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CST Clean Surface Technology Co.

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Production ProcessCST HT Phase Shift Blanks
CST Fringr Small CoatingZF11 : For large high definition photomask
HT type FHT typeTop type/bottom type half-tone mask

Production Process

Polished quartz or soda-lime glass is used for making mask blanks. Chrome and Chromic oxide are coated on the substrate.
This bilayer is formed by sputter device. We'll show you a general process below...

[Incoming inspection]

Checking scratch, chip and damege the plate has


Feature of CST film composition : CrO+Cr+CrO


[Pre-rinse with cleaning device]

Place substrate on a holder and rinse by dipping. Acid, alkaline, US treatment is done.
Occasionally UV treatment is necessary for the better wettability.

[Special inspection of film]

Measurement of reflectiveness, Optical density and film thickness


[Inspection after sputtering]

Check particle, dirt and PH with Halogen-lamp


[Prodction rinse]

After rinse through US treatment by DI water, lift to dry.

[PR coating]

We coat all sizes of substrate by spin method


Prebaking of PR surface by Hotplate


[Substrate inspection]

Checking defects using Halogen-lamp powered 600,000 lxs

[Final inspection]


[Load to sputter-machine]

Plate is stored in case, packaged, then shipped

CST Fringr Small Coating

This data shows a uniformity of PR surface after FS (Fringe Small) coating a GRX-M220 on a 700×800 size substrate targeting centered on 765nm, which performed 17nm range. Widely expanded patterning area compared to FF product, resulted in about 7mm as a fringe part. Now it covers size up to 800×960 as our product and developing 1220×1400 for use.

CST HT Phase Shift Blanks

CST has achieved success in an angle of inclination of the pattern cross-section forming right-angle with PS2013 madel, insted of sloping. Performing phase control for your own wavelength convenience, and applicable to adjust transmission volume with membrane composition.

[PS2013 model pattern cross-section(conpare to conventional product)]

[PS2013 model Thickness 1123Å Transmission and phase characteristics]

PS2013 365nm405nm436nm
Thickness 1123ÅTransmission5.0%8.6%12.0%
Phase Shift187.2°170.6°160.7°

ZF11 : For large high definition photomask

[Etching character of ZF11]

[Time of additional etching and loss volume of pattern-width]

[SEM photo of ZF11]

[Flatness change with CS8(1220×1400×13t)]
Flatness data below was all measured by the backside of a plate. Concave and convex is upside down when measured by front side.

[Face difference]
Plate will be returned to their nomal condition after removal of film.

Flatness change with ZF11(1220×1400×13t)]

[Flatness change with 800×920×8t]
Flatness data below is observed from film surface


HT type and FHT type

HT type based on Chromic oxide is preferable for high transmission purpose. We actually coat 30~70percent transmission as our performance.
FHT type based on Chrome, smaller wavelength-dependent is preferable for lower transmission purposes.
It has a transmission performance of 10~40 percent.

Top type / Bottom type half-tone mask

Process of top type half-tone mask
The now leading half-tone mask is produced by coating with half-tone film on the once patterned mask. This type(half-tone film lies on Cr film) is called a top type half-tone mask.

Exposure of half-tone mask

Half-tone blanks
Half-tone blanks consists of 3 layers: half-tone film (on the substrate), etching-stopper film(in the middle) and Cr film(on the top) This type is called a bottom type half-tone mask. Bottom type half-tone film is considered to be difficult to administer wet treatment alone.
CST is under development of half-tone blanks that can receive wet treatment.

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