Is Silicon Transparent to Infrared Light?

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Discussion Overview

The discussion centers around the transparency of silicon to infrared (IR) light, exploring whether silicon allows IR waves to pass through without change, and if this transparency is influenced by factors such as temperature. Participants seek references and data regarding silicon's optical properties in the infrared spectrum.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if silicon is 100% transparent to infrared light and whether this transparency is affected by temperature or other parameters.
  • Another participant compares silicon's transparency to that of glass for optical wavelengths, noting that while it appears transparent, there is some absorption, refraction, and reflection involved.
  • A participant provides links to resources that detail the transmission characteristics of silicon and compares it to other materials like ZnSe.
  • There is a mention of a specific application where silicon is used with backside IR illumination for mask alignment, although the participant has not personally used this setup.
  • One participant expresses confusion regarding the transmission percentages discussed, noting a discrepancy between a claim of high 90s transmission and their own findings of just below 60% maximum transmission.

Areas of Agreement / Disagreement

Participants express differing views on the extent of silicon's transparency to infrared light, with some suggesting high transmission rates while others report lower values. The discussion remains unresolved regarding the exact transparency characteristics of silicon in the infrared spectrum.

Contextual Notes

There are limitations in the discussion regarding the definitions of transparency and the specific conditions under which measurements are taken, as well as the potential influence of temperature and other factors on transmission rates.

rr00053
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hi everyone...

i have got a general doubt...I have heard that silicon is transparent to
infrared...so does that mean that any IR wave entering silicon comes out of it without any change? Is silicon 100% transparent to IR? does the transparency depend on temperature or any other parametre?

Can anyone give me some reference material, suggest some books or some links where i can get data about silicon transparency?

please hep me...
thanks in advance...
 
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Well, it's about the same as, for instance, glass for optical wavelengths. It looks more or less transparent, and the transmission is in the high 90s, but there is some (small) absorption and some refraction and a small bit of reflection. There's a mask aligner in the place I work at that uses backside IR illumination so you can align masks to features already present on the silicon. Haven't used it myself, however.

Here's a paper from Virginia Semiconductor (they make custom silicon)--this is targeted mostly to researchers, and it may be difficult to understand without some optics background:
http://www.virginiasemi.com/pdf/Optical%20Properties%20of%20Silicon71502.pdf
 
Last edited by a moderator:
Hi matlabdude,
thanku very much for the response and the reference u gave...taking a quick look at the data u gave and the data andy resnick gave...the maximum transmission seems jus below 60%. however u pointed out tat transmission is at high 90's ...
anyway thanyou for the data you gave...
 
HI andy resnick,
thanku for the valuable links...
 
rr00053 said:
Hi matlabdude,
thanku very much for the response and the reference u gave...taking a quick look at the data u gave and the data andy resnick gave...the maximum transmission seems jus below 60%. however u pointed out tat transmission is at high 90's ...
anyway thanyou for the data you gave...

High 90s is visible light through a thin piece of glass (I was laying down the groundwork in case you didn't have any background)
 

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