Micralign
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Perkin-Elmer PerkinElmer, Inc., previously styled Perkin-Elmer, is an American global corporation that was founded in 1937 and originally focused on precision optics. Over the years it went into and out of several different businesses via acquisitions and di ...
Micralign was a family of aligners introduced in 1973. Micralign was the first projection aligner, a concept that dramatically improved
semiconductor fabrication Semiconductor device fabrication is the process used to manufacture semiconductor devices, typically integrated circuits (ICs) such as microprocessors, microcontrollers, and memories (such as RAM and flash memory). It is a multiple-step photol ...
. According to the Chip History Center, it "literally made the modern IC industry". The Micralign addressed a significant problem in the early
integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
(IC) industry, that the vast majority of ICs printed contained defects that rendered them useless. On average, about 1 in 10 complex ICs produced would be operational, a 10% yield. The Micralign improved this to over 50%, and as great as 70% in many applications. In doing so, the price of
microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...
s and dynamic RAM products fell about 10 times between 1974 and 1978, by which time the Micralign had become practically universal in the high-end market. Initially predicting to sell perhaps 50 units, Perkin-Elmer eventually sold about 2,000, making them the by far largest vendor in the semiconductor fabrication equipment space through the second half of the 1970s and early 1980s. Formed into the Microlithography Division, by 1980 its income was the largest of Perkin-Elmer's divisions and provided the majority of the company's profits. The company was slow to respond to the challenge of the stepper, which replaced the projection aligners in most roles starting in the mid-1980s. Their move to
extreme ultraviolet Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths shorter than the hydrogen Lyman-alpha line from 121  nm down to ...
as a response failed, as the technology was not mature. Another attempt, buying a European stepper company, did nothing to reverse their fortunes. In 1990, Perkin-Elmer sold the division to Silicon Valley Group, which is today part of
ASML Holding ASML Holding N.V. (commonly shortened to ASML, originally standing for Advanced Semiconductor Materials Lithography) is a Netherlands, Dutch multinational corporation that specializes in the development and manufacturing of photolithography mach ...
.


Background

Integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
s (ICs) are produced in a multi-step process known as
photolithography Photolithography (also known as optical lithography) is a process used in the manufacturing of integrated circuits. It involves using light to transfer a pattern onto a substrate, typically a silicon wafer. The process begins with a photosensiti ...
. The process begins with thin disks of highly pure
silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
being sawn from a crystalline cylinder known as a boule. After initial processing, these disks are known as wafers. The IC consists of one or more layers of lines and areas patterned onto the surface of the wafer. The wafers are coated in a chemical known as
photoresist A photoresist (also known simply as a resist) is a light-sensitive material used in several processes, such as photolithography and photoengraving, to form a patterned coating on a surface. This process is crucial in the electronics industry. T ...
. One layer of the ultimate chip design is printed on a "mask", similar to a
stencil Stencilling produces an image or pattern on a surface by applying pigment to a surface through an intermediate object, with designed holes in the intermediate object. The holes allow the pigment to reach only some parts of the surface creatin ...
. The mask is placed over the wafer and an
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
(UV) lamp, typically a mercury arc lamp, is shone on the mask. Depending on the process, areas of the photoresist that are exposed to the light either harden or soften, and then the softer areas are washed away using a
solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...
. The result is a duplication of the pattern from the mask onto the surface of the wafer. Chemical processing is then used on the pattern to give it the desired electrical qualities. This entire process is repeated several times to build up the complete IC design. Each step uses a different design on a different mask. The features are measured in micrometres, so any previous design already deposited has to be precisely aligned with the new mask that will be applied. This is the purpose of the aligner, a task that was originally completed manually using a
microscope A microscope () is a laboratory equipment, laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic ...
. There is a strong economic argument to use larger wafers, as more individual IC's can be patterned on the surface and produced in a single series of operations, thereby producing more chips during the same period of time. However, larger wafers give rise to significant optical issues; focussing the light over the area while maintaining very high uniformity was a major challenge. By the early 1970s, wafers had been about 2.5 inches in diameter for some time and were just moving to 3 inches, but existing optical systems were having problems with this size. Every time a new wafer size was introduced, the optical systems had to be redesigned from scratch.


