical polishing is exactly the same shape and width as the concave portion on the polishing surface of the polishing pad used, and the height difference between the concave portion and the highest point on the wafer surface is 50 to 200

,As shown in Figure 6.

In view of the above-mentioned research, in order to obtain a flatter wafer surface, the invention provides a polishing pad, the polishing surface of the polishing pad has a planar region and a concave-convex region, and the planar region is a flat surface with a roughness less than 20um. For polishing a wafer, the concave-convex area has grooves, holes or a combination thereof for pulling the wafer from the polishing surface after polishing.

Further, the planar area surrounds the concave-convex area, and the geometric center of the concave-convex area coincides with the geometric center of the polishing surface. Further, the distance between any point on the outer contour of the concave-convex area and the geometric center of the polishing surface is 20.5 of the diameter of the polished wafer. % to 40%, since the plane area is used to polish the wafer, the area of the plane area should at least ensure that the wafer will not enter the concave-convex area when polishing the wafer.

Furthermore, the concave-convex area and the polishing surface are distributed in a concentric circle, the plane area is a circular area formed by removing the polishing surface from the concave-convex area, and the distance between any point on the outer contour of the concave-convex area and the geometric center of the polishing surface is 20.5 times the diameter of the polished wafer. % to 40%, the area of the plane area should at least ensure that the wafer will not enter the concave-convex area when polishing the wafer, therefore, the distance between any two points on the inner and outer contour lines of the plane area is greater than 120% of the diameter of the polished wafer, It is preferably greater than 120% of the diameter of the polished wafer and less than or equal to 150% of the diameter of the polished wafer.

As a more preferred technical solution, in the present invention, the diameter of the polished surface is set to D ₁ , and the diameter of the concave-convex area is D ₂ , then 76.2mm≤D ₂ ≤152.4mm, and 457.2mm≤D ₁ ≤711.2mm. The planar region of the polishing pad of the present invention has a flat surface, and the roughness of the flat surface is less than 20um. When performing chemical mechanical polishing, the wafer is mainly polished by the planar region, which can obtain high flatness and can be used for Wafer surface for optics.

When using a polishing pad with a flat polishing surface for chemical mechanical polishing, since the contact surface between the polishing surface and the wafer is very flat, the contact surface is tightly bonded. After the chemical mechanical polishing is completed, the wafer cannot be lifted from the polishing pad in the flat area. Pull out, in order to make the wafer easier to pull out from the surface of the polishing pad, after polishing, a part of the wafer can be rotated to the concave-convex area of the polishing pad, because the concave-convex area has grooves, holes or their combination, the wafer can be pulled out. Air is filled between the surfaces where the circle and the polishing pad are in full contact to reduce the pressure difference between the upper and lower surfaces of the wafer, so that the wafer can be pulled out from the surface of the polishing pad more easily.

The flat polishing surface in the present invention means that the polishing surface does not have grooves, holes, combinations thereof and any other uneven surface structures.

The concavo-convex area of the present invention has grooves, holes or their combination. The number of grooves, holes or combinations thereof contained in the concavo-convex area can be set as required, preferably the number of grooves, holes or combinations thereof is more than two.

The arrangement of grooves, holes or their combinations in the concave-convex area is not too demanding, and can be arranged regularly or irregularly. It is more preferable that the arrangement of grooves, holes or their combination in the entire concave-convex area is uniform, for example, a plurality of grooves are arranged in a regular circle or ellipse in the concave-convex area. Another example is that a plurality of holes are randomly and evenly distributed in the concave-convex area, such as arranged in regular quadrangles, pentagons, hexagons, etc., or arranged in regular ellipse, circular ring and other shapes. Another example is that multiple grooves and multiple holes are evenly distributed in the concave-convex area.

Because the effect of the concave-convex area of the present invention is to make the wafer be pulled out from the surface of the polishing pad easily after polishing, without affecting the flatness of the wafer surface, therefore, as long as the concave-convex area of the polishing pad provided by the present invention exists Air can enter the concave region to reduce the pressure difference between the upper and lower surfaces of the wafer, and the roughness of the convex surface should be the same as that of the polishing pad in the prior art.

