JP3175117B2 - Dry cleaning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dry cleaning method.

[0002]

2. Description of the Related Art Semiconductor manufacturing processes include various film forming processes, etching processes, ashing processes, and the like on a semiconductor wafer. In these steps, various process gases are used for film formation or film removal. These process gases may be completely stoichiometrically reacted for each purpose, but some are discharged as unreacted, and some generate unnecessary reaction products. Reaction products adhere and accumulate in the processing vessel.

For example, when dry etching a silicon oxide film, a silicon nitride film or polysilicon formed on the surface of a semiconductor wafer, a fluorine-based gas such as CF ₄ or CHF ₃ has been conventionally used as a process gas. . In the etching using these process gases, the process gas is turned into plasma to generate active species such as ions and radicals, and Si is formed by a physicochemical reaction between these active species and a silicon oxide film exposed in a predetermined pattern.
Volatile gases such as F ₄ and CO ₂ are generated and sequentially discharged and removed from the processing container to the outside.

At the time of etching, the process gas generates a volatile gas as described above, while the active species are recombined without reacting, and the fluorocarbons such as C _X F _Y and C _X F _Y 0 _Z are formed. System polymer is generated as a reaction product,
These adhere and deposit in the processing vessel to form a thin film.
This thin film gradually grows on the inner surface of the processing container and the surface of each part inside the processing container during repeated etching, and becomes thicker, and this thin film eventually peels off and causes particles.
For this reason, such thin films have been conventionally removed by periodic cleaning. As the cleaning method, for example, the above-mentioned thin film is removed using a solvent such as alcohol, or oxygen gas is turned into plasma,
There is a method of removing a thin film with an active species such as the oxygen radical O ^* .

[0005]

However, with the former cleaning method, a great deal of time is required for removal with a solvent, and it is necessary to temporarily stop and disassemble the etching apparatus. In addition, there is a problem that it takes a lot of time to start up, and the operation efficiency of the apparatus is significantly reduced.

Further, in the latter dry cleaning method, if an attempt is made to remove the fluorocarbon-based deposits using active species such as oxygen radicals O ^* in the plasma, the fluorocarbon-based deposits are removed by, for example, the following reaction (1). Although it can be removed in a short time, the fluorine radicals F ^* generated by this reaction will also etch parts in the processing vessel, for example, focus rings made of silicon carbide or silicon, for example, by the following reaction (2). However, these parts are consumed by the cleaning, and the parts must be replaced during the repetition of the cleaning, resulting in a high maintenance cost. _{^{xO * + C X F Y →}} xCO + yF * ······················ (1) 8F * + 2SiC + 3O * → 2SiF 4 + CO + CO 2 ···· (2)

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to efficiently remove a fluorocarbon-based deposit in a short time without disassembling an apparatus. It is an object of the present invention to provide a dry cleaning method capable of remarkably suppressing the consumption of the ink.

[0008]

According to a first aspect of the present invention, there is provided a dry cleaning method for removing a fluorocarbon-based deposit adhered in a processing vessel when processing an object to be processed. , oxygen cleaning gas obtained by adding hydrogen gas to the oxygen gas into plasma the radical
And hydrogen radicals, and the oxygen radicals and the
While removing the fluorocarbon-based deposits by reaction with fluoride carbonaceous deposits, fluorine La produced by the above reaction
Reacting dical with the above hydrogen radical to produce hydrogen fluoride gas
Is to be discharged .

According to a second aspect of the present invention, in the dry cleaning method according to the first aspect, the volume ratio of hydrogen gas to oxygen gas (hydrogen gas / oxygen gas) is set to at least 0.1. It is intended to be adjusted.

[0010] The dry liquid according to claim 3 of the present invention.
The leaning method is a method according to claim 1 or claim 2.
In the above description, the fluorine radical is
In preference to reaction with silicon carbide or silicon components
Reacts with hydrogen radicals.

