Patent Application
20090269506
The present invention relates to a method for cleaning a process chamber of a reactor. More specifically, the present invention relates to remote plasma cleaning of a process chamber of a chemical vapor deposition (CVD) reactor.
In the semiconductor industry, selected materials are deposited on a target substrate to produce electronic components. The various deposition techniques employed in the industry include chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and the like. In the CVD process, vaporized gaseous reactants are introduced into a process chamber and result in the formation of films on the target substrate. During the deposition process, unwanted films and particulate materials accumulate on surfaces other than the target substrate. The unwanted films and particulate materials may accumulate on the walls of the process chamber, susceptor, and on other employed equipment. These unwanted films and particulate materials can change the surface characteristics of the process chamber. Further, the unwanted films and particulate materials can flake off from the walls of the process chamber and get deposited on the wafers, causing defects on their surfaces. Therefore, the process chamber needs to be cleaned at regular intervals to ensure proper functioning of the deposition process.
The unwanted films and particulate materials deposited in the process chamber can be removed by plasma cleaning. This involves reacting a reactive species with the unwanted films and particulate materials to generate volatile products. Thereafter, the volatile products are removed from the process chamber. Plasma cleaning can be of two types—remote plasma cleaning and in situ plasma cleaning. In in situ plasma cleaning, the plasma is generated inside the CVD reactor, but in remote plasma cleaning it is generated outside the CVD reactor. Remote plasma cleaning has distinct advantages over in situ plasma cleaning. For example, there is reduced CVD reactor damage, greater feed gas destruction efficiency, a shorter clean time, etc. Therefore, remote plasma cleaning is the preferred method for cleaning the process chamber of the CVD reactor. In the CVD process, the reactive species are supplied to the process chamber through holes of a shower plate. However, a large part of the reactive species formed in a remote plasma generator recombines into an inert form by the time they reach the process chamber. Therefore, a substantial portion of the reactive species is wasted, resulting in low utilization and cleaning efficiency and non-uniform cleaning. Therefore, the CVD reactor needs to be well maintained on a more regular basis in the case of low cleaning efficiency to get the desired quality of films. This results in increased downtime of the reactor.
Accordingly, there is a need for a process and an apparatus that enhances the utilization efficiency of the reactive species. The apparatus and the method should have high cleaning efficiency to clean the process chamber of the CVD reactor. Further, the apparatus and the method should feed the reactive species uniformly into the process chamber. Furthermore, the apparatus and the method should be able to control the flow rate of the reactive species.
An object of the present invention is to provide a process and an apparatus for efficient and uniform remote plasma cleaning of a process chamber of a chemical vapor deposition (CVD) reactor.
Another object of the present invention is to provide a process and an apparatus that enables high utilization efficiency of the reactive species.
Yet another object of the present invention is to provide a process and an apparatus that can control the flow rate of the reactive species.
To achieve the objects mentioned above, the present invention provides a process and an apparatus that includes supplying the reactive species into the process chamber of the CVD reactor through a plurality of inlet holes. The plurality of inlet holes is located on a ring-shaped first body. The reactive species are generated in a remote plasma unit and are supplied to the process chamber through a first conduit. The first conduit connects the remote plasma unit to the first body. The reactive species are introduced into the process chamber via the plurality of inlet holes. This ensures the high utilization efficiency of the reactive species and uniform cleaning of the process chamber. Further, the flow rate of the reactive species can be controlled by inserting one or more parts into one or more of the plurality of inlet holes of the first body or by changing the flow rate of a cleaning gas. The reactive species react with unwanted deposited films in the process chamber and produce volatile products that are then exhausted from the process chamber.
The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the invention, wherein like designations denote like elements, and in which:
The present invention provides a process and an apparatus for uniform and efficient remote plasma cleaning of a process chamber of a chemical vapor deposition (CVD) reactor. A remote plasma unit is coupled with the CVD reactor. Reactive species are generated in the remote plasma unit and are supplied to the process chamber of the CVD reactor through a plurality of inlet holes. The plurality of inlet holes is located on a ring-shaped first body.
