JPH11186226A - Plasma cleaning method in plasma processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove the remaining deposit film on the inner wall of a plasma processor by providing cleaning steps including cleaning with an O gas plasma and cleaning with a mixed gas plasma of Cl and BCl3 . SOLUTION: A microwave etcher introduces a plasma generating gas after evacuating into a high vacuum, oscillates a microwave 10 which is fed into a quartz bell-jar 3 through a waveguide 11 to ionize a gas in a process chamber through a solenoid coil 12, and etches by utilizing this plasma 14. In a series of plasma cleaning steps, a cleaning step with an O gas plasma and cleaning step with a mixed gas plasma of Cl and BCl3 . The O gas plasma is applied to a chloride, it is substituted in O and Cl, thus gasifying Cl. The deposit can be easily removed by removal of Cl molecules.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry cleaning method in a processing chamber of a semiconductor manufacturing apparatus such as a film forming apparatus such as CVD or an etching apparatus in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In the manufacturing process of a semiconductor device, if dust (foreign matter) adheres to a substrate, pattern defects of a target device are caused, and the yield in the manufacturing process is reduced. On the other hand, in microfabrication in recent manufacturing processes,
A dry etching process using plasma has become important. That is, various gases are introduced into the semiconductor manufacturing apparatus, and etching is performed by utilizing the reaction of the plasma of the introduced gases. In such a process, products generated by the etching adhere as deposited films everywhere on the inner wall of the semiconductor manufacturing apparatus. That is, in dry etching, the etching gas is decomposed or combined in the plasma, and a deposited film adheres to the inner wall of the device due to an etching by-product generated by the etching. When the number of processed films increases and the film thickness increases, such a deposited film partially peels off and becomes dust.

[0003] Therefore, it is necessary to periodically remove these deposits.

Conventionally, as a method of removing such deposits, a semiconductor manufacturing apparatus is opened to the atmosphere and wiped with a solvent such as alcohol or pure water, that is, wet cleaning, and cleaning using a cleaning plasma. Plasma cleaning is known. An example of the plasma cleaning method is disclosed in JP-T-7-508313.

[0005]

However, the above-mentioned conventional cleaning method has the following problems.

First, regarding wet cleaning,
Since it is necessary to open the semiconductor manufacturing apparatus to the atmosphere and disassemble it, vacuum evacuation after wet cleaning is required. Therefore, the semiconductor manufacturing apparatus is stopped for a long time for each cleaning, which causes a remarkable reduction in the apparatus operation rate and a reduction in throughput.

As a method for improving the disadvantages of the wet cleaning, a plasma cleaning method using plasma without opening the processing chamber to the atmosphere is known, as shown in Japanese Patent Publication No. Hei 7-508313.

[0008] Plasma cleaning is performed by removing a deposit to be removed by reacting with the deposit to form a compound having a high vapor pressure, and consequently evaporating and evacuating the deposit. For example, if the deposit is a carbon compound, it is made to react with the plasma of O2 gas to remove it into gaseous CO and CO2 and to remove it. Residual deposits in dry etching equipment are complex mixtures consisting of a series of multi-metal layers that are continuously etched, organic materials based on photoresist as a mask material, and polymers of etching gas. Whether cleaning can be performed by selecting the plasma determines whether the residual deposited film can be removed. In Japanese Patent Publication No. Hei 7-508313, cleaning is performed by converting a mixed gas containing oxygen gas and chlorine gas into plasma, and cleaning is performed by removing organic substances with oxygen gas plasma and removing metal compounds with chlorine gas plasma. It aims to improve.

However, according to the analysis of the inventor of the present invention, when an aluminum alloy or a laminated film of a metal containing an aluminum alloy is etched with a mixed gas of boron trichloride and chlorine, the deposited film remaining on the inner wall of the apparatus is not removed. , A mixture of aluminum alloy and boron chloride. Aluminum alloys are the most common and widely used as metal wiring, and a mixed gas of boron trichloride and chlorine is most commonly and frequently used for etching the same. The above-mentioned conventional example is considered to be effective for cleaning residual deposited films composed of a mixture of an organic substance and a metal, but is considered to be less effective for such a mixture of a chloride and a metal. .

