JP2892191B2 - Wafer manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a single crystal,
The present invention relates to a method for manufacturing a wafer for forming a layer made of polycrystalline or amorphous silicon with a desired thickness and in a non-strained mirror state.

[0002]

2. Description of the Related Art Conventionally, a single crystal,
It has been extremely difficult to form a layer made of polycrystalline or amorphous silicon with a desired thickness and in a non-strained mirror state. As for this method, the present applicant has disclosed in
In Japanese Patent Application Publication No. 5 (1993) -5, after forming a stopper made of a material that is difficult to be mechanochemically polished on the surface of the substrate, a silicon layer is formed on the surface of the stopper, The present invention provides a method for producing a wafer in which a surface of the surface plate is polished without distortion while supplying an alkaline solution in which fine particles of high purity silica are dispersed.

FIG. 4 shows a silicon wafer obtained by bonding a supporting wafer 2 and an element wafer 4 by hydrogen bonding or the like. The element wafer 4 is a single crystal wafer 10.
A grid-like groove is formed on one surface (equivalent to a silicon substrate) at even intervals, and a stopper 8 is formed on the surface where the groove is formed to a uniform thickness. The silicon layer 6 (corresponding to a silicon layer) is formed by a chemical vapor deposition method. As the material of the stopper 8, a material such as oxide such as SiO ₂ , carbide such as SiC, and nitride such as Si ₃ N ₄ which is harder to be mechanically polished than silicon is used.

FIG. 5 shows a single crystal silicon layer 10 of the silicon wafer shown in FIG. 4 using a flat surface and a flat surface plate while supplying an alkaline solution in which fine particles of high-purity silica are dispersed. A large number of square silicon islands 10a are formed on the stopper 8 at equal intervals from each other. Elements such as transistors and diodes are formed on the silicon island 10a.

In manufacturing a wafer as shown in FIG. 5 above, if the wafer 2 and the wafer 4 are completely flat, as shown in FIG. The islands 10a can be manufactured accurately, but actually, the wafers 2 and 4
Since some of them are slightly curved as shown in FIGS. 6 to 8 (the curves are emphasized in FIGS. 6 to 8), the surface is flat and flat in such a case. When the single-crystal silicon layer 10 is gradually polished as shown in FIGS. 6 to 8 using the smooth platen 12, the outermost of the convex walls 8a of the stopper 8, as shown in FIG. Since the polishing is stopped by the convex wall 8a, there is a problem that the thickness of the silicon island 10a is not constant. An object of the present invention is to provide a method for manufacturing a wafer that can solve the above-described problems.

[0006]

According to the present invention, there is provided (A) a method in which one surface of a silicon substrate having a flat surface is made of a material which is less liable to be mechanochemically polished than silicon, and Forming a stopper that partially protrudes the stopper, (B) laminating a silicon layer on the silicon substrate having a thickness at least to fill the irregularities formed by the stopper, and (C) On the surface of a flat platen, using a polishing plate formed by attaching a large number of cells made of a rigid body via an elastic member, the surface of the large number of cells of the polishing plate and the surface of the silicon substrate are used. While supplying an alkaline solution in which an abrasive composed of fine particles of high-purity silica is dispersed between the other surface and the relative pressure movement of the polishing plate and the silicon substrate, the silicon Characterized by comprising a plate and a polishing step of mirror polishing.

[0007] The silicon substrate may be monocrystalline, polycrystalline or amorphous silicon.

[0008] In this specification, the rigid body refers to a member made of a material having a higher hardness than the surface to be polished of the wafer to be polished.

[0009]

According to the method of manufacturing a wafer according to the present invention, the silicon substrate is polished from the other surface in the polishing step because a large number of rigid cells are attached to the platen via the elastic member. At this time, polishing is performed until the cell comes into contact with the stopper while slightly moving up and down along the shape of the surface to be polished. Therefore, polishing is performed along the shape of the silicon substrate on which the stopper is formed, and even when the silicon substrate and the silicon layer are curved, the silicon is formed of silicon having a certain thickness on the silicon layer on the silicon layer. A layer is formed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, a polishing apparatus used in the polishing step will be described with reference to FIGS.

