JP2892190B2 - 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.

In the wafer 2 shown in FIG. 10, a large number of stoppers 6 are formed on a silicon substrate 4 so as to be spaced apart from each other by a fixed distance in a straight line direction and a direction perpendicular thereto, and silicon is covered so as to cover the stoppers 6. The layer 8 is formed by a chemical vapor deposition method. In FIG. 1, reference numeral 10 denotes a surface plate having a flat and smooth surface.

The surface 10a of the surface plate 10 and the silicon layer 8
Between the surface plate 10 and the wafer 2 while dropping an alkaline solution in which fine particles of high-purity silica are dispersed, the surface 10a of the surface plate 10
When the silicon layer 8 is polished until it comes into contact with (FIG. 11)
), A silicon layer 8 a having a uniform thickness is formed between the stoppers 6.

However, as described above, the silicon layer 8
When forming a, the wafer 2 (the surface of the silicon substrate 4) may be somewhat curved as shown in FIG. 10 (the curvature is emphasized in FIG. 10). As shown in FIG. 12, there is a problem that the thickness of the formed silicon layer 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, (A) at least one surface of a silicon substrate having a flat surface is provided.
A stopper forming step of forming a stopper made of a material that is difficult to be mechanochemically polished compared to silicon,
(B) a laminating step of laminating a silicon layer having a thickness at least to fill the unevenness formed by the stopper on the silicon substrate; and (C) a large number of rigid bodies formed on the surface of the flat surface plate. A cell is used with a polishing plate attached via an elastic member. Between the surfaces of the plurality of cells of the polishing plate and the silicon layer laminated in the laminating step, fine particles of high-purity silica are used. A polishing step of mirror-polishing the silicon layer by relative pressure movement between the polishing plate and the silicon layer while supplying an alkaline solution in which the polishing agent is dispersed.

[0007] In this specification, a rigid body refers to a member made of a material having a higher hardness than the surface to be polished of a wafer to be polished.

[0008]

According to the method of manufacturing a wafer according to the present invention, since a large number of cells made of a rigid body are attached to the surface plate via the elastic member, the silicon layer laminated in the laminating step is removed in the polishing step. When polishing, 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, the stacked silicon layers are polished along the shape of the silicon substrate, and a silicon layer having a certain thickness is formed from the surface of the silicon substrate even when the silicon substrate is curved.

[0009]

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.

FIG. 1 is a side view showing a polishing apparatus. In FIG. 1, reference numeral 12 denotes an upper platen and 14 denotes a lower platen, both of which are disc-shaped, and their opposing surfaces are formed flat. I have. The support shaft 1 connected to each of the surface plates 12 and 14
Reference numerals 6 and 18 are connected to driving means (not shown) so as to be rotatable around an axis, and furthermore, the support shaft 16 is capable of moving up and down. A ball bearing 15 is provided between the upper stool 12 and the support shaft 16.

A carrier resin (template) 20 is fixed to an outer peripheral portion of a lower surface of the upper platen 12. A wafer 2 shown in FIG.
2 is arranged such that its upper surface is water-bonded to the lower surface of the upper stool 12.

A disc-shaped sponge rubber (corresponding to an elastic member) 24 is bonded and fixed to the upper surface of the lower stool 14. The sponge rubber 24 is made of rubber, an elastomer resin foam, or the like.

On the upper surface of the sponge rubber 24, a large number of square plate-shaped ceramic cells 26 are arranged as shown in FIG.
It is fixed and arranged radially from the center of the disk in plan view. The ceramic cell 26 is made of Al ₂ O ₃ or the like. The length L1 of one side of the ceramic cell 26 is larger than the distance L2 between stoppers formed on the wafer 22 (see FIGS. 5 and 6).
And it is formed smaller than 1000 times of L2.

On the upper surfaces of the ceramic cells 26, urethane pads 28 are adhered. This urethane pad 2
Reference numeral 8 is for adjusting the amount of polishing by the ceramic cell 26, and may not necessarily be provided.

The above-mentioned lower platen 14, sponge rubber 24 and ceramic cells 26 constitute a polishing plate.

Next, a stopper forming step will be described. As shown in FIGS. 4 and 5, on the surface of the silicon substrate 32, stoppers 34 having the same thickness as the silicon layer to be formed and insulating portions 36 if necessary are formed. In the present embodiment, as shown in FIG. 5, the stoppers 34 are arranged so as to be spaced apart from each other by a fixed distance in a straight line direction and a direction perpendicular thereto in a plan view. A large number of square-shaped concave spaces 34c (see FIGS. 4 and 5) in a plan view are formed inside the.

As the silicon substrate 32, one having at least a surface portion made of single crystal silicon, polycrystal silicon or high-purity quartz is used.

As the material of the stoppers 34, oxides such as SiO ₂ , carbides such as SiC, Si ₃
Hard material is mechanochemical polishing than silicon, such as nitrides, such as N ₄ is used.

Next, the laminating step will be described. As shown in FIG. 6, a single crystal, polycrystalline or amorphous silicon layer 38 is laminated on the substrate 32 on which the stoppers 34 (and the insulating portions 36) are formed, using a CVD apparatus. The thickness of the silicon layer 38 to be laminated is at least a thickness that fills the irregularities formed by the stoppers 34 projecting from the surface of the substrate 32.

