JP2610623B2 - High precision flat polishing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a high-precision planar polishing apparatus capable of generating a uniform distribution of a processing load on a processed surface of an object to be polished and performing high-precision planar polishing. About.

(Prior Art) Wafers (mainly made of silicon) are well known as substrates for ICs and transistors. Since the wafer surface needs to be finished to a flat mirror surface with no processing distortion and a clean mirror surface, various processing and polishing methods and apparatuses have been proposed and developed. However, in the conventional wafer processing method, since rotation transmission and processing load transmission are performed using a pressure shaft, a universal joint, and the like, the uniformity and uniformity of the processing load are limited, and the wafer is polished. Due to the influence of the moment exerted on the wafer holding device system by the frictional force with the cloth, there is a problem that local flatness and parallelism defects are large.

(Problems to be Solved by the Invention) The present invention was invented in order to solve the above-mentioned problems, and a processing load having a uniform distribution was generated on a processing surface of a workpiece such as a wafer to be polished. High precision that reduces uneven load on wafer processing due to the effect of moment on the wafer holding device system due to the frictional force between the workpiece and the platen polishing unit, and improves the flatness and parallelism of the polished workpiece surface An object of the present invention is to provide a planar polishing apparatus.

(Means for Solving the Problems) In order to solve the above-mentioned problems, a high-precision planar polishing apparatus according to the present invention comprises: a platen having a polishing section provided on an upper surface; A fixed plate, a polishing shaft end flange attached to the lower end of the polishing shaft and located at a predetermined interval above the polished work fixed plate, and a gap between the polished work fixed plate and the polishing shaft end flange. It has an installed and extendable side wall, has a pressure chamber to which air or water is added as a fluid, and when the polishing plate and the polishing shaft are rotated, the polishing object fixed to the polishing object fixing plate. The object is pressed and slid on the portion to be polished, and it is possible to perform high-precision planar polishing that generates an evenly distributed processing load on the processing surface of the object to be polished, and the fluid pressure applied to the pressure chamber and / or Or, by adjusting the spring constant of the pressure chamber side wall, The side wall of the pressure chamber is made of natural rubber or synthetic rubber reinforced by a metal bellows or a piano wire or various fibers or a combination thereof, and the polishing object fixing plate Has a shape or shape that is substantially the same as that of the object to be polished at the connection portion.

A disk made of ceramics, for example, alumina is used as the platen to be polished. A stainless steel bellows is preferably used as the metal bellows.

If the polishing agent is continuously supplied to the polishing portion of the surface plate and the object to be polished is polished in a state where the polishing agent is contained in the polishing portion, in addition to the mirror polishing of the silicon wafer, no polishing cloth is used. Lapping can also be performed.

The object of polishing by the apparatus of the present invention is typically mirror polishing of a silicon wafer, but lapping can also be performed, and polishing of ceramics, glass, and metal can also be performed.

(Operation) By transmitting the rotational moment of the polishing shaft 20 to the polished work fixing plate 14 via the pressure chamber 22, a processing load having a uniform distribution is generated on the processed surface of the polished work W such as a wafer. Wafer processing uneven load due to the influence of the moment exerted on the wafer holding device system by the frictional force between the workpiece W and the platen polishing unit, thereby improving the flatness and parallelism of the workpiece processing surface. It is.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic explanatory view showing a main part of a high-precision planar polishing apparatus 2 according to the present invention. In the figure, reference numeral 4 denotes a surface plate which constitutes a part of the polishing apparatus 2, and a polishing section 6 formed of a rigid polyurethane foam or the like is provided on an upper surface thereof. The polishing portion 6 provided on the upper surface of the platen 4 with a rigid polyurethane foam or the like is generally called a polishing cloth. In addition, at the time of lapping or the like, the polishing process is performed without using the polishing cloth and using the upper surface of the platen 4 as a polishing portion. The setting panel 4 is rotatable about a rotation shaft 8 suspended at the center of the lower surface. Reference numeral 10 denotes a pipe provided above the central portion of the upper surface of the surface plate 4, and the abrasive 12 flows down to the surface of the polishing cloth 6 together with a liquid such as water during the polishing operation, and the abrasive 12 is contained on the surface of the polishing cloth 6. It acts to make it work. As the polishing agent 12, in the case of polishing a silicon wafer, colloidal silica and an alkali agent are used,
In the case of lapping, silicon carbide, alumina or cerium oxide is used.

