JPH04157721A - Plasma etching method - Google Patents

Abstract

PURPOSE:To remove an oxide film on the side face and to obtain an etched pattern whose selective ratio is high and whose uniformity is excellent by a method wherein the oxide film on a silicon-contained body is plasma-etched and removed by using a plasma gas composed of a fluorine compound which does not contain carbon and, after that, the silicon-contained body is etched by using a mixed gas of halogenated hydrogen with an inert gas. CONSTITUTION:A specimen to be etched is arranged; the inside of a reaction chamber 4 is evacuated by using a vacuum pump; a gas pressure is set to 1mTorr; after that, SF6 gas at 50scc/min is introduced through a gas introduction pipe 5; the distance between electrodes 2, 3 is set at 1.4 to 1.9cm; 200W is applied to a high-frequency power supply 6; the gas is changed to a plasma; an oxide film on polysilicon is removed by 20 to 50Angstrom in 5 to 10sec. Then, a mixed gas of HBr gas at 125scc/min with H2 gas at 100scc/min is introduced into the reaction chamber 4; a pressure is set at 250 to 350mTorr. The distance between the electrodes 2, 3 is set at 1.1cm; 250W is applied to the high-frequency power supply 6; the gas is changed to a plasma; polysilicon is etched. As a result, the oxide film can be removed and an etched pattern whose selective ratio is high and whose uniformity is good can be achieved when the polysilicon is etched.

Description

Detailed Description of the Invention (1) Industrial Application Field The present invention relates to a technique for obtaining highly selective plasma etching of a silicon-containing body, and in particular, it is capable of removing an oxide film on a silicon-containing body and This invention relates to a technique for obtaining plasma etching with high selectivity and excellent uniformity.

(2) Conventional Technology Etching apparatuses with various concepts have been announced as polysilicon etchers that have transitioned to 16M.

In particular, many new concept technologies such as ECR and magnetron RIE have been announced. At the same time, the performance amplifiers required for polysilicon etching are rapidly increasing. In particular, as the line width becomes narrower, it has become necessary to focus on achieving both oxide film selectivity and CD control (anisotropy). In addition, there are many etching processes for polysilicon and polycide on high-level differences.
The conventional two-step etching becomes difficult to use, and it is necessary to achieve anisotropy and high selectivity with a single-step etching.

The polysilicon enchers announced to date have achieved a moderate oxidation resistance film selectivity, and have achieved improved stringer capability, CD control, and shape change during 0/E (over etching). It has been a problem as a matter of fact. RIE with microwave assist
Etscher has extremely good stringer capability, but its shape tends to change when 0/E is performed.

HBr is a process developed to improve these problems.
This process achieved anisotropy and high selectivity in a single step by achieving an extremely high selectivity to oxide film.

Known techniques using HBr gas include the following.

US Pat. No. 4,490,209 describes the use of a mixed gas of 18r and a chlorine compound such as HcE or BCl3 as a silicon plasma gas.

Further, regarding tungsten plasma gas, US Pat. No. 4,849,067 describes the use of a gas containing at least SFb and HBr.

Furthermore, when both the selectivity to oxide film and anisotropic etching are achieved in a single step, etching residues due to the oxide film on the silicon-containing body become a problem.

The oxide film is uniformly attached to the surface of the polysilicon, and the polysilicon has a structure in which the upper and lower sides thereof are sandwiched with oxide films. Particularly in the case of polysilicon etching on high steps, the oxide film also adheres to vertical surfaces along the profile of the steps.

Removal of this oxide film is a big problem in an anisotropic process where the oxide film etch rate is about 20 people/sin.As for etching the polysilicon after removing the oxide film,
The following publicly known techniques are known.

JP-A-2-86126 discloses a polysilicon etching method in which an oxide film on polysilicon is etched with Freon and B.
, IJ, or ECR3 atmosphere, and then plasma etching of the polysilicon in an HBr atmosphere is disclosed.

