JPS61198632A - Formation of resist pattern undercut - Google Patents

Abstract

PURPOSE:To enable the control of undercut form by a method wherein a resist layer is first exposed to ion beams which pass through said resist layer over a smaller range than a required pattern and next exposed to ion beams accumulated at the surface layer part of said resist layer in accordance with a required pattern. CONSTITUTION:As the first exposure to a resist layer 22, its region in a range narrower by a length l at the eaves than that of the resist pattern to be finally obtained is exposed to a convergent ion beam 25 which passes through the resist layer 22, resulting in the formation of the first exposed part 23. Next, as the second exposure to the resist layer 22, its region in a range corresponding to the resist pattern to be finally obtained is exposed by a depth corresponding to the eaves thickness (t) so as to be lapped over to the first exposed part 23, resulting in the formation of the second exposed part 23. Thereafter, the unexposed part is removed by developing the whole.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a resist pattern undercut shape, and particularly to a method for forming a resist pattern undercut shape for a lift-off method applied to the manufacturing process of semiconductor devices. It is related to the method.

[Conventional technology]

A conventional method for forming this type of resist pattern undercut shape is shown in FIG.

FIGS. 2(a) to 2(d) are cross-sectional views showing the conventional method in the order of steps. That is, in this conventional method, first, a positive resist layer 12 such as AZ135G is coated on the entire surface of a silicon semiconductor substrate 11, and then a baking process is performed as shown in FIG. The exposed portions 12a are selectively formed by exposing the resist layer 12 through a mask or the like (see FIG.
b)) Then, this is immersed in a chemical such as monochrome benzene to create an altered layer on the surface of the resist layer 12 that is difficult to develop due to undercuts! Figure 3 (C))
This is further developed to obtain a resist pattern consisting of a developed area 12b and an undercut altered layer 13a on the surface thereof (FIG. 2(d)).

[Problem that the invention seeks to solve]

For this reason, a preferable undercut shape for this type of resist pattern is as shown in FIG.

The object of the present invention is to precisely form an eave portion 2a formed around the outer circumference of the front surface of a resist pattern 2 on a semiconductor substrate l to a controlled predetermined length and thickness t.

However, undercutting of the resist pattern by the conventional method described above is caused by the deterioration of the deteriorated layer 1 obtained by immersion in chemicals.
3a, it is extremely difficult to control the formation of its shape, and since the altered layer 13a can only be formed thinly on the surface of the developing section 12b, there are problems such as the undercut shape being damaged by heat etc. was there.

The present invention is an attempt to improve these drawbacks of the conventional method, and aims to provide a method for forming a resist pattern in which the formation of an undercut shape can be controlled.

[Means for solving problems]

In order to achieve the above object, in the method for forming a resist pattern undercut shape according to the present invention, a negative resist layer that is exposed to an ion beam is formed on a semiconductor substrate, and this resist layer is first exposed to the same pattern. The ion beam that passes through the resist layer is used to expose an area smaller than a predetermined pattern, and then the ion beam that remains on the surface of the resist layer is used to expose the resist layer according to the predetermined pattern.

[For production]

In the case of the method of this invention, first, an ion beam passing through the same resist layer is exposed to light within a range smaller than a predetermined pattern, the length of the eaves of the pattern is controlled by this first exposure, and then the same resist layer is The ion beam remaining on the surface layer of the substrate is exposed in accordance with a predetermined pattern, and the thickness t of the eaves portion of the pattern can be controlled by this second exposure.

〔Example〕

Hereinafter, one embodiment of the method for forming a resist pattern undercut shape according to the present invention will be described in detail with reference to FIG.

FIGS. 1(a) to 1(d) are sectional views showing the method of this embodiment in the order of steps.

That is, in the method of this embodiment, a negative resist layer 22 that is exposed by an ion beam is coated on the entire surface of a silicon semiconductor substrate 21 in advance to a thickness of, for example, about 1 μm, and then subjected to a capping process. In this state, the resist layer 22 is first formed as shown in FIG.
For example, as the first exposure for the same resist layer 2,
A focused ion beam 25 of 200 KeV Be transmitted through the resist pattern 2 is used to expose an area narrower by the length of the eaves than the resist pattern to be finally obtained, thereby forming a first exposed portion 23. ((b) in the same figure). Next, as a second exposure of the resist layer 22, for example, 100 KeV S is applied to the surface layer of the resist layer 22.
The i+ focused ion beam 2B wraps the area according to the resist pattern to be finally obtained on the first exposure part 23, so that the thickness tl at the eave part corresponds to, for example, about 2500A. The first and second exposed areas are formed by exposing to the depth to form a second exposed area 23 (FIG. 2(C)), and then developing it to remove the unexposed area. Only the portions corresponding to the exposed portions 23 and 24 are selectively left on the silicon semiconductor substrate 21 to obtain a resist pattern having a predetermined length and an eaves portion of thickness t, particularly by the second exposed portion 24. (
Figure (d)).

In this way, in this embodiment method, the eaves formed around the outer periphery of the front surface are precisely controlled and formed to a predetermined length and thickness t, as in the resist pattern shown in FIG. It can be done.

In the method of the above embodiment, a 200 KeV Be focused ion beam is used for the first exposure, but any combination of acceleration voltage and ion species may be used as long as the beam can transmit and expose the resist layer. Similarly, as the second exposure, 100 KeV
Although a focused Si ion beam of The order of the exposure operations may be arbitrary, and the semiconductor substrate is not limited to silicon.

〔Effect of the invention〕

As detailed above, according to the method of the present invention, a resist layer is exposed by an ion beam that transmits and exposes the resist layer within an area smaller than a predetermined pattern and while remaining on the surface layer of the resist layer. Since each ion beam was exposed in a predetermined pattern,
By performing these two exposure operations, it is possible to precisely control and shape the eaves formed around the outer periphery of the surface side of the resist pattern to a predetermined length and thickness t, and also to form the eaves to a predetermined length and thickness t. Since there is little proximity effect, resist patterns with extremely high precision can be easily formed with good reproducibility.

[Brief explanation of drawings]

FIGS. 1(a) to d) are cross-sectional views showing an example of the method for forming a resist pattern undercut shape according to the present invention in the order of steps, and FIGS. 2(a) to d) are the conventional methods as above. FIG. 3 is a cross-sectional view showing a preferred undercut shape of a general resist pattern. 21... Silicon semiconductor substrate, 22... Negative resist layer exposed by ion beam, 23...
...first exposure section, 24...second exposure section, 25.
...First focused ion beam, 26...Second focused ion beam agent Masuo Oiwa 1st cause (a> (C) Figure 2 (α) (b) (C) (d) Figure 3

Claims (2)

[Claims] (1) A step of forming a negative resist layer on a semiconductor substrate that is exposed to an ion beam; The resist pattern also includes at least the steps of: exposing the surface layer of the resist layer with an ion beam in a predetermined pattern; and developing and removing the unexposed portion of the resist layer. How to form an undercut shape. (2) The method for forming a resist pattern undercut shape according to claim 1, wherein the ion beam for exposure is a focused ion beam.