On 28/08/06, Takeshita K <[EMAIL PROTECTED]> 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.

-- 
Rob Studdert
HURSTVILLE AUSTRALIA
Tel +61-2-9554-4110
UTC(GMT)  +10 Hours
[EMAIL PROTECTED]
http://home.swiftdsl.com.au/~distudio//publications/
Pentax user since 1986, PDMLer since 1998

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