KR20100052028A - Dressing method of pads in double side polisher - Google Patents

Abstract

PURPOSE: A method for dressing a pad of a double-side polisher is provided to reduce the amount of glazing, and to maintain desirable flatness of a wafer after polishing, and to extend the service life of a pad. CONSTITUTION: A method for dressing a pad of a double-side polisher is as follows. A brush and a nozzle block(47) are in contact with a first pad(34). An upper surface plate(39) is descended so that a second pad(40) can be in contact with the brush and the nozzle block. The high-pressure deionized water is sprayed to the first and second pads through the brush and the nozzle of the nozzle block. Solids stuck on the first and second pads are separated from the first and second pads. The solids separated from the first and second pad are swept away through the brush and the nozzle block.

Description

Dressing method of double side polisher {Dressing method of pads in double side polisher}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pad dressing method of a double side polisher capable of simultaneously polishing both sides of a semiconductor wafer such as a silicon wafer, in particular, remaining in each pad attached to the upper and lower plates in the polishing process. It relates to a pad dressing method that can remove the solids.

In general, a bare silicon wafer manufacturing process for manufacturing a semiconductor device goes through a slicing process of cutting a cylindrical silicon ingot into a single wafer. In slicing, diamond blades are used or piano wires called wire saws are used. At this time, since the unevenness exists on the surface of the cut wafer, it must go through a planarization process by polishing.

Polishing includes single-sided polishing, which polishes one side of the wafer, or double-sided polishing, which simultaneously polishes both sides, of which the flatness of the processed wafer is improved and the back side contaminants are brought to the front side. It is a method of simultaneously polishing the surface and back of the semiconductor wafer for the purpose of preventing the transition. In the above, the double-sided polishing is less flat than the single-sided polishing, so the flatness is excellent.

An apparatus used to polish the surface and the back side of a wafer in a double side polishing process is a so-called double side polisher, and a wafer carrier is employed to support a wafer to be polished in the double side polisher. A conventional double side polisher and wafer carrier are shown in FIGS. 1A, 1B and 2.

1A to 2, the conventional double-sided polishing machine 9 is provided with an upper plate 1 and a lower plate 3 that rotate in opposite directions. Pads 2 and 4 are attached to the lower surface of the upper surface plate 1 and the upper surface of the lower surface plate 2 to polish the surface and the back surface of the wafer w, respectively. The conventional wafer carrier 5 is supported between the upper plate 1 and the lower plate 3, and is mounted in plural as shown in FIG. 1B. The wafer carrier 5 has a disk-shaped wafer holding hole 6 into which the wafer w is inserted and held, and has five slurry holes 8 having different sizes along the circumference of the wafer holding hole 6. It is arranged.

After the wafer w is inserted into the wafer holding hole 6 of the wafer carrier 5 in the double-side polisher 9 having the above-described configuration, the upper plate 1 moves downward to rotate the wafer w. Done. At this time, the lower plate 3 is also rotated together. The slurry required for polishing is supplied to the front surface of the wafer w through the top plate 1 and also flows into the rear surface of the wafer w through the slurry hole 8. When the slurry is supplied between the wafer w and the pads 2 and 4, the chemical components in the slurry react with the surface and the backside of the wafer w to form a reaction layer. In such a state, when the wafer w and the pads 2 and 4 are frictionally rotated relative to each other, the reaction layer is physically removed and the surface and the back surface of the wafer w are smoothly processed. Slurries generally used include hard silica particles, and are highly alkaline, so that the surface of the wafer (w) is oxidized to melt the wafer (w) as an oxide and to remove oxides and composite products with silica particles. The wafer carrier 5 rotates and revolves the wafer w.

Factors affecting the polishing characteristics are largely divided into factors that occur in the polishing process, the parameters for the workpiece and the material properties of the consumables supplied. Factors generated in the polishing process include pressure, relative speed, and polishing temperature. Factors for the workpiece include wafer hardness and wafer flatness before polishing. Factors related to the material properties of the consumables supplied are factors such as the slurry chemical composition, particle size, particle type, particle content and slurry feed flow rate, and the shear modulus, surface roughness, and pore of the pad. There are factors related to the pad, such as size, groove shape, groove size, density, and the like.

