The size of the wafers on which the chips are made has not always been the same. Overtime these increased in size in order to be able to manufacture more chips per wafer. The current shortage again raises the possibility of increasing platelet size. But, is this a viable solution that can be done in the short term in order to solve the problem of shortage of chips today?
More chips with 450mm wafers
To understand how the transfer to 450mm plates for production would affect the production of the different chips, we are going to do a little exercise. For this we will take a hypothetical 15mm chip per side, fabricated under a fabrication node with an error rate of 0.1.
So we used an online tool, which tells us how many good and bad chips would come out on average in each wafer, to visually show you the result.
Using a 300mm diameter wafer, as can be seen, we will get 205 fully functional chips, discarding 59 of them, 8 of which would be partially constructed chips as they are on the edges that demarcate the area of chopped off. In contrast, by making the same chip with a 450mm wafer, the number of good chips would become 488, but a total of 136 would be discarded, of which 16 would be due to being on the edges. The yields which are the percentage of chips in both cases would be 80.19%, so in this regard, using a 450mm wafer is not an advantage regardless of chip size.
So what would be the benefit? The cost of 450mm wafers would be much lower than 300mm ones, which in theory would mean not only more chips and in theory cheaper chips. Unfortunately, this is not so and a number of additional issues need to be taken into account.
Problems adopting larger platelets
The idea of making a transition to the 450mm diameter input coin with the problem of the availability of silicon ingots from which the chips are made. These silicon ingots are built after a chemical process to achieve 99.9% purity, but not all silicon goes to these ingots and a much lower percentage than the 300 are made at this time. This affects the subsequent production of 450mm platelets.
It is important that a factory can print more chips on its 450mm wafers than its 300mm wafers in order to increase production so in advance it will need a sufficiently large amount of ingots. and that means more purified silicon. But, since we are talking about factories, they are all prepared for their machines to work with the 300mm inserts, so we end up having to not only set up an entire factory, but also develop new machines that adapt. to the new platelet size.
All these problems they would end up charging a premium on the chips, but in a much broader way, since for example the insert transport systems that exist throughout the plant are designed to move 300mm inserts. So even this detail should be updated by making changes at the whole plant level.
