JP2735649B2 - Mixed gas composition for cleaning - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention removes deposits deposited on an inner wall of an apparatus other than a target object, a jig, and the like in a thin film forming process such as CVD, vacuum deposition, or sputtering spraying. Cleaning gas mixture composition for cleaning.

[Background Art] In processes for manufacturing amorphous solar cells, liquid crystal devices, integrated circuits, and the like, CVD and sputtering are one of important manufacturing processes.

On the other hand, in these thin film manufacturing processes, a large amount of deposits is deposited on the inner walls and jigs of the device other than the target on which the thin film is to be formed, and particles are generated inside the device or the deposits are separated, thereby deteriorating productivity The problem is that the yield decreases.

Physical methods such as mechanical polishing as measures to remove these deposits, a wet etching method using an aqueous solution, such as alkali, three types of _{CF 4 · SF 6 · NF 3} · ClF 3 gas etching method such as a Means have been taken (for example, JP-A-63-156533). Of these methods, the method requires disassembly of the apparatus in order to perform cleaning, and thus causes problems such as lowering the operation rate of the apparatus and damaging the jig and the apparatus. On the other hand, the gas etching process is a method that has recently been widely used because it is not necessary to disassemble the apparatus by a relatively new method, and the downtime of the apparatus can be reduced.

However, this gas etching process also has some problems and cannot be said to be a perfect method. For example
When using a CF ₄ or SF ₆ are formed by depositing a carbon compound or a sulfur compound not only requires plasma discharge in order to perform the cleaning, it may cause a new pollution. Meanwhile cleaning using ClF ₃ may has a drawback such as having or limited the material which can be used is not necessarily required plasma for strong reactivity of ClF _3, a special contrivance to the supply system for a liquefied gas. Cleaning using NF ₃ is a process with less problems compared to the above method, but has problems such as the fact that plasma discharge is required for cleaning, and the cleaning speed of parts that do not reach plasma is remarkably slow. .

[Means for Solving the Problems] As a result of intensive studies, the present inventor has found a mixed gas composition that solves these problems and efficiently removes and cleans unnecessary deposits in a thin film forming apparatus, and proposes the present invention. Reached.

That is, in the present invention, nitrogen trifluoride contains at least one gas selected from fluorine and halogen fluoride in an amount of 0.05 to 20 vol%.
An object of the present invention is to provide a cleaning mixed gas composition comprising a mixed gas composition.

The main component of the present invention is nitrogen trifluoride, which presently has the fewest problems. The gas is used as a basic composition, and at least one of fluorine and halogen fluoride having high reactivity is mixed. It is possible to effectively clean the deposit made of metal or its compound deposited inside the thin film forming apparatus by compensating for the low reactivity.

As the halogen fluoride of the present invention, ClF, ClF ₃ ClF ₅ , BrF
₃ , BrF ₅ , IF ₅ , IF _{7 and the} like, and these gases can be used alone or as a mixed gas. Further, as described above, the gas to be mixed with nitrogen trifluoride may contain at least one kind of gas among fluorine and halogen fluoride, and of course, two or more kinds may be mixed. The total amount of gas to be mixed is 0.05 to 20 vol%
If it is less than 0.05%, the effect of the mixed gas does not appear, while if it is more than 20 vol%, corrosion or the like is likely to occur depending on the material, and it is difficult to control the etching rate, which is not preferable.

The deposits inside the thin film forming apparatus targeted by the present invention are W,
Si, Ti, V, As, Ge, P, B, Mo, Nb, Ta, Te, Re, Os, Ir, Sb, etc., metals and their compounds, specifically nitrides, oxides, sulfides, Carbides and their intermetallic compounds or alloys of said metals are mentioned.

On the other hand, when the mixed gas composition of the present invention is used for cleaning these deposits, it can be diluted with a rare gas such as oxygen, nitrogen or helium for the purpose of adjusting the cleaning speed. In addition, it is possible to use the mixed gas composition of the present invention in a thin film forming apparatus that has conventionally used nitrogen trifluoride as a cleaning gas, and no special device is required to use the mixed gas composition.

Further, as a secondary effect when the mixed gas composition of the present invention is used for cleaning, it is possible to improve a detection / warning system at the time of gas leakage in a working environment. Nitrogen trifluoride is a colorless and odorless gas, and in the event of a leak, detection is based on the alarm of a detection alarm.

