JP3821947B2 - Wafer polishing apparatus and wafer polishing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wafer polishing apparatus and a wafer polishing method for polishing a wafer, particularly a semiconductor wafer and a single crystal silicon wafer.
[0002]
[Prior art]
In general, a wafer is sliced and chamfered from a cylindrical ingot, and then lapped while rubbing a polishing (lap) surface plate and an as-cut wafer with a polishing liquid containing abrasive grains, and the lapping The processed wafer is etched and then guided to a finishing process.
In the finishing process, mirror polishing is performed by a so-called chemical mechanical polishing method using a polishing solution in which SiO ₂ fine particles are suspended in a weak alkaline solution between a polishing cloth and a wafer.
[0003]
In this mirror polishing, as a method of holding the wafer, there is a wax method in which one side of a wafer is attached to a polishing plate using a wax for wafer bonding. In such a wax method, the thickness of the adhesive layer (wax layer) is reduced. It is important to make the thickness of the adhesive layer uniform because the non-uniformity reflects the flatness, parallelism, etc. of the polished wafer as it is. In addition, since it is necessary to remove the wax from the wafer after polishing the wafer, the process becomes complicated, and chemical processing and waste liquid treatment equipment used for applying and removing the wax are necessary, which increases the processing cost. There was a point.
[0004]
The waxless method eliminates the disadvantages of the wax method described above. The waxless method is a first waxless method based on vacuum adsorption and a first method in which a wafer is attached with water using a backing pad made of a porous resin, for example, a polyurethane resin porous body. No. 2 waxless method is used, but all have the advantage that it is not necessary to apply and remove the wax to the wafer.
[0005]
As shown in FIG. 4, the wax-free polishing apparatus using the backing pad has a lower rotary table 1 with a polishing cloth 2 (polishing pad) attached, and a carrier plate 3 and a backing pad 6 on the lower surface side. A plurality of polishing heads 4 to which a wafer holding jig 13 holding a wafer 10 is attached to a plurality of wafer positioning holes (holding holes) 11a, and a slurry for supplying slurry (polishing suspension) to the polishing cloth 2 The polishing apparatus includes a tube 5 and presses the wafer 10 against the polishing cloth 2 on the turntable 1 side to smooth the unevenness of the wafer.
[0006]
The wafer holding jig 13 used in such an apparatus is formed so that the template 7 having one or more wafer positioning holes 11a on the carrier plate 3 is used, and the backing pad 6 is inserted into and fixed to the positioning holes. Yes. The template 7 is made of a glass epoxy resin, a polycarbonate sheet, a polyester sheet or the like, and the backing pad 6 is made of a porous resin, for example, a polyurethane resin porous body.
[0007]
The polishing head 4 rotates and revolves with respect to the lower rotary table 1 to which the polishing cloth 2 is adhered, and the wafer 10 is configured to rotate in the wafer holding jig 13. Here, the term “spinning” means that when a wafer holding jig 13 having another rotation axis is placed on the turntable 1, centrifugal force distribution is generated in the surface of the wafer holding jig, and the wafer holding jig is caused by a difference in centrifugal force. It is a phenomenon that rotates.
That is, in FIG. 4, with respect to the rotation center of the turntable 1, the rotation centers of the plurality of polishing heads 4 are arranged at positions displaced in the radial direction, and both are rotated in the direction of the arrows to thereby hold the wafer holding jig. 13 and the wafer 10 fitted in the holding hole 11a of the wafer holding jig 13 rotate in the direction of the arrow, and as a result, the wafer 10 is polished while rotating and revolving relatively with respect to the polishing pad 2.
[0008]
FIG. 5 shows the structure of another polishing apparatus, which shows a rotating system in which a sun gear 53 and an internal gear 54 are combined. As shown in FIG. Reference numeral 13 denotes a configuration in which a wafer holding hole 11a is formed and outer peripheral teeth 13a are provided on the outer periphery. While meshing with a sun gear 53 provided at the center of the lower rotary platen 51 rotating in the direction of arrow A and an internal gear 54 provided outside the rotary platen 51, the wafer holding jig 13 is rotated and revolved. The wafer 10 is rotated.
