WO2001071790A1

WO2001071790A1 - Method of manufacturing semiconductor device

Info

Publication number: WO2001071790A1
Application number: PCT/JP2000/001647
Authority: WO
Inventors: Miyuki Yamane; Hiroki Kawada; Hiroyuki Kitsunai; Manubu Yamashita; Takayuki Hayashi
Original assignee: Hitachi, Ltd.; Hitachi Tokyo Electronics Co., Ltd.
Priority date: 2000-03-17
Filing date: 2000-03-17
Publication date: 2001-09-27

Abstract

To prevent the decrease in the yield of a semiconductor device due to reaction products deposited during etching in a process chamber, the chamber is cleaned by generating boron-base plasma, hydrogen chloride plasma and hydrogen plasma in sequence depending on the amount of deposition of reaction products in the process chamber.

Description

Specification

Method for manufacturing semiconductor device

Technical field

The present invention relates to a method for manufacturing a semiconductor device. Background art

2. Description of the Related Art In a semiconductor device, for example, in an electrode wiring forming process, various metal thin films are selectively etched. Etching is performed by reacting a gas used for the etching process with a substance to be etched. However, the reaction products formed by this reaction cannot be exhausted by the exhaust system attached to the processing chamber, but adhere to and accumulate on the inner wall of the chamber and the component surface of the etching processing chamber. The main reaction products are chlorine-based, bromine-based, and boron-based compounds used in the etching gas. Metal-based compounds to be etched are used for masking portions that are not to be subjected to etching. Organic compounds such as photoresist.

Adhering reaction products in the processing chamber deposition (hereinafter referred to as the deposited film), the dust force ^therefrom? Occur. Also, if the etching process is repeated, the deposited film gradually becomes thicker, peels off from the adhered parts (such as the surface of components in the processing chamber), and drops on the wafer, causing device pattern defects. In addition, when the deposition film force ^s increases, a reaction occurs between the deposition film and the process gas, and the actual process becomes unstable, so that etching reproducibility cannot be obtained. As described above, if the sediment is left untreated, the yield strength s decreases, and the device production cost increases significantly. From this it is necessary to remove these when the deposited film reaches a certain amount.

Examples of the method include a wet cleaning method in which a semiconductor device manufacturing apparatus is opened to the atmosphere and a deposited film is wiped with a solvent such as alcohol or pure water. There is a dry cleaning method that removes the deposited film by generating plasma using chlorine gas, boron-based gas, oxygen gas, or the like, as disclosed in Japanese Patent Application Laid-Open No. 10-261623. Disclosure of the invention

However, the pet cleaning method needs to periodically open the apparatus to the atmosphere and disassemble the semiconductor device manufacturing apparatus. Further, after the wet cleaning, the device must be evacuated to a predetermined vacuum again before the semiconductor device can be manufactured. Once the device has been released to the atmosphere, the process chamber must be evacuated for several hours before returning to the original vacuum: I dog state due to adsorption of moisture in the atmosphere. As described above, in the wet cleaning method, since it takes time to evacuate to a predetermined vacuum for each cleaning, a significant decrease in the operation rate of the apparatus and a decrease in throughput are caused.

In the conventional dry cleaning method represented by the example disclosed in Japanese Patent Application Laid-Open No. Hei 10-261623, a material to be etched or a deposited film or plasma due to a reaction product between a photoresist as a mask material and a process gas is used. Accordingly, it is possible to remove ion sputters formed by hitting members in the apparatus, and deposited films formed by reaction products between members in the apparatus and process gases.

But force ^s' et al, can not be prevented actually this decrease in yield of the conventional semiconductor device due to the reaction product of a process chamber in the dry cleaning method etching process be conducted chestnut-learning using Was.

An object of the present invention is to prevent a decrease in the yield of semiconductor devices due to a reaction product in a processing chamber in a semiconductor device manufacturing process, particularly in an etching process.

As a result of research conducted by the present inventor to solve the above-described problems, the conventional dry cleaning method can remove the deposited film formed during etching, but the reaction formed by the cleaning gas used at this time was not used. Product in the device Dry cleaning force, which is originally used to reduce the amount of deposited film that may cause foreign matter, is newly created as a cause of foreign matter, and reduces the cleaning effect in the equipment. And found the present invention.

