Dry Etching Of Phase Change Material And Micro-fabrication Of Phase Change Memory

Phase change random access memory (PCRAM) is one of the promising candidatesof the next generation memory to replace Flash, due to its non-volatility, high speed, highdensity, high reliability, anti-radiation and compatibility with CMOS process.Micro-fabrication is a key factor when it comes to the industrialization of PCRAM. Astable and reliable micro-fabrication guarantees a high quality PCRAM device. Microprocesses with high controllability, uniformity and reproducibility are essential in thelarge-scale manufacture of PCRAM.This thesis first studies the dry etching of phase change materials. InductivelyCoupled Plasma etching (ICP) with high controllability and high uniformity is adopted toetch the phase change materials such as Ge2Sb2Te5and superlattice with different periods.The etched films are analyzed by microscope, surface profilometer and atomic forcemicroscope. The process of etching is optimized and high etching speed, high uniformityand good etching morphology are achieved.Based on the research above, the dry etching of phase change materials is integratedinto the fabrication of PCRAM cells then.“T” type PCRAM cells with different phasechange materials are fabricated using etching process and lift off process respectively. Thedifficulties in each process are summarized and solutions of them are given. The testingresults of the cells show that the cells fabricated by etching and lift off process both worksuccessfully. And the PCRAM cell which adopts etched superlattice as phase changematerial has a phase transition voltage of1.9V, the operation current of8μA and the fastestreset operation of it costs only500ps. The dry etching process is integrated into the microfabrication of PCRAM cells successfully and it paves the way for the miniaturization andindustrialization of PCRAM.