研究生: |
Selvy Uftovia Hepriyadi Selvy Uftovia Hepriyadi |
---|---|
論文名稱: |
氮化鎵元件與矽共舞 GaN Devices Dancing with Silicon |
指導教授: |
葉秉慧
Ping-Hui Sophia Yeh |
口試委員: |
徐世祥
Shih-Hsiang Hsu 蘇忠傑 Jung-Chieh Su |
學位類別: |
碩士 Master |
系所名稱: |
電資學院 - 光電工程研究所 Graduate Institute of Electro-Optical Engineering |
論文出版年: | 2021 |
畢業學年度: | 109 |
語文別: | 英文 |
論文頁數: | 144 |
中文關鍵詞: | GaN LED 、passive matrix 、Si substrate 、solder bonding 、via holes |
外文關鍵詞: | GaN LED, passive matrix, Si substrate, solder bonding, via holes |
相關次數: | 點閱:302 下載:0 |
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GaN-based passive matrix LED has been studied intensively for the last decade due to its potential applications. In this study, passive matrix GaN-on-Si LEDs with backside via holes were fabricated. The LED matrix was fabricated on a commercial GaN-based LED epitaxial wafer grown on a Si substrate. Then the backside of the Si substrate was selectively removed using deep reactive ion etching (DRIE) to form backside via holes. Further etching was also done to remove undoped GaN, then metal layers were deposited subsequently to form backside n-metal. Solder pastes and solder balls were used individually to fill via holes to bond on a Si wafer that has n-metal lines for passive matrix function and will be integrated with a Si-based driving/control circuit. In this way, LED wafer did not need to be flipped for bonding. Flux and silver epoxy were applied on the backside of the LED wafer to enhance the bonding strength.
The first trial of passive matrix LED fabrication did not work well with solder pastes because the air gaps or voids were formed in between solder pastes and n-metal inside the via hole. The wafer with no etching of undoped GaN had high resistance. In addition, LED devices were easy to break due to lack of mechanical support after substrate removal, so we re-designed the photomasks. Moreover, the LED emission spectrum showed that the peak wavelength and the bandwidth remained the same, indicating the spectral characteristics of GaN active layers after partial substrate removal was not changed.
In the second trial of passive matrix LED fabrication, solder balls were used to fill via holes instead of solder pastes. However, there occurred some issues that failed the experiments, such as oil contamination during DRIE, poor adhesion of solder balls with the last metal layer (Ti), and insufficient solder ball volume leading to insufficient contact area to metal layer in the via hole. We resolved the oil contamination problem by applying topside photoresist prior to backside processing to protect the topside LEDs from any contamination during the process. Suggestions for future work were proposed at the end of this thesis.
GaN-based passive matrix LED has been studied intensively for the last decade due to its potential applications. In this study, passive matrix GaN-on-Si LEDs with backside via holes were fabricated. The LED matrix was fabricated on a commercial GaN-based LED epitaxial wafer grown on a Si substrate. Then the backside of the Si substrate was selectively removed using deep reactive ion etching (DRIE) to form backside via holes. Further etching was also done to remove undoped GaN, then metal layers were deposited subsequently to form backside n-metal. Solder pastes and solder balls were used individually to fill via holes to bond on a Si wafer that has n-metal lines for passive matrix function and will be integrated with a Si-based driving/control circuit. In this way, LED wafer did not need to be flipped for bonding. Flux and silver epoxy were applied on the backside of the LED wafer to enhance the bonding strength.
The first trial of passive matrix LED fabrication did not work well with solder pastes because the air gaps or voids were formed in between solder pastes and n-metal inside the via hole. The wafer with no etching of undoped GaN had high resistance. In addition, LED devices were easy to break due to lack of mechanical support after substrate removal, so we re-designed the photomasks. Moreover, the LED emission spectrum showed that the peak wavelength and the bandwidth remained the same, indicating the spectral characteristics of GaN active layers after partial substrate removal was not changed.
In the second trial of passive matrix LED fabrication, solder balls were used to fill via holes instead of solder pastes. However, there occurred some issues that failed the experiments, such as oil contamination during DRIE, poor adhesion of solder balls with the last metal layer (Ti), and insufficient solder ball volume leading to insufficient contact area to metal layer in the via hole. We resolved the oil contamination problem by applying topside photoresist prior to backside processing to protect the topside LEDs from any contamination during the process. Suggestions for future work were proposed at the end of this thesis.
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