The disadvantage of using chlorine compounds as a gas for oxide removal is that
Etching is performed under conditions where there is more ion bombardment than with fluorine, resulting in anisotropic etching, which makes it impossible to remove the oxide film at high step areas. In addition, the resist is easily etched, and carbon generated from the resist adheres to the surface of polysilicon, resulting in disadvantages such as non-uniform pattern shape when etching polysilicon. This causes a similar drawback when using fluorocarbon gas.

In order to solve the above-mentioned drawbacks and to effectively etch tungsten polycide, it is known that tungsten silicide is etched with SF6 and HBr gas, and polysilicon is etched with )lBr alone. (Semiconductor World)
rld) '90. k7. pages 80-84).

(3) The first problem to be solved by the invention is to remove the drawbacks of gases such as chlorine compounds mentioned above in removing the oxide film on the surface of polysilicon, and to remove the oxidation on the side surface of the object to be etched. The object of the present invention is to remove a film and obtain an etching pattern with a high selectivity and excellent uniformity when etching an object to be etched.

Second, even when etching a two-layer structure of high melting point metal silicide and polysilicon, the high melting point metal silicide and oxide film on top of the polysilicon can be removed, and the etching can be done uniformly with a high selectivity. The objective is to obtain an etching pattern with excellent properties.

(4) Means for solving the problem As a result of our intensive research to eliminate the various drawbacks of the above-mentioned conventional technology, we have found that "oxide film/silicon-containing breakdown layer/underlying oxide film/substrate" or "silicon-containing layer (silicide)" )/oxide film/silicon-containing layer/base oxide film/substrate. It has been found that the film should be removed by plasma etching using a plasma gas capable of removing it.

It has been found that when the outermost layer or intermediate layer oxide film is removed in this manner, etching of the remaining silicon-containing material can be carried out extremely smoothly and uniformly.

Therefore, in order to solve the above-mentioned problems, the present invention provides (i) a plasma etching method in which a base oxide film is formed on a substrate and a silicon-containing body deposited thereon is plasma-etched; The oxide film is removed by plasma etching using a plasma gas made of a fluorine compound that does not contain carbon, and then the silicon-containing body is etched with a mixed gas of hydrogen halide and an inert gas. Plasma etching method (11) In a plasma etching method in which an oxide film is formed on a substrate and polysilicon deposited thereon is plasma etched, the oxide film on the polysilicon is removed with a plasma gas containing at least SF. ,After this,[(
A plasma etching method characterized by etching polysilicon with a plasma gas of Br and He. In the plasma etching method, the tungsten silicide is etched with a plasma gas of a mixture of SF4.11Br and an inert gas, and then the polysilicon is etched with a plasma gas of IBr and He. An etching method is provided.

Here, the silicon-containing body is made of polysilicon, tungsten silicide, tantalum silicide, titanium silicide, or the like.

Plasma gases that can remove oxide films include carbon-free fluorine compound gases such as sp6 and SF, or
Fluorine compounds such as SFb and Sh that do not contain carbon, hydrogen halides such as HBr, He, and Ar.

There is a mixture of inert gases such as N2.

Plasma gases capable of plasma etching silicon-containing materials include hydrogen halides such as tlBr, Ar, N
6. There is a mixture of inert gases such as He.

(5) The working oxide film is removed by plasma etching with various plasma gases such as carbon-free fluorine compounds.

The silicon-containing body is etched by plasma etching with various plasma gases such as hydrogen halides and inert gases.

Conventionally, etching was performed according to the etching process shown in FIG. 1(a), but in the present invention, etching was performed according to the etching process shown in FIG.
and etched according to the etching process of (C). Here, the etching progresses from left to right, and eventually the oxide film is removed and the silicon-containing material is also etched, as shown in the figure on the far right. FIG. 1(C) shows a process in which two layers of silicon-containing bodies are deposited on a substrate;
After iv), polysilicon is etched using HBr+He gas.

Particularly by using an inert gas, a highly uniform etching pattern can be achieved.