Contact aligners

In the 1960s, the most common way to hold the mask during the exposure processes was to use a contact aligner. As the name implies, the purpose of this device was to precisely align the mask between each patterning step, and once aligned, hold the mask directly on the surface of the wafer. The reason for holding the mask on the wafer was that at the scale of the lines being drawn,
diffraction Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the Wave propagation ...
of the light around the edges of the lines on the mask would blur the image if there was any distance between the mask and the wafer. There were significant problems with the contact-mask concept. One of the most annoying was that any dust that reached the aligner's interior might stick to the mask and would be imaged on subsequent wafers as if it were part of the pattern. Equally annoying was that uncured photoresist would stick to the mask, and when the mask was lifted, it would pull off the top surface from the wafer, destroying that wafer and once again adding spurious images on the mask. Any one error might not be an issue because only the ICs in that location will be affected, but eventually, enough errors will be picked up that the mask is no longer useful. As a result of issues like these, masks generally lasted only a dozen times before having to be replaced. To supply the required number of masks, copies of the original mask were repeatedly printed using conventional
silver halide A silver halide (or silver salt) is one of the chemical compounds that can form between the Chemical element, element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine wit ...
photography on photographic stock, which was then used in the machine. The thermal stability of these masks during exposure to bright light caused distortions, which were not a concern in the early days but became an issue as feature sizes continued to shrink. This forced a move from film to glass masks, further increasing costs. Because any particular wafer could be damaged at any given masking step, the chance that any one wafer would make it through to production without damage was a function of the number of steps. This limited the complexity of the IC designs in spite of the designers being able to make use of many more layers.
Microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...
s, in particular, were complex multi-layer designs that had extremely low yield, with perhaps 1 in 10 of the patterns on a wafer delivering a working chip.


Microprojector

The Micralign traces its history to a 1967 contract with the
US Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
for a higher-resolution aligner. At the time, the Air Force was one of the largest users of ICs, which were used in many of their missile systems, notably the Minuteman missile. The cost, and especially time to market, was a significant problem that the Air Force was interested in improving. There was a second type of aligner in use, the proximity aligner. As the name implies, these held the mask in close proximity to the wafer rather than in direct contact. This improved the life of the mask and allowed a more complex design, but had the downside that diffraction effects limited its use to relatively large features compared to the contact aligners. More annoying was the fact that the mask had to be aligned in three axes to make it perfectly flat relative to the wafer, which was a very slow process, and had to hold the mask in such a way that it didn't sag. The Air Force had worked with Perkin-Elmer for many years on reconnaissance optics, and the
Air Force Materiel Command The Air Force Materiel Command (AFMC) is a Major Command (MAJCOM) of the United States Air Force (USAF). AFMC was created on July 1, 1992, through the amalgamation of the former Air Force Logistics Command (AFLC) and the former Air Force System ...
at
Wright-Patterson Air Force Base Wright-Patterson Air Force Base (WPAFB) is a United States Air Force base and census-designated place just east of Dayton, Ohio, in Greene County, Ohio, Greene and Montgomery County, Ohio, Montgomery counties. It includes both Wright and Patte ...
offered them a contract to see whether they could improve the proximity masking system. The result was the Microprojector. The key to the design was a 16-element lens system that produced an extremely focused light source. The resulting system could produce 2.5  μm features, 100 millionths of an inch, equal to the best contact aligners. Although the system was effective, meeting the goals set by the Air Force, it was not practical. With a large number of lenses, dispersion was a significant problem, which they addressed by filtering out everything but a single band of UV only 200-
angstrom The angstrom (; ) is a unit of length equal to m; that is, one ten-billionth of a metre, a hundred-millionth of a centimetre, 0.1 nanometre, or 100 picometres. The unit is named after the Swedish physicist Anders Jonas Ångström (1814–18 ...
wide (the G-line), throwing away the majority of the light coming from the 1,000 W lamp. This made the exposure times even longer than existing proximity designs. Another significant problem was that the filters removed the visible light as well as UV, which made it impossible for the operators to view the chips during the alignment process. To solve this problem, they added an
image intensifier An image intensifier or image intensifier tube is a vacuum tube device for increasing the intensity of available light in an optical system to allow use under low-light conditions, such as at night, to facilitate visual imaging of low-light proce ...
system that produced a visible image from the UV that could be used during alignment, but this added to the unit's cost.


