PLASMA REACTION CHAMBER HAVING CONDUCTIVE DIAMOND-COATED SURFACES

Abstract: A reactive ion etching chamber is disclosed having conductive diamond-coated wall surfaces (1, 2) to prevent the undesired sputtering of wall particles which can contaminate semiconductor device workpieces undergoing etching within the chamber. The diamond layer is conductive to enable the coated chamber walls to be used as an electrical ground in the reactive ion etching process.

Description: PLASMA REACTION CHAMBER HAVING CONDUCTIVE DIAMOND-COΛTED SURFACES Background of the Invention 1. Field of the Invention The present invention generally relates to semi¬ conductor device manufacturing tools having plasma reaction chambers and, more particularly, to such chambers having diamond-coated surfaces to prevent sputtering of the chamber surfaces and to stop con- comitant contamination of the semiconductor device workpiece therein. 2. Description of the Related Art As described in U.S. patent 4,657,617, issued on April 14, 1987 to Randall E. Johnson et al. for Anodized Aluminum Substrate for Plasma Etch Reactor, the gas plasmas typically used in semiconductor device etching tools react with tool surfaces and corrode the same as well as release some surface particles which may contaminate the semiconductor workpiece. Attempts have been made to protect some tool surfaces against such corrosion and to prevent undesirable contamination of the device being fabricated. Said patent teaches that the anodization of an aluminum wafer substrate assembly exposed to the plasma would protect those substrate surfaces from damaging corrosion. The improvement afforded by tool anodization, however, is wanting in the context of constantly evolving state-of-the-art semiconductor devices having greater densities and smaller geometries where sensitivity to contaminants becomes increasingly critical. One of the requirements of the walls of the plasma reaction chamber is to have electrically con¬ ductive properties so that they may be used as an electrical ground in the plasma reaction process. Insulating materials per se, such as anodized aluminum, therefor cannot be used for protectively coating those tool surfaces that must remain conductive. Summary of the Invention An object of the present invention is to sub¬ stantially reduce reaction between the plasma and the chamber walls of a plasma reaction chamber. Another object is to prevent sputtering of the chamber walls of tools used in reactive ion etching processes. A further object is to prevent contamination of semiconductor workpieces due to reaction of the plasma and the chamber walls of a reactive ion etching tool. Another object is to place an electrically con¬ ductive but nonreacting coating on the surfaces of semiconductor device tools exposed to plasma. In accordance with the present invention, the sputtering of the chamber walls of tools used in the reactive ion etching of semiconductor devices is pre¬ vented by coating the walls with a conductive diamond layer. The diamond layer is formed using known pro¬ cesses such as chemical vapor (CVD) , ion bombardment or ion beam expitaxial deposition processes. Suit- able conductivity is imparted to the diamond layer by control of CVD deposition process parameters whereby predetermined amounts of graphite are introduced into the diamond or by the use of conductive dopants. The conductive properties so created do not impact the desired hardness, inertness and strength of the diamond layer because the required amount of non- diamond material is minute. 3. Brief Description of the Drawing The sole figure is a simplified cross-sectional view of a plasma reaction chamber having conductive diamond-coated surfaces in accordance with the pre¬ sent invention. Description of the Preferred Embodiment Aluminum commonly is used as the material for constructing the chamber for housing the plasma and the semiconductor device workpiece in a reactive ion etching tool. Reactive ions from the etching plasma bombard the chamber walls as well as the intended workpiece and liberate aluminum atoms. The liberated atoms erode the chamber walls and, more objection¬ ably, contaminate the semiconductor device. In order to avoid such erosion and contamination, the present invention contemplates forming a diamond layer on the aluminum walls of the chamber. Diamond deposition processes for aluminum substrates are known in the art and are described, for example, in U.S. patent 4,767,517, issued Aug. 30, 1988 to Akio Hiraki et al. for Process of Depositing Diamond-Like Thin Film by Cathode Sputtering and in U.S. patent 3,840,451, issued Oct. 8, 1974 to V. M. Golyanov et al. for Method of Producing an Artificial Diamond Film. The diamond layer is desirably hard, strong and nonreactive to the reactive ion bombardment from the plasma. However, it could also be undesirably non- conductive as a coating on the chamber walls. It should be noted that the chamber walls are used as electrical ground in the reactive ion etching process. The diamond coating is made conductive, in accordance with the present invention, by the doping of proper impurities as stated in the cited U.S. patents 4,767,517 and 3,840,451. Alternatively, the deposited diamond layer can be made conductive by close control of the CVD process parameters to determine the amount of graphite interspersed with the diamond. Using either of the above conductivity determin¬ ing techniques, a resistivity of about (10 Ω-cm pre¬ ferably is imparted to the diamond coating which is deposited along surfaces 1 and 2 of the figure. Other desired characteristics of the diamond coating include a thermal conductivity of about 20 /cm °K (to allow good heat transfer from the plasma 3 to the inner chamber wall 4) and a thermal expansion rate of about 0.8 x 10 M/°K. A dielectric constant of about 7 5.5 and a breakdown voltage of about 10 V/cm also is preferred.

Claims: CLAIMS 1. A chamber for containing a plasma for interacting with a workpiece which can become contaminated by particles released from the walls of said chamber consequent to said interacting, characterized in that the surfaces of said chamber surrounding said plasma are covered by a conductive diamond layer. 2. A plasma reaction chamber for containing a semiconductor device workpiece and a plasma interacting with said workpiece, characterized in that the surfaces of said chamber surrounding said plasma are covered by a conductive diamond layer. 3. The chamber defined in claim 2 wherein said layer has a resistivity of about 10 -cm. 4. The chamber defined in claim 2 wherein said layer has a thermal conductivity of about 20 /cm°K. 5. The chamber defined in claim 2 wherein said layer has a dielectric constant of about 5.5. 6. The chamber defined in claim 2 wherein said 7 layer has a breakdown voltage of about 10 V/cm.

Inventors: DOWNEY DOUGLAS JOHN, LIPORACE JAMES WILLIAM, DOWNEY, DOUGLAS, JOHN, LIPORACE, JAMES, WILLIAM
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1990
Main classification: H01L21
IPC codes: C23C14, C23C16, C23F4, H01J37, H01L21