JPH10233388A - Plasma cleaning method - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a plasma cleaning method for a plasma processing chamber, in which the surface of the plasma processing chamber can be efficiently cleaned. In a plasma cleaning, a plasma reaction step using reactive chemical species and a plasma desorption step for promoting desorption of volatile products are alternately performed. The plasma desorption step to promote the desorption of volatile products need not be a plasma treatment with a noble gas; however,
When this gas is a noble gas, it has an excellent promoting effect on desorption of deposits.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a processing chamber of a plasma processing apparatus, and more particularly to a plasma cleaning method effective for cleaning the inside of a processing chamber.

[0002]

2. Description of the Related Art In plasma processing of a semiconductor substrate,
There are many processes where the deposition of reaction products occurs on the walls of the processing chamber. When this deposit is peeled off and becomes a foreign substance and adheres to the substrate to be processed, it causes a defect in the fine structure, which is a serious problem.

[0003] Deposits can be removed by plasma cleaning. However, at present, it is difficult to perform the plasma cleaning with sufficient time for complete removal because of the problem of the cleaning speed and the restriction of the spread of the plasma. Plasma cleaning is usually
It is performed every 25 days or 100 times, such as every 25 days or 100 times, and suppresses accumulation of deposits.
The generation of foreign matter due to sediment is delayed.

As a method of removing deposits, the treatment chamber may be opened to the atmosphere, and the deposits may be wiped off with water or the like. However, this method requires a very long time to return the apparatus.

For this reason, there is a demand to remove the processing chamber by plasma cleaning without exposing the processing chamber to the atmosphere.

[0006] In addition to semiconductor wafers, there is a demand to remove deposits by plasma cleaning also in plasma etching and plasma CVD used for manufacturing micromachines and fine structures.

[0007] The gas used for plasma cleaning is a gas that reacts with a deposit to form a volatile compound. For information on how to promote removal,
As disclosed in JP-A-7-153751, a patent has been proposed in which a non-gaseous reactive species generating material source is disposed in a processing chamber. Further, as disclosed in Japanese Patent Application Laid-Open No. 7-230954, a method has been proposed in which a processing chamber is sublimated and decomposed and removed by externally heating the processing chamber.

The rare gas is mentioned as one of gases simply diluting the reactive gas in the plasma cleaning of the deposit as disclosed in Japanese Patent Application Laid-Open No. 3-219080.

[0009]

In an apparatus for performing plasma processing on an object to be processed such as a semiconductor substrate, plasma cleaning is performed to remove substances deposited in a processing chamber during the plasma processing. In order to improve the operation rate of the plasma processing equipment, the efficiency of this plasma cleaning was increased,
There is a demand to reduce time. In the plasma cleaning, a deposit in contact with plasma can be removed by utilizing a sputtering effect by ion acceleration and a chemical reaction of radicals. However, in most cases, the processing chamber wall, which is usually subject to cleaning, has no choice but to rely on the sheath electric field to accelerate ions, so the sputtering effect is small, and how to promote the chemical reaction has been an issue. .

As described in JP-A-3-219080, when a rare gas and a reactive gas are mixed, there is a problem that both a reaction step and a desorption step described below cannot be efficiently performed.

[0011]

SUMMARY OF THE INVENTION In the removal of deposits, the inventor has found that in plasma cleaning using only a gas that reacts with deposits to generate volatile substances, part of the products are efficiently removed from the surface. They discovered that they were not removed, and found that by providing a plasma desorption step for positively desorbing the product from the processing chamber and the surface of the deposit, the cleaning speed was dramatically improved.

When a plasma treatment using reactive species (hereinafter referred to as a plasma reaction step) is performed, a part of the volatile substances adheres to the processing chamber, and it takes a very long time to remove the volatile substances by mere high vacuum evacuation. . Therefore, by adding a plasma desorption step after the plasma reaction step, volatile substances remaining on the surface of the processing chamber are desorbed into the gas phase so that a large amount can be removed in a short time.

