JPH06190824A - Method for slicing compound semiconductor monocrystal wafer - Google Patents

Abstract

PURPOSE:To produce a wafer having no saw mark or having a high flatness and reduce a grinding amount in a lapping process by slicing a wafer. CONSTITUTION:An ingot 1 is sliced in a feed direction of the ingot 1 at right angles to a rotating direction of an inner diameter blade 3. When a wafer having a (100) plane is sliced off the ingot 1, the ingot is sliced in a direction <0 bar 11>+ or -10 deg. or <01 bar 1>+ or -10 deg.. In this manner, the wafer sliced off at this time is convex upward in the rotating direction of the inner diameter blade 3 and concave downward in the slicing direction. Upon completion of slicing, when the ingot 1 is retracted from top of the inner diameter blade to an opening of the inner diameter blade, an air flow is generated by the rotation of the inner diameter blade 3. Because the wafer is convex upward in the rotating direction, the amount of the air flow passing through the upper surface of the wafer is larger than the lower surface. As a result, a pressure on the upper surface of the wafer is higher than that on the lower surface. Therefore, a pressing force acts to the wafer downward. The behavior of the wafer is stabilized at a position a small distance apart from the inner diameter blade.

Description

Detailed Description of the Invention

[0001]

The present invention relates to GaAs, GaP, I
The present invention relates to a method for manufacturing a III-V group compound semiconductor single crystal substrate such as nP, and particularly to a method for slicing a wafer from a single crystal ingot.

[0002]

2. Description of the Related Art III-V such as GaAs, GaP, InP
Group compound semiconductors have a wide range of applications in fields such as optical devices and electronic devices. The substrates used to make these devices are the liquid-encapsulated Czochralski method (LEC
Method), a horizontal Bridgman method (HB method), a vertical Bridgman method (VB method), etc., and a single crystal ingot is sliced into a wafer shape, and etching, lapping,
It is manufactured to have desired flatness and smoothness by a processing step such as polishing. The orientation of the surface of the wafer to be created is generally the (100) plane. As a method for slicing a wafer from a single crystal ingot, the method shown in FIG.
It is common to use a vertical type inner peripheral blade cutting machine as shown in FIG. As shown in FIG. 1, as a method of collecting sliced wafers, a beam 2 made of carbon, ceramic or the like is attached to the side surface of the ingot 1 so that the wafers do not scatter during slicing, and a plurality of wafers are sliced together with the beams. There are a batch recovery method of cutting off and a single-wafer recovery method of recovering every time one wafer is sliced, and the batch recovery method is advantageous in terms of the cost of the apparatus.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In the slice of the batch recovery system which is generally adopted, the ingot is newly cut out after the slit is made in the beam and the opening of the inner peripheral blade is cut. evacuate. At this time, the sliced wafer sticks to the blade, and when the ingot is moved in that state, it is scraped off by the diamond blade, and so-called saw marks are generated on the wafer. This saw mark is caused by the difference between the base metal plate thickness of the inner peripheral blade and the blade thickness of the blade portion as the maximum step,
There may be irregularities of about m. In order to create an optical device or an electronic device, an active layer is formed by either growing a epitaxial layer in a liquid phase or a vapor phase on a single crystal substrate, implanting ions in the single crystal substrate, or a combination thereof. It is formed. Since these active layers are greatly affected by the irregularities on the surface of the single crystal substrate and the damaged layer,
As the quality required for the single crystal substrate, it is important that the flatness and smoothness are good and there is no damaged layer.

In the slicing process which is the object of the present invention, when the saw mark as described above occurs on the wafer,
It is necessary to increase the grinding amount in the lapping process for removing the irregularities and reducing the damage layer, and it becomes very difficult to correct the flatness. As a means for solving such a problem, it is an object of the present invention to suppress the occurrence of saw marks in a slicing step by a very simple method and to produce a single crystal substrate of a compound semiconductor with good productivity and good quality. .

[0005]

Means for Solving the Problems The present inventors have found out that the cause of the saw mark generated in the slicing process is the warp of the sliced wafer caused by the crystal structure, and the saw mark is generated by an extremely simple method. I found that I can suppress. GaAs, Ga
III-V group compound semiconductors such as P and InP have a zinc blende type crystal structure as shown in FIG. 2, and when the plane orientation of the surface of the single crystal substrate is (100), as shown in FIG. Has twofold symmetry. When a wafer having a (100) plane is sliced from a single crystal ingot by using an inner peripheral cutting machine or the like, a so-called saddle-shaped warp as shown in FIG. 4 is obtained corresponding to the crystal structure. This phenomenon is similarly and universally observed even when the slice direction is changed.

FIG. 4 is a diagram showing a warped state of a wafer having a (100) plane, which is cut out from a single crystal ingot in the positional relationship shown in FIG. In FIG. 4, the A surface is the main flat surface and corresponds to A in FIG. 3, and the B surface is a sub flat surface and corresponds to B in FIG. As for the warp, the central portion is convex in the direction perpendicular to the A surface (<0 bar 1 bar 1>), and the central portion is concave in the direction perpendicular to the B surface (<01 bar 1>). The present inventor, due to the relationship between the warp of the sliced wafer and the slice direction that are universally observed, the sliced wafer adheres to the inner peripheral blade, and when the wafer is retreated to the inner peripheral blade opening, a saw mark is generated. In some cases, I found that the saw mark does not occur. That is, when slicing a wafer having a (100) plane, in the state shown in FIG. 1, when the ingot is moved in a direction perpendicular to the rotation direction of the inner peripheral blade, and this direction is defined as the slice direction, the slice <0 bar 11 of the crystal whose direction is shown in FIG.
It has been found that slices can be made without generating saw marks by setting the direction> or the direction <01 bar 1>. When the slice direction is the <0 bar 11> or <01 bar 1> direction, the generation of saw marks is negligible.
Saw marks will be generated as the slice direction shifts. To prevent the saw mark from being generated, the slice direction is ± 1 from the <0 bar 11> or <01 bar 1> direction.
Within 0 ° is acceptable. More preferably within ± 5 °,
Most preferably, it can be controlled within ± 1 °. This phenomenon can be explained by the air flow generated by the rotation of the inner peripheral blade.