The grooves contained in the above-mentioned concave-convex area can be selected from the shape of grid, ring, XY grid, spoke or spiral, and the grooves in the concave-convex area can be a separate grid, ring, XY grid Grid shape, spoke shape or spiral shape, also can be any combination of two or three shapes. The more preferred shape of the present invention is a concave-convex area formed by a single annular groove.

When the groove included in the concave-convex area is annular, its planar shape is not particularly limited, for example, it may be circular, polygonal (triangular, quadrangular, pentagonal), oval, etc. More preferably, the plurality of grooves contained in the concave-convex area are arranged in an annular shape, and more preferably, the plurality of grooves are arranged in a concentric annular shape.

The present invention has no special limitation on the cross-sectional shape in the width direction of the groove contained in the concave-convex area. On the one hand, the cross-sectional shape can be made into a shape formed by a flat side surface and a bottom surface, wherein the width of the opening side of the groove is the same as the bottom side of the groove. The widths can be the same or different, for example, the width of the opening side is larger than that of the bottom side, or the width of the bottom side is larger than that of the opening side.

According to the present invention, the width and depth of the grooves contained in the concave-convex area can be set as required, and the widths and depths of multiple different grooves contained in the concave-convex area can be the same or different.

In the present invention, the width of the groove is preferably at least 0.1 mm, more preferably 0.1 mm to 5 mm, particularly preferably 0.2 mm to 3 mm, and most preferably 0.15 mm to 0.5 mm. The depth of the groove is preferably 0.1 mm or more, more preferably 0.1 mm to 2.5 mm, particularly preferably 0.2 mm to 2.0 mm, most preferably 0.25 mm to 0.5 mm. In addition, the minimum length between adjacent grooves is preferably 0.05 mm or more, more preferably 0.05 mm to 100 mm, particularly preferably 0.1 mm to 10 mm.

That is to say, in the present invention, in the concave-convex area of the same polishing surface, the concave-convex area is set to have more than two grooves, and the plurality of grooves can be randomly arranged in the concave-convex area, and can also be evenly arranged into a regular pattern. The shape and the distance between the grooves can be the same or different, and the width and depth of multiple different grooves can be the same or different. The cross-sectional shapes of different grooves in the groove width direction may be the same or different.

In a preferred technical solution of the present invention: the concave-convex area has more than two grooves, the shape of the groove is annular, and a plurality of grooves are also distributed into a regular ring in the concave-convex area, and each different groove is in the groove width direction. The bottom cross-sectional shape is the same, and the width at the opening side of the groove is the same as the width at the bottom side of the groove, the width between the grooves is the same, and the width and depth of each groove are also the same. The specific numerical values of the width and depth of the grooves can be set according to needs within the numerical range given in the present invention, and there is no excessive limitation here. Adopting this preferred technical solution can simplify the manufacturing process of the polishing pad and reduce the cost.

In a most preferred embodiment, as shown in Figure 7, use circular polishing pad, concave-convex area 11 is a circular area, and becomes concentric distribution with the polishing surface of polishing pad, and planar area 12 removes concave-convex area for polishing surface The ring formed by 11, set the diameter of the polishing surface as D ₁ , then D ₁ can be set according to the size of the polishing equipment and the polished wafer. The fixed value is 508mm, 609.6mm, etc., and the diameter of the concave-convex area 11 is set to _D2 , then _{76.2mm≤D2≤152.4mm} , and the specific values set in the embodiment are 76.2mm, 101.6mm, 127mm, 152.4mm wait. The concavo-convex area sets more than two concentric circular grooves 13 as required (the two concentric circular grooves shown in the figure are only for illustration, and the actual number is set according to different needs. The present invention does not wish to do too much limitation to this), the cross-sectional shape of the groove 13 is circular, and the diameter difference between adjacent concentric rings is the same, this diameter difference can be according to the size of the polishing pad and the area of the plane region and the size of the concave-convex area, which is more common between 0.1mm and 2mm. The width and the depth of the groove 13 are also set according to the needs, the present invention does not wish to do too much limitation to this, but, as a specific embodiment, the present invention sets its width to be 0.15mm to 0.5mm, and the depth is 0.25mm to 0.5mm.

