July 12, 2021, Filed Under: MEMS processingDifferences among Etchers The main differences among etchers are size and gas. ICP RIE Etchers 2300 Exelan Flex LAMDSEOxford 100STSwafer size 300mm>100mm>100mmmaterialSiliconSilicon, metalsC4F8yesyesSF6yesyesCF4yesyesO2yesyesyesyesAryesyesyesyesHeyesCOyesCO2yesCHF3yesCH4yesHBryesyesyesN2yesyesSF6yesH2yesyesCI2yesyesBCI3yesSiCI4yes Among ICP RIE etchers, we often use DSE and Oxford 100. Because DSE conducts Bosch etch process, the tool is very appropriate for deep etching. Meanwhile, only Oxford 100 has BCI3, so we use Oxford 100 to etch some metals or metal oxidation. properties table: why can BCI3 etch Al2O3. RIE Etchers 790 Plasma Therm #1790 Plasma Therm #2Batchtop Plasma ThermOxford 80Trion OracleCF4yesyesyesyesBCI3yesSiCI4yesO2yesyesyesyesCH4yesyesCHF3yesyesyesC2H6yesSF6yesyesyesH2yesyesyesAryesyesyesN2yesyesCI2yesyesyesyesHeyesyesHBryesSO2yesCO2yes Because CHF3 holds excellent selectivity for etching silicon with the mask of silicon dioxide, we often use Oxford 80 to etch silicon dioxide which is used for other layers’ masks. Common etch processes used in microfabrication Material to be etchedWet etchantsPlasma etchantsAluminium (Al)80% phosphoric acid (H3PO4) + 5% acetic acid+ 5% nitric acid (HNO3) + 10% water (H2O) at 35–45 °C[4]Cl2, CCl4, SiCl4, BCl3[5]Indium tin oxide [ITO] (In2O3:SnO2)Hydrochloric acid (HCl) + nitric acid (HNO3) + water (H2O) (1:0.1:1) at 40 °C[6]Chromium (Cr)“Chrome etch”: ceric ammonium nitrate ((NH4)2Ce(NO3)6) + nitric acid (HNO3)[7]Hydrochloric acid (HCl)[7]Gallium Arsenide (GaAs)Citric Acid diluted (C6H8O7 : H2O, 1 : 1 ) + Hydrogen Peroxide (H2O2)+ Water (H2O)Cl2, CCl4, SiCl4, BCl3, CCl2F2Gold (Au)Aqua regiaIodine solutionMolybdenum (Mo)CF4[5]Organic residues and photoresistPiranha etch: sulfuric acid (H2SO4) + hydrogen peroxide (H2O2)O2 (ashing)Platinum (Pt)Aqua regiaSilicon (Si)Nitric acid (HNO3) + hydrofluoric acid (HF)[4]Potassium hydroxide (KOH)Ethylenediamine pyrocatechol (EDP)Tetramethylammonium hydroxide (TMAH)CF4, SF6, NF3[5]Cl2, CCl2F2[5]Silicon dioxide (SiO2)Hydrofluoric acid (HF)[4]Buffered oxide etch [BOE]: ammonium fluoride (NH4F) and hydrofluoric acid (HF)[4]CF4, SF6, NF3[5]Silicon nitride (Si3N4)85% Phosphoric acid (H3PO4) at 180 °C[4] (Requires SiO2 etch mask)CF4, SF6, NF3,[5] CHF3Tantalum (Ta)CF4[5]Titanium (Ti)Hydrofluoric acid (HF)[4]BCl3[8]Titanium nitride (TiN)Nitric acid (HNO3) + hydrofluoric acid (HF)SC1Buffered HF (bHF)Tungsten (W)Nitric acid (HNO3) + hydrofluoric acid (HF)Hydrogen Peroxide (H2O2)CF4[5]SF6[citation needed]
