JPS59107520A - Semiconductor substrate - Google Patents

Abstract

PURPOSE:To reduce the generation of breaking on the titled semiconductor substrate by a method wherein the side face thereof is formed into mirror face. CONSTITUTION:A surface 1 is finished in mirror face having no distortion and the side face of the semiconductor substrate, having the back side 4 as cut-off face and the side face 2 of 1.5mumRmax of polished finish, is finished in the mirror face of 0.2mumRmax or below in surface roughness by performing chemical polishing. When said side face is finished in mirror face, the side face is formed into the state wherein defects such as notches, an uneven surface, cracks, scratches and the like, where stress concentration is generated and will be the starting point of a cleavage causing breakages, are almost removed. As a result, the generation of a cleavage can be prevented, thereby enabling to increase the breakage strength of the semiconductor substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor substrate used for manufacturing semiconductor devices, and more particularly to a semiconductor substrate designed to prevent damage Jj4 from occurring during a manufacturing process.

Used to manufacture semiconductor devices such as integrated circuits
The semiconductor substrate used is a substantially disk-shaped wafer as shown in FIG. In the figure, / is a main surface polished to a distortion-free mirror surface, which is called a surface or mirror surface. This is a cylindrical surface along the outer periphery of the wafer, which is usually ground with a coarse grindstone before cutting the single crystal bar into rings. 3 is a plane parallel to the [/lo] direction called an orientation flat provided on a part of the outer periphery of the semiconductor substrate, and is usually finished by forming and grinding with a coarse grindstone before slicing the single crystal rod into rounds. The surface opposite to the main surface l is the surface that has been cut by the cutting wheel and is called the back surface. The cylindrical surface 2 and the orientation flat 3h are chamfered surfaces of various shapes, some examples of which are shown in the schematic cross-sectional view of FIG. In addition, the second @ ij: FA /A in the figure
-A cross section taken along the A' plane is shown.

Figure 2 (a) shows upper and lower taper chamfering, (b) shows semicircular chamfering, (c), 2) shows semi-elliptical chamfer11), G]+ shows parabolic chamfering, and (f) shows upper and lower chamfering. It is chamfered.

Conventionally, materials made of 8i-C have been used as materials for semiconductor substrates used to manufacture semiconductor devices such as the above-mentioned integrated circuits, but recently m-V materials such as 0aAs have been used.
Devices made of group semiconductors have also come to be used.

All of these semiconductors have a diamond or zincblende crystal structure and therefore have cleavage planes. A cleavage plane can be used to obtain a flat surface with very good uniformity simply by breaking it, so it has the advantage of being used as a reflection surface for semiconductor lasers. It was also a drawback that caused problems.

In particular, since (A-V group semiconductors such as iaAs have a stronger cleavage property than Si, damage to the semiconductor substrate during the manufacturing process becomes a problem.) The various chamfers shown in the 'πλ diagrams Although this is intended to prevent cracking, etc., damage has naturally occurred to This was a drawback.

In the present invention, the cause of damage to a semiconductor substrate is defects (irregularities, notches, cracks) caused by grinding on the outer periphery.

This is due to the presence of scratches, etc.), and in order to eliminate these defects, we propose a semiconductor substrate with mirror-finished sides so that it is less likely to be damaged.

That is, in the longevity embodiment of the present invention, for example, the cylindrical surface made of various chamfered surfaces shown in FIG. 2 is made into a mirror surface.

Fig. 3 is a schematic cross-sectional view of various samples used to explain the present invention in detail, in which (a) the front surface has a mirror finish with no distortion, the back surface q has a cut surface, and the (fil] surface 2 has a mirror finish without distortion. Approximately/jμm1
″tmax grinding finish a), so (h) figure is (a)
Compared to the one shown in the figure, the only difference is that the back side has a chemically etched finish. The surface roughness was reduced to O1jμmR by chemical etching the side surface of the one shown in
, lax, and (d) is similar to (a).
The side surface of the object shown in the figure is polished to a mirror surface with a surface roughness of 02μm or less by mirror boring, and (c) is the back surface of the object shown in (d).
(f) has an etch finish, and (f) is (
d) The back side of the one shown in the figure is finished to a distortion-free mirror surface (same level as the front side).

Both of these samples have side surfaces parallel to the [//θ] direction and have a width j~! q], length 30~≠0, thickness 30
It consists of a strip of 0 to 1/-00 μm, and the side surface has a semi-elliptical chamfered shape.

Here, the surface finish shown in (a) corresponds to the surface finish currently commonly used in 0aAs sea urchins, and the one shown in (C) corresponds to the surface finish currently commonly used in silicon wafers. The finished state t'14 (i) is made to match.The crystal material used is a 0aAs substrate that is prone to breakage, as shown in Figures 3(a) to (r).lt
For each shape, in order to obtain reference data, a nine-square shape was used on an 8+ board as shown in FIGS. 3(b) and 3(c).

