JPH06302565A - Plasma cleaning method for chamber - Google Patents

Abstract

PURPOSE:To clean a chamber without releasing vacuum by using plasma of gas containing at least hydrogen or at least hydroxyl group when the chamber is cleaned after dry etching. CONSTITUTION:Cleaning using plasma of mixed gas of methane (CH4) and N2 is conducted. First, chlorine content included in a deposit in a chamber 1 is reacted with hydrogen radical or ion generated from the CH4 in the cleaning gas plasma to become hydrochloride (HCl) to be removed. Methyl (CH3) group generated in the plasma is reacted with aluminum in the deposit in the chamber 1 to become trimethyl aluminum (Al(CH3)3), etc. Since the trimethyl aluminum has a vapor pressure of 157mmHg at 80 deg.C, it can be easily vaporized in a vacuum chamber and removed from the chamber 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing apparatus cleaning method, and more particularly to a plasma cleaning method for a chamber after dry etching of a metal thin film.

[0002]

2. Description of the Related Art In the process of forming electrode wiring of a semiconductor device, various metal thin films are selectively etched. However, during this etching, it is inevitable that a part of the reaction product of the etching gas and the material to be etched adheres to the inside of the chamber. When the amount of the deposits increases, it becomes a factor of instability of the atmosphere in the chamber, which causes deterioration of etching reproducibility. Further, it also causes a decrease in cleanliness in the chamber, which causes particles to be generated during etching, and eventually leads to defective etching. Conventionally, in order to remove deposits in this chamber, cleaning using plasma of oxygen (O ₂ ) gas or cleaning using plasma of gas containing fluorine (F) such as nitrogen trifluoride (NF ₃ ). Has been done. In addition, a dry cleaning method using a mixed gas of NF ₃ and H ₂ O as a cleaning gas (JP-A-2-94522), a dry cleaning method using a mixed gas of NF ₃ or SF ₆ and H ₂ as a cleaning gas (special Kaihei 2-304923) and the like are also proposed.

However, the cleaning using the plasma of oxygen (O ₂ ) gas can only remove the organic substances such as the photoresist sputtered during the etching which are redeposited in the chamber. Further, cleaning using a plasma of a gas containing fluorine such as nitrogen trifluoride (NF ₃ ) can only remove deposits made of silicon (Si) or the like that easily react with fluorine radicals and vaporize. Further, the method of using a mixed gas of NF ₃ and H ₂ O as a cleaning gas can only remove the redeposited organic substance in the chamber and the adhered substance such as silicon (Si). The method of using a mixed gas of NF ₃ or SF ₆ and H ₂ as a cleaning gas is for removing the residual bromine content that has adhered and accumulated in the chamber. However, in etching a metal thin film using a chlorine-based or bromine-based gas, a reaction product containing a metal and chlorine or bromine often adheres to the inside of the chamber.
This deposit is difficult to remove by conventional cleaning using plasma of oxygen (O ₂ ) gas or plasma of gas containing fluorine such as nitrogen trifluoride (NF ₃ ).
On the other hand, when the deposits in the chamber cannot be completely removed by the cleaning using these plasmas, the deposits are removed by breaking the vacuum of the chamber and cleaning. Therefore, in chamber cleaning after etching a metal thin film using a chlorine-based or bromine-based gas, it is essential to break the vacuum of the chamber and perform cleaning.

[0004]

As described above, in the conventional chamber cleaning method after dry etching using plasma, when the metal thin film is etched using chlorine or bromine gas, the inside of the chamber is It was difficult to remove the reaction product containing the adhered metal and chlorine or bromine. This causes problems that the reproducibility of etching is deteriorated and that etching is defective due to generation of particles during etching. Then, the vacuum of the chamber is broken and cleaned. (1) It is necessary to return the chamber to the vacuum again and perform dummy discharge for a certain period of time to eliminate the influence of residual air. It takes a very long time to restart, (2) It takes a long time for cleaning work,
(3) Since the gas used for etching is a highly reactive poisonous gas, there is a problem in that it is dangerous for the safety of the operator.

