Sensitive CMOS - Electronic Circuits Projects Diagrams Free

Elektor · 17th August 2005, 08:26 PM

why CMOS IC are so much sensitive towards ESD???????????

Dr.EM · 17th August 2005, 08:51 PM

As far as I know, they have a very thin layer of metal oxide in them, and a high enough voltage can arc through this layer, creating a hole.

fsahmed · 17th August 2005, 09:26 PM

CMOS technology is based upon enhancement type mosfets, which r common mosfets with no pre existing channel. A mosfet, or metal oxide semiconductor has a layer of metal (which serves as gate) which is insulated from the semiconductor by a thin layer of silicon dioxide, SiO2 (hence the name, Metal Oxide Semiconductor Field Effect Transistor: MOSFET).

It is the oxide layer that is sensitive to ESD, it cracks, shorting the gate metal with the semiconductor, turning the mosfet into something like a BJT. BJTs r made to handle current while mosfets r not, so excessive current flowing through the device causes it to blow up. (This may not be very accurate an account of what happens but this is the principle behind it all).

audioguru · 18th August 2005, 01:10 AM

I have been using many Cmoc IC's for about 30 years and there is a lot of static electricity here in Canada in winter. I don't use grounding straps and have never damaged one.
Their sensitive inputs are protected with clamp diodes that aren't big enough to arrest a lightning bolt or strong static arc but they do their job very well. About the only precaution I use is to discharge my body's static first before touching a Cmos IC. :lol:

Screech · 18th August 2005, 09:39 PM

Quote:

Originally Posted by audioguru

About the only precaution I use is to discharge my body's static first before touching a Cmos IC. :lol:

How do you discharge yourself , Audiguru ?

Styx · 18th August 2005, 09:56 PM

touch/connect to earth

Whenever I am working on my PC I leave it plugged in and turn off the ATX at the rear.
That leaves the earth connected to the case.
IF I built up charge on my in touching the case I discharge myself, IF I then strapp myself in I am tied to earth

For electronics work I have an ESD plug which is just two plastic prong going into LIVE and NEUTRAL but metal going into teh EARTH pin. Then there is a 4mm socket on the front for me to jack into (as well as a mat)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

17th August 2005, 08:26 PM	#1
Elektor	Sensitive CMOS why CMOS IC are so much sensitive towards ESD???????????

17th August 2005, 08:51 PM	#2
Dr.EM	As far as I know, they have a very thin layer of metal oxide in them, and a high enough voltage can arc through this layer, creating a hole. __________________ Angry!? I'm absolutely electrolytic! Music web page: http://www.music-playground.net/artist/drem/

17th August 2005, 09:26 PM	#3
fsahmed	CMOS technology is based upon enhancement type mosfets, which r common mosfets with no pre existing channel. A mosfet, or metal oxide semiconductor has a layer of metal (which serves as gate) which is insulated from the semiconductor by a thin layer of silicon dioxide, SiO2 (hence the name, Metal Oxide Semiconductor Field Effect Transistor: MOSFET). It is the oxide layer that is sensitive to ESD, it cracks, shorting the gate metal with the semiconductor, turning the mosfet into something like a BJT. BJTs r made to handle current while mosfets r not, so excessive current flowing through the device causes it to blow up. (This may not be very accurate an account of what happens but this is the principle behind it all). __________________ F. S. Ahmed

18th August 2005, 01:10 AM	#4
audioguru	I have been using many Cmoc IC's for about 30 years and there is a lot of static electricity here in Canada in winter. I don't use grounding straps and have never damaged one. Their sensitive inputs are protected with clamp diodes that aren't big enough to arrest a lightning bolt or strong static arc but they do their job very well. About the only precaution I use is to discharge my body's static first before touching a Cmos IC. :lol: __________________ Uncle $crooge

18th August 2005, 09:56 PM	#6
Styx	touch/connect to earth Whenever I am working on my PC I leave it plugged in and turn off the ATX at the rear. That leaves the earth connected to the case. IF I built up charge on my in touching the case I discharge myself, IF I then strapp myself in I am tied to earth For electronics work I have an ESD plug which is just two plastic prong going into LIVE and NEUTRAL but metal going into teh EARTH pin. Then there is a 4mm socket on the front for me to jack into (as well as a mat) __________________ Nothing is impossible. Once a problem is realised, the rest is just details