Implications of Transition to 450mm on Gases for Semiconductor Manufacturers
The transition to larger 450mm wafers is necessary to combat the increase in costs per transistor associated with continuing on the Moore's Law trajectory. The manufacture of 450mm wafers, which is being hotly debated in the industry, is expected to occur near the end of the decade, when it will intersect with the 7nm-or even 5nm-process node.
To achieve increasingly diminutive geometries, the semiconductor industry is seeing a convergence of larger wafer size, EUV, and multiple patterning, which all lead to substantially increased consumption of critical gases such as N2, H2, He, SiH4, and more.
Which brings us to this question: What are the implications of this transition on the gases for semiconductor manufacturers? Larger wafers will require the use of larger tools, which will need more gases. A 450mm wafer has 2.2 times the surface area of a 300mm wafer. Therefore, deposition gases and precursor flow rates will have to be scaled up. The tools will also be larger and require much larger vacuum pumps to evacuate them. For some critical gases, these increased requirements will change the means of delivery and will significantly impact the facility planning for new 450 mm fabs.
Let's consider a few critical gases and how they will be impacted.
Nitrogen: Nitrogen is by far the highest volume gas used in semiconductor production. It is used as a purge gas in almost all the process tools and is also a process gas. A high-volume fab today typically uses 15,000-30,000 Nm3/hour of N2, usually provided by an on-site generator. New 450mm fabs will require higher N2 flow; in order to do that cost effectively, larger on-site plants will be needed. For example, Linde has developed an efficient 50,000 Nm3/hour plant and installed the first one in Taiwan. These will be the workhorses of 450mm fabs in the future.
Hydrogen: The usage of H2 in fabs has been growing rapidly since the introduction of FinFets due to the increased role of epitaxy. The introduction of EUV will further dramatically increase the use of H2 in fabs. Add to this the larger wafer size and there will be a very large increase in H2 usage. Hydrogen at most fabs today is supplied via compressed gas in trailers. However, for 450 mm fabs it is clear that on-site generators will be required. Cost-effective on-site generators from 300-2000m3/hour are available from companies such as Linde; manufacturers will have to consider the infrastructure needs of power and natural gas in order to have these on site.
Helium: Helium is a non-renewable resource used primarily for cooling wafers. Larger wafers will need more helium to cool. Helium supply has recently been quite tight and there is much interest in possibly recycling the unused helium. At 450mm, this will become even more important. Linde has extensive experience in gas recycling and has designed helium recovery systems that can be used by semiconductor fabs.
Nitrogen trifluoride: With the increased use of gases, environmental concerns are magnified. NF3 is a very potent greenhouse gas and is used in large volumes for chamber cleaning. 450mm fabs offer an opportunity to transition away from NF3 completely by switching to molecular fluorine (F2) gas, which is more effective at cleaning while at the same time having a zero GWP.
Chip makers will benefit from considering these dynamics and beginning to work with suppliers at these early stages in the 450mm transition to ensure readiness to move with and satisfy the demands of the market.
