JP2000068171A - Semiconductor wafer and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make easy and accurate the angularly aligning optical work of a device creating process, by applying no chamfering to the orientation-flat portion of a wafer to machine only its side surface, and by making its side surface orthogonal to the top and rear surfaces of the wafer. SOLUTION: In the chamfering process of a semiconductor-wafer manufacturing process, machining only the side surface of the orientation-flat portion of a wafer, no chamfering is applied to the orientation-flat portion to make its side surface orthogonal to the top and rear surfaces of the wafer. Also, applying chamferings to the outer peripheral side surface of the wafer wherefrom the one of the orientation-flat portion is excluded, its side surface and its top and rear surfaces are connected continuously by curves. In this case, the machining means such one as a grinding other than a cleavage. Also, in the machining, a regrinding, chemical etching, or the like after performing the machining is included too. As result, facilitating the focussing of a microscopy on the ridge formed out of the side and top surfaces of the orientation-flat portion, its angularly aligning accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a circular semiconductor wafer, and more particularly, to a circular semiconductor wafer having an orientation flat portion and a method of manufacturing the same.

[0002]

2. Description of the Related Art A circular semiconductor wafer is usually manufactured by a process as shown in FIG.

[0003] A linear portion called an orientation flat is provided on the outer peripheral portion of the wafer to indicate its crystal orientation. This orientation flat is formed in the cylindrical grinding (2) and chamfering (4) steps of FIG. Alternatively, as another method, there is a method of forming by cleavage. Since the orientation flat is used as a reference for angle adjustment with respect to a specific crystal orientation when a device is formed on a wafer, it is desirable that the orientation flat be as accurate as possible with respect to a specified crystal orientation.
There are two methods for adjusting the angle during device fabrication: mechanical abutment and optical methods.The latter method involves observing the orientation flat from the wafer surface with a microscope and focusing on the orientation flat. This is a method of adjusting the angle based on the reference.
In addition, there is a method of detecting the position of the orientation flat with an optical sensor and adjusting the angle.
Generally, in such a circular wafer, in order to prevent chipping and cracking of the outer peripheral portion during handling, the outer peripheral side surface portion including the orientation flat is uniformly chamfered and connected to the front and back surfaces with a smooth curve. It has become.

[0004]

In the prior art,
In particular, when the angle is adjusted by an optical method, for example, in a method using a microscope, since the cross-sectional shape of the orientation flat portion is curved as shown in FIG. 2, the orientation flat portion is viewed from the surface as shown in FIG. However, it was difficult to focus the microscope observation image, and the accuracy of the angle adjustment was deteriorated.

[0005] In addition, when an angle is adjusted using an optical sensor, light is reflected or wrapped around a curved portion formed by the side surface of the orientation flat and the wafer surface, which adversely affects the accuracy of the angle adjustment. There was something. On the other hand, for example, in a III-V group compound semiconductor having a surface of the (100) plane, if an orientation flat indicating the [011] direction is formed by cleavage, the side surface and the surface of the orientation flat portion are perpendicular to each other,
A wafer whose optical angle can be easily adjusted can be manufactured. However, in this cleavage method, it is necessary to manually process each wafer one by one, which is very troublesome. In addition, it is difficult to accurately control the length of the orientation flat, and further, there is a problem that a flaw at one end of the orientation flat remains for cleavage.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a wafer capable of accurately adjusting an optical angle and a method of easily manufacturing the wafer.

[0007]

As a result of intensive studies, the present inventor has found that the above-mentioned problems can be solved by not chamfering the orientation flat portion.

The present invention has been made based on this finding. For circular wafers with flat front and back surfaces, chamfering is applied to the outer peripheral side surface except for the orientation flat portion to make it smooth with the front and back surfaces, and only the side surface is machined without chamfering the orientation flat portion. Semiconductor wafer having an orientation flat portion side surface orthogonal to the front and back surfaces by means of

[0009] 2. For circular wafers with flat front and back surfaces, chamfering is applied to the outer peripheral side surface except for the orientation flat portion to make it smooth with the front and back surfaces, and only the side surface is machined without chamfering the orientation flat portion. And a method for manufacturing a semiconductor wafer characterized by being perpendicular to the front and back surfaces.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in the chamfering step (4) of the manufacturing process of the semiconductor wafer shown in FIG.
As shown in (2), the orientation flat portion is machined only on the side surface, and is not chamfered so that the side surface and the surface are orthogonal.

In addition, the outer peripheral side surface excluding the orientation flat is chamfered so that the side surface and the surface are continuously curved. For the purpose of preventing chipping, the size of the chamfered portion is preferably 75 μm or more when viewed from above or below the wafer.

Here, the mechanical processing means mechanical processing such as grinding other than cleavage.
Further, it does not prevent further polishing or chemical etching after the mechanical processing.

