Study on defect reduction for high aspect ratio etch process
Increasing data needs much larger memory capacity. One of the Flash Memory Solution is Vertical NAND (V-NAND) Flash Memory. In order to fabricate this device, a high aspect ratio hole must be made in the channel hole through the etching process after multilayer thin film deposition. In order to obtain high aspect ratio etch, process condition should have high RF power, high flow rate of polymer gas, and long process time. This harsh etch condition results in high ion energy and lots of polymer production. It can create defects like fluorocarbon polymer and arcing. In this study, we studied arcing mechanism. Here we defined various margins for arcing-free and optimized the focus ring. And we improved pumping conductance for polymer discharge. This study removed defects and obtained arcing-free during V-NAND etch process.
Study on Wafer De-Chuck for High Aspect Ratio Etch Process
Higher aspect ratio feature etch is required with the increase of the layer count in 3D NAND technology. The arcing frequency in high aspect ratio etch process increases because charge accumulates due to the high power and more polymer deposition in the process. Thus, it is essential for the etching tool configure optimization to avoid arcing occurrence. In this study, we found that the helium detection for De-chuck charge release has high risk of arcing, while the soft-lifted pin charge release detection has wider window in avoiding the arcing happening. To acquire additional margin, the De-chuck parameters are optimized for healthier mass production.
An Ultrasensitive Analytical Method Based on Chemiluminescence Sensing Electrochemical Parallel Catalytic Reaction Event
An ultrasensitive electrochemiluminescence (ECL) method on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed for improving ECL analytical characteristics using vanadate(V) as a representative. Vanadate(V) could be electrochemically reduced to generate vanadate(II) which could be chemically oxidized by potassium periodate to regenerate vanadate(V) and give parallel catalytic wave effect. Then, the reduced product of potassium periodate could react with butyl-rhodamine B to emit a sensitive chemiluminescence signal. The chemiluminescence intensity was correlative with vanadate(V) concentration. The investigation on the electrochemical reaction rate constant (k0) confirmed that the speed of electrochemical reaction was faster than that of the subsequent chemiluminescence reaction. The possibility of the combination of electrochemical parallel catalytic reaction with chemiluminescence signal sensing was proved. The similar ECL behaviors could be observed at zirconia nanowires-Nafion modified electrode. Because of the separation and enrichment effect of the modified electrode on vanadate(V), the selectivity and sensitivity was further improved greatly. Based on these findings, a new concept on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed and an ultrasensitive ECL method for the determination of vanadate(V) was developed at zirconia nanowires-Nafion modified electrode. Under the optimum experimental conditions, the ECL intensity was linear with the concentration of vanadate(V) in the range of 2.0×10−12 mol/L–2.0×10−10 mol/L. The detection limit was 8.0×10−13 mol/L, which was more than 6 orders of magnitude lower than that observed by electrochemical current transduction for electrochemical parallel catalytic reaction at zirconia nanowires-Nafion modified electrode.