The manufacture of modern flat panel displays involves the use of advanced high technology processes and materials. Production of TFT-LCDs (Thin film transistor liquid crystal displays) involves the merging of traditional Si semiconductor processing technology with glass processing and fine chemicals.
This application note focuses on the use of TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) for the analysis of residue formed during a TFT manufacturing step. TOF-SIMS provides highly specific chemical information (both atomic and molecular) from the top 10-30Å of a surface.
In this case, circular defects filling almost whole cells were found to be present during inspection of the display. A typical area of the TFT structure is shown on page 2. Each cell is about 100µm wide. The defects were only visible when liquid crystals were present within the structure and the defect positions were noted at that point. The defects were suspected to be organic in nature.
TOF-SIMS data can be displayed as either ion images or as mass spectra. The images below show the lateral distribution of selected species on a TFT surface. Mass spectra show the specific molecular and atomic species present in a particular region within the image, in this case, from the defect.