JP2004281951A - Semiconductor wafer - Google Patents

Abstract

An object of the present invention is to provide a structure of a semiconductor wafer that can more easily identify the front and back of a notched wafer.
A chamfered portion of a wafer outer peripheral portion has a concave surface formed on one of a front surface tapered portion and a back surface tapered portion, or a wafer notch has a chamfered portion formed on a chamfered portion of a wafer notch. One of them is a concave surface 24.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a compound semiconductor wafer having a notch.
[0002]
[Prior art]
GaAs wafers are widely used as substrates for light receiving, light emitting devices, high frequency devices and the like. In order to manufacture semiconductor devices by implanting ions or forming epitaxial layers on these GaAs wafers, considering the manufacturing cost, it is better to use a larger-diameter wafer like a Si wafer. Can be suppressed. For this reason, a 6-inch (about 150 mm) diameter wafer is often used as a GaAs wafer.
[0003]
With Si wafers, as the diameter increases, instead of attaching an orientation flat and an index flat for specifying the direction of the wafer to the wafer, a notch called a V-shaped notch is formed on the outer periphery of the wafer as shown in FIG. Notched wafers marked with have been used by device manufacturers. With the advent of φ6 ″ (6 inch diameter) wafers, notched wafers have been used by device manufacturers as well as Si wafers. As the diameter of the wafer increases, the size of the wafer increases. In addition, the length of the orientation flat and the index flat becomes longer, which reduces the usable area of the wafer.In addition, when the wafer is rotated in the device manufacturing process, if the wafer diameter is increased, the inertia during rotation is increased. This is because the position is shifted due to the increase in the moment.
[0004]
The processing of such a notched wafer is performed in the following order.
[0005]
(1) The surface of the grown crystal is ground and processed into a cylindrical ingot.
[0006]
(2) A V-shaped groove is formed in a specific direction on the side surface of the ingot (this groove becomes a temporary notch when the wafer is sliced).
[0007]
(3) Slice the ingot into wafers of a predetermined thickness using a slicer, wire saw, or the like.
[0008]
(4) The wafer with the temporary notch is chamfered at the notch portion and other end surfaces by a wafer end surface grinding machine (chamfering machine).
[0009]
(5) The chamfered wafer is polished and the ground surface is mirror-finished.
[0010]
Here, in a general wafer end surface grinding machine (chamfering machine), the wafer 10 having the notch portion 30 (see FIG. 2) is vacuum-sucked to a processing table, and at a high speed as shown in FIG. The wafer outer periphery 20 is chamfered by rotating the wafer 10 against the rotating grindstone 50. When processing the notched wafer 10, the chamfering machine has two grinding wheels. One of the grinding wheels is used for chamfering the entire end surface of the wafer outer peripheral portion 20, and then the notching portion is used for grinding. The notch 30 is chamfered. The surface width and chamfer shape (taper angle, R (R) shape) of each part can be adjusted by inputting numerical data because the end face grinding machine is an NC machine.
[0011]
A grindstone (a grindstone for chamfering a wafer outer peripheral portion or a grindstone for a notch portion) 50 for grinding an end face has a shape with a grinding groove 51 as shown in FIG. Is composed of a tapered portion 52 and an R (R) portion 55. These parts are provided with diamond abrasive grains of a specific particle size.
[0012]
The wafer is chamfered by applying the wafer outer peripheral portion 20 to the grinding groove 51. The upper surface of the wafer outer peripheral portion 20 is brought into contact with the upper tapered portion (upper ground surface 53) of the groove, and the lower surface is brought into contact with the lower tapered portion (lower ground surface 54) of the groove, as shown in FIG. As shown in FIG. 2B, the tapered portion 22 is chamfered to follow the ground surface.
[0013]
The notch portion 30 is different only in that the diameter of the grinding wheel for grinding is considerably smaller than that of the chamfering grindstone for the outer periphery of the wafer. It is the same as the case of processing.
[0014]
When processing a notched wafer, the processing is performed in the order described above, starting with the Si wafer. Here, the notched wafer has exactly the same shape of the front (front) surface and the back (back) surface, so for a wafer that needs to be distinguished between the front and back, be careful not to mistake the front and back in each process. You need to be careful.
[0015]
In the process up to chamfering, there is a method that enables identification of the front and back, such as marking one side of the wafer with a chemical, but if polishing is done after chamfering, there is no such method, and the front and back can be distinguished. It is very likely that the front and back of the wafer will be mistaken in the post-polishing process.
