癲癇治療電子系統之研發及其動物實驗之驗證-子計畫七：應用於癲癇治療系統之雙極性電流刺激器電路設計( I )

Abstract

在癲癇治療系統晶片中，刺激器接觸到的等效負載依接點位置、接觸時間、和電極材質不同，負載阻抗為幾十 kΩ 到幾百 kΩ 都有可能，而一般刺激電流為數十 μA 到數百 μA，由此可知，在輸出點會有相對高壓產生，大於低壓 CMOS 製程可承受的 1.8V/2.5V/3.3V 電壓。因此，現有的電流刺激器都是以高壓製程來實作。而為了系統單晶片整合的需求，如果利用低電壓製程所設計的電流刺激器操作在高電壓的環境，電性過壓 (electrical overstress)、閘極氧化層可靠度 (gate-oxide reliability)、熱載子衰退效應 (hot-carrier degradation)、漏電流 (leakage current) 等現象將會發生。本子計畫將利用電路設計技巧，以低壓製程實作可承受高壓之雙極性電流刺激器，並考慮電路元件可靠度的問題，以應用於癲癇治療系統晶片。此外，在晶片生成後，在組裝、使用、拿取中，晶片都有可能遭受到靜電放電 (ESD) 的衝擊，使得晶片在未使用前就損壞。因此，依據雙極性電流刺激器的需求，設計出適用於雙極性電流刺激器的靜電放電防護電路，在本計畫中也是相當重要的一環。本計畫發展以積體電路與生物科技的結合為目標，研究成果將發表於國際研討會與國際期刊，創新的研發成果也將申請專利，提供並保護業界使用本計畫之研究成果。

In the epilepsy prosthetic system, the loading impedance of stimulus driver will vary from tens of kΩ to hundreds of kΩ due to different kinds of tissue location, implanted time, and electrode materials. The required stimulus current is about tens of μA or hundreds of μA, and then the output node will suffer the voltage level which is higher than the supply voltage (1.8V/2.5V/3.3V) in low-voltage CMOS process. Thus, the high-voltage processes were used to implement the stimulus driver. For the intelligent prostheses SOC applications, the stimulus driver implemented in low-voltage CMOS process will suffer the reliability issues, such as electrical overstress, gate-oxide reliability, hot-carrier degradation, and leakage current. This project will use the circuit techniques to design the high-voltage-tolerant biphasic stimulus driver in low-voltage CMOS process, and apply the biphasic stimulus driver to the SOC of epilepsy prosthetic system. The reliability issues will be considered in this design.After the chip is produced, the chip will suffer the impact of electrostatic discharge (ESD). Therefore, ESD protection for the biphasic stimulus driver is also an important issue in this project.The goal of this project is to combine the integrated circuit skill and biology technology. The research results will be presented in the international conferences and published in the international journals. Patents will be applied in this project in order to provide and defend the usage of this invention to the industry.