JPH01152285A - Production of semiconductor device - Google Patents

Abstract

PURPOSE:To improve etching characteristics by adding a specified percentage of one or more among gaseous fluorocarbon, sulfur hexafluoride and oxygen to gaseous fluorobromocarbon as principal gas and by etching silicon with the resulting gas. CONSTITUTION:The cathode 102 is placed opposite to the anode 101, a gas introducing inlet 105 and a gas sucking outlet 106 are formed and silicon is etched with gas prepd. by adding <25% one or more among gaseous fluorocarbon, sulfur hexafluoride and oxygen to fluorobromocarbon as principal gas. Since the added gas removes a produced carbon-based polymer and prevents the occurrence of etching residue, etching characteristics such as etching speed and anisotropy are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a silicon etching gas.

[Conventional technology]

Conventional silicon etching gases are fluorobromocarbon gases such as CB r P and c*nrtFa, and etching is carried out under the conditions shown in Table 1, for example. The etching method used at this time was reactive ion etching (RIE) having the structure shown in Table 1 as shown in FIG.

[Problem that the invention seeks to solve]

However, in the conventional technology described above, fluorobromocarbon gas reacts with Sl in a plasma state to form SiF (Si+F"→5iF), and etching progresses, but at the same time, carbon-based polymer is generated. It is well known that polymers have high etching resistance, and as the etching area of silicon in particular increases, the amount of etching increases.
Figure 7 (a), (b)? As shown in e, the etching shape becomes tapered and the amount of carbon-based polymer (405) generated changes depending on the density of the pattern, resulting in non-uniform etching shape and non-uniform etching rate. However, if the generation of carbon-based polymer is significant, the portion that should originally be etched will be masked by the carbon-based polymer, resulting in an etching residual odor.

These in-plane non-uniformities in pattern shape and pattern dimensions have become a major problem as processing dimensions have decreased.

Therefore, the present invention aims to solve these problems.
The purpose of this method is to control the etching shape, control the pattern size and shape by controlling the density of the pattern, and provide etching without an etching residual smell.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention uses fluorobromocarbon as a main gas, and uses fluorocarbon, sulfur hexafluoride, or oxygen alone or in combination as an additive gas in less than 25% of the main gas. It is characterized by etching silicon.

[Effect]

When etching silicon with fluorobromocarbon, the generated carbon-based polymer can be removed with fluorocarbon, sulfur hexafluoride, or oxygen plasma. A similar effect can be achieved while etching progresses when fluorocarbon, sulfur hexafluoride, or oxygen is mixed as an additive gas in fluorobromocarbon.

In particular, fluorocarbon and sulfur hexafluoride have the effect of etching silicon, and can further improve the etching properties.

〔Example〕

The present invention will now be described in detail based on examples.

The IT diagram shows the structure of the etching apparatus used in the first embodiment of the present invention, which processes the object to be etched on the cand ffi electrode (102), and generally uses reactive ion etching (hereinafter abbreviated as RIE). It is a device called.

Furthermore, FIG. 2 shows the structure of the etching apparatus used in the second embodiment of the present invention, and shows the gas introduction part (105) of the RIE apparatus.
) to grow a microwave generator, plasma minute 1ili
This is a device called type RIE.

Furthermore, FIG. 3 shows the structure of the etching apparatus used in the third embodiment of the present invention, in which gas introduced into the etching chamber is dissociated by microwaves carried by a waveguide (107), and etching is performed. Magnets placed around the room (10
This is a device called an electron or cyclotron type RIE (hereinafter abbreviated as ECR) that causes resonance by 8).

Figure 4 shows the cross-sectional structure of etching sample black 1 used in this example, showing a thermal oxide film (401) on a silicon substrate (401).
02) and polycrystalline silicon film (403), respectively.
There are 0 people and 4000λ, and patterning is performed using photoresist (404) as a mask material.

Figure 5 shows the etching sample Na2 used in this example.
In the cross-sectional structure, a pattern is formed on a silicon substrate (401) using a photoresist (404) as a mask material.

The first example is in RIE.

