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Adjustable Alloy Deposition Using Hollow Cathode Electrodes

IP.com Disclosure Number: IPCOM000062464D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Bumble, B: AUTHOR [+2]

Abstract

A method for adjusting the composition of alloy layers utilizing cathode plasmas is described herein. The method can be most easily understood with reference to Fig. 1. In this figure, a simple RF sputtering system is shown with the primary alterations to the powered electrode 3. The system consists of a grounded vacuum chamber 4 with some means of vacuum pump pumping 5 and the introduction of a working gas 6 through a leak valve 7. The electrode 3 is powered by an RF generator 8, and the power is conducted to the electrode 3 through a standard matching network 9. A plasma will be formed in the chamber 4 if there is suitable RF power supplied to the electrode and the gas pressure is in a suitable range (millitorr).

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Adjustable Alloy Deposition Using Hollow Cathode Electrodes

A method for adjusting the composition of alloy layers utilizing cathode plasmas is described herein. The method can be most easily understood with reference to Fig. 1. In this figure, a simple RF sputtering system is shown with the primary alterations to the powered electrode 3. The system consists of a grounded vacuum chamber 4 with some means of vacuum pump pumping 5 and the introduction of a working gas 6 through a leak valve 7. The electrode 3 is powered by an RF generator 8, and the power is conducted to the electrode 3 through a standard matching network 9. A plasma will be formed in the chamber 4 if there is suitable RF power supplied to the electrode and the gas pressure is in a suitable range (millitorr). The electrode 3 will be sputtered by ion bombardment from the plasma and this sputtered material will be deposited on the samples 10. The samples may be biased or floating, depending on the desired film characteristics. The electrode 3 is of primary interest here, and is shown in cross-section in Fig. 2. The target has the cross-section of a "bucket RF electrode". It is constructed of two separate materials. The back plate 13 of the electrode will be described as material "X". The tubular section of the electrode 14 is constructed of material "Y". These materials may be metals, semiconductors or dielectrics for the purposes of this description, although materials of similar type will operate more efficiently (e.g., both metals or both insulators, etc.). The formation of the plasma in Fig. 1 results in the formation of a plasma sheath at the electrode surface. This sheath is designated as a dashed line 15 in Figs. 2 and 3. Depending on the plasma density, the sheath will behave differently inside the cavity formed by the bucketshaped electrode opening. When the plasma is dense, as it would be at high working gas pressure, the sheath will be of the form shown in Fig. 2. In this case, the sheath is small compared to the dimensions of the bucket-shaped opening, and follows the contour of the inside of the electrode. In this case, the walls (material Y) and the back plate (material X) will be sputtered uniformly. The net flux of material leaving the opening and landing on some sample will then be a combination of both materials. In the second case, as shown in Fig. 3, the plasma is less dense and the dimensions of the plasma sheath now are not small as compared...