JP3067576B2 - Plasma etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention performs cleaning by gas plasma containing fluorine, cleaning after alone gas or chlorine gas (Cl ₂₎ and oxygen gas of chlorine gas (Cl ₂₎
In a plasma etching apparatus for etching silicon, polycrystalline silicon, and silicide using a mixed gas of (O ₂ ) as an etching gas, the change in etching rate of silicon after cleaning and an oxide film (SiO ₂ ) as a base film is measured. The present invention relates to a plasma etching method suitable for suppressing and improving uniformity between wafers.

[0002]

2. Description of the Related Art Conventionally, in a plasma process including etching, cleaning is performed to prevent particle contamination of a wafer, and post-cleaning is performed to eliminate residues in a processing chamber after cleaning. When SF ₆ or NF ₃ gas is used for cleaning, N ₂ , Ar, O ₂ gas plasma is used for post-cleaning. Examples of this type of technology include, for example, Literature: Yutaka Hiratsuka, Cleaning Design
P41-53,1992.Summer.

[0003]

In the conventional etching apparatus, the effect of the residue in the processing chamber on the etching characteristics after cleaning is not considered. There is a problem that the speed decreases and the remaining film of the base oxide film fluctuates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma etching method capable of suppressing a decrease in the etching rate of silicon and an oxide film after cleaning, preventing a change in a remaining film of a base oxide film, and obtaining good uniformity between wafers. To provide.

[0005]

The above object can be achieved by performing seasoning with a plasma of a mixed gas of Cl ₂ gas and SiCl ₄ gas after cleaning to reduce the influence of residues in the processing chamber for cleaning.

[0006]

FIG. 1 shows the change in the emission spectrum of SiF according to the number of processed wafers when silicon is etched with Cl ₂ gas plasma after cleaning with SF ₆ gas plasma. SiF produced by the reaction between silicon and fluorine
The intensity of the emission spectrum decreases with the number of processed wafers and becomes almost constant. From this, it was found that fluorine remained in the processing chamber after cleaning with a gas containing fluorine. Next, FIGS. 2 and 3 show the emission spectrum of SiF and the change in the etching rate of the silicon and oxide films when SF ₆ gas is added to Cl ₂ gas. SF ₆ as shown in Figure 2
The intensity of the emission spectrum of SiF increases with an increase in the amount of added Si. Further, as shown in FIG. 3, the etching rate of the silicon and oxide films increases with the increase in the amount of SF ₆ added. From this, it has been found that the etching rate of the silicon and the oxide film decreases as the residual fluorine decreases. Therefore, after cleaning, seasoning is performed with a mixed gas plasma of Cl ₂ and SiCl ₄ to remove residual fluorine, and when the time change of the intensity of the emission spectrum of SiF becomes a certain value or less, the seasoning ends and etching starts. This can suppress fluctuations in the etching rate of the silicon and oxide films.

[0007]

FIG. 4 shows an embodiment of the present invention. FIG. 4 shows a schematic diagram of a microwave plasma etching apparatus. In FIG. 4, magnetron 1
The microwave oscillated from the
Through the processing chamber 4. Processing room 4 is bell jar 3,
It is composed of a mounting electrode 5 and a ground electrode 6. A cleaning gas (SF ₆ ) and a seasoning gas (Cl ₂ , SiCl ₄ ) supplied from an etching gas supply device 9 by a magnetic field formed by a DC current supplied from a magnetic field generating DC power supply 7 to a solenoid coil 8 and a microwave electric field. ) And the etching gas (chlorine gas (Cl ₂ )) are turned into plasma. The processing chamber 4 is cleaned by the SF ₆ gas plasma. C
seasoning the processing chamber 4 is carried out by a mixed gas plasma of l ₂ and SiCl _4. At the time of cleaning and seasoning, a quartz substrate is mounted on the mounting electrode 5. After cleaning and seasoning, the substrate 10 mounted on the mounting electrode 5 is etched by Cl ₂ gas plasma. The pressure at the time of cleaning, seasoning, and etching is controlled by the evacuation device 11. The energy of ions incident on the substrate 10 is controlled by the high-frequency power supplied from the high-frequency power supply 12 to the mounting electrode 5. FIG. 5 and FIG. 6 show the difference in the change in the etching rate of the silicon and oxide films depending on the presence or absence of seasoning. Seasoning is
Carried out by a mixed gas plasma of Cl ₂ and SiCl _4, stops seasoning when the emission intensity ratio becomes 1 ± 0.002 of spectra measured emission spectra of SiF the monitored time tn and time tn-1 every 10 seconds did. By performing the seasoning after the cleaning, the influence of the residual fluorine generated during the cleaning can be suppressed, and the fluctuation of the etching rate can be prevented.

According to this embodiment, the effect of residual fluorine after cleaning can be suppressed, and the etching rate of silicon and an oxide film can be prevented.

In this embodiment, the effects of the microwave plasma etching apparatus have been described. However, the same effects can be obtained in other discharge systems such as an inductively coupled discharge system and an internal energy supply discharge system.

[0010]

According to the present invention, the influence of residual fluorine after cleaning can be suppressed, and the etching rate of silicon and an oxide film can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the dependence of the SiF emission intensity on the number of processed wafers.

FIG. 2 is an explanatory diagram showing the dependence of the emission intensity of SiF on the amount of SF ₆ added.

FIG. 3 is an explanatory diagram showing the dependency of the etching rate of Si and SiO ₂ on the addition amount of SF ₆ .

FIG. 4 is a configuration diagram of a microwave plasma etching apparatus showing one embodiment of the present invention.

FIG. 5 is a view for explaining an effect of one embodiment of the present invention;
FIG. 4 is an explanatory diagram showing the dependence of the O ₂ etching rate on the number of processed wafers.

FIG. 6 is a view for explaining an effect of one embodiment of the present invention;
FIG. 4 is an explanatory diagram showing the dependence of the etching rate on the number of processed wafers.

[Explanation of symbols]

3… bell jar, 6… earth electrode, 7… solenoid coil, 9… substrate.

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065

Claims (3)

(57) [Claims] 1. A Clean the gas plasma containing fluorine, a mixed gas of cleaning after chlorine gas alone gas or chlorine gas (Cl ₂₎ (Cl ₂₎ and oxygen gas (O ₂₎ as an etching gas, the gas In a plasma etching apparatus that etches silicon, polycrystalline silicon and silicide at a pressure of 20 mTorr or less, after cleaning,
A plasma etching method characterized in that etching is started after performing discharge (hereinafter, referred to as seasoning) by using plasma of a mixed gas of Cl ₂ gas and SiCl ₄ gas. 2. The fluorine-containing gas according to claim 1, wherein the gas comprises sulfur hexafluoride (SF ₆ ), nitrogen trifluoride (NF ₃ ), xenon difluoride (XeF ₂ ), fluorine (F ₂ ), A plasma etching method, which is a single gas or a mixed gas of chlorine trifluoride (ClF ₃ ). 3. The cleaning and the seasoning according to claim 1, wherein the cleaning and the seasoning are continuously performed using a substrate having a silicon oxide film (SiO ₂ ) formed thereon or a quartz substrate. Characteristic plasma etching method.