Optical: systems and elements – Lens – With reflecting element
Patent
1990-05-18
1991-08-20
Arnold, Bruce Y.
Optical: systems and elements
Lens
With reflecting element
355 43, 355 53, 359732, 359738, G02B 1700
Patent
active
050408828
ABSTRACT:
An optical projection system has been provided which is particularly suited for use in microlithography and includes a source of exposure energy for generating a beam of energy. A primary lens and mirror are located in the path of the beam for receiving the beam and passing only a portion of the beam therethrough. A refractive lens group is located in the path of the portion of the beam for receiving and transmitting that portion. A recticle element is located in the path of the portion of the beam and has a uniform thickness having a pattern on one surface thereof and an unpatterned portion adjacent thereto. The reticle element is positioned for permitting the portion of the beam to pass through its thickness and for reflecting the portion of the beam back through its thickness and the refractive lens group to the primary lens and mirror. The primary lens and mirror is positioned to receive the reflected beam and includes a surface for reflecting a portion of the reflected beam back through the refractive lens group and the unpatterned portion on the reticle element to a surface to be imaged. The reticle element includes a transparent element having a predetermined uniform thickness and having two parallel planar surfaces separated by that thickness. The reticle pattern on one of the planar surfaces is made from a material having a high degree of reflectivity with respect to optical exposure energy. The reticle further includes a covering physically contacting the reticle pattern and completely covering that pattern. The covering has an index of refraction with respect to optical exposure energy which is sufficiently lower than the reticle index of refraction to cause a small portion of the exposure energy striking the covering to be reflected with insufficient intensity to expose photoresist on a wafer but with sufficient intensity and phase shift to improve edge control and resolution of the projected image formed by the reflected reticle pattern.
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0.3-Micron Optical Lithography Using a Phase-Shifting Mask--Tsuneo Terasawa, Norio Hasegawa, Toshiei Kurosaki and Toshihiko Tanaka.
New Phase Shifting Mask with Self-Aligned Phase Shifters for a Quarter Micron Photolighography--Akihiro Nitayama, Takashi Sato, Kohji Hashimoto, Fumiaki Shigemitsu and Makoto Nakase.
Arnold Bruce Y.
Dang Hung Xuan
General Signal Corporation
Hubbard Robert R.
Kleinman Milton E.
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