Post-exposure processing

In other work, the impact of thermal processing on linewidth variation was examined and interpreted in terms of how the resist s varying viscoelastic properties influence acid diffusion (105). The authors observed two distinct behaviors, above and below the resist film s glass transition. For example, a plot of the rate of deprotection as a function of post-exposure processing temperature show a change in slope very close to the T of the resist. Process latitude was improved and linewidth variation was naininiized when the temperature of post-exposure processing was below the film s T. 

After the volunteer is dressed and outfitted with appropriate gear for the study, he/she may have to walk only a short distance to the field site or may need to be transported to the field site via a vehicle. When transporting the volunteer(s) by a vehicle, the seats of the vehicle should be covered with plastic sheeting. The volunteers should be escorted into the vehicle and asked to keep their hands off surfaces in the vehicle. The volunteers are then transported to the field site. The plastic seat covers need not be changed until after the volunteers have been transported back to the dressing area for post-exposure processing. The plastic seat covers should be changed before a new set of volunteers enters the vehicle. 

Post exposure process resists (a) additive processes (b) subtractive processes. 

Three approaches have been identified that reduce susceptibility of CA resists to airborne contamination. In the first, process engineering changes such as the addition of special activated carbon filters to the environmental chambers surrounding the exposure tools (76,79), overcoating the resist with a soluble protective film to isolate the resist from the environment (77,80,81), or modifications of the process flow to minimize the time interval between exposure and post-exposure bake have been shown to improve CA resist processibibty. 

Whole-body dosimeters are processed post-exposure as follows. The whole-body dosimeter is laid on a table covered with fresh aluminum foil and is sectioned into various pieces using a solvent-cleaned pair of scissors. The whole-body dosimeter is usually cut just at the knees to provide two lower leg sections, at the waist to provide an upper leg section, at the elbow to provide two lower arm sections, at the edge of each shoulder to provide two upper arm sections, and across the shoulders and down each side of the chest area to provide a front torso and back torso sample. The two-dosimeter sections from symmetrical parts of the body are combined to form one sample and wrapped in aluminum foil prior to storage. The upper leg, front torso, and back torso pieces are kept separate, and each is wrapped in aluminum foil prior to storage. 

The chemically amplified resists reported here for deep-UV applications require a post-exposure thermal treatment process step to effect the deprotection reaction. This step has proven to be critical, and in order to understand the processing considerations it is instructive to discuss, qualitatively, the various primary and secondary reactions that occur with these systems during both exposure and PEB, ie ... 

The process control of the post-exposure bake that is required for chemically amplified resist systems deserves special attention. Several considerations are apparent from the previous fundamental discussion. In addition for the need to understand the chemical reactions and kinetics of each step, it is important to account for the diffusion of the acid. Not only is the reaction rate of the acid-induced deprotection controlled by temperature but so is the diffusion distance and rate of diffusion of acid. An understanding of the chemistry and chemical kinetics leads one to predict that several process parameters associated with the PEB will need to be optimized if these materials are to be used in a submicron lithographic process. Specific important process parameters include ... 

Processes Exposure Wash-out Drying Post exposure... 

The post-exposure treatment of photopolymerized structures in resin and resist is of critical importance for the final retrieval of 3D structures [77]. Since development of positive or negative resists and resins is a wet process, the damaging effect of capillary forces should be considered during the rinsing and drying of the samples. 

In the photolithographic process, the functional layer is covered by a photoresist film. State-of-the-art circuits are fabricated with chemically amplified photoresists consisting of a polymer with an acid-labile pendant protection group, photoacid generator molecules (PAG), and additional additives [2], Upon exposure to UV radiation through a patterned mask, the PAG is decomposed generating a low concentration of acid. In a post-exposure bake... 

Sarin and its corresponding nontoxic hydrolysis products (IMPA, and additional methyl phosphonic acids) are predominantly eliminated via the kidneys which are thus more important for detoxification than the liver (Little et al, 1986 Waser and Streichenberg, 1988). Urinary excretion happens quite rapidly as demonstrated for single dose s.c. application of sarin, cyclosarin, and soman to rats (Shih et al, 1994). The terminal elimination half-life was found to be 3.7 =E 0.1 h for sarin and 9.9 0.8 h for cyclosarin. In contrast soman showed a biphasic elimination with terminal half-fives of about 18.5 h and 3.6 h (Shih et al, 1994). Maximum peak levels of sarin metabolites in urine were detected 10-18 h after exposure (Minami et al, 1997) and after 2 days hydrolyzed sarin metabolites had been excreted nearly quantitatively (Shih et al, 1994). In contrast, even at 5 days post-exposure soman metabolite recovery was only 62% (Shih et al, 1994). Excretion of soman from blood, fiver, and kidney compartments following cfiemical and enzymatic hydrolysis is considered a first-order elimination process (Sweeney et al, 2006). 

---