Selective reactive ion etching of tungsten films in fluorinated gases. Technical report
The use of reactive ion etching (RIE) with fluorinated gas plasmas, such as SF/sub 6/, CHF/sub 3/ and CF/sub 4/ mixed with oxygen, to achieve selective patterning of tungsten films is reported. Rapid thermal annealing (RTA) was used to improve the properties of sputtered films. The resistivity of W films was found to decrease rapidly with annealing time (within 10 sec) and to exhibit an Arrhenius behaviour with annealing temperature. The etch rates of W, Si, and SiO/sub 2/ were measured as a function of oxygen percentage in the fluorinated gas plasma. The results on optimum selectivity indicate that a CHF/sub 3//70%O mixture results in W:Si and W:SiO/sub 2/ etch rate ratios of 2.4:1 and 2.1:1 for unannealed W films, and 1.6:1 and 1.8:1 for annealed samples, respectively. A higher W etch rate selectivity over SiO/sub 2/ was obtained in an SF/sub 6// 5% O/sub 2/ plasma where the etch rate ratio is 11.6:1 for unannealed W films and 3:1 for annealed W samples. For reverse selectivity, the optimum W:SiO/sub 2/ etch rate ratios measured are 1:7.7 in pure CHF/sub 3/ gas for unannealed W and 1:4.6 for annealed W. The optimum W:Si reverse selectivity of 1:10 is obtained with an SF/sub 6//30%O/sub 2/ mixture plasma for both annealed and unannealed films. Satisfactory anisotropic edge profiles were obtained with CHF/sub 3/ /70%O/sub 2/ and SF/sub 6//5%O/sub 2/ where vertical-to-later etch ratios of 3.5:1 and 2:1 were measured.
- Research Organization:
- Rensselaer Polytechnic Inst., Troy, NY (USA). Center for Integrated Electronics
- OSTI ID:
- 6136912
- Report Number(s):
- AD-A-183263/3/XAB; RPI/CIE/TR-16
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360101 -- Metals & Alloys-- Preparation & Fabrication
656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
ANNEALING
BEAMS
CHEMICAL REACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
ETCHING
FILMS
FLUIDS
FLUORINATION
GASES
HALOGENATION
HEAT TREATMENTS
ION BEAMS
METALS
NONMETALS
OPTIMIZATION
OXYGEN
RADIATIONS
SAMPLING
SPUTTERING
SURFACE FINISHING
THERMAL RADIATION
TRANSITION ELEMENTS
TUNGSTEN