JP3158993B2 - Plasma etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method, and more particularly to a plasma etching method suitable for etching silicon, polycrystalline silicon or silicide.

[0002]

2. Description of the Related Art Conventionally, Yutaka Hiratsuka, "Chamber Cleaning of Dry Process Equipment", Cleaning Design 1992. Sum
As described in Mer, P41-53, in a plasma process such as etching, cleaning is performed to prevent particle contamination of a wafer, and post cleaning is performed to eliminate residues in the processing chamber after cleaning. When SF ₆ and NF ₃ gases are used for cleaning, N ₂ , Ar, H ₂ and O ₂ gas plasmas are used for post-cleaning.

[0003]

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

An object of the present invention is to provide a silicon, polycrystalline silicon
Of wafers with silicon or silicide film to be processed
In grayed, a plasma et <br/> etching process uniformity is achieved between the wafer to prevent fluctuation of the remaining film to suppress the decrease of the etching rate of the silicon after processing chamber cleaning and oxide film underlying oxide film Is to do.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to contain fluorine.
Cleaning of the processing chamber by gas plasma
After the cleaning, there is a single gas of chlorine gas (Cl2).
Or a mixed gas of chlorine gas (Cl2) and oxygen gas (O2)
Into a plasma as an etching gas,
High frequency power is applied to the mounting electrode of the substrate to be processed independently of
To control the incident energy of ions on the substrate to be processed
Silicon, polycrystalline silicon or silicide
When etching the substrate to be treated as the
After the polishing, the silicon (Si) substrate is
To the same etching gas plasma as the etching process.
And then replace the dummy substrate with Si
Substrate or stone with oxide film (SiO2) formed on substrate
The high-frequency power is marked on the mounting electrode using the English substrate as a dummy substrate.
Plasma treatment with Cl2 gas without adding
Thereafter, this is achieved by starting the etching process of the substrate to be processed . In addition, the above purpose is to
The inside of the processing chamber is cleaned by plasma.
After polishing, chlorine gas (Cl2) alone gas or chlorine
Etching mixed gas of gas (Cl2) and oxygen gas (O2)
Into a plasma as a gas, independent of the generation of the plasma
Apply high-frequency power to the mounting electrode of the substrate to be processed
Controls the incident energy of ions on the substrate,
Processing using crystalline silicon or silicide as a processing film
When cleaning the substrate, after cleaning,
Substrate with oxide film (SiO2) formed on the surface of silicon
Is a mixture of Cl2 and SiCl4 using a quartz substrate as a dummy substrate
A break-in discharge by gas plasma is performed, and
Substrate or stone with oxide film (SiO2) formed on its surface
The high-frequency power is marked on the mounting electrode using the English substrate as a dummy substrate.
Plasma treatment with Cl2 gas without adding
Then, by starting the etching process of the substrate to be processed,
Is achieved.

[0006]

First, after cleaning, the discharge (seasoning) is performed by using the etching gas Cl ₂ or a mixed gas plasma of Cl ₂ and O ₂ to reduce the influence of residual fluorine in the processing chamber after cleaning. Then, by performing Cl ₂ plasma treatment with Cl ₂ gas plasma after the break-in discharge, the influence of reaction products of silicon in the processing chamber after the break-in discharge can be reduced, and the etching of silicon and oxide films after cleaning can be performed. It is possible to obtain a good uniformity between wafers by suppressing a decrease in the speed and preventing a change in the remaining film of the base oxide film.

[0007]

First, FIG. 4 shows a change in the emission spectrum of SiF (wavelength: 441 nm) according to the number of processed wafers when cleaning is performed with SF ₆ gas plasma and then silicon is etched with Cl ₂ gas plasma. The intensity of the emission spectrum of SiF generated by the reaction between silicon and fluorine decreases with the number of processed wafers and becomes substantially constant. From this, it was found that fluorine remained in the processing chamber after cleaning with a gas containing fluorine. FIG. 5 and FIG. 6 show the case where SF ₆ gas is added to Cl ₂ gas.
5 shows a change in the emission spectrum of iF and the etching rate of silicon and an oxide film. As shown in FIGS. 5 and 6, the intensity of the emission spectrum of SiF (wavelength 441 nm) increases as the amount of SF ₆ added increases. As the addition amount of SF ₆ increases, the etching rate of the silicon and oxide films increases. From this fact, it has been found that the etching rate of the silicon and the oxide film fluctuates due to the residual fluorine, and the etching rate of the silicon and the oxide film decreases as the residual fluorine decreases.