The holes contained in the above-mentioned concave-convex area can have various cross-sectional shapes, and the cross-sectional shapes can be various regular shapes, such as circles, ovals, polygons (triangles, quadrangles, pentagons, hexagons), etc. It can be other various irregular graphics. The hole in the concavo-convex area can be a single circular, elliptical, polygonal or other irregular shape, or a combination of any two or three of the above-mentioned various shapes of holes.

A plurality of holes can be arranged in a regular shape or an irregular shape in the concave-convex area. The present invention hopes that it is better that a plurality of holes are more evenly distributed in the concave-convex area, and it is better that each different hole is arranged in a shape such as a ring, a polygon, and a spiral in the concave-convex area, and it is better that a plurality of holes are arranged in the concave-convex area. They are arranged in circular rings, and the distance between each ring is set according to needs, which can be the same or different. The most preferred method of the present invention is that a plurality of holes are arranged in the shape of concentric circles in the concavo-convex area, the distance between each concentric circle, that is, the radius difference between two adjacent concentric circles is the same, each of the concentric circles is formed The distance between the holes can be adjusted as needed.

In the direction of the depth of the hole, the cross-sections of holes with different depths can be the same or different, for example: the three-dimensional shape of the hole can be a cylinder, or a cone and other three-sided or four-sided cylinders. In the present invention, it is more preferable that the cross-sections of the holes with different depths are the same, and it is more preferable to form a circular hole, and the sizes of the cross-sections of the holes with different depths are the same.

According to the present invention, the width and depth of the holes contained in the concave-convex area can be set as required, and the widths and depths of multiple different holes contained in the concave-convex area can be the same or different.

In order to make the polished wafer easier to pull up from the polishing pad, and not to cause waste of the polishing liquid entering the hole, and not to block the hole, the diameter of a single hole is set at 5 mm to 12 mm, preferably 6 mm to 10 mm, More preferably between 8mm and 9mm.

In the present invention, when the concave-convex area contains multiple holes, we hope that the holes are relatively evenly distributed in each area of the concave-convex area, that is, when most of the area of the wafer is rotated to any area of the concave-convex area , the concave-convex area in contact with the wafer should be distributed with multiple holes, so that the wafer can be pulled out from the polishing surface smoothly, and the arrangement shape of the multiple holes in the concave-convex area should not be restricted too much. Preferably, a plurality of holes are arranged in a plurality of circular rings in the concave-convex area, and the spacing of different circular rings can be adjusted according to needs, and the spacing between different circular rings can be the same or different. The depth and width of the holes are also the same.

And a preferred technical scheme of the present invention is that a plurality of holes in the concavo-convex area are arranged in concentric rings, and the diameter difference between adjacent two concentric rings is set to be the same, and the width and depth of each hole are also are set to be the same respectively.

In a more preferred embodiment, a circular polishing pad is used, the concave-convex area is a circular area, and is concentrically distributed with the polishing surface of the polishing pad, the planar area is the ring formed by removing the concave-convex area from the polishing surface, and the concave-convex area has a shape composed of A plurality of holes are evenly arranged to form concentric rings, and the concentric ring formed by arranging the plurality of holes in the concave-convex area is concentrically distributed with the plane area.

In a most preferred embodiment, as shown in Figure 8, use circular polishing pad, concave-convex area 21 is circular area, and becomes concentric distribution with the polishing surface of polishing pad, and planar area 22 removes concave-convex area for polishing surface The ring formed by 21, set the diameter of the polishing surface to be D ₁ , then D ₁ can be set according to the size of the polishing equipment and the polished wafer. The fixed value is 508mm, 609.6mm, etc., and the diameter of the concave-convex area 21 is set to _D2 , then _{76.2mm≤D2≤152.4mm} , and the specific values set in the embodiment are 76.2mm, 101.6mm, 127mm, 152.4mm wait. The concave-convex area contains several holes 23, and the holes 23 are evenly arranged to form more than two concentrically distributed rings. The distance between the formed rings can be set according to the needs. The two rings in the figure are only schematic representations. , the number of rings formed by the hole 23 is not limited to two. The spacing between different rings is set according to the size of the polishing pad, the area of the plane area and the area of the concave-convex area, and is more commonly between 0.1mm and 2mm. The distance between the holes can be adjusted as required, which is not intended to be too limited in this embodiment. The cross-section of a single hole is circular, the diameter is set at 5 mm to 12 mm, and the depth of the hole is set according to needs.