[0011]

According to the first aspect of the present invention, when a cleaning gas consisting of oxygen gas and hydrogen gas is turned into plasma in the processing chamber, oxygen radicals and hydrogen radicals are generated, and the oxygen radicals become carbon fluoride. Reacts with carbonaceous deposits to generate carbon monoxide gas and fluorine radicals, and hydrogen radicals react with fluorine radicals generated by the reaction with carbon fluoride deposits to generate and discharge hydrogen fluoride gas
However, it is possible to suppress the etching of various components in the processing container due to the fluorine radicals, thereby suppressing the consumption of various components.

According to a second aspect of the present invention, in the first aspect of the present invention, the volume ratio of hydrogen gas to oxygen gas is adjusted to at least 0.1. Is increased, and the reaction with fluorine radicals is stoichiometrically promoted, so that the consumption of various components in the processing container due to the fluorine radicals can be further suppressed.

Further , according to the invention of claim 3 of the present invention.
Then, in the invention described in claim 1 or claim 2 ,
The fluorine radical is silicon carbide or
Hydrogen radicals in preference to reactions with silicon components
Parts made of silicon carbide or silicon
Can reduce the consumption by the reaction with fluorine radicals
it can.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment using the plasma processing apparatus shown in FIG. First, a plasma processing apparatus to which the dry cleaning method of this embodiment is applied will be described. As shown in FIG. 1, the plasma processing apparatus includes a processing container 1 made of a conductive material such as aluminum, and a lower electrode disposed on the bottom surface of the processing container 1 and made of the same material as the processing container 1. And an electrostatic chuck 3 disposed on the upper surface of the lower electrode 2 and holding an 8-inch semiconductor wafer W as a workpiece by Coulomb force
And an upper electrode 4 which is disposed above the electrostatic chuck 3 at a predetermined interval and is made of the same material as the processing container 1.
It is comprised including. Further, the processing vessel 1 is connected to an exhaust device (not shown) via a pipe 5 so that the interior of the processing container 1 is reduced to a reduced-pressure atmosphere, for example, 10 ⁻² Torr or less. It is configured. A high frequency power supply 7 is connected to the lower electrode 2 via a capacitor 6, a high frequency voltage is applied to the lower electrode 2 by the high frequency power supply 7, and etching of CF ₄ or the like is performed between the lower electrode 2 and the grounded upper electrode 4. It is configured to convert the use gas into plasma to generate active species such as ions and radicals. Further, a coolant supply pipe 8 and a gas discharge pipe 9 are connected to the lower electrode 2, and the lower electrode 2 is cooled by the coolant from the coolant supply pipe 8 so as to be maintained at a predetermined low temperature during the etching process. ing.

The upper electrode 4 is formed in a hollow shape, and a supply pipe 4 for supplying an etching gas into the hollow on the upper surface.
A plurality of holes 42 for ejecting an etching gas are dispersedly formed on the lower surface thereof, and an etching gas is supplied from the holes 42 into the processing container 1. Active species such as ions and radicals are generated between the upper electrodes 4 as described above, and the semiconductor wafer W is etched by these active species. Further, a focus ring 10 surrounding the outer periphery of the electrostatic chuck 3 is provided on the lower electrode 2. The focus ring 10 is formed of, for example, silicon carbide or silicon, and is configured so that the plasma formed between the lower electrode 2 and the upper electrode 4 by the focus ring 10 is focused on the semiconductor wafer W.

