高靈敏度微波共振探針研製及其射頻電漿鞘層影響分析

Development of a High Sensitivity Plasma Absorption Probe and RF Sheath Effect Analysis

邱晉陞(Chiou, Jin Sheng)

指導教授 ： 柳克強

國立清華大學/原子科學院/工程與系統科學系/碩士(2015年)

摘要

現今半導體製程中，電漿製程的穩定性是影響整個製程良率的關鍵之一，其中電漿密度在電漿製程中扮演一個重要的角色。因此即時監測腔體內電漿的情況，反饋腔體內的電漿狀態藉以調整製程參數來達到製程的需求，顯得相當重要。
本研究用電漿吸收探針(Plasma Absorption Probe, PAP)探討及分析射頻電漿鞘層(RF Sheath)對於實驗量測造成的影響，其原理為饋入微波至探針頂端，當探針結構與電漿中的電子發生共振時，微波能量被電漿大量吸收，此時饋入之微波反射為最小值，透過射頻網絡分析儀得到主動式電漿共振頻譜(Active Plasma Resonance Spectrum, APRS) 讀出反射的最小值，此時的頻率即為吸收頻率。透過模擬軟體(High Frequency Structure Simulator, HFSS)建立真實的電漿環境及探針結構獲得主動式電漿共振頻譜，比較實驗與模擬頻譜在半高寬上差異。
實驗量測的峰值半高寬比模擬結果還來得寬，這將降低對吸收頻率的辨識程度與量測之靈敏度，本研究初步結果為射頻電漿鞘層(RF Sheath)所造成的，透過於實驗量測，增設電容式耦合功率(偏壓功率Bias Power)用以提高電漿電位，預期峰值(peak)半高寬將隨著偏置射頻功率升高而變寬，進而證實射頻電漿鞘層對實驗量測的影響。並且研製新型電漿吸收探針，使量測到共振峰值更加得清晰進而提生共振頻率之解析度；而為了使微波探針量測於PECVD及ALD此種高氣壓與低密度電漿製程環境，因此採用於真空中本身就是共振結構的夾型共振器(Hairpin probe)並且以實驗與模擬方式研製夾型共振器(Hairpin probe)。

關鍵字

電漿監測 ； 電漿吸收探針 ； 懸浮式夾型共振器

並列摘要

Nowadays, in the semiconductor manufacturing process, the stability of plasma processing influence greatly to yield rate, while the plasma density is the key parameters for plasma processing. Therefore, monitoring and maintaining the plasma, by adjusting procedure parameter to achieve its needed state, it the important step to the process.
In this study, plasma absorption probe (PAP) is used to analyze that RF sheath affect the peak of spectrum in experiment. The probe tip is fed into the microwave, when the microwave resonates both with probe structure and with electron in the plasma, the microwave is absorbed greatly by plasma, in this time the microwave have lowest reflected and the absorption frequency can be obtained at the lowest point of the active plasma resonance spectrum (APRS). Using the High Frequency Structure Simulator (HFSS) to set the real plasma environment and probe structure, simulating and obtaining the active plasma resonance spectrum in simulation. Compare with the FWHM of spectrums in experiment,
The peak of spectrum in experiment is more broaden then in simulation, it will reduce the identification of absorption frequency, the slight changes of plasma density will be difficult to detect. The rf sheath effect can be support the phenomenon. In the experiment, using the RF-bias power to increase the plasma potential and finding the peak of spectrum is wider with the rf-bias power increasing, it is also confirm the rf sheath affect the plasma measurement. Developing new structure of plasma absorption probe by coating the dielectric on metal antenna to improve the bandwidth of resonance peak. According to the simulation result, the plasma absorption probe is not suitable for measurement in the high pressure and low-density plasma environment. Finally, the hairpin probe, which is the quarter-wavelength structure of resonant itself, be developed by simulation and experiment and the probe can measure the high pressure (~1 atm) and low plasma density (~2x109 cm-3). It is effective to measure environment the ALD and PECVD process.

並列關鍵字

Plasma diagnostic ； Plmsma absorption probe ； Floating hairpin probe

參考文獻

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