Referring to Fig. 9, it is another specific embodiment of the present invention, using a circular polishing pad, the concave-convex area 31 is a circular area, and is concentrically distributed with the polishing surface of the polishing pad, and the flat area 32 is the polishing surface to remove the concave-convex area 31 For the formed ring, set the diameter of the polishing surface to D1, then D1 can be set according to the size of the polishing equipment and the polished wafer. Generally speaking, it is set to 457.2mm to 711.2mm, and the more common setting value is 508mm, 609.6mm, etc., if the diameter of the concave-convex area 31 is set to D2, then 76.2mm≤D2≤152.4mm, the specific values set in the embodiment are 76.2mm, 101.6mm, 127mm, 152.4mm, etc.

Referring to Fig. 9, the concave-convex area 31 is formed by a circular groove 33 with a cross-sectional shape and a circle formed by a plurality of holes 34, and the circular groove 33 and a circle formed by a plurality of holes 34 Concentrically distributed, the number of circular grooves 33 and circles formed by a plurality of holes 34 can be set according to needs, and is not limited to the number in the figure. The distance between the annular groove 33 and the circle formed by the plurality of holes 34 can be set as required, and is not limited here. The width and depth of groove 33 are also set according to needs, and the present invention does not wish to do too much limitation to this, but, as a specific embodiment, the present invention sets its width to be 0.15mm to 0.5mm, and depth is 0.25mm to 0.5mm. The cross-sectional shape of the hole 34 is circular, and the diameter of a single hole is set at 5 mm to 12 mm. The depth of the hole is set as required, and the distance between the holes can also be adjusted as required. This is too restrictive.

The polishing pad of the present invention can be a hard polishing pad or a soft polishing pad. Since the planar area is mainly used for chemical mechanical polishing, in order to make the dispersion ability of the polishing liquid on the polishing pad better during chemical mechanical polishing, the present invention preferably adopts a soft polishing pad. polishing pad.

The present invention has no special requirements on the material of the polishing pad provided, and is applicable to all polishing pads and polishing surface materials in the prior art. More preferably, the polishing surface is made of foamed porous polyurethane.

The polishing pad can be a multi-layer polishing pad, that is to say, the polishing pad can also have a lining layer arranged on the non-polishing surface. The material and structure of the liner on the non-polishing surface are exactly the same as those of the multi-layer polishing pad in the prior art, which belongs to the prior art and will not be described in detail here.

When the concave-convex area of the polishing surface contains holes, in order to make the polishing liquid can not leak from the holes, it must be ensured that the holes will not penetrate the entire polishing pad, and the polishing pad must be set to a multi-layer polishing pad. Lining on the surface.

When using the above-mentioned polishing pad for polishing, since the polishing surface is a flat structure, in the chemical mechanical polishing, the unevenness of the wafer surface caused by the unevenness of the concave portion in the prior art will not occur, so a wafer with high flatness can be obtained. Round surface, after polishing, a part of the wafer can be rotated to the concave-convex area of the polishing pad, and the wafer can be easily pulled out from the polishing surface, avoiding the difficulty of polishing the wafer when simply using a polishing pad without grooves on the surface Face pull-out defect.

The present invention also proposes a new chemical mechanical polishing method. The key to polishing is to use the polishing pad of the present invention for polishing. The entire polishing process is completed in two steps. First, the wafer is polished on the plane area of the polishing surface. , and then, move the polishing pad to the concave-convex area of the polishing surface, and pull out the wafer from the polishing surface.

In the chemical mechanical polishing method mentioned above, when the polishing pad is moved to the concave-convex area of the polishing surface, the minimum distance from any point on the wafer to the edge of the polishing pad should be 12.7mm to 25.4mm to prevent the rough edge profile of the polishing pad from scratching the wafer surface.

After polishing using the polishing pad of the present invention and the chemical mechanical polishing method, the surface microstructure of the wafer is as shown in Figure 10. After polishing, the concentric rings caused by the polishing pad with concave portions on the wafer surface are eliminated. , the surface of the wafer is uniform and flat, and the roughness is less than 10nm. The above flatness of the wafer surface satisfies the application requirements of optical devices for image transmission.

