Large-size Panel Lcd Array Process, The Metal Molybdenum Etching

Recent years, the liquid crystal display (LCD) has been taking the place of the normal CRT (Cathode Ray Tube) display rapidly. In order to meet the needs of the market and increase the production, the manufactures have put many patents about the methods to simplify the LCD process. Samsung put a patent about a four-count-mask (4mask) process, which is now been used by many manufactures. The work of this paper is based on this patent. And this paper talks about the key part of the 4mask process, the multi-step etching on the 1.1m×1.3m glass substrate. It involves four steps: the active etching, the photo resist etching, the molybdenum etching and the n plus layer etching.Among the four steps, the second and the fourth were new processes comparing with the normal five-count-mask (5mask) process. The goal of the research was to develop a series of process parameters to make the two new steps operate well. First of all, an enumeration experiment and an orthogonal matrix experiment were needed to find the general trend between the various parameters. The orthogonal matrix experiment had three factors and three levels, so the orthogonal table L9 (34) should be chosen. The result of the orthogonal matrix experiment showed the relationship between etch rate, uniformity and the parameters power, pressure and the gas flux. So from the result, primary process parameters could be got. And then, the scan electronic microscope (SEM) was used to observe the profile of the substrate. From the photos taken by the SEM, whether the selectivity was good could be jugged easily. The Mac/Mic equipment was used to see whether there is some remain material. At last, the Electric-Property-Measure (EPM) equipment was used to test the electric property of the thin film transistor (TFT), and to make sure that the transistor could work. The four steps were sequential and uninterrupted, so the infections among the steps were serious.In the ashing process, the oxygen atom was the reacting particle, and the etch rate directly related with the concentration of the oxygen atoms. The roughness of the channel surface of the TFT was very important, and it infected the off state current of the TFT obviously. The etch rate of the molybdenum was difficult to get higher because of the bad uniformity and the bad selectivity to SiN.This paper shows a series of process parameters at the end of the article. These parameters can make the array process just work, but not very well. In order to improve the yields, the etching uniformity of molybdenum should be better.By using the results of this paper, BOEOT's mass production productivity increased 30% in last December's statistic.