New concept

Harold Hemstreet, manager of what was then the Electro-Optical Division, felt that Perkin-Elmer could improve on the Microprojector. He called on Abe Offner, the company's main optical designer, to come up with a solution. Offner decided to explore systems that would focus the light using mirrors instead of lenses, thus avoiding the problem of dispersion. Mirrors suffer from another problem, aberration, which makes it difficult to focus near the edges of the mirror. Combined with the desire to move to the larger 3-inch wafers, a mirror would be a difficult solution in spite of its advantages. Offner's solution was to use only a small portion of the mirror system to image the mask, a section where the focus was guaranteed to be correct. This was along a thin ring running about halfway out from the center of the primary mirror. That meant only this sliver of the mask's image was properly focussed. This could be used if the resulting light was magnified to the size of the mask, but Rod Scott suggested that it instead be used by scanning the sliver of light across the mask. Scanning requires the light to shine on the photoresist for the same time as it would for the entire wafer in a contact aligner, so this implied that a scanner would be much slower to operate, as it imaged only a small portion at a time. However, because the mirror was achromatic, the entire output of the lamp could be used, rather than just a small window of frequencies. In the end, the two effects offset each other, and the new system's imaging time was as good as contact systems. John Bossung built a proof-of-concept system that copied a mask onto a photographic slide. This won another $100,000 contract from the Air Force to produce a working example.


Practical design

The $100,000 would not be enough to bring such a system to commercial production, so Hemstreet had to persuade management to fund development. At the time, another division was asking for funds to develop a laser letterpress, a high-speed currency printing system, and Hemstreet had to argue they should be funded instead of that project. When the
board of directors A board of directors is a governing body that supervises the activities of a business, a nonprofit organization, or a government agency. The powers, duties, and responsibilities of a board of directors are determined by government regulatio ...
asked about the potential market, he suggested that the company might sell 50 of the systems, which was laughed at as no one could imagine a requirement for 50 such machines. Nevertheless, Hemstreet managed to win approval for the project. In May 1971 a production team was formed, led by Jere Buckley, a mechanical designer, and Dave Markle, an optical engineer. Offner's original design required the mask and wafer to be scanned horizontally in precisely the same motion as the mask passed over the active area of the mirror system. This appeared to be fantastically difficult to arrange with the required precision. They developed a new layout where both the mask and wafer were held on opposite ends of a C-shaped holder, at right angles to the main mirror. New mirrors reflected the light through right angles so vertical motion of the holder was translated into horizontal scanning over the main mirror, and a roof prism flipped the final image so that the mask and wafer did not produce mirror images. By making the C-shaped holder large enough, rotating the assembly produced a facsimile of horizontal scanning that was more than accurate enough for the desired resolution. A flexure bearing was used to provide super-smooth rotational motion. Perkin-Elmer boasted that one could throw a handful of sand into the mechanism and it would still work perfectly. There is no record of the scanner ever failing. The basic mechanical design was completed by November 1971. The next step was to come up with a lamp that could efficiently light the curved section of the mirror. They called Ray Paquette at Advanced Radiation Corporation, and after working on it for about two hours he had produced a sample of a curved lamp. Offner then designed a new
collimator A collimator is a device which narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays), or to cause the spat ...
that worked with the curved shape. Because almost all of the light from the lamp was being used, scanning took 10 to 12 seconds, a dramatic improvement over older systems. The next problem was how to align the mask, as the system focussed only UV light. This was solved by adding a dielectric coating that reflected the UV but not visible light. A separate lamp was used during the alignment process, with the light passing through the optics to the microscope that the operator used to align the mask. The product was set to launch in the summer of 1973. In a pre-launch sales effort, the company ran a series of wafers for
Texas Instruments Texas Instruments Incorporated (TI) is an American multinational semiconductor company headquartered in Dallas, Texas. It is one of the top 10 semiconductor companies worldwide based on sales volume. The company's focus is on developing analog ...
, which they then used as their "golden wafers" to show to potential clients. They showed the wafers to
Raytheon Raytheon is a business unit of RTX Corporation and is a major U.S. defense contractor and industrial corporation with manufacturing concentrations in weapons and military and commercial electronics. Founded in 1922, it merged in 2020 with Unite ...
who rejected them,
National Semiconductor National Semiconductor Corporation was an United States of America, American Semiconductor manufacturing, semiconductor manufacturer, which specialized in analogue electronics, analog devices and subsystems, formerly headquartered in Santa Clara, ...
who were impressed, and
Fairchild Semiconductor Fairchild Semiconductor International, Inc. was an American semiconductor company based in San Jose, California. It was founded in 1957 as a division of Fairchild Camera and Instrument by the " traitorous eight" who defected from Shockley Semi ...
who produced
electron microscope An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing it ...
images of the wafers which showed they had "horrible edges". By the time they returned to company headquarters in Norcross, Raytheon had indicated that the problem might not be with the aligner itself, but the photoresist layers. They sent one of their experienced operators to Perkin-Elmer and began sorting out the practical problems of fabrication that the company had not had to deal with previously.


