JPS60137022A - Etching method - Google Patents

Abstract

PURPOSE:To eliminate trouble of a defective pattern shape, the formation of pin hole, etc. by improving the ashing rate of a polymethyl methacrylate group resist. CONSTITUTION:Patterns such as wiring patterns 2 in aluminum are formed on a wafer 1, and a PSG layer 3 is applied in approximately 1mum thickness. A polymethyl methacrylate (PMMA) layer 4 is applied in approximately 1-1.5mum thickness, and patterned. A PMMA group resist is treated with chlorine group plasma, and the PMMA layer 4 is etched by Freon group plasma. An ashing rate to Freon group plasma of the PMMA group resist is lowered largely through treatment by chlorine group plasma. Accordingly, the excess ashing of the resist is prevented, and troubles such as the defective shape of a material to be etched, the generation of a pin hole, etc. are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an etching method, particularly an etching method using Freon plasma as a polymethyl methacrylate (PMMA) type resist mask. As part of the microfabrication technology accompanying the increase in the degree of integration of devices, exposure with a resist electron beam has become commonplace. PMMA is a typical resist for electron beam exposure that was developed early on, and its high resolution is particularly attractive.

However, since the ratio of the etch rate to the material to be etched in dry etching is small, there are problems such as defective etching shapes and generation of pinholes. This will be explained with reference to FIGS. 1 and 2. For example, after forming 2 aluminum wiring patterns on wafer 1, PSG
Layer 3 is covered to a thickness of about 1 μm.

Next, a PMMA layer 4 is applied to a thickness of about 1.0 to 1.5 μm, and patterned as shown in PMMAN 4y in order to form a window in PSGN 3 for forming a through hole, for example. It is assumed that the width of the opening in the PMMA layer 4 for opening the window is Wl. After this, if selective etching of PSG%3 is performed using, for example, Freon-based plasma 7, p MM
Since the ashing rate of A + a 4 is fast, the PMMA layer 4 is ashed together with the PSG layer 3 exposed under the opening of the PM MA depression. Particularly in the vicinity of the opening, as shown by the broken line in Figure 2,
CPMllvJ, the A layer 4 is laterally ashed, and as a result, the width W8 of the opening in the PMMA layer increases, and finally the P
When the SG layer 3 is etched to form a window, the width of the window becomes W2 (larger than W'1 as shown in the figure), and a defect occurs in the etched pattern shape.

In addition, since the PMMA layer 4 is not necessarily coated to a uniform thickness, parts with insufficient thickness may be etched during the etching process.
j M M A layer has turned into ashes, and the PSG underneath it has
There is a risk that layer 3 will also be etched and bin holes will be formed there.

Purpose of the Invention The present invention, in view of the problems of the prior art as described above,
In the plasma etching process using MMA thread as a resist mask, it is possible to improve the ashing rate of the PMMA resist and eliminate inconveniences such as the formation of poor pattern shapes and poles. The eyes become pale.

Structure of the invention In order to achieve the above object, the present invention provides a PMM
After patterning the A-type resist, the resist is first treated with chlorine-based plasma and then etched with Freon-based plasma. By this treatment with chlorine-based plasma, the ashing rate of I) MMA-based resist due to Freon-based plasma is significantly reduced. The present invention has been devised to discover these four fruits.

In addition to PMMA having the following formula:), the PMMA resist referred to in the present invention includes PMMA having the following formula: 1. ,7S:
It refers to a stout body like this. Furthermore, these three polymers (P(
MMA-MA)) +CP (MMA-CIlPvlA
)), and combinations thereof. In addition, chlorine-based plasma and 'D, B HnCJ8-4-Hs CHyl
CJ! 4-B1. + S 1 Hl Ce4-1
(n11ntlj, o1112, or 3.)
, CG2 gas, etc., in which zero plasma exists. Freon plasma is Freon gas, such as CF.
Embodiment of the Invention FIG. 3 shows a square plate type etching apparatus.

High frequency power can be supplied from a power source 8 to the electrode plates 6,7 in the etching chamber 5, and a wafer 9 to be processed is placed on the electrode plate 10,000. The etching chamber 5 is hermetically sealed.
t, while evacuating from the gas outlet 10, the scum population 11
From the valve 12 - [The plasma gas is of equal size.

