JPH01270231A - Etching method - Google Patents

Abstract

PURPOSE:To enable forming a plurality of holes in various shapes for a single aperture, by making the section of a first etching mask almost triangular, forming the aperture of a second etching mask in a part corresponding with the first etching mask, and performing anisotropic etching. CONSTITUTION:The section of a first etching mask 12 is nearly triangular, and the aperture 16a of a second etching mask 16 is formed in a part corresponding with the first etching mask 12. As a result, a beam 17, for anisotropic etching, entering the first etching mask 12 via the aperture 16a of the second etching mask 16 is reflected in two or more oblique directions by the first etching mask 12. Thereby, a plurality of holes can be formed by a single aperture, and holes having various shapes can be formed, by setting the reflection direction of the beam 17 for anisotropic etching by selecting the three-dimensional shape of the first mask 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an etching method for forming holes in a layer to be etched.

[Summary of the invention]

The present invention provides an etching method as described above, in which the cross section of the first etching mask is approximately triangular and the opening of the second etching mask is formed in a portion corresponding to the first etching mask. By performing etching, it is possible to form a plurality of holes in a single opening in various shapes.

[Conventional technology]

For example, in recent DRAMs, in order to increase the degree of integration, a trench structure has been proposed in which capacitive elements and switching transistors are three-dimensionally formed using trenches (for example, in the monthly Sem1-conductor
r World 198B, 2 Press Journal Inc. PP
, 31-36).

[Problem to be solved by the invention]

However, the trench described above is formed by RIE,
Only one trench is formed per opening in the etch mask.

Therefore, in order to increase the capacitance of the capacitive element, it is necessary to form a deep trench, but this is not easy. As a result, in the DRAM having the trench structure as described above, the capacitance of the capacitive element is not necessarily sufficient, and high reliability cannot necessarily be obtained.

Furthermore, since the trench has a simple cylindrical shape, the function of the trench as an active element is also limited.

[Means to solve the problem]

In the etching method according to the present invention, a first etching mask 12 having a substantially triangular cross section is etched on a first layer ll to be etched.
a step of selectively forming a second etching target l1i15 on the first etching target layer ll covering the first etching mask 12; forming a second etching mask 16 having an opening 16a in a portion on the second workpiece/notching layer 15; 1
The etching target layer 15 and 11 are anisotropically etched and notched, respectively.

[Effect]

In the etching method according to the present invention, the cross section of the first etching mask 12 is approximately triangular, and the opening L6a of the second etching mask 16 is etched by the first etching mask 12.
Since the beam 17 for anisotropic etching enters the first etching/notching mask 12 through the opening 16a of the second etching mask 16,
is reflected by the first etching mask 12 in two or more diagonal directions.

〔Example〕

Hereinafter, first to third embodiments of the present invention will be described with reference to FIGS. 1 to 3.

Figure 1 shows the first hole for forming a hole with a rectangular planar shape.
An example is shown. In this first embodiment, as shown in FIG. 1A, a 5in2 film 12 or the like is deposited on a Si substrate 11, and a resist film 13 is further applied on this 5iOz film 12. As the material for this resist film 13, a material with low resolution in photosensitive reaction is used.

Next, an exposure mask 14 having a rectangular planar shape is formed on a portion of the resist film 13 corresponding to a portion where a hole is to be formed by etching. Note that this exposure mask 14 is formed by lowering the numerical aperture of the exposure device. Therefore, the exposure mask 14 is formed with a blurred peripheral portion.

If the resist film 13 is exposed and developed in this state, the resolution of the material of the resist film 13 is low as described above, and the peripheral part of the exposure mask 14 is blurred, so as shown by the dashed line in FIG. 1A, The resist film 13 remains in a ridge shape.

Note that the inclination angle of the resist film 13 remaining in the ridge shape can be selected to a desired value by selecting the resolution of the material of this resist film 13 and the numerical aperture of the exposure apparatus for forming the exposure mask 14.

Next, the resist film 13 and the 5i(h film 12) are etched using an etching gas such that the etching selectivity of the 5i(h film 12 and the resist film 13 is 1). As shown in , the SiO2 film 12 film thickness 2
remain in shape.

Next, as shown in FIG. 1C, the 5iOz film 12 is covered with S.
A Si epitaxial layer 15 is formed on the entire surface of the i-substrate 11, and a Sing film 16 is further formed on the Si epitaxial layer 15.

Next, as shown in FIG. 1D, with a Sing film of 16 film type 6,
An opening 16a is formed in the portion where the SiO□ film 12 is left in a ridge shape.

Then, RIE is performed on the Si epitaxial layer 15 and the Si substrate 11 using the 5iOz film 16.12 as an etching mask. Then, when the 5iOz film 12 is exposed, the etching beam 1 is applied as shown in FIG. 1E.
7 is placed between 12 SiO□ films.

As a result, two rows of holes 21a are formed in the Si epitaxial layer 15 and the Si substrate 11 along the ridge-shaped 5iOz film 12.
, 21b is formed. Note that this is removed at the same time as the 2iO2 film 16 between the SiO□ films 12 is removed.

If a DRAM capacitive element is formed in the holes 21a and 21b, for example, a sufficient storage charge capacity can be obtained even if the hole 21 is relatively shallow. Furthermore, it is also possible to form different active elements in each of the holes 21a and 21b.

2 and 3 show the second and third embodiments, respectively. If the planar shape of the exposure mask 14 formed in the step of FIG. 1A in the first embodiment is made triangular or circular, the second
As shown in FIG. A and FIG. 3A, it is possible to leave two conical or conical shapes between the 12 SiO□ films.

Therefore, if RIE is performed on these Sing films 12 in the same manner as in the first embodiment, holes 22 and 23 as shown in FIGS. 2B and 3B are respectively formed.

〔Effect of the invention〕

In the etching method according to the present invention, the anisotropic etching beam incident on the first etching mask through the opening of the second etching mask is reflected by the first etching mask in two or more diagonal directions. , multiple holes can be formed with a single opening.

In addition, since the beam for anisotropic etching is reflected in two or more diagonal directions, if the three-dimensional shape of the first mask is selected and the direction of reflection of the beam for anisotropic etching is selected,
Holes of various shapes can be formed.

[Brief explanation of the drawing]

1 is a side sectional view sequentially showing a first embodiment of the present invention, FIGS. 2A and 3A are perspective views of a first etching mask used in the second and third embodiments, respectively, and FIG. 2B and third
Figure B is a perspective view of holes formed in the second and third embodiments, respectively. In addition, in the symbols used in the drawings, 11・---1-・・・・Si substrate 12～・−
......--5iO□ film 15-...
−・−・Si epitaxial layer 16 −・−・−・−・・
-5iO□ film 16a--Aperture 17--Beam.

Claims (1)

Scope of Claims: A step of selectively forming a first etching mask having a substantially triangular cross section on the first layer to be etched; forming a second etching target layer on the second etching target layer; forming a second etching mask having an opening in a portion corresponding to the first etching mask on the second etching target layer; and the second etching mask using the first etching mask.
and a step of anisotropically etching the first layer to be etched.