Micralign 100

The first sale of what was now known as the Micralign 100 was in 1974 to Texas Instruments, which paid $98,000 for the machine, , about three times that of existing high-end contact aligners. Sales to
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...
and
Raytheon Raytheon is a business unit of RTX Corporation and is a major U.S. defense contractor and industrial corporation with manufacturing concentrations in weapons and military and commercial electronics. Founded in 1922, it merged in 2020 with Unite ...
followed. Intel kept their system secret, and were able to introduce new products, notably memory devices, at prices no one else could touch. The secret finally leaked out when various Intel workers left the company. The sales pitch to early customers was simple; they could use their existing glass master masks, or "reticles", without the need to print working masks at all. The masks would last 100,000 uses instead of 10. By the next year, the company was in full-out production and had a year-long backlog of orders. By 1976, they were selling 30 a month. The only issue found during initial use was that the longer exposures led to new issues with thermal expansion, which was cured by moving from conventional soda-lime glass to
borosilicate glass Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...
for the masks. The real advantage was not a reduction in mask costs, but improved yield. A 1975 report by a 3rd party research firm outlined the impressive advantages; because the contact problems with dirt and sticking emulsion were eliminated, yields had improved dramatically. For simple single-layer ICs like the 7400-series, yields improved from 75 percent with contact printing to 90 percent with the Micralign. Results were more dramatic for larger chips; a typical four-function calculator chip yielded 30 percent using contact printing, Micralign yielded 65 percent. Microprocessors were only truly useful after the introduction of the Micralign. The
Intel 8088 The Intel 8088 ("''eighty-eighty-eight''", also called iAPX 88) microprocessor is a variant of the Intel 8086. Introduced on June 1, 1979, the 8088 has an eight-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers ...
had yields of about 20% on older systems, improving to 60% on the Micralign. Other microprocessors were designed from the start specifically for fabrication on the Micralign. The
Motorola 6800 The 6800 ("''sixty-eight hundred''") is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System (later dubbed ''68xx'') that also included serial and parall ...
was produced using contact aligners and sold for $295 in single units.
Chuck Peddle Charles Ingerham Peddle (November 25, 1937 – December 15, 2019) was an American electrical engineer best known as the main designer of the MOS Technology 6502 microprocessor, the single-board computer, and its successor, the Commodore PET per ...
found customers would not buy it at that cost and designed a low-cost replacement. When Motorola management refused to fund development, he left and moved to
MOS Technology MOS Technology, Inc. ("MOS" being short for Metal Oxide Semiconductor), later known as CSG (Commodore Semiconductor Group) and GMT Microelectronics, was a semiconductor design and fabrication company based in Audubon, Pennsylvania. It is ...
. Their
MOS 6502 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small ...
was designed specifically for the Micralign in mind, with a combination of high yield and smaller feature set allowing them to hit their design cost of $5 per unit. They introduced the 6502 only a year after the 6800, selling it for $25 in singles, and sold the subsequent 6507 with their
RIOT A riot or mob violence is a form of civil disorder commonly characterized by a group lashing out in a violent public disturbance against authority, property, or people. Riots typically involve destruction of property, public or private. The p ...
support IC to
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for a total of $12 per pair.