In FIG. 1, reference numeral 14 denotes an upper surface plate, and 16 denotes a lower surface plate, both of which have a disk shape, and their opposing surfaces are formed flat. The support shafts 18 and 20 connected to the respective platens 14 and 16 are connected to driving means (not shown) so as to be rotatable around the axis, and the support shaft 18 can be moved up and down in the vertical direction. . Upper surface plate 1
The ball bearing 17 is arranged between the support shaft 4 and the support shaft 18.

A carrier resin (template) 22 is fixed to an outer peripheral portion of a lower surface of the upper stool 14. A silicon wafer 24 exactly the same as the silicon wafer shown in FIG. The upper surface of the upper platen 14 is water-bonded to the lower surface of the upper platen 14.

A disc-shaped sponge rubber (corresponding to an elastic member) 26 is adhered and fixed to the upper surface of the lower stool 16. The sponge rubber 26 is made of rubber, an elastomer resin foam, or the like.

On the upper surface of the sponge rubber 26, a large number of square plate-shaped ceramic cells 28 are formed as shown in FIG.
In plan view, they are fixedly arranged radially from the center of the circle and at a predetermined interval from each other. This ceramic cell 28 is made of Al ₂ O ₃ or the like. The length L1 of one side of the ceramic cell 28 is equal to the length L2 of one side of the square recess 8b of the stopper 8 of the silicon wafer 24, which is defined between the convex walls 8a formed in a grid. (See FIG. 4) and larger than 1 of L2.
It is formed smaller than 000 times.

On the upper surfaces of the ceramic cells 28, urethane pads 30 are adhered. This urethane pad 3
0 is for adjusting the polishing amount by the ceramic cell 28, and is not necessarily provided.

The above-mentioned lower platen 16, sponge rubber 26 and ceramic cells 28 constitute a polishing plate.

Next, the stopper forming step will be described. In the wafer 24 shown in FIG. 4, as described above, a lattice-like groove is formed on one surface of the single crystal wafer 10,
It is formed at equal intervals by photolithography and selective etching. Thereafter, the stopper 8 is formed to a uniform thickness on the surface where the groove is formed. As a material of the stopper 8, a material such as oxide such as SiO ₂ , carbide such as SiC, and nitride such as Si ₃ N ₄ which is harder to be mechanically polished than silicon is used.

Next, the laminating step will be described. FIG.
As described above, the polysilicon layer 6 is laminated on the surface of the stopper 8 by the CVD device in the wafer 24 shown in FIG. The silicon layer 6 to be laminated may be single crystal silicon or amorphous silicon. The thickness of the silicon layer 6 to be laminated is set to a thickness at which at least the unevenness formed by the stopper 8 is filled.

Next, the polishing step will be described. First,
As shown in FIG. 1, the wafer 24 shown in FIG.
The supporting wafer 2 is fixed to the lower surface of the upper stool 14 by water bonding.

The lower platen 16 is rotated about the axis, while the upper platen 14 is rotated about the axis in a direction opposite to that of the lower platen 16, and is moved downward while being pressed. On the upper surfaces of the cells 28, the single crystal silicon layer 10 of the wafer 24 is friction-polished. At this time, between the urethane pad 30 and the silicon layer 10,
Polishing is performed while dropping an alkaline solution (PH10 to 11) in which an abrasive made of fine particles of high-purity silica having a particle size of about 0.02 μm is dispersed.

By this polishing step, the single crystal silicon layer 10 of the wafer 24 is removed except for the thickness (depth) of the stopper 8 protruding inward of the single crystal silicon layer 10, and as shown in FIG. As shown, a large number of silicon islands 10a having a square shape in plan view are formed between the convex walls 8a of the stoppers 8 formed in a lattice shape.

When the wafer 24 is polished, the ceramic cells 28 are connected to the lower platen 16 via the sponge rubber 26.
When the wafer 24 is curved as shown in FIG. 3 and the surface to be polished is curved as shown in FIG. 3, the ceramic cells 28... The entire surface to be polished is uniformly mirror-polished without distortion.

