JPH0483341A - Processing of semiconductor minute device - Google Patents

Abstract

PURPOSE:To easily process a complicated and minute pattern by selectively etching a semiconductor substrate through using an etchant, of which etching speed changes depending upon the variation of high impurity concentration or difference in conductivity type. CONSTITUTION:Impurity atoms composed of boron atoms are introduced into a semiconductor layer 12 to form a P-type high concentration impurity layer 14. Then, SiO2 film 15 is formed on both sides of Si substrate. After that, etching is conducted by the use of an etchant mainly composed of ethylenediamine, of which etching speed changes abruptly between 10<-1>OMEGA-cm and 10<-2>OMEGA-cm in the P-type layer Si. Then, the Si substrate 11 forming a rack using the SiO2 film 15 as a mask is etched surely. In this case, the low concentration P-type part of an Si epitaxial layer 12 almost remains without being etched. Subsequently, when etching is conducted by the use of the etchant, of which etching speed changes abruptly between resistivities of 10<-1>OMEGA-cm and 10<-2>OMEGA-cm, only he high concentration impurity layer 14 is selectively etched along the direction of thickness of the semiconductor layer 12 so that a square opening 17 with high accuracy can be formed in the semiconductor layer 12.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for processing fine semiconductor devices such as apertures of multi-element photodetecting elements, and aims to provide a processing method that can easily process complex and fine patterns using a semiconductor substrate. , forming a semiconductor layer of a conductivity type opposite to that of the substrate on a semiconductor substrate, forming a high concentration impurity layer in a predetermined pattern on the semiconductor layer, and etching the substrate depending on variations in impurity concentration or differences in conductivity type. It is constructed by selectively etching using an etching solution with varying speed.

[Industrial application field]

The present invention relates to a method for processing semiconductor microdevices, and particularly to a method for processing apertures, etc. of multi-element type photodetecting elements.

In a multi-element type photodetecting device, in order to regulate the amount of light incident on the photodetecting element or to regulate the viewing angle of the incident light, a fine aperture is provided opposite to the detecting element. Aperture is used.

[Conventional technology]

Conventionally, the present applicant has proposed a method of forming such an aperture using a semiconductor substrate such as silicon (Si) in Japanese Patent Laid-Open No. 1-3337.

For example, as shown in FIG. 3(a), this method uses ion implantation or the like to inject P into the surface of a P-type or N-type Si substrate 1.
After forming the top layer 2, a silicon dioxide (SiOz) film 3 is formed on both sides of the substrate. Next, the SiO□ film 3
After forming the ^l film 4 thereon, the A2 film 4 is etched into a predetermined pattern using a resist film as a mask.

Next, using this A42114 as a mask, the SiO□ film 3 is etched into a predetermined pattern.

Furthermore, as shown in FIG. 3(b), the above A! Membrane 4 and 5in2
Hydrofluoric acid (HF) is applied to the upper layer 2 using the film 3 as a mask.
Etching is performed by isotropic etching using a mixture of nitric acid (HNO:l) and acetic acid (CF13COOH).

Next, the back side of the Si substrate 1! After removing the film 4, the third
As shown in Figure (C), a 5i02 film 5 is formed on the back side of the substrate.

Next, as shown in FIG. 3(d), only the Si substrate 1 is selectively etched using an etching solution that does not etch the upper surface layer 2 of the P layer but selectively etch only the P type layer. An aperture is formed by anisotropic etching using the mask as a mask to form an aperture frame 6.

[Problem to be solved by the invention]

By the way, in the above-described conventional method, the above-mentioned upper surface layer 2 is etched along the thickness direction using the above-mentioned isotropic etching solution.

However, if such an isotropic etching solution is used to etch the top layer in the thickness direction, the etching will spread laterally. Therefore, like the aperture of a two-dimensional multi-element photodetector, the pinch is 50 μm.
Even if an attempt is made to form a rectangular opening with a negative side of 20 to 30 μm, the rectangular pattern will become diamond-shaped and the openings will be connected to each other, resulting in an opening with highly accurate dimensions. There is a problem that an aperture having a portion is not formed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for processing a semiconductor microdevice, which eliminates the above-mentioned problems and allows openings for forming apertures to be formed in a predetermined rectangular pattern with high precision.