Later generations

Several improvements were introduced into the line to adapt to changes in the IC market. One of the first, on the Model 110, was the addition of an automated wafer loader, which allowed the operators to rapidly mask many wafers in a row. The Model 111 was a single-wafer model that replaced the 100, and could be adapted for use with 2-, 2.5- or 3-inch wafers, and optionally 4×4-, 3.5×3.5- or 3×3-inch masks. The Model 120 was a 111 with automatic wafer loading. The 130 worked with 100 mm wafers and 5×5-inch masks on a single wafer system, and the 140 added wafer loading to the 130. Any existing model could be adapted to other wafer and mask sizes, or add wafer loading, through conversion kits. The second-generation Micralign was introduced in 1979. This offered higher resolutions and the ability to work with larger wafers, but also cost much more at $250,000, . This higher price was offset by its ability to print more chips per wafer, due to the smaller feature sizes. 1981's Model 500 increased throughput to 100 wafers an hour, offsetting its $675,000 price, via improved throughput. By the early 1980s, Perkin-Elmer was firmly in control of the majority of the aligner market, in spite of concerted efforts on the parts of many companies to enter the space. Between 1976 and 1980, overall company sales tripled to $966 million, , of which $104 million was from the Microlithography Division, making it the single largest division of the company, and by far the most profitable.


Exiting the market

While Perkin-Elmer was introducing the Micralign, several other companies were working on different solutions to the same basic problem of focussing a light across the ever-growing wafers. GCA, formerly Geophysical Corporation of America, had been working on a concept that focused on only a small part of the wafer at a time, magnifying the image of the mask about 10-to-1 so it could shine more light through a much larger mask and make up for the fact that it used only a single band of UV light.
IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
had purchased one at about the same time the Micralign came to market, but gave up on the system and concluded it could never work. By 1981, GCA had solved the problems in the stepper system. During that period, the chip industry had continually moved to denser features and more complex designs. The Micralign was running out of resolution, while the additional magnification in the GCA system allowed it to operate at finer feature sizes. With roughly the same speed that the Micralign ended sales of contact printers, GCA's stepper ended sales of the Micralign. Perkin-Elmer had simply not listened to its customers who were clamoring for higher resolution, and ignored the
research and development Research and development (R&D or R+D), known in some countries as OKB, experiment and design, is the set of innovative activities undertaken by corporations or governments in developing new services or products. R&D constitutes the first stage ...
of newer systems. Instead of steppers, the Model 600 bet on Deep UV (note: correcting interview "EUV" blooper) (DUV) as a solution to the resolution problem. IBM used these to run a memory chip series, but no one else had an effective photoresist that worked in DUV, and few other customers purchased the system. Steppers were far slower than the Micralign and much more expensive, so sales started very slowly, but by the mid-1980s the stepper was rapidly taking over the market. In an effort to stay in the market, in 1984 Perkin-Elmer purchased Censor, a stepper company from
Liechtenstein Liechtenstein (, ; ; ), officially the Principality of Liechtenstein ( ), is a Landlocked country#Doubly landlocked, doubly landlocked Swiss Standard German, German-speaking microstate in the Central European Alps, between Austria in the east ...
. The product never made major inroads in the market, and in spite of GCA's bankruptcy in 1987, Perkin-Elmer decided to give up on the Microlithography Division and put it on the market in April 1989, along with their
electron-beam lithography Electron-beam lithography (often abbreviated as e-beam lithography or EBL) is the practice of scanning a focused beam of electrons to draw custom shapes on a surface covered with an electron-sensitive film called a resist (exposing). The electron ...
(EBL) division. The EBL work quickly sold, but the aligner division lingered. In 1990 it was purchased by the Silicon Valley Group (SVGL) in a multi-way deal involving IBM whose involvement was brokered by
Nikon (, ; ) is a Japanese optics and photographic equipment manufacturer. Nikon's products include cameras, camera lenses, binoculars, microscopes, ophthalmic lenses, measurement instruments, rifle scopes, spotting scopes, and equipment related to S ...
. SVGL was purchased by
ASML Holding ASML Holding N.V. (commonly shortened to ASML, originally standing for Advanced Semiconductor Materials Lithography) is a Netherlands, Dutch multinational corporation that specializes in the development and manufacturing of photolithography mach ...
in 2001.


Notes


References


Citations


Bibliography

* * * * * * * * * * * {{Cite interview , title=Oral History of Chuck Peddle , last=Peddle , first=Chuck , interviewer=Doug Fairbairn and Stephen Diamond , date=12 June 2014 , url=https://www.youtube.com/watch?v=enHF9lMseP8 Lithography (microfabrication) Machines