JP2003007620A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method by which the exchanging frequency of the substrate placing section of a plasma enhanced CVD system can be reduced, by prolonging the service life of the section. SOLUTION: Before cleaning the substrate placing section, a protective film (SiN film), against plasma etching performed at cleaning of the section, is formed on the surface of the section. Alternatively, a high-quality protective film, having a higher resistance against plasma etching than protective films formed in the other sections than the substrate placing section have, is formed on the surface of the substrate placing section, by causing the section to have higher temperature suitable for forming the protective film than the other sections have, by impressing a bias voltage on the section or heating the section. At performing of the plasma etching, in addition, the film thicknesses of the protective film formed on the surface of the substrate placing section and protective films and insulation films formed in the other sections are set, so that the etching time of the protectively film may become equal to the etching time of the protective and insulation films.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cleaning method in a plasma CVD apparatus.

[0002]

2. Description of the Related Art Plasma C is currently used in semiconductor manufacturing.
Film formation using a VD (Chemical Vapor Deposition) apparatus is known. A plasma CVD apparatus supplies a gas that is a raw material of a film into a container (deposition chamber) to form a plasma state, and a chemical reaction on a surface of a substrate (wafer) by active particles (excited atoms or molecules) in the plasma. Is a device for promoting film formation. The container is provided with an electromagnetic wave transmission window, and by supplying electric power from a high frequency power source to a power feeding antenna arranged outside the container to cause the electromagnetic wave to enter the deposition chamber through the electromagnetic wave transmission window, the energy of the electromagnetic wave (high frequency Power) to bring the gas in the film forming chamber into a plasma state.

In such a plasma CVD apparatus, an S oxide film is used as an insulating film for insulating between elements and wiring.
When forming an iO _x film (SiO ₂ film or the like) on a substrate,
For example, SiH ₄ and O ₂ are used as the insulating film forming gas. In this case, since the SiO _x film is also formed on the inner surface of the film forming chamber when the SiO _x film forming process is performed on the substrate, after the film forming process, fluoride such as NF ₃ is fluorinated in the film forming chamber. By supplying a gas and making it into a plasma state with a high frequency power, the SiO _x film adhering to the inner surface of the film forming chamber is removed by plasma etching (chemical etching) (cleaning).

[0004]

However, in the above-mentioned conventional cleaning method, when cleaning the film forming chamber by plasma etching with a fluorinated gas, the substrate mounting portion (AlN, Al ₂ O _3, etc.) on which the substrate is mounted is mounted. (Electrostatic chuck made of ceramic material) is also etched and damaged. For this reason, it is necessary to frequently replace the substrate mounting portion (electrostatic chuck), but since this substrate mounting portion (electrostatic chuck) is expensive and it takes time to replace it, It has been desired to extend the service life of parts and reduce the frequency of replacement as much as possible.

Therefore, in view of the above circumstances, it is an object of the present invention to provide a cleaning method capable of extending the life of the substrate mounting portion of the plasma CVD apparatus and reducing the replacement frequency thereof.

[0006]

[Means for Solving the Problems] First to solve the above problems
According to a cleaning method of the invention, when a predetermined film is formed on a substrate in a film forming chamber of a plasma CVD apparatus, the film attached to a portion other than the substrate in the film forming chamber is cleaned with a cleaning gas in the film forming chamber. In a cleaning method in which the substrate is supplied to be in a plasma state and is removed by chemical etching using the plasma, a gas for forming a protective film is supplied to the film forming chamber to bring the substrate into a plasma state before cleaning so that the substrate is mounted. A protective film against plasma etching at the time of cleaning is formed on the surface of the substrate mounting portion.

The cleaning method of the second invention is the cleaning method of the first invention, wherein the predetermined film is an insulating film, the protective film is a SiN film, and the etching gas is a fluorinated gas. .

The cleaning method of the third invention is the cleaning method of the second invention, wherein SiH ₄ and N ₂ are used as a protective film forming gas for forming the SiN film.
Alternatively, NH ₃ is used.