An object of the present invention is a method of manufacturing a semiconductor device having an etching step of etching a film formed on a semiconductor wafer in a chamber, and the following steps are performed according to the state of a substance attached to the chamber. Will be resolved.

(1) After supplying a wafer into the chamber, a plasma of a gas containing a boron-based gas is generated in the chamber, and then a plasma of hydrogen chloride gas is generated in the chamber. A plasma of hydrogen gas is generated at the beginning.

(2) After supplying a wafer into the chamber, a plasma of a gas containing a boron-based gas is generated in the chamber, and then plasma of the chamber hydrogen gas is generated. '

Plasma of a gas containing a boron-based gas is effective for removing deposits, particularly when the deposit is an aluminum compound. As a gas containing a boron-based gas, for example, a mixed gas of boron trichloride and chlorine gas is suitable, but it is also effective to use another boron-based gas such as BBr ₃ .

According to the present invention, it has been found that a boron-based reaction product is generated by the plasma of the gas containing the boron-based gas.

In the above method (1), hydrogen chloride gas plasma is performed to remove the boron-based reaction product, and chlorine gas adsorbed to the chamber during the hydrogen chloride plasma is removed. A hydrogen plasma is generated for the purpose.

In the above method (2), hydrogen plasma is continuously generated in order to remove the boron-based reaction product.

In the above method (1), the boron-based reaction product is produced at high speed by hydrogen chloride plasma. Since processing can be performed, the entire tallying processing time can be shortened. Since the method (2) does not use highly corrosive hydrogen chloride gas, it is possible to prevent corrosion in the semiconductor device manufacturing equipment. Also, since two types of gas are used, process control is easy. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a structural view of a microwave etching apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a wiring pattern according to the embodiment of the present invention.

FIG. 3 is a device manufacturing procedure according to the embodiment of the present invention.

FIG. 4 is an explanatory view of a method for monitoring a deposited film adhesion state according to the embodiment of the present invention. FIG. 5 is an explanatory diagram of a method for monitoring a deposited film adhesion state according to the embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION.

A first embodiment of the present invention will be described in detail with reference to the drawings. The outline of the manufacturing process of semiconductor devices is as follows. 'The formation and removal of the oxide film and the nitride film are selectively repeated on the semiconductor wafer. Then, they are selectively removed, and boron and phosphorus are diffused in the part. After that, formation of gate electrode, formation of interlayer insulating film for multilayer wiring, formation of contact hole for wiring connection, deposition of aluminum thin film for wiring between elements, formation of wiring pattern by removing unnecessary aluminum, formation of protective film It is formed in the order of formation and pad opening.

Although semiconductor devices are substances forces are film and diffused is formed on the wafer Ri on the ^type? Different, the gate electrode, an interlayer insulating film, contactors Tohoru, the electrode wiring film formation, wiring pattern formation, the protective film formation, the pad opening Manufactured through a hole process

FIG. 1 shows a configuration diagram of a microwave etching apparatus used in the above wiring pattern forming step. In the figure, 101 is an upper channel, 102 is a lower channel 105, and a quartz window is formed therein, in which a vacuum atmosphere is created. 103 is a waveguide and 104 is a microwave. The microwave 104 passes through the quartz window 105 through the waveguide 103 and is introduced into the upper chamber 101. 107 is a quartz tube which is installed inside the upper chamber 101. This is to prevent the surface of the upper chamber 101 from being etched by the plasma. Reference numeral 108 denotes a table, which is provided in the upper chamber 101 so as to face the English window 105. 109 is a silicon wafer (substrate) to be subjected to fine processing. The silicon wafer 109 is detachably placed on the table 108 by means such as electrostatic attraction. '110 is an electromagnetic coil, which is arranged concentrically outside the upper chamber 101. The state of plasma generation can be controlled by applying a current to the coil 110. On the other hand, 111 is an exhaust gas, which is connected to the lower chamber 102, and gas used for etching and cleaning processing is exhausted from here ^).

FIG. 2 is a diagram showing a wiring pattern formed according to the present embodiment. Figure 3 shows the manufacturing procedure.

