Study on the Mechanism and Process Development of the Application of Germanium Nano-dot in Energy Storage Battery

• Main Authors: Chang, Chung-Lun, 張崇綸
• Other Authors: Leou, Keh-Chyang
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/6g3qk9

碩士 === 國立清華大學 === 工程與系統科學系 === 105 === In recent, Japanese companies developed a new structure of secondary cell, called “Battenice”, the output density and cycle life are better than Lithium batteries. This study will use a different process to produce the charge storage layer of battery, promising to produce a new type battery which can be combined with semiconductor products. The main procedure to produce charge storage layer in this study is to deposit SiGe film by PECVD, followed by oxygen thermal annealing treatment to oxidize Si atoms into SiO2, assemble Ge atoms to form nano-crystalline grains. Then, the physical properties and electrical characteristics of the charge storage layer are discussed. In order to investigate the effect of plasma environment on the deposition of SiGe film, the plasma spectrum was in-situ monitored using optical emission spectrum, OES. And the relationship between the specific spectrum and the characteristics of SiGe film was analyzed. The results show that the OES-ratio (Ge*/Si*) and the Ge content in the film have the same trend as the parameter change. The OES-ratio (Ge*/Si*) and the Ge content in the film show a downward and rise trend with the process power and RGeH4(≡〖GeH〗_4/(〖GeH〗_4+〖SiH〗_4 )) increasing respectively. It means OES-ratio(Ge*/Si*) exists strong correlation to the Ge content in the film. Then, OES-ratio(Si/SiH) and OES-ratio(Hβ/Hα) can be used to analyze the electron temperature in the plasma. When changing the power (50W to 100W) and RGeH4 (0.2 to 0.33), the above two OES-ratios change a little (Maximum change is less than 7%). Finally, H2 fulcher is used to analyze the electron density in the plasma. The results show that H2 fulcher increases with power and RGeH4, indicating that the electron density in the plasma also increases. So, effect of process parameters on Ge content and plasma characteristic can be understood by the OES analysis. In order to allow the Ge nano-dots formed after the film annealing to be effectively isolated from each other, the Ge content of the film is selected to be in the range of 30 to 40%, and the Ge content of the SiGe film deposited by the plasma parameter power of 100 W and RGeH4 of 0.2 is 34.61%. The Raman spectra of this film shows three specific peaks at 250 cm-1, 300 cm-1 and 420 cm-1, respectively, corresponding to the vibration modes are amorphous Ge-Ge, crystalline Ge-Ge and Si-Ge. It indicates that the film is consisting with a portion of amorphous and crystalline. Then, the Raman peak of amorphous Ge-Ge is significantly decreased after thermal annealing treatment (O2 /900 °C/20 min). This phenomenon represents the crystallization of the film. In the C-V measurement, a memory window, 2.5 V, and storage charge number density, 2.15×〖10〗^12 〖cm〗^(-2), are observed with applying 10 volt sweep range . And it is a clockwise type hysteresis, which means that carriers from the top electrode into nano-dots embedded in insulator. However, the battery which made by this charge storage layer, the charge and discharge characteristic is similar to a resistance component, and no storage effect.