JPS61192475A - Tool for polishing substrate - Google Patents

Abstract

PURPOSE:To float a semiconductor substrate and a crystal substrate to be polished from a polishing tool so that they are held in a non-contact state by preventing a processing liquid from percolating by filling the inclined faces of V-shaped grooves to produce a dynamic pressure in the V-shaped grooves. CONSTITUTION:A processing liquid 23 including isolated grains 22 dispersed therein is supplied between a substrate 16 and a polishing tool 11 and the tool 11 is relatively moved toward the left hand with respect to the substrate 16. Since the surface of V-shaped grooves 18 is filled with a molten layer 20, a processing liquid 23 is prevented from percolating from inclined faces 19 into the inside of the polishing tool 11 to produce a regular dynamic pressure in the V-shaped grooves 18. Thus, the substrate 16 is floated from the surface of the tool 11 to the position where the dynamic pressure and a processing pressure are balanced with each other so that the substrate 16 is held in a non-contact state. On the other hand, since nonwoven fabrics 14 are exposed as they are on flat portions 17, isolated grains 22 are liable to be captured by pores 15 and among textiles of resin 12 and furthermore the processing liquid 23 is percolated thereto, the surface of the substrate 16 is polished with excellent efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polishing tool for highly accurate surface polishing of semiconductor substrates and crystal substrates by mechanochemical lapping.

<Conventional technology> Conventionally, semiconductor substrates made of silicon, gallium, arsenic, etc., or sapphire, gadolinium, gallium, garnet (G
One way to remove the damaged layer by surface polishing a crystal substrate such as GG) is to overlay the substrate on a nonwoven fabric made of resin fibers such as polyester hardened with polyurethane resin, etc.
Mechanochemical wrapping is known in which a nonwoven fabric and a substrate are rubbed together to achieve a mirror finish while a processing liquid in which fine silica particles are suspended in an alkaline aqueous solution is supplied between them.

This mechanochemical wrapping combines the mechanical grinding action of fine silica particles and the chemical erosion action of an alkaline aqueous solution, making it possible to achieve a finish with high efficiency and minimal processing damage, but it also causes a large amount of wear on the nonwoven fabric. In addition to high exchange purity, chemical erosion is likely to increase due to frictional heat during polishing, and strict process control and skilled techniques are required to obtain a stable and high-quality machined surface.

Therefore, by applying the principle of hydrodynamic bearing, the substrate is floated above the surface of the nonwoven fabric, and the substrate and the nonwoven fabric are kept in a non-contact state to prevent the generation of frictional heat. A method of surface grinding has been proposed in Japanese Patent Publication No. 54-30800.

As shown in FIG. 3 showing the processing principle of this non-contact lapping, the surface of the polishing tool 2 on which the substrate 1 is stacked has a flat part 3 facing the substrate 1, and a polishing tool 2 for the substrate 1. direction perpendicular to the relative movement direction (left direction in the figure) (
V-grooves 4 extending in a direction perpendicular to the plane of the drawing are alternately formed along the relative movement direction. ■In the groove portion 4, an inclined surface 5 for generating dynamic pressure is formed, and the depth of the groove gradually becomes deeper toward the direction of relative movement of the polishing tool 2 with respect to the substrate 1, and between the substrate 1 and the polishing tool 2. A machining liquid 8 in which free abrasive grains 6 are dispersed in a corrosive liquid 7 is supplied.

Therefore, when the polishing tool 2 is moved relative to the substrate 1 in the left direction in the figure, the pressure distribution of the working fluid 8 along the relative movement direction of the polishing tool 2 at this time is shown in FIG. 4. Dynamic pressure is generated by the machining fluid 8 in the groove 4, and the substrate 1
floats relative to the polishing tool 2 at a position where this dynamic pressure and processing pressure are balanced. Then, the surface of the substrate 1 is processed by the collision between the substrate 1 and the free abrasive grains 6 due to the flow of □ processing "e8" and the chemical action of the processing liquid 8.

<Problems to be Solved by the Invention> When non-contact lapping is performed using an abrasive tool made of non-woven fabric, the permeability of machining fluid is generally good because non-woven fabric has numerous pores; As a result, the generation of dynamic pressure in the V-groove tends to be insufficient, and as a practical matter, the substrate and the polishing tool often come into contact with each other.

On the other hand, when using a polishing tool made of urethane rubber, etc., which has almost no permeability to machining fluid, it is possible to generate sufficient dynamic pressure in the grooves, but it is possible to generate a sufficient amount of dynamic pressure in the grooves. Due to the poor retention of abrasive grains, the processing efficiency is significantly lower than that of a polishing tool made of non-woven fabric.

In view of the problems of the conventional polishing tools used in mechanochemical contactless lapping, it is an object of the present invention to provide a polishing tool that has high processing efficiency and can maintain a non-contact state with respect to the substrate.

Means for Solving the Problems> The polishing tool of the present invention moves relative to a substrate and flows a machining liquid in which free abrasive grains are dispersed between the tool and the substrate, thereby flattening the substrate. A polishing tool made of resin fiber nonwoven fabric, wherein V1JIt extending in a direction crossing the relative movement direction and a flat part facing the substrate are alternately arranged along the relative movement direction, and the The V-groove portion is formed with an inclined surface for generating dynamic pressure, which becomes deeper toward the relative movement direction of the polishing tool, and which causes the substrate to levitate from the polishing tool. It is characterized by a sealing treatment that prevents the penetration of machining fluid.

