JP2012174922A - Cleaning gas and remote plasma cleaning method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cleaning gas which is used by a remote plasma cleaning method for deposits in a CVD device, and has a low global warming coefficient and a high etching rate, and a remote plasma cleaning method using the same.SOLUTION: There is provided the cleaning gas for removing Si contents, Ge contents, or metal contents deposited in a reaction chamber 1 of the CVD device by the remote plasma cleaning method, the gas being mixed gas containing CFxOy (where (x) is 2 or 4 and (y) is an integer of 1-3 when x=2 or an integer of 1-4 when x=4) and N.

Description

  The present invention relates to a cleaning gas for a CVD apparatus and a remote plasma cleaning method using the same.

In the CVD apparatus, it is necessary to periodically remove unnecessary deposits generated on the inner wall of the reaction chamber and the wafer stage, for example, Si-containing materials, Ge-containing materials, or metal-containing materials. As one of the methods, active F radicals are generated by plasma discharge in the presence of a cleaning gas containing NF ₃ or C ₂ F ₆ to convert the deposit into a highly volatile substance. There is a plasma cleaning method in which the gas is discharged out of the reaction chamber.

  Plasma generation methods in plasma cleaning are roughly classified into two types. One is a system that generates a plasma discharge inside the reaction chamber, such as a parallel plate type plasma generator, and the other is a system that introduces a plasma discharge gas outside the reaction chamber into the reaction chamber. This is called the remote plasma cleaning method.

  In both cases, the optimum method is selected as appropriate according to the specifications of the apparatus, and in particular, the remote plasma cleaning method is used when it is impossible to generate plasma discharge in the chamber, or parallel plate type plasma generation. In the apparatus, it is used when there is a concern about damage to the electrode substrate due to ion bombardment at the time of plasma discharge by a cleaning gas component.

In the remote plasma cleaning method, a cleaning gas diluted with NF ₃ or C ₂ F ₆ is generally used. In particular, NF ₃ is currently most frequently used because of its high etching rate compared to other gases. However, since NF ₃ and C ₂ F ₆ both have a high global warming potential (GWP), there is a drawback that the load on the environment is large.

In recent years, carbonyl difluoride (CF ₂ O) and trifluoromethyl hypofluorite (CF ₃ OF), which have a GWP of 1 as a cleaning gas with a low global warming potential, have been developed, and parallel plate plasma generation A cleaning performance by an apparatus is disclosed (Non-Patent Document 1).

Development of immediate and innovative energy environmental technology Research and development of electronic device manufacturing cleaning system using gas that substitutes for SF6 etc. Result report (March 2003 edition, pages 120-129)

Conventionally, plasma cleaning with a gas having a low environmental impact when discharged into the atmosphere and a low global warming potential has a drawback that the etching rate is inferior to that of using NF ₃ . Therefore, from the viewpoint of suppressing global warming and improving the efficiency of the plasma cleaning process, the plasma cleaning of deposits in the CVD apparatus uses NF ₃ having a low global warming coefficient and a GWP of 17,000. There is a need to develop a cleaning gas that can achieve a high etching rate equivalent to or higher than the above.

  It is an object of the present invention to provide a cleaning gas used in a remote plasma cleaning method that has a low global warming potential and a high etching rate, and a remote plasma cleaning method using the same. .

As a result of extensive studies, the present inventors have found that the cleaning gas has a general formula CF _x O _y having a low global warming potential and having a ketone group or an OF group [where x is 2 or 4, and x = 2 represents an integer of y = 1 to 3, and x = 4 represents an integer of y = 1 to 4. ], It is possible to clean the deposits in the chamber at a high etching rate equivalent to that using NF ₃ by performing remote plasma cleaning using a mixed gas obtained by adding N ₂ to the compound represented by And found the present invention.

That is, in the cleaning gas for removing the Si-containing material, the Ge-containing material, or the metal-containing material deposited in the reaction chamber of the CVD apparatus by a remote plasma cleaning method, the gas is represented by the general formula CF _x O _y [where x Is 2 or 4, and when x = 2, an integer of y = 1 to 3 is represented, and when x = 4, an integer of y = 1 to 4 is represented. A cleaning gas is provided, which is a mixed gas containing N ₂ and a compound represented by the formula:

Further, the compound represented by the general formula CF _x O _y is CF ₃ OF or CF ₂ O, and is represented by the general formula CF _x O _y in the cleaning gas. The cleaning gas, wherein the concentration of the compound is 20 vol% or more and 99.5 vol% or less, and the concentration of N _{2 in} the cleaning gas is 0.5 vol% or more and 80 vol% or less, or the cleaning gas It further provides a cleaning gas characterized in that it contains at least one gas selected from the group consisting of He, Ar, and O ₂ .

  Alternatively, in the remote plasma cleaning method for removing Si-containing material, Ge-containing material, or metal-containing material deposited in the reaction chamber of the CVD apparatus, the above-described cleaning gas is used as the cleaning gas. A cleaning method is provided.