However, these detectors and alarms are still technically imperfect and interfere with many gases other than nitrogen trifluoride, causing many false alarms and frequently causing production to be stopped. On the other hand, mixed fluorine, halogen fluoride and the like have a very strong irritating odor, so that even a very small amount of leakage can be sufficiently recognized, and an independent detection alarm is also known. Therefore, when the mixed gas composition of the present invention is provided with an alarm for both of the mixed gas such as nitrogen trifluoride and fluorine in the working environment, it is possible to detect without leak when the mixed gas leaks. Becomes possible.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 A cleaning test was performed using an apparatus in which amorphous silicon was deposited 10 times by a plasma CVD method and about 3 μm was deposited on an electrode portion and about 2,000 mm of amorphous silicon was deposited on a CVD furnace wall.

Plasma CVD equipment (SUS316 cylindrical type) Inner diameter 450mm Height 300mm Electrode Upper electrode diameter 150mm Lower electrode diameter 100mm Distance between electrodes 50mm High frequency power frequency 13.56 MHz Cleaning condition Furnace pressure 50mTorr Temperature Room temperature Applied power 0.315W / cm ² Gas flow 150SCCM Gas composition NF ₃ 95.2% F ₂ 4.8% Cleaning time 35 minutes Result: After cleaning was completed, the plasma CVD device was released and the inside was inspected. After 35 minutes of cleaning, the amorphous silicon deposited inside the apparatus was completely removed, exposing the stainless steel surface. Furthermore, powdery deposits deposited inside the exhaust officer were almost completely removed and were not visually observed.

COMPARATIVE EXAMPLE 1 Amorphous silicon was deposited 10 times by a plasma CVD method, and a cleaning test was performed using an apparatus in which about 3 μm of an electrode portion was deposited and about 2,000 mm of amorphous silicon was deposited on a CVD furnace wall. The apparatus used in the comparative experiment is the same as the apparatus shown in the embodiment.

Cleaning conditions Furnace pressure 50 mTorr Temperature Room temperature Applied power 0.315 W / cm ² Gas flow 150 SCCM Gas composition NF ₃ 100% Cleaning time 35 minutes Result: After cleaning was completed, the plasma CVD device was released and the inside was inspected. After 35 minutes of cleaning, amorphous silicon deposited inside the device was almost completely removed, exposing the stainless steel surface. However, the powdery deposits deposited inside the exhaust officer were hardly cleaned, and it was impossible to visually confirm the decrease.

Example 2, Comparative Examples 2-3 In order to determine the difference between the effects of the mixed gas composition of the present invention, nitrogen trifluoride and CF ₄ , monocrystalline silicon, silicon nitride deposited on a glass substrate, and graphite substrate After fixing three types of tungsten carbide test pieces deposited at a specified distance from the center of the plasma discharge electrode, plasma etching was performed.

The same etching apparatus as in Example 1 was used, and the etching conditions were a furnace pressure of 50 mTorr, a normal temperature, an applied power of 0.315 W / cm ^{2, a} gas flow rate of 150 SCCM, and a cleaning time of 35 minutes. The results are shown in Table 1. The etching rate was measured using a stylus-type step measuring device (step meter).

As shown in Table 1, the etching rate did not decrease significantly even when the electrode was separated from the discharge electrode in the example, whereas a clear difference was observed in the etching rate as the electrode was separated from the discharge electrode in the comparative example. It is recognized that the cleaning gas mixture composition of the present invention is suitable for cleaning a thin film forming apparatus.

[Effect of the Invention] The cleaning mixed gas composition of the present invention is a mixture of fluorine, halogen fluoride, etc., which is mainly composed of nitrogen trifluoride and has excellent reactivity, and is used for cleaning a thin film forming apparatus having a built-in plasma generator. To provide an effective gas, compared to the conventionally used cleaning gas,
Deposits accumulated inside the exhaust pipe can be removed, and the cleaning performance is excellent, with a high etching rate at locations away from the discharge electrode. It is possible to improve the rate.

Claims (1)

(57) [Claims] 1. A gas for reacting with a deposit of a metal or a compound thereof deposited inside a thin film forming apparatus including an exhaust pipe under plasma discharge and removing the gas as a gas outside the apparatus. A mixed gas composition for cleaning comprising a mixed gas composition obtained by mixing 0.05 to 20 vol% of at least one gas selected from fluorine and halogen fluoride in nitrogen iodide.