'First, according to the etching procedure 301, the silicon wafer 109 is etched. ′ The upper chamber 101 and the lower chamber 102 are exhausted from the exhaust duct 111. The introduction chamber (not shown) for introducing the silicon wafer 109 is also evacuated similarly. When the upper chamber 101 and lower chamber 102 is evacuated to about 10- ⁶ Torr, the introduction chamber, ^mosquitoes? Silicon wafer 109 formed is conveyed (aluminum thin film 205 in this embodiment) the object to be etched , On the table 108. On the surface of the transferred silicon wafer 109, a device structure as shown in FIG. 2 is formed. An interlayer insulating film 204 is formed on the memory and structure including the bit line 201, the lead line 202, and the storage electrode 203. An aluminum thin film 205 is already formed on the upper part, and the upper part is covered with a resist 206. Part of the aluminum thin film 205 is etched by an etching process. A portion of the resist 206 is vacant so that the removed portion is exposed for removal. Then, as an etching gas, a mixed gas of chlorine gas at a partial pressure of about 1.2 Pa and a boron trichloride gas at a partial pressure of about l.OPa is introduced into the upper chamber 101. An electric current ⁵ is supplied to the electromagnetic coil 110 outside the upper chamber 101. A microwave 104 having a frequency of about 2.45 GHz and 800 W is introduced from the microwave waveguide 103, thereby generating a plasma in the upper chamber 101. A high frequency of 2 MHz is applied to the lower surface side of the silicon wafer 109 at 60 W, and the etching target on the silicon wafer 109 is etched. That is, a portion of the surface of the aluminum thin film 205 that is not covered with the resist 206 is etched away, and the underlying interlayer insulating film 204 is exposed at that portion. When plasma is generated for a predetermined period of time and the etching of the aluminum thin film 205 is completed, the introduction of microwaves, the application of high frequency, the introduction of coil current and etching gas is stopped, and the silicon wafer 109 is carried out from the upper chamber 101 to the introduction chamber. Is done.

According to the etching processing procedure 301, several silicon wafers to be processed are repeatedly performed. When the etching process is repeatedly performed, the etching process causes a reaction generated by an etching reaction of the aluminum thin film 205, the resist 206, and the like on the inner surface of the upper chamber 101, the lower chamber 102, and the quartz tube 107, which is a constituent member of the chamber. When the material is attached to the deposited film 112 as in the deposited film 112 shown in FIG. 1 and has a certain thickness, dust and debris are generated from the deposited film 112 and are discharged into the upper chamber 101. If these adhere to the surface of the device part to be etched, defective etching will occur, resulting in defective device fabrication. Therefore, it is necessary to remove or reduce it in some way.

Therefore, by monitoring the adhesion state of the deposited film on the inner surface of the quartz tube 107 in the upper chamber 101 without opening the etching apparatus to the atmosphere, the material of the deposited film 112 adhered to the inner surface of the stone tube 107 or the like is monitored. And clarified its cleaning method.

Fig. 4 shows an embodiment of the method for monitoring the adhesion state of the deposited film 112 on the inner surface of the quartz cylinder 107. Show. An incident gas analyzer 401 is attached to the side surface of the upper chamber 101 so that gas ions and the like incident on the wall surface of the upper chamber 101 can be sampled. In addition, a sample 402 for examining the adhesion state of the deposited film 112 is provided in the upper chamber 101, and the sample is irradiated with infrared light introduced from an infrared light introduction window 403 to reflect and reflect the light. The state of the deposited film 112 adhering in the upper chamber 101 can be monitored by measuring. The method of monitoring the surface state in the upper chamber 101 by the reflection-absorption vector of the infrared light has a structure as shown in the plan sectional view of FIG. The infrared light 501 is incident from an infrared light introduction window 403. For this window, a material called KRS-5, which has high transmittance of infrared light, is used. In addition, in order to suppress the dispersion of the measured values due to the fogging of the window, the absorption spectrum can be obtained by polarizing the infrared light with the polarizer '502 and subjecting the infrared light 501 to spectroscopy. . The infrared light 501 reflected on the sample 402 is detected by the detector 503. Since the inner surface of the upper chamber 101 is covered with the quartz cylinder 107, the state of the deposited film 112 adhering to the upper chamber 101 may be determined by examining the behavior on the quartz. Therefore, the sample 402 has a force using an aluminum-evaporated mirror with high reflection efficiency, and its surface has a thickness of about

A quartz film of about 0.6 / m was deposited. Since the infrared light of a specific wavelength is absorbed by the bonding state of the atoms of the deposited film 112 attached to the surface of the sample 402, by examining the absorption spectrum of the infrared light detected by the detector This makes it possible to monitor the adhesion state of the deposited film 112.