A cleaning method according to a fourth aspect of the present invention is the cleaning method according to the first, second or third aspect of the present invention, in which a bias is applied to the substrate mounting portion so that a portion other than the substrate mounting portion in the film forming chamber is not included. A high-quality protective film having a higher resistance to the plasma etching than the protective film formed on the portion is formed on the surface of the substrate mounting portion.

The cleaning method of the fifth aspect of the present invention is the cleaning method of the first, second or third aspect of the present invention, wherein the substrate mounting portion is heated and the surface temperature of the substrate mounting portion is adjusted to the film forming chamber. Than the temperature of the portion other than the substrate mounting portion of the, by making the temperature suitable for forming the protective film, than the protective film formed in the portion other than the substrate mounting portion in the film forming chamber,
A high-quality protective film having high resistance to the plasma etching is formed on the surface of the substrate mounting portion.

A cleaning method according to a sixth aspect of the present invention is the cleaning method according to the fourth or fifth aspect of the invention, wherein during the plasma etching, the etching time of the protective film formed on the surface of the substrate mounting portion and the film formation are performed. It is characterized in that the film thicknesses of the protective film and the predetermined film formed on the portion other than the substrate mounting portion in the chamber are set to be equal to each other.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram of a plasma CVD apparatus for carrying out a cleaning method according to an embodiment of the present invention, and FIG.
Is a flowchart showing the procedure of the cleaning method,
3, 4 and 5 are explanatory views showing the procedure of the cleaning method. Further, FIG. 6A is a graph showing an outline of the etching rate regarding the film forming temperature, and FIG. 6B is a graph showing an outline of the etching rate regarding the bias.

As shown in FIG. 1, a cylindrical vacuum chamber container 2 made of aluminum is provided on the base 1, and the inside of the container 2 serves as a film forming chamber 3. A circular ceiling plate 4 serving as an electromagnetic wave transmission window is provided above the film forming chamber 3, and a substrate support 5 is provided inside the film forming chamber 3.
The substrate support base 5 has a disk-shaped substrate mounting portion 7 for mounting the substrate 6 of the semiconductor element, and the substrate mounting portion 7 is supported by the support shaft 8. The substrate mounting portion 7 is made of Al ₂ O ₃ or Al.
The electrostatic chuck is made of a ceramic material such as N and electrostatically attracts and holds the substrate 6 placed on the substrate placing portion 7.

The substrate 6 is a disk-shaped Si wafer, and as is well known, it has a diameter of 150 mm (6 inches) or a diameter of 200 m.
There are various sizes such as m (8 inches).
A bias power supply 1 is provided on the substrate mounting portion 7 via a matching device 20 and a capacitor 9 for impedance matching.
0 is connected. That is, the substrate platform 7 also functions as a bias electrode. In addition, LP is placed on the substrate mounting portion 7.
The electrostatic power source 12 is also connected via F11.

Therefore, when the high frequency power is supplied from the bias power source 10, the high frequency bias is applied to the substrate mounting portion 7 and the substrate 6. The bias power at this time is appropriately adjusted by the bias power supply 10. Further, DC power is supplied from the electrostatic power source 12, and the substrate 6 is attracted to the substrate mounting portion 7 by the electrostatic force generated in the substrate mounting portion 7 by this. It should be noted that the substrate support base 5 can be raised and lowered as a whole or the support shaft 8 can be expanded and contracted to make the substrate 6
The vertical height of the can be adjusted to the optimum height.

Further, the substrate mounting portion 7 is provided with a heater 13 as a heating means. Heater 13 is heater power supply 1
4 is connected to the heater power source 14 and the heater 1
By adjusting the electric power supplied to the substrate 3, the film forming temperatures of the substrate mounting portion 7 and the substrate 6 are appropriately adjusted. The heating means is not necessarily limited to the heater 13. For example, a fluid such as a gas may be supplied to the substrate placement portion 7 and the temperature of the fluid such as the gas may be adjusted to adjust the substrate placement portion. The film forming temperature of 7 or the substrate 6 may be adjusted appropriately.

