Theodore H. Fedynyshyn

Effect of acid diffusion on performance in positive deep ultraviolet resists

Two methods to measure acid diffusion in positive acid catalyzed resists are described. The first method employs a spectrophotometric titration to determine the acid concentration ([H+]) followed by measuring the ion conductivity (σ) of the resist film to determine the diffusion coefficient (D). This method allows the diffusion coefficient of acid in the resist to be determined at different temperatures ranging from room temperature to different post‐exposure bake (PEB) temperatures. The second method is based on the threshold acid density theory of image formation, which assumes that when a critical concentration of acid is reached, the developer solubility of the resist is changed. With this method, a constant level of acid can be followed at different PEB times and the diffusion coefficient determined. A comparison of the two methods to measure the acid diffusion coefficient will be made and the temperature dependence of diffusion for different types of organic acids will be presented. Based on a previ...

Correlation of UVIIHS resist chemistry to dissolution rate measurements

This article describes the correlation of UVIIHS resist chemistry to dissolution rate measurements as a function of resist processing conditions. The acid generation efficiency, α, for the UVIIHS photoacid generator is high, 0.027 cm2/mJ. The dissolution rate versus exposure curves show the excellent developer selectivity of UVIIHS, with n values >8 for all processes. The rmax values for this resist are above 20 000 A/s, which is higher than any positive resist previously reported. The extent conversion for deprotection is directly related to the dissolution rate changes; ∼30% deprotection correlates to the E0 dose for all process conditions evaluated. At 30%–40% acid produced, all of the deprotection chemistry is essentially completed. The chemical contrast, as measured by extent conversion versus exposure dose, is strongly affected by the postexposure bake (PEB) temperature, with 140 °C PEB showing higher chemical and lithographic contrast than the 130 °C PEB. Mack’s dissolution model has been shown to ...

Process optimization of the advanced negative electron beam resist SAL605

Electron beam lithography requires a high resolution resist system capable of maintaining tight linewidth tolerances. These tolerances require a resist process which yields the greatest process latitude. SAL601‐ER7 is an example of an electron beam resist which has demonstrated the ability to provide submicron resolution coupled with high resist sensitivity. This paper will focus on developing an optimized process for a new advanced negative electron beam resist (ANR), SAL605 which also utilizes a chemically amplified crosslinking system. The SAL605 electron beam resist is a next generation version of SAL601‐ER7, and as such has many of the same processing requirements. The effect of developer normality and development time on sensitivity and linewidth control with MF‐312 based developers will be presented. The effect of post‐exposure bake (PEB) temperature and time with respect to sensitivity and linewidth control will also be presented. We will show that there are processing windows for submicron resolu...

Lithographic and chemical contrast of single-component top-surface imaging (TSI) resists

A variety of different approaches were used in an effort to improve the photospeeds of single component TSI resists based on poly(4-hydroxystyrene). The variations included molecular weights, co-monomer partners, and selected substituents. The factors that were studied dramatically affected silylation rates, in one case by as much as an order of magnitude. However, when the silylation times were adjusted to compensate for the rate differences and silylation depths, only minimal differences in photospeed were observed. The apparent contrast measured by swelling upon silylation was very poor ((gamma) equals 1.5) while the contrast measured after etching was quite high, approximately ten times that of the silylation value.

DUV positive resist system designed for Micrascan use

The development of a new DUV positive resist, XP-9493, is reported. XP-9493 was designed for the Micrascan II exposure system. Its absorbance over the 245 - 252 nm wavelength range is 0.48/micrometers , substantially higher than that of APEX-E, which is approximately 0.2/micrometers . The dissolution selectivity, tan ((phi) ), of XP-9493, 7.7, is much higher than that of APEX-E, 4.1. Thus, XP-9493 is capable of higher resolution than APEX-E with better swing curve control. It is shown that the deprotection rate of this resist is proportional to the pKa of the photogenerated acid. This result leads to the prediction that protonation of the protected polymer may determine the rate of the deprotection reaction. Further study of the photospeed vs PEB temperature showed a two-tier activation energy for the deprotection reaction. At high PEB temperatures, >= 95 degree(s)C, the deprotection reaction is diffusion-limited, where the protonation step is rate limiting. The activation energy, Ea, under diffusion limited conditions is only 7.6 kJ/mole. At lower PEB temperatures, < 95 degree(s)C, the deprotection reaction is reaction-limited, where the deprotection of the protonated protected polymer is rate-limiting. Ea under these conditions is 26.3 kJ/mole. This behavior leads to lower linewidth shifts per unit PEB temperature change, (Delta) CD/(Delta) T, at the recommended process conditions. For XP-9493, (Delta) CD/(Delta) T is approximately 6 nm/ degree(s)C for 300 nm line/space pairs. XP- 9493 resolves 0.225 micrometers line/space pairs at 19 mJ, and 0.25 micrometers contact holes at 27 mJ. The 0.25 micrometers process window for XP-9493 is >= 1.0 micrometers depth-of-focus, with 25% exposure latitude on a MSII exposure tool.

Film life enhancement of chemically amplified electron-beam resists

A key resist requirement for electron beam sensitive resists is an extended film life of up to 12 weeks, the demands of which far exceed the reported film life of current high resolution acid catalyzed electron beam sensitive resists. Simple techniques are described which increase the coated film life of acid catalyzed electron beam resists, specifically MICROPOSITTM SALTM603 E-Beam Resist, to greater than 12 weeks. Evidence shows that water in the resist film is the likely cause of decreasing resist sensitivity. Finally, it is demonstrated that electron beam sensitive negative acid catalyzed resists have sufficient film life stability to be a viable choice for routine mask making applications.