Willard Earl Conley

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.

Polyhydroxystyrene Carbonate Esters for High Sensitivity Photoresists Having Autodecomposition Temperatures > 160°

There are particular polymeric materials having acid labile groups pendant to the polymer backbone which can be used to produce resist structures having autodecomposition temperatures greater than 160°C. The increase in autodecomposition temperature of the resist is achieved by selecting acid labile groups which upon acid catalyzed deprotection generate less stable intermediate carbonium ions than the t-butyl carbonium ion. Acid labile groups that provide increased autodecomposition stability include those capable of forming secondary aliphatic and deactivated secondary benzylic carbonium ion intermediates. There must be a hydrogen on a carbon adjacent to the carbonium ion in order for elimination of an alkene and a proton to occur and continue the chemical amplification process. The acid labile pendant groups can be part of a polystyrene homopolymer or part of copolymers containing styrene and maleimide units.

Single layer chemically amplified resist processes for device fabrication by x-ray lithography

Resist systems using synchrotron radiation x‐ray lithography for the fabrication of 0.25 μm (Leff) devices has been investigated [R. Viswanathan et al. (unpublished)]. In this study, a chemically amplified negative crosslinking IBM resist, CGR [W. Conley and J. Gelorme, J. Vac. Sci. Technol. B 10, XXXX (1992)], for use on the contact level was the focus. Linewidth control and contrast curves of this system have been studied as a function of a number of parameters including changes in formulations. Mask limited resolution to 0.25 μm feature size (line/space array) has been achieved using a 40 μm mask‐to‐wafer gap. More important for device fabrication, reproducibility of exposure latitude and resist bias has been demonstrated and will be discussed. Data on the effect of postapply and postexposure bake conditions on the process will also be presented. It is of interest to note that this resist shows little change in linewidth with respect to postexposure bake temperature. This resist system was modeled usin...

A new positive DUV photoresist optimized for 0.25 mm isolated lines

Abstract This paper reports on the Shipley/IBM developed UV4 positive DUV photoresist, which is particularly suitable for gate array applications. This resist shows ≥1.4 μm DOF for 0.25 isolated lines and ∼20% exposure latitude. The UV4 photoresist has been designed to have relatively high developer selectivity (∼8) and an R max of 3100A/s. In this case, we have opted for a lower developer selectivity and R max than those of UVIIHS photoresist. The UV4 photoresist also shows good photospeed, ≤30 mJ/cm 2 , excellent postexposure delay stability, ≥1 hour at 0.25 μm, and better etch resistance than UVIIHS resist.

Characterization Enhancements in Resist Photospeed

Current photospeed testing methods are based on dose to clear (E 0 ) or resist contrast (γ 10 ). Either method is inadequate for controlling sensitivity to within ±1.5%. We investigated various methods for improving these photospeed tests. Ranked in order of decreasing importance are: (i) controlling standing waves (reflectivity); (ii) choice of developer, (iii) develop time; and (iv) exposure pattern. Reflectiuty can be controlled by careful attention to resist thickness, addition of a bottom antireflective layer, addition of a low refractive index layer (AquaTar), or by using a thick photoresist. Moreover, we can utilize the whole dissolution curve rather than the one-point determination of the E 0 test