[Means to solve the problem]

The method of the present invention for achieving the above object includes forming a semiconductor layer of a conductivity type opposite to that of the substrate on a semiconductor substrate, forming a high concentration impurity layer in a predetermined pattern on the semiconductor layer, and changing the impurity concentration of the substrate. Alternatively, it is characterized by selective etching using an etching solution whose etching rate changes depending on the difference in conductivity type.

[For production]

In the method of the present invention, a semiconductor layer of a conductivity type opposite to that of the substrate is formed on the surface of a semiconductor substrate, and a high concentration impurity layer in a predetermined pattern is formed in this semiconductor layer by ion implantation or the like. When the semiconductor layer is etched using an etching solution whose etching rate varies depending on variations in impurity concentration, highly accurate openings can be formed in a predetermined pattern.

In addition, if the substrate is selectively etched using an etching solution whose etching speed changes depending on the conductivity type, the semiconductor layer with a different conductivity type will not be etched with respect to the substrate, so the pedestal can be formed easily and with high precision. An aperture having an opening with a certain size can be easily formed.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1(a), a semiconductor layer 12 made of a P-type St epitaxial layer having a resistivity of 0.1 Ω-G is formed on a P-type Si substrate 11 with a thickness of several tens of μm.
Form to a thickness of m.

Next, a Si film 13 is formed on the substrate by thermal oxidation, and the 5iO1 film 13 is etched into a predetermined pattern by hydrofluoric acid etching using the resist pattern as a mask.

Next, Fig. 1(C) and 1-1' of Fig. 1(C)
As shown in Figure 1 (°C) of the line cross-sectional view, the SiO
Using the film as a mask, impurity atoms made of boron (B) atoms are added to the semiconductor layer 1 using an ion implantation method or a thermal diffusion method.
2 to form a P-type high concentration impurity layer 14 having a resistivity of about io-'Ω-Ω.

Next, as shown in FIG. 1(d), a SiO□ film 15 is formed on both sides of the Si substrate, and a 5i film is formed on the back side of the Si substrate 11.
The 02 film is etched into a pattern for forming a pedestal.

Next, as shown by curve 22 in FIG. 2(b), S of the P-type layer is
Etching is carried out using an etching solution containing ethylenediamine as a main ingredient whose etching rate changes rapidly between 10@-1 Ω@-1 and 10@-2 Ω@-1 at t.

Then, as shown in FIG. 1(e), using the 5iOz film 15 as a mask, the Si substrate 11 serving as the pedestal is reliably etched. At this time, the low concentration P-type portion of the Si epitaxial layer 12 remains almost unetched because the etching solution has anisotropy.

Next, as shown in curve 21 of FIG. 2(a), etching rates such as nitric acid, hydrofluoric acid, and acetic acid, whose resistivity changes rapidly between 10-1 Ω-1 and 10-'' Ω-Ω, are used. When etching is performed using an etching solution consisting of a mixed solution, only the high concentration impurity layer 14 is selectively etched along the thickness direction of the semiconductor layer 12, and as shown in Figure 1), the semiconductor layer 12 is etched with high precision. A rectangular opening 17 can be formed.

The above has been described using an example of manufacturing an aperture for a multi-element type photodetecting element, but if etching is performed using an etching solution that has different etching speeds depending on the impurity concentration or conductivity type of the semiconductor, it is possible to use a semiconductor substrate. For example, the nozzle of an inkjet head, a pressure fluid juicer, or the spiral column of a gas chromatography device can be easily formed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an aperture having a complicated shape can be easily formed with highly accurate opening dimensions, and by using an aperture microfabricated by the method of the present invention, resolution can be improved. It is possible to form a one-dimensional or two-dimensional multi-element type photodetecting element with good properties.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(g) are cross-sectional views and plan views showing the steps of the method of the present invention, and FIGS. Characteristic diagrams FIG. 3(a) to FIG. 3(d) are cross-sectional views showing the steps of the conventional method. In the figure, 11 is a Si substrate, 12 is a semiconductor layer, and 13.15 is a Si substrate.
, a film, 14 a high concentration impurity layer, 16 a pedestal, 17 an opening, and 21 and 22 a characteristic curve of an etching solution. Figure 1 RfI) 2 brim T7re''' and Figure 2

Claims (1)

[Claims] A semiconductor substrate (11) is provided with a semiconductor layer (
12), a high concentration impurity layer (14) of a predetermined pattern is formed on the semiconductor layer (12), and a highly concentrated impurity layer (14) is formed on the semiconductor layer (12).
) is selectively etched using an etching solution whose etching rate changes depending on changes in impurity concentration or differences in conductivity type.