JP3171316B2 - Method of manufacturing PDA - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing a PDA using an SOI substrate.

[0002]

2. Description of the Related Art A semiconductor substrate having a semiconductor layer formed on an insulating layer is called an SOI (Semiconductor On Insulator). The SOI substrate and its manufacturing method are described, for example, in Japanese Patent Application Laid-Open No. 4-243132. A photodiode array (PDA) can be manufactured using the SOI substrate described here.

[0003]

FIGS. 1 (a) to 1 (c) are process cross-sectional views showing the principle for manufacturing an SOI substrate described in the above-mentioned Japanese Patent Application Laid-Open No. 4-243132.
(a) to (e) are process sectional views for trial production of a PDA by applying the principle of the related art, and FIG. 3 is an enlarged view of an area A in FIG. 2 (d). It is an expanded sectional view of a cut part.

FIG. 4 shows a conventional PDA prototype PDA.
FIG. FIG. 4A is an enlarged cross-sectional view of the PDA showing a void formed under the aluminum metal film, and FIG. 4B is an aluminum wiring edge showing that the aluminum metal wiring is etched from the back side. It is a perspective view. The same reference numerals are the same objects throughout the drawings.

Next, the principle of the above-mentioned prior art will be described with reference to FIGS.
This will be described with reference to FIG. (Step 1-FIG. 1 (a)) Two silicon single crystal wafers each having a silicon oxide film formed on one surface are bonded together, and one silicon single crystal wafer is ground and polished to make it thin. Support substrate 1 consisting of a tie layer
Silicon oxide film (Sio ₂ ) 2 formed on the surface
And a silicon single crystal layer (S
An SOI substrate composed of (i single crystal layer) 3a is obtained.

(Process FIG. 2-FIG. 1 (b)) A V-shaped groove 4 having a taper is formed in the silicon single crystal layer 3 a of the SOI substrate to expose the silicon oxide film 2.

(Step 3-FIG. 1C) A silicon oxide film 5 is deposited on the surface of the SOI substrate.

Step 1-3 in the prior art principle
When an actual PDA is prototyped by applying the above method, as shown in FIGS. 2 (b) to 2 (c), the silicon oxide film 6 is removed when the mask 6 made of the silicon oxide film used for etching the silicon single crystal layer 3a is removed. 2 is also etched to produce an undercut A below the lower end of the element region 3b. As shown in FIGS. 2 (d) and 3, even if the passivation silicon oxide film 5 is subsequently grown, this undercut A
It does not disappear and the undercut B remains.

As shown in FIG. 2E, when an aluminum metal film (Al metal film) 10a is formed here, FIG.
As shown in FIG. 7, a tunnel-shaped gap C is formed between the aluminum metal film 10a and the passivation silicon oxide film 5. Next, as shown in FIG. 4 (b), when an unnecessary portion of the aluminum metal film 10a is removed by wet etching to form an aluminum metal wiring 10b, an etchant enters from the void C and the aluminum metal wiring 10b is formed.
Will be etched from the back side. For this reason, there is a problem that the possibility of occurrence of wiring failure such as disconnection of a step increases.

[0010] It is an object of the present invention to provide a method of manufacturing a PDA using an SOI substrate, in which a defect of an aluminum metal wiring caused by an undercut formed at a lower end portion of an element region made of a single crystal silicon layer is prevented. And

[0011]

Means for Solving the Problems The present inventor has found that in a method of manufacturing a PDA using an SOI substrate, etching occurs to remove a mask made of a silicon oxide film.
When the cause of the defect of the Al metal wiring caused by the undercut was eagerly investigated, it was found that the aluminum metal film did not easily reach the undercut portion on the silicon oxide film during the formation of the aluminum metal. That a defect occurs, and
For this reason, by wet etching of the Al metal film,
It has been clarified that the etchant enters the undercut portion and etches the Al metal film from the back side, thereby causing a wiring defect such as a step disconnection.

Based on this fact, the inventor of the present invention has made intensive studies to prevent the aluminum metal film from running into the undercut portion formed on the surface of the silicon oxide film. In order to increase the sensitivity of the silicon nitride film formed as an anti-reflection film on the surface of the light-receiving part and formed into the undercut part, the aluminum metal film is On the silicon nitride film, it goes around well to the undercut part, and there is no gap in the undercut part, and even when the etchant enters the undercut part when etching the aluminum metal film, the etchant enters from the gap of the aluminum metal wiring, Discovering that etching of aluminum metal wiring from the back side can be prevented, Which resulted in the completion of the gun invention.