The above-described etching of silicon by Cl ₂ gas plasma corresponds to break-in discharge after cleaning, that is, seasoning. After the seasoning, a silicon-based reaction product (Si or SiCl
It was found from the emission spectrum of Si that x) remained. FIG. 7 shows a change in the etching rate of the oxide film when the SiCl ₄ gas is added to the Cl ₂ gas. The etching rate of the oxide film decreases as the added amount of SiCl ₄ increases. It has been found that the etching rate of the silicon oxide film immediately after seasoning is reduced due to the silicon-based reaction product.

According to the above, seasoning is performed after cleaning with plasma containing fluorine, and by removing fluorine remaining in the processing chamber after cleaning, fluctuations in the etching rates of silicon and oxide films can be suppressed. Later, a plasma treatment using Cl ₂ gas, that is, a Cl ₂ discharge is performed to remove a reaction product of silicon remaining in the treatment chamber after seasoning, and thus it is possible to suppress a change in an etching rate of an oxide film. Was.

An embodiment of the present invention will now be described with reference to FIGS.
This will be described below. FIG. 3 is a diagram schematically showing a microwave plasma etching apparatus which is an example of a plasma processing apparatus for performing the method of the present invention. Magnetron 1
The microwave oscillated from the laser beam propagates through the waveguide 2 and is guided to the processing chamber 4 via the discharge tube 3 made of quartz. A cleaning gas (SF ₆ ) and a seasoning gas (Cl ₂ gas) supplied from the etching gas supply device 8 by a magnetic field formed by a DC current supplied to the solenoid coils 6 and 7 from the magnetic field generating DC power supply 5 and a microwave electric field. ), Cl ₂ discharge gas (Cl ₂ ) and etching gas (Cl ₂ gas)
Each step is turned into plasma.

First, the processing chamber 4 is treated with SF ₆ gas plasma.
Cleaning is performed. Thereafter, seasoning of the processing chamber 4 is performed by Cl ₂ gas plasma using the silicon substrate. Further, Cl ₂ discharge is performed using a silicon substrate or a quartz substrate having an oxide film formed on the silicon surface. After cleaning, seasoning and Cl ₂ discharge, C
The wafer 10 mounted on the mounting electrode 9 by l ₂ gas
Is etched. The pressure during cleaning, seasoning, Cl ₂ discharge, and etching is controlled by the evacuation unit 11. The energy of ions incident on the wafer is controlled by high-frequency power supplied from the high-frequency power supply 12 to the mounting electrode 9.

FIGS. 1 and 2 show the difference in the change in the etching rate of the silicon and oxide films between the case without seasoning and the case with seasoning and Cl ₂ discharge. Seasoning was performed using Cl ₂ gas plasma, and the emission spectrum of SiF was monitored every 10 seconds, and the emission intensity ratio of the spectrum measured between time t (n) and time t (n−1) became 1 ± 0.002. At this point, seasoning was stopped. 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. Cl ₂ discharges Cl ₂ without applying a high-frequency power
The reaction product of silicon is removed by gas plasma. The emission spectrum of Si is monitored every 10 seconds and the time t
The Cl ₂ discharge was stopped when the emission intensity ratio of the spectrum measured between (n) and time t (n−1) became 1 ± 0.002.
By performing the Cl ₂ discharge after the seasoning, the influence of the residual silicon reaction product generated during the seasoning can be suppressed, and the fluctuation of the etching rate of the base oxide film can be prevented.

According to this embodiment, it is possible to suppress the influence of the residual fluorine after cleaning and to prevent the fluctuation of the etching rate of the silicon and oxide films. In addition, it is possible to suppress the influence of the reaction product of silicon after seasoning and prevent a change in the etching rate of the base oxide film.

In this embodiment, the effect of the microwave plasma etching apparatus has been described. However, other discharge methods such as plasma etching (PE), helicon, TCP
(Transformer Coupled Plasma) can provide the same effect.

[0015]

According to the present invention, there is an effect that the influence of the residual fluorine after cleaning and the reaction product of silicon after seasoning can be suppressed, and fluctuations in the etching rates of silicon and oxide films can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing the dependence of the etching rate on the number of processed SiO ₂ wafers in one embodiment of the present invention.