Here, C* B r s F a 50 s c
cm 1. :CF a5secm was mixed and used as a process gas. With this gas, the vacuum level is 10mtorr1
The RF power was 160W. As a result, the characteristics shown in Table 2 were obtained.

Table 2 As for the etching shape, a completely anisotropic pattern perpendicular to the mask was obtained.

Further, the etching characteristics when etching was performed under the conditions shown in Table 1 are as shown in Table 3, and each item was greatly improved.

Table 3 The second example is based on plasma separation type RIE. Here, CBrF, 50 sec and Oy5se
cm is mixed as a process gas, and the vacuum degree is 5mtOrr.
The microwave power was 100W and the RF power was 160W.

As a result, the characteristics shown in Table 4 were obtained.

Table 4 The etched shape at this time was a completely anisotropic pattern perpendicular to the mask.

The third embodiment is based on ECR. Here C
BrF540sccms 0.2sccm1SFs 2
sccm is mixed and used as a process gas, and the vacuum degree is 5 mto.
rr, microwave power 10QW1RF power 90W
Etching was carried out as follows.

As a result, the characteristics shown in Table 5 were obtained.

Table 5 The etching shape at this time was a completely anisotropic pattern perpendicular to the mask.

As described above, compared to etching using only fluorobromocarbon, the generation of carbon-based polymer can be suppressed, so the etching speed can be improved by 20 to 50%, and the etching shape and size variations can be stabilized.

However, as shown in Figure 8, although it depends on other etching conditions, if the mixing ratio of 70 carbon and sulfur hexafluoride as additive gas exceeds 20%, the etching shape becomes reverse taper. , if it exceeds 25%, it will have a serious adverse effect on the characteristics of the device.

In this embodiment, three types of RIE have been described, but other types of RIE have similar effects, and there is no difference depending on the type of etching, but the effect is due to the etching gas. In other words, the present invention is characterized by the etching gas rather than the etching device.

Further, in this embodiment, polycrystalline silicon and single crystal silicon are used as the silicon of the etching filter medium, but the same effect can be obtained regardless of the type and concentration of these impurities. The same applies to amorphous silicon.

Further, although photon cyst is used as the mask material in this embodiment, any material may be used as long as it has a selectivity to Si, such as an oxide film or a silicon nitride film.

〔Effect of the invention〕

As described above, according to the present invention, by etching with a mixture of fluorocarbon, sulfur hexafluoride, or oxygen, the etching rate is 10 to 50% compared to the conventional etching rate, and the selectivity to the oxide film is 0 to 50%. Improved by 20%.

Furthermore, the etched shape was completely anisotropic, no change due to pattern density was observed, and dimensional reproducibility was achieved within ±3%.

[Brief explanation of the drawing]

FIGS. 1 to 3 are diagrams showing the structure of the etching apparatus used in this example. 4 and 5 are cross-sectional views showing the structure of the etching sample used in this example. FIGS. 6(a) and 6(b) are diagrams showing the etching shapes of the present embodiment. Figures 7(a) and 7(b) are diagrams of etching shapes obtained by conventional etching. FIG. 8 is a graph showing the ratio of added gas and the etching taper angle in this example. 100...Etching chamber 101...Anode electrode 102...Cathode electrode 103-13.56MHz RF generator 104...2
．． 45 GHz microwave generator 105... Gas inlet 106... Gas outlet 107... Waveguide 108... Magnet 109... Quartz plate 401... Silicon substrate 402... Thermal oxidation Film 403...Polycrystalline silicon film 404...Photoresist mask 405...Carbon polymer 406...Etching residue or more Applicant: Seiko Epson Corporation tt Agent: Patent attorney Tsutomu Mogami and 1 other person 31 Rei 4 Tomoe No. 913 Virtue 4 B No. '711

Claims (1)

[Claims] With fluoropromocarbon as the main gas, two of the main gases
A method for manufacturing a semiconductor device, comprising etching silicon with a gas containing less than 5% of fluorocarbon, sulfur hexafluoride, or oxygen, alone or in combination, as an additive gas.