Buffered Oxide etchants have a long history in the IC industry as etchants for SiO2 films as well as for pre-diffusion and pre-metalization surface cleans. The ICL uses a 7:1 BOE as its wet oxide etch and diluted HF (unbuffered) for the surface cleans. Buffered HF has several advantages over unbuffered HF as an etchant, namely improved
SPTS’ patented Primaxx® HF/Alcohol process employs a reduced pressure, gas phase environment for the isotropic etch removal of sacrificial oxide layers. The process is generally carried out at pressures between 75 and 150 torr providing controlled, residue-free etching. Typical vertical and lateral oxide etch rates are in the 0.1 - 10 Microtechnology/Etching Processes - Wikibooks, open books Sep 03, 2018 Surface Cleaning and Wet Processing HF is typically diluted with DI water in order to slow down the etch rate of SiO2, thereby ensuring better etch uniformity. Typical dilution ratios range from 1:1 H2O:HF to 100:1 H2O:HF. For certain critical etches, the HF may be diluted with ammonium fluoride (NH4F) to promote more uniform liquid coverage on the Si surface, and it is then
Si3N4, LSN, SiO2 and PR etch rates for selective Si3N4 etching SF6-CH2F2-N2 En nm/m Elsn nm/min Esio nm/min Epr nm/min. CNF TCN, page 8 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 3 5 7 1200 1600 2000 4 8 12 9 12 15 s RIE power [Watts] ICP power [Watts] CH2F2 flow rate …
SiO2 + 6HF = H2 + SiF6 + 2H2O. As the etching rate of hydrofluoric acid on silicon dioxide is very high, it is difficult to control in the process, so in practice are used after dilution of hydrofluoric acid solution, or the addition of ammonium fluoride as a buffer mixture, to etch the silicon dioxide.
Conductivity measurements can be used to monitor the etching rate of SiO2 in HF solutions very accurately when the etching rate is relatively slow (around 1 A/min).
Conductivity measurements can be used to monitor the etching rate of SiO2 in HF solutions very accurately when the etching rate is relatively slow (around 1 A/min). the etch rates of other materials that will be exposed to the etch, such as masking films and underlying layers, enables an etch process to be chosen for good selectivity (high ratio of etch rate of the target material to etch rate of the other material)—if one exists. While several large literature-review compilations in the solution coupled with temperature also effects the etch rate as seen in the following figures. Etch rate of SiO 2 increases with increasing weight % of HF in the etch solution, as well as higher ratios of NH 4 F buffer in the solutions. Etch rate also increases with increasing temperature. Etch rate: r • Speed at which ethcing occurs • Typical unit: r [nm/min] Selectivity : S • Ratio of two etch rates Example 1: SiO 2 etching with hydrofluoric acid (HF): SiO 2+ 6 HF H 2SiF 6 + 2 H 2O A. Determine the etch time for a 1,2 μm thick SiO 2 film with r SiO2 = 400 nm/min 3 min. B. How thick should the resist mask be if the The different equilibria in HF and HF/HCl solutions are examined and the etching reaction of SiO2 is investigated as a function of the different species present in the HF solution. A new model for The commented results are based on the segregation at Si/SiO2. We have developed a “theory” based on an empirical equation which modelizes the etch rate in non doped SiO2, to modelize it for those n-doped and p-doped. This “theory” stipulates that the etch rate in doped SiO2 can be predicted by knowing the etch rate in nondoped one.