Next, the polishing step will be described. First,
As shown in FIG. 1, the wafer 22 shown in FIG.
The surface of the substrate 32 on which the silicon layer 38 is not formed is fixed to the lower surface of the upper stool 12 by water bonding.

The lower platen 14 is rotated about the axis, while the upper platen 12 is rotated about the axis in a direction opposite to that of the lower platen 14, and is moved downward by pressing. On the upper surfaces of the cells 26, the silicon layer 38 of the wafer 22 is friction-polished. At this time, polishing is performed while dropping an alkaline solution (PH10 to 11) in which an abrasive comprising fine particles of high-purity silica having a particle size of about 0.02 μm is dispersed between the urethane pad 28 and the silicon layer 38.

By this polishing step, all portions 38a (see FIG. 6) of the silicon layer 38 of the wafer 22 which exceed the height of the stoppers 34 are removed, and a certain amount is kept between the stoppers 34, 34 as shown in FIG. Is formed on which a silicon layer 38b having a thickness of 3 mm is formed.

When the wafer 22 is polished, the ceramic cells 26 are connected to the lower platen 14 via the sponge rubber 24.
3, the polished surface of the wafer 22 is
, The ceramic cells 26 move slightly up and down along the curvature of the surface to be polished, and the entire surface to be polished is uniformly mirror-polished without distortion.

Therefore, according to the above-described wafer manufacturing method, even when the silicon substrate 32 is curved, in the polishing step, the silicon layer 38 laminated in the laminating step is used.
Can be accurately polished to the height of the stopper 34, and by adjusting the thickness (height) of the stopper formed in the stopper forming step, the silicon substrate 32 can be polished.
An unstrained silicon layer having a desired thickness can be formed thereon. Therefore, the yield of the wafer to be manufactured can be significantly improved.

As described above, the length L1 of one side of the ceramic cells 26 is larger than the interval L2 (see FIG. 5) between the stoppers 34 formed on the wafer 22, so that the length L1 during polishing is reduced. Ceramic cell 26 ...
However, the silicon layer 38b between the stoppers 34 and 34 is not entangled between the stoppers 34 and 34.

The shape of the stopper formed on the silicon substrate is not limited to the one described above, and may be, for example, a shape as shown in FIG. Stopper 40 shown in the figure, the surface of the silicon single crystal substrate 32 is thermally oxidized to form a SiO ₂ layer, by etching the SiO ₂ layer, a stopper 40 such that a portion 32a of the substrate 32 is exposed Is formed. The stopper 40 is stepped, and includes a lower portion 40a and an upper portion 40b. The silicon layer 38 is formed by crystal growth from the exposed portion 32a of the substrate 32 by a selective epitaxial method. When the stopper shape is set as described above, the polished silicon layer 38a has a shape as shown in FIG.

In the above-mentioned polishing apparatus, the lower platen 14 is used as a polishing plate. However, the upper platen 12 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 following the cell 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 grid, and the shape of the cells themselves is also round. , Triangles and various other shapes are possible.

[0030]

As described above, according to the present invention, a stopper is formed on at least one surface of a silicon substrate having a flat surface, the stopper being made of a material which is harder to be mechanochemically polished than silicon. Step, the silicon substrate, a silicon layer having a thickness to fill at least the unevenness formed by the stopper is laminated, a laminating step, 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, a high height is provided between the surface of the many cells of the polishing plate and the silicon layer laminated in the laminating step. A wafer is manufactured from a polishing step of mirror-polishing the silicon layer by the relative pressure movement of the polishing plate and the silicon layer while supplying an alkaline solution in which an abrasive composed of fine silica particles is dispersed. Even when the silicon substrate has a curvature, the silicon layer laminated in the laminating step can be accurately polished to the height of the stopper in the polishing step, and the thickness (height) of the stopper formed in the stopper forming step By adjusting (2), a non-strained silicon layer having a desired thickness can be formed on the silicon substrate.

[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.

FIG. 5 is a plan view of the wafer of FIG. 4;

FIG. 6 is a side view showing a wafer on which a stopper is formed and a silicon layer is laminated (before polishing).

FIG. 7 is a side view showing a state after polishing of the wafer of FIG. 6;

FIG. 8 is a side view showing a wafer (before polishing) on which a stopper is formed and a silicon layer is stacked.

FIG. 9 is a side view showing a state after polishing of the wafer of FIG. 8;

FIG. 10 is a side view showing a wafer and a surface plate before polishing.

FIG. 11 is a side view showing a wafer and a surface plate during polishing.

FIG. 12 is a side view showing the wafer after polishing.

[Explanation of symbols]

 14 surface plate 24 elastic member 26 cell 32 silicon substrate 34 stopper 38 silicon layer 40 stopper

Claims (1)

(57) [Claims] (A) forming a stopper on at least one surface of a silicon substrate having a flat surface, which is made of a material that is less susceptible to mechanochemical polishing than silicon; and (B) the silicon substrate. A stacking step of stacking at least a silicon layer having a thickness to fill in the unevenness formed by the stopper; and (C) forming a large number of cells made of a rigid body on the flat surface of the platen, forming an elastic member. Using a polishing plate attached through the intermediary, between the surface of the plurality of cells of the polishing plate and the silicon layer laminated in the laminating step, an abrasive comprising fine particles of high-purity silica is dispersed. A polishing step of mirror-polishing the silicon layer by relative pressure movement between the polishing plate and the silicon layer while supplying the alkaline solution. Manufacturing method.