However, 300 mm double side grinders currently in use are inferior in pad life time to conventional double face grinders and poor in flatness, especially in edge roll-off (ERO) quality levels. This is because the formation rate of glazing on the pad surface is faster from the beginning of the pad life than other devices, and the glazing refers to a solid substance in which wafer reactants, slurry particles, and foreign substances are vitrified after high pressure and temperature. As the glazing occurs, a deformation of the pad thickness profile is caused, which causes deterioration of the flatness of the wafer, thereby repeating a vicious cycle of shortening the pad life.

Therefore, there is a need for a method of maintaining the polishing rate of the wafer through the pad glazing and improving the flatness and surface roughness, and to remove the wafer reactants, slurry particles, and foreign substances remaining on the pad surface at the end of each polishing. For this purpose, high-pressure deionized water (DIW) injection is performed (so-called high pressure dressing). The current high pressure deionized water spraying method has the effect of slowing the pad glazing time and reducing the amount of glazing generation.However, the problem is that the flatness of the wafer after the polishing process does not satisfy the desired level and the ERO is urgently improved. It is pointed out.

The present invention has been conceived to solve the above-mentioned problems, the problem to be solved by the present invention is to provide a pad dressing method that can perform the pad dressing operation of the effective double-side polishing machine by deriving the optimum conditions of high-pressure deionized water injection will be.

The pad dressing method according to the present invention for solving the above problems, the surface of the wafer to the first and second pads while supplying a slurry, including the lower plate with the first pad and the upper plate with the second pad; A dressing method for removing solids produced by the reaction of the wafer and the slurry during the polishing in the double-side polishing machine for simultaneously polishing the back surface and fixed on the surface of the first and second pads, the brush and the first pad in contact with the first pad; Installing a nozzle block, lowering the upper plate such that the second pad contacts the brush and the nozzle block, and deionized water is applied to the first and second pads through a nozzle formed on the brush and the nozzle block. Spraying to separate solids adhered to the first and second pads, and moving the brushes and nozzle blocks to move the brushes and nozzles Sweeping and removing the solids separated from the first and second pads through a brush formed in the block, the deionized water injection angle of the nozzle is 25 degrees, the deionized water injection pressure is 120 to 150 Bar, the The deionized water discharge amount from the nozzle is 1.2 LPM, characterized in that to maintain the distance between the nozzle and the first pad or the second pad at 50 to 60 mm.

According to the present invention, there is an effect of delaying the timing of the occurrence of glazing on the pad of the double-side polishing machine and reducing the amount of glazing. Also, the flatness of the wafer after the polishing process can satisfy a desired level and extend the life of the pad.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only this embodiment is to complete the disclosure of the present invention, those skilled in the art to which the present invention belongs It is provided to fully inform the scope of the invention, and the invention is defined only by the scope of the claims.

3 is a side view of a double-side polisher capable of implementing the pad dressing method according to the present invention. The lower surface plate 33 is provided on the turntable 31, and the upper surface plate 39 is provided to correspond to the lower surface plate 33.

The inner circumference gear 35 is installed in the upper center of the lower plate 33. Then, the first pad 34 is attached to the remaining portion except the center where the inner gear 35 is formed on the lower plate 33, and the outer gear 37 is installed on the edge portion of the first pad 34. do.

The upper plate 39 corresponds to the lower plate 33 by the support 43 and is driven up and down by the driving device 45. The groove 41 in which the inner circumference gear 35 is inserted is formed in the center of the surface facing the lower surface plate 33 of the upper surface plate 39. In the above, the side surface of the groove 41 is uneven to engage with the outer surface of the inner circumferential gear 35. Then, the second pad 40 is attached to the remaining portion except for the center where the groove 41 of the surface facing the lower plate 33 of the upper plate 39 is formed.

The operation of the double-side polishing machine of the above-described configuration will be described.

