Talk:Semiconductor fabrication

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The oxidation link leads to Redox which is not appropriate for semiconductor device fabrication because it ignores the growth of an SiO2 film on top of a silicon substrate. Propose breaking out "Oxidation" from Redox in order to address this issue and talk more specifically about silicon reactions with oxygen and why such reactions are performed. Alternatively, if someone has objections to this use of "Oxidation", a topic such as "Oxide Growth" or "Oxide Formation" (which could also include oxide deposition) could be used. Amadeust 21:27, 12 Nov 2004 (UTC)


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[edit] Wafer cost questioned

I have issues with this part: "In 2005, a typical cost for a processed 300mm wafer was about $US 300,000. The desire for profit inspires manufacturers to pack more devices on a wafer."

The total surface area of a round 300mm-diameter wafer is about 71,000 mm2 (square millimeters, don't know how to superscript.) Using my Sempron CPU as an example, it uses about 100mm2. So ignoring waste about 700 Semprons-to-be fit on a wafer. That's over $400 each, and we're a long, long way from a finished product. I'd expect my $70 Sempron to cost at least $2000 if the $300,000 wafer cost is correct.

Also, they cut 1000-2000 wafers off an ingot these days, implying PER INGOT production cost of $300,000,000 to $600,000,000 if $300,000 is correct for a single wafer.

Does anyone have a better number for wafer cost? Shyland 23:58, 15 April 2006 (UTC)

Update: I'm editing the section about wafer cost based on data from icknowledge.com. Estimated cost for a 300mm wafer for 130nm IC's is currently around $2500-$3500. Shyland 02:34, 16 April 2006 (UTC)

I seem to remember from a couple of year's ago Discovery program that a wafer costs around $8000 (at that time obviously). There's no way it can cost $300,000 these days. A few thousand dollars is a good estimate, although I'm sure the exact price varies a lot with process size, number of masks, etc, etc. Romanski 21:53, 15 May 2006 (UTC)

[edit] "A number is" vs. "a number are"

I disagree with the last edit to change "a number are" to "a number is". Grammar authorities generally call for collective nouns indicative of a plurality of something to take the plural verb. Accordingly, "a number are" is correct and it certainly pleases my ear more. Still, I don't want to be the one to just edit it back to the previous version.

Perhaps you have the wrong article? I can't find that phrase in this article. Aaronmz 01:52, May 12, 2005 (UTC)

[edit] The recent content deletions

I'm always troubled when an anonymous editor comes along and deletes a bunch of apparently-valid content from an article (as just happened here). Ordinarily, I'd revert the change but in this case, some value was added as well. Does anyone have any opinions on the accuracy or importance of the deleted 'graphs:

  • It is important for these workers to minimize their exposure to the toxic materials used in manufacture, such as arsenic; for this reason, the semiconductor fabrication facilities are highly automated.
  • Memory chips are typically the first devices to use a technology, as they are highly regular, and can be used to test a technology.
  • In an effort to increase profits, semiconductor device manufacture spread from Texas and California in the 1960s to the rest of the world, such as Malaysia and Japan, and is a global business today. Some Malaysian facilities are now in their fourth decade of operation, for example.

(Some of that last 'graph now exists in the recent edit.)

Opinions?

Atlant 16:41, 24 May 2005 (UTC)

I reinstated the Hazard notice. The information about RAM is in the IC article. The history of semiconductor manufacture in Malaysia etc might be reinstated. But it may well be the case that these fabs are long gone. Ancheta Wis 11:54, 30 May 2005 (UTC)

My comments on the deleted sections - I would say they needed revising at least.

The reason for increased automation in semiconductor fabrication facilities (fabs) is not a safety measure, though safety may improve as a consequence. Automation reduces the chance of "mis-processing" material which can result in "scrap". Human operators make mistakes while a programmed automated process, when correctly set up, does not.

With regard to RAM leading the way I would say that memory and microprocessor technology are increasingly taking different paths. Memory devices perhaps rely more on novel memory cell designs, on ways to reduce process steps and dealing with extreme physical features such as trench depth. Microprocessors, in the hunt for process speed, lead the way in minimum device sizes, new engineered substrates (such Silicon on Insulator and Strained Germanium Silicon) and new interconnect techniques an material (copper, dual damascene, etc).

As for the spread of manufacturing, the desire to build IC's in the US is fading fast and Taiwan, now the king, will probably hand its crown to China in the coming decades, at least with respect to numbers. Malaysia has been more involved in relatively low-tech post-fab dicing, bonding and packaging operations and is not an IC fab stronghold. Interestingly the most advanced, mass-produced microprocessors are still produced in the "West", especialy in the USA and Europe.

Supplied by Rutherford - 13 June 2005

I've rewitten the hazards section - before reading this discussion (blush). But I think what I've written takes account of what was being said above. I can confirm that we used to use all that hazardous stuff before there was significant automation - the automation was put in to improve reproduceabilty mainly. --Phil Holmes 14:09, 6 September 2005 (UTC)
Phil,
We use to seperate acids and solvents too.
Acids went into a tank and solvents went down the drain.
May want to label in the article the same?

