Harbans S. Sachdev

Characterization of plasma-deposited organosilicon thin films☆

Abstract Preliminary experimental data on the chemical composition and properties of films 1200–2000 A thick from representative monomers of silanes, siloxanes and silazane are presented. Fourier transform IR spectroscopy, electron spectroscopy for chemical analysis (ESCA) and contact angle measurements were used to characterize the films as deposited at ambient temperature and after thermal treatment up to 300 °C. For an evaluation of the film integrity the relative pinhole density was determined using an electrolytic bubble trail technique. For the as-deposited films the elemental ratios derived from the ESCA study are similar to those calculated for the corresponding monomers. These analyses show that the post-deposition thermal annealing causes a significant change in the surface and bulk composition and consistently provides defect-free films.

Defect studies on single and bilayer resist systems

Defect detection equipment and procedures to qualify resist systems with regard to defects have been investigated. An analysis was carried out for two bilayer resist systems which were compared to a single layer resist. One of the bilayer resists was developed for the mid‐UV exposure range, the other for deep‐UV. It showed that the pinhole‐limited yield measured by metal–oxide–semiconductor test structures is approximately 10% lower for one of the bilayer resists compared to a single layer resist. The other bilayer resist scheme was compared to a single layer resist with regard to particulates. Here the dry‐developed bilayer resist scheme showed approximately four times higher additive defect densities than the wet‐developed single layer resist. A short dry etch process for opening an anti reflective coating underneath a single layer resist increased the defect densities. Water rinse steps are capable of reducing these defect levels substantially. The dry‐developed resist schemes had higher defect densiti...

Sensitivity enhancers for chemically amplified resists

The addition of phenolic compounds to positive tone chemically amplified resists has increased sensitivity by approximately 2X for Deep UV exposures and up to 5Xfor X-ray imaging. Sensitivity enhancement during e-heam exposures was only 20%. Additives like hydroquinone sensitize various acid generators including triphenyl sulfonium triflate (TPS) and N-tosyloxyphthalimide (PTS) without affecting contrast and image profiles. The sensitization occurs in poly(t-butyloxycarbonyloxystyrene) as well as in base soluble resins. With PTS, the predominant mechanism is believed to involve electron transfer from the excited singlet or triplet state of the additive to the acid generator. For onium salt, direct photolysis plays a significant role in acid generation so that the effect of the additives is not as great as with PTS.

New negative tone resists for subhalf micron lithography

Abstract New crosslinking type resist systems are described which use benzylic carbocation precursors carrying phenolic hydroxy group. The special feature of the new resists is the versatility of applications, ease of synthesis, high sensitivity, high contrast and a large process window. One such resist system has been used successfully in the back-end-of-the-line personalization for manufacturing advanced bipolar devices which required an exceptionally large process window. The new resist system is a promising candidate for surface imaging as well as for I-line, DUV and X-Ray applications.

New negative tone resists for sub-quarter micron lithography

A new acid amplified negative tone resist system is described which utilizes the formation of tetrahydropyranyl ether group for the crosslinking reaction. In a three component system, the phenolic groups of the matrix resin add to the dihydropyranyl groups of the crosslinker in the imaged areas. N-sulfonyloxy triflate or triphenyl sulfonium triflate are used as photoacid generators. The resist has excellent sensitivity to DUV, E-Beam, and X-Ray and is also used for positive tone surface imaging.

Improved underlayers for acid amplified resists

Abstract Acid amplified resists represent a major development in lithography in the last few years. It is recognized that for precise CD control with these resists in device manufacturing, it is required that the processing environment be free of any basic contaminants. Top coat protection of the resist films in conjunction with rigorous exclusion of basic chemical vapors in the work area has been recommended to minimize the effects of environmental contaminants. Another important variable in determining the resist performance is the effect of substrate chemistry which has received little attention in the literature. This paper provides an understanding of these effects and gives a general method to circunmvent the problem.

New silicon containing positive resist and its applications for sub-half micron lithography

Abstract New silicon containing photosensitive polymers have been synthesized using poly(phydroxybenzylsilsesquioxane-co-p-methoxybenzylsilsesquioxane) resins as starting materials and partially replacing the available -OH groups with 2,1-diazonaphthoquinone sulfonyloxy moiety. Bilayer resist formulations derived from these polymers have higher sensitivity and contrast as compared to the resists based on silicon resins/PAC mixtures for sub-micron and sub-half micron I-line, DUV, and g-line lithography.

New silicon-containing negative resist for bilayer lithography

The increasing use of high density integrated circuits has created a need for development of new resist materials and lithographic schemes involving process simplification in semiconductor device fabrication to lower defect levels and improve product reliability. Towards that goal, we have developed a new negative working photoresist applicable to a bilayer resist scheme using optical and E-beam exposures. In this paper, we discuss the synthesis and lithographic applications of the silicon containing resist PHBS-AZIDE. The resist comprises a single component in which the photoactive group, an azide moiety, is chemically bonded to the base polymer, poly(4-hydroxybenzylsilsesquioxane) via an esterification reaction. The new polymer is easily synthesized and has the advantageous properties of aqueous base developability, excellent oxygen RIE resistance and high sensitivity to DUV, i-line and E-beam exposures. Sub-half micron images have been demonstrated using PHBS-AZIDE as a thin top imaging layer in a bilayer mode.