The reactive species used in remote plasma cleaning are free radicals and are generated in remote plasma unit 102. In various embodiments of the present invention, the reactive species may be fluorine radicals, oxygen radicals, and the like. The reactive species are generated from a cleaning gas, which is supplied to remote plasma unit 102 through cleaning gas inlet 104. In an embodiment of the invention, the cleaning gas is a mixture of oxygen, a rare gas such as Ar, and an additive gas such as N2 gas. In an embodiment of the invention, the flow rate of oxygen gas may be set at 15,000 sccm, the flow rate of Ar gas may be set at 2, 500 sccm, and the flow rate of N2 gas may be set at 800 sccm. In various embodiments of the invention, the flow rate of oxygen may be set in the range of 2,000 to 20,000 sccm, the flow rate of Ar may be set in the range of 1,000 to 15,000 sccm and the flow rate of N2 gas may be set in the range of 0 to 3,000 sccm.
In another embodiment of the invention, the cleaning gas may be a carbon- and fluorine-containing gas or a mixture of oxygen, and a carbon- and fluorine-containing gas. In various embodiment of the invention, the carbon- and fluorine-containing gas may be Tetrafluoromethane (CF4), Hexafluoroethane (C2F6), Octafluoropropane (C3F8), Octafluorocyclobutane (C4F8), Carbonyl fluoride (COF2), and the like. In another embodiment of the invention, the cleaning gas may be Nitrogen trifluoride (NF3) gas or a mixture of oxygen and Nitrogen trifluoride (NF3) gas.
The preliminary plasma is struck by introducing an inert gas into remote plasma unit 102. Thereafter, the cleaning gas is introduced into remote plasma unit 102 and the reactive species are generated from the cleaning gas. In an embodiment of the present invention, the inert gas may be argon, and plasma is struck by an inductively coupled plasma (ICP) source. The reactive species are generated by activation of the cleaning gas molecules. In an embodiment of the present invention, the power supplied to maintain the plasma in remote plasma unit 102 may be at least 2,000 W.
The reactive species are supplied to first body 108 through first conduit 106. In an embodiment of the invention, remote plasma unit 102 has one outlet for supplying the reactive species. First conduit 106 connects remote plasma unit 102 to first body 108. In an embodiment of the present invention, first body 108 is a ring-shaped body. First body 108 has a plurality of inlet holes 110 for supplying the reactive species to the process chamber. In accordance with the first embodiment of the invention, first conduit 106 connects remote plasma unit 102 to first body 108 through second body 112. First body 108 is detachably mounted onto second body 112. Second body 112 provides a casing for the vacuum process chamber.
The reactive species react with the unwanted residue in the process chamber and generate volatile products. These volatile products are exhausted from the process chamber by exhaust line 114. The pressure inside the CVD reactor may be set in accordance with the area that is to be cleaned. In an embodiment of the invention, the pressure inside the CVD reactor is 533 Pa and the cleaning rate is greater than 1000 nm/minute. In various embodiments of the invention, the pressure inside the CVD reactor is in the range of 100 to 1300 Pa.
Second conduit 116 supplies a process gas to the process chamber. In an embodiment of the invention, the process gas is a hydrocarbon like cyclopentene and is supplied to the reactor at a rate of about 350 sccm. In this embodiment, additive gases may be Argon and Helium gas and are supplied to the reactor at a rate of 1,700 sccm and 1,300 sccm respectively. As a result, a carbon film is formed on a substrate. Insulator 118 is attached to upper body 120 to prevent RF transfer from the process chamber. Insulator 118 is made of ceramic material. Upper body 120 is placed over second body 112. Thus, second conduit 116 supplies process gas to the process chamber through upper body 120. The process gas is introduced into the process chamber through a plurality of holes of shower plate 122. In an embodiment of the invention, the size (diameter) of shower plate 122 is 0.350 mm and is set at a temperature range of 100 to 200 centigrade. The process chamber has susceptor 124 for holding a substrate. In an embodiment of the invention, the size (diameter) of the substrate is 0.300 mm and the distance between shower plate 122 and susceptor 124 is in the range of 1 to 50 mm. In various embodiment of the invention, susceptor 124 may be set at a temperature range of 150 to 600 centigrade. Radio frequency generator 126 provides power for generating plasma from the process gas. Radio frequency generator 126 is integrated with the process chamber.
In accordance with the second embodiment of the invention, first conduit 106 is connected to an upper part of first body 108 directly and not through second body 112. The process chamber can be cleaned in accordance with the second embodiment of the invention under the process conditions as described in the first embodiment of the invention.
