JP2857302B2 - Diffusion wafer manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a diffusion wafer.

[0002]

2. Description of the Related Art Some silicon wafers have a diffusion layer of impurities formed on one side, and these are generally called diffusion wafers. This diffusion wafer is mainly used as a substrate of a triple diffusion type transistor because an accurate diffusion concentration and diffusion depth are secured. Conventionally,
This type of diffusion wafer has been manufactured by the following steps (see FIGS. 3A to 3E). First, a plurality of wafers each having a diffusion layer formed on both surfaces are prepared (FIG. (A)), and each wafer is bonded using an adhesive to form an ingot (FIG. (B)). Next, the ingot is adhered to the base member using an adhesive (FIG. 3C). Further, the central portion of each silicon wafer diffused on both sides constituting the ingot is cut together with the base member (see FIG. 4D). Thereafter, the respective adhesives were removed (FIGS. (E) and (f)) to obtain a single-sided diffusion wafer (FIG. (G)). Heretofore, a water-soluble adhesive has conventionally been used for bonding the base member, while a non-water-soluble adhesive having a lower softening point than that for bonding the base member has been used for bonding the wafer.

[0003]

In the above-described conventional method, the adhesive used for bonding each wafer has a lower softening point than the adhesive for bonding the base. In addition, the adhesive applied between the wafers softens, and each wafer may be displaced or tilted on the base member. When each wafer is cut in such a manner that the position shift and the inclination are generated, there is a problem that the parallelism of the obtained single-sided diffusion wafer is reduced.
In addition, an alkaline solution is used to remove the water-soluble adhesive, while a chlorine-based organic solvent is used to remove the non-water-soluble adhesive. Cleaning process is required, and there are environmental and handling problems when the chlorine-based organic solvent is discarded. The present invention has been made to solve such a problem of the prior art, and can improve the parallelism of the obtained single-sided diffusion wafer, simplify the process of removing the adhesive, and furthermore, An object of the present invention is to provide a method for manufacturing a diffusion wafer that does not require a chlorine-based organic solvent for removing the agent.

[0004]

To achieve the above object, the present invention provides the following method. First, a double-sided diffusion wafer is formed by diffusing impurities on both sides of a plurality of silicon wafers. That is, for example, an N-type silicon ingot is sliced and wrapped to form an N-type wrapped wafer 1 (FIG. 1A), and a diffusion layer (diffusion) of an N-type impurity is formed on both surfaces of the wrapped wafer 1. A depth of 70 to 250 μm) 2 is formed (see FIG. 3B).
Note that the conductivity type of the wrapped wafer or the diffusion layer may be a P-type as necessary. Next, a plurality of silicon wafers diffused on both sides are bonded with an adhesive 3 to form an ingot (FIG. (C)). Further, the ingot is bonded to the base member 5 using the adhesive 4 (FIG. 4D).

Next, the central part of each silicon wafer diffused on both sides constituting the ingot is cut (FIG. 1E). For this cutting, for example, the same method as the cutting of the silicon ingot pulled up by the CZ method can be applied. That is, the silicon ingot adhered to the base member is mounted on a cutting machine, and cut to a base member together with the ingot by a diamond blade. Thereafter, the adhesive 3 applied between the silicon wafers and the adhesive 4 applied between the ingot and the base member 5 are removed to obtain a single-side diffused diffusion wafer (FIG. 1F).

[0006] In the method of manufacturing a diffusion wafer including such a step, the present invention provides a method in which the adhesive for bonding between the silicon wafers and the adhesive for bonding between the ingot and the base member are water-soluble adhesives. The adhesive for bonding between the silicon wafers has a softening point higher than that of the adhesive for bonding between the ingot and the base member. Here, as a main component of the adhesive used for bonding between a plurality of silicon wafers diffused on both sides, for example, purified rosin and dibasic acid-modified rosin can be mentioned.