An object of the present invention is to provide a plasma cleaning method which is effective as an aluminum alloy etching apparatus which is most commonly used as a metal wiring of a semiconductor element and is often used.

[0011]

The above object can be attained by carrying out plasma cleaning including at least cleaning with oxygen gas plasma and cleaning with plasma of a mixed gas of chlorine and boron trichloride. You.

Further, it is preferable that the cleaning by the oxygen gas plasma is performed before the cleaning by the plasma of the mixed gas of chlorine and boron trichloride.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma cleaning method of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a processing chamber of a microwave etching apparatus used in the dry cleaning method according to the present invention. FIG. 2 is a schematic diagram showing the composition of the deposited film remaining in the processing chamber, and FIG. 3 is a schematic diagram showing a state in which the residual deposited film is being removed.

In FIG. 1, reference numeral 1 denotes a silicon wafer (substrate) to be subjected to fine processing, and reference numerals 2 and 3 denote a quartz bell jar and a main chamber, respectively, for creating a vacuum atmosphere. Reference numeral 4 denotes an exhaust port for evacuation, and 5 denotes a gas introduction port for etching or plasma cleaning. Reference numeral 6 denotes a substrate stage for fixedly holding the wafer, and reference numeral 7 denotes a mechanical clamper for clamping the wafer. As means for supporting the wafer on the stage, an electrostatic suction means may be used. The clamp 8 is a ground plate, and 9 is a high frequency power supply for applying an RF bias to the wafer stage 6.

The microwave etching apparatus first introduces a gas for plasma generation after evacuation under high vacuum. And
A microwave 10 is oscillated from a magnetron (not shown), introduced into a quartz bell jar 3 (processing chamber) through a waveguide 11, and a solenoid coil 1 disposed around the processing chamber.
The gas in the processing chamber is turned into plasma by resonance (ECR) with the magnetic field formed by step 2 and etching is performed using the plasma 14. An RF bias power is applied between the earth 8 and the wafer stage 6 by a high frequency power supply 9 for the purpose of performing anisotropic etching by drawing ions.

By the way, as a metal wiring material of a semiconductor element, aluminum or an alloy obtained by adding copper, silicon, or the like to aluminum is most commonly used. Recently, in order to improve migration resistance and prevent reflection in lithography, titanium nitride TiN is spread below and above aluminum wiring to form a multi-metal layer.

In order to etch these, chlorine Cl
A gas mixture of 2 and boron trichloride, BCl3, is the most common and widely used. For the etching, plasma of a gas that reacts with the film material to be a compound having a high vapor pressure is used for the film material to be etched. That is, plasma is generated and not only physically struck, but also chemically reacted, and finally evaporated and evacuated to progress the etching. For example, with respect to an aluminum alloy, etching is advanced by generating aluminum trichloride AlCl3 having a high vapor pressure by Cl2 gas plasma. At this time, an aluminum oxide layer is formed on the surface of the aluminum alloy, and in general, boron trichloride BCl3 is mixed with chlorine Cl2 gas in order to easily penetrate the aluminum oxide layer.

According to the analysis of the inventor of the present application, when an aluminum alloy single film or a laminated film of titanium nitride / aluminum alloy / titanium nitride is etched with a mixed gas of chlorine Cl2 and boron trichloride BCl3, the inner wall of the device is etched. Residual deposited film 13
Is a mixture of aluminum and boron chloride, BClx, and it is clear that the proportion of boron chloride is particularly large. FIG. 2 is a schematic diagram showing the composition of the deposited film remaining in the processing chamber.

The remaining deposit of aluminum is removed by generating AlCl 3 having a high vapor pressure by Cl 2 gas plasma as in the case of etching. However, the residual deposit is not only pure aluminum, but also a complex mixture of organic matter from the photoresist used as the mask material and a polymer of the etching gas. How can plasma cleaning with chlorine gas work effectively? Is the decisive factor in removing the residual deposited film. As shown in the schematic diagram of FIG. 2, the residual deposit has a form in which chlorine surrounds the aluminum, so that plasma cleaning with chlorine does not work effectively, and the residual deposit cannot be removed.

