JPH04249114A - Method for cutting single crystal for optics - Google Patents

Abstract

PURPOSE:To cut out an optic not containing a core and having the area larger than those heretofore available by cutting said simple crystal body along the plane in parallel substantially in the pickup direction of the single crystal for optics. CONSTITUTION:A single crystal 1 is cut along the plane 3 in parallel substantially in the pickup direction A to manufacture a number of wafers 4 of almost rectangular shape. At that time, although a number of lattice faces corresponding to the plane 3 are considered, practically a blade is fed into the single crystal 1 along the plane vertically in the direction [100] and cutting is carried out to form the lattice faces of wafers 4 as 100. When the single crystal 1 is cut along the plane vertical in the direction [010], the lattice faces of wafers 4 are formed as [010]. In the cubic system, respective lattice faces of [001], [010] and [100] are equivalent in physical properties each other, and it is not necessary to discriminate them and also said respective lattice faces are rectangular each other. When the single crystal 1 is cut along the plane vertical in the direction [110], the lattice faces of [110] are formed.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to silicon oxide bismuth B
The present invention relates to a method of cutting a cubic single crystal for an optical element such as an i12SiO20 (BS0) single crystal to produce a wafer.

0002

[Prior art] Silicon oxide bismuth Bi12SiO20
(BS0) single crystals have excellent optical properties and are expected to be used as optical functional devices such as magnetic field sensors, image conversion devices, and volume hologram devices. BSO is a body-centered cubic crystal and belongs to the bismuth sirenite family, which belongs to space group 23.

[0003] To produce such a BSO single crystal,
A melt of bismuth oxide and silicon dioxide is collected in a platinum crucible, a seed single crystal is immersed in the melt, and the seed single crystal is pulled up while rotating to form a BSO single crystal in the shape of an approximately round rod (approximately cylindrical). Create. Then, the approximately cylindrical BSO single crystal is sliced to cut out circular wafers 6 as shown in FIG.

0004

[Problem to be solved by the invention] However, the inventor of the present invention
When I tried to cut out a BSO plate from a circular wafer and fabricate a spatial light modulator, I encountered the following problem. That is, a so-called core 2 is generated near the center of the circular wafer 6, and this portion cannot be used as a spatial light modulator or the like because the optical characteristics etc. of this portion are different from those of the surrounding area. Therefore, the circular wafer 6
When further cutting out an optical element from the wafer, it is necessary to cut out, for example, a substantially square optical element 7 while avoiding the core 2. On the other hand, due to the growth conditions of the BSO single crystal, there is a limit to the size of the substantially cylindrical single crystal, and the diameter of the circular wafer 6 is approximately 80 mm at most. As a result, the size of one side of the optical element 7 is only 30 mm or less, making it impossible to increase the size and area of the optical element 7.

On the other hand, the reason why the core 2 is formed is as follows.
There are two possible causes: segregation of impurities and the appearance of so-called "facets." The segregation of impurities is approximately cylindrical B
This occurs because the growth rate in the center of the SO single crystal is greater than that in the surrounding area, and the effective segregation coefficient depends on the crystal growth rate. Facets often appear in single crystals with high symmetry and strong crystal habit. In any case, it is extremely difficult to obtain a single crystal without a core during the growth of a BSO single crystal because many factors interact with each other during crystal growth.

[0006] An object of the present invention is to make it possible to produce a wafer that does not include a core and can cut out optical elements with a larger area than before when cutting a single crystal for optical elements to produce a wafer. An object of the present invention is to provide a method for cutting a single crystal for an optical element.

[0007]

[Means for Solving the Problems] The present invention provides a cutting method for producing wafers by cutting a cubic system single crystal for an optical element produced by a pulling method, in which the pulling direction of the single crystal for an optical element is provided. This invention relates to a method for cutting a single crystal body for an optical element, which cuts the single crystal body for an optical element along a plane substantially parallel to the plane.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic front view for explaining the cutting portion of a substantially cylindrical single crystal body 1 for an optical element, and FIG. 2 is a bottom view thereof.

