JPS6075587A - Etching method - Google Patents

Abstract

PURPOSE:To form efficiently a flat etched surface by etching alternately with an etching liquid for Si and an etching liquid for an oxidized Si film in the etching of an Si substrate having an uneven oxidized Si film. CONSTITUTION:An upper Si 3 is firstly etched with a nitric and fluoric acid liquid, etc., and the protruding part 4 of an oxidized Si film 1 is exposed in the etching of an Si substrate 2 having the uneven oxidized Si film 1 at the inside. The material is washed with water, and etched with an etching liquid for the oxidized Si film such as an aq. soln. of ammonium fluoride to remove the exposed protruding part 4 of the oxidized Si film by etching. After washing with water, the material is etched again with the nitric and fluoric acid liquid for Si, and the exposed part of the oxidized Si film is etched with the aq. soln. of ammonium fluoride. By repeating alternately the process, a flat etching having no level difference between the Si 3 and the oxidized Si film 1 is efficiently carried out in a short time.

Description

[Detailed description of the invention] (1) 〔Technical field〕 The present invention relates to an etching method.

[Background technology]

Generally, a silicon substrate having a silicon oxide film therein is etched using a single etching solution (for example, a nitric-hydrofluoric acid solution). That is, as shown in FIG. 1, when the surface of a silicon substrate 2 having an uneven silicon oxide film 1 therein is etched with the above etching solution, the silicon on the surface side of the silicon substrate 2 is etched as shown in FIG. The portion 3 is etched away, and the convex portion 4 of the internal silicon oxide film 1 comes to protrude from the surface. Therefore, the surface of the silicon substrate 2 becomes extremely uneven due to the protrusion of the convex portions 4 of the silicon oxide film 1.

As described above, regarding the silicon substrate 2 in which the convex portions 4 of the silicon oxide film 1 protrude from the surface, the unevenness cannot be eliminated even if the silicon oxide film 1 is subsequently etched. As described above, in the conventional etching using a single etching solution, it was not possible to flatten the surface of the silicon substrate 2 having the silicon oxide film 1 therein as described in (2) above. On the other hand, there is also a method of polishing the silicon substrate 2 as described above. However, when physical polishing is used, it is difficult to finely adjust the polishing thickness, and furthermore, problems such as the occurrence of crystal defects on the polished surface occur. Therefore, it is desirable to perform etching on the silicon substrate 2 having the silicon oxide film 1 inside. Problems such as uneven surfaces occur, and efforts are being made to solve this problem.

[Purpose of the invention]

An object of the present invention is to form a flat etched surface by etching a silicon substrate having a silicon oxide film therein.

[Disclosure of invention]

This invention is an etching method in which a silicon substrate having a silicon oxide film therein is prepared, and the surface of the silicon substrate is (3) etched. a first etching step for etching until a part of the silicon oxide film is exposed; and a second etching step for etching the exposed part of the silicon oxide film with an etching solution for etching the silicon oxide film. The gist of this is an etching method characterized by the following.

In other words, using the two types of etching solutions mentioned above,
By separately etching the silicon portion of the silicon substrate and the exposed portion of the silicon oxide film, a flat etched surface can be formed.

Next, the present invention will be explained based on examples.

That is, as shown in FIG. 3, the surface of a silicon substrate 2 having an uneven silicon oxide film 1 therein is etched with an etching solution (for example, nitric-hydrofluoric acid solution) for etching the silicon portion 3, as shown in FIG. Erasing is performed until the convex portions 4 of the internal silicon oxide film 1 appear. Then, water washing is performed when the convex portions 4 of the oxide film 1 appear. Next, the exposed convex protrusion 4 of the oxide film 1
is etched using an etching solution for etching the oxide film 1 (for example, ammonium fluoride aqueous solution) as shown in FIG. After the etching of the protruding portion of the oxide film 1 is finished in this way, it is washed with water, and the surface of the silicon substrate 2 is etched again using an etching solution for etching the silicon portion 3. Then, the silicon portion 3 on the surface side of the silicon substrate 2 is etched to expose the convex portion 4 of the silicon oxide film 1 (the top portion has been etched by the previous etching), and then washed with water to remove the exposed silicon oxide. Etching is performed on the convex portion 4 of the film 1 using an etching solution for etching the silicon oxide film 1. Rinse with water after etching. By repeating these steps, etching is performed to a predetermined thickness. In this case, by shortening the etching time for each of the etching of the silicon portion 3 and the etching of the silicon oxide film 1 and alternating them (5), flat etching can be achieved without creating a step. You will be able to obtain a surface. Note that the time required for etching the silicon portion 3 and the silicon oxide film 1 is set at such a rate that the same thickness is etched for each.

In this way, two types of etching liquids are used properly, and one etching the silicon part 3 and the other etching the silicon oxide film 1.
By shortening the etching time and repeating this process alternately, a flat etched surface can be obtained without creating a step between the silicon oxide film 1 and the silicon portion 3. Therefore, difficulties in the subsequent exposure process etc. can be solved.

〔Effect of the invention〕

As described above, the present invention provides an etching method in which a silicon substrate having a silicon oxide film therein is prepared and the surface of the silicon substrate is etched using an etching solution for etching the silicon portion. A first etching step (6) in which the silicon oxide film is etched until a part of the internal silicon oxide film is exposed, and a second etching step in which the exposed part of the silicon oxide film is etched with an etching solution for silicon oxide film etching. This process makes it possible to form a flat etched surface.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a silicon substrate having a silicon oxide film therein, FIG. 2 is a sectional view of a silicon substrate after etching by a conventional method, and FIG. 3 is a sectional view of a silicon substrate used in an embodiment of the present invention. , FIGS. 4 to 6 are explanatory diagrams illustrating the etching state. 1... Silicon oxide film 2... Silicon substrate 3.
...Silicon Department Representative Patent Attorney Takehiko Matsumoto (7) Figure 3 3

Claims (2)

[Claims] (1) An etching method in which a silicon substrate having a silicon oxide film inside is prepared and the surface of the silicon substrate is etched, and the surface of the silicon substrate is etched using an etching solution for etching the silicon portion. The method is characterized by comprising a first etching step in which the silicon oxide film is etched until a part of the silicon oxide film is exposed, and a second etching step in which the exposed part of the silicon oxide film is etched with an etching solution for etching the silicon oxide film. Etching method. (2) The etching method according to claim 1, wherein the etching time in the first etching step and the second etching step is shortened, and the first etching step and the second etching step are alternately repeated.