Second conduit 116 supplies the process gas to inner pipe 502. The process gas is supplied through the vertical passage 504 of inner pipe 502 to first plate 506. First plate 506 distributes the process gas uniformly to shower plate 122. Shower plate 122 supplies the process gas to the process chamber. The reactive species are supplied through outer pipe 508 and pass through the vertical passage 510 of the outer pipe 508. Second plate 512 changes the direction of the flow of the reactive species and is attached to the upper portion of first plate 506. The reactive species generate heat at the contact point between second plate 512 and inner pipe 502. Therefore, third plate 514 is mounted on second plate 512 to prevent heat breakage of second plate 512. Inner pipe 502, second plate 512 and third plate 514 are made of a metal or a ceramic material. In an embodiment of the invention, the ceramic material may include aluminum nitride (AlN) ceramics, aluminum oxide (AL2O3) ceramics, sapphire glass, and the like. The reactive species are introduced into the process chamber through plurality of inlet holes 516.
The process starts at step 702. A substrate such as silicon is loaded into the process chamber at step 704. At step 706, a film such as carbon-based film is deposited on the silicon substrate in the process chamber. In an embodiment of the invention, the process gas is a hydrocarbon like cyclopentene and is supplied to the reactor at a rate of about 350 sccm. In this embodiment, additive gases may be Argon and Helium gas and are supplied to the reactor at a rate of 1,700 sccm and 1,300 sccm respectively. A conduit supplies the process gas to the process chamber through an upper body. The process gas is introduced into the process chamber through the plurality of holes of a shower plate. In an embodiment of the invention, the size (diameter) of the shower plate is 0.350 mm and is set at a temperature range of 100 to 200 centigrade. The process chamber has a susceptor for holding a substrate. In an embodiment of the invention, the size (diameter) of the substrate is 0.300 mm and the distance between the shower plate and the susceptor is in the range of 1 to 50 mm. Further, the susceptor may be set at a temperature range of 200 to 600 centigrade.
The silicon substrate is unloaded from the process chamber at step 708 after the carbon film is deposited on it. At step 710, the reactive species are generated in a remote plasma unit in order to remove the unwanted residues inside of the process chamber. In various embodiments of the present invention, the reactive species may be fluorine radicals, oxygen radicals, and mixture thereof. The preliminary plasma is struck by introducing an inert gas into a remote plasma unit. Thereafter, a cleaning gas such as oxygen is introduced into the remote plasma unit and the reactive species are generated from the cleaning gas. In an embodiment of the present invention, the inert gas may be argon, and plasma is struck by an inductively coupled plasma (ICP) source. The reactive species are generated by activation of the cleaning gas molecules. In an embodiment of the present invention, the power supplied to maintain the plasma in remote plasma unit 102 may be at least 2,000 W.
At step 712, the reactive species are supplied to the process chamber through a first body. A first conduit connects the remote plasma unit to the first body. The first body has a plurality of inlet holes. The reactive species are supplied to the process chamber through the plurality of inlet holes. The flow of the reactive species can be controlled. In an embodiment of the invention, the flow rate of the reactive species is controlled by inserting one or more parts into one or more of the plurality of inlet holes. In another embodiment of the invention, the flow rate of the reactive species is controlled by changing the flow rate of the cleaning gas. In an embodiment of the invention, the one or more parts are metallic parts. In another embodiment of the invention, the one or more parts are made of a ceramic material. Further, the flow rate of the reactive species can be controlled independently across the plurality of inlet holes in accordance with the area that is to be cleaned. That is, one or more parts may be inserted into one or more of the plurality of inlet holes 110, and one or more of the plurality of inlet holes 110 may be kept open, in accordance with the area that is to be cleaned.
At step 714, the reactive species react with the unwanted residues in the process chamber. These unwanted residues are formed in the process chamber during the film-deposition process. The reactive species react with the unwanted residues and generate volatile products. The volatile products are removed from the process chamber at step 716 using an exhaust line. The process ends at step 718.
The remote plasma cleaning process and apparatus of the present invention enable high-utilization efficiency of the reactive species. The uniform distribution of the reactive species ensures high cleaning efficiency. Further, the remote plasma cleaning process of the present invention can control the flow rate of the reactive species. Control over the flow rate of the reactive species makes the process suitable for the use of radicals such as oxygen radicals, NF3 radicals and the like as the reactive species.
While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claims.
