JPH07263408A - Plasma etching method - Google Patents

Abstract

PURPOSE:To avoid the fluctuation in the residual underneath film for assuring an excellent wafer-to-wafer uniformity by a method wherein the etching step is to be started after cleaning and seasoning steps using HCl, BCl3 gas plasma as well as preetching step using an etching gas plasma. CONSTITUTION:A cleaning gas (SF6), a seasoning gas (BCl3) and an etching gas (Cl2 gas) fed from a feeder 8 by a magnetic field and microwave electric field formed by DC fed from a magnetic field generating DC current 5 to solenoid coils 6, 7 are to be made plasmatic. Next, a preprocessing chamber 4 is cleaned up using cleaning gas (SF6) plasma while the seasoning and preetching steps of the processing chamber are performed using the seasoning gas (BCl3 gas plasma) and the etching gas plasma (Cl2). At this time, a wafer 10 mounted on a mounting electrode 9 is etched away using the etching gas (Cl2). Through these procedures, the effect of residual fluorine after the cleaning step is averted thereby enabling the fluctuation in the etching rate of Si and an oxide film to be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cleaning with a gas plasma containing fluorine, and in particular to silicon after cleaning and an oxide film (SiO 2) which is a base film.
_{The present} invention relates to a plasma etching method suitable for suppressing the change in the etching rate of ₂ ) and improving the 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 remove a residue in a processing chamber after cleaning. When SF ₆ and NF ₃ gases are used for cleaning, N ₂ , Ar, H ₂ and O
₂ Gas plasma is used for post cleaning.

Note that, as a technique related to the present technology, for example, reference: Yutaka Hiratsuka, Cleaning Design P41-53, 199.
2. Summer is mentioned.

[0004]

In the conventional etching method, the influence of the residue in the processing chamber after cleaning on the etching characteristics is not taken into consideration. There is a problem that the speed decreases and the residual film of the underlying oxide film fluctuates.

An object of the present invention is to provide an etching method capable of obtaining a good wafer-to-wafer uniformity by suppressing a decrease in the etching rate of silicon and an oxide film after cleaning, preventing a fluctuation of a residual film of an underlying oxide film. is there.

[0006]

In order to solve the above-mentioned problems, after cleaning, seasoning with HCl, BCl ₃ gas plasma and pre-etching with etching gas Cl ₂ or Cl ₂ and O ₂ mixed gas plasma are performed. It is intended to reduce the influence of residues in the processing chamber after cleaning.

[0007]

FIG. 1 shows the change in the emission spectrum of SiF (wavelength 441 nm) depending on the number of processed wafers when the silicon is etched by Cl ₂ gas plasma after cleaning by SF ₆ gas plasma. The intensity of the emission spectrum of SiF produced by the reaction of silicon and fluorine decreases with the number of processed wafers and becomes almost constant. From this, it was found that after cleaning with a gas containing fluorine, fluorine remained in the processing chamber. 2 and 3
FIG. 4 shows changes in the emission spectrum of SiF and the etching rate of silicon and an oxide film when SF ₆ gas is added to Cl ₂ gas. As shown in FIGS. 2 and 3, the etching rate of silicon and the oxide film increases as the amount of SF ₆ added increases. Also, as the amount of SF ₆ added increases, SiF
The intensity of the emission spectrum (wavelength 441 nm) increases. From this, it was found that the etching rates of the silicon and the oxide film fluctuate due to the residual fluorine, and the etching rates of the silicon and the oxide film decrease as the residual fluorine decreases. Therefore, after cleaning, to remove residual fluorine, seasoning with HCl and BCl ₃ gas plasma is performed, and when the time change of the intensity of the emission spectrum of SiF becomes a certain value or less, the seasoning is finished,
After seasoning, the etching gas is Cl ₂ or C
Pre-etching is performed with a mixed gas plasma of l ₂ and O ₂ .
By starting the etching after the seasoning and pre-etching, fluctuations in the etching rate of the silicon and the oxide film can be suppressed. Further, as shown in FIG. 4, H or B containing B, which has a larger binding energy with F than Cl.
It was found that the removal time of residual fluorine can be shortened by using Cl and BCl ₃ gas plasma.

