Researchers at the Imec technology institute still see significant obstacles to the use of euv technology. If these are not overcome, the 7nm production will become a so-called half node, making the chips considerably more expensive to produce in that process.
The researchers announced at the Imec Technology Forum that they are optimistic about the use of euv for 7nm production, but there is still doubt about the extent to which there is still doubt, EE Times writes. Immersion lithography is used for the current nanometer production process, but chips have to be exposed through the machines in more and more steps in order to get smaller lines on the wafers. As a result, times and costs increase. The euv machines must use light with a wavelength of 13.5nm, with which the small structures can be applied to wafers in a single step, for which current immersion machines require several steps. According to Imec, 34 lithography steps are required for 7nm via immersion and 9 via euv.
However, ASML’s euv machines are not yet ready for mass production. To use them effectively, a number of improvements are needed, according to imec researchers. The light source must be upgraded to 180W, where ASML now comes to a maximum of 110W. Furthermore, the systems must be able to function 80 percent of the time; now that is on average 50 to 60 percent. However, ASML reported that a customer with its NXE 3300B machine had achieved 82 percent uptime for a week and should be within reach of 86 percent by the end of this year.
In addition, production must also increase from 70 to 80 wafers per hour now, to 200 wafers per hour. The latter is the speed at which current immersion lithography machines can illuminate the wafers. ASML and its customers do not have a long time to get the machines ready. They should be ready for production in 18 months, otherwise the manufacturers will start 7nm production without EUV, says An Steegen of Imec’s research branch for process technology: “In that case 7nm will probably become a half node, not a full shrink”. The euv machines would then partly be used for the node. Certain critical layers are then produced via euv. Processes beyond 7nm will likely require other technologies to be used, meaning that euv may only last for a single node. Incidentally, Imec is already working on other techniques for transistors that should follow the current finfet technology.
According to Steegen, it is also questionable whether the costs per transistor will decrease for all fabs in 10nm production. Many manufacturers already indicated that the cost per transistor for 20nm and 14nm/16nm production had risen, but this was not the case for Intel. However, ASML announced that it will deliver an immersion lithography machine that can handle 275 wafers per hour by the end of this year, which should cut costs.