砷化鎵及磷化銦異質接面雙載子電晶體之銅金屬化製程研究

Abstract

這篇論文為研究砷化鎵(GaAs)及磷化銦(InP)異質接面雙載子電晶體(HBT)之銅金屬化製程，內容包含了使用氮化鎢(WNX)為擴散阻障層應用在磷化銦鎵/砷化鎵(InGaP/GaAs) HBT上，和不使用金材料而完全銅金屬化的InGaP/GaAs HBT，以及使用非合金材料的歐姆接觸和以鉑作為擴散阻障層應用在InP HBT上。 在銅的內連接導線方面，本篇使用濺鍍的方式分別成長氮化鎢和銅金屬材料做為擴散阻障層和內連接導線應用在InGaP/GaAs HBT上，從掃描式電子顯微鏡(SEM)、X光繞射(XRD)、歐傑電子光譜(AES)和片電阻(sheet resistance)的結果，銅/氮化鎢/氮化矽(Cu/WNX/SiN)和銅/氮化鎢/金(Cu/WNX/Au)的結構分別在550℃和400℃加熱後都還很穩定，並將元件施以55小時，高電流密度140 kA/cm2之電流加速測試(current-accelerated test)，其電流增益並沒有下降，仍然超過100。另外，也將元件施以250 oC 25小時的熱處理，元件特性也並沒有明顯的改變。 之後我們更進一步利用鉑做為擴散阻障層成功製作出不使用金材料而完全銅金屬化的InGaP/GaAs HBT，使用鈀/鍺(Pd/Ge)和鉑/鈦/鉑/銅(Pt/Ti/Pt/Cu)做為n型和p型的歐姆接觸，使用鈦/鉑/銅(Ti/Pt/Cu)做為內連接導線金屬，從X光繞射和片電阻結果顯示Ti/Pt/Cu結構在350℃加熱後都還很穩定，將元件施以24小時，高電流密度140 kA/cm2之電流加速測試，其電流增益並沒有下降，另外，也將元件施以250 oC 24小時的熱處理，元件特性只有些微的改變。 最後我們更將銅製程應用在InP元件上，使用非合金材料鈦/鉑/銅(Ti/Pt/Cu)和鉑/鈦/鉑/銅(Pt/Ti/Pt/Cu)做為n型和p型的歐姆接觸，以及使用Pt做為擴散阻障層，成功製作出不使用金而完全使用銅金屬化的InP HBT。從歐傑電子光譜結果顯示Ti/Pt/Cu結構在350℃加熱後都還穩定，將元件施以24小時，高電流密度80 kA/cm2之電流加速測試，其電流增益並沒有下降，也將元件施以200 oC 3小時的熱處理，元件特性幾乎改變。由以上的結果顯示，我們可以成功的製作出銅製程和完成電性研究，必且是第一次發表砷化鎵及磷化銦異質接面雙載子電晶體之銅金屬化製程。

In this dissertation, copper-metallized GaAs and InP heterojunction bipolar transistors (HBTs) were studied. The developed copper metallization technology for HBTs include interconnect copper metallization of InGaP/GaAs HBTs using WNX as the diffusion barrier, gold-free fully Cu-metallized InGaP/GaAs HBTs, and gold-free fully Cu-metallized InP HBTs using non-alloyed ohmic and platinum diffusion barrier. The WNX and Cu films were deposited sequentially on the InGaP/GaAs HBT wafers as the diffusion barrier and interconnect metallization layer respectively using the sputtering method. As judged from the data of scanning electron microscopy (SEM), X-ray diffraction (XRD), Auger electron spectroscopy (AES), and sheet resistance, the Cu/WNX/SiN and Cu/WNX/Au structures were very stable up to 550℃ and 400℃ annealing, respectively. Current accelerated stress test was conducted on the Cu/ WNX metallized HBTs with VCE=2 V, JC=140 kA/cm2 and stressed for 55 hours, the current gain (b) of these HBTs showed no degradation and was still higher than 100 after the stress test. The Cu/ WNX metallized HBTs were also thermally annealed at 250℃ for 25 hours and showed no degradation in the device characteristics after the annealing. Gold-free, fully Cu-metallized InGaP/GaAs HBTs using platinum as the diffusion barrier have also been successfully fabricated. The gold free HBTs use Pd/Ge and Pt/Ti/Pt/Cu as n+-type and p+-type ohmic contact metals, respectively, and use Ti/Pt/Cu as interconnect metals with platinum as the diffusion barrier. The Ti/Pt/Cu structure was stable after annealing up to 350℃ as judged from the XRD and the sheet resistance data. A current-accelerated stress test was conducted on the device with a current density JC=140 kA/cm2 for 24 h, the current gain of the device showed no degradation after the stress. The devices were also thermally annealed at 250℃ for 24 h and showed little change. In addition, gold-free, fully Cu-metallized InP HBTs using non-alloyed Ti/Pt/Cu and Pt/Ti/Pt/Cu ohmic contacts and platinum diffusion barrier have been successfully fabricated. The InGaAs/Ti/Pt/Cu ohmic structure used in this study was very stable after annealing up to 350 ℃ as judged from the Auger depth profiles. A current-accelerated stress test was conducted on the device with a current density JC=80 kA/cm2 for 24 hours, and the current gain showed no degradation after the current stress. The devices were also thermally annealed at 200℃ for 3 hours and showed almost no change in the electrical parameters after the heat treatment. Overall, we have successful developed the copper metallization process for the GaAs and InP HBTs and have reported for the first time the fabrication and electrical performance of the Cu-metallized GaAs and InP HBTs.