A plurality of disc shaped carriers (not shown) are mounted on the first pad 34 of the lower plate 33 with a plurality of wafers (not shown) to be processed. In the above, the carrier penetrates a portion to which the wafer is inserted so that the surface and the back of the wafer are exposed, and the inner and outer sides of the carrier are concave and convex to engage the inner and outer gears 35 and 37. Then, the upper peripheral plate 39 is inserted into the groove 41 by the drive device 45 so that the second pad 40 is brought into contact with the carrier. Therefore, each of the surface and the back surface of the wafer is pressed in contact with the first and second pads 34 and 40 attached to the lower plate 33 and the upper plate 39. In the above drive device 45 is composed of a cylinder to raise and lower the upper plate (39).

The lower plate 33 and the inner and outer gears 35 and 37 are rotated by respective driving devices (not shown). At this time, the plurality of carriers in which the plurality of wafers are inserted are respectively rotated by the inner gear 35 and the outer gear 37 while driving along the lower platen 33. In addition, since the inner circumferential gear 35 is inserted into and engaged with the groove 41, the upper plate 39 rotates.

Then, a slurry made of an abrasive and a corrosion solution is injected. At this time, the corrosive component corrodes the rough portions of the surface and back of the wafer to be processed and the abrasive promotes abrasion when the corroded portion is rubbed with the first and second pads 34 and 40. Therefore, the wafer to be processed is mirror polished simultaneously on the rough surfaces of the surface and the back.

The above-described configuration is a configuration of a polishing machine for performing a polishing process, and the dressing method of the present invention is performed by adding a high pressure dressing system as a dressing apparatus to this configuration. The dressing device is composed of a pressing means 49, a drain pipe 51, a dresser arm 53, and a brush and a nozzle block 47.

The pressurizing means 49 is made of a high pressure pump to increase the water pressure to enable high pressure injection of deionized water used when dressing the first and second pads 34 and 40. The drain pipe 51 injects the deionized water pressurized by the pressurizing means 49 to the first and second pads 34 and 40.

In addition, the dresser arm 53 has one side fixed to the support 43 and the other side is provided with a brush and a nozzle block 47. The brush and the nozzle block 47 is formed in a rod shape made of polyvinyl chloride (PVC) and the like, and brushes are formed in contact with the first and second pads 34 and 40 at upper and lower portions thereof, and deionized water is disposed therebetween. The nozzle which sprays the is formed. 4A and 4B are photographs of the brush and the nozzle block 47, showing the brushes 60 and 61 formed in the brush and the nozzle block 47 and the nozzles 71 provided inside the brushes 60 and 61.

The dresser arm 53 allows the brush and nozzle block 47 to reciprocate between the inner gear 35 and the outer gear 37 as well as the up and down movements so as to contact the first pad 34 on the lower plate 33. . In the above, the dresser arm 53 should be in contact with the inner and outer gears 35 and 37 when driving the brush and the nozzle block 47 up and down and reciprocating so that no mechanical interference occurs.

5 is a plan view illustrating a pad dressing method according to the present invention.

After each polishing process, the carrier used in the polishing process is removed, and the dresser arm 53 is lowered to contact the brush and the nozzle block 47 with the first pad 34. Then, the upper plate 39 is lowered by the drive device 45 to bring the second pad 40 into contact with the brush and the nozzle block 47. Accordingly, the brushes (60 and 61 in FIG. 4A) of the upper and lower portions of the brush and the nozzle block 47 may be connected to the first and second pads 34 and 40 attached to the lower plate 33 and the upper plate 39. Contact and pressurization.

Next, the dresser arm 53 is driven left and right while rotating the lower plate 33 and the upper plate 39 so that the brush and the nozzle block 47 reciprocate between the inner gear 35 and the outer gear 37. Do it. Then, the deionized water is increased by the pressurizing means 49, and is injected at high pressure through the drain pipe 51 to the first and second pads 34 and 40. At this time, the deionized water sprayed at high pressure separates the solids from the surfaces of the first and second pads 34 and 40, and the brush and the nozzle block 47 sweep the solids separated by the brushes formed above and below. Remove from the first and second pads 34, 40.

