Etching a substrate: processes – Gas phase etching of substrate – Application of energy to the gaseous etchant or to the...
Patent
1997-09-02
2000-01-18
Beck, Shrive
Etching a substrate: processes
Gas phase etching of substrate
Application of energy to the gaseous etchant or to the...
438708, 438935, 134 13, 156345, C23F 112
Patent
active
060155035
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus which provides for the conditioning of the surface of a substrate in a plasma-less gas phase environment. It finds particular application in etching, cleaning, or bulk stripping removal of films or contaminants from the surface of a semiconductor wafer for use in the fabrication of integrated circuits.
2. Description of the Related Art
The traditional standard for surface contamination removal in the semiconductor industrv is the RCA clean which uses liquid aqueous chemicals. Highly selective bulk film stripping is also commonly carried out with liquid aqueous chemicals. The liquid aqueous chemical processes have problems involving safety, waste disposal, cleanliness and cost, and these problems make the use of gaseous processes very attractive.
The use of plasma containing reactive gas mixtures or reactive ion etching (RIE) are an alternative to liquid aqueous chemical processes. In these type of processes, the container is filled with a low pressure gas, the substrate is inserted into the container along with a reactive etchant gas. Voltage is applied to excite the gas, which chemically reacts with the surface. These types of processes have the disadvantage of causing additional damage and contamination of the substrate surface. It is also known to use the effluent of a gas plasma having at least one reactive specie, but being substantially free of electrically charged particles. This is known in the art as a downstream plasma source and is shown in U.S. Pat. No. 4,687,544 to Bersin, entitled "Method And Apparatus For Dry Processing of Substrates".
Plasma-less UV treatments have also been disclosed before. For example, U.S. Pat. No. 2,841,477 to Hall, entitled "Photochemically Activated Gaseous Etching Method" is the earliest known reference teaching a process of using a photochemically activated gas to etch semiconductor materials. This reference shows an etching method involving the steps of immersing the semiconductor material in a photolyzable gas and directing UV light toward the portion of the material to be etched. The gas is apparently static. The UV light causes the photolyzable gas to dissociate into various chemically active species which react with the substrate surface.
U.S. Pat. No. 3,122,463 to Ligenza, entitled "Etching Technique for Fabricating Semiconductor Or Ceramic Devices" is another example showing a method of using photochemically activated F.sub.2 O gas to etch semiconductor materials. This reference shows a method of immersing the semiconductor material in a static gas and directing UV light toward the portion of the material to be etched.
Processes of the type disclosed in Hall or Ligenza have the disadvantages of non-uniform gas distribution and of a static gas regime which does not allow the transport of contaminants and etching residues out of the reactor during the etch reaction.
It has been known to use a flow of gas across the surface of a substrate in an etching process. Such processes provide excellent process control and reduce accumulation of contamination and residue at the wafer surface. For example, U.S. Pat. No. 4,749,440 to Blackwood et al, entitled "Gaseous Process And Apparatus For Removing Films From Substrates" assigned to FSI Corporation and Texas Instruments Inc. shows a device which causes anhydrous reactive gas to flow over the substrate in the presence of water vapor, to chemically react with the surface.
U.S. Pat. No. 5,022,961 to Izumi et al, entitled "Method For Removing A film On A Silicon Layer Surface" shows a device, substantially identical to the device of U.S. Pat. No. 4,749,440, which is used to etch silicon oxide using HF and alcohol gases directed across the surface of a substrate wafer.
U.S. Pat. No. 5,228,206 to Grant et al, entitled "Cluster Tool Dry Cleaning System" shows a device which directs a flow of reactive gas across the surface of a substrate and asserts that UV radiation causes the gas to photochemically react with the substrate s
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Butterbaugh Jeffery W.
Fayfield Robert T.
Gray David C.
Heitzinger John
Hiatt Fred C.
Beck Shrive
Chen Bret
FSI International Inc.
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