Therefore, according to the above-described wafer manufacturing method, even when the single crystal wafer 10 and the polysilicon layer 6 have a curvature, the single crystal wafer
0 can be accurately polished while leaving the thickness of the stopper 8 protruding to the inside of the single crystal wafer 10. By adjusting the thickness of the stopper 8 formed in the stopper forming step, the polysilicon layer 6 can be formed. A layer made of single-crystal wafer 10 and made of unstrained silicon having a desired thickness can be formed thereon. For this reason, even when the silicon substrate is slightly warped or curved, it is possible to manufacture a wafer on which a layer made of silicon having a certain thickness is formed by using the silicon substrate, thereby dramatically increasing the yield of wafer manufacturing. Can be improved.

As described above, the length L1 of one side of the ceramic cells 28 is larger than the length L2 of one side of the recess 8b of the stopper 8 (see FIG. 4). … Is the convex wall 8a and the convex wall 8
a and the silicon island 1
0a ... will not be lost.

In the above-mentioned polishing apparatus, the lower platen 16 is used as a polishing plate. However, the upper platen 14 may be used as a polishing plate. It may be.

Further, the elastic member is not limited to the sponge rubber as described above, and may be any material having an elasticity capable of moving up and down by following cells according to the surface shape of the wafer during polishing.

Further, the arrangement of the cells is not limited to that shown in FIG. 2, and various modifications are possible, for example, arrangement in a lattice, and the shape of the cells themselves is also round. , Triangles and various other shapes are possible.

[0028]

As described above, according to the present invention, one surface of a silicon substrate having a flat surface is made of a material which is less liable to be mechanochemically polished than silicon, and is provided on the inner side of the silicon substrate. Forming a stopper that partially protrudes toward the stopper, a step of forming a stopper, and a step of stacking, on the silicon substrate, a silicon layer having a thickness to fill at least the unevenness formed by the stopper, a stacking step, On the surface of the surface plate, using a polishing plate obtained by attaching a large number of cells made of a rigid body via an elastic member, the surface of the large number of cells of the polishing plate and the other surface of the silicon substrate are connected. In the meantime, while supplying an alkaline solution in which an abrasive composed of fine particles of high-purity silica is dispersed,
Since the wafer is manufactured from the polishing step of mirror-polishing the silicon substrate by the relative pressing movement of the polishing plate and the silicon substrate, even if the silicon substrate and the silicon layer are curved, the silicon substrate is Can be accurately polished while leaving only the thickness (depth) of a stopper protruding to the inside of the silicon substrate. By adjusting the thickness of the stopper formed in the stopper forming step, A layer made of a silicon substrate having a desired thickness and having no distortion can be formed.

[Brief description of the drawings]

FIG. 1 is a side view showing a polishing apparatus according to a polishing step.

FIG. 2 is a plan view showing an example of an array of rigid cells.

FIG. 3 is a side view showing a state during polishing of the wafer by the polishing plate.

FIG. 4 is a side view showing a wafer on which a stopper is formed (before polishing).

FIG. 5 is a side view showing a wafer having a stopper formed (after polishing).

FIG. 6 is a side view showing a wafer on which a stopper has been formed (before polishing).

FIG. 7 is a side view showing a wafer on which a stopper is formed (during polishing).

FIG. 8 is a side view showing a wafer on which a stopper has been formed (after polishing).

[Explanation of symbols]

 6 Silicon layer 8 Stopper 8a Convex wall 10 Silicon substrate 16 Surface plate 26 Elastic member 28 Cell

Claims (1)

(57) [Claims] (A) A stopper is provided on one surface of a silicon substrate having a flat surface, the stopper being made of a material that is less liable to be mechanochemically polished than silicon, and partially protruding toward the inside of the silicon substrate. Forming a stopper; (B) laminating a silicon layer on the silicon substrate at a thickness to fill at least the irregularities formed by the stopper; and (C) forming a flat surface plate. On the surface, using a polishing plate obtained by attaching a number of cells made of a rigid body via an elastic member, between the surface of the number of cells of the polishing plate and the other surface of the silicon substrate, A polishing step of mirror-polishing the silicon substrate by relatively moving the polishing plate and the silicon substrate while supplying an alkaline solution in which an abrasive made of fine particles of high-purity silica is dispersed; Wafer manufacturing method characterized by comprising a.