Numeral 14 denotes a plate to be polished, which is displaced from the center of the platen 4 to the peripheral direction and provided above the upper surface thereof. A template 16 is provided on the lower surface of the polishing object fixing plate 14,
An object to be polished W such as a wafer is held via the template 16. Reference numeral 18 denotes a polishing shaft end flange provided at a lower end of the polishing shaft 20 and located at a predetermined interval above the workpiece fixing plate 14.

Reference numeral 22 denotes a pressure chamber provided between the polishing object fixing plate 14 and the polishing shaft end flange 18. The pressure chamber 22
Is composed of a pressure chamber side wall 24 formed of a member (having a constant or higher spring constant) which can expand and contract in the vertical direction and has a slight rigidity in the horizontal direction, and a pressure chamber main body 22a surrounded by the side wall 24. It is configured. 28 and 30 are connection flanges. The connection flange 28 connects the upper end of the pressure chamber 22 to the lower surface of the polishing shaft end flange 18 while the connection flange 30
Serves to connect the lower end of the pressure chamber 22 to the upper surface of the polishing object fixing plate 14.

FIG. 2 is a sectional view showing an example of the pressure chamber 22.
FIG. 2 shows a mechanism for vacuum-sucking the wafer W.
A vacuum suction pipe 32 connected to the central portion of the polishing shaft end flange 28 and the central portion of the polishing object fixing plate 14 is provided, and the pipe 32 defines a space 36 provided on the lower surface of the suction base adapter 34. The suction pipe 38 is connected to a plurality of suction pipes 38 pierced inside the object-fixed plate 14 and opened to the processing surface 14a, and the pipe 32 is evacuated and the suction pipe 38 is evacuated. An object to be polished (such as a silicon wafer) W located on the processing surface 14a is vacuum-sucked. In FIG. 2, reference numeral 40 denotes an annular upper position stopper which is suspended from the lower surface of the connection flange 18, and numeral 42 is provided on the upper surface of the suction base adapter 34 so as to be engageable with the upper position stopper 40. This is the lower position lock. The upper position stopper
The inner engaging projection 44 projecting inward from the lower end of the fork 40 and the outer engaging projection 46 projecting outward from the upper end of the lower positioning stopper 42 are positioned. As shown in FIG. 2, when the polishing is performed, they are engaged with each other, but when the polishing is performed, they are separated from each other without being engaged with each other. The connection is established only by the chamber side wall 24.

The pressure chamber 22 exerts the most important effect in the present invention, and the processing load on any one of the processing surfaces 14a of the fixed plate 14 to be polished can be adjusted extremely uniformly, and the processing surface 14a Following the polishing cloth 6 adhered and fixed to the upper surface of the workpiece 4, the work surface 14a is provided with an object to be polished (for example, a silicon wafer) fitted to the positioning template 16 and adsorbed under reduced pressure as shown in FIG. The processed surface is brought into close contact with the upper surface of the polishing cloth 6 via a thin film of the abrasive 12, and the sliding polishing can be performed while applying a uniform load.

As described above, it is necessary that the pressure chamber side wall 24 has a constant or higher spring constant and generates a constant stress when expanding and contracting. In normal polishing, the degree of expansion and contraction of the pressure chamber side wall 24 partially varies along its circumference, and the degree of expansion and contraction is not uniform. However, since the expansion and contraction is small, the difference in spring compression force affects uniform polishing of the workpiece W. It doesn't get big enough.

The work piece fixing plate 14 is forcibly rotated at a constant speed about a polishing shaft 20 in a plane perpendicular to the polishing shaft 20, and is appropriately combined with the rotation of the polishing pad 6 and the platen 4 below. ,
When polishing a plurality of workpieces, it is necessary to control the polishing rate between the workpieces to be constant, and to control the polishing rate within the polishing surface to be constant even for the same workpiece. However, the pressure chamber side wall 24 needs to have sufficient strength to transmit the rotation of the polishing shaft 20.