As a result, since the side surface of the orientation flat portion and the front and back surfaces are perpendicular to each other, when the angle of the orientation flat is adjusted with a microscope during device fabrication,
The ridge formed by the orientation flat side surface and the surface is easily focused, and the accuracy of the angle adjustment can be improved. Also, with the method using an optical sensor,
Unnecessary light reflection and wraparound are eliminated, and the accuracy of angle adjustment is improved. Further, compared to the cleavage method, the method is less troublesome, the accuracy of the orientation flat length is improved, and, of course, no scratch due to cleavage is left.

[0014]

EXAMPLES AND COMPARATIVE EXAMPLES The following describes examples in which the semiconductor wafer of the present invention and its manufacturing method are applied to a 2 "InP wafer. First, the LEC (Liquid Encapsulated Czoc) is used.
An n-type InP single crystal was grown in the (100) direction by the (hralski) method. This single crystal was formed into a cylindrical shape having a diameter slightly larger than 2 ", and a flat surface corresponding to an orientation flat was formed in the [011] direction.
Slicing was performed so as to form a surface, and a wafer was cut out. Next, in the chamfering process, first, the diameter is exactly 50.
After grinding the outer peripheral side surface to 8 mm, the portion excluding the orientation flat was ground so that the corner portion where the side surface and the surface contact was curved. FIG. 4 shows the shape of a wafer obtained by such chamfering. FIG. 5 shows the shape of the wafer before it is put into the chamfering step.

Since such a processing cannot be performed by a copying-type chamfering machine, a chamfering machine having a numerical control mechanism is used. At this time, the crystal orientation of the orientation flat before the chamfering, that is, in the cylindrical grinding process, is measured by an X-ray diffraction method or the like, and the side of the orientation flat is machined by a chamfering machine so as to correct the error. Is performed, an orientation flat having more accurate crystal orientation can be formed. In this embodiment, a lapping, etching, and polishing are performed to obtain a mirror-finished wafer. When the orientation flat portion of the completed wafer was observed from the surface with an optical microscope, the ridge formed by the side surface of the orientation flat portion and the surface was clearly recognized, and the focus could be easily focused. Further, using this orientation flat, the angle of the mask was adjusted with a microscope, and a stripe-shaped pattern was formed on the wafer surface in a direction orthogonal to the orientation flat. Thereafter, the wafer was cleaved in a direction orthogonal to the orientation flat, and the angle θ between the cleavage plane and the stripe pattern shown in FIG. 6 was measured.

For comparison, the orientation flat portion is also chamfered in the chamfering step of the flow shown in FIG. 1, that is, processing is performed so that the side surface of the orientation portion and the front and back surfaces of the wafer are continuous with a smooth curve as described in the prior art. A wafer processed by the same method as that of the above-described embodiment was prepared for the steps other than the chamfering step. As a result of measuring the angle θ between the cleavage plane of these wafers and the angle of the stripe pattern, in the comparative example, θ> 0.05 °
Was 5%. On the other hand, in Examples of the present invention, the ratio of wafers satisfying θ> 0.05 ° was 1% or less.

[0017]

As described above, according to the present invention, the orientation flat portion is not chamfered, but only the side surface is machined, and the orientation flat portion side surface and the wafer surface are orthogonalized, thereby achieving an optical process in the device manufacturing process. Angle adjustment work can be performed easily and accurately. Further, as compared with a conventional manufacturing method for obtaining such a shape, for example, by cleaving, it takes less time and effort to manufacture, and the orientation flat length can be accurately controlled.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a semiconductor wafer manufacturing process.

FIG. 2 is a cross-sectional view of an orientation flat portion of a semiconductor wafer according to the related art.

FIG. 3 is a diagram showing that a focus is not obtained when observed by an optical microscope from the surface of an orientation flat portion of a semiconductor wafer according to a conventional technique.

FIG. 4 is a view showing a shape of a wafer after a chamfering step according to the present invention;

FIG. 5 is a view showing the shape of a wafer before it is put into a chamfering process.

FIG. 6 is a diagram showing a deviation angle θ between a stripe pattern formed based on an orientation flat and a cleavage plane orthogonal to the orientation flat.

Claims (2)

[Claims] 1. A circular wafer having flat front and back surfaces, chamfering is applied to an outer peripheral side surface excluding an orientation flat portion so as to be continuous with the front and back surfaces with a smooth curve, and the orientation flat portion is not chamfered and only a side surface is not provided. A semiconductor wafer having an orientation flat portion side surface orthogonal to the front and back surfaces by machining. 2. In a circular wafer having flat front and rear surfaces, the outer peripheral side surface except for the orientation flat portion is chamfered to be continuous with the front and rear surfaces with a smooth curve, and the orientation flat portion is not chamfered and only the side surfaces are not chamfered. A semiconductor wafer is machined so as to be orthogonal to the front and back surfaces.