Patent ID: 6821892
Filing Date: 2004-11-23
Classification: H01L

Abstract:
A method of determining the etch rate and time to etch as a function of the properties of the etching process and of the film being etched, comprising the steps of:providing a rate formula ER(C,T)=ER0*C*exp(âˆ’Ea/RT)+A; providing a substrate; providing an etch bath in a tank; providing an etch concentration monitor in said tank; providing a temperature monitor in said tank; forming a film over said substrate; measuring the initial thickness of said film over said substrate; placing said film on said substrate in said tank; starting the etching of said film in said tank, and simultaneously recording the start time of said etching; measuring a first temperature of said etch bath in said tank; measuring a first concentration of said etch bath in said tank; stopping said etching of said film, and recording the stop time of said etching; removing said substrate with said film thereon from said tank; measuring the final thickness of said film on said substrate; calculating a first film loss by subtracting said initial thickness from said final thickness of said film; calculating a first etch time by subtracting said start time from said stop time of etching; calculating a first etch rate (ER(T,C)1) as a function of said first temperature and first concentration; repeating previous steps at second, third, (nâˆ’1) and n temperatures while holding constant said first concentration, and calculating the corresponding second, third, (nâˆ’1) and nth etch rates [ER(T)C2, . . . ER(T)C(nâˆ’1), ER(T)Cn] values as a function of said temperatures, and their statistical average (ER(T)C,avg.); repeating previous steps at second, third, (nâˆ’1) and n concentration while holding constant said first temperature, and calculating the corresponding second, third, (nâˆ’1) and nth etch rates [ER(C)T2, . . . ER(C)T(nâˆ’1), ER(C)Tn] values as a function of said concentrations, and their statistical average (ER(C)T,avg.); using said values in said formula to calculate etch rate ER for subsequent etching of said film for a specified film loss or to a specified film thickness; providing a substrate having formed thereon a first film to be etched and a second film, wherein a first film thickness of said first film is less than a second film thickness of said second film; calculating a film loss &Dgr;H for said specified film loss or for said specified film thickness; and calculating etch time; wherein T is temperature, C is concentration, ER(C, T) is etch rate as a function of concentration (C) and temperature (T), ER0 is a first constant, Ea is activation energy; R is the universal gas constant, A is a second constant and &Dgr;H is film loss.