Wet etching benches (RCA clean, Buffered Oxide etch, Isotropic Silicon etch, Aluminium etch, Si3N4 etch, Anisotropic Silicon etch (KOH), Chromium etch)

Vendor: PV-Plast, Model: ICD Heateflex Bath

Contact: Tatiana Becker (04-8293250, tatiana@ee.technion.ac.il)

RCA Clean: Standard set of wafer cleaning steps which need to be performed before high-temperature processing (Pre diffusion clean):

  1. Piranha – removal of organic impurities, photo resist,
    Chemicals: H2SO4(98%) : H2O2 (30%) (2:1), Temperature T=120oC
  2. HF bath – SiO2 etch, removal of mobile ions in oxide and Si/SiO2 interface HF(49%) :H2O (1:50), T=22oC
  3. SC1 (standard clean 1) – removal of ions and organic impurities
    Chemicals: NH4OH(30%) : H2O2(30%) : H2O (1:1:4), Temperature T=75oC
  4. SC2 removal of alkali ions and hydroxides of Al+3, Fe+3, Mg+2
    Chemicals: HCl (35%) : H2O2 (30%) : H2O (1:1:4), Temperature T=75oC

BOE: Buffered hydrofluoric acid (Buffer Oxide Etch)
40%wt HF (the buffer):49%wt NH4F (6:l)

­Poly Si Etch: 2 steps reaction Si Oxidation and then SiO2 etch.
Etchant: HNO3 (64%*, 70%in water) + NH4F(3%) + H2O(33%)

Aluminum etch: multi-step etch, the aluminum is oxidized by the nitric acid. The phosphoric acid and water simultaneously etch the resulting oxide.
Commercially prepared by J.T. Baker., Composed of 80% phosphoric acid, 5% nitric acid, 5% acetic acid, and 10% water. Some formulations may include a surfactant.

Phosphoric Acid – Si3N4 Etch
H3PO4 85%wt, 175oC

KOH Etching Apparat: orientation dependent Silicon wet etch.
Mixed from 330gr KOH pellets and 1.5 liters H2O (the solution is ~ 22%wt KOH)
The system uses a hot plate with a stirrer to heat and stir the solution during the etch process to 75°C.