FIG. 3 is a schematic diagram showing the function of the plasma cleaning of the present invention. According to the present invention, a series of plasma cleaning steps include a cleaning step using oxygen O2 gas plasma, chlorine Cl2 and boron trichloride BCl3.
Cleaning process using a plasma of a mixed gas of When O2 gas plasma is exposed to chloride, oxygen and chlorine are replaced, and chlorine is vaporized. That is, BClx +
The reaction of O2 → BO + Cl2 occurs, and is removed from the main chamber 3 as Cl2 gas and evacuated. Further, the deposit in the form of BClx is removed as BCl3 by removing Cl molecules, and part of Al contained in the residual deposited film is removed as AlCl3.

By the replacement of oxygen and chlorine by the O2 gas plasma, chlorine surrounding aluminum is eliminated. At this time, the surface of the aluminum is oxidized because the plasma of oxygen is applied. Here, the remaining aluminum oxide can be removed by performing cleaning using plasma of a mixed gas of chlorine Cl2 and boron trichloride BCl3. When aluminum is an oxide, the interatomic bond energy of Al-O is larger than the interatomic bond energy of Al-Cl, so that ClCl alone cannot generate AlCl3 and is removed by cleaning. Can not. Therefore, O is extracted from Al-O by using a plasma containing B2 gas and Bcl3 gas, which has a higher interatomic bond energy to oxygen than Al-O interatomic bond energy. Can be enabled.

Therefore, the cleaning by the oxygen gas plasma needs to be performed at least before the cleaning by the plasma of the mixed gas of chlorine and boron trichloride. In this case, the cleaning with the oxygen gas plasma and the cleaning with the plasma of the mixed gas of chlorine and boron trichloride may be performed continuously, or another plasma cleaning step such as a plasma cleaning of a fluorine-based gas may be performed between them. You may.

[0024]

As described above, according to the present invention, the residual deposited film adhered to the inner wall of the plasma processing apparatus can be efficiently removed. As a result, it is possible to prevent the separation of the deposited film and the generation of dust due to the increase in the thickness of the deposited film (increase in the number of processed sheets), thereby improving the yield in the manufacturing process and improving the operation rate of the manufacturing apparatus. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a plasma processing apparatus to which the present invention is applied.

FIG. 2 is a schematic diagram illustrating a composition of a deposited film remaining in a processing chamber.

FIG. 3 is a schematic diagram showing a state where a residual deposited film is being removed by the plasma cleaning of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Quartz bell jar, 3 ... Main chamber, 4 ... Vacuum exhaust port, 5 ... Gas inlet, 6 ... Wafer stage, 7 ... Wafer clamper, 8 ... Ground, 9 ... High frequency power supply, 10 ... Microwave, 11: waveguide, 12: solenoid coil, 13: residual deposit, 14: plasma.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuo Tsumaki 502, Kachimachi, Tsuchiura-shi, Ibaraki Pref.

Claims (3)

[Claims] A plasma for etching an aluminum film, a film made of a metal compound containing aluminum, or a laminated film having a film containing aluminum on a substrate by using plasma of a mixed gas of chlorine and boron trichloride. A plasma cleaning method for removing residues remaining inside a processing apparatus, comprising a plasma processing step and a plasma cleaning step using plasma for cleaning the inside of the plasma processing apparatus. Cleaning process by plasma,
A plasma cleaning method using a plasma of a mixed gas of chlorine and boron trichloride. 2. The plasma cleaning method according to claim 1, wherein the cleaning with oxygen gas plasma is performed before the cleaning with plasma of a mixed gas of chlorine and boron trichloride. 3. The plasma cleaning method according to claim 1, wherein the cleaning with oxygen gas plasma and the cleaning with plasma of a mixed gas of chlorine and boron trichloride are performed continuously.