Why does the BJT Fabrication process less used and more costly than Mosfet?
A few years ago, bipolar transistors were bigger, harder to manufacture and their circuits tended to use more electricity. The main thing that has kept bipolar active is that mos has been considered intrinsically slower. after a better design, the problem of speed was solved, mos took off like a rocket and never looked back. Getting a billion bipolar transistors on a reasonably sized processor might not even be possible in theory, and certainly not in practice.
technologies are a decade apart BJT is generally considered clumsy and outmoded and MOSFET as its successor. Bjts will never lick mosfets in amplifier circuits and processors. as a current-controlled device, it always consumes energy, while (in case of leakage) it only draws power during switching. there is no continuous way from door to source or from door to drain.
and the much faster switching speed of the fet, combined with high gate impedance and voltage control, make it the king of high-speed, low-power applications.
but the modest bjt still holds in high-gain, low-noise applications.
The more you do something, the less expensive it is. this is called economies of scale. the bjt have seen their day come and go. most applications can now use fet technology. A so obsolete and less used technoloy is also manufactured by obsolete technology. it is more expensive to maintain and update is not usually worth the cost. rising costs and declining demand mean that they will eventually move in the direction of the vacuum tube and the magnetic amplifier. some niche markets will still have demand, but they will pay a premium.
just a thought / random question was triggered by writing my . I think I remember that during the manufacture of the bjt, many toxic waste was generated because of the high doping of the substrate. if anyone could check it, it could also be an additional cost for manufacturing the bjt.