The plasma desorption step is performed for the purpose of efficiently supplying energy to the inner wall of the processing chamber and the substances adhering to the inner wall of the processing chamber to promote the desorption of the attached volatile substances. Further, it is more preferable to perform the treatment under the condition that the desorbed substances are quickly exhausted.

[0014] After the plasma desorption step, unreacted contaminated sediment surfaces appear. Therefore, when the next plasma reaction step is performed, the reaction is promoted because the reactive chemical species easily bonds to the deposit.

In ordinary plasma cleaning, plasma cleaning is performed under the same conditions for several tens of seconds to several minutes. Some of the volatile substances generated during the plasma cleaning are adsorbed and are not easily removed, and gradually cover the surface of the deposit and start to hinder the plasma cleaning.

Therefore, by performing the plasma reaction process and the plasma desorption process alternately at appropriate time intervals according to the present invention, the deposits can be efficiently produced, rather than performing cleaning continuously for several minutes under a single condition. It is removed from the processing chamber.

Although the processing time of the plasma desorption step or the plasma reaction step is not limited, it is desirable that the plasma desorption step be performed in as short a time as possible under conditions in which desorption and evacuation are advantageous. For example, the plasma processing is performed by alternately repeating that the plasma reaction process is performed for several seconds to several tens of seconds and the plasma desorption process is performed for several hundred milliseconds to several seconds.

Although an appropriate reactive species varies depending on the composition of the deposit, the improvement of the cleaning effect by providing the plasma desorption step can be obtained for any deposit.

A rare gas can be used as an optimal gas for the plasma desorption step.

Since the rare gas has no reactivity, the formation of another compound does not cause the formation of a deposit again. Therefore, when the rare gas collides with the inner wall of the processing chamber, it causes only desorption of the adsorbed gas (which is a volatile gas generated in the plasma reaction process and remains on the surface of the inner wall of the processing chamber), Can be exhausted.

Volatile substances can be desorbed by the energy of the rare gas.

Increasing the output of the plasma generator and increasing the energy input to generate plasma is as follows.
There are limitations depending on the device. By using a rare gas, limited energy can be efficiently used.

Further, it is possible to suppress the re-dissociation of the desorbed substance while adding the reactive gas to the rare gas at about 30% or less, while utilizing the characteristics of the noble gas effective for desorption.

The plasma desorption step can be performed by a plasma treatment other than a rare gas under conditions advantageous for desorption, and a plasma treatment under a lower pressure condition using a reactive chemical species can be performed. Can also. By making the pressure lower (about 5 mtorr) as compared with the plasma reaction process, desorption of volatile products adhering to the wall surface and evacuation can be promoted.

The conditions of the plasma desorption step can be optimized as follows.

In the plasma desorption step, high-speed exhaustion and large flow rate plasma conditions are more advantageous for the exhaustion than in the plasma reaction step. In particular, when the flow rate is increased, the desorbed volatile substances can be quickly exhausted without being re-adsorbed.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an embodiment will be described with respect to cleaning of an etching processing chamber. However, the present invention is not limited to this and can be applied to an ashing processing chamber and a plasma CVD processing chamber. Further, as long as a means for generating plasma is provided in a vacuum processing chamber, the present cleaning method can be applied to a sputtering apparatus or a thermal CVD apparatus.

An embodiment of the present invention will be described below with reference to the drawings for plasma cleaning when etching an aluminum wiring on a semiconductor substrate with an ECR microwave etching apparatus. The film to be etched for aluminum wiring is mainly made of organic polymer resist, aluminum alloy, silicon oxide.
It is a laminated structure of three types of films. First, the configuration of the apparatus to which the present invention is applied will be described with reference to FIG. 1, and then the plasma processing using the plasma cleaning method of the present invention will be described with reference to the flowchart of FIG.

(Description of Configuration) In FIG. 1, a plasma processing chamber 1 (hereinafter simply referred to as a processing chamber) has a stage 3 on which a substrate 2 to be etched (hereinafter simply referred to as a substrate) is mounted.