Using such a device, we conducted the following experiments.
A PMMA resist film was formed. This wafer was placed on a parallel plate plasma etching apparatus shown in Fig. 3 and etched with 5Bα, 200SCCM, (c converted to standard condition).
Waterfall in nt/minute unit) 10CCJ410S
Cc M gas mixture is supplied, and the degree of vacuum (>, 1 To
rr s frequency 13.56 M) lz high frequency with power 0.
Plasma treatment was performed for 5 minutes under conditions of approximately 1 W/c11t. The film thickness of PHMA after this plasma treatment was approximately 0.8 to 1.0 μm.

Next, the supply gas YCf (F'38
0SCCM+0□ Change to 3~58CCM, vacuum degree 0.
2 Torr, high frequency power 13.56 M■1z, 0
．． Plasma treatment was performed at a rate of 4 W/crtl. After measuring the film thickness after treatment and calculating the ashing rate, we found that
It was about 50 to 100 A/min.

Conventionally, PMMA was directly converted without chlorine plasma treatment.
The rate of ash 1 to M is about 300 to 50 OA/min7.
According to this C1 chlorine plasma treatment,
The ashing rate of 'l MA is significantly reduced by VC. Incidentally, since the enol-l- of pSG by the above Freon plasma treatment is 800 to 900 A/min, PM
The MA resist achieves an etch rate ratio of about 10 times. Also, 'SiO□.

The etch rate of SiN3 is about 500 A/min and 250 A/min.

Example 2 PMMA resist film (thickness 145μ?+1) formed as in Example 1 L5BCig3+CQ? 5ick4200~300SCCM instead of 4 mixed gas, +(
Using mixed gas V of '7280SCCH, vacuum degree 0.1
Torrx high frequency power 13.56MHz, 1W
Plasma treatment was performed for 10 to 30 seconds under the conditions of /rr&, leaving a 10 μm thick film. When this was subjected to Freon plasma treatment under the same conditions as in Example 1, the etch rate was 50 to 100 A/min.

Example 3 P M M A (P(MMA-MA)) and C
Two copolymers of P(MMA-CiMA)) were polymerized by dehydrochlorination reaction. CrosslinkedM
ethavilate Re5ist (CMR) l
: Similar results were obtained when using

Example 4 Similar effects have been confirmed in Freon plasma etching using CF and +eHF3'Y in addition to tiCHF3. For example, the etching conditions are CC
Into the flow rate of F41005CC, CCHF31O0SCC, vacuum degree 0.2 Torr Rf 13.56 MHz
Under the condition that the power density is about 1 W/crt1,
The ashing rate of the resist is about 800A/Jl1m without chlorine plasma treatment, but with the above treatment
I try to keep it to around 00A/Nll+.

Referring to FIG. 1, an aluminum wiring pattern (thickness: 1.0 μm) 2) is formed on a silicon wafer 1, and a PSG layer is coated thereon to a thickness of 1 μm. Then P.M.
It was coated to a thickness of 1.5 μm using the MAi liquid spin-off method.

A window with a width of 2 μm is formed above the aluminum wiring layer 2 of this PMMA Ifi4.

Then, as in Example 1, B C/, + C' (
Perform plasma treatment using J4 mixed gas for approximately 5 minutes.

The PMMA layer has a thickness of about 1.0 μm. Next, Example 1
In the same manner as above, plasma etching is performed using a mixed gas of CHF3+0□ for about 15 minutes. As a result, as shown in FIG. 4, through-hole windows with a width of about 2.3 μm are formed in the 280 layer 3.

Effects of the Invention As is clear from the above explanation, the present invention produces a PMMA-based resist that is an electron beam resist with a high resolution of 7! Even in plasma etching performed as a mask, it is possible to reduce resist ash [hypertonia] and remove inconveniences such as poor shape of the object to be etched and generation of pinholes.

[Brief explanation of drawings]

No. 11￥1 is a cross-sectional view of the object to be processed before etching treatment, FIG. 2 is a cross-sectional view of the object to be processed after etching treatment in the conventional technology, FIG. 3 is a conceptual diagram of the etching apparatus, and FIG. 4 is the present invention. FIG. 3 is a cross-sectional view of the object to be processed after etching according to FIG. 3...PSCI! , 4...PMMAf
&, 5...Etching room, 6,7...
Electrode, 8... Power supply, 9... Wa
)1゜

Claims (1)

[Claims] It is characterized by including the step of applying a polymethyl methacrylate resist on a substrate, patterning it, treating the resist with chlorine plasma, and then selectively etching the substrate with Freon plasma using the resist as a mask. Etching method.