Photoresist is a chemical substance that becomes insoluble by exposure to ultraviolet light.

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Photoresist is used to form patterns for industrial processing

Photoresist is a light-sensitive chemical substance that is used to form a coating on a surface or substrate. This coating can then be exposed to a specific band of light, referred to as the photoresist’s action spectrum, to affect a desired change in the photoresist. This change causes the photoresist to either become soluble or insoluble to another chemical called the developer which will be washed over the photoresist.

Once developed, the photoresist that has been exposed to light in the action spectrum either remains or is washed away leaving a pattern that can then be used for further processing such as chemical etching, engraving, or lithography.




Photoresist sees widespread use in numerous technologies including micromachining

Photoresist is extensively used in the printed circuit board industry where the patterns created by its use layout the circuit connections or traces of printed circuit boards through the use of etching chemicals.

Another heavy user of photoresist is the semiconductor industry, where it is a crucial step in the photolithographic production of micro-patterns that are used to form the tiny circuits of individual semiconductor devices.

Photoresists have also found use in Biomedical engineering, holography, and micromachining. The last application, micromachining, is a rapidly advancing arena in industrial technology.

Also referred to as MEMS, short for MicroElectroMechanical Systems technology, micromachining has driven the use of photoresist to remarkable new heights. Special photoresists and substrates are carefully processed and developed repeatedly in micro-sized layers, forming fully functional micro-sized circuits, structures, and even entire machines such as gear sets, valves, mirrors, sensors, and gyroscopes. Some MEMS devices can be as small as a single micrometer.

DLP or digital light processing is a technique used in modern projection television sets that utilizes a microchip with thousands of microscopic mirrors on its surface, manufactured through MEMS technology, along with a light source to create smooth, high-contrast, jitter-free images.

Controlling the exposure of photoresists is critical to maintaining production

Many photoresist types exist to suit a large variety of applications, and the action spectra can vary from one to the next. It is critical to control the action spectra exposure settings, both the intensity of the light and the time of exposure, to avoid wasteful under or overexposure of the photoresist during processing and production.

To maintain these settings, a light meter with a spectral response as close to the photoresist’s action spectrum as possible is required to get an accurate idea of how well the photoresist is being exposed. Further complicating matters is the processing equipment where photoresists are exposed are frequently very compact and have minimal room for taking these measurements.

International Light Technologies is committed to providing a variety of unique, photoresist-specific instruments to assist our customers in making these often difficult measurements.


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NOTE: All XRD(XRL) series sensors are being re-designed. The new low profile series will be released in August 2016. Please contact for availability of all XRD(XRL) series sensors.


Application Common Sources Spectral Range ILT System Options
Click Links Below
Measurement Range Units
PHOTORESIST PC board-exposure systems,
UVA Sources, UV-Vis Sources
320-475 nm ILT5000, SED033/A/W 2e-9 to 2 W/cm²
    320-475 nm ILT2400, SED033/A/W 2e-7 to 2 W/cm²
    320-475 nm ILT1000/A/W 2e-7 to 2 W/cm²
    320-475 nm ILT1700, SED033/A/W 7e-9 to 4 W/cm²
    320-475 nm ILT2400, XSD140A 4e-8 to 7e-1 W/cm²
    320-475 nm ILT2400, XSD340A 8e-7 to 10 W/cm²
    326-401 nm ILT5000, SED033/B/W 3e-10 to 2e-1 W/cm²
    326-401 nm ILT2400, SED033/B/W 2e-8 to 2e-1 W/cm²
    326-401 nm ILT1700, SED033/B/W 50e-10 to 5e-1 W/cm²
    326-401 nm ILT1000/B/W 2e-7 to 2 W/cm²
    326-401 nm ILT2400, XSD140B 7e-8 to 1 W/cm²
    326-401 nm ILT2400, XSD340B 2e-6 to 30 W/cm²
Super Slim Sensor   260-400 nm ILT2400, SSD001 6e-6 to 0.9 W/cm²
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* All Radiometers/Photometers/Spectroradiometers are NIST Traceable.
* If units of measure are not shown please contact us (empirical units also available i.e. fc, fL, nits, lm/ft²).
Image courtesy of Sandia National Laboratories, SUMMiTTM Technologies,