why Si?

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sgyuanyuan

Joined: 02 Dec 2006
Posts: 4

02 Dec 2006 0:42 why Si?

Hello I'm new to here. I'm trying to find out why silicon is used in chips and wondered if anyone could explain this.

And what is the qualification need for jobs in semiconductor?

thanks!

the_risk_master

Joined: 12 Aug 2005
Posts: 688
Helped: 59
Location: UE+MIT, Philippines, (14°N , 120°E )

02 Dec 2006 0:51 Re: why Si?

Silicon is far more abundant than any other source of semiconductor material,
you can actually extract silicon on sand, germanium is the second abundant material and the others are which i dont know.

flatulent

Joined: 19 Jul 2002
Posts: 4877
Helped: 324
Location: Middle Earth

02 Dec 2006 2:46 Re: why Si?

This is because silicon can be made with unusually high purity and it has a lattice constant that will accept group 3 and 5 atoms. Silicon oxide is a good diffusion shield.

Germanium is superior in the mobility area but cannot be made as pure and germanium oxide is not as good a diffusion shield.

bhatt_tanmay

Joined: 18 Sep 2006
Posts: 114
Helped: 9

03 Dec 2006 7:33 Re: why Si?

HI , silicon is semiconductor ,u can see the properties of silicon in the book \"INTEGRATED ELECTRONICS'' by milliman -halkias inin the chapter 1 or 2,and for the job qualification u should have knowledge in microelectronics.u should be at least M.E /MTech in microelectronics/vlsi/ic technology

rkodaira

Joined: 08 Jun 2004
Posts: 332
Helped: 54
Location: Sao Paulo - Brasil

04 Dec 2006 13:31 Re: why Si?

As written before, silicon is a semiconductor element, so its electrical properties classifies semiconductors as not so good electrical conductors and no perfect isolators. This is because they have 4 electrons in their valence layer of electrons. So silicon alone is not useful for electronic devices. When some impurities are inserted in the crystaline structure of the pure silicon crystal, the material changes their electrical properties becoming more conductive and with electrical fields properties. The insertion of some Boron or Phosphorus atoms (the impurities) in the silicon structure, creates the N or P type semiconductors with free holes or electrons in the structure. After this, layers of N and P type semiconductors are arranged to form the semiconductors devices (transistors, diodes, triacs, scrs, mosfets, etc).

neils_arm_strong

Joined: 05 Jan 2006
Posts: 274
Helped: 20

06 Dec 2006 5:43 why Si?

Another reason for use of Si compared to Ge is its high temperature tolerance.

maks10

Joined: 09 Jun 2005
Posts: 49
Helped: 3
Location: Bangalore, India

06 Dec 2006 8:18 Re: why Si?

I have somethin 2 say regardin qualification for getting a job in semiconductor industry.. IN designing side u need 2 have a project experience. U shud be a Btech in E&C + u shud have done a PG diploma in VLSI. Or else masters in vlsi is more prominant.. Well since u have asked abt Silicon I think Ur asking for jobs in Fabrication industry. Well for fab jobs metallurgy & physics shud be the main subjects in your degree. All these stated with my limited knowledge. Correct if I am wrong..

rohitppande

Joined: 23 May 2006
Posts: 9

29 Dec 2006 10:25 Re: why Si?

Si is a semiconductor device which falls between conductors and insulators. It enables to have components which allow unidirectional flow of current and also such components which allow us to have a rapid switching action.
Now the point of using Si over Ge is that Si can work over a larger temperature range than Si. Also the leakage current in Si devices is much less than the Ge devices.

arman_arian2005

Joined: 20 Oct 2006
Posts: 33
Helped: 3

29 Dec 2006 12:21 Re: why Si?

Well... I guess

1. Ease of extraction
2. Temperature tolerance
3. Less leakage Current and
4. Faster Swichig
are the reasons.

rabel126

Joined: 08 Feb 2006
Posts: 101
Helped: 12
Location: pakistan

29 Dec 2006 20:43 Re: why Si?

because of its stability over a range of temperature see the structure of silicon and germemium u can see the difference why we use it and after careful examination read falowing reason

because a little temperature variation cause the device to be unstable so we use silicon and it is cheap too

most stable at temperature is GaAs but it is very expensive

rosarioantony

Joined: 04 Aug 2005
Posts: 71
Helped: 5

30 Dec 2006 8:22 Re: why Si?

not only silicon , any semiconductor element can be used.
silicon is widely used because of availability and fabrication cost .

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/solids/dope.html#c4

DoctorProf

Joined: 26 Mar 2002
Posts: 86
Helped: 4

31 Dec 2006 1:41 Re: why Si?

I want to add my 2 cents worth.

All of what has been said is true but I believe the main reason silicon is used so widely is the fact that it grows a stable high quality oxide. Many of the other semiconductors do not form a stable quality oxide.