According to this method, the deposited film 112 adhering to the inner surface of the quartz tube 107 in the upper chamber 101 was examined in the etching treatment procedure 301, and as a result, the chlorine atom used as the etching gas and the aluminum-based compound used as the object of the etching treatment were determined. For the first time, it was revealed that, besides the organic compounds from the photoresist, a B0-based compound force, in which a boron atom and an oxygen atom were bonded, was formed. It is considered that boron atoms are supplied from the etching gas, and oxygen atoms are supplied from the quartz cylinder 107 in the upper chamber of the photoresist. Oxygen gas and chlorine gas Of the deposited film 112 adhering to the inner surface of the quartz tube 107 in the upper chamber 101 during the conventional dry cleaning using a gas containing boron and boron atoms. Was not completely removed, and was also formed during the cleaning process. This is considered to be the source of gas containing boron atoms used in the cleaning process. From the above, a dry cleaning method in which the B0-based compound remaining in the upper chamber 101 during the repeated etching treatment procedure 301 is removed and the by-product B0-based compound is not formed by the cleaning gas is performed. developed. Figure 3 shows the specific method.

First, a plasma cleaning process (a) 302 is performed. The purpose of this treatment is to remove the metal compounds in the aluminum thin film that has been etched. First, the inside of the upper chamber 101 and the lower chamber 102 is evacuated from the exhaust duct 111. After subsequent pressure in the upper chamber 101 reaches about 10- ⁶ Torr, and conveys the silicon Kon'weha 109, placed on the platform 108. The silicon wafer 109 in the case of the dry cleaning process does not need to be a product wafer, and a dummy wafer or the like coated with an oxidation film is used.

As a cleaning gas, a boron-based gas is used to remove aluminum-based compounds in the deposit 112. Aluminum compounds can be removed by chlorine gas alone, but by introducing boron-based gas, aluminum oxide is decomposed in the aluminum-based compound, so the reaction between chlorine atoms and aluminum It is known that the effect of promoting the removal of aluminum compounds is enhanced. Therefore, using boron trichloride as a boron-based gas, a partial pressure of about l.OPa is introduced to decompose the aluminum oxide. At this time, chlorine gas is introduced at a partial pressure of about 1.2 Pa to promote the reaction between decomposed aluminum and chlorine atoms, and to produce aluminum chloride with high vapor pressure, thereby efficiently producing aluminum-based compounds. Is removed. A predetermined current is supplied to the coil 110 outside the upper chamber 101, and the coil used in this embodiment is divided into four stages, and 18A, 17A, 12A, and 16A flow from above. Microwave introduction tube 103? Plasma is generated in the upper chamber 101 by introducing a microwave 104 having a frequency of about 2.45 GHz and 1000 W. The high frequency was applied to the silicon wafer 109 during the etching process, but is not required during the plasma cleaning process. By not applying a high frequency to the silicon wafer 109, the plasma and the reaction product deposited on the upper chamber 101 are apt to react with each other, and the effect of removing the deposited film 112 is improved. The generated plasma of boron trichloride gas promotes the decomposing power ^s of aluminum oxide, and generates aluminum chloride having a higher vapor pressure when introducing chlorine gas, is discharged into the upper chamber 101, and is exhausted. Exhausted and removed from duct 111. After the plasma is generated for a time necessary to remove the aluminum-based compound, the introduction of the microwave 104 and the introduction of the current and the cleaning gas to the coil 110 are stopped.

However, according to the above-described method of monitoring the adhesion state of the deposited film, in the cleaning process 302, since a boron-based gas is used, a boron-based reaction product remains in the upper chamber 101. Can be confirmed.

Therefore, a new cleaning process (b) 303 is performed. This is intended to remove the boron-based reaction product formed by the cleaning treatment (a) 302.