In the processing chamber, helium, chlorine, boron trichloride, and oxygen are supplied so that they can be supplied. The gas flow controller 4 can quickly control the gas type and gas flow. In addition, the microwave generated from the magnetron 5 is guided to the processing chamber by the waveguide 6, and a current is applied to the coil 7 to apply a magnetic field to generate a high-density plasma. In addition, a high frequency (RF) can be applied to the stage 3 in order to control the manner in which ions are incident on the substrate to be processed. Further, the processing chamber is connected to a pressure gauge 8 and an exhaust system 9 capable of adjusting an exhaust speed to adjust the pressure. For example, the exhaust system includes a turbo-molecular pump with a constant displacement and a butterfly valve (not shown) for adjusting the conductance of the gas flow.
Consists of In addition, the processing chamber has adjacent vacuum chambers 10a and 10b.
There are gates 11a and 11b that can be opened and closed. Through the gates 11a and 11b, the substrates are taken in and out between the processing chamber and the adjacent vacuum chambers 10a and 10b by the vacuum transfer devices 12a and 12b. In the figure, the gates 11a and 11b and the vacuum chambers 10a and 10b
Has shown different cases when the substrate is put into the processing chamber and when the substrate is taken out of the processing chamber, but they may be shared. Further, the vacuum chambers 10a and 10b have gates 15a and 15b respectively in a load chamber 13 for carrying an unprocessed substrate under atmospheric pressure under vacuum and an unload chamber 14 for carrying out a processed substrate from vacuum under atmospheric pressure.
Is connected through. In addition, plasma processing (plasma cleaning) conditions consisting of tens of steps can be set,
The device has a control system 16 that can control the driving parts of the device according to the settings.

FIG. 2 shows a flowchart of the plasma processing to which the plasma cleaning method of the present invention is applied.

The plasma processing roughly includes repetition of loading of an unprocessed substrate into the processing chamber, plasma processing of the substrate, and unloading of the processed substrate from the processing chamber. The timing of plasma cleaning the processing chamber is as follows. After one substrate is processed by plasma (A and B) and after several tens to hundreds of substrates are processed (C), after one substrate is processed, the processed substrate is in the processing chamber. Plasma cleaning can be performed in the state (A) and after the processed substrate is unloaded (B).

In the embodiments described below, first, Embodiments I and II
Shows plasma processing of plasma cleaning at timings (A) and (B), and shows a case of performing plasma cleaning at timing (C) in Example III.

(Embodiment I) In the embodiment I, after one substrate is processed, the plasma cleaning of the present invention is performed at the timing (A) in a state where the processed substrate is present, and after the processed substrate is carried out. The case where the plasma cleaning (B) is not performed is shown.

Table 1 shows the conditions of each step of the plasma cleaning (A).

[0036]

[Table 1]

The purpose of each step will be described.

After the plasma treatment of the substrate, in the No. 1 plasma desorption step, the etching gas adsorbed on the surface of the processing chamber and volatile substances generated by the etching reaction are desorbed from the surface of the processing chamber and exhausted. In the No.2 O2 reaction step,
Remove carbon components. The carbon component is generated by etching the photoresist. In the plasma cleaning using O2, a large amount of volatile products adhere to the processing chamber. No.3
Since the volatile substances in the processing chamber are reduced by the He plasma desorption process, when opening the gate to carry out the substrate,
The amount of reaction products diffused from the processing chamber to the vacuum chambers 10a and 10b is reduced, and contamination outside the processing chamber can be suppressed.

The plasma generation in these steps may be optimized respectively, but the cleaning speed can be increased by performing the plasma generation at the maximum allowable output of the plasma generator.

In order to shorten the cleaning time,
The switching of each step is preferably performed by switching the supply gas while continuing the plasma discharge.

