the temperature is high suspected during annealing. I have NPN transistor for BICMOS circuit. The delta feedback resistance if high. suspect the high delta feedback resistance is due to annealing process
Dear Izzati,
your question is simply too general, if one does not precisely know what is your system. Geometry , contacts, materials, fabrication of your NPN transistor etc. In general, these semiconductor "elements" are rather temperature sensitive and the whole range of annealing effects can take place, starting from in-diffusion of the metal contacts into your PNP transistor, the changes in your p-n-p interfaces, formation of un-wanted deep levels, but possibly also some beneficial effects.
In order to answer/comment on your statement concerning "delta feedback resistance", you have to explain to me first what it is.
With best regards
Petr
Annealing is routinely considered to happen at high temperatures. Typically only for very short times as all types of diffusion (including metallization into the semiconducting structures) are sped up significantly. Thus it could be that your transistor(s) are already gone...
Regarding 'delta feedback resistance': never heard this term before so please explain.
May be he is using Optimization technique (CAD tool may be tcad Synopsys) , to see the effects of annealing !!
He wants to check the temperature variants and its effect on semiconductor surface (varying in regions ). If sheet metal concept is applicable then the resistivity variation upon unequal temperature spreading at equilibrium (at the end of the process ) or intermediate values for updating in steps of temperature , affecting BiCMOS .
BiCMOS -> CMOS + Good aspects of BJT
Annealing generally helps with lowering the contact resistance. However, if done too long it will : (a) cause diffusion of dopant impurities such as Zn which in turn can short the device; (b) cause annealing of proton-implanted regions (for current blocking in specific device areas) which in turn will wipe out current blocking and will significantly decrease the device efficiency.
The semiconductor resistance will be lowering with heating. It’s a common rule. Very important reporting the temperature of annealing for some discussion in detail of your question.
The semiconductor material have temperature dependent resistance (NTC i.e negative temperature coefficient of resistance ). This may also disturb the doping concentration of your device and also affect the performance of your device.
The contact resistance usually decreases with temperature and the time of the semiconductor exposure to the temperature. However, there is a minimum temperature below which the resistance doesn't change, no matter how long the semiconductor is exposed. Conversely, at very high temperatures the exposure should be short ( 30 sec to 1 minute) to avoid degrading the semiconductor-material quality or impair the device performance.
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