DrProf

toram16

Joined: 19 Dec 2006
Posts: 24
Helped: 1
Location: banglore

02 Jan 2007 12:56 Re: why Si?

as our friends said that above all true once again according to me
since conductors having positive temparature coefficient of resistance it should not useful for all conditions.but due to negive negitive temparature coefficient we should prefer semiconductors.
so any semiconductors like ge ,si,gaAs, we can use
but most preferbly si because

high avaialability
high purity of oxides avaliable
less leakage current
high temparature tolarance
less cost
fabrication process is easy

sgyuanyuan

Joined: 02 Dec 2006
Posts: 4

05 Jan 2007 9:31 Re: why Si?

I really appriciate all! Thanks so much!

Actually I'm an oversea student studying in an English-speaking country for electronic diploma. Language is big problem to me, I usually need to take long time to understand content I've learnt. But I'll try my best to overcome it.

Very Happy

zolam

Joined: 03 Oct 2005
Posts: 102
Helped: 9

05 Jan 2007 9:43 Re: why Si?

actually, the world is going to use PLASTIC instead of SILICON, but giant companies invested a lot in their plants (see the last news in the domain)
i understand ur question was a rhetoric one ?

sgyuanyuan

Joined: 02 Dec 2006
Posts: 4

05 Jan 2007 10:12 Re: why Si?

And I gather all answers about Si:

1. abundant semiconductor (sand)
2. high purity
3. lattice constant
4. SiO2 is a good diffusion shield ???
5. high temperature tolerance
6. allow unidirectional flow of current
7. some related components have a rapid switching action ???
8. Less leakage Current
9. low availability and fabrication cost
10. grows a stable high quality oxide
11. Semiconductor has negitive temparature coefficient ???
12. fabrication process is easy

some I'm still not very clear, like why high purity? due to its crystal structure?

And why material could affect the current follow direction? I just know the ohmic contacts could allow current in both directions.

Im sorry I dont know what the switching action & negitive temparature coefficient are?

And I think I also need to know more about its oxide and other related techniques.

Thanks!!!

Added after 9 minutes:

zolam wrote:

actually, the world is going to use PLASTIC instead of SILICON, but giant companies invested a lot in their plants (see the last news in the domain)
i understand ur question was a rhetoric one ?

Maybe my question is a little stupid, but i really wonder to know it well. I hope work in this field in future.

archillios

Joined: 29 Jun 2005
Posts: 97
Helped: 4

06 Jan 2007 15:44 why Si?

silicon based semiconductor is most deeply researched in semiconductor material physics, and most mature in process, for mass production

ashad

Joined: 28 Mar 2006
Posts: 307
Helped: 9
Location: Singapore

07 Jan 2007 13:38 Re: why Si?

hi,

initially Vacuum tubes was used to control the follow ....... then 1947 in bell lab transistor is invented coz in which semiconductor material (Germaninum) was used

why semiconductor used......
Answer is that in only semiconductor has the property to control the follow of current by changing the impurity level that is why we used semiconductor.

there are various semiconductors available why silicon is used......
Answer is that Si has good thermal and electrical property as compared to other semeconductor and our earth crest consist of silicon so it is very easily available

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mannnish

Joined: 06 Aug 2006
Posts: 201
Helped: 3

11 Jan 2007 4:46 Re: why Si?

The three semiconducting elements (Si, Ge, and Sn) from column IVA of the periodic table serve as a kind of boundary between metallic and nonmetallic elements. Silicon (Si) and germanium (Ge), widely used elemental semiconductors, are excellent examples of this class of materials. [Another important semiconductor material is GaAs, a compound of the group IIIA element Ga; and the group V element, As.]

Silicon is a semiconductor, which means that its electrical behavior is between that of a conductor and an insulator at room temperature. With the proper addition of dopant elements, p-n junctions can be formed on silicon. Useful electronic components and integrated circuits can be built from p-n junctions. Silicon is obtained by heating silicon dioxide (SiO2), or silica, with a reducing agent in a furnace. Silicon dioxide is the main component of ordinary sand.

Aside from being used as semiconductor substrate, silicon is also widely used as dielectric in integrated circuits, usually in the form of silicon dioxide. Dielectric layers are used to isolate conductive lines and the individual components in the circuit from each other. Polycrystalline silicon, or polysilicon, is also used for making resistors or conductors in integrated circuits. The top glassivation used to mechanically and electrically protect the die is also usually composed of silicon in the form of silicon nitride. Silicon is also widely used in semiconductor packaging, being the main ingredient of plastic encapsulants for integrated circuits. Silicon is also used in die overcoats.

vackamania

Joined: 02 Oct 2005
Posts: 220
Helped: 49

15 Jan 2007 4:15 why Si?

major factor which decides the material is the thermal stability at higher temperature...

well only other material that can be used is the germanium but it is not thermally stable so they dont use it and moreover at higher frequency it is not stable too....

sgyuanyuan

Joined: 02 Dec 2006
Posts: 4

19 Jan 2007 20:59 why Si?

thanks all!

I learnt a lot from here. From the purpose of wildly using semiconductor to the application of the silicon, the knowledges are all related to the baisc properties of semiconductor. I should make effort on basis of this subject, and put it into practice to digest sufficiently.