Nitto Technology


See us by accuracy | To the limit of surface processing

Ultimate level of finishing technology for photomask surface.Nitto makes angstrom level of surface roughness available.

Photomask technology is used for various electronic devices, such as television, cellular phone, personal computer, PDA, etc. In order to enable minute patterns to be printed on the surface, the surface of a photomask must be made as flat as possible. At Nitto, a high standard of surface polishing is performed for photomasks to the angstrom (Å) level.

What is a photomask?

Photomasks are master components used to optically transfer circuit patterns or images on to silicon wafers and substrates. A circuit pattern is formed on a photomask surface, and this area with a transferred pattern shields off light radiated through the photomask. On a silicon wafer with an applied photoresist, this area irradiated with light is exposed by the light, which induces chemical reactions to alkalify the area. When washed with an alkaline solution, this portion, chemically reacting with alkali, is washed away and dissolves into the washing solution, leaving only the circuit pattern on the surface as if it was etched. That is, this portion functions as the negative film of the circuit.

Photomask

High-precision pattern forming is required for semiconductor integrated circuits.

While IT industry continuously offers improved products with more advanced performance and lighter weight, panel and semiconductor structures become more and more complicated, resulting in the need for pattern forming of a much higher definition image. The pattern width is dozens of nanometers. If this detailed pattern is not exactly and precisely transferred, defects are caused, such as misprint, distortion and warping, and the performance of the device will suffer. For this reason, highly advanced technology is required for the process of making circuit patterns on photomasks.

Absolutely flat surface is prerequisite for forming patterns on the surface.

A surface that is as flat as possible is necessary to form a pattern on a photomask. For example, if the surface is tilted or uneven, the pattern on the circuit board gets broken or warped, causing transfer failure of the high-precision pattern onto the substrate.

When a photomask surface is not smooth.

When a photomask surface is not smooth.

If the surface of a photomask is not smooth before generating patterns,

even an intended length of line cannot be drawn, due to the deviations caused by the concave/convex surface.

even an intended length of line cannot be drawn, due to the deviations caused by the concave/convex surface.

The substrate and transferred pattern become defective.

The substrate and transferred pattern become defective.

When a photomask surface is smooth.

If the surface of a photomask is smooth enough to form patterns on the top,

If the surface of a photomask is smooth enough to form patterns on the top,

intended lines can be correctly drawn on the surface.

intended lines can be correctly drawn on the surface.

Patterns can be transferred to the substrate exactly as designed .

Patterns can be transferred to the substrate exactly as designed .

Here's how to do it! Nitto's high-precision technology

Nitto's surface processing technology allows accuracy level of 1/10 nanometer.

Nitto's accuracy can provide 1Å (angstrom) of difference in surface roughness.

As you can understand from the previous explanation, photomask surfaces are required to be absolutely flat for the next process. For this reason, Nitto provides a high accuracy (1 angstrom) of surface roughness. 1Å (angstrom) is equivalent to 1/10 million mm. The surface required is an absolute flatness without any warp and contortion. Nitto's technology makes possible this surface level for large-size glass substrates.

Photomask

Photomask