The cleaning gas of the present invention makes it possible to remove unnecessary deposits in the reaction chamber of the CVD apparatus at high speed without using NF ₃ having a high global warming potential in the remote plasma cleaning of the CVD apparatus.

The schematic system diagram of the CVD apparatus used for the test is shown. The relationship between the gas A concentration and the etching rate when the object to be cleaned is SiO ₂ is shown. The relationship between the gas A concentration and the etching rate when the cleaning target is Si is shown.

  What is to be removed in the present invention is a Si-containing material, a Ge-containing material, or a metal-containing material deposited on the inner wall of the reaction chamber of the CVD apparatus. Examples thereof include Si, Si oxide, Si nitride, SiGe, Ge, W, Ti, In, and Ir.

The cleaning gas of the present invention has at least the general formula CF _x O _y [where x is 2 or 4, y is an integer from 1 to 3 when x = 2, and y is an integer from 1 to 4 when x = 4 Represents. ] Are both mixed gases containing compound and N ₂ represented by. Examples of the compound represented by the general formula CF _x O _y include CF ₂ O, CF (OF) O, C (OF) ₂ O when x = ₂ , and CF ₃ when x = 4. OF, CF ₂ (OF) ₂ , CF (OF) ₃ , C (OF) _{4 and the} like.

The concentration of the compound represented by the general formula CF _x O _y in the cleaning gas is preferably 20 vol% or more and 99.5 vol% or less, and more preferably 40 vol% or more and 99.5 vol% or less. It is desirable to obtain a high etching rate. Further, the concentration of N ₂ is preferably 0.5 vol% or more and 80 vol% or less, and preferably 0.5 vol% or more and 60 vol% or less in order to obtain a higher etching rate.

In the cleaning gas, in addition to the compound represented by the general formula CF _x O _y and N ₂ , at least one gas selected from the group consisting of He, Ar, and O ₂ may be mixed. The concentration of at least one gas selected from the group consisting of He, Ar, and O ₂ is not particularly limited, but is not more than the concentration obtained by subtracting the total concentration of the general formula CF _x O _y and N ₂ from the cleaning gas. A gas other than those described above may be contained.

  Next, the remote plasma cleaning method of the present invention will be described.

  The cleaning gas is plasma-discharged by the remote plasma generator via the remote plasma generator connected to the reaction chamber of the CVD apparatus and introduced into the reaction chamber, whereby the inner wall or wafer in the reaction chamber of the CVD apparatus is introduced. The Si-containing material, the Ge-containing material, or the metal-containing material deposited on the stage is removed. This method makes it possible to remove deposits at a high etching rate.

  The pressure in the reaction chamber during cleaning may be a pressure at which stable plasma discharge is obtained when plasma discharge is performed by a remote plasma generator, and is preferably 5 Pa or more and 3000 Pa or less.

  As for the method of introducing the cleaning gas into the remote plasma generator, the cleaning gas adjusted and mixed in advance to a desired composition is supplied to the plasma generation source of the remote plasma generator, and the plasma discharged here is put into the reaction chamber. By supplying, remote plasma cleaning at a high etching rate becomes possible.

By performing remote plasma cleaning using the cleaning gas, it is possible to obtain a high etching rate equivalent to or higher than that of NF ₃ having a high global warming potential.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples.

  FIG. 1 is a schematic system diagram of a CVD apparatus used in this test.

  The flow rate of the cleaning gas is adjusted by a mass flow controller (not shown), and is introduced into the reaction chamber 1 from the gas inlet 5 via the remote plasma generator 6 at a predetermined flow rate.

  The reaction chamber 1 is equipped with a parallel plate type capacitively coupled plasma generator. A high frequency power source 3 is connected to a plate electrode 4 b in the reaction chamber 1, and a ground 9 is connected to a plate electrode 4 a in the reaction chamber 1. ing.

  Further, a pressure gauge 2 for detecting the pressure in the chamber is connected to the reaction chamber 1. Further, an exhaust gas line (not shown) is connected to the discharge port 7 of the reaction chamber 1 in order to discharge gas in the chamber such as volatile products generated by remote plasma cleaning and unreacted gas.

  At the time of remote plasma cleaning, the cleaning gas is introduced from the gas inlet 5 while the discharge of the remote plasma generator 6 is maintained, and the pressure in the chamber is adjusted by adjusting the exhaust amount of the exhaust gas line (at this time) Remote plasma cleaning proceeds with the pressure being the process pressure.

In this test, a test piece 8 made of SiO ₂ or Si material having a thickness of 0.5 mm and an area of 4 cm ² is used as an object to be removed, and the test piece 8 is placed on the flat plate electrode 4a and remote under predetermined conditions. Plasma cleaning was performed. The total flow rate of the introduced cleaning gas is 100 sccm.

The mass of the test piece was measured before and after this test, and the etching rate of SiO ₂ or Si material was calculated by the following calculation formula (1).

