Masao Kanazawa

New antireflective layer for deep-UV lithography

ABSTRACT This paper describes an anti-reflective layer (ARL) suitable for use in sub-half-micron and quarter-micron KrF excimer laser lithography. Advantages of the new anti-reflective layer include improved critical dimension (C.D.) control with the resist thickness and reduction ofnotching caused by reflection from the substrate. In contrast to a well-known anti-reflective coating (ARC) 1,2,3,4is applied by spin coating, we studied amorphous carbon (a-C:H) filmwhich we applied by plasma-enhanced chemical vapor deposition (PECYD). The new film has two major advantages: Its thickness is topographically conformal thanks to the CVDmethod, and it can be ashed together with the resist because it is an organic film. Wedetermined the most suitable conditions for forming the a-C:H film, by experimental measurements of refractive index n and extinction coefficient k and by varying parameters in simulations. An a-C:H film only 350A thick provided sufficient protection against reflectionand had a higher exposure/focus latitude than conventional films.

Gate oxide damage and evaluation techniques

The quantities of the gate damage in an ECR plasma are evaluated as charge-up gate currents with the technique which employs Al gate MOS diodes and their sensitive flat band voltage shifts with current stress. A general model for charge-up damage is proposed. A charge-up I- V characteristic in the ECR plasma is estimated applying this technique, showing good agreement with that derived from the model. It is also deduced that the same I-V of the test device as the real device is essentially required for the correct evaluation. In a barrel reactor damage, antennas do not show the simple current collecting effect which has been expected.