A fluid such as air or water is press-fitted into the pressure chamber main body 22a from a fluid press-in hole 26 provided in the polishing shaft 20. The pressure in the pressure chamber 22 is appropriately adjusted depending on the object to be polished and the polishing step. For example, the pressure can be adjusted to about 0 to 2.0 kg / cm ² . The pressure in the pressure chamber 22 is applied to the workpiece W such as a wafer as a polishing load. When the polishing rate is increased, the pressure in the pressure chamber is adjusted so as to occupy a considerable portion of the polishing load, for example, 50% or more, and the operation is performed so that the flatness of the workpiece (for example, wafer) W becomes optimal. Is done.
For example, not only the silicon wafer, but the polishing of the object to be polished always requires one or two or three or more finishing steps,
At this time, except for the fluid pressure of the pressure chamber 22, the polishing is completed only by the spring compressive force of the pressure chamber side wall 24 and the own weight of the workpiece fixing plate 14, so that the load applied to the workpiece W becomes a desired minimum. It is preferable to design it.

The spring constant of the pressure chamber side wall 24 must be sufficiently small in order to adjust the processing load during such finishing. This is inconsistent with a sufficient strength for transmitting the rotational force to the workpiece fixed platen 14, so that the mechanical strength of the pressure chamber side wall 24 has an appropriate range.

As shown in FIG. 2, the pressure chamber side wall 24 is preferably made of metal, for example, stainless steel bellows, but is not limited to this example, and may be a piano wire, natural or synthetic rubber reinforced with various fibers, or the like.

When the strength of the pressure chamber side wall 24 is sufficiently reduced, in order to prevent the polishing object fixing plate 14 from receiving a force from the polishing pad 6 and remarkably abnormally deviating from a predetermined position, the pressure chamber side wall 24 is required.
It is effective to insert a cylindrical rigid body in contact with the side surface of the pressure chamber into or outside the pressure chamber side wall 24. However, when the processing pressure of the object to be polished (for example, a silicon wafer) is reduced, the torsional stress applied to the pressure chamber side wall 24 is also reduced.

The diameter dimension of the pressure chamber side wall 24 should not be too small as compared with that of the workpiece fixing plate 14. In addition, an appropriate position is set to transmit the rotational power of the polishing shaft end flange 18 to the workpiece fixing plate 14 without delay and to apply a uniform processing load to the lower surface of the workpiece fixing board 14.

Since the unevenness of the processing pressure cannot be avoided, it is also important to set the rigidity of the work piece fixing plate 14, especially when the polishing speed is high, it is preferable that the polishing load is mainly generated by the fluid pressure of the pressure chamber 22. . In consideration of the fact that the fluid pressure does not increase the deformation of the grinding object fixing plate 14 and the thermal deformation due to the heat generated during polishing, the grinding object fixing plate 14 is made of a material having a rigid body and a small coefficient of thermal expansion, for example, an alumina-based material. It is preferable to use ceramic.

FIGS. 3 to 5 show an example of an apparatus in which a plurality of (four) high-precision planar polishing apparatuses 2 are installed. 3 to 5, reference numeral 50 denotes a base, on which a gate 52 is slidably provided by a ball screw 54. 56 is a guide rail for guiding the gate 52. The gate 52 has a laterally inverted U-shape, and the upper plate 52a and the side plate 5
2b. A polishing shaft swing motor 58 is provided at the center of the upper plate 52a, and four grinding shafts 20 are provided at symmetrical positions around the swing motor 58. The polishing shaft 20 is oscillated by the oscillating motor 58 so as to approach or separate from the oscillating motor 58 during the polishing operation. Reference numeral 60 denotes a rotation motor attached to each polishing shaft 20. Reference numeral 62 denotes a sink frame provided on the upper surface of the front portion of the base 50, and the base 4 is provided therein. Abrasive 12 and polished slag, etc., which flow on the surface of the surface plate 4, flow out of the surface of the surface plate 4,
It is stored in the sink frame 62 and does not leak outside.
Reference numeral 64 denotes a receiving table provided on the upper surface of the rear portion of the base 50, and a receiving section 64a corresponding to the workpiece fixing plate 14 located below the polishing shaft 20 is provided. 66 is a motor for ball screw, 6
Reference numeral 8 denotes a motor for rotating the platen 4, and reference numeral 70 denotes a speed reducer.

 The operation will be described with the above configuration.