Cheers

Scott 15:25:22, 2005-09-06 (UTC)

As measured by sales, the largest semiconductor manufacturers in the world are Intel, Samsung, and Texas Instruments. (Data from IC Insights.) It's hard to compare TSMC and other foundries, since foundries don't sell directly to end users, but the claim that Singapore is the second biggest manufacturer in the world is, um, questionable at best. Edited the section to reflect this.--Katherine (Was registered user, but lost ID info.) 66.30.210.131 21:47, 9 February 2006 (UTC)

[edit] Correct the source links

There's an extensive list of articles that link to Fabrication (semiconductor). Now that that is a redirect page, we should edit all the source links to correctly link to the real article here at Semiconductor fabrication.

Atlant 17:17, 5 August 2005 (UTC)

[edit] Front end/Back end?

The article refers to front end processes (photolith and doping, etc.) and back end processes (metal, etc.). It's been a while since I worked in the industry (mid 80's) but we never referred to these processes as front or back end. Has anyone else ever heard of them? --Phil Holmes 14:12, 6 September 2005 (UTC)

Front end and Back end refer to the use of Copper (Cu) in the processs. FE is usually to about the 1st metal layer and all of that is done without Cu because of its migratory properties and hazards to the chemistries in the early stages of the process. Once the interconnecting layers are started (they are Cu now) then the process becomes BE. These terms are mainly for segregation of tools so that there is no Cu/Non-Cu cross contamination.

[edit] Device Test & Tungsten

In my opinion, in this section should be a link to the DFT page and some description about that: http://en.wikipedia.org/wiki/Design_For_Test Opinions?

And a Question about the vias: I recently learnt that the lower metal layers (1&2) are connected with tungsten vias (called tungsten-plugs) to the silicon and amongst each other. In the higher metal layers, the vias are the same material as the metal. Why is tungsten used for metal 1&2?

Andreas

At least one reason tungsten is used is because when the metal layers are copper, the copper would contaminate the semiconductor. The tungsten acts as a barrier to copper contamination. For aluminum metalization, I don't know; someone else will have to answer; my next guess would be for better compatibility between the coeffients of thermal expansion.
Atlant 20:23, 9 February 2006 (UTC)

Tungsten also offers better electromigration resistance (though worse electrical resistance) than aluminum, so tungsten vias can block electromigration. -- Katherine 66.30.210.131 21:59, 9 February 2006 (UTC)


I have seen some images (transistor crossection) and additionally to your thoughts I think to have two additional ones: 1. It seems you can (due to some reasons I don't know) achieve way better aspect ratios with tungsten. All the aluminum interconnects on higher levels had considerably worse aspect ratios and showed intense underetching (.18 CMOS). 2. Maybe there are some high temperature processes to do while the first via layer is already applied. Eutectic Si-Al melts at 577°C which is not very much for some diffusion processes and stuff.

The thermal expansion seems to be a good point as well. Thermal expansion coefficients: Si: 2.6 µm/(m·K) W: 4.5 µm/(m·K) Al: 23.1 µm/(m·K)

Andreas


May I ask to what does the sentence "This takes six to eight weeks" in the "Device test" section refer to? Laser etching, chip mounting, or the entire testing process? If it confused me, you can be sure it will confuse a few more people. A little bit of disambiguation by someone more knowledgeable would be welcome, i.e. make it clearer. -- xompanthy 18:45, 11 March 2006 (UTC)

Perhaps the entire beginning-to-end IC production process? I'm mystified too. Shyland 02:58, 16 April 2006 (UTC)

[edit] Title of article

I think this article should be entitled "Semiconductor device fabrication". It mostly seems to address IC product fabrication and doesn't really discuss any of the material system development issues that the current article title might imply. In addition, semiconductors themselves aren't "fabricated" strictly speaking, but refined grown into crystals, and processed for electronic/electromechanical device construction. If there are no objections, I'll move the article soon. -- mattb @ 2007-01-13T16:07Z

Also consider "microelectronic fabrication". --Smack (talk) 18:34, 18 January 2007 (UTC)
No, as this would exclude MEMS, which are still mostly a semiconductor field (with exceptions). It is also not a very suitable title for devices like LED, lasers, APDs, etc, which are generally called "optoelectronics." I think "semiconductor device fabrication" is an appropriate title. -- mattb @ 2007-01-18T19:57Z

[edit] Merge

This article overlaps greatly with Microfabrication. I admit that the two terms are not exactly synonymous, and each includes some areas that the other does not. However, I think that we should restructure our coverage of micro/electronic fabrication to eliminate this overlap and clearly identify non-overlapping areas. --Smack (talk) 18:34, 18 January 2007 (UTC)

Strong oppose. Semiconductor fabrication is a big enough topic without merging in all the non-semiconductor microfabrication stuff. If there's too much overlap, take some of the semiconductor part out of microfabrication. Dicklyon 18:48, 18 January 2007 (UTC)
Oppose per Dick. While microfabrication has largely been a semiconductor-dominated field in the past, the development of biomedical MEMS and the like have provided the motivation for developing microfabrication techniques for totally unrelated materials like polymers. These articles should remain separate and have little overlap, even if the articles' current status don't reflect this ideal. -- mattb @ 2007-01-18T19:55Z
Close for lack of support; leave separate articles. Dicklyon 18:22, 21 January 2007 (UTC)
But we still have overlap. Would someone like to remove it? --Smack (talk) 19:11, 21 January 2007 (UTC)
Add a comment to the microfabrication talk page to suggest what work it needs; some overlap is OK, but that article shouldn't need to get into the details that this one covers well. Dicklyon 19:16, 21 January 2007 (UTC)
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