JPH06155253A - Manufacture of wafer - Google Patents

Abstract

PURPOSE:To reduce the chips which are generated much at the end and improve yield by working the end of an orientation flat part. CONSTITUTION:After an ingot (silicon rod) 1 is ground to a columnar form, an orientation flat part 1a is formed on the ingot 1. Then, the end 1b of the orientation flat part 1a is polished by a polisher 3. Then, the ingot 1 is cut to each wafer, and the circumference of the wafer is bevelling-worked. After the orientation flat part is polished again by a polisher, the wafer is subjected to lapping work. Accordingly, the cut of the orientation flat part during the transport of the wafer can be prevented by correcting the discontinuous curved line part on the boundary between the orientation flat part 1a as the reference surface of the crystal orientation and other circumferential parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wafer used in a semiconductor device.

[0002]

2. Description of the Related Art FIG. 9 is a flowchart showing a conventional wafer manufacturing method. First, an ingot is generated by the pulling method, the crystal orientation is confirmed and the specific resistance is checked, and then the outer periphery is ground to shape the cross section of the ingot into a perfect circle. Then, using a cup-shaped diamond grindstone, orientation flat processing is performed to form a reference plane of the crystal orientation of the wafer. This orientation flat portion is mainly used as a mask position reference in the manufacture of semiconductor devices. After washing this ingot, it is cut into a predetermined thickness by a circumferential blade type cutting machine. After further cleaning, beveling processing (chamfering processing) is performed on the outer peripheral corners with the beveling machine shown in FIG. In this beveling machine, a wafer W cut into a predetermined thickness is held horizontally by a vacuum chuck 11 and a drum-shaped ordinary round grindstone 12 is horizontally rotated to chamfer the outer peripheral portion of the wafer W. It is a thing.

After that, both sides are lapped, etched and mirror-polished. Taking a φ6 ″ Si wafer as an example, the thickness is 0.625 mm and the orientation flat portion has a length of 45 to 45 mm.
Finished to 50mm. The shape of this wafer is shown in FIG.
11 (a) is a plan view of the wafer, and FIG. 11 (b) is a side view. In FIG. 11, assuming that the radius of the wafer is a and the length of the orientation flat portion is b, the angle α formed by the orientation flat line and the tangential line of the circumference in the vicinity of the I portion which is the end portion of the orientation flat portion is as follows. It is calculated by the formula. α = sin ⁻¹ (b / 2a) However, (π / 2) <α <π Substituting a general φ6 ″ Si wafer value, α≈160 °.

[0004]

However, in the wafer manufactured by the conventional method, the peripheral portion is smoothly ground, but the portion I shown in FIG. 11 is not subjected to the corner treatment (α≈160).
°), it is conveyed to the subsequent processing process while being square. Then, during this transportation, chipping (chipping) is likely to occur at the portion I during mounting on a jig or during processing such as lapping and polishing. Normally, the grain size of the abrasive grains used in lapping and polishing is about a few μm at the maximum, whereas grains produced by such chipping are a few hundred μm.
It can be a degree. If these particles are contained in the processing liquid, the surface of other wafers will be seriously damaged, and the productivity will be adversely affected. The present invention has been made in view of such circumstances, and provides a wafer manufacturing method capable of preventing chipping of a wafer by adding a step of processing an end portion of an orientation flat portion. To aim.

[0005]

A method of manufacturing a wafer according to the present invention comprises a first step of grinding an ingot into a cylindrical shape,
A second step of forming an orientation flat portion on the ingot that has undergone the first step, a third step of cutting the ingot that has undergone the second step into wafers, a fourth step of beveling the circumference of the wafer, and a fourth step. A wafer manufacturing method including a fifth step of lapping a wafer that has passed through the steps, wherein the orientation is provided between the second step and the third step and / or between the fourth step and the fifth step. It is characterized by including a step of polishing the end portion of the flat portion.

[0006]

In the present invention, the curve discontinuity at the boundary between the orientation flat portion, which is the reference plane of the crystal orientation, and the other circumferential portion is corrected, so that the jig is transferred to the jig during the subsequent transportation. It is possible to prevent chipping that occurs during mounting of the product or during processing such as lapping and polishing.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a flowchart showing a wafer manufacturing method according to the present invention. First, an ingot is generated by the pulling method, the crystal orientation is confirmed and the specific resistance is checked, and then the outer periphery is ground to shape the cross section of the ingot into a perfect circle. Then, using a cup-shaped diamond grindstone, orientation flat processing is performed to form a reference plane of the crystal orientation of the wafer. This orientation flat portion is mainly used as a mask position reference in the manufacture of semiconductor devices.

