EUVL is considered to be the next generation method of photo-lithography. This new approach requires manufacturing special- reflective in UV spectra – masks, which are significantly different from traditional transitive optical photo masks.
The EUVL mask blank consists of a reflective Mo-Si multi-layer deposited onto a 6Ó square quartz reticule.
The top structure of the mask is composed of a buffer layer (SiO2, 10-50 nm), absorber layer (Cr or TaN, 50-150 nm), and anti-reflective coating layer 5-50 nm). The most important requirements for those films are thickness non-uniformity <5% (3s), low defect density, deposition temperature below 150C, and low intrinsic stress (+/- 200 MPa) uniformly distributed across the layers to prevent distortion of the mask figure.
A new sputter deposition technique, developed at Sputtered Films, creates high quality oxide, nitride and oxi-nitride thin films.
In the S-GunTM magnetron, which consists of two conical type concentric targets with a central anode, the magnetron discharge is generated by MF (40 kHz) power supply.
An additional RF (13.56 MHz) power supply is connected to the targets (Fig. 1) eliminating MF discharge re-ignition during each half of voltage period. Lack of bombardment by high-energy particles diminishes growth
In the MF-RF coupled S-Gun, special electrical circuits enable better control of film uniformity, and lower substrate temperature during deposition. Superimposed RF discharge also decreases an intrinsic compressive stress inherent to reactively sputtered compound films. Fig. 2
shows low and repeatable stress in Cr, TaN, SiO2, CrOxNy, and TaOxNy films deposited by MF-RF coupled S-Gun on 8Ó Si wafers.
The S-Gun sputters up, so the substrate is placed active-side down on a wafer land.
This approach essentially reduces foreign particles and defects in the growing films.
Fig. 3 shows the Endeavor EUV process module design as a part of the systemÕs reticule handling mechanism. There is no front, back, or side contact of the mask in any stage of transfer from SMIF box to process module. Bevels of the mask are used to support reticule during transfer.
Unique LifTabª design allows the user to adjust lifting speed, further eliminating particle generation during the handling process.
For more information, please contact: Fig.1 Schematic diagram of MF-RF Coupled S-Gun.
Fig. 2 Stress in buffer, absorber, and anti-reflective films.
Fig. 3 Process module for EUVL mask coating.