JPH02273923A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To contrive the prevention of the generation of a break, a crack and the like in the outer peripheral part of a wafer by a method wherein the diameter of a first wafer is left without being changed and at the same time, the unbonded outer peripheral part, at which the first wafer and a second wafer oppose to each other pinching a void between them, of the wafer is removed. CONSTITUTION:A bonded semiconductor substrate (a bonded wafer) 14 is formed by a method wherein the fellow mirror-polished main surfaces of first and second semiconductor substrates (first and second wafers) 11 and 12 performed a bevel work 16 on their sidewalls are closely adhered to each other, are heat-treated and are integrally formed, and a joined semiconductor substrate 15 is formed by a method wherein the fellow main surfaces, which are mirror- polished and on the main surface of a first semiconductor substrate 11a on at least one side of which an oxide film 13 is applied, of the first substrate 11a and a second semiconductor substrate 12, which are performed a bevel work 16 on their sidewalls, are closely adhered to each other, are heat-treated and are integrally formed. The diameter of the substrate 11 of the substrate 14 is left without being changed and at the same time, the sidewall of the substrate 14 is ground so that an unbonded outer peripheral part, at which the substrates 11 and 12 oppose to each other pinching a void between them, does not exist. In such a way, the unbonded outer peripheral part, that is, the outer peripheral part, at which the first and second wafers oppose to each other pinching a void between them, is removed. Thereby, a supply of the bonded wafer, in which a break, a crack and the like are not generated in its outer peripheral part, becomes possible.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for manufacturing a semiconductor substrate, and in particular to an adhesive method for closely integrating two semiconductor substrates for a semiconductor device. It is used for manufacturing semiconductor substrates.

(Prior Art) An outline of a conventional manufacturing method of a bonded wafer in which two semiconductor substrates (hereinafter referred to as wafers) for semiconductor devices are brought into close contact and integrated will be explained with reference to the drawings. First, the conventional wafer 11 whose surface to be bonded is mirror-polished is
As shown in Figure (a), the cleaning process is performed regardless of the presence or absence of an oxide film on the surface. As shown in Figure (b), the mirror surfaces are brought into close contact with each other in a clean atmosphere and physically bonded. .

Next, as shown in (c) of the same figure, a void inspection is performed to check the presence or absence of gaps on the bonded surface using an infrared transmission method.Next, as shown in (d) of the same figure, the temperature is 200°C or higher, usually 11
A heat treatment was performed at 00° C. for about 2 hours to form an integrated bonded wafer 1.

However, as shown in FIG. 6(a), the outer peripheral portion of the wafer 11 is beveled (umbrella-shaped) so that the outer peripheral surface is book-shaped. Furthermore, due to surface treatment such as mirror polishing, surface sag (indicated by a broken line) occurs on the outer peripheral surface. When such wafers are bonded, the outer periphery 1 on the bonded wafer
No. 2 is not bonded due to the beveled surface and surface sag. Proceeding to the element manufacturing process in this state not only causes chipping and cracking, but also leads to process contamination. This lick Figure 6 (
As shown in b), the wafer diameter is reduced by adding an outer periphery grinding process to scrape off the unbonded portion.
That is, for example, when wafers with a diameter of 125 nnφ are bonded as shown in FIG.
It was formed on a φ wafer.

When wafers are bonded, the portion that is not bonded due to the bevel surface or surface wobbling is about 2 to 3 Ill from the outer periphery. In order to create a substrate with no unbonded parts on the outer periphery, it would be sufficient to scrape off only that part, but if this is done, the standard wafer diameter size standard, for example 100 nm, would be required.
φ, 125IIIφ, 1501111φ, etc., and therefore lacks versatility, and for example, conventional jigs and instruments for holding or storing wafers cannot be used in common.

Therefore, when reducing the diameter of the wafer in the conventional technology, 150 niφ becomes 125IIIφ, 125 i
lφ is 1001nφ, so that the diameter of one rank is reduced. Therefore, a long outer circumferential grinding process is required, and by reducing the diameter, the chip forming area is reduced, leading to an increase in the cost of the wafer.

(Problems to be Solved by the Invention) As described above, the outer peripheral part of the bonded wafer becomes unbonded due to the beveled surface or surface sagging, and if left as it is,
When proceeding to the element manufacturing process, chips and cracks occur on the outer periphery of the wafer, leading to process contamination.

