Optimization of resist shrink techniques for contact hole and metal trench ArF lithography at the 90-nm technology node

Abstract

Two fundamentally different approaches for chemical ArF resist shrinkage are evaluated and integrated into process flows for 90 nm technology node. The chemical shrin k and the corresponding gain in process window is studied in detail for different resist types with respect to CD uniformity through pitch, linearity and resist profiles. For both, SAFIER and RELACS material, the sensitivity of the shrink process with respect to the baking temperature is characterized by a temperature matrix to check process stability, and optimized conditions are found offering an acceptable amount of shrinkage at contact and trench levels. For the SAFIER material, thermal flow contributes to the chemical shrink which is a function of the photoresist chemistry and its hydrodynamic properties depending on the resists' glass transition temperature (Tg) and the baking temperature: at baking temperatures close to Tg, a proximity and pattern dependent shrink is observed. For a given resist, line-space patterns and contact holes shrink differently, and their resist profiles are affected significantly. Additionally, the chemical shrinkage depends on the size of contact holes and resist profile prior to the application of the SAFIER process. At baking temperatures below Tg some resists exhibit no shrink at all. The RELACS technique offers a constant shrink for contacts at various pitches and sizes. This shrink can be moderately adjusted and controlled by varying the mixing bake temperature which is generally and preferably below the glass transistion temperature of the resist, therefore no resist profile degradation is observed. A manufacturable process with a shrink of 20nm using RELACS at the contact layer is demonstrated. Utilizing an increased reticle bias in combination with an increased CD target prior to the chemical shrink, the common lithography process window at contact layer was increased by 0.15um. The results also indicate a possibility for an extension of the shrink to greater than 50nm for more advanced processes.

Novel chemical shrinkage material for small contact hole and small space patterning

“…The process window of ICAP for 80 nm C/H patterning has almost same largeness as that of the original, non-processed wafer for 120 nm C/H patterning. This "bringing in" ofwider process margin ofthe original wafer was also observed in RELACS process 8 and is beneficial for small feature patterning. The EL of ICAP process at best focus is slightly smaller than that of RELACS process, but it exceeds RELACS over defocused area.…”

Proximity effect correction for the chemical shrink process of different type contact holes

“…Another group is resist related techniques, such as photo-resist developments, resist shrinkage technologies. Resist shrinkage technologies for example, there are thermal flow, RELACS etc [1][2][3][4][5][6][7]. RELACS process is introduced by AZ Electronic Materials to be realized the small contacts [8][9].…”