FIG. 2 is a diagram showing the dependence of the Si etching rate on the number of processed wafers in one embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a microwave plasma etching apparatus showing an example of an apparatus for performing the method of the present invention.

FIG. 4 is a diagram illustrating the dependence of the SiF emission intensity on the number of processed wafers.

FIG. 5 is a graph showing the dependence of the emission intensity of SiF on the amount of SF ₆ added.

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

FIG. 7 is a diagram showing the dependency of the SiO ₂ etching rate on the amount of added SiCl ₄ .

[Explanation of symbols]

3. Quartz discharge tube, 6, 7 solenoid coil, 8 etching gas supply device, 10 wafer.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuo Yamazaki 5-2-1, Kamimizuhonmachi, Kodaira-shi, Tokyo Semiconductor Company, Hitachi, Ltd. (56) References JP-A-7-201814 (JP, A) JP-A-4-87329 (JP, A) JP-A-6-295882 (JP, A) JP-A-1-298180 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00 H01L 21/304 645

Claims (8)

(57) [Claims] 1. A processing chamber using a fluorine-containing gas plasma.
Perform cleaning, plasma post the cleaning, the mixed gas alone gas or chlorine gas in chlorine gas (Cl2) (Cl2) and oxygen gas (O2) as the etching gas
And independently of the generation of the plasma,
Applying high-frequency power to the poles to transfer ions to the substrate
Controls incident energy and etches substrate to be processed using silicon, polycrystalline silicon or silicide
In processing, after said cleaning, silicon (S
i) the substrate and the dummy substrate, was discharged conditioned by plasma of the same <br/> etching gas and the etching process, the following
The dummy substrate was replaced with an oxide film (Si) on the Si substrate.
O2) formed substrate or quartz substrate is used as dummy substrate
And without applying the high-frequency power to the placement electrode,
Plasma treatment with l2 gas is performed, and then the
A plasma etching method characterized by starting an etching process for a processing substrate . 2. The plasma etching method according to claim 1 , wherein the same pattern as that of the substrate to be processed is formed after the cleaning, the conditioning discharge, and the plasma processing using the gas plasma containing fluorine before starting the etching. Plasma etching method for dummy-etching the etched silicon substrate and oxide film substrate one by one. 3. The plasma etching method according to claim 2 ,
Oite, wherein the processing time with the silicon substrate definitive dummy etching the just etching time of the substrate to be processed in the etching process, the oxide film processing time with substrate prior <br/> in the etching process A plasma etching method in which the substrate to be processed is over-etched. 4. The plasma etching method according to claim 1, wherein
The gas containing fluorine is sulfur hexafluoride (SF
6), nitrogen trifluoride (NF3), xenon difluoride (Xe
A plasma etching method using a single gas or a mixed gas of F2), fluorine (F2) and chlorine trifluoride (ClF3). 5. The plasma etching method according to claim 1, wherein
Oite, the conditioned discharge plasma etching method ends when the time change in the intensity of monitoring the emission spectrum of SiF light emitting spectrum is below a predetermined value. 6. The plasma etching method according to claim 1, wherein said plasma processing is performed by monitoring an emission spectrum of Si and ending when a temporal change in the intensity of the emission spectrum becomes a predetermined value or less. 7. The plasma etching method of claim 1, wherein, the plasma etching method of the temperature of the temperature or the processing chamber of the etching process at the start of the discharge tube and 100 ° C. or higher. 8. A process chamber is cleaned by a gas plasma containing fluorine, and after the cleaning, a plasma of a single gas of chlorine gas (Cl2) or a mixed gas of chlorine gas (Cl2) and oxygen gas (O2) is used as an etching gas. Independently of the generation of the plasma, high-frequency power is applied to the mounting electrode of the substrate to be processed to control the incident energy of ions on the substrate to be processed, and silicon, polycrystalline silicon or silicide is converted to the film to be processed. When the substrate to be processed is etched, after cleaning, a substrate having an oxide film (SiO2) formed on the silicon surface or a quartz substrate is used as a dummy substrate, and a break-in discharge is performed by plasma of a mixed gas of Cl2 and SiCl4. A substrate having an oxide film (SiO2) formed on a silicon surface or a quartz substrate is used as a dummy substrate, A plasma process using a Cl2 gas without applying the high-frequency power to the substrate, and then starting an etching process on the substrate to be processed.