Progressive defects caused by crosstalk between mask fabrication processes

Most of defects generated in mask fabrication processes have been mainly created during each unit process. It becomes more important to detect and remove smaller defects on mask as pattern nodes keep shrinking. Each unit processes are getting not only more challenging to sustain mask quality and defect level but also more influencing on other processes for smaller pattern nodes. New type of defects based on such influences (crosstalk) between different processes is starting to emerge, which is requesting for a revision of defect reduction strategy because dealing with crosstalk defects is directly related with quality and TAT of mask manufacturing. It is relatively difficult to properly understand root-cause or working mechanism of defects generated by crosstalk between different processes. This is because interaction between different processes from defect generation perspectives has hardly been studied. In this paper, we introduce emerging progressive defects created while etched masks are undergoing cleaning process or subsequent events of moving to next process or temporary storage. We will investigate how etch gas residues on mask surface remaining after etching process interact with cleaning chemicals or moisture from subsequent process or environment to trigger defect generation and its growth. We will also examine effects of POD outgassing on generation of crosstalk progressive defect. Based on this understanding, appropriate solutions to mitigate defects caused by crosstalk between mask fabrication processes will be proposed. It is believed that new type of progressive defects caused by crosstalk between different mask fabrication processes will be more flourishing in the near future where mask blank materials, mask manufacturing processes, and chemicals need to diversify in order to meet much tighter specifications of mask quality. Therefore, it is very crucial to have right understandings on the interactions between various processes and eradicate possible root-causes of defect generations.