Brief introduction of electron beam lithography system and UV 3 positive resist
Japan JEOL's JBX-5000LS electron beam exposure system electron gun source for the LaB6 thermal field emission; exposure method for the double Gaussian vector scan direct write; electron beam acceleration energy fixed 25 keV and 50keV two files, leads to a circular beam spot diameter 8 nm; Exposure limit of 30 nm; Graphic overlay accuracy ± 60 nm (3 σ); Identified alignments marked as concave troughs and raised metal strips with position accuracy less than 0.1 μm; Control The machine is a DEC V AX system.
The function of the resist is to record and transfer the exposed pattern, which is usually an organic polymer that dissolves in solution. Common indications of resist in the process include resolution, sensitivity, contrast, corrosion resistance, thermal stability, adhesion to the substrate, and ease of storage. The most traditional electron beam resist is PMM A (polymethylmethacrylate).
PMM A positive resist, high resolution, commonly used in nanoscale microfabrication. But its biggest drawback is impatient plasma etching, high temperature gel easily flow, and the sensitivity is very low, the critical dose than other resists more than 10 times.
Therefore, PMMA is not suitable for bulk silicon recession CMOSFinFET devices and circuit fabrication that are compatible with mainstream CMOS processes. Because of the same basic characteristics of e-beam resists as those of general resists, many of the resists used in deep-submicron optical exposure systems can be used in electron beam exposures. The United States Shipley's UV 3 positive resist is a modified soluble chemical amplification formerly used for DUV exposure with a nominal resolution of 0.25 μm.
UV 3 contains a copolymer of hydroxystyrene and t-butylacrylate and therefore has high thermal stability, reduces the sensitivity to airborne impurities that diffuse through the gel, and suppresses the formation of photoacid generators Affect the sensitivity of plastic. In this paper, UV 3 positive resist is applied to electron beam lithography to fabricate a groove pattern on a bulk silicon recess CMOS FinFET. The target of the process is that the width of a groove pattern on a 100 mm silicon wafer is 150-200 nm, which is close to 90 degrees Straight trough surface.
In addition, the new silicon CMOS FinFE T device consists of two fine patterns: the convex line (line) and the concave groove (DI TCH). Since e-beam direct writing exposure is a low efficiency technique, it is important to reduce exposure time. It is the most basic way to reduce the actual area of the electron beam direct write exposure; at the same time, all the graphics area is far less than the rest of the free area.
Therefore, the use of negative resist for printed convex line patterns and the use of positive resist in printing groove patterns are the basic requirements for direct exposure to electron beams on large area silicon wafers. In this paper, groove patterns are made by using UV 3 positive resist.