The present inventors conducted a bending fracture experiment using the above sample, with both ends freely supported and a concentrated load applied to the center, and compared the bending fracture stresses of various shapes.

Figure J shows the bending fracture stress values of samples with various surface shapes shown in Figure 3. This indicates whether the surface is under tensile stress. From the figure, we can see that samples with mirror-finished sides, samples with ground-finished sides, and samples with surface roughness of 0.
Compared to a sample with a chemically etched finish of about 3ltmTLmax, the fracture stress is significantly improved. The Cia As substrate of the present invention has approximately three times the strength of the currently used substrates, and is approximately as strong as the currently used substrates81.
The strength of the St substrate of the present invention is about 1 times that of the currently used substrates.

As shown in the figure, the sides are o, 2/im. 28 or less ((It is thought that the reason why the fracture strength of mirror-finished samples is improved is as follows.

When the sides are polished to a mirror finish, most of the defects such as notches, unevenness, cracks, and scratches that cause stress concentration and become starting points for cleavage that cause damage have been removed.
It becomes. The idea is that the fracture strength increases because the coil prevents the occurrence of cleavage. The experimental results shown in Section F contradict this idea.

When a mechanically calculated maximum stress is applied to sample 1d material whose side surfaces are not mirror-finished, cleavage occurs from the cleavage starting point? However, even if the maximum stress of 3'I1 is applied to the sample ifI, whose fl11 surface is mirror-finished, no cleavage cracks occur, and no further stress occurs. When it was destroyed by the addition of water, it often broke into many pieces. The reason why the wafer breaks into multiple pieces is because the stress is stored as elastic energy within the wafer, supporting the above idea.

Furthermore, in Figure ≠, the fracture strength is only slightly improved in the case where unevenness around Q, j /+m exists on the full surface (the sample in Figure 3 (c) finished by chemical etching). From 0. ．． 3-, the irregularities on the surface of the order of am indicate the starting point of cleavage.
i The unevenness of the surface is Q2. It will be necessary to have less than about am.

In the experiment described above, the samples shown in FIG. 3 ((1) to (f) were polished to a mirror finish on the sides, but the semiconductor substrate with high breaking strength, which is the objective of the present invention, Since it can be obtained by removing defects that cause stress concentration on the surface, it is obvious that a mirror finish can be achieved not only by polishing but also by etching or other methods. It is clear that there is no relation to the shape.Furthermore, although the material of the semiconductor substrate is (aAs) and 81 is shown, it is clear that other semiconductor substrates may be used.

From the above explanation, it has become clear that if the side surface of the semiconductor substrate has surface irregularities of approximately 0.2 μm or less, it will not be possible to obtain a product with high fracture strength, that is, a product with a small probability of occurrence of damage. A semiconductor whose unevenness is about 0.2 μm or less has a mirror surface.

From this, it follows that a semiconductor substrate whose outer peripheral side surface of the wafer has a mirror surface is a semiconductor substrate with a low probability of occurrence of damage.

Semiconductor devices are becoming more dense and faster each year, and along with this, the manufacturing process is also becoming more complex.As a result, the processing steps for semiconductor substrates are also becoming more complex. The probability of semiconductor substrate failure is increasing.

Recently, automation of semiconductor device manufacturing has been promoted, but since this automated process involves continuous processing, there is a risk of damage to semiconductor substrates during the process.
d It will also stop the entire process and damage the semiconductor substrate]l
is becoming an increasingly big problem.

Since the present invention solves the above problems, it provides a significant improvement in semiconductor manufacturing.

Also, to prevent damage to semiconductor substrates, the larger the diameter of the semiconductor substrate, the thicker it becomes. However, if the semiconductor substrate of the present invention is used, it becomes possible to make the thickness thinner than that of the conventional one. Reducing the thickness of the semi-conductor substrate has the advantage of making it more economical because more semiconductor substrates can be obtained from the ingot, but the problem is that the weight of the semiconductor substrate becomes a factor in damage. Therefore, from this point of view, it also contributes to the reduction of breakage, and there is also the possibility of improving the relationship between the diameter and thickness of the conventional U-17.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a semiconductor substrate, FIG. 2 is a schematic cross-sectional view showing several examples of chamfered molding surfaces, FIG. 3 is a schematic cross-sectional view of various samples used to demonstrate the effects of the present invention, and FIG. ≠M is a diagram showing fracture stress. l...principal surface, λ...cylindrical surface, 3-orientation/
Flat, <L...Back side. fathom 1 vice

Claims (1)

[Claims] A semiconductor substrate characterized by having a mirror surface on the outer peripheral side of the wafer.