JP2006024709A - Method of cleaning chamber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of cleaning a chamber capable of cleaning the inside of the chamber efficiently in a short time by optimizing the kinds and the mixing ratio of gas which are mixed to hexafluoride propene and also by finding out the optimum conditions in cleaning treatment. <P>SOLUTION: Mixed gas of oxygen containing hexafluoride propene of 15-25% is introduced into the chamber so that it may be made to plasma within the chamber. Then, the mixed gas pressure in the chamber is set as 530-933Pa so as to perform a high-pressure cleaning process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a chamber cleaning method, and more particularly, to a method for removing deposits attached to a chamber of a semiconductor manufacturing apparatus for manufacturing a silicon oxide film or the like.

Conventionally, a cleaning process for removing deposits adhering to the chamber has been performed by introducing a gas, mainly a fluorinated gas, into the chamber and turning it into plasma. Although hexafluoroethane has been widely used as the fluorinated gas, it has been proposed to use hexafluoropropene as a cleaning gas as a countermeasure against global warming (see, for example, Patent Document 1).
JP-A-10-27781

Although the above-mentioned patent document describes that a simple gas such as He, Ne, Ar, H ₂ , N ₂ , or O ₂ may be mixed with hexafluoropropene at an appropriate ratio, The mixing ratio and the conditions for the cleaning treatment are not described, and these detailed examinations are not made at all. In particular, hexafluoropropene has a problem that the polymer formation reaction is likely to proceed because it has a double bond in the molecule, and the fluorine radical necessary for cleaning is removed while preventing the polymer formation reaction from occurring. It is necessary to generate efficiently.

  Therefore, the present invention provides a chamber cleaning method capable of efficiently cleaning the inside of the chamber by optimizing the type and mixing ratio of the gas mixed with hexafluoropropene and finding the optimum conditions in the cleaning process. It is intended to provide.

  In order to achieve the above object, the chamber cleaning method of the present invention is characterized in that a gas mixture with oxygen containing 15 to 25% of hexafluoropropene is introduced into the chamber and is plasmatized in the chamber. . Furthermore, it is characterized by including a high-pressure cleaning process in which the pressure of the mixed gas in the chamber is set to 530 to 933 Pa.

  Effective cleaning can be performed by setting the hexafluoropropene concentration in the mixed gas of hexafluoropropene and oxygen to a range of 15 to 25%. In particular, a more effective cleaning process can be performed by increasing the pressure to 530 to 933 Pa during the cleaning process.

  FIG. 1 is a schematic system diagram showing an example of a semiconductor thin film forming apparatus for carrying out the method of the present invention. This semiconductor thin film forming apparatus includes a raw material gas introduction pipe 12, a hexafluoropropene as a cleaning gas, and a hexafluoride propene for introducing oxygen into a chamber 11 having a plasma generating means for applying high frequency and microwaves. An introduction pipe 13 and an oxygen introduction pipe 14 and an exhaust pipe 16 provided with a vacuum pump 15 are provided.

  The thin film is formed by disposing a substrate in the chamber 11, introducing a source gas into the chamber 11 from the source gas introduction pipe 12, and generating a plasma in the chamber 11 by operating a plasma generating means. . The gas in the chamber 11 is sucked into the vacuum pump 15 and discharged from the exhaust pipe 16.

  When cleaning the inside of the chamber 11, the hexafluoropropene and oxygen are respectively introduced at a predetermined flow rate from the hexafluoropropene introduction pipe 13 and the oxygen introduction pipe 14 and introduced into the chamber 11 in a predetermined mixed state. The plasma generating means is operated to generate plasma in the chamber 11. The gas in the chamber 11 at this time is also sucked into the vacuum pump 15 and discharged from the exhaust pipe 16. The mixed gas of hexafluoropropene and oxygen serving as the cleaning gas is adjusted in flow rate by flow rate adjusters 13F and 14F provided in the hexafluoropropene introduction tube 13 and the oxygen introduction tube 14, respectively, and has a predetermined mixing ratio. Alternatively, a mixed gas in a state of being mixed at a preset mixing ratio may be filled in the container and introduced into the chamber 11.

  The mixing ratio of hexafluoropropene and oxygen is optimal when the concentration of hexafluoropropene in the mixed gas is 15 to 25%, and the cleaning effect is lowered both above and below this concentration range.

  The cleaning process is performed in a high-pressure cleaning process performed at a relatively high pressure and a low-pressure cleaning process performed at a relatively low pressure, and the pressure in the low-pressure cleaning process is normally performed around 200 Pa. On the other hand, when the pressure during the high-pressure cleaning process is low, sufficient cleaning cannot be performed. When the pressure is too high, solids such as carbon fluoride, mainly carbon, adhere to the chamber 11. The pressure of 530 to 933 Pa is appropriate.

  Under such conditions, that is, by setting the hexafluoropropene concentration in the mixed gas in the range of 15 to 25% and setting the pressure during the high-pressure cleaning step in the range of 530 to 933 Pa, polymer formation of hexafluoropropene While preventing the reaction from occurring, fluorine radicals that are the most important active species for cleaning in the chamber 11 can be efficiently generated, and the cleaning effect can be improved. The plasma generation conditions can be set in the same manner as in the prior art.

