Drawing

Semiconductors are used in all sorts of devices, from Smartphones and games to personal
computers, appliances, and automobiles.
Of the various processes used in manufacturing semiconductor devices, the most importantis photolithography, the process of creating the fine patterns that form the circuits.
In this tiny, nano-level world, Ushio light plays a big role.

Photolithography: The main process of semiconductor manufacture
Building on the principle used to photographically replicate original documents on printing
paper, light is employed to create the paths used to fabricate circuits on substrates such as siliconwafers or glass. This process is referred to as “photolithography” (Figure 1). Aluminum or copper
embedded into the channels transferred from a circuit pattern to a substrate becomes the “wiring”
through which electricity travels. The finer the lines of this “wiring,” the smaller the elements
making up the heart of electronic components and the more compact the chips that can beproduced or the greater the functionality and performance that can be achieved.
What determines the line width that can be achieved is the wavelength of light. As shorterwavelengths allow reproducing lines of finer width, the wavelengths of the lamps used as lightsources have become shorter and shorter, starting with lamps of 365 to 436 nm, then moving
down to excimer lasers with wavelengths of 193 to 248 nm, and then to 13.5 nm EUV lightsources. The process of photolithography is extremely subtle work which could be compared totaking the 23 wards of Tokyo, dropping them into a 30-km circle, and then drawing innumerable
lines with a width of 0.1 mm onto the circle, and then repeating the process with multiple layers ofcolored drawings to create an electronic circuit of exceeding complexity.

From light source to device components, developed entirely by Ushio

Common platform＋Light sources Illumination
opticsMasktransport

Work
transport

Projectorlenses

After-salesupportUshio’s UX Series exposure system
Using core technology developed and owned entirely
by Ushio, this system fulfills all the requirements for a
final device used in production of a variety of sensors,
power semiconductors, and LEDs.

Reproduction of such finely detailed electronics circuits requires not only a stable, high-energy
light source of the appropriate wavelength for exposure, but optical technology including mirrors
and lenses that are capable of efficiently condensing light emitted by the lamp and projecting itwith a high degree of uniformity and collimation, transport technology appropriate for carrying the wide variety of hard glass or film
types onto which the light is projected (the substrates), the alignment technology necessary to position substrates of dimensions
exceeding 10 cm with precision on the order of a few microns, and the software technology necessary to control all of theseprocesses. And of course all of these elements must be combined into a well-balanced system.

Beginning with development and production of UV lamps for use with the photolithography systems used in manufacture of thefirst integrated circuits in the 1960s, Ushio has gone on to develop all of its own core technologies for such equipment, making
possible the development of photolithography systems (exposure systems) of its own. With its ability to optimize operation according
to the type of device being manufactured, Ushio’s exposure now plays a role around the world.
It now plays an indispensable role in the production of the digital devices that have come to play such an essential role in ourdaily lives. Such are Ushio’s UV lamps and exposure systems for ‘photolithography’.

“Drawing with light” The Mechanism
Fig. 1 Photolithography process diagram
RepeatResist application

ResistOxide film
Silicon
Wafer

Exposure

UV
Mask
ExposedResistResistDevelopment

Removal of exposed resist

Alignment

Etching

Etching to remove oxide film fromareas not protected by resist① A photosensitive material called a ‘photoresist’ is applied to the surface of the substrate (such as a silicon wafer)→② The photoresist is exposed tolight through a mask on which is drawn the circuit pattern, transferring the pattern to the resist→③ The image is developed and the resist is removed→④ The oxide film underlying the resist is removed by etching and the circuit is formed in the etched pattern. The process is repeated with a variety ofmasks in a series of operations to build up a complex 3-dimensional circuit.