This rotation method is used for polishing such as double-side polishing and double-side lapping. A polishing cloth is used for polishing on the upper and lower rotary surface plates, and a polishing surface plate (lapping surface plate) is used for lapping. The wafer holding jig 13 used in this rotation method is also simply called a carrier. In this rotation method, the wafer holding jig (carrier) is forcibly rotated, but the wafer in the carrier is rotated by the same action as the centrifugal force difference, that is, the accompanying phenomenon.
[0009]
In the wax-free polishing apparatus described above, as in the wax polishing apparatus, the non-uniformity in the thickness of the backing pad layer directly reflects the flatness and parallelism of the polished wafer. Therefore, the thickness after polishing is averaged by rotating the wafer in the wafer holding jig 13 during polishing.
Therefore, in wax-free polishing, it is important to stably rotate the wafer during polishing. For this reason, unevenness is provided on the backing pad, and air or a lubricant is interposed between the backing pad and the wafer to reduce the frictional force between the backing pad and the wafer.
[0010]
However, the frictional force between the backing pad and the wafer is affected by the surface roughness of both, and as the surface roughness increases, the frictional force increases and the wafer becomes difficult to rotate, and the flatness after polishing deteriorates. In particular, there are wafers on which a polysilicon layer or an oxide film layer such as PBS (Polyback Seal) or CVD (Chemical Vapor Deposition) is formed on the back surface of the wafer, each having a different roughness.
It is the same that it is preferable to rotate the wafer also in double-side polishing, double-side lapping, and the like.
[0011]
[Problems to be solved by the invention]
In such a wax-free polishing apparatus, when only the polishing head and the carrier plate rotate and the wafer does not rotate during polishing in the template, the nonuniformity of the backing pad thickness reflects the flatness, parallelism, and the like. That is, while the thickness of the wax layer is 1 μm, the backing pad thickness is 100 to 300 μm, the non-uniformity of the backing pad thickness reaches 10 to 50 μm, and the influence on the flatness is far greater than that of wax polishing. It is a big problem.
[0012]
In another rotational polishing method in which the wafer rotates during polishing, if the balance between the positions of the wafer holding jig and the polishing (polishing) head is poor, the rotation of the wafer holding jig becomes unstable.
As described above, in order to manufacture a wafer with good flatness, it is necessary to stably rotate a wafer or a wafer holding jig that is not forced to rotate.
[0013]
The polishing cloth (polishing pad) used in each of the polishing apparatuses uses, for example, a polyurethane-impregnated polyester nonwoven fabric or other nonwoven fabric when performing primary polishing, and a foamed polyurethane layer when performing secondary polishing, for example. A porous abrasive cloth having a two-layer structure of (surface layer) and polyester layer (back layer) has been put into practical use.
For the purpose of increasing the polishing efficiency by stably supplying an abrasive between the wafer and the polishing cloth, these polishing cloths are disposed on the wafer sliding surface of the polishing cloth 2 as shown in FIG. Some use a grooved polishing cloth provided with grooves 20d at equal intervals in a lattice shape. (Japanese Patent Laid-Open No. 9-201765)
[0014]
The present invention provides a wafer polishing apparatus for wafer polishing and a wafer in which the flatness of the polished wafer is improved by devising the groove density of the grooved polishing cloth so that the wafer or the wafer holding jig is stably rotated. An object is to provide a polishing method .
[0015]
[Means for Solving the Problems]
The gist of the present invention is to change the groove density depending on the distance from the center of the polishing cloth (polishing pad), specifically, to increase the groove density as the distance from the center of the polishing cloth increases. The present invention is applied to a polishing method in which the wafer itself is desired to be efficiently rotated by wax-free polishing, double-side polishing, and the like, and the polishing body is not only a polishing pad but also a polishing surface plate for lapping processing ( It is preferable to perform the same groove processing on the lapping plate.
[0016]
That is, a first aspect of the present invention, the wafer polishing apparatus having a polishing cloth to perform the polishing of the wafer while sliding with the relative velocity difference between the wafer,
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. The groove density formed on the moving surface is varied, and the groove density at a portion where the peripheral speed of the polishing body is high is increased with respect to the groove density at a portion where the peripheral speed is low.
[0017]
The invention according to claim 2 is a wafer polishing apparatus having a polishing cloth for polishing the wafer while sliding with a relative speed difference between the wafer and the wafer .