With reference to shown in accompanying drawing 11, for adopting the polishing pad provided by the present invention to carry out the defect occurrence rate of the wafer after chemical mechanical polishing and adopting the polishing pad with groove in the prior art polishing surface to carry out the comparison of the defect incidence rate of the wafer after polishing , it can be seen from the figure that the defect occurrence rate of the prior art is 30% to 40%, and the defect occurrence rate of the wafer can be reduced to zero after chemical mechanical polishing is carried out by using the polishing pad provided by the present invention.

Although the present invention has been disclosed above with preferred embodiments, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention should be based on the scope defined in the claims.

Claims (20)

1. A polishing pad, characterized in that, the polishing surface of the polishing pad has a planar area and a concave-convex area, and the planar area is a flat surface with a roughness less than 20um for polishing a wafer, and the concave-convex area has Slots, holes, or a combination thereof, used to lift the wafer from the polished surface after polishing. 2. The polishing pad according to claim 1, wherein the planar area surrounds the concave-convex area, and the geometric center of the concave-convex area coincides with the geometric center of the polishing surface. 3. The polishing pad according to claim 2, wherein the distance between any point on the outer contour of the concave-convex area and the geometric center of the polishing surface is 20.5% to 40% of the diameter of the polished wafer. 4. The polishing pad according to claim 1, wherein the distance between any two points on the inner and outer contour lines of the planar area is greater than 120% of the diameter of the polished wafer. 5. The polishing pad according to claim 4, characterized in that, the shortest distance from any point on the inner contour line of the plane area to the outer contour line of the plane area is greater than 120% of the diameter of the polished wafer and less than or equal to the polished wafer 150% of the diameter. 6. The polishing pad according to claim 1, wherein the concave-convex area is concentrically distributed with the polishing surface, and the planar area is an annular area formed by removing the concave-convex area from the polishing surface. 7. The polishing pad according to claim 6, wherein the diameter of the polishing surface is D ₁ , and 457.2mm≤D ₁ ≤711.2mm; the diameter of the concave-convex area is D ₂ , and 76.2mm≤D ₂ ≤152.4 mm. 8. The polishing pad according to claim 1, wherein the concave-convex area has more than two grooves, holes or combinations thereof. 9. The polishing pad according to any one of claims 1 to 8, characterized in that the grooves in the concave-convex area are in the shape of individual grids, rings, XY grids, spokes, spirals, or any of them A combination of two or more shapes. 10. The polishing pad according to any one of claims 1 to 8, characterized in that the cross-sectional shape of the hole in the concave-convex area is a single circle, ellipse, polygon, or any two or more of them The combination. 11. The polishing pad according to any one of claims 1 to 8, characterized in that the concave-convex area has a plurality of annular grooves arranged in a concentric circle. 12. The polishing pad according to claim 11, wherein the distance between the annular grooves is 0.1 mm to 2 mm. 13. The polishing pad according to claim 11, wherein the width of the grooves is 0.15mm-0.5mm, the depth of the grooves is 0.25mm-0.5mm, and the minimum length between adjacent grooves is 0.1mm-10mm. 14. The polishing pad according to any one of claims 1 to 8, wherein the concave-convex area has a plurality of circular holes arranged in a concentric ring. 15. The polishing pad according to claim 14, wherein the diameter of the holes is 5mm-12mm. 16. The polishing pad of claim 14, wherein the spacing between the concentric rings is 0.1 mm to 2 mm. 17. The polishing pad according to any one of claims 1 to 8, characterized in that the concave-convex area has a number of circular holes arranged in a concentric ring and a number of annular grooves arranged in a concentric ring . 18. The polishing pad of claim 17, wherein the spacing between the concentric rings is 0.1 mm to 2 mm. 19. The polishing pad according to any one of claims 1 to 8, characterized in that, the polishing pad further has a lining layer provided on the non-polishing surface. 20. A chemical mechanical polishing method, characterized in that, using the polishing pad according to any one of claims 1 to 19, first using the planar area of the polishing pad to chemically mechanically polish the wafer, and then polishing the wafer Move to the concave-convex area and pull out the wafer.

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