The present invention has been made in consideration of the above circumstances, and an object thereof is to remove reaction products adhering to the inside of a chamber after dry etching of a metal thin film using a chlorine-based or bromine-based gas. It is an object of the present invention to provide a plasma cleaning method that can be efficiently performed and can be cleaned without breaking the vacuum of the chamber.

[0006]

In order to achieve this object, the present invention uses the following means. That is, in the plasma cleaning method of the chamber according to the present invention, in the method of cleaning the chamber after dry etching of a metal thin film using a chlorine-based or bromine-based gas, plasma of gas containing at least hydrogen is used, Alternatively, plasma of a gas containing at least a hydroxyl group is used.

[0007]

According to the present invention, the reaction product deposited in the chamber after dry etching of a metal thin film using a chlorine-based or bromine-based gas by the above method uses plasma of an organic compound gas containing at least hydrogen. If it is present, chlorine or bromine in the attached reaction product is removed by combining with hydrogen, and the metal forms a compound with a high vapor pressure with the above-mentioned organic compound from which hydrogen has been desorbed. Therefore, the attached reaction product can be easily removed by an ordinary plasma cleaning method.

When plasma of a gas containing at least a hydroxyl group is used, the metal in the attached reaction product becomes a metal alkoxide compound, for example, when the gas containing a hydroxyl group is alcohol. Since the similar compound is removed, the attached reaction product can be easily removed by a usual plasma cleaning method.

As described above, the reaction products attached to the chamber can be efficiently removed. As described above, in the chamber plasma cleaning method of the present invention, it is possible to efficiently remove the reaction product attached in the chamber after dry etching of a metal thin film using a chlorine-based or bromine-based gas, Cleaning can be performed without breaking the vacuum of the chamber.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) This embodiment embodies the invention of claim 1 of the present invention.

FIG. 1 is a schematic block diagram of an RIE (reactive ion etching) device used in the embodiment of the present invention. Figure 1
In the chamber (vacuum processing chamber) 1, a gas introduction port 2 and an exhaust port 3 are provided. A sample mounting electrode (cathode) 4 is arranged in the chamber 1, and a counter electrode (anode) 5 is attached to the upper end of the chamber 1 so as to face the sample mounting electrode 4. High frequency power is applied to the sample mounting electrode 4 from a high frequency power source 6 through a matching circuit 7, and the counter electrode 5 is grounded. The sample mounting electrode 4 is cooled by the cooling mechanism 8. Then, the sample 9 to be etched is placed on the sample placing electrode 4.

FIG. 2 shows a sectional view of the sample used in the embodiment of the present invention. Here, in the sample, a silicon dioxide (SiO ₂ ) film 11 is formed as an insulating oxide film on a silicon substrate 10, and an aluminum-silicon-copper alloy film (Al-Si-) having a film thickness of 0.8 μm is formed thereon. Cu film) 12 is formed by the sputtering method. Further, a mask pattern 13 of photoresist is formed thereon by a known photolithography technique.

Using the mask pattern 13 as an etching mask for this sample, using the above-mentioned RIE apparatus,
Etching is performed using a mixed gas of SiCl ₄ , Cl ₂ , CHCl ₃ and N ₂ . The etching pressure is 20 Pa, and the high frequency power density at a frequency of 13.56 MHz is 1 W / cm ² . The substances adhering to the inside of the chamber after etching include reaction products of Al and chlorine, reaction products of Si and chlorine, sputter decomposition products of resist, and a mixture of these. is there.

Here, cleaning of the chamber with plasma of NF ₃ gas and cleaning of the chamber with plasma of O ₂ gas are performed, and then methane (CH
₄ ) Clean the chamber using plasma of a mixed gas of N ₂ and N ₂ . Here, at the time of cleaning using plasma of a mixed gas of methane (CH ₄ ) and N ₂ , the temperature of the inner wall of the chamber is maintained at 60 ° C. or higher.

Here, by cleaning the chamber with the plasma of NF ₃ gas, it is possible to remove the deposit mainly made of silicon (Si) or the like that easily reacts with the fluorine radicals and is easily vaporized. In the cleaning using the plasma of O ₂ gas, it is possible to mainly remove the organic substances such as photoresist sputtered during the etching that are re-deposited in the chamber.

