This feature will be updated on a regular basis with information related to Semiconductor, MEMS, ORGANIC devices processing/manufacturing.
Notes on Etchants, Etching, Chemical/Photo Milling
Wafer or substrate preparation: Before applying resist, be sure that the wafer or polymer surface to be coated is very carefully cleaned. Good adhesion of the photoresist is imperative for deep etching. Traces of organic matter, dirt and dust lead to imperfect results. Recommended steps in the surface preparation is plasma etching or RCA clean. Sometimes Acetone /Alcohol may suffice.
Photoresist Application: Follow instructions for application of pos/neg photo resist.as well as lithography as needed
Post baking will improve bonding and chemical resistance to the photoresist film.
ETCHANTS: Use recommended concentrations of etchants. For ferric chloride, adjust specific gravity with Baume hydrometer. Do not guess. 36 Baume ferric chloride is used for most applications. Weaker or stronger mixes are generally not as good, that is, they are "too hot," too slow, or lead to excessive undercutting. For increased etching speed, add about 1% muriatic acid to 36 B. FeC l3 and use at about 90°F, i.e., one gallon of muriatic acid to 100 gallons of ferric chloride.
Use caution wear protective gear.as well as glasses always use an exhaust
Metals
| Aluminum | a. 8-20% sodium hydroxide at 140-180°F b. Ferric chloride 36 Baume (somewhat spent bath) c. Muriatic acid 20% by volume |
| Beryllium CU | a. Ferric chloride 36 Baume 90°F b. Chromic-sulfuric acid mixtures |
| Brass | a. Ferric chloride 36 Baume 90°F b. Chromic-sulfuric acid mixtures |
| Chromium | a. Hydrochloric acid 1 part + water 1 part b. Ferric chloride 2 parts + hydrochloric acid 1 part |
| Constantan | a. Ferric chloride 36 Baume 90°F |
| Copper | a. Ferric chloride 36 Baume 90°F b. Ammonium persulfate 2 lbs./gal solution c. Chromic-sulfuric acid mixtures |
| Germanium | a. Hydrofluoric acid b. Hydrofluoric-nitric acids |
| Glass | a. Hydrofluoric acid 10-15% + balance water |
| Gold | a. Aqua regia (hydrochloric acid 3 parts + nitric 1 part) |
| Hastelloys | a. Ferric chloride 36 Baume 90°F |
| Havar | a. Ferric chloride 36 Baume 90°F |
| Invar | a. Ferric chloride 36 Baume 90°F |
| Inconels | a. Ferric chloride 36 Baume 90°F |
| Kovar | a. Chromic-sulfuric acid |
| Lead | a. Ferric chloride 36 Baume 90°F |
| Magnesium | a. Nitric acid 12-15% by volume |
| Manganese | a. Hydrochloric acid 1 part + water 1 part b. Ferric chloride 2 parts + hydrochloric acid 1 part |
| Molybdenum | a. Sulfuric acid 1 part + nitric 1 part + H2O 3 parts b. Nitric acid 1 part + HC1 1 part + H2O 1-2 parts c. Electric etch in 5% sodium hydroxide |
| Moly Peramalloy | a. Ferric chloride 36 Baume 110°F |
| Nagro-G | a. Aqua regia |
| Nichrome | a. Ferric chloride 36 Baume 110°F b. HC1 4 parts + H2O 1 part |
| Nickel | a. Ferric chloride 36 Baume 120°F |
| Nickel Silver |
a. Ferric chloride 36 Baume 110°F |
| Ni-Span-C | a. Ferric chloride 36 Baume 110°F |
| Palladium | a. Aqua regia (hydrochloric acid 3 parts + nitric 1 part) |
| Phosp. Bronze | a. Ferric chloride 36 Baume 110°F |
| Platinum | a. Aqua regia (hydrochloric acid 3 parts + nitric 1 part) |
| Silicon | a. Ferric chloride 38 Baume 4 parts + nitric acid 4 parts + hydrofluoric acid 1 part |
| Silver | a. Nitric acid 8 parts + water 1 part b. Ferric chloride 36 Baume 90°F |
| Stainless Steel | a. (Low 300) Ferric chloride 36 Baume 90°F (except 301) a. (Low 300) Nitric acid 1 part + hydrochloric acid 1 part + water 1-2 parts |
| Steels | a. Ferric chloride 36 Baume 90°F |
| Tantalum | a. Hydrofluoric acid 1 part + nitrite acid 1 part + water 2 parts |
| Tellurium | a. Nitric acid 2 parts + water 3 parts> b. Ammonium persulfate 2 lbs./gal solution |
| Tin | a. Ferric chloride 36 Baume 90°F |
| Titanium | a. Hydrofluoric acid b. Hydrofluoric-nitric acids b. Hydrofluoric acid 1 part - water 20 parts |
| Tungsten | a. Electrolytic in 5% sodium hydroxide b. Nitric acid 12-15% by volume |