Revolutionizing the Semiconductor Industry Nanoimprint Lithography

Photolithography uses light to etch circuit patterns on the surface of silicon wafers. This technology, which has served as the mainstream semiconductor lithography equipment for half a century, is undergoing a transformation, moving toward the next-generation technology of nanoimprint lithography. Making use of its high-speed, high-accuracy wafer stages and precision-alignment systems, technologies that Canon has developed for its semiconductor lithography equipment, the company is working to become the first in the world to mass produce next-generation semiconductor lithography systems employing nanoimprint technology.

Overcoming Technical Limitations Through
New Technologies

The History of Semiconductor Miniaturization

While line widths have halved roughly every five years, progress has stalled since late 2000s.

Semiconductor chips are an essential part of the products we use every day, from home appliances to automobiles and smartphones. The evolution of semiconductor chips has progressed hand in hand with the miniaturization of circuit patterns. The key to this miniaturization has been shortening light-source wavelengths and developing lithography technologies that contribute to further miniaturization.
In the early 1990s, Canon introduced its i-line (365 nm wavelength) steppers, making possible 350 nm resolution for a variety of imaging applications. Later, new shorter wavelength light sources such as KrF lasers and ArF lasers were developed, efforts that culminated with the development in late 2000s of an argon fluoride (ArF) immersion lithography system capable of 38 nm-resolution patterning. Since that time, however, no further progress has been made, suggesting that miniaturization had reached its technological limit.
As an alternative to conventional approaches to realizing circuit miniaturization, Canon set its sights on nanoimprint lithography (NIL). Nanoimprint lithography, which can achieve line widths of a mere 15 nm, has the potential to significantly reduce production costs for device manufacturers, and is poised to revolutionize the semiconductor industry.

Out of the Lab and into the Realm of Practical Application

Unlike traditional lithography technology, which makes use of light to etch circuit patterns, nanoimprint lithography (NIL) fabricates nanometer-scale patterns by bringing the nano-pattern mold into direct contact with the resist material on the substrate surface. In essence, it is like pressing a concave mold into clay to create a convex impression. This new technology makes possible the precise formation of minute circuit patterns while achieving a high level of reproducibility.
This technology, however, involves many challenges. The circuit patterns are formed using direct transfer, requiring nm-level accuracy. The commercialization of NIL was also considered difficult because mass production requires a consistent level of fabrication accuracy over repeated use and the elimination of particles. Overcoming these daunting obstacles, however, was made possible through the combination of Canon hardware, software and material technologies, which promptly enabled NIL to become a commercially viable technology.

Tackling Numerous
Challenges Head-on

One of the commercialization technologies Canon made use of to overcome these challenges controls the amount and positioning of the resist that is applied to the wafer surface. Technology employed in inkjet printing, an area in which Canon has unique expertise, is used to finely control how much and where the resin is applied to prevent it from being squeezed out when the mold, or mask, is brought into contact with the resin, while also ensuring a uniform thickness of the resin layer. Also, when the mask is removed from the wafer, their relative positions must be controlled and optimized to prevent convex circuit pattern deformation. To this end, Canon has developed new technologies, including those capable of delivering enhanced nm-level control, to realize advanced technical capabilities. In this way, the company is making steady progress toward the realization of mass production.

Generating Synergies From Different Cultures

Canon is collaborating with U.S.-based Canon Nanotechnologies, Inc. (CNT), owner of some of the world's most advanced and unique technologies, to achieve its goal of mass producing nanoimprint lithography systems.
Essential to Canon's development of semiconductor lithography systems are, in addition to control and measuring technologies, as well as element integration technologies, the service and support knowhow that the company has cultivated to date. By merging these with CNT's cutting edge technologies, Canon aims to overcome current technological limits to break through the miniaturization barrier.
This collaboration with CNT offers many benefits that go beyond technical advances. The engineers at CNT, a new company established in 2001, are focused on cutting-edge R&D, and their development activities have had a positive, stimulating effect on Canon's own upand- coming engineers.

How Canon Nanoimprint Lithography Works

The history of photolithography dates back more than a half century. Although the technology has contributed to reducing the cost of semiconductor chips, as line widths grow narrower, it becomes more difficult to achieve sharp circuit pattern definition. Consequently, realizing further miniaturization requires a range of innovations, the result being ever-larger lithography systems. This is the reason why miniaturization is believed to have reached its technological limit.
Nanoimprint technology, however, does not require shorter-wavelength light-sources. Instead, it uses the simple approach of physically applying a mask into which circuit patterns have been cut. Not only does this approach have the potential to significantly reduce costs, it also produces extremely sharp circuit patterns and is expected to contribute to lower chip defect rates.

Nanoimprint lithography: 1.Inkjet technology is used to apply droplets of liquid resin, called resist, to the wafer surface, following the circuit pattern 2.A mold, called a mask, into which the circuit has been cut, is pressed like a stamp onto the resist applied to the wafer surface 3.Ultraviolet light is used to solidify the resist and form the circuit patterns, after which the mask is separated from the resist Photolithography: 1.Photolithography resist is applied to the wafer 2.A projection lens is used to reduce and project circuit patterns drawn on the reticle onto silicon wafers, causing a chemical reaction in the resist 3.Following development, the resist that was exposed to light is removed to create a circuit pattern