An exhaust port 15 is provided in the base 1,
By exhausting the gas in the film forming chamber 3 to a vacuum exhaust system (not shown) through the exhaust port 15, the inside of the film forming chamber 3 has a low pressure environment, and film formation and cleaning are performed under this low pressure environment. Various gases for performing are supplied (details will be described later).
The container 2 (film forming chamber 3) is provided with a loading / unloading port (not shown) for the substrate 6 so that the substrate 6 can be loaded and unloaded from / to a transport chamber (not shown).

A spiral feeding antenna 16 is installed on the ceiling plate 4, and a high frequency power supply 17 is connected to the feeding antenna 16 via a matching device 19 for impedance matching. Therefore, by supplying high frequency power from the high frequency power supply 17 to the power feeding antenna 16, the electromagnetic wave 18 is made incident from the power feeding antenna 16 into the film forming chamber 3 through the ceiling plate 4, and the electromagnetic wave 18 is generated.
The various gases supplied into the film forming chamber 3 by the above energy (high frequency power) are brought into a plasma state.

Further, the container 2 may be a gas supply system (not shown).
Various gases sent from the above are introduced into the film forming chamber 3.
Nozzles 21, 22, 23, and 24 are provided.
O from the nozzle 21 as an oxidizing gas₂Gas is supplied
It The supply amount of this oxidizing gas is MFC (Mass Flow Control
ller) 25. N as the oxidizing gas ₂
O gas or the like may be used. MFC 26 from the nozzle 22
Flow rate adjusted SiH_FourGas is supplied. This
SiH_FourGas is O₂SiO with gas_xMembrane (insulation
It becomes the raw material of the film). N as oxidizing gas₂When O is used
Is SiO_xN_YA film is formed. In addition, SiO_xMembrane
SiO_xN_YThe source gas for the film is not necessarily SiH_Four
However, other gases including Si can be used.
Good.

From the nozzle 23, N ₂ gas whose flow rate is adjusted by the MFC 27 is supplied. This N ₂ gas is Si
It becomes a raw material for the SiN film (protective film) together with H ₄ gas. NF ₃ gas is supplied from the nozzle 24 as a cleaning gas (plasma etching gas). The supply amount of this NF ₃ gas is adjusted by the MFC 28. Other fluoride gas may be used as the cleaning gas.

Note that the nozzles 21, 22, 23, 24 may be appropriately shared, and the nozzles 21, 22, 23, 24,
The vertical position of 24 and the like may be changed as appropriate.

In the controller 30 equipped with a microcomputer, the details of which will be described later, but the ON / OF of the MFCs 25, 26, 27, 28 are based on a predetermined control sequence.
By performing F control, the supply timing of various gases is controlled, and the high frequency power supply 17, bias power supply 10,
The heater power supply 14 and the electrostatic power supply 12 are ON / OFF controlled to control the power supply timing of these power supplies.

The flow of processing carried out by the plasma CVD apparatus will be described with reference to FIGS. 2, 3, 4, 5 and 6.

As shown in FIG. 2, in the plasma CVD apparatus, first, a SiN film forming process for forming a SiN film (protective film) on the substrate mounting portion 7 is performed (step S1). The thickness of the SiN film at this time is, for example, 1 μm or less (the optimum film thickness condition will be described later). After that, Si on the substrate 6
A SiO _x film forming process for forming an O _x film (insulating film) is performed (step S2). The thickness of the SiO _x film at this time is, eg, 10 μm or more. After the SiO _x film forming process is completed, a cleaning process for removing the SiO _x film attached to the inner surface of the film forming chamber 3 is performed (step S).
3). After that, similarly, the processes of steps S1 to S3 are repeated. These processes will be further described with reference to FIGS.

First, in the SiN film forming process shown in FIG. 3, a high frequency power from the high frequency power supply 17 is supplied by supplying SiH ₄ gas or N ₂ gas as a protective film forming gas from the nozzles 22 and 23 into the film forming chamber 3. A SiN film (protective film) 41 is formed on the surface of the substrate mounting portion 7 by turning it into a plasma state with power. At this time, the SiN film 42 is simultaneously formed on the inner surface of the film forming chamber 3.