Next, the operation of the plasma processing apparatus will be described. For example, the semiconductor wafer W is held by the electrostatic chuck 3 on the lower electrode 2 in the processing chamber 1 in a reduced pressure state of 10 ⁻² Torr or less, and then a high-frequency voltage is applied to the lower electrode 2 to make contact with the upper electrode 4. When a discharge space is formed therebetween and CF ₄ gas is supplied as an etching gas into the upper electrode 4 from the supply pipe 41 of the upper electrode 4, the CF
_{The four} gases are supplied into the processing chamber 1 from the plurality of holes 42, turned into a plasma between the lower electrode 2 and the upper electrode 4, and etched, for example, a silicon oxide film on the surface of the semiconductor wafer W by ions and radicals. At this time, in the plasma, CF ₄ is dissociated by the discharge energy and generated F ^* and CF ₃
^* , CF2 ^*, etc., which react with the silicon oxide film to form SiF ₄ , HF, CO, CO
_{2 and the} like are generated and discharged out of the processing container 1. On the other hand, radicals such as F ^* , CF ₃ ^* , and CF ₂ ^* repeat recombination to produce polymers such as C _X F _Y , C _X F _Y 0 _Z, and the inner surface of the processing vessel 1 and the focus ring 10. 2 to form a thin film F made of a fluorocarbon-based deposit as exaggeratedly shown in FIG.

Thereafter, when the thin film F is removed by cleaning, the dry cleaning method of this embodiment is applied. In the dry cleaning method of this embodiment, a mixed gas obtained by adding a hydrogen gas to an oxygen gas is used as a cleaning gas, and the cleaning gas is supplied into the processing vessel 1 from the hole 42 of the upper electrode 4 at a predetermined flow rate by a procedure according to the etching. The cleaning gas is supplied and turned into plasma by the discharge between the lower electrode 2 and the upper electrode 4, and then the carbon fluoride-based deposit made of C _X F _Y is removed by etching with oxygen radicals O ^* . The cleaning conditions at this time were specifically as follows. Pressure in processing vessel: 100 mTorr Power supply to lower electrode: 1450 W Cleaning gas flow rate: 300 sccm Cleaning gas composition ratio: as shown in Table 1 below Cleaning time: 20 minutes

At the time of the above-described cleaning, oxygen gas and hydrogen gas are turned into plasma to generate oxygen radicals O ^* and hydrogen radicals H ^* . And
The oxygen radical O ^* reacts with the fluorocarbon-based thin film F made of, for example, the polymer C _X F _Y according to the above formula (1) to generate carbon monoxide and a fluorine radical F ^* . The fluorine radical F ^* generated at this time reacts with the already generated hydrogen radical H ^* to generate hydrogen fluoride gas and is discharged to the outside. The generation of hydrogen fluoride gas occurs preferentially to the etching reaction on the focus ring 10 according to the above formula (2), that is, the silicon carbide, and suppresses the etching reaction of the silicon carbide due to the fluorine radical F ^* to suppress the consumption of the focus ring 10. I do.

Next, as a result of examining the influence of the addition amount by changing the addition amount of the hydrogen gas as shown in Table 1 below,
The results shown in Table 1 below were obtained. According to this result, the focus ring 10 is consumed by the conventional cleaning gas to which the hydrogen gas is not added, and the focus ring 10 is consumed by the cleaning gas to which the hydrogen gas is added by 10%, but the consumption rate is such that the hydrogen gas is not added. 30% of the case
It was found that the focus ring 10 was hardly etched when the addition amount of hydrogen gas was increased to 25% by further increasing the addition amount of hydrogen gas. Therefore, when the thin film F made of the fluorocarbon-based deposit is removed, consumption of the focus ring 10 can be suppressed by using a cleaning gas obtained by adding a hydrogen gas to an oxygen gas,
It has been found that when the amount of addition reaches at least 25%, the consumption of the focus ring 10 can be reliably suppressed.
The degree of consumption of the focus ring 10 was based on the thickness at the outer periphery of the focus ring 10, and the reduction rate when hydrogen gas was not added was set to 1.

[0020]

[Table 1]

As described above, according to this embodiment, when dry cleaning the thin film F made of fluorocarbon-based deposits deposited and deposited in the processing vessel 1 of the plasma processing apparatus, oxygen gas is used as a cleaning gas. Since a mixed gas obtained by adding hydrogen gas to the processing vessel is used, it is possible to efficiently remove the fluorocarbon-based deposit in a short time, and furthermore, the processing vessel 1
(In this embodiment, silicon carbide and silicon focus ring 10) can be prevented from being consumed. Further, when the volume ratio of the hydrogen gas and the oxygen gas of the mixed gas is adjusted to at least 0.1, the consumption of parts can be remarkably suppressed.

