Talk:Photolithography

Contact printing
Contact printing is something that should be discussed a bit further. I am thinking maybe it can get its own article. This form of photolithography has a lot in common with nanoimprint lithography.Guiding light 17:10, 31 January 2006 (UTC)

What is EUV
EUV sources and materials for lithography currently operate at a central peak wavelength of 13.5 nm, although the spectrum should range from 5 to 50 nm (source). Guiding light 04:31, 7 January 2006 (UTC)

I believe that EUV refers to smaller wavelengths than mentioned in the article. It would be helpful if someone knowledgeable on the subject to correct this. --Matt Stoker

It says that EUV may be able to produce feature sizes down to 10nm in production fabrication by 2016. Did that happen?

Sodium
In my experience, sodium is avoided like the plague in a fab, so I doubt that sodium hodroxide would be used for the developing step, but would expect to see potasium hydroxide there. Gentgeen 15:02, 24 Mar 2004 (UTC)


 * That's true, sodium is totally off limits in CMOS foundries. I've updated the article to mention metal-ion-free developers. 64.119.159.126 04:09, 25 Mar 2004 (UTC)


 * It is not just sodium that is an issue, but any heavy metal ions - anything that is a potential source of contamination. In some processes (non-CMOS) it may be desirable to use NaOH (Sodium Hydroxide) but ONLY if this is considered to be a necessary part of the fabrication process. Metal Ion-Free developers (MIF) (tetra-methyl-ammonium hydroxide? - from memory - needs to be checked) are available as an alternative.

Acid creation
Novolak/DNQ resist systems are made up of a backbone resin called Novolac. Novolac has a certain solubility in alkaline fluids (developer). The solubility can be decreased by adding DNQ. Upon exposure the DNQ is transformed into an ICA acid which increases the solubility to levels above that of the resin. I think it is not only the creation of an acid that makes changes the solubility. There is also some reaction/attraction between the DNQ and novolak that reduces dissolution.

The resist technology described here is based on so-called Novolak/DNQ systems. These work fine -and are still used- for wavelengths downto 365 nm. However when industry moved to lower wavelengths to make feature sizes even smaller they changed there resist technology to chemically amplified resist which has a slightly different working principle.

Chemically amplified resists work on very simiarly to photographic film. Exposure causes a change in the sensitizer creating an acid molecule, in turn upon a post exposure bake process, the acid generated cleaves the polymer creating more acid thus "amplifying" the effect of exposure. This was invented by Willson and Ito of IBM Research in the early 80's. They used acid generators originally invented by Crivello from GE, which were used for epoxy curing.

Needs figures
This article sure could use some images. Would a snap of our Nikon i-Line Wafertrak system be suitable? How about an image of a spinner? What image would most interest the kind of person who is liable to consult this article? Alison Chaiken 06:01, 28 January 2006 (UTC)


 * This sounds good, so long as you can get images that can be licensed under WIki's rather-broad terms. Don't forget to try to put them in "commons" rather than just en.wikipedia.org; that way, all the other language variants can use them as well.


 * Atlant 18:04, 28 January 2006 (UTC)


 * I can upload a photo of our small manual contact aligner if anyone's interested. It's definitely not a high volume machine, but it's good for device research and (I think) well illustrates the idea.  Pictures:,  -- uberpenguin


 * Appropriately captioned, the front view of your aligner would make a nice addition to the rather-barren article.


 * Atlant 00:52, 1 September 2006 (UTC)

The use of photoetch components in scale models
If I wanted to write a section on the use of photolithography in the creation of finescale accessories for model kits (typically called photoetching in the hobby), should I start a new page to handle that topic? It would not be a very long section, so I'm concerned with creating a needless content fork. --Agamemnon2 14:33, 2 June 2007 (UTC)

Definition
Lithography means 'to write in stone'. But does photolithography mean 'to write in a wafer'? Or just 'to write in resist'? In the current definition etching is part of lithography. In that case the lift-off process does not use lithography (there is no etching). Also, the resolution of photolithography is determined not by diffraction but (also) by chemical etching processes. 169000 web pages contain "photolithography and etching". I think one should consider removing etching from the definition of photolithography and mentioning / referring to it. Same for stripping. Mhesselb (talk) 19:41, 9 March 2008 (UTC)
 * I agree. I also noticed this discrepancy when I found that patterning redirects to this page. I was surprised I didn't get a disambiguation page, but even beyond that, the concept of patterning is much broader than just photolithography.  Etching is certainly a separate step from litho, although together they might make up one patterning scheme.  But patterning should also include things like contact printing, mentioned above, and other types of "soft lithography".  Maybe even inkjet printing...  There is a lot of work to be done on a lot of the microprocessing articles.  I wish I had more time, but I'm going to take a look at this when I get a chance. Lone Skeptic (talk) 19:02, 5 August 2008 (UTC)

Basic procedure section is missing some bits
The "Basic procedure -> preparation and photoresist application" sections have had content deleted. An old version of this page, as edited by 201.250.36.43 at 22:23, 18 April 2008, contains the sentences that were deleted.

Photoresist Develop
The "analogy with photographic developer" is better illustrated by preferential etching of a film (layer) since the developer completely removes an area of the photoresist rather than simply changes the opacity of the material as it does in a photographic emulsion. —Preceding unsigned comment added by 74.10.115.69 (talk) 00:01, 27 August 2008 (UTC)

question
Is nano-scale sculpture carving considered a form of photolithograhpy? --Ramu50 (talk) 21:13, 16 September 2008 (UTC)
 * Any reference that shows what you mean by "nano-scale sculpture carving"? --DrTorstenHenning (talk) 10:35, 17 September 2008 (UTC)

--Ramu50 (talk) 19:25, 17 September 2008 (UTC)
 * The Thinker, scultpure made by a Korean Researcher (20millionth of 1m)
 * Micro-bull, made by Japanese engineers (7 micrometer)


 * You win! The reference of the Nature paper describing this work would be interesting. Plantsurfer (talk) 19:47, 17 September 2008 (UTC)


 * There is already a Wikipedia article on stereolithography, which appears to be the method by which the two samples were made. I would not call it carving since that implies the use of a sharp tool to remove material around the final product. --DrTorstenHenning (talk) 21:50, 17 September 2008 (UTC)


 * The bull, at least, is not what is described in the article on stereolithography, as it is produced with a subtractive, not additive process. —Preceding unsigned comment added by 204.227.241.18 (talk) 15:33, 12 October 2009 (UTC)

Patterning in Photoresist
This article glosses over a key step in the lithographic process - creating the pattern that is then projected onto the photoresist in UV prior to etching. If anyone could add this information, it would add greatly to this article. Quodfui (talk) 13:40, 16 November 2013 (UTC)

Resolution in projection systems
The intro to this section contradicts its source. The line "Current state-of-the-art photolithography tools use deep ultraviolet (DUV) light from excimer lasers with wavelengths of 248 and 193 nm" probably comes from the line in the source "Nowadays a state-of-the-art 193 nm light source, such as the Cymer XLR 600ix..." however this appears to be referencing the state of the art of 193 nm lasers, not state of the art lithography, as the article later states "During that time period, the source wavelength progressed from 436 nm down to 193 nm and now to 13.5 nm"

It’s unclear where the reference to 50nm feature size comes from as it is not mentioned in the source. The source also suggests that lithography would be used "to support high-volume manufacturing starting in the 2012-2013 timeframe." Implying a much smaller minimum feature size than 50nm.

The line "over the past 20 years" is also unclear, past 20 years from when? User:31.185.58.188 08:45, 20 July 2020 (UTC)