At this time, the bias power source 10 applies a bias of, for example, 100 W to the substrate mounting portion 7, so that the SiN film 42 formed on the inner surface of the film forming chamber 3 is more fluorinated in the cleaning process. Gas (N
A high-quality SiN film 41 having high resistance to plasma etching by F ₃ or the like) is formed on the surface of the substrate mounting portion 7. Alternatively, the substrate mounting portion 7 is heated by a heating means such as the heater 13 so that the surface temperature of the substrate mounting portion 7 is lower than the inner surface temperature of the film forming chamber 3 (for example, 200 ° C. or lower) by the SiN film (protective film). ), The SiN film 4 formed on the inner surface of the film forming chamber 3 is heated to a high temperature (for example, 350 ° C.).
A high-quality SiN film 41 having a higher resistance to the plasma etching than that of No. 2 is formed on the surface of the substrate mounting portion 7. That is, by applying a bias or raising the film forming temperature, a film quality difference is caused between the SiN film 41 and the SiN film 42.

After that, in the SiO _x film forming step shown in FIG. 4, O ₂ gas, SiH ₄ gas or the like is supplied as the SiO _x film forming gas into the film forming chamber 3 from the nozzles 21 and 22, and the high frequency power source 17 supplies the gas. By forming a plasma state with high-frequency power, a SiO _x film 43 such as a SiO ₂ film is formed on the substrate 6 as an insulating film that insulates elements and wiring from each other.
At this time, the SiO _x film 44 is simultaneously formed on the inner surface of the film forming chamber 3. Also in this case, as in the case of forming the SiN film, a good-quality S is formed on the substrate 6 by applying a bias from the bias power source 10 and heating by a heating means such as the heater 13.
An iO _x film 43 is formed, and SiO _x is formed on the inner surface of the film forming chamber 3.
A SiO _x film 44 having a poorer film quality than the film 43 is formed.

After the SiO _x film forming process is completed,
In the cleaning process shown in FIG. 5, after the substrate 6 is moved from the substrate platform 7 and carried out of the film forming chamber 3, a fluorinated gas such as NF ₃ is supplied from the nozzle 24 into the film forming chamber 3 as a cleaning gas. Of the SiO _x film 44 and the SiN film 42 adhering to the inner surface of the film forming chamber 3 by plasma etching (chemical etching) to remove (clean) them. .

At the same time, the SiN film 41 formed on the surface of the substrate mounting portion 7 is also plasma-etched.
That is, since the surface of the substrate mounting portion 7 is protected from the plasma etching during cleaning by the SiN film 41, it is possible to prevent the surface of the substrate mounting portion 7 from being directly plasma-etched and damaged. Therefore, it is possible to extend the life of the substrate platform 7 and reduce the frequency of replacement.

Further, in this case, it is desirable that the SiN film 41 remains until the cleaning process is completed (until the SiO _x film 44 and the SiN film 42 are removed), but the SiN film 41 is excessively thickened. And extra SiN
It takes a long time and energy to form a film, which causes a decrease in efficiency, and the SiN film 4 is formed every time the SiN film forming process is repeated.
Since 1 is accumulated, the film thickness condition of the SiN film (protective film) is shown in FIG.
It is most desirable that the relation of equations such as

That is, the S formed on the surface of the substrate mounting portion 7
Etching time of the iN film (protective film) 41 (SiN film 41
Is removed by plasma etching)
And the SiN film 42 and Si formed on the inner surface of the film forming chamber 3.
The film thicknesses of these films 41, 42, and 44 are set so that the etching time of the O _x film 44 (the time during which all of these films 42 and 44 are removed by plasma etching) is equal. Specifically, the thickness of the SiO _x film 44 is Si
Since it is determined in accordance with the formation of the SiN film 43 having a predetermined thickness in the O _x film forming process, the film thickness of the SiN film 41 is appropriately adjusted so that the above equation is satisfied.

For example, as shown in FIGS. 6 (a) and 6 (b) for reference, the outline of the HF etching rate is shown as follows.
The etching rate of the film largely depends on the film forming temperature and the bias power (the vertical axis in the figure is a logarithmic scale), and the higher the film forming temperature and the larger the bias power, the smaller the film etching rate. That is, the higher the deposition temperature of the SiN film,
The higher the bias power, the better the film quality, and the more difficult it is to be etched by the fluorinated gas plasma. This also applies to the SiO _x film.