(6) Examples Example 1 Parallel plate-shaped high frequency upper and lower electrodes 2 shown in FIG.
．． After forming an oxide film with a thickness of 8,000 wafers on the surface of a silicon substrate and buttering it, a sample to be etched with polysilicon deposited with a thickness of 4,000 wafers was placed in the reaction chamber 4 of a gas plasma etching apparatus having a After evacuating the reaction chamber 4 with a pump and setting the gas pressure to 1 mTorr,
SF gas is supplied through the gas introduction pipe 5 at 50 sec/sin.
was introduced, and the pressure was set at 300 to 40 θ-Torr. Then, the distance between the electrodes 2 and 3 is set to 1.4 to 1.8 cl, and the high frequency ti! [200W is applied to 6 to turn the gas into plasma, and 20 to 50 oxide films on polysilicon are
It was removed in 0 seconds. At this time, the temperatures of the upper and lower electrodes are each 40"C, and the temperature of the cooling chamber 7 under the lower electrode is
e The cooling pressure was 15 to 20 Torr.

In addition to the above gases, t (Br gas 1003cc/wi
n6, SF & gas 50scc/winXHe gas 100
A mixed gas of scc/sin can be used.

Next, HBr gas 125scc/win was introduced into the reaction chamber 4,
Introducing a mixed gas of He gas 100scc/+ein,
The pressure was 250-350 mTorr. Then, the distance between the electrodes 2 and 3 is set to 1.1C11, and the high frequency power source 6 is
W was applied to turn the gas into plasma to etch the polysilicon.

The temperature of the upper and lower electrodes at this time is 40 to 80, respectively.
°C, and the He cooling pressure in the cooling chamber 7 below the lower electrode was 10 to 20 Torr.

FIG. 3a shows an SEM photograph of polysilicon etched under these etching conditions. A resist was used as a mask at this time. Further, SEM photographs in the case of using a multilayer resist, a C resist, and an oxide film as masks are shown in FIGS. 3 and 3C. FIG. 4 shows an SEM photograph of polysilicon etched under these etching conditions.

The relationship between the pressure dependence of the polysilicon thickness and the pinching characteristics in this example is shown in FIG.
The etching rate of polysilicon at 50 layer Torr is
Approximately 4,500 people/sin or more, uniformity of ±3 to 5%, selectivity to oxide film of 90, and selectivity to resist of 20 to 30 were obtained.

Further, FIG. 8 shows the dependence of the He flow rate on the polysilicon etching characteristics in this example.

As a result, the oxide film was removed and an etching pattern with high selectivity and good uniformity was achieved in polysilicon etching.

Example 2 An oxide film with a thickness of 150 mm was formed on the surface of a silicon substrate in the reaction chamber 4 of the plasma etching apparatus shown in FIG. Tungsten silicide on the oxide film with a thickness of 20
After placing the sample to be etched and depositing 0.00 μm, the inside of the reaction chamber 4 was evacuated using a vacuum pump to bring the gas pressure to 1 mTorr, and then HBr gas was introduced at 50 scc/w through the gas introduction pipe 5.
in6,) He gas 100scc/+ein.

A mixed gas of SF and gas at 50 scc/win was introduced, and the pressure was set to 350+wTorr. Then, the distance between the electrodes 2.3 was set to 1.1 cm, and 250 W was applied to the high frequency power source 6 to turn the gas into plasma, thereby etching and removing the tungsten silicide and the oxide film thereunder. At this time, the He cooling pressure under the lower electrode was set to zero.

Next, 100 scc/sin of HBr gas was introduced into the reaction chamber 4,
Introducing a mixed gas of He gas 1ooscc/win,
The pressure was 350 Torr. Then, the distance between the electrodes 2.3 was set to 1.8 or 1.1 CIl, and 225 W was applied to the high frequency power source 6 to turn the gas into plasma to etch the polysilicon. At this time, the extreme temperatures of the upper and lower parts were each 40°C, and the He cooling pressure under the lower part was 2°Torr.

FIG. 5 shows an SEM photograph of tungsten silicide/polysilicon etched under these conditions. The etch rate of tungsten silicide at this time was 3000
person/sin, that of polysilicon is 3000 people/sin
, that of the oxide film was 80 people/sin.

A multilayer resist was used as a mask material at this time.