If only the unbonded portion on the outer periphery is removed in order to prevent this, the diameter of the wafer will deviate from the standard dimensions, resulting in loss of versatility. In order to maintain versatility, it is wasteful in terms of production to further grind the material to a standard size that is one rank smaller in diameter.

An object of the present invention is to solve the problems of the prior art when manufacturing one bonded wafer by closely integrating two semiconductor wafers, and to solve the problems without reducing the diameter of the substrate.
Further, it is an object of the present invention to provide a method of manufacturing a bonded wafer without chipping, cracking, etc. on the outer periphery of the wafer.

[Structure of the Invention] (Means for Solving the Problems) A method for manufacturing a semiconductor substrate (wafer) of the present invention includes a method for manufacturing a semiconductor substrate (wafer) in which mirror-polished main surfaces of first and second semiconductor substrates whose side walls are bevel-processed are connected to each other. or a step of forming a bonded semiconductor substrate in which mirror-polished principal surfaces with an oxide film attached to at least one principal surface of the substrates are brought into close contact with each other and integrated by heat treatment; and a first semiconductor substrate of the bonded semiconductor substrate. a step of grinding a side wall of the bonded semiconductor substrate so that the diameter of the bonded semiconductor substrate remains unchanged and there is no unbonded outer peripheral portion where the first semiconductor substrate and the second semiconductor substrate face each other with a gap in between. It is characterized by:

(Function) In the present invention, in the step of grinding the side wall of the bonded wafer, the diameter of the first wafer is not ground and is left as is, so the diameter of the bonded wafer is equal to that of the conventional wafer, and the diameter of the bonded wafer is the same as that of the conventional wafer. Since the unbonded outer periphery, that is, the outer periphery where the first wafer and the second wafer face each other with a gap in between, is removed without changing the diameter of the wafer, chips and cracks in the outer periphery during the device manufacturing process are eliminated. significantly reduced.

This made it possible to supply wafers with no unbonded parts without reducing the diameter of the bonded wafers, and it was also possible to increase the chip formation area.

The diameter of the wafer is the maximum value of the outer circumferential diameter d1 of the wafer, as shown by the symbol d7 in Figure 1 (a>), and the unbonded outer circumferences are opposite to each other with a gap in between, as shown in the cross-sectional view. This is plane ABC or plane AB'C'.

(Example) Next, an example of the present invention will be described below with reference to the drawings.

A first semiconductor substrate (hereinafter referred to as a first wafer) 1 which has been beveled 16 and has a mirror-polished surface to be bonded as shown in FIG.
Prepare 20 pieces of 1. The specifications of the first wafer are diameter 1
25 lnφ, thickness 625μrg, N type, plane orientation (10
0) and specific resistance ρΣ10Ω·C11.

Ten of these sheets were thermally oxidized to a thickness of 500 mm on the surface to be adhered.
Forms 0 oxidized fyA13. A first wafer with an oxide film attached thereto is denoted by reference numeral 11a.Next, 20 second semiconductor substrates (hereinafter referred to as second wafers) 12 are prepared, which are beveled and have mirror-polished surfaces to be bonded. The specifications of the second wafer are the same as those of the first wafer 11.

Next, as in the prior art, the first wafer and the second wafer are closely attached and heat-treated at 1100° C. for 2 hours to create an integrated bonded semiconductor substrate (hereinafter referred to as bonded wafer).

As shown in FIG. 1(a), there are ten bonded wafers consisting of a first wafer 11 and a second wafer 12, and as shown in FIG. Ten bonded wafers 1 to 1 each consisting of wafer 12 were formed.

Next, 10 each of A and -15 (with oxide film) on the bonded wafer.
Five of the grinding wheels 2 shown in Fig. 2(a) are
1, the outer periphery was ground as shown in FIG. 1(b). Reference numeral 22 is the grinding portion of the grindstone 21, and the roughness is #800. First, the bonded wafer top A or 12 is fixed on the vacuum chuck stand 23. Reference numeral 24 is a vacuum groove that attracts the wafer. Next, the height of the grindstone 21 is adjusted so that the distance Mh from the wafer mounting surface of the chuck table 23 to the lower surface of the grindstone 21 is 600 μm. In this state, the whetstone 21
is rotated and fed in the direction of the arrow, and the chuck table 23 is also rotated until the diameter of the upper second wafer 12 is 117mmφ.
Grind the outer periphery so that

Subsequently, the unbonded orientation flat portion is similarly ground and removed.

In this embodiment, the grindstone is fed in the grinding process so that the grinding allowance becomes 4III1 in the radial direction, and the unbonded portion ABC is removed. Generally, the grinding allowance is determined in advance through trials.