In the cleaning using the plasma of a mixed gas of methane (CH ₄ ) and N ₂ , the chlorine component contained in the deposit in the chamber was generated from CH ₄ in the cleaning gas plasma. It reacts with hydrogen radicals or ions to become hydrogen chloride (HCl) and is removed. Then, the methyl (CH ₃ ) group generated in the plasma reacts with aluminum in the deposit in the chamber to become trimethylaluminum (Al (CH ₃ ) ₃ ) and the like, and this trimethylaluminum has a vapor pressure of 80 ° C. 157
Since it is in mmHg, it can be easily vaporized in a vacuum chamber and can be removed from the chamber. Here, the N ₂ gas serves to stabilize the formation of trimethylaluminum while facilitating the formation of a methyl group in plasma.

In this way, the reaction products adhering to the inside of the chamber can be efficiently removed after the etching of the aluminum alloy using the chlorine-based gas. Then, after this cleaning, when the Al-Si-Cu alloy is etched again by reactive ion etching (RIE) using a mixed gas of SiCl ₄ , Cl ₂ , CHCl ₃ and N ₂ , the initial state before the cleaning process is performed. Compared to
Etching rate, etching shape, mask (resist)
There is no change in etching characteristics such as the selection ratio with respect to the base and the base.

During the cleaning in this embodiment, as a plasma of a gas of an organic compound containing hydrogen, C
A plasma of a mixed gas of H ₄ and N ₂ was used, but instead,
Ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ), butane (C ₄
H _10), ethylene (C ₂ H _4), propylene (C ₃ H _6),
Plasma of gas of butylene (C ₄ H ₈ ) or acetone (CH ₃ COCH ₃ ) or plasma of mixed gas combining these gases, or gas containing fluorine (F) and oxygen (O ₂ ) And nitrogen (N ₂ ) each of which is a single gas, or a plasma of a gas to which a mixed gas of a combination thereof is added can be used. Further, an inert gas such as Ar or He may be added to these and used. Further, instead of NF ₃ used in this example, S
It is also possible to use plasma of a gas containing fluorine such as F ₆ , CF ₄ , ClF ₃ or the like. Further, the case where the cleaning using the plasma of the gas containing fluorine and the cleaning using the plasma of the O ₂ gas are described separately, but the cleaning is performed using the plasma of the mixed gas of the gas containing the fluorine and the O ₂ gas. May be performed. Similarly, it is possible to apply various cleaning gases shown in this embodiment by selecting an appropriate gas at the time of cleaning processing and transforming the combination of gas and processing into the optimum one. And
The cleaning effect can be enhanced by setting the temperature of the inner wall of the chamber at the time of cleaning to be appropriate.

Further, in this embodiment, a mixed gas of SiCl ₄ , Cl ₂ , CHCl ₃ and N ₂ is used as the etching gas, but in addition to this, chlorine-based gas such as BCl ₃ or HCl, BBr ₃ , The present invention can also be applied when using a bromine-based gas such as HBr or Br ₂ as an etching gas. Further, in this embodiment, an Al-Si-Cu alloy film is selected as the metal to be etched, but other aluminum (Al), silicon (Si), titanium (T
The same effect can be obtained when dry etching a metal film such as i), molybdenum (Mo) or the like, an alloy film containing these metals, or a laminated film made of them is used as a chlorine-based or bromine-based gas as an etching gas.

As the etching and cleaning method, magnetron RIE or ECR etching may be used instead of RIE.

(Second Embodiment) This embodiment embodies the invention of claim 2 of the present invention.

The RIE (reactive ion etching) device used in this embodiment is the same as the RIE device used in the first embodiment. FIG. 1 shows the RIE used in this example.
The schematic block diagram of an apparatus is shown. The sample used in this example is the same as the sample used in the first example. Figure 2
The sectional view of the sample used in the example of the present invention is shown in FIG. here,
In the sample, a silicon dioxide (SiO ₂ ) film 2 is formed as an insulating oxide film on a silicon substrate 1, and a film thickness of 0.1 is formed on the silicon dioxide (SiO ₂ ) film 2.
8 μm aluminum-silicon-copper alloy film (Al-S
An i-Cu film) 3 is formed by the sputtering method. Further, a mask pattern 4 of photoresist is formed thereon by a known photolithography technique.