With the polishing shaft 20 raised, the gate 52 is moved onto the receiving table 64, and the processing surface 14a of the workpiece fixing plate 14 is ground.
After the object to be ground (for example, a silicon wafer) W is attracted to the substrate 52, the gate 52 is moved above the surface plate 4. Then, the polishing shaft 20 is lowered to set the workpiece W in contact with the surface of the polishing pad 6 of the platen 4. And the pressure chamber
A fluid such as air or water is press-fitted into 22 and set to an appropriate pressure. The polishing object 12 (silicon wafer) W is polished by rotating the platen 4 and simultaneously rotating and oscillating the polishing shaft 20 while the polishing agent 12 flows out of the pipe 10. In the case of polishing a silicon wafer, after the rough polishing is completed, finish polishing of several steps (about 1 to 4 steps) is performed, and the mirror polishing operation is completed. This finish polishing is usually performed by lowering the pressure in the pressure chamber 22, and is performed under extremely reduced pressure or without pressure from which the internal fluid is removed.

In the above-described embodiment, as an example of the means for attaching the object to be polished to the processing surface 14a of the object to be polished fixed plate 14, an example using vacuum suction is shown. As a means, it is also possible to adsorb by interposing water.

As a configuration of the pressure chamber 22 used in the present invention, a case having a side wall of a metal bellows is illustrated, but as described above, a piano wire, a natural or synthetic vulcanized rubber reinforced with various fibers can also be applied, It goes without saying that a pressure chamber having a side wall made of various other materials can be applied without departing from the spirit of the present invention.

As the polishing target of the apparatus of the present invention, mirror polishing of a silicon wafer has been described. However, the present invention may be applied to lapping, and the processing material is not necessarily limited to a silicon wafer, and is applicable to polishing of ceramic, glass, and metal. You can also.

(Effects of the Invention) As described above, according to the present invention, an evenly distributed processing load is generated on the processing surface of the object to be polished such as a wafer, and the frictional force between the object to be polished and the polishing part of the platen is held by the wafer. This has a great effect that the uneven load on the wafer processing due to the influence of the moment on the apparatus system can be reduced, and the flatness and parallelism of the processing surface of the workpiece can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a main part of the apparatus of the present invention, FIG. 2 is a sectional view of a pressure chamber, and FIGS. 3 to 5 are views showing an example in which four high-precision planar polishing apparatuses are installed. 3 is a top view, FIG. 4 is a front view, and FIG. 5 is a side view. 2. High precision flat polishing machine, 4 ... Surface plate, 6 ... Polishing unit, 8 ... Rotary shaft, 10 ... Pipe, 12 ... Abrasive, 14 ...
… Polishing object fixing plate, 16… Template, 18… Polishing shaft end flange, 20… Polishing shaft, 22… Pressure chamber, 24… Side wall, 28, 30… Connection flange, W… Polished Stuff.

Claims (4)

(57) [Claims] A surface plate provided with a polishing portion on an upper surface; a fixed object plate for fixing an object to be polished to a lower surface; a fixed plate attached to a lower end of a polishing shaft and provided above the fixed plate for the object to be polished. A polishing shaft end flange located at an interval, a pressure chamber to be provided between the workpiece fixing plate and the polishing shaft end flange and having a stretchable side wall, and to which air or water is added as a fluid. When the surface plate and the polishing shaft are rotated, the object to be polished fixed on the object to be polished is slid to press and slide on the polished part, and the surface to be polished is processed. It is possible to generate a distributed processing load and perform high-precision planar polishing, and adjust the fluid pressure applied to the pressure chamber and / or the spring constant of the side wall of the pressure chamber to adjust the processing load on the processing surface of the workpiece. So that the side wall of the pressure chamber is a metal bellows or It is made of natural rubber or synthetic rubber reinforced with any of anodized wire and various fibers or a combination thereof, and has almost the same outer shape or shape as the object to be polished at the connection part with the fixed plate for the object to be polished. High-precision planar polishing equipment. 2. A high-precision planar polishing apparatus according to claim 1, wherein a disk made of ceramics is used as said platen to be polished. 3. The high-precision planar polishing apparatus according to claim 2, wherein said ceramic is an alumina-based ceramic. 4. The method according to claim 1, wherein said metal bellows is a stainless steel bellows.
Item 6. The high-precision planar polishing apparatus according to any one of the above items.