[Examples 1 to 20]
In this test, the etching rate of the test piece 8 placed on the parallel electrode 4a was calculated under the cleaning gas composition and cleaning conditions shown in Table 1. In both tests, the cleaning time is 10 minutes. As reference examples, in Examples 1 to 7, 11, 13 to 16, 19, and 20, cleaning was performed in the same manner except that NF ₃ was used as gas A, and the test results (Reference Examples 1 to 14) are shown in Table 2. Show.

In Examples 1 to 6, remote plasma cleaning was performed on a test piece 8 made of SiO ₂ with a binary gas composition of CF ₃ OF and N ₂ at a chamber internal pressure of 53.2 Pa. _CF 3 OF or NF ₃ concentration is performed a cleaning test under the same conditions using a NF _3, both Reference Examples and Examples, a fluorine radical source in place of Reference Example 1-6 In the _CF 3 OF The tendency for the etching rate to decrease with decreasing is similar. The etching rate when CF ₃ OF was used was equal to or higher than that when NF ₃ was used.

From the above, it can be seen that even CF ₃ OF with a small global warming potential has a cleaning performance equivalent to or higher than that of NF ₃ .

A system (Examples 7 to 10) having a cleaning gas composition in which Ar, O ₂ or He is further added in addition to CF ₃ OF and N ₂ , and a system in which the pressure in the chamber during cleaning is changed to 5 Pa, 500 Pa and 3000 Pa ( Examples 11 to 13), a system using Si as a material to be cleaned (Examples 14 to 16), and a system using CF ₂ O instead of CF ₃ OF as gas A (Examples 17 and 18) It can be seen that the results are equivalent to or better than the NF ₃ cleaning results (Reference Examples 1, 8 to 13) when Gas A is replaced with NF ₃ (Reference Example).

[Comparative Examples 1-15]
In this test, remote plasma cleaning was performed by performing the same operation as in the example with the cleaning gas composition and cleaning conditions shown in Table 3 not containing N ₂ . The results are shown in Table 3.

Further, from the above results, a graph of the relationship between the etching rate and the gas A concentration at a process pressure of 53.2 Pa is shown in FIG. 2 for the SiO ₂ cleaning object and in FIG. 3 for the Si cleaning object.

In Comparative Examples 1 to 8, N ₂ added to Examples 1 to 6, 19 and 20 is changed to another gas (O ₂ or Ar) for cleaning, but cleaning containing N ₂ is performed. It can be seen that the etching rate is extremely reduced as compared with the case of gas.

In the examples (Comparative Examples 9 to 11) in which the material to be cleaned was Si (Comparative Examples 9 to 11), the tendency of the etching rate to be extremely reduced was not changed compared to the case of the cleaning gas containing N ₂ . The same was true when the gas A was CF ₂ O (Comparative Example 12).

CF against 3 _OF, by N ₂ to a remote plasma cleaning in gas composition contained a predetermined amount, global warming potential is low CF 3 Again using the _OF of NF ₃ and equivalent to or higher than the etching You can see that cleaning is progressing at speed. Also, when CF ₂ O is used as the gas A, it can be seen that the cleaning is proceeding at the same or higher etching rate as in the case of NF ₃ .

The present invention can be used for cleaning a CVD apparatus, and can be used as an alternative gas for NF ₃ having a high global warming potential, particularly in a remote plasma cleaning method.

DESCRIPTION OF SYMBOLS 1 ... Reaction chamber 2 ... Pressure gauge 3 ... High frequency power supply 4a, 4b ... Flat plate electrode 5 ... Gas introduction port 6 ... Remote plasma generator 7 ... Discharge port 8 ...・ Test specimen 9: Earth

Claims (5)

In a cleaning gas for removing Si-containing material, Ge-containing material, or metal-containing material deposited in a reaction chamber of a CVD apparatus by a remote plasma cleaning method, the gas is a general formula CFxOy [where x is 2 or 4] Yes, an integer of y = 1 to 3 when x = 2, and an integer of y = 1 to 4 when x = 4. A cleaning gas, which is a mixed gas containing N ₂ and a compound represented by the formula: The cleaning gas according to claim 1, wherein the compound represented by the general formula CF _x O _y is CF ₃ OF or CF ₂ O. According to claim 1, wherein the concentration of the formula _CF x _{O y} compound represented by the cleaning gas is less 20 vol% or more 99.5 vol%, and the concentration of _{N 2} in the cleaning gas is 0. A cleaning gas characterized by being 5 vol% or more and 80 vol% or less. The cleaning gas according to claim 1, wherein the cleaning gas further contains at least one gas selected from the group consisting of He, Ar, and O _2. . The cleaning gas according to any one of claims 1 to 4, wherein the cleaning gas is a cleaning gas in a remote plasma cleaning method for removing Si-containing material, Ge-containing material, or metal-containing material deposited in a reaction chamber of a CVD apparatus. A remote plasma cleaning method using the method.

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