At the end of the cleaning, the cleaning is performed as follows. By the time the plasma desorption process of No. 3 helium is completed, the unprocessed substrate should be ready to be carried into the processing chamber. N
After the helium plasma desorption process of o.3 is completed and a high vacuum is reached, the gates 11a and 11b are quickly opened, the plasma-processed substrate is unloaded, the unprocessed substrate is loaded, and the gate 11
Close a and 11b and start etching the unprocessed substrate. In addition, the processed substrate that has been unloaded is moved so that the next processed substrate does not hinder the unloading from the processing chamber.

Normally, after the plasma processing is completed and a high vacuum is reached, additional vacuum evacuation is performed for several seconds.
Since a helium plasma desorption step for desorbing and evacuating the residue is performed, additional evacuation can be omitted to save time.

In addition to the present embodiment, the following method can be adopted.

After the plasma treatment, a reactive gas step may be performed first, and then a plasma desorption step may be performed. In addition, the plasma reaction process may have a configuration of two or more steps in which the type of reactive gas and conditions are changed.

The gas used in the plasma desorption step is as follows:
In addition to He, Ne, Ar, or Xe may be used, or a gas other than a rare gas that does not adversely affect the plasma-processed substrate may be used if it is performed under conditions advantageous for desorption. The No. 2 plasma reaction step can also be performed using a gas that does not adversely affect the plasma-treated substrate.

(Example II) A case is shown in which, after the processed substrate is carried out of the processing chamber (B), cleaning is performed without the substrate in the processing chamber. Table 2 shows the plasma cleaning steps in this case.

[0047]

[Table 2]

In this case, first, No. in Table 2. Only the plasma desorption process shown in 1 is performed when the processed substrate is in the processing chamber (A). Here, volatile substances generated during the plasma processing are removed.

Next, after the processed substrate is unloaded from the processing chamber (B), No. Perform the second and subsequent steps.

In addition, a high frequency (RF) is applied to the stage to effectively remove volatile substances adhering to the stage when there is no substrate.

The gas used in the plasma reaction process at the timing (B) is not limited to the O 2 gas because the processing substrate is not in the processing chamber, and another reactive gas may be used. This plasma reaction step may be composed of two or more steps, like other plasma reaction steps.

(Embodiment III) In Embodiment III, an example is shown in which the plasma cleaning of the present invention is performed at timing (C) after processing tens to hundreds of substrates. Where 1
The case where plasma cleaning is performed for every 00 sheets will be described.
When 100 substrates are processed, the silicon substrate is brought into a processing chamber by the time the last substrate is carried out. After the plasma desorption process of the last substrate, the silicon substrate is carried into the processing chamber and plasma cleaning is performed.

The plasma cleaning is configured, for example, as shown in Table 3 when the aluminum wiring is etched using an ECR microwave etching apparatus.

[0054]

[Table 3]

This table shows the gases used for each step, the flow rate, the pressure, the plasma processing time of the step, and the purpose of the step.

No. Steps 2, 4, 6, 8, and 10 are a plasma desorption process for efficiently removing reaction products generated by cleaning with a reactive chemical species before and adhering to a processing chamber or a deposit. is there.

As shown in the example, in the plasma of the reactive species, in order to supply a large amount of the reactive species, the pressure is increased and the flow rate is decreased. In the plasma desorption process, in addition to efficiently heating and desorbing volatile products from the wall surface, the pressure is reduced and the flow rate is increased in order to quickly exhaust gas.

In this embodiment, the cleaning of 10 steps shown in Table 2 is repeated for 8 sets (9 minutes), and then the plasma processing is performed with the same kind of gas as the plasma processing conditions for the substrate to be processed. The plasma processing of the substrate to be processed is repeatedly performed.

As in this embodiment, the plasma processing of the substrate 100
Cleaning can be performed for each sheet, but every 25 sheets,
One set of the ten steps in Table 1 may be performed.

In this example, one step is constituted by 3 to 10 seconds. However, one step may be constituted by tens of seconds or tens of seconds, and the number of repetitions may be reduced. In the case where the number of steps is large as in this example, it is particularly necessary to continue the discharge and switch the flow rate immediately.