The same etching as in the first embodiment is performed on this sample. That is, using the above RIE device,
Using the mask pattern 13 as an etching mask, SiC
Etching is performed using a mixed gas of l ₄ , Cl ₂ , CHCl ₃ and N ₂ . Etching pressure is 20 Pa, frequency 1
The high frequency power density at 3.56 MHz is 1 W / cm ² . The substances adhering to the inside of the chamber after etching include reaction products of Al and chlorine, reaction products of Si and chlorine, sputter decomposition products of resist, and a mixture of these. is there.

Where NF₃Gas plasma plasma
Clean the chamber and then use isopropyl
Alcohol (i-C₃H₇OH) and O₂Mixed gas plasm
Use a marker to clean the chamber. Where i
Sopropyl alcohol (i-C ₃H₇OH) and O₂A mixed moth
Of the chamber during cleaning with plasma
The temperature of the inner wall is maintained at 100 ° C or higher.

Here, by cleaning the chamber with the plasma of NF ₃ gas, it is possible to remove the deposit mainly made of silicon (Si) or the like which easily reacts with the fluorine radicals and is easily vaporized.

Then, isopropyl alcohol (i-C ₃
In cleaning using plasma of a mixed gas of (H ₇ OH) and O ₂ , first, the chlorine component contained in the deposit in the chamber is changed to i-C ₃ H ₇ O in the cleaning gas plasma.
HC by reacting with hydrogen radicals or ions generated from H
It becomes 1 and is removed. Then, the alkoxyl group (i-OC ₃ H ₇ ) generated in the plasma reacts with aluminum in the deposit in the chamber to form triisopropoxyaluminum (Al (i-OC ₃ H ₇ ) ₃ ). Isopropoxy aluminum has a vapor pressure of 8.3 mm at 132 ° C.
Due to the presence of Hg, it can be easily vaporized in the vacuum chamber and removed from the chamber. The oxygen component (O) in the plasma can mainly remove the organic substance such as the photoresist sputtered during the etching and redeposited in the chamber.

In this way, it is possible to efficiently remove the reaction products adhering to the inside of the chamber after etching the aluminum alloy using the chlorine-based gas. Then, after this cleaning, when the Al-Si-Cu alloy is etched again by reactive ion etching (RIE) using a mixed gas of SiCl ₄ , Cl ₂ , CHCl ₃ and N ₂ , the initial state before the cleaning process is performed. Compared to
Etching rate, etching shape, mask (resist)
There is no change in etching characteristics such as the selection ratio with respect to the base and the base.

In the cleaning of this embodiment, i-C ₃ H ₇ OH was used as plasma of a gas containing a hydroxyl group.
A mixed gas plasma of O and O ₂ was used, but instead of this, methanol (CH ₃ OH), ethanol (C ₂ H ₅ OH),
Butyl alcohol (C ₄ H ₉ OH), a plasma of any gas, or a plasma of a mixed gas in which these gases are combined, or a gas containing fluorine (F) in each gas and oxygen (O ₂ ) and nitrogen (N It is possible to use the plasma of a gas obtained by adding the individual gases of ₂ ) or a mixed gas combining them. Further, an inert gas such as Ar or He may be added to these and used. Further, instead of NF ₃ used in this example, SF ₆ , CF ₄ , Cl
It is also possible to use plasma of a gas containing fluorine such as F ₃ . Further, the case where the cleaning using the plasma of the gas containing fluorine and the cleaning using the plasma of the O ₂ gas are explained separately, but the gas containing the fluorine and the O ₂ gas are explained.
Cleaning may be performed using plasma of a mixed gas with a gas. Similarly, it is possible to apply various cleaning gases shown in this embodiment by selecting an appropriate gas at the time of cleaning processing and transforming the combination of gas and processing into the optimum one. And by making the temperature of the inner wall of the chamber at the time of cleaning appropriate,
The cleaning effect can be enhanced.