After this orientation flat processing, the processing described later is performed by the apparatus shown in FIG. 2 (main processing 1) and cleaning is performed. Next, this ingot is cut to a predetermined thickness with a circumferential blade type cutting machine, washed, and then chamfered at the outer peripheral corners with a beveling machine shown in FIG. In this beveling machine, a wafer W cut into a predetermined length is held horizontally by a vacuum chuck 11 and a drum-shaped normal round grindstone 12 is horizontally rotated to perform a beveling process on the outer peripheral portion of the wafer W ( Chamfering).

After this beveling process, the process described later is performed by the apparatus shown in FIG. 3 (main process 2). After this, double-sided lapping, etching and mirror polishing are applied,
Taking a 6 ″ Si wafer as an example, the thickness is 0.625 mm and the orientation flat portion length is 45 to 50 mm. The shape of this wafer is shown in FIG. 4. FIG. 4 (a) is a plan view of the wafer, and FIG. (b) is a side view.

FIG. 2 is a perspective view showing an apparatus used for the main processing 1 in the method of the present invention and an implementation state thereof. In the figure, 1 is a cylindrical silicon rod, a part of the side surface of which is subjected to orientation flat processing to form an orientation flat portion 1a. Two cylindrical rollers 2 and 2 are arranged parallel to the crystal axis of the silicon rod 1. A film-like polisher 3 to which abrasive grains are adhered is wound and wound between the rollers 2 and 2, and is rotated in the same direction as indicated by an arrow. Further, a polishing liquid nozzle S for spraying a polishing liquid containing polishing abrasive grains is installed with its spray port facing the polishing position.

In the apparatus having the above-described structure, the rollers 2 and 2 are rotated in the arrow direction to slide the polisher 3 on the edge portion 1b of the silicon rod 1, the polishing liquid is sprayed from the polishing liquid nozzle S, and the silicon is further added. The edge 1b is polished by moving the rod 1 in the direction of the hollow arrow. Instead of the polisher 3, a polisher having pores may be used to supply a working liquid containing abrasive grains for polishing. The angle β may be set under appropriate conditions.

3A and 3B are schematic views showing an apparatus used for the main processing 2 in the method of the present invention and an implementation state thereof. FIG. 3A is a plan view and FIG. 3B is a side view. W in the figure is
The wafer is a wafer on which an orientation flat portion W _a is formed and is beveled, and is held horizontally by the vacuum chuck 5. The two rollers crystal axis parallel to cylindrical wafer W 4, 4 is disposed so as to be in contact with both edges W _b, W _b of the orientation flat portion W _a. A polishing pad is attached to the rollers 4 and 4 so as to rotate in the opposite direction as indicated by an arrow. Further, the position can be adjusted so as to be in contact with both edge portions W _b , W _b .

In the apparatus having the above-described structure, the rollers 4 and 4 are rotated in the arrow direction, and the wafer W is pressed against the rollers 4 and 4, whereby the edge portion W _b is polished.

FIGS. 5 and 6 are perspective views showing the second and third devices used for the main processing 1 in the method of the present invention and the state of implementation thereof. In the figure, 1 is a cylindrical silicon rod, a part of the side surface of which is subjected to orientation flat processing to form an orientation flat portion 1a.

In FIG. 5, a cup grindstone 6 conventionally used for orientation flat processing is arranged so as to contact one edge portion 1b of the orientation flat portion 1a. The cup-shaped grindstone 6 has a configuration in which the mounting angle (rotational axis angle) can be changed to change the polishing angle. In such an apparatus, while rotating the cup-shaped grindstone 6, the silicon rod 1 is moved in the outline arrow direction to polish the edge portion 1b. A plurality of cup-shaped grindstones having different mounting angles may be mounted.

In FIG. 6, a plurality of cylindrical rollers 7, 7, 7 are arranged so that their mounting angles (rotation axis angles) are different so as to contact one edge portion 1b of the orientation flat portion 1a. A polishing pad is wound around the surfaces of the rollers 7, 7, 7.