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. The groove density formed on the moving surface is made different, and the groove density at the peripheral part of the polishing body is increased with respect to the groove density located inside thereof.
The density of the lattice-like or concentric grooves and radial grooves formed in the polishing body is varied in a ring shape, and the wafer located on the center side with respect to the plurality of wafers held by the wafer holding jig has no grooves or A wafer located on the outside straddles between a relatively sparse groove part and a relatively dense groove part so as to straddle between a relatively sparse groove part and a relatively dense groove part. Thus, the effect of this invention can be achieved more smoothly if each groove | channel space | interval is set.
[0018]
Invention described in claim 4, it relates c Eha polishing method according to claim 1, wherein the said, is polished of the wafer while sliding with the relative speed difference between the polishing body consisting of the wafer and the polishing pad In the wafer polishing method,
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. Wafer polishing is performed using a polishing body in which the groove density formed on the moving surface is made different and the groove density at a portion where the peripheral speed of the polishing body is high is increased with respect to the groove density at a portion where the peripheral speed is low. It is characterized by that.
[0019]
Invention described in claim 5, it relates c Eha polishing method according to claim 2, wherein the said, is polished of the wafer while sliding with the relative speed difference between the polishing body consisting of the wafer and the polishing pad In the wafer polishing method,
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. The wafer is polished by using a polishing body in which the groove density formed on the moving surface is different and the groove density at the peripheral portion of the polishing body is increased with respect to the groove density located inside the polishing body. To do.
[0020]
Also these inventions were formed on the polishing body lattice shape or a concentric circle and the density of the radial grooves with be different in-ring shape, is wafer positioned on the center side with respect to a plurality of wafers held in the wafer holding jig No groove or a relatively sparse groove part and a relatively dense groove part between the relatively sparse groove part and the relatively dense groove part. so as to bridge between, good to set the respective groove spacing, further, the wafer polishing the wafer polishing method, to smooth the unevenness of the wafer by pressing the wafer adhered with wax pretend over the backing pad polishing cloth It should be a method.
[0021]
In any of the present inventions, the frictional force acting in the wafer follow-up direction is increased without stabilizing the lattice density of the lattice-like or concentric and radial grooves provided on the wafer sliding surface of the polishing body. and performs polishing of Kwai Ha using abrasive bodies of varying density of the grooves.
[0022]
Lattice-shaped or concentric and radial grooves of the polishing body has the effect of rotating the Kwai Ha strikes obliquely to the edge of the Kwai Ha.
However, the direction of this action depends on which part of the edge the groove hits, and the groove that hits the outer peripheral side (the side with the higher relative speed) of the polishing cloth acts in the follower direction, and the center side of the polishing cloth (relative The groove that hits the lower speed side acts in the direction opposite to the follow-up direction.
Therefore, smooth follow-up rotation is possible by making the groove density on the outer peripheral side (the side with the higher relative speed) of the polishing cloth denser (increase) than the groove density on the center side (the side with the lower relative speed) of the polishing cloth. Become.
[0023]
Thus as in claim 6 wherein, the center side the density of the lattice-shaped or concentric and radial grooves formed in the polishing body with be different in a ring shape, for a plurality of wafers held in the U Eha holding jig Situated in Kwai Ha so as to straddle between the relatively dense grooves site and no or relatively sparse groove portion groove and Kwai Ha is relatively sparse groove portion relative located outside so as to straddle between the dense grooves sites, by setting the respective groove spacing, more preferred co-rotation rotational and flatness of Kwai wafer is achieved.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.
[0025]
FIG. 1 shows an example of the groove shape of a lattice-like or concentric and radial groove that is increased as the density of the groove formed on the wafer sliding surface of the polishing cloth (polishing pad) 2 is further away from the central part to the peripheral side. .
(A) is an example of the lattice-like groove density, the central portion 21f is set to 20f without grooves, the outer side 21b is set to a sparse groove 20b, and the outermost side 21a is set to a dense groove 20a.
Actually, for example, a polishing cloth (polishing pad) having a diameter of 1.4 m has no groove at the center, a ring circle near the center is provided with a 40 mm square sparse density groove, and a 10 mm square dense groove at the periphery. Form. The thickness of the polishing cloth (polishing pad) is 1 to 1.5 mm, and the groove has a depth of 0.5 to 1 mm and a width of 2 to 3 mm. These grooves are formed by cutting a polishing cloth (polishing pad), but may be formed by pressing.
