Optical Emission Spectrometry Diagnosis Of Pulse-modulated RF Capacitive Coupling Discharge In SiH₄/C₂H₄/Ar

Pulse-modulated of low pressure radio frequency (RF) capacitive coupled plasmas have been widely used for manufacturing microelectronic devices and integrated circuit processing in the semiconductor industry. A voltage-control type power source can be used as an additional parameter to gain additional control such as densities and temperatures which can change the gas phase chemistry and to modify the energy of ions bombarding substrates placed on either the rf or the earthed electrodes. And thus improve the plasma enhanced chemical vapor deposition and etch results. Also, by pulsing the RF signal, it is possible to control the plasma properties and prevent the dielectric from reaching too high a temperature for surface treatment. An applied rf electric field for plasma production often disturbs probe measurements because it becomes an origin of noise for the measurement circuit. Therefore plasma by rf pulse discharge is used for rf electric free measurement without an rf electric field.We use the pulse modulated RF plasma source in the experiment and use Princeton Acton 2500i emission spectrometer as detection means. We mark five Ar I lines and Ar+ line, and discuss the change of electronic excitation temperature and emission intensity of line with experimental conditions (power, pressure, pulse-modulated frequency, Duty Cycle) in Ar discharge. The results are as follows:1.As the power increases, electronic excitation temperature rises first and then levels off, emission intensity of Ar+ tend to increase linearly.2.As the pressure increases, electronic excitation temperature decreases, emission intensity of Ar+ tend to increase linearly.3.As the modulation frequency increases, electronic excitation temperature rises first and then decreases, the peak is the value corresponding to about 20Hz,when the duty cycle is 70%(pulse-on is 35ms), pulse-off is 15ms,emission intensity of Ar+ increases slowly first and then decreases slowly, and then increases rapidly, the peak is the value corresponding to about 20Hz,when the duty cycle is 70%(pulse-on is 35ms),pulse-off is 15ms.4.As the duty cycle increases, electronic excitation temperature increases slightly, emission intensity of Ar+ increases first and then decreases, the peak is the value corresponding to 80%,when the modulation frequency is 2KHz(pulse-on is 0.4ms),pulse-off is 0.1ms. We mark Ar+357.6nm,Si2+ 380.6nm,Si+ 518.1nm,601.3nm,C+ 426.7nm and five Ar I lines, discuss the change of electronic excitation temperature and emission intensity of lines with experimental conditions (power, pressure, pulse-modulated frequency, duty cycle) in SiH4/C2H4/Ar gas mixture discharge.The results are as follows:1.As the power increases, electronic excitation temperature increases first and then levels off, emission intensity of Ar+,Si+,Si+,C,C+ increase but its rate of increase becomes small.2.As the pressure increases, electronic excitation temperature decreases, and emission intensity of Ar+,Si2+,Si+,C, C+ increase first and then decrease, the peak is the value corresponding to 60-70Pa.3. As the modulation frequency increases, electronic excitation temperature increases first and then decreases, the peak is the value corresponding to 20Hz,when the duty cycle is 70%(pulse-on is 35ms),pulse-off is 15ms,emission intensity of Ar+ increases first and then decreases, the peak is the value corresponding to 2KHz,when the duty cycle is 70%(pulse-on is 0.35ms),pulse-off is 0.15ms,emission intensity of Si2+,Si+ increase, but emission intensity of C,C+ decrease in the range of low modulation frequency, and increase in the range of high modulation frequency.4. As the duty cycle increases, electronic excitation temperature increases first and then decreases, the peak is the value corresponding to 50%,when the modulation frequency is 2KHz(pulse-on is 0.25ms),pulse-off is 0.25ms,emission intensity of Ar+ increases, emission intensity of Si2+,Si+,C,C+ increase first and then decrease, the peak of Si2+,C is the value corresponding to 90%,when the modulation frequency is 2KHz(pulse-on is 0.45ms),pulse-off is 0.05ms,the peak of Si+, C+ is the value corresponding to 85%,when the modulation frequency is 2KHz(pulse-on is 0.425ms),pulse-off is 0.075ms,the peak of Si2+,Si+ is sharper than other peaks of lines.Overall, the electronic excitation temperature is higher in gas mixture discharge than in Ar discharge.