There have been lots of technical advances in the fileld of semiconductor industry for the last dacades ever since DRAM and NAND were invented and commercialized. Meanwhile, form factor was changed from 8F2 to 6F2 in DRAM, and the concept of 3D stacking was adopted in NAND flash memory. Furthermore, EUV tool has been adopted and are being successfully used to make the fine pattern in logic and DRAM as well. And also, it has been very long since ALD was taken as a new advanced depostion technology to meet the need for excellent conformality. But all these new process technologies couldn’t have been possible without the advances in process materials such as advanced photo resist, precursors, functional chemicals and CMP slurries. Recently, those process materials are beginning to open the new possibilities for the innovation of process integations, resulting in cost reduction and giving an extra performance to the process tools. In this talk, the role, the current issues and future challenges will be discussed focusing on the process materials in semiconductor industry.
Starting from photo resist, thin and etch resistant resist has been cosistantly required to suppress the pattern collapse and wiggling during the patterning process. Since the EUV was adopted in DRAM and Logic, high sensitivity EUV resist is now being intensively explored to obtain low DtS as well as good CD uniformity to make the best use of the enomoursly high-priced EUV tool in a cost effective way. For the sake of that, even metal-containing resist is also being tried for high quality patterning. Additionally, thick KrF resist is also required at 3D NAND flash memory with the increase of ON stack and especially for the new platform to be. And for the future, the new concept of PR based on small sized polymer will be worth trying and dry type developer would be also necessary to keep the pattern stable without collapse or wiggling.
With regard to the wet chemicals and CMP slurries, advanced functional chemicals are getting more and more important rather than convetnional cleaning chemicals that are used after etch and CMP process. W or Mo recess chemical in 3D NAND would be that very case. Those chemicals should assure the good uniformity in terms of recess amount in the vertical direction. Most of all etch and CMP prcesses need post cleaning steps to clean the residue, but during that, some unwanted part of the surroundings is apt unavoidably to be removed deteriorating the device proformance in the end. Therefore, special clean chemical will be also needed to minimize the unwanted film loss as well as residue removal. When it comes to the slurry, the shape of the abbrasive particles consistently has been changing from sharp and pointed to the rounded one by adopting colloidal synthesis to suppress the scratch during CMP. The size of the abrasive particle tends to get smaller but slurry is required to make up the decreased removal rate by properly regulating components within slurry. With the change of material to be polished such as Mo or Carbon, new slurry for those new materials will be a new drive for CMP related materials.
Precursor and some functional gases have been contributing to the quality improvement or deposition modication of functional materials such as high-k materials in DRAM. As always, there should be more technical areas, in which precursor and gas will be able to play an important role in ASD(Areal Selective Deposition) or ALE(Atomic Layer Etching) process.
Since process materials needs to be considered from the operation of FAB line unlike the process tools, it must be managed well from the aspect of consistent quality control and risk management of supply chain and safety. In the past, process material used to play a simple and supporting role in the process and tools as well. But now, it is becoming a time for the process materials to play a more active role in cost reduction and risk management as well as providing technology for semiconductor industry. Especially, new process materials are also required to meet the needs for low carbon emission during the process and safety issues from the using PFAS containg materials that are hazardous to human body. Way of doing work needs to be also changed in a way that R&D activities have to be shifted to the earlier engagement. And plus, the collaboration between device maker and process material supplier shoud be much closer and earlier than before so that the developed materials can be successfully adopted at a targeted process and a tool for it. As the material supply chain has been becoming very unstable since corona pandemic and US-China trade conflict, it needs to be managed with a good predictability and balance as well in order for consistent and stable supply in case of unexpected issues at a supply chain.
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