All-dry development

A novel microlithographic application for photoinitiated polymerization involves the polymerization of a monomer and the locking-in of a plasma-sensitive host polymer so that plasma techniques can be used to carry out all-dry development, thus avoiding the problems of swelling and resolution limitation associated with standard resists. Some plasma-developable resists are described later in this section. 

One important area of resist research in recent years is the development of plasma-developable resist systems. The aim of plasma developable resists is to use nonsolvent, all dry development methods to avoid the problems of swelling and consequent resolution limitation associated with conventional resists. Much of the semiconductor fabrication process now utilizes plasma techniques as they are capable of providing high resolution images. An important consideration in this is that the plasma-developable resist images should stand up well to the plasma etching treatments. 

Repeated chromatography of the sample in the same direction with the chromatographic plate being dried before all re-developments. 

This section deals with process technologies associated with the bilayer process. Particular emphasis will be given to the development of an all-dry processing scheme including dry development and dry deposition of the Ag-compound sensitizing layer. 

At the same time, on a purely engineering basis, extensive work was conducted in all major developed countries to design and build large-scale reliable Ifeeze-drying plants that were able to handle batches of several tens—sometimes hundreds-of thousands of vials or ampoules in well-controlled sterile conditions. In parallel, an important amount of basic research was conducted in several laboratories to understand and monitor the Ifeeze-drying process. Our own work in the field started in 1954 and has been pursued ever since. 

All dry processes under development use a calcium-based sorbent to react with SO2 to form CaS03 and/or CaS04. All processes are once-through and the sulfated sorbent is normally land filled along with coal ash. The processes are classified as high-, medium-, and low temperature. 

Fig. 155 All-dry bilayer lithography (thermal development-02 RIE pattern transfer)...

The shift from aqueous base development to the dry development employing oxygen plasma is rather drastic and therefore many issues must be addressed before implementation of the new technology in manufacturing. First of all, a new equipment (etcher) is needed and the etch uniformity (across a wafer and wafer-to-wafer) is a very important issue from a tooling point of view. The all-dry TSI technique requires a silylation equipment as an additional tool set. 

Stationary phase Silica gel (DG Riedel, Hannover, FRG). Mobile phase Af, = benzene Mi = chloroform My = 1,2-dichlorobenzene M4 = n-hexane Ms = CCU M = dichloromethane M7 = ethyl acetate M = toluene M = benzene-dichloromethane (I I) M,o = chloroforin-CCL (7 3) M 1 = dichloromethane-toluene (7 3) M j = n-hexane-CCI4 (2,8) M 3 = chloroform-dichloromethane (7 3) M,j = benzene-toluene (1 1) M,s = chloroform-CsHs-dichloromethane, (6 2 2) Mi<, = acetone-water (6 4). Remarks All single component solvent systems were dried before use, development time 7-20 min, with all dry single component solvent systems the complexes are separated on silica gel layer by an adsorption mechanism and the Rf values of complexes investigated increase in the following order of the ligand acac < bzac < dibzac < ttfac < tfac < hfac. 

Standard soln. of potassium penicillin G prepared in doubly distilled water at cone, of I and 10 f>g/)tl. Appropriate volumes of the standard soln. and the potassium penicillin G dosage forms are applied with a IO-/1I Hamilton syringe, each application being dried in a nitrogen stream before another is made. Chromatograms developed in 7 X 28 X 22 cm glass-lined tanks lined with Whatman No. I filter paper. All plates developed until the solvent rises to within 5 cm of the top (ca. 50 min)... 

All glassware should be scrupulously clean and, for most purposes, dry before being employed in preparative work in the laboratory. It is well to develop the habit of cleaning all glass apparatus immediately after use the nature of the dirt will, in general, be known at the time, and, furthermore, the cleaning process becomes more difficult if the dirty apparatus is allowed to stand for any considerable period, particularly if volatile solvents have evaporated in the meantime. 

---