Also, SE of tungsten silicide when there is a step difference.
The M photograph is shown in FIG. 5, and the SEM photograph when the tungsten silicide is over-etched by 50% and 200% is shown in FIG. 6a.

Shown in b.

In Examples 1 and 2 above, SF was used as the gas for removing the oxide film.
was used, but Nh can be used in addition to this.

In addition to He, Ar and Nz gases can also be used as inert gases.

Furthermore, in addition to the above-mentioned tungsten silicide, it can also be applied to tantalum silicide, titanium silicide, etc.

■Effects According to the present invention, even when there is a high level difference in the base oxide film, it is possible to completely remove the level difference part, and therefore, it is possible to completely remove the oxide film, and to achieve high selectivity and anisotropic shape at the same time. Moreover, an etching pattern with excellent uniformity can be achieved.

[Brief explanation of drawings]

FIG. 1 (al represents the etching process according to the conventional method. FIG. 1 [present]) and (C) represent the etching process according to the method of the present invention. Here, A refers to a base oxide film, B refers to a silicon-containing material, C refers to an oxide film, and D refers to a silicon-containing material. FIG. 2 shows a plasma etching apparatus for performing plasma etching of the present invention. FIGS. 3(a), 3(c), and 3(c) are SEM photographs taken at 20,000 times, 48,000 times, and 20,000 times, respectively, after etching the polysilicon on the step. FIG. 4 is an SEM photograph of polysilicon after etching at a magnification of 24,000 times. FIG. 5 is an SEM photograph of the tungsten silicide on the step after etching at a magnification of 20,000 times. FIG. 6 (al and Φ) is a SEM photograph with a magnification of 24,000 times after tungsten silicide was overetched by 50% and 200%, respectively. FIG. 7 is a graph of HBr process/pressure dependence. FIG. 8 is a graph of He flow rate dependence. l Two substrates, 2: cathode, 3 near node,
4: Reaction chamber, 5: Gas introduction pipe, 6: High frequency power supply, 7: Cooling chamber,
8: Cooling water, 9: Shield, 1
o: Baffle plate, 11: Cooling water, 12: Switching means, 13: He gas inlet, 14: Clamp 7th Fj! J Pressure (mTorr) 8th gap 1008θ 60

Claims (1)

[Claims] 1. In a plasma etching method in which a base oxide film is formed on a substrate and a silicon-containing body deposited thereon is plasma-etched, the oxide film on the silicon-containing body is formed using a carbon-free fluorine compound. A plasma etching method characterized in that the silicon-containing body is removed by plasma etching using a plasma gas consisting of a silicon-containing material, and then the silicon-containing body is etched with a mixed gas of hydrogen halide and an inert gas. 2. The method of claim 1, wherein the silicon-containing material is selected from the group consisting of polysilicon, tungsten silicide, tantalum silicide, or titanium silicide. 3. The fluorine compound is SF_6, NF_3,
The method according to claim 1. 4. The method according to claim 1, wherein the etching gas for removing the oxide film further contains hydrogen halide and an inert gas. 5. The method according to claim 4, wherein the hydrogen halide is HBr. 6. The method according to claim 4, wherein the inert gas is He. 7. The method according to claim 1, wherein the hydrogen halide is HBr. 8. The method according to claim 7, wherein the inert gas is He. 9. In a plasma etching method in which an oxide film is formed on a substrate and polysilicon deposited thereon is plasma etched, the oxide film on the polysilicon is removed with a plasma gas containing at least SF_6, and then HBr and A plasma etching method characterized by etching polysilicon with He plasma gas. 10. The etching gas for removing the oxide film further contains H
10. The method according to claim 9, comprising a mixed gas containing Br and He. 11. In a plasma etching method that forms an oxide film on a substrate and plasma-etches a double layer consisting of tungsten silicide and polysilicon deposited on the oxide film, the tungsten silicide is etched with a plasma of a mixed gas of SF_6, HBr, and an inert gas. A plasma etching method characterized in that polysilicon is etched with a gas, and then polysilicon is etched with a plasma gas of HBr and He.