[0026]
(B) is a vertical longitudinal sectional view of (A), arrow A is the direction of rotation of the polishing pad 2, arrow B is the direction of rotation of the wafer holding jig for fitting the wafer 10 rotatably, and arrow C is the rotation. The rotation directions of the wafer 10 to be processed are shown.
[0027]
As is clear from this figure, the wafer 10 located on the outer side is sparsely grooved so that the wafer 10 located on the center side held by the wafer holding jig straddles between the grooveless portion 20f and the sparsely grooved portion 20b. By setting the groove interval so as to straddle between the part 20b and the dense groove part 20a, more preferable rotation and flatness of the wafer 10 can be achieved.
[0028]
FIG. 2 shows a polishing cloth according to another embodiment, wherein the grooves are formed concentrically and radially, the center portion is set to no groove 20f, the outer side is a sparse groove 20b, and the outermost side is set to a dense groove 20a. It is.
Further, the wafer 10 positioned on the outer side of the wafer 10 positioned on the center side held by the wafer holding jig straddles between the grooveless portion 20f and the sparse groove portion 20b, so that the sparse groove portion 20b and the dense groove portion 20a. As described above, the groove interval is set so as to straddle between the two.
[0029]
According to this embodiment, by forming such a groove in the polishing pad 2, the slurry interposed between the wafer 10 and the polishing pad 2 is pushed out into the groove 20 (20a, 20b). Therefore, the wafer 10 comes into contact with the polishing cloth 2 without being lifted from the polishing cloth 2 due to the hydroplaning phenomenon, and the frictional force increases.
This frictional force acts on the entire surface of the wafer. However, if the density of the grooves 20 is increased toward the outer peripheral side of the polishing cloth 2, the wafer 10 and the polishing cloth 2 are easily brought into contact with each other, and the frictional force acting in the follower direction increases. The wafer or the wafer holding jig is easily rotated.
The effect of the present invention was confirmed by performing polishing with a rotating polishing apparatus.
[0030]
First, in the examples, the polishing cloth (polishing pad) was formed of a non-woven fabric, and specifically, Suba600 (manufactured by Rodel Nitta Co., Ltd.) was used.
In the polishing cloth (polishing pad) 2 having a diameter of 1400 mm, as shown in FIG. 2A, the center to the diameter of 470 mm form a 40 mm square groove 20c, the diameter of 470 to 1200 mm is the 20 mm square groove 20b, and the diameter of 1200 to 1200. 1400 mm formed a 10 mm square groove 20a. Each of the grooves has a depth of 0.7 mm and a width of 3 mm. The wafer holding jig has a diameter of 565 mm and can charge five 8-inch wafers. The wafer 10 used was one having PBS formed on the back surface.
These were polished under the conditions of a polishing load of 240 g / cm ² , a platen rotational speed of 35 rpm, and a polishing time of 15 minutes.
[0031]
(Comparative example)
The polishing cloth was formed of a non-woven fabric. Specifically, Suba600 (manufactured by Rodel Nitta Co., Ltd.) was used, and polishing was performed with a rotating type polishing apparatus in the same manner as in the example.
Then, as shown in FIG. 2B, a 20 mm square structure 20d was formed with a uniform density on a polishing cloth having a diameter of 1400 mm. Each of the grooves 20d has a depth of 0.7 mm and a width of 3 mm. The wafer holding jig 13 has a diameter of 565 mm and can be charged with five wafers. The wafer 10 used was a surface on which a PBS layer was formed.
These were polished under the same polishing load as in the example, 240 g / cm ² , a platen rotational speed of 35 rpm, and a polishing time of 15 min.
[0032]
When the flatness of the example and the comparative example was evaluated, the total flatness (Total Thickness Variation: TTV) was 3.5 μm in the comparative example, and the total flatness was significantly improved to 1.0 μm in the example. Understandable.
FIG. 3 shows the flatness shape. This evaluation was performed using a capacitance type wafer flatness measuring apparatus.
