JPS61256621A - Production of bound-type semiconductor substrate - Google Patents

Abstract

PURPOSE:To improve yield ratio and reliability by providing a process where the circumference of a bound semiconductor substrate is grinded and unbound section is removed so as to retain only the section that is firmly bound without producing defects in the subsequent process for the adjustment of thickness. CONSTITUTION:Two sheets of wafer 1 and 2 whose one side is specular-finished are bound at both specular faces with pressure and heat applied. At this time, an unbound section 3 is produced at the circumference of the bound surfaces due to the burr of each substrates. Such bound wafer 10 is mounted on a cylinder grinding machine, and its end face is applied to the end face of a rotary grinding stone 11. The grinding stone 11 is provided with inclination faces 11b and 11c that incline upward in the direction of the circumference with an angle on the both sides of the plane cylinder face 11a. The width of the plane section 11b is slightly made shorter than the thickness of the bound wafer, and the circumferences of the both bound wafers contact with the inclined sections 11b and 11c respectively, forming a chamfered section 7 with reduced diameter.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing an adhesive semiconductor substrate,
In particular, it is used in the production of Dayongkun's power transistors.

(Technical background of the invention and its problems) In manufacturing semiconductor devices, silicon wafers are used and predetermined active regions of transistors are formed through a wafer process that repeats diffusion, oxidation, etching, etc. In particular, for bipolar transistors with high breakdown voltage and saturation current capacity, in order to ensure operation in the active region, a buried diffusion region, which is a high concentration impurity diffusion region, is first formed, and then the active region A diffusion region is formed such that However, this method requires lengthy diffusion and deposition steps and lacks manufacturing stability.

For this reason, a technique has been proposed in which two wafers having different diffusion concentrations are used and bonded together to form one wafer. In other words, two wafers having a thickness of 400 to 600 μm are processed, for example, as shown in FIG. N-binding is performed with low phosphorus diffusion, lapping and polishing are applied to at least one side of both to create a mirror surface, and by applying pressure and bringing these mirror surfaces into contact, strong adhesion is achieved by the atomic attraction between the two. There is. After this adhesion, high m (1100℃)
) The adhesion strength at the interface is further increased by 2H heat treatment.

Next, the substrate thickness of the n-wafer 2 used as an active region is reduced by grinding, lapping, and polishing to a thickness of 80 to 100 μm, and a wafer process is performed using this to manufacture semiconductor devices. do.

However, this type of bonding process has a problem in that the wafers are often damaged. That is, Fig. 4(a) (
As shown in b), the flatness of each wafer before bonding has decreased due to polishing during mirror finishing, and sagging 4 has occurred particularly at the peripheral edge 3 of the bonding surface, so the bonding is not performed at the time of bonding. Not yet. For this reason, the bonding strength becomes weaker, and when wrapping to reduce the thickness, cracks 5, chips 6, peeling, etc. occur as shown in the front view of Figure 5 (a) and the perspective view of Figure 5 (1)). occurs, resulting in a decrease in yield. Therefore, the effective area for manufacturing the semiconductor device is reduced, or the area where normal adhesion is performed is affected, resulting in deterioration of characteristics and reliability.

[Purpose of the invention]

The present invention was made to solve these problems, and an object of the present invention is to provide a bonded semiconductor substrate with a high yield and high reliability.

[Summary of the Invention] In order to achieve the above object, the present invention includes a process of mirror-polishing at least one side of two semiconductor substrates, and bonding the two semiconductor substrates by bringing the mirror-polished surfaces into contact and applying pressure. This process includes a step of grinding the periphery of the bonded semiconductor substrate to remove the unbonded portion, and by leaving only the strongly bonded portion, it is easier to adjust the thickness later. No defects occur during processing, improving yield and reliability.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings.

As in the conventional example, two wafers 1, 2 . The mirror surfaces are glued together by applying pressure and humidity. At this time, an unbonded portion 3 is generated at the outermost periphery of the bonded surface due to sagging of each substrate.

Such a bonded wafer 10 is mounted on a cylindrical grinder, and as shown in the front view of FIG. Grinding is performed by This grindstone 11 has inclined portions 11b and 11C that rise at an angle toward the outer circumference on both sides of a flat cylindrical surface 11a.

The width of the flat portion 11b is slightly smaller than the thickness of the bonded wafer, and the peripheral edges of both sides of the bonded wafer come into contact with the sloped portions 11b and 11c, respectively, and as the diameter decreases, a chamfered portion 7 is formed. will be done.

During this grinding, the grindstone 11 is rotating at, for example, 350 rpm, and the bonded wafer 10 being ground is given a rotation opposite to this. Grinding ends at a position where the non-bonded portion 3 at the periphery of the bonded wafer is removed. Note that during actual manufacturing, the size of the wafers used in the mass production process is determined in advance, so the diameter is often adjusted to that size.For example, 4-inch (101,6 m) wafers are bonded together. The bonded wafer is finished into a 3-inch (76,2a+s+) wafer by removing the surrounding non-bonded portion.

The grinding device is also equipped with a grindstone following arm that uses both hydraulic pressure and air pressure so that the grindstone follows the wafer being ground.

Glued joint with unbonded parts removed in this way - C10
As shown in the front view of FIG. 2, complete adhesion is performed on the entire surface of wafers 1' and 2', and in the next step, the surface of wafer 2' is lapped as shown in the front view of FIG. Then, polishing is performed to obtain a wafer 2'' whose thickness has been reduced, and a wafer process is performed using this completed bonded wafer 10''.

In the above embodiments, the two wafers to be bonded were made to have approximately the same thickness, but the thicknesses were changed to facilitate processing for reducing the thickness as soon as the bonded wafer was completed. For example, bonding can be performed with one side having a thickness of 500 μm and the other side having a thickness of 300 μm.

Further, in the embodiment, the chamfering process is performed together with the process of removing the unbonded portion, but these processes can be separated.

〔Effect of the invention〕

As described above, according to the present invention, the periphery of a bonded wafer made up of two bonded wafers is ground to remove the unbonded area, so that there are no gaps in the wafers that are left unbonded during subsequent lapping, etc. , cracking, peeling, etc. do not occur, the yield is improved, and there is no adverse effect on normal bonded parts, making it possible to improve the reliability of semiconductor devices formed thereafter.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the method of manufacturing a bonded wafer according to the present invention, and FIG. 2 is a front view showing the state where the unbonded part is removed.
Fig. 3 is a front view of a bonded wafer obtained by the present invention, Fig. 4 is an explanatory diagram showing the state of a conventional bonded wafer after bonding, and Fig. 5 is a thickness adjustment in a conventional bonded wafer. It is an explanatory diagram showing problems when processing. 1.1', 2.2', 2''... wafer, 3...
- Unbonded part, 4... Sag, 7... Chamfered part, 10.
10'10"...adhesive wafer, 11...grinding wheel.

Claims (1)

[Claims] A step of mirror-polishing at least one side of one or two semiconductor substrates, a step of bonding the two semiconductor substrates by bringing the mirror-polished surfaces into contact and applying pressure; A method for manufacturing a bonded semiconductor substrate, comprising: grinding the peripheral edge of the bonded semiconductor substrate and removing the unbonded portion; and adjusting the overall thickness as necessary. 2. The method for manufacturing an adhesive semiconductor substrate according to claim 1, wherein the semiconductor substrate is a circular semiconductor wafer. 3. The method of manufacturing a bonded semiconductor substrate according to claim 1, wherein the grinding is performed to remove the unbonded portion of the peripheral edge and also the sharp portion of the peripheral edge.