In this embodiment, a mixed gas of SiCl ₄ , Cl ₂ , CHCl ₃ and N ₂ is used as the etching gas, but other than this, chlorine-based gas such as BCl ₃ or HCl, BBr ₃ , The present invention can also be applied when using a bromine-based gas such as HBr or Br ₂ as an etching gas. Further, in the present embodiment, an Al-Si-Cu alloy film is selected as the etching target, but other aluminum (Al), silicon (Si), titanium (Ti),
The same effect can be obtained when dry etching a metal film such as molybdenum (Mo), an alloy film containing these metals, or a laminated film made of them using chlorine or bromine gas as an etching gas.

Further, as the etching and cleaning method, magnetron RIE or ECR etching may be used in addition to RIE.

[0032]

According to the present invention, in a method of cleaning a chamber after dry etching a metal thin film using a chlorine-based or bromine-based gas, plasma of an organic compound gas containing at least hydrogen is used, or That is, plasma of a gas containing at least a hydroxyl group is used. As a result, the reaction products adhering to the inside of the chamber can be efficiently removed after dry etching of the metal thin film using a chlorine-based or bromine-based gas, and cleaning can be performed without breaking the chamber vacuum.

Therefore, the reproducibility of dry etching of a metal thin film using a chlorine-based or bromine-based gas is improved, and the generation of particles during etching can be suppressed to reduce the etching defect rate. These have a great effect in further increasing the integration of the LSI. Further, since the cleaning can be performed without breaking the vacuum of the chamber, there is an effect that the operating rate of the etching apparatus is improved, and the worker is prevented from coming into contact with a highly toxic chemical substance, so that safety can be improved. The effect is also large.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an RIE (reactive ion etching) device used in an embodiment of the present invention.

FIG. 2 is a sectional view of a sample used in an example of the present invention.

[Explanation of symbols]

1 chamber (vacuum reaction chamber) 2 gas inlet 3 exhaust port 4 sample mounting electrode (cathode) 5 counter electrode (anode) 6 high frequency power supply 7 matching circuit 8 cooling mechanism 9 sample to be etched 10 silicon substrate 11 silicon dioxide (SiO ₂ ) Film 12 Aluminum-silicon-copper alloy film (Al-Si
-Cu film) 13 mask pattern

Claims (6)

[Claims] 1. A plasma cleaning method for a chamber, characterized in that plasma of a gas of an organic compound containing at least hydrogen is used in a method of cleaning the chamber after dry etching a metal thin film using a chlorine-based or bromine-based gas. . 2. A plasma cleaning method for a chamber, wherein plasma of a gas containing at least a hydroxyl group is used in a method of cleaning the chamber after dry etching a metal thin film using a chlorine-based or bromine-based gas. 3. The plasma of the gas of an organic compound containing hydrogen according to claim 1, wherein the plasma of methane (CH ₄ ) or ethane (C
₂ H _6), propane (C ₃ H _8), butane (C ₄ H _10), ethylene (C ₂ H _4), propylene (C ₃ H _6), butylene (C ₄ H _8), acetone (CH ₃ COCH ₃ ) Plasma of any gas of ₃ ) or plasma of a mixed gas combining these, or a gas containing fluorine (F) in each gas, and each single gas of oxygen (O ₂ ) and nitrogen (N ₂ ) or those A plasma cleaning method for a chamber, wherein the plasma is a gas obtained by adding a mixed gas obtained by combining the above. 4. The plasma of the gas containing a hydroxyl group according to claim 2 is methanol (CH ₃ OH), ethanol (C ₂ H ₅
OH), isopropyl alcohol _{(i-C 3 H 7 OH} ),
Plasma of any gas of butyl alcohol (C ₄ H ₉ OH) or plasma of a mixed gas of these gases, or a gas containing fluorine (F) and oxygen (O ₂ ) and nitrogen ( A plasma cleaning method for a chamber, characterized in that the plasma is a plasma obtained by adding a single gas of N ₂ ) or a mixed gas of a combination thereof. 5. A plasma cleaning method for a chamber, wherein the metal thin film according to claim 1 is an aluminum metal thin film or a thin film of an alloy containing aluminum. 6. The gas containing fluorine (F) according to claim 3 or 4, wherein nitrogen trifluoride (NF ₃ ) gas, carbon tetrafluoride (CF ₄ ) gas or sulfur hexafluoride (SF ₆ ) gas is used. Alternatively, there is provided a chamber plasma cleaning method characterized by using chlorine trifluoride (ClF ₃ ) gas.