JPH09320963A - Method for conditioning a CVD chamber after cleaning - Google Patents

Abstract

(57) [Abstract] (Corrected) [PROBLEMS] To effectively remove fluorine residues and particles from a CVD chamber. A multi-step process is performed after cleaning,
Used to condition the chemical vapor deposition chamber during the subsequent deposition process, which removes fluorine residues from the chamber with a hydrogen plasma and subsequently deposits solid compounds in the chamber and leaves them in the chamber. This is done by wrapping the particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is broadly applicable to chemical vapor deposition (C
VD) processing. In particular, the present invention relates to conditioning a CVD chamber after it has been cleaned and prior to the next CVD process.

[0002]

BACKGROUND OF THE INVENTION CVD is, for example, intrinsic.
nsic or doped amorphous silicon, silicon oxide, silicon nitride, oxynitr
ide) Widely used in the semiconductor industry for depositing films of various materials such as silicon and other similar compounds on substrates. Modern semiconductor CVD processes are commonly performed in a vacuum chamber by heating a precursor gas, which dissociates and reacts to form the desired film. A plasma can be formed from the precursor gases in the chamber during deposition to deposit the film at low temperatures and at relatively high deposition rates. Such a process is a plasma enhanced chemical vapor deposition process.
nced chemical vapor deposi
known as PECVD.

The state-of-the-art CVD chamber is made of aluminum and includes a support for the substrate to be processed and an inlet port for the required precursor gas. When plasma is used, the gas inlet and / or substrate support is connected to a power source, such as a radio frequency (RF) power source. A vacuum pump is also connected to the chamber to control the pressure within the chamber and to remove various gases and particles generated during deposition.

As semiconductor devices on substrates get smaller and closer to each other, particles in the chamber must be kept to a minimum. During the deposition process, not only the deposited film deposits on the substrate, but also various fixtures such as walls and shields in the chamber, substrate supports, etc.
Particles are also formed due to the deposits. During further subsequent deposition, the film, such as on the walls, can crack and flake off, causing contaminant particles to drop onto the substrate. This causes and damages certain devices on the substrate. When individual devices or dies are cut from eg a silicon wafer, it may happen that damaged devices, eg transistors, have to be discarded.

Similarly, when large glass substrates are processed to form thin film transistors for use as computer screens and the like, millions of transistors are formed on a single substrate. In this case, the presence of contaminants in the processing chamber is also a serious problem. This is because computer screens and the like will not work if damaged by particles.

Therefore, the CVD chamber must be regularly cleaned to remove particles between one deposition step and the next. Cleaning is generally etching gas,
This is done by passing a particularly fluorine-containing gas, such as trifluoride nitrogen, through the chamber. Next, plasma is generated from the fluorine-containing gas. The gas reacts with the coating produced on the chamber walls and fixtures by the preceding deposition, i.e. the coating of amorphous silicon, silicon oxide, silicon nitride, etc. and any particles in the chamber to form a gaseous fluorine containing product. . The product can be exhaled through a chamber exhaust system. Generally, a nitrogen purge is then performed.

[0007]

However, after this cleaning process, residual fluorine (fluorine resi
It was found that the dues) remained in the chamber and, more importantly, the particles were not completely removed from the chamber. The residual fluorine can adversely affect the film quality of subsequently deposited films, especially amorphous silicon on silicon nitride films, and also shifts the threshold voltage of devices created therefrom. The presence of particles can damage the device on the substrate.

As described above, the CVD chamber is adjusted (con) between the deposition process using the nitrogen-containing gas.
Then, there is a need for a process that can remove any residual fluorine that remains in the chamber and at the same time prevent particles that remain in the chamber from falling onto the substrate.

[0009]

We have found a multi-step conditioning process for a CVD chamber after the chamber has been cleaned of unwanted deposits using a fluorine-containing gas. The process removes residual fluorine from the chamber and reduces the number of particles in the chamber that may fall onto subsequently processed substrates.

In the preceding cleaning step, fluorine flows into the chamber where it reacts with unwanted deposits and particles. In the first conditioning step of the present invention, a plasma is generated in the chamber from hydrogen, which reacts with the fluorine residue remaining in the chamber. These are wiped out. In the second conditioning step, the plasma is formed from the deposition gas mixture, forming a layer of solid compound on the walls and fixture of the chamber, and removing any particles left on the inner surface of the chamber. Wrap it effectively.