[0016]
Conventionally, as a method for preventing the mixing of the front and back of a wafer, wafers having different shapes of chamfered portions on the front and back have been proposed (for example, see Patent Documents 1 and 2).
[0017]
[Patent Document 1]
JP 2001-53084 A
[Patent Document 2]
JP-A-2002-15966
[Problems to be solved by the invention]
In the above Patent Document 1, in the cross section in the thickness direction of the edge of the wafer, a tapered portion with an angle of 22.5 ° and a round chamfered portion of R300 μm are formed on the front side of the end face processed portion, and on the other hand, It is provided with a taper portion at an angle of 30 ° and a round chamfered portion of 150 μm, and it is possible to distinguish front and back from the difference between the angle and R. Patent Literature 2 discloses that a wafer having a notch is formed at a different angle by setting the inclination angle of the notch with respect to the chamfered portion on one surface side to 22.5 ° and the inclination angle of the notch on the other surface side to 54 °. The front and back sides of the wafer can be distinguished from the appearance of the front and back sides and the difference in gloss when light is applied.
[0020]
However, since the chamfered portion of the wafer in these conventional techniques is several hundred μm long, it is relatively difficult to distinguish between the front and back of the wafer at a glance.
[0021]
SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor wafer structure capable of easily recognizing the front and back of a notched wafer by overcoming the above-mentioned disadvantages of the prior art.
[0022]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0023]
The semiconductor wafer according to the first aspect of the present invention is a semiconductor wafer obtained by cutting a semiconductor crystal, in which a notch for identifying the orientation of the wafer is provided. The tapered portion of any one of the chamfered portions on the outer peripheral portion of the wafer (the back surface) is concave.
[0024]
A semiconductor wafer according to the second aspect of the present invention is a semiconductor wafer obtained by cutting a semiconductor crystal, in which a notch for identifying the orientation of the wafer is provided, wherein a chamfered portion of a notch portion on the wafer surface or a back surface of the wafer is provided. One of the tapered portions of the chamfered portion of the notch portion has a concave surface.
[0025]
According to a third aspect of the present invention, in the semiconductor wafer according to the first or second aspect, the wafer is made of a compound semiconductor wafer, and the material is any one of GaAs, InP, InSb, InAs, and GaP. .
[0026]
<The gist of the invention>
The gist of the present invention is to form one of the surface taper portion or the rear surface taper portion of the chamfered portion of the wafer outer peripheral portion into a concave shape in order to enable identification of the front and back of the notched wafer, Alternatively, one of the chamfered portions of the wafer notch portion is formed into a concave shape on either the front surface tapered portion or the rear surface tapered portion. As shown in FIG. 3, an upper grinding surface or a lower grinding surface for grinding and shaping a tapered portion of a chamfered portion, as either a grinding wheel for grinding a wafer outer peripheral portion or a grinding stone for grinding a notch portion, as shown in FIG. This is achieved by using one having one of the ground surfaces having a convex shape. When the chamfered portion of the outer peripheral portion of the wafer is formed in a concave shape in this way, the light reflection of the chamfered portion differs in a relatively large surface area, so that the front and back surfaces of the wafer can be more easily formed than in the related art. Can be identified.
[0027]
When the tapered portion is referred to as a concave surface, it means that the tapered portion contour is depressed when viewed in the cross section of the wafer outer peripheral portion or the notch portion, and does not necessarily mean that the tapered portion has a constant curvature.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiments.
[0029]
FIG. 2 shows a compound semiconductor wafer 10 obtained by cutting a compound semiconductor crystal such as GaAs, InP, InSb, InAs, or GaP, and a semiconductor wafer provided with a notch portion 30 for identifying the orientation of the wafer.
[0030]
In the first embodiment of the present invention, as shown in FIG. 1, in this compound semiconductor wafer, a chamfered portion 21 of the wafer outer peripheral portion 20 on the wafer front surface (front surface) or the wafer outer peripheral portion 20 on the wafer back surface (back surface). One of the tapered portions 22 (the lower tapered portion in FIG. 1) is formed on the concave surface 24 and the other is formed on the flat surface (straight surface) 23 so that the front and back of the notched wafer can be identified. enable.