[0007]

In the present invention, a water-soluble adhesive is used for bonding between a plurality of silicon wafers diffused on both sides and bonding between the ingot and the base member. Therefore, since both of these adhesives can be removed with an alkaline detergent or an alcohol detergent,
A common cleaning step can reduce the number of steps.
Moreover, since it is not necessary to use a chlorine-based organic solvent, there is no need to perform a difficult waste liquid treatment. In addition, since an adhesive showing a softening point higher than that of the adhesive for bonding the base member is used for bonding between the plurality of silicon wafers diffused on both sides, when the ingot is bonded to the base member, the gap between the silicon wafers is reduced. The applied adhesive does not soften,
There is no possibility that each silicon wafer will be displaced or tilted on the base member.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. However, the present invention is not limited by the following examples. First, a plurality of N-type double-sided diffusion wafers were prepared (FIG. 2A). These double-sided diffusion wafers
Heat to 0 to 120 ° C and apply 80 to 1 to the bonding surface of each wafer.
An ingot was prepared by dropping 1 to 5 g of a water-soluble adhesive heated to 60 ° C., bonding the respective adhesive surfaces, and applying pressure at ² to 4 kg / cm ² in a direction orthogonal to the adhesive surface. (FIG. 2B). The softening point of the water-soluble adhesive used at this time was 75 to 85 ° C. The produced ingot was adhered to the base member using a water-soluble adhesive having a softening point of 68 to 73 ° C (FIG. 3C). Thereafter, the wafer was mounted on a cutting machine, and the central portion of each diffused wafer constituting the ingot, which had been diffused on both sides, was cut together with the base member (FIG. 4D).

Then, in order to remove the adhesive interposed between each wafer and between the wafer and the base member, 0.5% of sodium hydroxide and 1% of a surfactant are added at 60 to 70 ° C.
Then, the wafer with the base member was cleaned using a cleaning agent heated as shown in FIG. As a result, a single-sided diffusion wafer was obtained (FIG. 1F). The single-sided diffusion wafer thus obtained had a wafer parallelism of 5 to 35 μm. On the other hand, the parallelism of the single-sided diffusion wafer manufactured by the above-described conventional technique was 80 to 150 μm. Further, in the prior art, since paraffin was used as the adhesive, it was necessary to wash with a chlorine-based organic solvent, for example, triethane. As described above, in the present embodiment, it was possible to improve the cutting accuracy, eliminate the chlorine-based organic solvent, and simplify the cleaning process, as compared with the related art.

[0010]

As described above, according to the method of the present invention, it is possible to manufacture a single-sided diffusion wafer having a high degree of parallelism, to simplify the step of removing the adhesive, and to reduce the adhesive. Since a chlorine-based organic solvent is not required for removal, workability and environmental performance can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing each step in a method for manufacturing a diffusion wafer according to the present invention.

FIG. 2 is also a flowchart.

FIG. 3 is a flowchart showing a conventional method for manufacturing a diffusion wafer.

[Explanation of symbols]

 Reference Signs List 1 N-type wrapped wafer 2 Diffusion layer 3, 4 Adhesive 5 Base member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/22 H01L 21/02

Claims (1)

(57) [Claims] 1. A step of diffusing impurities on both surfaces of a plurality of silicon wafers, a step of bonding the plurality of silicon wafers diffused on both sides with an adhesive to form an ingot, and a step of bonding the ingot to a base using an adhesive. The step of bonding to the member, the step of cutting the central portion of each silicon wafer diffused on both sides constituting the ingot, the adhesive applied between the silicon wafers, and the adhesive applied between the ingot and the base member Removing the one-sided diffusion wafer to obtain a diffusion wafer, wherein the adhesive for bonding between the silicon wafers and the adhesive for bonding between the ingot and the base member are dissolved in water. The adhesive for bonding between the silicon wafers and the silicon wafer is an adhesive for bonding between the ingot and the base member. A method for manufacturing a diffusion wafer, characterized by using a material having a higher softening point.