The deposition gas mixture is silane.
Can be used, and a co-reactant (co-re
Actants) may be added to form a solid silicon compound such as silicon oxide or silicon nitride in the chamber.
Instead, the deposition gas mixture is tetraethoxysilane (TEO).
S) and oxygen, which form a silicon oxide compound. Generally, the deposition gas mixture used in the conditioning process uses some of the same gases used to deposit the film on the substrate.

[0012]

DETAILED DESCRIPTION OF THE INVENTION U.S. Pat. No. 5,366,585 issued to Robertson et al. Discloses a PECVD chamber suitable for processing large area glass sheets. Referring now to the figures, the vacuum chamber 113 enclosed by the reactor housing 112 includes a hinged lid. A gas manifold 132 is located above and parallel to the susceptor 116 on which the substrate is mounted during processing. The gas manifold 132 includes a face plate 192, which has a plurality of orifices 193 for supplying process and purge gases therein. The RF power source 128 creates a plasma from the supplied gas.

Adjacent to the housing 112 is a set of ceramic liners 120, 121, 122.
The metal wall is insulated so that an arc does not fly between the housing 112 and the susceptor 116 during plasma processing. These ceramic liners 120, 12
1, 122 can also withstand a fluorine-containing etching cleaning gas. Also, a ceramic ring (an
123) is attached to the face plate 192 and provides electrical insulation for the face plate 192. These ceramic components also keep the plasma away from, thereby helping to confine the processing plasma near the substrate and to reduce the amount of deposition that builds up on the walls of the housing 112.

After the last substrate on which the layer is to be deposited is removed from the chamber, standard fluorine containing gas cleaning is first performed in the chamber in the conventional manner. 3
800 scc of trifluoride nitrogen
m flow is established by wide opening the gas inlet valve, creating a pressure of 200 mTorr in the chamber. The susceptor and gas manifold are now spaced 1600 mils apart. A 1600 watt RF power source is used in the gas manifold to generate the plasma. The cleaning plasma is continued for about 1 minute for each 2000 Å of amorphous silicon film previously deposited in the chamber. The cleaning plasma is applied to the silicon nitride film 4 previously deposited on the substrate in the chamber.
Approximately 1 minute per 000 angstroms is additionally continued.

The two-step adjustment process is followed by the above CV.
D Used to remove residual fluorine remaining after the chamber cleaning step, and to deposit thin inert solid compound films on fixtures and walls within the chamber to enclose particles.

As an example of this process, in the first adjustment step, 1200 sccm of hydrogen is flowed into the chamber for 30 seconds, and a plasma of hydrogen is formed in the chamber by using 300 watts of power to create the plasma. Was done. The hydrogen plasma that reacted with the fluorine present in the chamber formed hydrogen fluoride (HF), which could be easily removed via the chamber exhaust system. The chamber was maintained at a temperature used for subsequent deposition and a pressure of 1.2 Torr. The spacing between the substrate support and the gas manifold was 1462 mils.

In the second conditioning step, a thin film of silicon nitride was deposited under the same spacing, temperature and pressure conditions, but with the power increased to 800 watts and the gas changed. Silicon nitride film is 100sccm of silane, 5
It was deposited by additionally flowing 00 sccm of ammonia and 3500 sccm of nitrogen into the chamber for 30 seconds.

In this way, the total time required to condition the chamber for the subsequent deposition process is only about 1 minute. A thin silicon nitride film covers the walls and fixtures of the chamber, thereby encapsulating and sealing any particles that may remain in the chamber after the cleaning process and prevent them from falling onto the substrate being processed. . The deposited silicon nitride layer also reduces outgassing from the wall material and reduces residual fluorine-containing material from the chamber.

The two-step conditioning process described above is used with a standard cleaning process that includes cleaning stabilization, plasma cleaning with a fluorine-containing gas, followed by a nitrogen purge.
After the suicide deposition and hydrogen plasma treatment of the conditioning process, the chamber may be purged with nitrogen.

The process described above is preferred in that it removes fluorine-containing residues and reduces the number of particles in the chamber while minimizing system throughput degradation.

