Lecture 08 Dry Etching

Lecture 08 Dry Etching - Dry Etching Dr Bruce K Gale...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Dry Etching Dr. Bruce K. Gale Fundamentals of Micromachining BIOEN 6421 EL EN 5221 and 6221 ME EN 5960 and 6960 Etching Issues - Anisotropy • Isotropic etchants etch at the same rate in every direction Isotropic An-isotropic mask Etching Issues - Selectivity • Selectivity is the ratio of the etch rate of the target material being etched to the etch rate of other materials • Chemical etches are generally more selective than plasma etches • Selectivity to masking material and to etch- s impo Mask target Etch stop Dry Etching Overview • What is dry etching? – Material removal reactions occur in the gas phase. • Types of dry etching – Non-plasma based dry etching – Plasma based dry etching • Why dry etching? • Development of dry etching • Plasma parameters/influences Dry Etching Advantages • Eliminates handling of dangerous acids and solvents • Uses small amounts of chemicals • Isotropic or anisotropic etch profiles • Directional etching without using the crystal orientation of Si • Faithfully transfer lithographically defined photoresist patterns into underlying layers • High resolution and cleanliness • Less undercutting • No unintentional prolongation of etching • Better process control • Ease of automation (e.g., cassette loading) Dry Etching • Disadvantages: – Some gases are quite toxic and corrosive – Re-deposition of non-volatile compounds – Need for specialized (expensive) equipment • Types: – Non-plasma based = uses spontaneous reaction of appropriate reactive gas mixture – Plasma based = uses radio frequency (RF) power to drive chemical reaction Non-plasma Based Dry Etching • Isotropic etching of Si • Typically fluorine-containing gases (fluorides or interhalogens) that readily etch Si • High selectivity to masking layers • No need for plasma processing equipment • Highly controllable via temperature and partial pressure of reactants Xenon Difluoride (XeF 2 ) Etching • Isotropic etching of Si • High selectivity for Al, SiO 2 , Si 3 N 4 , PR, PSG • 2XeF 2 + Si Æ 2Xe + SiF 4 • Typical etch rates of 1 to 3 µ m/min • Heat is generated during exothermic reaction • XeF 2 reacts with water (or vapor) to form HF Interhalogen (BrF 3 & ClF 3 ) Etching • Nearly isotropic profile • Gases react with Si to form SiF 4 • Surface roughness: ~40 to 150 nm...
View Full Document

This note was uploaded on 11/16/2011 for the course MSE 5960 taught by Professor Douglas during the Fall '04 term at University of Florida.

Page1 / 8

Lecture 08 Dry Etching - Dry Etching Dr Bruce K Gale...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online