That is, the present invention relates to a method of manufacturing a PDA by applying aluminum metal wiring to an SOI substrate having an undercut portion formed below a lower end portion of an element region, before forming an aluminum metal film. In advance, a silicon oxide film formed on a support substrate, and a silicon nitride film formed on both surfaces of a silicon oxide film formed on an element region including a silicon single crystal layer,
A method of manufacturing a PDA, characterized in that a silicon nitride film is introduced into an undercut portion.

[0014]

FIG. 2 is a block diagram showing an embodiment of the present invention.
This will be described with reference to (a) to (c) and FIGS. 5 (a) to (d). Fig. 5 (a) ~
(d) is a process sectional view of the method for manufacturing a PDA in the present invention. FIG. 6 is an enlarged cross-sectional view of the portion A in FIG. The same reference numerals are the same objects throughout the drawings.

According to the prior art shown in FIGS. 2 (a) to 2 (c),
An SOI substrate was formed. As shown in FIG. 2 (a), two single-crystal silicon wafers 1, 3 having a silicon oxide film 2 formed on one surface are bonded together, and one of the single-crystal silicon wafers 3 is ground to about 20 μm. I made it thin.

As shown in FIGS. 2 (b) to 2 (c), after oxidizing the surface of the silicon single crystal layer 3, it was patterned by a usual photolithography technique to form a silicon oxide film mask. Next, the silicon single crystal layer 3 was etched with an aqueous solution of potassium hydroxide to form a tapered groove 4 having a V-shaped cross section 4 to expose the silicon oxide film 2, and then the silicon oxide film mask 6 was removed. .

As shown in FIG. 5A, N-type and P-type metals are ion-implanted into a silicon single crystal layer to form a silicon element region 3b. A silicon oxide layer 5 functioning as a passivation oxide film is formed on the crystal 3 by a thermal oxidation method to a thickness of 0.1 μm.
It was formed in thickness.

As shown in FIG. 5B, on the passivation silicon oxide film 5, a silicon nitride film (SiN film) 9 used as an anti-reflection film of a light receiving portion was formed by a conventional method.

As shown in FIGS. 5C and 5D, after the electrode connection port 13 is opened in the silicon nitride film 9 and the passivation silicon oxide film 5, the aluminum metal film 10a is formed.
Was formed by a well-known vapor deposition method. Next, unnecessary portions of the aluminum metal film 10a (not shown) are removed by wet etching, and aluminum wiring 10b is removed.
Was formed to obtain PDA.

As shown in FIG. 6, even if unnecessary portions of the aluminum metal film 10a are removed by wet etching to form the aluminum metal wiring 10b, FIG. The void portion C as shown is not formed,
Therefore, the etchant did not enter from the void C and the aluminum metal wiring 10b was not etched from the back side. For this reason, a PDA free of wiring defects such as disconnection was obtained.

[0021]

According to the present invention, a silicon oxide film formed on a supporting substrate by using a silicon nitride film used as an antireflection film of a light receiving portion;
And forming a film over both surfaces of a silicon oxide film formed on an element region composed of a silicon single crystal layer and entering into an undercut portion, when forming an aluminum metal film, the aluminum metal film becomes a silicon nitride film. Above, it goes around well to the undercut part, and no voids are created in the undercut part, so even if the etchant enters the undercut part when etching the aluminum metal film, it is possible to etch the aluminum metal wiring from the back side. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view showing a principle for manufacturing a conventional SOI substrate.

FIG. 2 is a process cross-sectional view for producing a prototype of a PDA by applying the principle of the related art.

FIG. 3 is an enlarged cross-sectional view of a part of FIG. 2 (d).

FIG. 4 is an SEM observation diagram of a PDA in a conventional PDA prototype.

FIG. 5 is a process sectional view showing a manufacturing process of the PDA in the present invention.

FIG. 6 is an enlarged cross-sectional view of a portion A in FIG. 5 (d).

[Explanation of symbols]

Reference Signs List 1 Si support substrate 2 SiO ₂ film 3 a Si single crystal layer 3 b Si element region 4 V-shaped groove A undercut 5 passivation SiO ₂ film 6 SiO ₂ mask B undercut portion 9 SiN film 10 a Al metal film C void 10 b Al metal wiring 11 Groove bottom 12 Element region slope

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 31/10-31/119 H01L 27/14-27/148 H01L 21/306-21/308

Claims (1)

(57) [Claims] In a method of manufacturing a PDA by applying an aluminum metal wiring to an SOI substrate having an undercut portion formed below a lower end of an element region, a support is required before forming an aluminum metal film. A silicon nitride film is formed on both surfaces of a silicon oxide film formed on a substrate and a passivation silicon oxide film formed on an element region formed of a silicon single crystal layer, and a silicon nitride film is formed on an undercut portion. A method for manufacturing a PDA, comprising: