KR20010017439A - Chemical mechanical polishing apparatus - Google Patents

Abstract

PURPOSE: A chemical mechanical polishing(CMP) apparatus is provided to uniformly perform a polishing process regarding the entire surface of a wafer, by forcibly controlling a height of a central portion of the wafer or edge portion of the wafer when the height of the central and edge portions of the wafer are not the same. CONSTITUTION: A wafer absorbing pad(121) is installed on a polishing table, and a recess part(121a) of a predetermined shape is formed on the wafer absorbing pad. A plurality of holes having a predetermined pattern is formed in a base surface of the recess part. A cover plate(122) seals the recess part. A sealing ring(126) is intervened between the cover plate and the recess part so that the holes are divided into a plurality of independent regions. Pipes are coupled to the respective regions. A vacuum pressure generating unit and a gas supplying unit are connected in parallel to the respective pipes. A wafer(101) polished by a wafer chuck is temporarily transferred to a wafer stage. A slurry eliminating unit eliminates slurry on the wafer of the wafer stage. A wafer cleaning unit cleans the wafer whose slurry is removed in the slurry eliminating unit.

Description

Chemical mechanical polishing apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical mechanical polishing (CMP) apparatus, and more particularly, a profile at a center portion and an edge portion of a wafer polished by a chemical mechanical polishing apparatus is not uniform due to various causes. If not, the present invention relates to a chemical mechanical polishing apparatus that can correct this.

Generally, a semiconductor chip consists of an arrangement of devices with conductive terminals interconnected by a metal wiring pattern. Especially in very large scale integrated (VLSI) chips, these metal wiring patterns form wiring layers in multiple layers, and each wiring layer is insulated from other conductive layers by an interlayer insulating film and penetrates the interlayer insulating film when it is necessary to electrically connect different wiring layers. Via holes are formed to interconnect each wiring layer.

In recent years, as the size of the VLSI chip becomes smaller and the number of wiring layers increases, irregularities in any one of the wiring layers are transferred to the next wiring layer, resulting in irregular irregularities on the surface of the wiring layer. These unevennesses lower the uniformity of the wiring layer toward the top of the wiring layer.

For this reason, severe unevenness has caused a need for planarization of the wiring layer surface, and a conventional physical polishing method for planarizing the wiring layer surface has been researched and developed.

Recently, in addition to physical polishing, a chemical mechanical polishing method has been developed.

Conventional chemical mechanical polishing methods are applied to a slurry surface by applying an abrasive called slurry, which is prepared by mixing alumina, silica, pure water, a pH adjusting liquid composed of potassium hydroxide or sodium hydroxide, and the like. Through the chemicals involved, the surface of the wafer is chemically reacted, and the grinding particles mechanically polish the surface of the wafer and then clean the slurry on the surface of the wafer.

Conventional chemical mechanical polishing apparatus for implementing such a chemical mechanical polishing method is a slurry described above in the polishing pad, the wafer chuck adsorbing the wafer on the upper surface of the polishing pad, the wafer or the polishing pad is rotated at a predetermined speed. Slurry supply unit for supplying the wafer, the wafer stage where the chemical mechanical polishing is finished, the wafer stage is temporarily loaded by the wafer chuck, the wafer loaded on the wafer stage is transferred by a transfer device such as a robot arm, the slurry buried in the wafer The slurry removal apparatus which removes a primary, and the slurry washing | cleaning apparatus which wash | cleans a residual slurry after a slurry is removed in a slurry washing | cleaning apparatus.

At this time, the wafer chuck is formed with a vacuum hole arranged in a circular shape on a plurality of concentric circles to adsorb the wafer, the vacuum hole is in communication with a predetermined space in communication with the vacuum pressure generating portion, the vacuum pressure generated in the vacuum pressure generating portion is The same applies to the vacuum hole.

However, when chemical mechanical polishing is performed on the wafer by such a conventional chemical mechanical polishing apparatus, as shown in FIG. 1A, the wafer may be formed at the circumferential portion of the wafer due to manufacturing errors such as flatness of the wafer chuck or polishing pad or processing conditions. There is a problem that the thickness of is smaller than the thickness at the center portion of the wafer.

In addition, as shown in FIG. 1B, the thickness at the circumferential portion of the wafer becomes thicker than the thickness at the center portion of the wafer due to manufacturing errors or processing conditions such as flatness of the wafer chuck or polishing pad.

Another problem is that there is no means for correcting the difference in the profile of each wafer, so it takes a lot of time and effort to correct it.

Accordingly, the present invention has been made in view of such a conventional problem, and an object of the present invention is to allow uniform chemical mechanical polishing to be performed over the entire surface of a wafer.

Other objects of the present invention will become more apparent from the following detailed description of the invention.

1A and 1B are graphs showing the profile trend of chemically mechanically polished wafers.

Figure 2 is a perspective view showing a chemical mechanical polishing apparatus according to the present invention.

3 is a cross-sectional view taken along the line A-A of FIG.