As is clear from this figure, the embodiment shown in (A) can obtain a substantially horizontal shape, whereas the comparative example shown in (B) can only obtain a slanted shape. That is, it can be seen that by polishing using the polishing body of the present invention, the wafer is efficiently rotated, polished in a rotationally symmetric shape, and a wafer having a substantially horizontal shape and good flatness can be obtained.
[0033]
【The invention's effect】
As described above, according to the present invention, the flatness of the polished wafer is improved by the stable rotation of the wafer or the wafer holding jig. Note that the present invention is not limited to this embodiment, and double-side polishing and lapping are effective because the wafer rotates in the carrier. In the embodiment, a batch type example in which a plurality of sheets are processed simultaneously has been shown. However, the same effect can be obtained by single wafer wax-free polishing in which the center of rotation of the polishing head and the center of rotation of the wafer are aligned. Furthermore , even when the wafer is attached to the wafer holding jig (polishing plate) with wax, the wafer holding jig itself can be efficiently rotated by using the polishing body of the present invention, and the same effect can be obtained. It is done.
[Brief description of the drawings]
1A and 1B show a groove shape of a polishing cloth according to an embodiment of the present invention, in which FIG. 1A is an example of a lattice groove, FIG. 1B is a vertical longitudinal sectional view of FIG. 1A, and FIG. An example of the groove | channel which consists of radial shapes is shown.
FIG. 2 shows the groove shape of the polishing pad used in the experiment for confirming the effect of the present invention, in which (A) is an example and (B) is a comparative example.
FIG. 3 shows the flatness shape of Example (A) and Comparative Example (B). FIG. 4 shows a wax-free polishing apparatus using a backing pad.
FIG. 5 shows a wafer rotation type polishing apparatus in which a sun gear and an internal gear are combined.
[Explanation of symbols]
2 Polishing cloth 10 Wafer 13 Wafer holding jig 20 Groove

Claims (6)

In a wafer polishing apparatus having a polishing cloth that polishes the wafer while sliding with a relative speed difference with the wafer,
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. A wafer polishing apparatus characterized in that the groove density formed on the moving surface is made different so that the groove density at a portion where the peripheral speed of the polishing body is high is increased relative to the groove density at a portion where the peripheral speed is low. In a wafer polishing apparatus having a polishing cloth that polishes the wafer while sliding with a relative speed difference with the wafer,
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. A wafer polishing apparatus characterized in that the groove density formed on the moving surface is made different so that the groove density at the peripheral edge portion of the polishing body is increased with respect to the groove density located inside thereof. The density of the lattice-like or concentric grooves and radial grooves formed in the polishing body is varied in a ring shape, and the wafer located on the center side with respect to the plurality of wafers held by the wafer holding jig has no grooves or A wafer located on the outside straddles between a relatively sparse groove part and a relatively dense groove part so as to straddle between a relatively sparse groove part and a relatively dense groove part. The wafer polishing apparatus according to claim 1 or 2, wherein a groove interval is set as described above. In the wafer polishing method of polishing of the wafer while sliding with the relative speed difference between the wafer and polishing cloth or Ranaru polishing body,
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. Wafer polishing is performed using a polishing body in which the groove density formed on the moving surface is made different and the groove density at a portion where the peripheral speed of the polishing body is high is increased with respect to the groove density at a portion where the peripheral speed is low. A wafer polishing method characterized by the above. In the wafer polishing method of polishing the wafer while sliding with a relative speed difference between the wafer and a polishing body made of a polishing cloth,
A wafer slide on which the wafer slides in a direction away from the center of the polishing body is provided with a lattice-like or concentric groove and a radial groove at predetermined intervals on the wafer sliding surface of the polishing body made of the polishing cloth. The wafer is polished by using a polishing body in which the groove density formed on the moving surface is different and the groove density at the peripheral portion of the polishing body is increased with respect to the groove density located inside the polishing body. Wafer polishing method. The density of the lattice-like or concentric circles and radial grooves formed on the polishing body is varied in a ring shape, and the wafer located on the center side with respect to the plurality of wafers held by the wafer holding jig is not grooved or relatively So as to straddle between a relatively sparse groove part and a relatively dense groove part, and so that a wafer located outside straddles between a relatively sparse groove part and a relatively dense groove part. 6. The wafer polishing method according to claim 4 , wherein a groove interval is set .

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