[0031]
In the second embodiment of the present invention, in the compound semiconductor wafer 10 provided with the notch portion 30 in FIG. 2, the chamfered portion 31 of the notch portion 30 on the wafer surface (front surface) or the back surface (back surface) of the wafer One of the chamfered portions 31 of the notch portion 30 is formed with one of the tapered portions 22 on the concave surface 24 and the other is formed on the flat surface 23 so that the front and back of the notched wafer can be distinguished.
[0032]
An example of the first embodiment will be described. FIG. 3 shows a grindstone 40 provided in an end grinding machine (chamfering machine) for grinding the outer peripheral portion of a wafer. As shown in FIG. 3, a grinding groove 41 is formed on the side surface of the grinding wheel main body 40a in the grinding wheel 40 for chamfering the wafer outer peripheral portion. The grinding groove 41 has an upper grinding surface 43 and a lower grinding surface 44 for grinding the outer peripheral portion 20 (FIG. 2) of the wafer 10 into a tapered cross section, and R (R) for grinding the outer peripheral edge of the wafer with a predetermined curvature. And a unit 45. Then, either one of the upper grinding surface 43 and the lower grinding surface 44 for grinding and shaping the tapered portion 22 of the chamfered portion 21 of the wafer (the lower grinding surface 44 in this example) is It is formed on a convex curved surface 46.
[0033]
By grinding the outer peripheral portion 20 of the wafer using the grindstone 40 having the lower grinding surface 44 having a convex shape, the chamfered portion 21 of the outer peripheral portion of the wafer 10 has a front side tapered portion as shown in FIG. 22 is formed on a linear inclined surface (flat surface 23), and the back side tapered portion 22 is formed and processed into a concave surface 24. In the case of this embodiment, the concave surface 24 is formed as a curved surface having a constant curvature such that the tapered portion contour is depressed when viewed in a cross section of the outer peripheral portion of the wafer.
[0034]
When the chamfered portion 21 of the wafer 10 is formed in a concave shape in this manner, the light reflection of the chamfered portion differs in a relatively large surface area compared with the conventional case, so that the front surface and the back surface can be distinguished more easily than before. can do.
[0035]
Also in the case of the second embodiment, the same as in the first embodiment described above, in order to make it possible to identify the front and back of the notched wafer, as a grindstone for grinding the notch portion 30 of the wafer 10, As described in 3, regarding the grinding groove 41 provided on the side surface of the grindstone main body 40a, one of the upper grinding surface 43 and the lower grinding surface 44 (the lower grinding surface 44 in this example) is replaced by And those having a convex shape (convex curved surface). As a result, one of the front side taper portion 22 and the rear side taper portion 22 of the chamfered portion of the wafer notch portion 30 is shaped into a concave surface 24.
[0036]
If either the front side tapered portion or the back side tapered portion of the chamfered portion 21 of the wafer notch portion 30 is formed in a concave shape, the light reflection of the chamfered portion 21 differs in a relatively large surface area as compared with the related art. Therefore, the front and back surfaces of the wafer can be identified more easily than before.
[0037]
Hereinafter, examples of the present invention will be described.
[0038]
(Example)
1000 (100) GaAs wafers with a temporary notch in the (100) direction and a thickness of 750 μm and a diameter of 152 mm were prepared, and these wafers were used as a grindstone of an end face shape grinder (chamfering machine) as shown in FIG. As shown in the figure, the wafer has an upper grinding surface 43 and a lower grinding surface 44 for chamfering the end surface of the outer peripheral portion of the back surface of the wafer into the tapered portion 22, of which the lower grinding surface (lower tapered portion) 44 has a convex cross-sectional shape. Using the outer peripheral grinding wheel 40 formed as 46, a notched (100) wafer 10 having a diameter of 150 mm was shaped. FIG. 4 shows an enlarged cross section of the outer peripheral portion 20 of the wafer 10 at this time.
[0039]
After chamfering these 1000 wafers, the wafers were sent to a polishing process, but there was no misunderstanding of the front and back of the wafers in the subsequent processes.
[0040]
This is because, as shown in FIG. 4, the tapered portion 22 of the outer peripheral portion 20 on the front surface side is a flat surface 23, whereas the tapered portion 22 of the outer peripheral portion 20 on the rear surface side of the wafer is a concave surface 24. This is considered to be because the way of reflection when light hits is different between the two. The processing of the outer peripheral portion did not damage the wafer.