[0007]

It is generally known that even a free-flowing fluid such as air having a low viscosity does not adhere to the surface of a moving object and its flow velocity does not become zero. An air flow having a velocity proportional to the peripheral speed of the inner peripheral blade is also generated on the surface of the inner peripheral blade. When the ingot feeding direction is perpendicular to the rotation direction of the inner peripheral blade, and when the wafer having a (100) plane is sliced from the ingot, the slicing direction is <0 bar 11> direction or <01 bar. By setting the 1> direction, the wafer sliced at that time is convex upward in the inner peripheral blade rotation direction and convex downward in the slicing direction. When slicing is completed and the ingot retracts from the inner peripheral blade to the inner peripheral blade opening, the airflow generated by the rotation of the inner peripheral blade passes more on the upper surface of the wafer because the wafer is convex upward in the rotation direction. . As a result, the pressure is higher on the upper surface than on the lower surface of the wafer. Therefore, a force that pushes the wafer downward is exerted, which balances the elastic force of the wafer and the beam made of carbon, and the behavior of the wafer stabilizes at a position slightly away from the inner peripheral blade. The wafer is separated from the inner peripheral blade and sliced extremely flat without being cut by the diamond grindstone portion of the inner peripheral blade.

[0008]

EXAMPLE Using a single crystal ingot having a growth axis in the <100> direction and having a diameter of about 110 mm prepared by the LEC method, the upper and lower ends of the ingot were cut off at (100) ± 0.5 °, and the outer circumference was 101 mm. After grinding the part into a cylindrical shape, the wafer was sliced by an inner peripheral blade cutting machine rotating in a horizontal plane.

Example 1 (see FIG. 5) The ingot is a (100) plane on the side farther from the inner peripheral blade and a bar (10) on the side closer thereto.
If the carbon beam is adhered to the (0 bar 11) surface and sliced in the <0 bar 11> direction,
Saw mark was not observed at all, and TTV (Total Th
ickness Variation) was about 2 μm.

(Example 2) Referring to FIG. 6, when the side farther from the inner peripheral blade is the (bar 100) plane and the near side is the (100) plane, a carbon beam is bonded to the (011) plane, <01
When sliced in the 1> direction, no saw mark was observed and the TTV was about 2 μm.

Comparative Example 1 (see FIG. 7) On the other hand, an ingot prepared under the same conditions was used (10
When the carbon beam is bonded to the (011) plane when the (0) plane and the near side are the (bar 100) planes and sliced in the <011> direction, a clear saw mark is observed and TT
V became about 50 μm. This means that it is necessary to grind more than 50 μm on a wafer without saw marks in a lapping process which is a post process.

(Comparative Example 2) Referring to FIG. 8, when the ingot made under the same conditions as in Example 1 is set so that the side farther from the inner peripheral blade is the (bar 100) surface and the near side is (100), the carbon is Adhesive beam to the (0 bar 11) surface, <0 bar 11>
When sliced in the direction, a clear saw mark was observed, and TTV was about 50 μm. This means that a wafer without saw marks needs to be ground by about 50 μm more in a lapping process which is a post process. That is, according to the slicing method in which saw marks are not generated, the amount of grinding in the lapping process can be reduced.

[0013]

When slicing a wafer having a (100) plane from a III-V compound semiconductor single crystal ingot having a zinc blende type crystal structure, the wafer always warps in a saddle shape. When the wafer surface is (100) plane,
It is convex downward in the <0 bar 11> direction and upward in the <011> direction. By slicing the wafer by the method of the present invention, a wafer without saw marks, that is, a wafer with good flatness can be produced, and the amount of grinding in the lapping step can be reduced. Further, by reducing the thickness of the sliced wafer, there is an advantage that the number of wafers cut out from the ingot can be increased.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state of slicing by a vertical type inner peripheral blade cutting machine.

FIG. 2 is a perspective view showing a zinc blende type crystal structure.

FIG. 3 is a diagram showing a 2-fold symmetry of a zinc blende type crystal structure.

FIG. 4 is a perspective view showing the warp of the wafer.

FIG. 5 is a diagram showing a slice direction according to the first embodiment.

FIG. 6 is a diagram showing a slice direction according to the second embodiment.

7 is a diagram showing a slice direction of Comparative Example 1. FIG.

8 is a diagram showing a slice direction of Comparative Example 2. FIG.

[Explanation of symbols]

 1 Single crystal ingot 2 Beam 3 Inner peripheral blade

Claims (1)

[Claims] 1. A III-V group compound semiconductor single crystal ingot in a <01 bar 1> ± 10 ° direction or <0 bar 11>.
A method of slicing a compound semiconductor single crystal wafer, which comprises slicing in a direction of ± 10 °.