In the pre-cleaning process ( _a ) 302, after the plasma is generated for a predetermined time, the introduction of the microphone mouth wave 104 is a force for temporarily stopping the current and the like to the coil 110, and the silicon wafer 109 is put on as it is without being carried out. deep. Then, the cleaning gas is switched to hydrogen chloride gas and introduced into the upper chamber 101. About 1.5Pa of hydrogen chloride gas is introduced at a partial pressure. The plasma is generated in the same manner as in the cleaning process (a) 302. The generated hydrogen chloride plasma changes the boron compound into a BH compound, for example, BH ₃ , B ₂ H _6, etc. The gas is discharged into the upper chamber 101 and exhausted and removed from the exhaust duct 111. After the plasma is generated for a predetermined time, the introduction of the microwave 104, the current to the coil 110, and the introduction of the cleaning gas are stopped. . However, when hydrogen chloride gas is used, the silicon wafer 109 is not carried out, but is left as it is, and the silicon wafer 109 is subjected to the taring process (c) 304-.

Finally, the cleaning process (c) 304 is performed. This is intended to remove the chlorine gas adsorbed in the upper chamber 101 when performing the cleaning process using hydrogen chloride in the cleaning process (b) 303.

The cleaning gas uses hydrogen gas. By the generation of hydrogen plasma,

The reaction of H-C1 is caused to be released into the upper chamber 101 and exhausted and removed from the exhaust duct 111. The plasma may be generated in the same manner as in the cleaning process (a) 302. As a result, even if the processing chamber is opened to the atmosphere after the plasma cleaning process, safety for workers is ensured because the toxic gas is removed. In addition, if plasma is generated by mixing ^ in argon gas instead of hydrogen gas, water molecules dissociate and hydrogen atoms are generated, and the H-C1 reaction described above occurs. It is possible to remove toxic gas from the upper chamber 101.

In addition, although hydrogen chloride gas was used in the cleaning treatment (b) 303, the same effect can be obtained by introducing hydrogen gas instead of introducing hydrogen chloride gas.

In the cleaning process ( _a ) 302, after generating the plasma for a predetermined time, introduction of the microphone mouth wave 104 and current to the coil 110 are temporarily stopped, but the silicon wafer 109 is not carried out. Leave it on. Then, the cleaning gas is switched to hydrogen gas and introduced into the upper chamber 101. Hydrogen gas is introduced at a partial pressure of about 1.5Pa. The plasma may be generated in the same manner as in the cleaning process (a) 302. By the generated hydrogen plasma, the boron-based compound is converted into a BH compound, for example, BH ₃ , B ₂ H _6, etc., released into the upper chamber 101, and exhausted and removed from the exhaust duct 111. After generating the plasma for a predetermined time, the introduction of the mark mouth wave 104 and the introduction of the current and the cleaning gas to the coil 110 are stopped. Then, the silicon wafer 109 is carried out to the introduction chamber. In the cleaning treatment (b) 303, if hydrogen gas is used instead of hydrogen chloride gas, the number of treatment steps can be reduced by one, so that process control becomes easy. In addition, since highly corrosive hydrogen chloride gas is not used, damage to semiconductor device manufacturing equipment is small. '' In order to remove boron-based compounds, plasma generation time is more than twice as long as when hydrogen chloride gas is introduced. However, although one process is increased, the entire cleaning processing time is shortened. Therefore, when considering the production efficiency of semiconductor devices, it is more advantageous to use hydrogen chloride gas.

By sequentially performing such cleaning processes (a), (b), and (c), reaction products deposited in the upper chamber 101 and the like during the etching process are removed, and by-products due to the cleaning gas are also removed. can do. Then, the etching process 301 is repeatedly performed.

In the dry cleaning method described in this embodiment, the case where chlorine and boron trichloride are used as the etching gas in the etching process 301 has been described.However, when another boron-based gas such as BBr ₃ is used. It is also effective in In the semiconductor device shown in FIG. 2, the metal thin film 205 is also effective when it is a thin film of an alloy containing aluminum in addition to the aluminum single-layer film. .

Next, a second embodiment of the present invention will be described in detail with reference to the drawings. This embodiment relates to an etching process when the aluminum thin film 205 in FIG. 2 is a tungsten-silicon oxide film.