[0041]
(Comparative example)
As a comparative example, 1,000 (100) GaAs wafers each having a thickness of 750 μm and a diameter of 152 mm with provisional notches in the (100) direction were prepared, and these wafers were cross-sectionally shaped as shown in FIG. Was shaped into a (100) wafer having a diameter of 150 mm with a notch by using the grinding wheel for outer circumference grinding. FIG. 5 shows an enlarged cross section of the outer peripheral portion of the wafer at this time. In the wafer 10 of this comparative example, both the front and rear tapered portions 22 are flat surfaces 23, and the concave surface 24 is not formed as in the above-described embodiment (FIG. 4).
[0042]
When 1000 wafers of these comparative examples were polished after chamfering, in the subsequent steps, 10 front and back wafers were misplaced.
[0043]
From the results of the present embodiment and the comparative example described above, in the notched wafer, setting any one of the shapes of the tapered portion 22 of the chamfered portion 21 of the wafer outer peripheral portion 20 to the concave surface 24 means that the front surface and the back surface of the wafer It is very effective as a method of identification, and it can be seen that the management of the front and back of the wafer can be surely performed in wafer manufacturing.
[0044]
In the above embodiment, the tapered portion of the chamfered portion of the wafer outer peripheral portion on the back surface of the wafer is described as a concave surface. (1) The tapered portion of the chamfered portion of the wafer outer peripheral portion of the wafer surface is formed as a concave surface Also, (2) a configuration in which the tapered portion of the chamfered portion of the notch portion on the wafer surface is concave, and (3) a configuration in which the tapered portion of the chamfered portion of the notch portion on the back surface of the wafer is concave. Also in these embodiments, the effect of preventing the wafer from being interchanged between the front and back sides can be obtained as described in the above embodiment and comparative example.
[0045]
【The invention's effect】
As described above, the semiconductor wafer of the present invention may be configured such that one of the surface taper portion and the back surface taper portion of the chamfered portion of the wafer outer peripheral portion is concave, or the surface taper portion of the chamfered portion of the wafer notch or The present invention has a configuration in which one of the back side tapered portions is formed in a concave shape, and light reflection is different at a chamfered portion of a wafer outer peripheral portion in a relatively large surface area formed in the concave shape. According to the semiconductor wafer described above, the front surface and the back surface can be distinguished more easily than the semiconductor wafer of the related art.
[0046]
Further, according to the semiconductor wafer of the present invention, since the front surface and the back surface of the notched wafer can be easily distinguished in the wafer manufacturing process, the reduction of the yield due to the mistake of the front surface and the back surface of the wafer is prevented. can do.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view showing a shape of a chamfered portion on an outer peripheral portion of a semiconductor wafer of the present invention.
2A and 2B show the appearance of a notched wafer to which the present invention is applied, wherein FIG. 2A is a plan view and FIG. 2B is a cross-sectional view.
FIG. 3 is a partially enlarged sectional view of a grindstone used for chamfering an outer peripheral portion of a wafer in an embodiment of the present invention.
FIG. 4 is an enlarged cross-sectional view of an outer peripheral portion of a wafer chamfered with the grindstone of FIG. 3 according to the embodiment of the present invention.
FIG. 5 is a diagram showing a cross section of an outer peripheral portion of a wafer according to a comparative example.
6A and 6B are cross-sectional views of a conventional grindstone and a state of chamfering an outer peripheral portion of a wafer, wherein FIG. 6A is a diagram before chamfering and FIG. 6B is a diagram after chamfering.
[Explanation of symbols]
Reference Signs List 10 Wafer 20 Wafer outer peripheral portion 21 Chamfered portion 22 Tapered portion 23 Flat surface 24 Concave surface 30 Notch portion 31 Chamfered portion

Claims (3)

In a notched wafer to identify the orientation of the wafer in the semiconductor wafer obtained by cutting the semiconductor crystal,
A semiconductor wafer characterized in that a tapered portion of a chamfered portion of either a wafer outer peripheral portion on a wafer front surface or a wafer outer peripheral portion on a wafer back surface is concave. In a notched wafer to identify the orientation of the wafer in the semiconductor wafer obtained by cutting the semiconductor crystal,
A semiconductor wafer characterized in that either a chamfered portion of a notch portion on the wafer surface or a chamfered portion of a notch portion on the back surface of the wafer has a concave surface. The semiconductor wafer according to claim 1 or 2,
A semiconductor wafer, wherein the wafer is a compound semiconductor wafer, and the material is any of GaAs, InP, InSb, InAs, or GaP.

Images