[0008]

EXAMPLE An example of the present invention will be described with reference to FIG. FIG. 5 shows a schematic diagram of a microwave plasma etching apparatus. In FIG. 5, the microwave oscillated from the magnetron 1 propagates through the waveguide 2 and is guided to the processing chamber 4 through the microwave introduction window 3. DC power supply for magnetic field generation 5
The cleaning gas (S) supplied from the etching gas supply device 8 by the magnetic field and the microwave electric field formed by the direct current supplied to the solenoid coils 6, 7 from
F ₆ ), seasoning gas (BCl ₃ ) and etching gas (Cl ₂ gas) are turned into plasma. The processing chamber 4 is cleaned by SF ₆ gas plasma. Processing room 4
The seasoning and pre-etching are performed by BCl ₃ gas plasma and Cl ₂ gas plasma. The wafer 10 mounted on the mounting electrode 9 is etched by the Cl ₂ gas. The pressure during cleaning and etching is controlled by the vacuum exhaust device 11. The energy of the ions incident on the wafer is controlled by the high frequency power supplied from the high frequency power supply 12 to the mounting electrode 9. 6 and 7 show the difference in the change in the etching rate of silicon and the oxide film depending on the presence or absence of seasoning. The seasoning and pre-etching are performed by BCl ₃ gas plasma and Cl ₂ gas plasma, and the emission spectrum of SiF is monitored every 10 seconds, and the emission intensity ratio of the spectrum measured at time tn and time tn- ₁ becomes 1 ± 0.002. The seasoning was stopped when it became. By performing the seasoning after the cleaning, it is possible to suppress the influence of the residual fluorine generated during the cleaning and prevent the fluctuation of the etching rate.

According to this embodiment, it is possible to suppress the influence of residual fluorine after cleaning and prevent fluctuations in the etching rate of silicon and oxide films.

Although the effect of the microwave plasma etching apparatus has been described in the present embodiment, the same applies to other discharge methods such as reactive ion etching (RIE), plasma mode etching (PE), magnetron RIE, helicon, and TCP. Can be obtained.

[0011]

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

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing dependency of SiF emission intensity on SF ₆ addition amount.

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

FIG. 4 is an explanatory diagram showing processing time dependence of SiF emission intensity.

FIG. 5 is a configuration diagram of a microwave plasma etching apparatus.

FIG. 6 is an S diagram for explaining an effect in one embodiment of the present invention.
iO ₂ is an explanatory diagram showing processing number dependency of the etching rate.

FIG. 7 is an S diagram for explaining an effect in one embodiment of the present invention.
It is explanatory drawing which shows the number of processed i of etching rate.

[Explanation of symbols]

2 ... Waveguide, 3 ... Microwave introduction window, 4 ... Processing chamber, 6 ...
Solenoid coil.

Claims (3)

[Claims] 1. Cleaning is performed with a gas plasma containing fluorine, and after cleaning, etching of silicon, polycrystalline silicon, or silicide is performed by using a single gas of chlorine gas or a mixed gas of chlorine gas and oxygen gas as an etching gas. In the etching apparatus, after the cleaning, seasoning by plasma of hydrogen chloride gas, boron trifluoride gas alone or mixed gas of at least two kinds of hydrogen chloride gas, boron trifluoride gas, chlorine gas and plasma of etching gas A plasma etching method characterized by starting etching after performing pre-etching. 2. The gas containing fluorine is a single gas or a mixed gas of sulfur hexafluoride, nitrogen trifluoride, xenon difluoride, fluorine and chlorine trifluoride. Plasma etching method. 3. The plasma according to claim 1, wherein the emission spectrum of SiF is monitored during the seasoning, and the seasoning is terminated and etching is started when the time change of the intensity of the emission spectrum becomes a certain value or less. Etching method.