FIG. 2C is a partially omitted cross-sectional view including the outer circumferential portion of the bonded wafer A placed on the chuck stand after the grinding has been performed. FIG. 2D is a partially omitted plan view of the bonded wafer 14. As is clear from Ryogoku, the diameter of the bonded wafer after grinding can maintain the standard size because the diameter of the first wafer remains as it is without being ground. Also, all unbonded outer peripheral parts are removed.

5 each of bonded wafers IA and 15 (10 in total) whose outer periphery was ground as described above, and 5 each (10 in total) of bonded wafers L1 and 15 whose outer periphery was not ground,
A bonded wafer was lapped using a lapping machine until the thickness of the bonded wafer became 725 μm, and a comparative test for chipping, cracking, etc. was conducted. As a result, chipping occurred on all of the wafers A and 2 on which the outer periphery had not been ground. On the other hand, the top of the bonded wafer with the unbonded outer peripheral part removed and 1
No. 5 had no chipping. No difference was observed between wafers with and without an oxide film.

A second embodiment of outer circumferential grinding is shown in FIG. In this case, a portion A of the second wafer 12 with a thickness tA remains above the bonding surface.

If tA is thin, for example less than 50μ, chipping may occur, so the first embodiment shown in FIG. 2 is more suitable.

Furthermore, there is a shape shown in FIG. 4 as a third embodiment.

In this case, the amount of grinding in the diameter direction of the wafer is the same as in the above embodiment, but the amount of grinding in the depth (thickness) direction of the wafer is changed to a depth where the diameter of the first wafer (thickness to) 11 does not change. Sa, that is, t. The outer periphery is ground to a depth that leaves a thickness of 72 mm or more. As a result, the unbonded portion can be almost completely removed regardless of the dimensional accuracy during grinding.

[Effects of the Invention] When the first and second wafers are closely attached to form a bonded wafer that is fixed together, a gap is created due to the beveled surface and the surface sag, and an unbonded outer peripheral portion is created around the gap. This caused chipping and cracking of the wafer during the device manufacturing process. In the present invention, the diameter of the first wafer is left unchanged, and the unbonded outer peripheral portion where the first wafer and the second wafer face each other with a gap in between is removed, so there is no need to reduce the diameter of the wafer. In addition, it has become possible to supply a wafer without an unbonded outer periphery, that is, a bonded wafer without chipping or cracking of the outer periphery.

As a result, when bonding wafers with a diameter of 125 μΦ, it is now possible to use the pellet process with a wafer of 125 μΦ instead of the 100 amΦ in the past, and the chip forming area has also been reduced to about 1.4 in terms of the above diameter ratio. I was able to double it.

Moreover, in order to produce a bonded wafer of 10011 IIφ, two wafers of 125III1φ were conventionally used, but now two wafers of 100 mmφ are required, and the material cost can be reduced.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view including the outer periphery of a bonded wafer used in an embodiment of the present invention, FIG. The same figure (b
) is a grinding process, (c) is a partial sectional view of the bonded wafer after grinding, (d) is a plan view of the bonded wafer after grinding, and FIGS. 3 and 4 are diagrams showing the process of the present invention. 5 is a sectional view showing the manufacturing process of the bonded wafer according to the present invention and the conventional bonded wafer, and FIG. 6 is a partial sectional view of the bonded wafer of the conventional bonded wafer including its outer periphery. It is a diagram. 11...first semiconductor substrate, upper layer, 14. Above...
adhesive semiconductor substrate, 12... second semiconductor substrate, 13.
... Oxide film, 16... Beveled surface, dI, i
a...Aperture, surface ABC, surface AB''C'...Unbonded outer peripheral surface. (a) Figure (b) Figure (a) (b)

Claims (1)

[Scope of Claims] 1. Mirror-polished main surfaces of first and second semiconductor substrates whose side walls are beveled, or mirror-polished main surfaces with an oxide film on at least one of the substrate main surfaces. A step of forming a bonded semiconductor substrate whose surfaces are brought into close contact with each other by heat treatment, and a diameter of the first semiconductor substrate of the bonded semiconductor substrate remains unchanged, and a gap is formed between the first semiconductor substrate and the second semiconductor substrate. A method for manufacturing a semiconductor substrate, comprising the step of: grinding a side wall of the bonded semiconductor substrate so that there is no unbonded outer peripheral portion facing each other with the bonded semiconductor substrate in between.