Therefore, if the film thickness of the SiN film 41 is selected to be an appropriate film thickness, it is possible to set the film thickness so as to satisfy the relation of the above equation. For example, the film thickness of the SiN film 41 is 0.8 μ
m, the thickness of the SiN film 42 is 0.8 μm, and the SiO _x film 44 is
The film thickness is set to 10 μm. Then, by setting the film thickness so as to satisfy the relationship of the above equation,
It is possible to reliably protect the surface of the substrate platform 7 from the plasma etching during cleaning without forming an additional SiN film 41 on the surface of the substrate platform 7.

Although the case where the substrate mounting portion (electrostatic chuck) 7 made of ceramic such as Al ₂ O ₃ or AlN is protected by the protective film (SiN film) has been described above, the invention is not limited to this. Instead, the present invention can be applied to a substrate mounting portion using another material such as SiC. In the case of a substrate mounting part using metal, a bias cannot be applied, and therefore a means of increasing the film forming temperature is adopted.

In the above description, the case of removing (cleaning) the insulating film (SiO _x film) attached to the inner surface of the film forming chamber 3 has been described. However, the present invention is not limited to this, and If there is a portion where the insulating film is to be removed (a portion other than the substrate mounting portion) other than the inner surface thereof, the present invention can also be applied to the removal of the insulating film at that portion.

In the above, the SiN film forming process is performed before the SiO _x film forming process. However, the present invention is not limited to this, and the cleaning process after the SiO _x film forming process is completed. Before that, the SiN film forming treatment step may be performed.

[0038]

As described above in detail with the embodiments of the invention, the cleaning method of the first invention is performed when the predetermined film is formed on the substrate in the film forming chamber of the plasma CVD apparatus. In the cleaning method of removing the film adhering to a portion other than the substrate in the film chamber by supplying a cleaning gas into the film forming chamber to a plasma state and removing the film by chemical etching by the plasma, the film formation before cleaning. A protective film for plasma etching at the time of cleaning is formed on the surface of the substrate mounting portion on which the substrate is mounted by supplying a protective film forming gas to the chamber to bring it into a plasma state.

The cleaning method of the second invention is the cleaning method of the first invention, wherein the predetermined film is an insulating film, the protective film is a SiN film, and the etching gas is a fluorinated gas. .

The cleaning method of the third invention is the cleaning method of the second invention, wherein SiH ₄ and N ₂ are used as a protective film forming gas for forming the SiN film.
Alternatively, NH ₃ is used.

Therefore, according to the cleaning method of the first, second or third invention, since the surface of the substrate mounting portion is protected from the plasma etching during cleaning by the protective film, the surface of the substrate mounting portion is protected. Can be prevented from being directly plasma-etched and damaged. For this reason, it is possible to extend the life of the substrate mounting portion and reduce the frequency of replacement thereof.

The cleaning method according to the fourth aspect of the present invention is the cleaning method according to the first, second or third aspect of the present invention, in which a bias is applied to the substrate mounting portion so that a portion other than the substrate mounting portion in the film forming chamber is not exposed. A high-quality protective film having a higher resistance to the plasma etching than the protective film formed on the portion is formed on the surface of the substrate mounting portion.

The cleaning method of the fifth aspect of the present invention is the cleaning method of the first, second or third aspect of the present invention, wherein the substrate mounting portion is heated and the surface temperature of the substrate mounting portion is adjusted to the film forming chamber. Than the temperature of the portion other than the substrate mounting portion of the, by making the temperature suitable for forming the protective film, than the protective film formed in the portion other than the substrate mounting portion in the film forming chamber,
A high-quality protective film having high resistance to the plasma etching is formed on the surface of the substrate mounting portion.

Therefore, according to the cleaning method of the fourth or fifth aspect of the invention, the protective film formed on the substrate mounting portion,
Since a film quality difference occurs between the protective film formed on the portion other than the substrate mounting portion, the surface of the substrate mounting portion can be more reliably protected from plasma etching during cleaning by the protective film.