  As a semiconductor thin film forming apparatus, a parallel plate type plasma apparatus for film formation of silicon oxide film using tetraethoxysilane (Applied Materials Co., Ltd .: Precision5000, 5-inch wafer) is used, and after cleaning the silicon oxide film by about 8000A, cleaning is performed. It was. The gas discharged from the chamber during the cleaning process was collected in a Fourier transform infrared spectrometer, and the transition of the amount of silicon tetrafluoride generated by the cleaning process was measured. As basic conditions for the cleaning process, the high frequency applied power was 750 W, the high pressure cleaning time was 45 seconds, the low pressure cleaning was 200 Pa for 25 seconds, and the substrate temperature was 400 ° C.

Comparative Example 1
Cleaning treatment was performed by using a mixed gas of hexafluoroethane and oxygen as a cleaning gas and changing the pressure of high-pressure cleaning and the total flow rate of hexafluoroethane concentration. As a result, it was found that when the cleaning gas was used, good cleaning could be performed in 70 seconds with a high pressure of 467 to 600 Pa, a hexafluoroethane concentration of 45 to 50%, and a total flow rate of 750 sccm or more. .

  Further, when the hexafluoroethane concentration is lowered to 15 to 25%, the cleaning process time becomes longer. When the hexafluoroethane concentration is increased to 55% or higher, or the pressure is increased to 667 Pa or higher, carbon is contained in the chamber. As a result, a solid substance of fluorinated carbon, mainly composed of No. 1, became attached, and good cleaning treatment could not be performed.

Example 1
In the mixed gas system of hexafluoropropene and oxygen, the cleaning process was performed by changing the mixing ratio of gas introduced into the chamber, the total gas flow rate, and the like. FIG. 2 shows the relationship between the concentration of hexafluoropropene in the mixed gas, the flow rate, and the total generation amount of silicon tetrafluoride, and FIG. 3 shows the relationship between the pressure, flow rate, and total generation amount of silicon tetrafluoride in the high-pressure cleaning process. Show. The total amount of silicon tetrafluoride generated is expressed as a relative value with the total amount of silicon tetrafluoride generated when the cleaning process is performed under the optimum conditions in Comparative Example 1 being 100.

  As is apparent from FIGS. 2 and 3, in the cleaning with a mixed gas of hexafluoropropene and oxygen, the concentration of hexafluoropropene is in the range of 15 to 25%, and the pressure during high pressure cleaning is in the range of 530 to 933 Pa. It can be seen that a good cleaning process can be performed. Further, it is understood that the total flow rate of the mixed gas is optimal in the range of 300 to 800 sccm, particularly 450 to 600 sccm in the case of the apparatus used in this example. The treatment time at this time was about 70 seconds, which is substantially the same as when hexafluoroethane was used.

  Thus, since the molecular structure and chemical reactivity of hexafluoroethane and hexafluoropropene differ greatly, the optimum conditions for hexafluoroethane cannot be applied to hexafluoropropene as they are. In the case of using propylene fluoride, it can be seen that a good cleaning process can be performed when the flow rate is low and the pressure is high compared to hexafluoroethane.

  In addition, when the mixing ratio of hexafluoropropene and oxygen and the working pressure are optimized, even if nitrogen, nitrous oxide, argon, and helium are added up to 10% of the total flow rate, the cleaning characteristics can be improved. There wasn't.

Example 2
Under the conditions derived in Example 1, thin film generation and cleaning were repeated 100 times, and it was confirmed that no residue remained in the chamber. As a result, it was found that no film formation residue was observed in the chamber and normal cleaning was performed. Moreover, although the film thickness uniformity of the produced thin film was compared with the case of using the hexafluoroethane of Comparative Example 1, the film thickness uniformity was not changed from an average of 1.5 and was derived in Example 1. It can be seen that if hexafluoropropene is used under the conditions, the same level of cleaning performance as when hexafluoroethane is used can be obtained.

It is a schematic system diagram which shows an example of the semiconductor thin film formation apparatus for enforcing the method of this invention. It is a figure which shows the relationship between the hexafluoride propene density | concentration in mixed gas, a flow volume, and the generation amount of silicon tetrafluoride. It is a figure which shows the relationship between the pressure and flow volume in a high-pressure cleaning process, and the generation amount of silicon tetrafluoride.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Chamber, 12 ... Source gas introduction pipe, 13 ... Hexafluoropropene introduction pipe, 14 ... Oxygen introduction pipe, 15 ... Vacuum pump, 16 ... Exhaust pipe

Claims (2)

  A method for cleaning a chamber, comprising introducing a mixed gas of oxygen containing 15 to 25% of hexafluoropropene into oxygen into the chamber and generating plasma in the chamber.   The chamber cleaning method according to claim 1, further comprising a high-pressure cleaning step in which a pressure of the mixed gas in the chamber is set to 530 to 933 Pa.

Images