After the dressing of the first and second pads 34 and 40 is completed, the upper plate 39 is driven upward, and then the dresser arm 53 is driven upward and left or right to drive the brush and the nozzle block 47 during the polishing process. ) Does not interfere with the drive of the upper plate (39).

At this time, the nozzle spray angle of the high pressure dressing system, the spraying pressure during dressing, the amount of deionized water discharged, and the nozzles to improve the ERO flatness and the life of the pad used, which are problems of the current double-side polishing machine used in the double-side polishing process. The distance between pads was sought.

Table 1 summarizes the dressing conditions before improvement (before) and after improvement (invention).

First, the spray angle of the nozzle was reduced to 25 degrees, and the pressure during dressing was increased to 120 to 150 Bar. The discharge amount from the nozzle was reduced to 1.2 LPM and the distance between the nozzle and the pad was increased to 50 to 60 mm.

According to this dressing condition change, as shown in FIG. 6, the pads were replaced after 310 runs when the present invention was applied, whereas the pads had to be replaced after 175 runs. Accordingly, the pad life is improved by about 77% compared to the conventional one.

In addition, as shown in FIG. 7 evaluating wafer flatness after double-side polishing, the ERO flatness was improved by 40% in the case of the present invention. As such, it can be confirmed that the wafer flatness and the pad life are improved through the optimization of the dressing conditions.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications are possible by those skilled in the art within the technical idea of the present invention. Is obvious. For example, the configuration of the double-sided polishing machine having a dressing apparatus is described as an example of FIGS. 3 and 5, but the dressing apparatus that removes the glazing on the pad by spraying high-pressure deionized water is illustrated in FIGS. 3 and 5. Even if the structure is not as described above, it can be used in the dressing method of the present invention. Embodiments of the invention have been considered in all respects as illustrative and not restrictive, including the scope of the invention as indicated by the appended claims rather than the detailed description therein, the equivalents of the claims and all modifications within the means. I'm trying to.

1A is a schematic configuration diagram of a conventional wafer double-side polishing machine, and FIG. 1B is a schematic plan view of a state in which a plurality of wafer carriers are mounted on a lower platen.

2 is a schematic plan view for explaining the configuration of a conventional wafer carrier.

3 is a side view of a double-side polisher for carrying out the pad dressing method according to the present invention.

4A and 4B are photographs showing the brush and the nozzle block.

5 is a plan view illustrating a pad dressing method according to the present invention.

6 is a graph showing a comparison of pad life before and after applying the present invention.

7 is a graph comparing wafer flatness before and after applying the present invention.

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

31 Turntable 33 Lower plate 34 First pad

39 Top plate 40 Second pad 47 Brush and nozzle block

49 Pressure unit 51 Drain pipe 53 Dresser arm

60, 61 ... Brush 71 ... Nozzle

Claims (1)

The wafer and the wafer during the polishing in a double-side polisher for simultaneously polishing the surface and the back surface of the wafer with the first and second pads while supplying a slurry including a lower plate with a first pad and an upper plate with a second pad. CLAIMS 1. A dressing method for removing solids produced by reaction of a slurry and stuck to surfaces of said first and second pads, comprising: installing a brush and a nozzle block in contact with said first pad; Lowering the upper plate such that the second pad is in contact with the brush and the nozzle block; Separating deionized water adhered to the first and second pads by high-pressure spraying deionized water onto the first and second pads through a nozzle formed in the brush and the nozzle block; And Moving the brush and the nozzle block to sweep and remove the solids separated from the first and second pads through the brushes formed on the brush and the nozzle block, The deionized water injection angle of the nozzle is 25 degrees, the deionized water injection pressure is 120 to 150 Bar, the deionized water discharge amount from the nozzle is 1.2 LPM, the distance between the nozzle and the first pad or the second pad 50 to 60 mm Pad dressing method, characterized in that the holding.

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