In the above embodiment, the case where the polymer C _X F _Y is removed as the carbon fluoride-based deposit has been described. In this embodiment, however, the fluorocarbon polymer such as the polymer C _X F _Y 0 _Z is removed. The same can be applied to merging. In addition, the present invention can be similarly applied to a plasma processing apparatus used for film formation processing other than etching processing, ashing processing, and the like.

[0023]

As described above, according to the first aspect of the present invention , a processing container is provided for processing an object to be processed.
Dry chest to remove fluorocarbon-based deposits attached inside
In the cleaning method, hydrogen gas was added to oxygen gas
Oxygen radicals and hydrogen by converting the cleaning gas into plasma
Generating radicals, the oxygen radicals and the fluorinated carbon
The above-mentioned fluorocarbon-based deposits are removed by reaction with the silicon-based deposits.
On the other hand, the fluorine radical generated by the above reaction
Reacts with the above hydrogen radicals and discharges as hydrogen fluoride gas
The oxygen radicals without dismantling the device.
Fluorocarbon deposits can be efficiently removed in a short time, and oxygen radicals and fluorocarbon deposits can be removed .
Reaction of fluorine radical generated by the reaction with hydrogen radical
As hydrogen fluoride, and by fluorine radicals.
A dry cleaning method capable of suppressing the consumption of components in the processing container.

According to the second aspect of the present invention, in the first aspect, the volume ratio of hydrogen gas to oxygen gas (hydrogen gas / oxygen gas) is set to at least 0.1. By performing the adjustment, it is possible to provide a dry cleaning method that can significantly reduce the consumption of components in the processing container.

Further , according to the invention of claim 3 of the present invention.
Then, in the invention described in claim 1 or claim 2,
The fluorine radical is silicon carbide or
Hydrogen radicals in preference to reactions with silicon components
Parts made of silicon carbide or silicon
Can reduce the consumption by reaction with fluorine radicals
Can provide a dry cleaning method that can
You.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of a plasma processing apparatus that applies an embodiment to a dry cleaning method of the present invention.

FIG. 2 is a partially enlarged view showing a state in which a thin film made of a fluorine-based deposit is formed in a processing container.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing container 3 Lower electrode 4 Upper electrode 6 Capacitor 7 High frequency power supply 10 Focus ring

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Ogasawara 5-3-6 Akasaka, Minato-ku, Tokyo Inside Tokyo Electron Co., Ltd. (72) Inventor Jun Yashiro 5-3-6 Akasaka, Minato-ku, Tokyo Tokyo Inside Electron Co., Ltd. (72) Inventor Yoshifumi Tahara 5-3-6 Akasaka, Minato-ku, Tokyo Inside Tokyo Electron Co., Ltd. (56) References JP-A-61-222227 (JP, A) JP-A-63- 221620 (JP, A) JP-A-59-11629 (JP, A) JP-A-5-36653 (JP, A) JP-A-4-22123 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 H01L 21/304 645

Claims (3)

(57) [Claims] In a dry cleaning method for removing a fluorocarbon-based deposit adhering in a processing vessel when processing an object to be processed, a cleaning gas obtained by adding a hydrogen gas to an oxygen gas is turned into plasma to generate oxygen radicals. Hydrogen radio
To generate oxygen radicals and the fluorocarbon
Removal of the fluorocarbon-based deposits by reaction with kimono
On the other hand, the fluorine radical generated by the above reaction
A dry cleaning method characterized by reacting with hydrogen radicals and discharging as hydrogen fluoride gas . 2. The dry cleaning method according to claim 1, wherein the volume ratio between hydrogen gas and oxygen gas (hydrogen gas / oxygen gas) is adjusted to at least 0.1. 3. The fluorine radical in the processing container
Preference is given to reaction with silicon carbide or silicon parts
And reacting with hydrogen radicals.
A dry cleaning method according to claim 2.