利用雙加熱檢測系統進行靜態隨機存取記憶體故障分析

Abstract

本論文在探討利用雙加熱量測技術(Dual Thermal Measurement, DTM)來進行靜態隨機存取記憶體(SRAM)元件中溫度對漏電流影響的研究。實驗中利用紅外光阻值變化偵測儀(Infrared Optical Beam Induced Resistance Change, IR-OBIRCH )結合恆溫控制系統組合成雙加熱檢測系統，利用此系統對試片進行加熱，偵測元件故障熱點位置，並利用相關分析技術對故障熱點進行分析，達到瞭解故障構因，幫助達到元件結構設計之最佳化。 一般MOSFET元件給予不同程度之偏壓時,元件會有電流(電阻)變化之特性，若在不同的溫度條件之下給予不同的偏壓可以觀察到元件因為熱而產生的微量電流變化，本研究即是藉由改變元件工作電壓以及工作環境溫度條件來觀察電流變化，將此一特性應用在半導體故障分析的電性定位上。研究中使用經測試後，判定為漏電失效之系統晶片(System-on-Chip，SoCs)元件進行實驗，利用溫度與電流的變化來進行故障熱點定位，並進而探討其故障構因，最終希望能增加半導體產業故障分析的成功率並協助相關製程的開發與應用，使產品良率得以提高。

In this thesis, we developed a dual thermal measurement (DTM) technique to study the dependence of the leakage current of a static random access memory (SRAM) on the temperature. Infrared optical beam induced resistance change (IR-OBIRCH) inspection system was combined with a sample heating system to form a DTM system. We used the DTM to accurately locate defect areas in the device and investigated the cause leading to the device failure. Under light illumination, the temperature in a metal oxide semiconductor field effect transistor (MOSFET) increases, and the temperature increase changes the device current, whose magnitude depends on the bias voltage applied to the MOSFET. We studied the change in the device current as a function of the bias voltage and the ambient temperature. The DTM system was used to analysis system-on-chip (SoCs) devices that were determined to be failed in the leakage current test. By properly controlling the biased voltage and the sample temperature, we demonstrated the successful identification of the hot-spot due to defects in the devices, and the capability of the DTM technique for the study of failure modes of an SRAM device. The development of the DTM can produce a better understanding of the failure mechanism of SoC devices and thus to improve the production yield.