Abstract A process is described for the fabrication of devices in which thin films of tungsten are etched by a chemical procedure. This chemical procedure involves the use of ferricyanide as the oxidizing agent contained in an aqueous solution. The solution also contains a substance with an affinity for protons to promote the etching reaction. The pH of the etching solution is between 7 and 10 but can be higher if desired. Such etching solutions not only yield etching rates of practical interest, but are usable with photoresists which are ordinarily attacked at high pH. In cases where enhanced etching resolution and uniformity is of particular importance, a special procedure is described which involves spraying the etchant and spinning the sample.
The process of claim 1 in which the proton acceptor has a basicity constant between 10 8 and 10 3.
Claim 2
Dependent Claim
23 words
The process of claim 1 in which the concentration of proton acceptor is between 1 and 100 times the mole concentration of ferricyanide.
Claim 3
Dependent Claim
23 words
The process of claim 1 in which the proton acceptor is selected from the group consisting of ammonia, ethylenediamine, piperidine, pyridine and acetate.
Claim 4
Dependent Claim
21 words
The process of claim 1 in which the proton acceptor is selected from the group consisting of HPO4 and HBO3 .
Claim 5
Dependent Claim
18 words
The process of claim 1 in which the aqueous solution is applied to the tungsten film by spraying.
Claim 6
Dependent Claim
16 words
The process of claim 6 in which the devices with the tungsten thin film are rotated.
Claim 7
Dependent Claim
26 words
The process of claim 1 in which the solution contains conjugate proton donor (substance obtained by adding a proton to the proton acceptor) to lower pH.