A fluorine-based gas force is used for the etching of these materials. In the etching process in this case, a compound containing fluorine, an organic substance from a photoresist, tungsten, silicon, and the like adheres to the upper chamber 101, the quartz tube 107, and the like. When a fluorocarbon-based gas is used as an etching gas, the alumina component forming the upper chamber 101 is hit with plasma, and fluorine atoms of the etching gas and aluminum of the alumina component combine to form a fluoride gas. Lumi is formed and adheres. This aluminum fluoride is very difficult to remove by the conventional dry cleaning method, and remains in the upper chamber 101 or the like, and increases the generation of dust, which is a major factor in lowering the yield.

However, it was confirmed by the monitoring method shown in FIG. 5 that such a deposited film was also removed by performing the same procedure in the dry cleaning method shown in FIG. That is, no by-products are formed by the cleaning gas, and the reaction products deposited in the upper chamber 101 and the like can be removed.

Object Etchingu in the first embodiment and the second embodiment, aluminum, tungsten, ^force? Described for silicon Sani匕膜, in each case as platinum Ya Ruteniu beam to other, the chamber by the etching process more performing the Doraikuri-learning the procedure of FIG. 3 as long as the compound of aluminum is deposited in one, the same effect ^mosquito? obtained.

Further, the force in the first embodiment and the second embodiment is described as an example of dry Etsu quenching ^process?, In CVD processes and sputtering process, by performing dry cleaning in the procedure of FIG. 3, the same effect can get. The inventor of the present application conducted a search of known examples based on the results of the present invention, but found no known examples suggesting the present invention.

The use of hydrogen gas or hydrogen chloride gas as the plasma cleaning method has been described in JP-A-6-302565, JP-A-3-62520, JP-A-10-74732, etc. Is a technique for removing a deposited film formed by an etching process, and is not a method for removing a deposited film formed by plasma cleaning as in the present application. There was no suggestion about combining with a boron-based gas.

According to the present invention, it is possible to prevent a decrease in the yield of semiconductor elements due to a reaction product in a processing chamber in an etching step.

Claims

The scope of the claims

1. A method for manufacturing a semiconductor device having an etching step of etching a film formed on a semiconductor wafer in a chamber, wherein the method includes the steps of: Supplying a wafer;

Introducing a gas containing a boron-based gas into the chamber after supplying the wafer;

Generating a plasma of a gas containing the boron-based gas;

Introducing a hydrogen chloride gas into the chamber after generating a plasma of a gas containing the boron-based gas;

Generating a plasma of the hydrogen chloride gas;

Introducing a hydrogen gas into the chamber after generating the plasma of the hydrogen chloride gas;

Generating a plasma of the hydrogen gas;

For manufacturing a semiconductor device.

2. A method for manufacturing a semiconductor device having an etching step of etching a film formed on a semiconductor wafer in a chamber, the method comprising the steps of:

Supplying a wafer into the chamber; and introducing a gas containing a boron-based gas into the chamber after supplying the wafer.

Generating a plasma of a gas containing the boron-based gas;

Introducing a hydrogen gas into the chamber after generating a plasma of the gas containing the boron-based gas;

A method of manufacturing a semiconductor device, comprising the steps of: generating a hydrogen gas plasma.

3. The method according to claim 1, wherein the film is an aluminum thin film, and a gas used in the etching step is a gas containing a chlorine atom.

4. The method of manufacturing a semiconductor device according to claim 1, wherein a high frequency is not applied to the wafer.

5. The method for manufacturing a semiconductor device according to claim 1, wherein the gas used in the etching step is a gas containing a fluorocarbon-based gas, and the chamber is provided with an alumina component.

6. A method for cleaning an etching apparatus for etching a film formed on a semiconductor wafer in a chamber, the method comprising:

A step of removing the aluminum-based compound attached to the chamber in the etching step by using a plasma of a boron-based gas;

Removing the boron-based reaction product adhered to the chamber using the plasma of hydrogen chloride gas in the step of removing using the plasma of boron-based gas; and removing the reaction product using the plasma of hydrogen chloride gas. Removing the chlorine gas adsorbed in the chamber using a plasma of hydrogen gas in

A cleaning method for an etch sig device provided with:

7. A method for cleaning an etching apparatus for etching a film formed on a semiconductor wafer in a chamber, the method comprising:

Removing the aluminum-based compound attached to the chamber in the etching step using a plasma of a boron-based gas;

Removing the boron-based reaction product attached to the chamber using hydrogen gas plasma in the step of removing using the boron-based gas plasma.