Alternative single-step conditioning processes using the same amount of processing time have been tried so far, but they are not as efficient as the process of the present invention. A single 60 second silicon nitride deposition process is effective at reducing particles, but less effective at reducing fluorine residues. It also creates a thicker wall deposit that must be etched away in a subsequent cleaning step. A single 50 second step of forming a hydrogen plasma is effective at reducing fluorine residues, but less effective at reducing particles. A single 60 second step of amorphous silicon deposition, formed by adding silane to a hydrogen plasma process, is effective in reducing fluorine residues. It is due to high hydrogen atom production. However, grain reduction is not as effective as silicon nitride deposition. Again,
It is necessary to remove the amorphous silicon deposit in the subsequent cleaning process.

Another two-step conditioning process using the same length of processing time is also ineffective. A 30 second amorphous silicon deposition plus a 30 second silicon nitride deposition is effective in reducing fluorine residues and particles. However, the added amorphous silicon wall deposition needs to be removed in subsequent cleaning steps.

The multi-step cleaning and conditioning process described above is used in conjunction with the conventional stabilization of the reaction chamber between cleaning steps, and is performed after the fluorine cleaning step and after the silicon nitride deposition step. A nitrogen purge can be used later. It is done in preparation for the subsequent CVD process.

FIG. 2 is a flow chart showing the preferred sequence of steps for the CVD chamber cleaning and conditioning process of the present invention. The plasma CVD chamber is first cleaned with a fluorine-containing gas, a hydrogen plasma is formed in the chamber to remove fluorine residues, a plasma of a silicon compound precursor gas is formed, and a solid silicon compound is deposited inside the chamber. Finally, the chamber is purged with an inert gas before inserting the substrate into which the material is to be deposited.

Although the process has been described with respect to particular embodiments, it will be understood by those of ordinary skill in the art that various changes in gases, reaction conditions, etc. are possible and are included therein. it is obvious.

Further, although specific CVD chambers have been described herein, many CVD chambers are available on the market and can be cleaned and adjusted according to the present process. The invention is limited only by the claims.

[0027]

As described above, according to the present invention, it is possible to effectively remove the fluorine residue and particles, and to perform CVD.
Effective adjustment of the chamber is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view of a PECVD chamber useful for depositing thin films on large area glass substrates.

FIG. 2 is a flow chart illustrating a preferred process step of the present invention.

[Explanation of symbols]

112 ... Housing, 113 ... Vacuum chamber, 116 ...
Susceptor, 120, 121, 122 ... Ceramic liner, 123 ... Annular ring, 132 ... Gas manifold, 192
... face plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michael Corrack, USA, California, Sunnyvale, Pea. Oh. Box 62124 (72) Inventor Anjurley Castle Glen Avenue, San Jose, California, USA 5476 (72) Inventor Takako Takehara United States, California, Hayward, Colony Vue Place 2811 (72) Inventor Gov Jeff Fen United States Bernese Avenue, San Jose, California, 3307 (72) Inventor Kwan Yuan Shan, Johnson Avenue, San Jose, California, USA 1507 (72) Kam S. Inventor. Row United States, California, Union City, Riviera Drive 461

Claims (8)

[Claims] 1. A method of conditioning a chemical vapor deposition chamber after cleaning the chamber and prior to a subsequent deposition step, comprising the steps of: (a) introducing hydrogen into the chamber and then forming a plasma to leave residual fluorine. Reacting with a substance, and (b) flowing a deposition gas mixture into the chamber under reaction conditions so as to deposit a layer of a solid compound on the inner surface of the chamber before the step of depositing on the substrate. And a method. 2. The method of claim 1, wherein the deposition gas mixture comprises silane. 3. The method of claim 2, wherein a nitrogen-containing gas is added to the silane during step (b). 4. The nitrogen-containing gas is ammonia.
The method of claim 3. 5. The method of claim 4, wherein the nitrogen-containing gas additionally comprises nitrogen gas. 6. The method of claim 1, wherein the deposition gas mixture comprises tetraethoxysilane. 7. The method of claim 1, wherein the chamber has been previously cleaned with a fluorine containing gas. 8. The method of claim 7, wherein the fluorine-containing gas is nitrogen trifluoride.