JPS5851414B2 - Youkiyokusankahouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of anodic oxidation, and more particularly to a method of anodic oxidation of a semiconductor film using a corrosion-resistant film as a mask and an electrode.

When anodizing silicon, a nitride film is generally used as a mask, and as a charge supply method, platinum is deposited on the back surface of the silicon substrate, and the silicon surface is selectively etched or oxidized in a hydrofluoric acid solution using silicon as an anode. method is known.

In the prior art, it is extremely difficult to selectively oxidize or etch P-type silicon on an N-type silicon substrate or a silicon film on an insulating substrate as an anode.

This is because in the latter case, it is impossible to obtain conduction with the substrate Si even if a platinum electrode is provided on the back surface, and if P-type silicon is provided on an N-type silicon substrate, the surface of the n-type silicon substrate This is because if a platinum electrode is used as an anode, only a small amount of current will flow, making it difficult for a reaction to occur.

Furthermore, if an attempt is made to supply charge from the side surface of the wafer, the path through which the current flows becomes longer, resulting in uneven oxidation.

The purpose of the present invention is to selectively anodize or anodize a P-type silicon film on an N-type silicon substrate, silicon on an insulator, etc., which were conventionally thought to be difficult to anodic oxidize or anodically etch. To provide a possible method of oxidation.

. The present invention will be explained by taking as an example a case where a P-type silicon film on a substrate is anodized.

A corrosion-resistant conductor 3 such as platinum is deposited on a P-type silicon film 2 on an N-type substrate 1 .

Furthermore, an acid-resistant material 4 such as silicon dioxide is deposited thereon, and a predetermined pattern is obtained by a normal PEP process.

Next, using this SiO2 as a mask, platinum is selectively removed with acid as shown in FIG. 1A.

The 5in2 used as a mask is removed with N H4F, and the patterned platinum is used as a mask for anodization and a portion thereof is used as an electrode to selectively anodize the P-type silicon on the n-type substrate.

At this time, only the part not masked by platinum is shown in Figure 1B.
A reaction film 5 is formed as shown in FIG.

In the case of a semiconductor IC, as shown in FIG. 2, when etching is desired to leave an isolated pattern 6, a current can be supplied to the platinum mask of the isolated pattern 6 by using a scribe line T, which serves as a wiring (charge supply source) over the entire wafer surface, as an anode. You can achieve your goal without it.

In ICs using P-type silicon on an N-type substrate, it has been difficult to apply insulation isolation technology using porous silicon, which is a product of an anode reaction.

By using the present invention, it has become possible to create a faster IC using an insulation separation method using porous silicon for an IC using P-type silicon on an N-type substrate.

Similarly, using silicon on an insulating substrate such as dielectric isolation,
When making ICs, there was a limitation that insulation isolation technology using porous silicon produced by an anodic reaction could not be applied, but by using the present invention, insulation isolation method using porous silicon can be applied to LSIs on insulating substrates. It has also become possible to use it to create faster ICs.

As a second embodiment of the present invention, a case will be described in which a P-type silicon layer on an N-type silicon substrate is anodized.

Generally, when silicon is anodized, a positive voltage is applied to the silicon substrate with respect to a platinum electrode in hydrofluoric acid HF.

However, when anodizing a P-type silicon layer on an N-type silicon substrate, if a positive potential is applied to the N-type silicon substrate,
A voltage in the opposite direction is applied to the P-type silicon layer, so that almost no current flows, and anodic oxidation of the P-type silicon layer hardly progresses and progresses in the N-type silicon layer.

Therefore, in order to perform anodic oxidation only on a desired portion of the P-type silicon layer, a platinum pattern that serves as an anodization-resistant mask and forms a current path may be provided at a location that will become a scribe line in the future, for example.

It goes without saying that other corrosion-resistant metals may be used instead of platinum.

[Brief explanation of drawings]

FIGS. 1A and 1B are process sectional views for explaining an embodiment of the present invention, and FIG. 2 is a plan view for explaining how to take out an electrode in the present invention. In the figure, 3...conductor pattern.

Claims (1)

[Claims] 1. An anodizing method characterized by anodizing a semiconductor layer using a corrosion-resistant conductor as a mask and selectively anodizing the semiconductor layer.