Figure 4 is a plan view showing the position of the wafer adsorption pad and the sealing ring.

The chemical mechanical polishing apparatus for achieving the object of the present invention is provided on the polishing table, and the upper surface of the polishing table, the recess is formed on the upper surface in a predetermined shape and a plurality of holes formed in a predetermined pattern on the base surface of the recess A wafer chuck comprising a formed wafer adsorption pad, a cover plate for sealing the recessed portion, a sealing ring interposed between the cover plate and the recessed portion so that the holes are separated into a plurality of independent regions, and piping connected to each region, A vacuum pressure generator and a gas supply device which communicate with each other in parallel again with the pipe, a wafer stage where the wafer polished by the wafer chuck is temporarily transferred, a slurry removal unit for removing the slurry on the wafer of the wafer stage, and a slurry Wafer cleaning unit for cleaning the wafer from which the slurry is removed from the removal unit It characterized in that it comprises.

Hereinafter, the chemical mechanical polishing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

Chemical mechanical polishing apparatus 100 according to the present invention as a whole has a disk-shaped polishing table 110, polishing chuck 120, wafer stage 130, slurry removal device 140 and slurry cleaning device 150, It consists of a turnover table 160.

Specifically, the polishing table 110 is provided with a polishing pad 115, the polishing chuck 120 is installed in a state spaced apart from the upper surface of the polishing pad 115 by a predetermined distance, the polishing chuck 120 is a wafer ( It is installed so as to be movable to the wafer stage 130 which will be described later in the state in which 101 is fixed.

Referring to this cross-sectional view of the polishing chuck 120 is as follows.

The polishing chuck 120 is in the shape of a disc again and is attached to the wafer adsorption pad 121 and the recessed portion 121a of the wafer adsorption pad 121 having a recessed portion 121a having a circular groove shape on the top surface thereof. Installed in the cover plate 122, the cover plate 122 and the wafer adsorption pad 121 is fixed to the cover plate 122, the fixed cover 123, the fixed cover 123 is formed with a cylindrical protrusion (122a) is inserted into A driving device (not shown) for rotating the wafer chuck rod 124 and the wafer chuck rod 124 and a wafer suction pad (to adjust the distance between the wafer 101 and the polishing pad 115) while fixing the wafer 101. Ring-shaped sealing ring installed between the plurality of pipes 125a and 125b communicating with 121 and the cylindrical protrusion 122a of the cover plate 122 and the bottom surface of the recess 121a of the wafer suction pad 121. 126.

More specifically, the wafer adsorption pad side vacuum holes 121b are formed in the base surface of the recess 121a formed in the wafer adsorption pad 121 so as to penetrate the base surface of the recess 121a. The holes 121b are formed to be circularly arranged on imaginary concentric circles whose diameter is gradually increased.

In addition, the protruding height of the cylindrical protrusion 122a of the cover plate 122 is formed to be somewhat smaller than the base surface depth of the recess 121a.

In this case, a predetermined space 127 is formed between the base surface of the recess 121a and the end of the cylindrical protrusion 122a, and at least two through holes 122b and 122c are formed in the cylindrical protrusion 122.

At this time, the position of the through-holes 122b and 122c formed in the cylindrical protrusion 122a is very important, and the position of the through-holes 122b and 122c is, in one embodiment, a boundary surface divided into two by dividing the radius of the cylindrical protrusion 122a. Concave grooves 122d are formed in the cylindrical protrusions 122a to separate the two regions, and the through holes 122b and 122c are formed at predetermined positions within the range not departing from the respective regions.

At this time, the groove 122d is provided with a rubber ring sealing ring 126 having a ring shape so that the cylindrical protrusion 122a of the cover plate 122 and the wafer adsorption pad 121 are formed by the sealing ring 126. The recess 121a is completely separated into two regions. In this case, the separated region is defined as a first region 128a and a second region 128b.

In this manner, two wafer chuck rod side through holes are also formed in the wafer chuck rod 124 corresponding to the through holes 122b and 122c of the cylindrical protrusion 122a in which the first region 128a and the second region 128b are formed. .

One end of each of the pipes 125a and 125b is inserted into the through holes 122b and 122c formed in the cylindrical protrusion 122a of the two wafer chuck rod-side through hole-cover plates 122 thus formed. One end of 125a and 125b is hermetically coupled to two through holes 122b and 122c previously formed in the cover plate 122.

In this case, the two pipes 125a and 125b should be provided with a twist prevention means so that the pipes 125a and 125b are not twisted and damaged even if the wafer chuck 120 rotates.

The other ends of the two pipes 125a and 125b communicate with the vacuum pressure generating units 129a and 129b, respectively, and part of the pipes 125a and 125b communicate with one end of the branch pipes 125c and 125d. In the other end of the branch pipe (125c, 125d) nitrogen gas supply unit (129c, 129d) is in communication.

At this time, solenoid valves are installed in the two pipes 125a and 125b communicating with the vacuum pressure generating units 129a and 129b to control the opening and closing, and two branch pipes 125c communicating with the nitrogen gas supply units 129c and 129d. 125d) is also provided with a solenoid valve to control the opening and closing.

The vacuum pressure generators 129a and 129b configured as described above adsorb the wafer 101 by forming a vacuum pressure inside the wafer suction pad side vacuum hole 121b formed in the wafer suction pad 121 of the polishing chuck 120. It serves to adsorb and fix the pad 121.

The nitrogen gas supply units 129c and 129d blow nitrogen gas into the wafer adsorption pad side vacuum hole 121b to remove the slurry introduced into the wafer adsorption pad side vacuum hole 121b.

Meanwhile, a wafer stage 130 having a stepped portion (not shown) on which the wafer 101 is seated is installed, as shown in FIG. 2, adjacent to the polishing chuck 120 configured as described above.

The wafer 101 seated on the wafer stage 130 is transferred to the slurry removal device 140 by a wafer transfer device such as a robot arm (not shown), and the slurry removal device 140 includes two slurry removal rollers ( 142 and 144 abut and rotate to primarily remove the slurry on the wafer 101.

The wafer 101 from which the slurry is removed from the slurry removal device 140 is transferred to the slurry cleaning device 150 and cleaned, and then subjected to a spin dry process.

The slurry cleaning device 140 includes a wafer turn table 152 for rotating the wafer 101 at high speed, and a pure water supply nozzle 154 for supplying pure water to the wafer 101 seated on the wafer turn table 152. .

The turn-over table 160 for changing the front and the back of the wafer 101 is installed near the slurry cleaner 140 so that the front surface of the wafer 101 is turned upward by the turn-over table 160. 101 is loaded into wafer cassette 170.

Referring to the accompanying drawings, the action of the wafer chuck of the chemical mechanical polishing apparatus according to the present invention configured as described above is as follows.

First, after polishing is performed by a chemical mechanical polishing apparatus, the cross-sectional profile of the wafer 101 is measured, and when a cross-sectional profile tendency as shown in FIGS. 1A and 1B occurs, for example, illustrated in FIG. 1B. As described above, the grinding of the center portion of the wafer 101 is less chemically mechanically polished than the edge portion of the wafer 101, that is, at the center portion of the wafer 101 when the center portion of the wafer 101 is convexly ground. The polishing amount must be increased.

To realize this, the wafer corresponding to the second region 128b is operated by opening the solenoid valve while simultaneously operating the vacuum pressure generator 129a communicating with the pipe 125a communicating with the second region 128b. The vacuum pressure is generated in the suction pad side vacuum hole 121b to firmly adsorb and fix the wafer 101 to the wafer suction pad 121.

Thereafter, the solenoid valve communicating with the nitrogen gas supply unit 129b of the pipe 125b communicating with the first region 128a is opened to open the wafer adsorption pad 121 and the wafer 101 corresponding to the first region 128a. The nitrogen gas is supplied so that a predetermined pressure is generated by the nitrogen gas so that the wafer 101 corresponding to the first region 128a protrudes a predetermined height.

At this time, the opening degree of the solenoid valve and the pressure measurement of the first region 128a are performed very precisely so that the polishing amount at the center portion of the wafer 101 is equal to the edge portion of the wafer 101.

Meanwhile, even when the profile of the chemical mechanically polished wafer 101 is the same as that of FIG. 1A, the above-described method may be applied to perform the same amount of polishing of the center of the wafer 101 and the edge portion of the wafer 101.

As described in detail above, when chemical mechanical polishing is performed on the wafer by a chemical mechanical polishing apparatus, when the center portion of the wafer is polished more than the edge portion of the wafer or the center portion of the wafer is compared to the edge portion of the wafer When less polished, there is an effect of forcibly adjusting the height of the center portion of the wafer or the edge portion of the wafer to uniform the amount of polishing over the entire surface of the wafer.

Claims (3)

A polishing table; A wafer adsorption pad provided on an upper surface of the polishing table and having a recessed portion formed on an upper surface thereof in a predetermined shape, and having a plurality of holes formed in a predetermined pattern on a bottom surface of the recessed portion, a cover plate for sealing the recessed portion, and the holes A wafer chuck including a sealing ring interposed between the cover plate and the recessed portion so as to be separated into a plurality of independent regions, and pipes connected to the respective regions; A vacuum pressure generator and a gas supply device connected to each of the pipes again in a parallel manner; A wafer stage to which the wafer polished by the wafer chuck is temporarily transferred; A slurry removal unit for removing the slurry adhered to the wafer of the wafer stage; And a wafer cleaning unit for cleaning the wafer from which the slurry is removed from the slurry removing unit. 2. The chemical mechanical polishing apparatus according to claim 1, wherein the cover plate is provided with a protrusion that is fit and coupled to the recess, and a predetermined space is formed between the protrusion and the base surface of the recess. The method of claim 1, wherein one sealing ring is installed so that first and second regions are formed between the cover plate and the recess, and the pipe is in communication with the first and second regions. Chemical mechanical polishing apparatus.