The chipping test of the wafer manufactured by the method of the present invention was conducted by the tester shown in FIG. Figure 7
(a) shows a side view and FIG. 7 (b) shows a plan view. 17 in the figure
Is a quartz disc having a hardness higher than that of the wafer W.
In the drawing, two guides 18a, 18b are installed in the left-right direction at intervals slightly larger than the diameter of the wafer W. guide
18a is fixed, and the guide 18b can adjust its position in the direction indicated by the arrow according to the diameter of the wafer W. Then, at the center of the space between the guides 18a and 18b, two pillars are arranged at a space slightly larger than the thickness of the wafer W.
19, 19 are installed. A pin 20 is penetrated at a predetermined height position between these two columns 19 and 19. When the wafer W is inserted into the space restricted on all sides in such a manner that its plane is vertical, the wafer W is supported at the predetermined height.

When the pin 20 is removed in this state, the wafer W falls along the guides 18a and 18b. At this time, since the quartz disk 17 has a higher hardness than the wafer W, the wafer W is chipped without the quartz disk 17 being chipped. The processing conditions for the wafer W are as follows. Material 6 inch Si wafer (100) Resistivity 10
Ωcm P type belt grindstone feeding speed 3m / min Abrasive grain size # 6000 Pressing force About 400gf / cm ² Rod extrusion speed 50cm / min

As shown in FIG. 4, the center point of the orientation flat portion is A and the edge portion is B as shown in FIG. 4, and four points are taken at intervals of about 45 ° from six points A, B, C, D, E and F.
It is a point. If the number of chipping occurrences at point F is 1,
FIG. 8 shows a bar graph showing the number of chipping occurrences as a relative value to this. The outline is the result of the conventional method, and the shaded area is the result of the method of the present invention. In both the method of the present invention and the conventional method, the value at the point B is the highest, but the value of the conventional method was 8 times that of the point F, but the method of the present invention improved to about 3 times. It can be seen that the number of chipping occurrences is reduced by carrying out the method of the present invention in this way.

The above results are the results when only the main machining 2 is carried out, and the same effect is obtained when only the main machining 1 is carried out, and a better effect is obtained when the main machining 1 and 2 are used together. Is obtained.

[0021]

As described above, the method of manufacturing a wafer according to the present invention has a step of processing the end portion of the orientation flat portion, so that the chipping that frequently occurs at this portion is reduced and the yield is improved. That is, the present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a flowchart showing a wafer manufacturing method according to the present invention.

FIG. 2 is a perspective view showing an apparatus used for carrying out main processing 1 in the method of the present invention.

FIG. 3 is a perspective view showing an apparatus used for carrying out main processing 2 in the method of the present invention.

FIG. 4 is a plan view and a side view showing a wafer obtained by the method of the present invention.

FIG. 5 is a perspective view showing a second embodiment of the apparatus used for carrying out the main processing 1 in the method of the present invention.

FIG. 6 is a perspective view showing a third embodiment of the apparatus used for carrying out the main processing 1 in the method of the present invention.

FIG. 7 is a schematic diagram showing a tester that performs a chipping property test.

FIG. 8 is a bar graph showing the number of chipping occurrences.

FIG. 9 is a flowchart showing a conventional wafer manufacturing method.

FIG. 10 is a schematic view showing a beveling machine.

FIG. 11 is a plan view and a side view showing a wafer obtained by a conventional method.

[Explanation of symbols]

W wafer S polishing liquid nozzle 1 silicon rod 1a, W _a orientation flat portion 1b, W _b edges 2,4, 6,7 roller 3 polishers 5 vacuum chuck

Claims (1)

[Claims] 1. A first step of grinding an ingot into a cylindrical shape, a second step of forming an orientation flat portion on the ingot subjected to the first step, and a third step of cutting the ingot into a wafer after the second step. A wafer manufacturing method including a fourth step of beveling the circumference of the wafer, and a fifth step of lapping the wafer that has undergone the fourth step, wherein the wafer manufacturing method includes a step between the second step and the third step; /
Alternatively, a method of manufacturing a wafer, including a step of polishing an end portion of the orientation flat portion between the fourth step and the fifth step.