In the example, first, a cubic system single crystal body 1 for an optical element is produced by a conventional pulling method. This single crystal body 1 has a substantially cylindrical shape with a tapered upper part, and a hanging part 1a is formed at the upper end. BSO single crystal, Bi12
GeO20 single crystal etc. are grown in the [001] direction (ie, pulling direction A). Conventionally, the single crystal body 1 was sliced into rings along a plane perpendicular to the pulling direction A, so that a core remained at the center of the circular wafer. Also, the lattice plane of a circular wafer is necessarily (00
1) It became a face.

In contrast, in this embodiment, the single crystal body 1 is cut along a plane 3 substantially parallel to the pulling direction A to obtain a large number of substantially rectangular wafers 4. On this occasion,
Although there are many possible lattice planes corresponding to plane 3, in reality, as shown in FIG. 2, for example, [100]
Single crystal 1 blade along a plane perpendicular to the direction
When the wafer 4 is fed into the interior and cut, the lattice plane of the wafer 4 becomes (1
00) becomes. Furthermore, when the single crystal 1 is cut along a plane perpendicular to the [010] direction, the lattice plane of the wafer 4 becomes (010). In the cubic system, (001
), (010), and (100) are physically equivalent to each other and need not be distinguished, and these lattice planes are orthogonal to each other. Furthermore, the [110] direction is the direction that makes a 45° angle to both the [100] direction and the [010] direction, and if the single crystal 1 is cut along a plane perpendicular to the [110] direction, , (110)
lattice planes are obtained.

According to this embodiment, the core 2 is not present in the center of each wafer 4, and wafers 4 containing no core can be taken out. Further, unlike conventional circular wafers, there is no need to cut out square, rectangular, etc. optical elements while avoiding the core 2 in the center, so it is possible to increase the area of each optical element. Moreover, since each wafer 4 is approximately rectangular, especially when cutting out square or rectangular optical elements,
Unnecessary parts can be reduced even more than conventional circular wafers.

Moreover, in the past, the lattice plane of a circular wafer was inevitably the single crystal growth plane, that is, the (001) plane in this example. In contrast, in this embodiment, the lattice plane of the wafer 4 can be easily selected between the (100) plane and the (110) plane by simply rotating the substantially cylindrical single crystal body 1 around the core 2. can do.

More specific examples will be described below. Using an internal frequency slicing machine as a cutting machine,
A substantially cylindrical single crystal 1 was cut along the cutting line 5 with a blade having an inner diameter of 184 mm and a thickness of 0.35 mm. The dimensions of the BSO single crystal 1 are 60 mmφ in diameter,
The length of the cylindrical portion was 80 mm. Blade rotation speed is 16
The cutting speed was 50 rpm, the sample feeding speed was 5 mm/min, the thickness of the wafer 4 was 4 mm, and both the (100) lattice plane and the (110) lattice plane were cut. As a result, coreless wafers with a maximum size of 55 mm x 80 mm could be obtained.

[0014]

According to the present invention, since a cubic system single crystal for an optical element is produced by a pulling method, a core is generated that extends in the pulling direction of the single crystal. and,
Since the single crystal for optical elements is cut along a plane substantially parallel to the pulling direction of the single crystal for optical elements,
It is possible to cut out a wafer that does not contain any cores, except for a small portion of the wafer that falls on the area where the cores exist. As a result, unlike conventional circular wafers, there is no need to cut out optical elements while avoiding the core present in the center of the wafer, so it is possible to cut out optical elements with a much larger area than in the past.

Furthermore, the lattice plane of the wafer can be changed and selected simply by rotating the single crystal material for optical elements around the pulling direction of the single crystal material and changing the direction of cutting.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view for explaining a cutting portion of a substantially cylindrical single crystal body 1 for an optical element.

FIG. 2 is a bottom view illustrating a cutting portion of a substantially cylindrical single crystal body 1 for an optical element.

FIG. 3 is a plan view showing a conventional circular wafer.

[Explanation of symbols]

1 substantially cylindrical single crystal for optical element 2 core 3 plane (cut surface) substantially parallel to the pulling direction 4 wafer 5 cutting line 6 circular wafer 7 optical element

Claims (1)

[Claims] 1. A cutting method for producing a wafer by cutting a cubic system single crystal for an optical element produced by a pulling method, wherein the cutting method comprises: A method for cutting a single crystal for optical elements, which cuts the single crystal for optical elements along a plane.