A schematic illustration of a photomask (top) and an integrated circuit created using that mask (bottom).

A photomask is an opaque plate with holes or transparencies that allow light to shine through in a defined pattern. They are commonly used in photolithography. Lithographic photomasks are typically transparent fused silica blanks covered with a pattern defined with a chrome metal absorbing film. Photomasks are used at wavelengths of 365 nm, 248 nm, and 193 nm. Photomasks have also been developed for other forms of radiation such as 157 nm, 13.5 nm (EUV), X-ray and electrons and ions, but these require entirely new materials for the substrate and the pattern film. A drawing of different reticles used in telescopic sights. ... Image File history File links Mask_illustration. ... Image File history File links Mask_illustration. ... Photolithography is a process used in semiconductor device fabrication to transfer a pattern from a photomask (also called reticle) to the surface of a substrate. ... Fused quartz is a man-made material manufactured principally from sands. ... A nanometre (American spelling: nanometer) is 1. ... Extreme Ultraviolet Lithography (also known as EUV or EUVL) is a next-generation lithography technology using the 13. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... ...

A set of photomasks, each defining a pattern layer in integrated circuit fabrication, is fed into a photolithography stepper or scanner and individually selected for exposure. In double patterning techniques, a photomask would correspond to a subset of the layer pattern. Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... A stepper is a device used in the manufacture of integrated circuits (ICs) that is similar in operation to a slide projector or a photographic enlarger. ... A stepper is a device used in the manufacture of integrated circuits (ICs) that is similar in operation to a slide projector or a photographic enlarger. ... Multiple patterning is an extension of double patterning, a class of technologies developed for photolithography to enhance the feature density. ...

In photolithography for the mass production of integrated circuit devices, the more correct term is usually photoreticle or simply reticle. In the case of a photomask, there is a one-to-one correspondence between the mask pattern and the wafer pattern. This was the standard for the 1:1 mask aligners that were succeeded by steppers and scanners with reduction optics. As used in steppers and scanners, the reticle commonly contains only one layer of the chip. (However, some photolithography fabs utilize reticles with more than one layer patterned onto the same mask). The pattern is projected and shrunk by four or five times onto the wafer surface. To achieve complete wafer coverage, the wafer is repeatedly 'stepped' from position to position under the optical column until full exposure is achieved. Mass production is the production of large amounts of standardised products on production lines. ... Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ...

Features 150 nm or below in size generally require phase-shifting to enhance the image quality to acceptable values. This can be achieved in many ways, but the two most common methods are to use an attenuated phase-shifting background film on the mask to increase the contrast of small intensity peaks, or to etch the exposed quartz so that the edge between the etched and unetched areas can be used to image nearly zero intensity. In the second case, unwanted edges would need to be trimmed out with another exposure. The former method is attenuated phase-shifting, and is often considered a weak enhancement, requiring special illumination for the most enhancement, while the latter method is known as alternating-aperture phase-shifting, and is the most popular strong enhancement technique.

As leading-edge semiconductor features shrink, photomask features which are 4× larger must inevitably shrink as well. This could pose challenges as the absorber film will need to become thinner, and hence less opaque. ^[1] A recent study by IMEC has found that thinner absorbers degrade image contrast and hence contribute to line-edge roughness, using state-of-the-art photolithography tools. ^[2] One possibility is to eliminate absorbers altogether and use 'chromeless' masks, relying solely on phase-shifting for imaging. IMEC (Interuniversity Microelectronics Centre) is a microelectronics research facility on the outskirts of Leuven, Belgium with affiliated laboratories throughout Flanders. ...

The emergence of immersion lithography has a strong impact on photomask requirements. The commonly used attenuated phase-shifting mask is more sensitive to the higher incidence angles applied in "hyper-NA" lithography, due to the longer optical path through the patterned film. ^[3] Immersion lithography is a photolithography resolution enhancement technique that replaces the usual air gap between the final lens and the wafer surface with a liquid medium that has a refractive index greater than one. ...

Leading commercial photomask manufacturers, 2003

• Dai Nippon Printing Company, Japan, $499 mln (revenue)
• Photronics, USA, $349 mln
• Toppan Photomasks, USA, $326 mln
• Toppan Printing Company, Japan, $321 mln

In October, 2004, DuPont Photomasks was acquired by Toppan, approved by U.S. regulators and merged in May 2005 to became the largest photomask manufacturer. Dai Nippon Printing ), established in 1876, is a Japanese printing company. ...

Major chipmakers such as Intel, AMD, IBM, NEC, TSMC, Samsung, Micron Technology, etc., have their own large maskmaking facilities. Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... Advanced Micro Devices, Inc. ... For other uses, see IBM (disambiguation) and Big Blue. ... NEC Corporation (Jp. ... Taiwan Semiconductor Manufacturing Company, Limited (Traditional Chinese: 台灣積體電路製造股份有限公司, abbrev. ... Samsung Group is one of the largest South Korean business groupings. ... Micron Technology (Micron) NYSE: MU is a multinational company based in Boise, Idaho, USA, best known for producing many forms of semiconductor devices. ...

• Photo Sciences, Inc. is the largest privately held photomask manufacturer in the United States, 2007.

The cost to set up a modern 45 nm process mask shop is US$200-500 million, a very high threshold for entering this market. The purchase price of a photomask can range from $1,000 to $40,000 for a single, high end phase shift mask; as many as 30 masks (of varying price) may be required to form a complete mask set. A Maskshop is a factory which exclusively manufactures photomasks for use in the Semiconductor industry within a cleanroom. ... The United States dollar is the official currency of the United States. ...

References

1. ^ Y. Sato et al., Proc. SPIE, vol. 4889, pp. 50-58 (2002).
2. ^ M. Yoshizawa et al., Proc. SPIE, vol. 5853, pp. 243-251 (2005)
3. ^ C. A. Mack et al., Proc. SPIE, vol. 5992, pp. 306-316 (2005)

External links

• Photomask production process
• UCLA Mask Shop
• Design rule guide for CAD layout of photomasks
• Masking out difficult images in Photoshop