Are you talking about a Step and Repeat Machine? * That takes a photograph of the IC artwork, and reduces it in size, then prints 4 copies of the artwork 1/2 size. Then it does it again and you get 16 copies 1/4 size, again and you have 64 copies 1/8 size, etc. When you get the IC's down to the desired size you use the image to photo etch the IC's onto the wafer. I can see how there may be a minimum size limit, but not how there can be a maximum size limit. After all the original image is many times larger than the wafer. Of course there may well be a size limit on the automatic cutters that cut the wafers into individual IC's.
*My knowledge of this is ancient, they undoubtedly use digital imaging now, but the principle should be the same. I could do some research on modern IC production methods. But why? No one is going to hire me to design IC's for them <grin>. -- graywolf http://www.graywolfphoto.com http://webpages.charter.net/graywolf "Idiot Proof" <==> "Expert Proof" ----------------------------------- Takeshita K wrote: > > On 28/08/06, Takeshita K <marinerone at gmail.com> wrote: > > >> My understanding is that the current size is the one which produces > >> the most yield under the current process using the stepper. > >> It's not the choice by the camera makers or sensor makers etc. > >> I used to have a link which explains this, but lost it. Will dig it > > > I'm not familiar with the term "stepper:" in this context. Yield > > factors make a big difference to sensor manufacture affordability > over > > other general semiconductors which don't often exceed 10x10mm. The > > shear expanse of a sensor area means that due to the lower numbers of > > chips per silicon wafer (for all intents a fixed cost) any wafer > > contaminants will render a larger portion of the wafer to waste. And > > since wafers are circular (Sony now produced 300mm diameter wafers) > > the larger the sensor produced the more the waste. > > > The tech used to produce the sensor used in the Kodak 14MP FF meant > > that there were only 11 full sensors per wafer (approx 125mm > diameter) > > assuming a 100% yield, no wonder they were expensive. Think how many > > 24x16mm sensor could be shoehorned into a 300mm diameter wafer vs > > 36x24mm sensors, it's not a linear correlation. > > My mail on this subject bounced, and that's probably because I > inadvertently used a different address. > If it's duplicated somehow, my apology. > Anyway.... > I have not dug into any specific site yet, but my memory goes like this. > > This is indeed a "stepper' issue, and not about the usual yield per > wafer argument. > APS-H size sensor is the maximum size that can be obtained by a one > shot exposure in the lithography process using a stepper. i.e., it's > a stepper-driven size limitation. Anything smaller than that indeed > becomes a yield issue, i.e., max obtainable numbers per circular wafer. > > Incidentally, Nikon is the world largest maker of the high > performance stepper which Sony also uses. > > I thought I saw an article somewhere that Canon developed a process > (or probably stepper) which can make a FF size sensor in one shot > exposure, thus significantly reducing the cost of such sensor, hence 5D. > > Nevertheless, my understanding is that the cost of the FF size > sensors is at least 10 times (or more) that of the APS sized one, > and this gap is not going to narrow any time soon. > > I also saw some articles that both Nikon and Pentax, particularly > Nikon, said that if the cost of FF sensors come down sufficiently to > make any commercial sense, and if the lens/sensor performance could > be reasonably conformed to such a sensor, there is no reason not to > produce FF machines. > > But most of experts are predicting that APS size sensor has already > become a de facto standard, and with the performance of APS sized > sensor being rapidly increasing, they do not see any pressing need to > rush the FF machines. > > We'll see. > > Cheers, > > Ken > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