When the deposit is expected to be a mixture as in this example, the reactive gas can be changed for each step. In addition, for example, when performing a plasma by a reactive gas such as BCl3 and O2 that generates a solid material between the reactive gases in each step, by providing a plasma desorption step between the steps In addition, the amount of solids generated between reactive gases can be reduced.

Although the present embodiment shows the case of the aluminum wiring process, the present invention is not limited to this. The effect of the plasma cleaning method of the present invention comprising the plasma reaction process and the plasma desorption process is the same as that of the silicon oxide film. , Polysilicon, Si3N4, W, WSi, TiN, Cu, Cu alloy, Pt, etc. in the case of an etching process.

In the above embodiment, the case where the plasma source is an ECR microwave is described. However, the present invention can be applied to a high frequency induction type plasma source or a microwave plasma source.

[0064]

As described above, according to the present invention,
A method for efficiently cleaning the surface of a plasma processing chamber by effectively removing volatile substances remaining on the surface of the processing chamber and deposits in plasma cleaning in the plasma processing chamber is provided.

[Brief description of the drawings]

FIG. 1 is a simplified configuration diagram of a dry etching apparatus used for etching a semiconductor substrate.

FIG. 2 is a flowchart of plasma cleaning showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plasma processing chamber, 2 ... Substrate to be etched, 3 ...
Stage, 4 gas flow controller, 5 magnetron, 6 waveguide, 7 coil, 8 pressure gauge, 9 exhaust system, 10a, 10b vacuum chamber, 11a, 11b gate, 12a, 12b vacuum Transport equipment, 13… Load chamber, 14… Unload chamber, 15a, 15
b ... gate.

Claims (12)

[Claims] In a method of performing a plasma processing step of processing an object to be processed carried into a processing chamber with plasma, introducing a gas into the processing chamber, and cleaning with the gas plasma, a material to be cleaned in the processing chamber is provided. A plasma reaction step of converting the gas into a volatile substance by the gas plasma; and a plasma desorption step of desorbing the volatile substance adhering to the surface of the processing chamber and components by the gas plasma. Plasma cleaning method. 2. The plasma cleaning method according to claim 1, wherein the plasma cleaning is performed after performing a plasma processing step on a plurality of workpieces. 3. The plasma cleaning method according to claim 1, wherein after performing the plasma processing step on the object, the plasma cleaning processing is performed next.
Thereafter, the plasma processing step of the next substrate to be processed is repeatedly performed continuously. 4. The plasma cleaning method according to claim 1, wherein said plasma reaction step and said plasma desorption step are alternately performed two or more times. 5. The plasma cleaning method according to claim 1, wherein said plasma reaction step and / or said plasma desorption step comprises two or more steps. 6. The plasma cleaning method according to claim 1, wherein after performing the plasma processing step on the object to be processed, the plasma desorption step is performed, and then the plasma reaction step is performed. A plasma cleaning method, further comprising performing the plasma desorption step. 7. The plasma cleaning method according to claim 1, wherein after performing the plasma processing step on the object, the object is carried out of the processing chamber and the plasma cleaning is performed. A plasma cleaning method comprising: 8. The plasma cleaning method according to claim 1, wherein after performing the plasma processing step on the object, before carrying out the object from the processing chamber,
A plasma cleaning method comprising performing the plasma cleaning. 9. The plasma cleaning method according to claim 1, wherein after performing the plasma processing step on the processing object, the plasma desorption step is performed before the processing object is carried out of the processing chamber. Performing the plasma cleaning, and then carrying out the object from the processing chamber and performing the plasma cleaning. 10. The plasma cleaning method according to claim 2, wherein, after carrying out the object to be processed, a non-processed object is introduced into a position where the object to be processed is processed by the plasma, and the plasma cleaning is performed. A plasma cleaning method comprising: 11. The plasma cleaning method according to claim 1, wherein said plasma reaction step and said plasma desorption step comprise at least one different gas. 12. The plasma cleaning method according to claim 1, wherein the plasma desorption step is performed using a rare gas alone or a mixed gas containing a rare gas in a flow rate of 70% or more.