| Summary: | 碩士 === 國立成功大學 === 電機工程學系碩士在職專班 === 106 === Plasma fabrication, which is one of the most well-known and utilized technology in the present semiconductor industry. The advantages of this technology are capability of fabricating minute device and ability of control the direction of the ions. However, as the dimension of the device shrinks, disadvantages of this technology start revealed and show their importance, such as charge build up effecting etched profile, charging damage degrading electrical characteristics and ultra violet (UV)/vacuum ultra violet (VUV) photons irradiation effecting electrical performance. In order to conquer the problems, a new semiconductor fabrication technology has been developed, neutral beam system. Neutral beam system is an extended application of plasma fabrication, the key of this technique is to neutralize the ions before reacting with substrate. The main purpose is to avoid plasma damages caused by charge accumulation and UV/VUV irradiation effecting both physical profile and electrical performance of the device.
In this thesis, the purport is to discuss the neutral beam system applied in etching process. Through fabricating high-k/metal gate capacitor, we would like to verify the ability of improving conventional plasma fabrication defect. In this work, the experiment is divided into two parts. The first part is focusing on the effect of ultra violet generated by traditional plasma to the device electrical characteristics, and verifying whether the neutral beam system is capable of improving the UV/VUV damage or not. First of all, the author used the optical emission spectroscopy (OES) directly to measure the emission photons generated by ICP and NBE respectively; the purpose is to evaluate the intensity of photons on the basis of UV/VUV magnitude. Second, in order to understand the damage to the device caused by UV/VUV and the diversification of electrical characteristics firsthand, the author set the pre-fabricated capacitor in the ICP and NBE system to absorb the irradiation of UV/VUV respectively. For making the information accurately, the MOS capacitor used in the first part was fabricated by lift off process; any plasma process was avoided during fabrication lest effect the reliability of the experiment data. The result shows that the photon intensity measured in ICP is far stronger than in NBE, which proves that the irradiation dosage of UV/VUV in ICP is larger than in NBE. In the device electrical performance part, the characteristics of capacitor placed in ICP system show further degradation compared to the other placed in NBE. Base on the above result, in a nutshell: (a) The UV/VUV generated by plasma fabrication does indeed effect the device performance. (b) The neutral beam system does possess the potential to reduce the damage of UV/VUV photons. Finally, in order to agree with the interest of industry, the author made the capacitor through annealing process in the atmosphere of forming gas which is N2+H2, and observe the recovery of the damaged device.
The second part of the experiment is fabricating silicon germanium based metal-oxide-semiconductor (MOS) by neutral beam etching (NBE) and inductively coupled plasma etching (ICP) respectively; the electrical performance of the capacitors under different etching mechanism are analyzed, and the difference in characteristics such as flat-band voltage shift, oxide trapped charge, interface state density and leakage current are also compared. The results show the characteristics of MOS capacitor fabricated by ICP are inferior to those made by NBE, which proves the neutral beam system is capable of improving the damages induced by conventional plasma system.
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