1. Purpose of the gate
A shrink, a layer or bits per cell step, or a derivative is approved with its cost per bit case and its requalification scope.
A shrink saves cost on every wafer for the rest of a generation's life, but it costs engineering, masks, qualification and customer effort. The review checks that the saving is worth that cost given the generation's remaining life, and that the requalification scope and customer impact are understood before work starts.
Customer impact deserves care. Some customers will need to requalify a changed part, which takes their time; a shrink that arrives without warning damages the relationship.
The requalification scope should be set from a written comparison, even at this early point. Reviewers want to see which parts of the cell, process, design, test and package will change, which reliability mechanisms those changes could affect, and therefore which stresses must be repeated. A scope set by habit tends to be either too thin to satisfy customers or too heavy to pay back.
Reviewers also confirm the notice plan. The notice period agreed with customers sets the earliest date the changed part can ship to them, and that date belongs in the business case. Lead customers who must requalify are named, with the samples and support they will need.
Finally, the review considers the effect on capacity. A shrink often runs in the same fab as the original, so its development lots and its ramp take capacity from a product in volume, and the plan should show how that is managed.
The review is clearer when it compares options side by side: a die shrink, a layer or bits per cell step, a derivative, or no change and a faster move to the next generation. Each has a cost per bit, a schedule, a risk and a customer impact.
10 more sections for registered members.