Effect> The resin fiber non-woven fabric is exposed on the flat part of the polishing tool facing the substrate, and free abrasive grains in the processing fluid are captured in the intertwined parts of the resin fibers, the pores, etc. The combined effect of the grinding action of the free abrasive grains and the chemical action of the processing fluid itself polishes the surface of the substrate with high efficiency. In addition, the sloped surface of the V-groove of the polishing tool is sealed, so there is almost no permeation of machining fluid, and therefore, sufficient dynamic pressure close to the theoretical value is generated in the groove due to the relative movement between the substrate and the polishing tool. Occur.

As a result, contactless lapping is ensured without the substrate coming into contact with the polishing tool.

Embodiment As shown in FIG. 1 showing the processing state of an embodiment of the polishing tool according to the present invention and FIG. 2 showing the enlarged structure of this 7iFFII tool, the polishing tool 11 is made of polyester fiber or the like. It is made of a nonwoven fabric 14 in which resin fibers 12 are three-dimensionally intertwined in a non-arranged manner and molded and solidified into a predetermined shape with a binder 13 such as polyurethane resin, and has numerous pores 15.
However, specific examples of the resin fibers 12 and binder 13 described above may of course be other than those exemplified. The surface of this polishing tool 11 has a substrate 16 to be flat-polished.
a groove portion 18 extending in a direction perpendicular to the direction of relative movement of the polishing tool 11 with respect to the substrate 16 (left direction in FIG. 1) (direction perpendicular to the plane of the paper in FIG. 1); are formed alternately along the relative movement direction. ■The groove part 18 has a polishing tool 11 for the substrate 16.
A slope surface 19 for generating dynamic pressure is formed in which the depth of the groove becomes gradually deeper toward the relative movement direction of
The surface of the groove 18 is heated, compressed and melt-molded at approximately 200° C. using a heater (not shown) having a shape corresponding to the groove 18, and the resin m fibers 12 and the binder 13 are melted together to form a molten layer 20 in which the pores 15 are sealed. It has a compressed overcrowded layer 21 on the surface and inside thereof, in which the pores 15 remain in a compressed state. As described above, in this embodiment, the inclined surface 19 is sealed by heating the surface of the V-groove portion 18. It also functions as a sealing process by forming it by means of other means.

When the machining liquid 23 in which free abrasive grains 22 are dispersed is supplied between the substrate 16 and the polishing tool 11, and the polishing tool 11 is moved relative to the substrate 16 in the left direction in FIG. Since the surface of the groove portion 18 is sealed with the molten layer 20, the machining fluid 23 flows from the inclined surface 19 into the polishing tool 11.
The substrate 16 floats above the surface of the polishing tool 11 and is held in a non-contact state at a position where this dynamic pressure and the processing pressure are balanced. Ru. On the other hand, in the flat part 17, the nonwoven fabric 14 is exposed as it is, and the free abrasive grains 22 are easily captured between the pores 15 and the resin fibers 12. Moreover, the machining fluid 23 permeates there. The surface of the substrate 16 is polished with high efficiency due to the collision between the substrate 16 and the free abrasive grains 22 due to the flow and the chemical action of the processing liquid 23 itself.

Incidentally, using the polishing tool of the present invention, a silicon single crystal substrate with a diameter of 3 inches was polished using a processing solution in which zirconium silicate with a particle size of 1 to 1.4 micrometers was suspended in an alkaline aqueous solution with a pH of 12. When polished at a processing pressure of 100 grams per square centimeter, a thickness of 15 micrometers can be polished per hour, similar to the one shown in Figure 3, and the urethane rubber has almost no permeability to the processing fluid. The polishing ability was slightly less than 8 times that using a polishing tool such as the above polishing tool. Also, $ side 1 of the processed side
1? :lk/l? n+avli9n peoplell11m*hj
This value was sufficiently smaller than that obtained when the T plate and the polishing tool were polished in contact with each other.

<Effects of the Invention> According to the present invention, sufficient dynamic pressure can be generated by sealing the grooves, and the flat part has excellent capture of loose abrasive grains, resulting in high machining efficiency. It is possible to achieve contactless wrapping.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the processing state of an embodiment of the polishing tool according to the present invention, and FIG. 2 is a diagram showing its structure. The enlarged view and FIG. 3 are cross-sectional views showing the processing state of conventional non-contact lapping, and FIG. 4 is a graph showing the distribution of dynamic pressure generated. Also, in the figure, 11 is a polishing tool, 12 is a resin fiber,
14 is a nonwoven fabric, 16 is a substrate, 17 is a flat part, 18 is a groove part, 19 is an inclined surface, 20 is a molten layer, 22 is a free abrasive grain, 2
3 is a processing fluid. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Tool position

Claims (1)

[Claims] A polishing tool formed of a resin fiber nonwoven fabric that moves relative to a substrate and flat-surface polishes the substrate by flowing a machining liquid with free abrasive particles dispersed between the substrate and the substrate, wherein the polishing tool moves in the direction of relative movement. V-groove portions extending in a direction intersecting with the substrate and flat portions facing the substrate are arranged alternately along the relative movement direction, and the V-groove portion has a groove deeper toward the relative movement direction of the polishing tool. an inclined surface for generating dynamic pressure that increases the depth and lifts the substrate from the polishing tool;
A tool for polishing a substrate, characterized in that the inclined surface is sealed to prevent penetration of the machining fluid.