The cleaning method according to the sixth invention is the cleaning method according to the fourth or fifth invention, wherein during the plasma etching, the etching time of the protective film formed on the surface of the substrate mounting portion and the film formation. It is characterized in that the film thicknesses of the protective film and the predetermined film formed on the portion other than the substrate mounting portion in the chamber are set to be equal to each other.

Therefore, according to the cleaning method of the sixth aspect of the present invention, the surface of the substrate mounting portion is reliably protected from the plasma etching during cleaning without forming an additional protective film on the surface of the substrate mounting portion. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a plasma CVD apparatus that carries out a cleaning method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of the cleaning method.

FIG. 3 is an explanatory diagram showing a procedure of the cleaning method.

FIG. 4 is an explanatory diagram showing a procedure of the cleaning method.

FIG. 5 is an explanatory diagram showing a procedure of the cleaning method.

FIG. 6A is a graph showing an outline of an etching rate regarding a film forming temperature, and FIG. 6B is a graph showing an outline of an etching rate regarding a bias.

[Explanation of symbols]

1 Base 2 Container 3 Film Forming Chamber 4 Ceiling Board 5 Substrate Support 6 Substrate 7 Substrate Placement 8 Support Shaft 9 Capacitor 10 Bias Power Supply 11 LPF 12 Electrostatic Power Supply 14 Heater Power Supply 15 Exhaust Port 16 Power Supply Antenna 17 High Frequency Power Supply 18 Electromagnetic Wave 19, 20 Matching device 21, 22, 23, 24 Nozzle 25, 26, 27, 28 MFC 30 Controller 41 SiN film 42 SiN film 43 SiO _x film 44 SiO _x film

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4K030 DA06 FA01 LA15                 4K057 DA02 DD01 DE06 DM01 DM35                 5F045 AA08 AB32 AB33 AC01 AC02                       AC11 AC12 DP04 EB06 EC05                       EH02 EH11 EH20 EK07 EK30                       EM05 EM09 EM10 GB09 GB15                       HA13

Claims (6)

[Claims] 1. A cleaning gas is supplied into the film forming chamber for depositing the film that adheres to a portion other than the substrate in the film forming chamber when a predetermined film is formed on the substrate in a film forming chamber of a plasma CVD apparatus. In a cleaning method in which the substrate is placed in a plasma state and is removed by chemical etching using this plasma, the substrate is placed by supplying a protective film forming gas to the film forming chamber before the cleaning to bring the substrate into a plasma state. A cleaning method, which comprises forming a protective film against plasma etching during cleaning on the surface of the substrate mounting portion. 2. The cleaning method according to claim 1, wherein the predetermined film is an insulating film, the protective film is a SiN film, and the etching gas is a fluoride gas. 3. The cleaning method according to claim 2, wherein SiH ₄ and N ₂ or NH ₃ are used as a protective film forming gas for forming the SiN film. 4. The cleaning method according to claim 1, 2, or 3, wherein a bias is applied to the substrate mounting portion to form a protective film on a portion other than the substrate mounting portion in the film forming chamber. The method for cleaning is characterized in that a high-quality protective film having higher resistance to the plasma etching is formed on the surface of the substrate mounting portion. 5. The cleaning method according to claim 1, 2, or 3, wherein the substrate mounting portion is heated to adjust a surface temperature of the substrate mounting portion to a portion other than the substrate mounting portion in the film forming chamber. Than the temperature of
By applying a high temperature suitable for forming the protective film, a high-quality protective film having higher resistance to the plasma etching than the protective film formed in the portion other than the substrate mounting portion in the film forming chamber can be formed on the substrate. A cleaning method characterized in that it is formed on the surface of the placing portion. 6. The cleaning method according to claim 4 or 5, wherein during the plasma etching, an etching time of a protective film formed on a surface of the substrate mounting portion and a portion other than the substrate mounting portion in the film forming chamber are excluded. A method of cleaning, wherein the film thicknesses of the protective film and the predetermined film formed in the area are set so that they are equal in etching time.