An e-beam test system has been developed to detect opens and shorts in three-dimensional networks of conductors embedded in a dielectric matrix. The specimens, which measure up to 100×100 mm, are tested electrically without making physical contact and without mechanical stepping. The system comprise two flood beams and a focused probe beam deflected over the full specimen area at a resolution of better than 3000 lines at 1–2 kV beam energy. One flood gun is located at the rear, the other at the front of the specimen. The change in secondary emission imposed by impinging electrons charging or discharging the surface is detected as voltage contrast which allows one to discriminate between uninterrupted and interrupted as well as shorted pairs of conductors. The physical concept, the contrast mechanism, and the electron optics of the system will be presented together with experimental results.

Articles you may be interested inElectron optics using multipole lenses for a low energy electron beam direct writing system Electron optical image correction subsystem in electron beam projection lithography Lie algebraic aberration theory and calculation method for combined electron beam focusing-deflection systems Electron and ion optical design software for integrated circuit manufacturing equipmentThe PREVAIL proof-of-concept ͑POC͒ system is described elsewhere in these proceedings. For theoretical as well as practical reasons, the operating conditions of POC were restricted to the special, albeit not necessarily optimum case, of the deflected beam following a particular trajectory in the lens doublet forming the backbone of the POC optics; this trajectory is referred to in optics as the ''fundamental off-axis imaging ray.'' To provide guidance for and evaluation of its operation, the necessary computer simulation software was developed in-house. The interaction between modeling and experimentation proved fruitful in achieving the primary objective, demonstration of feasibility of large-area reduction projection and beam scanning for next-generation lithography. Beyond that, the theory provides the means to investigate variations of the optics regarding configuration as well as setup, their impact on performance, and the direction for further improvements.

Variable axis lens of mixed electrostatic and magnetic fields and its application in electron-beam lithography systems J.Electron and ion optical design software for integrated circuit manufacturing equipmentThe concept of the curvilinear variable axis lens ͑CVAL͒ has been introduced for the optics of projection reduction exposure with variable axis immersion lenses, an approach to electron projection lithography reported elsewhere. In the proof-of-concept system the special case of a planar CVAL following the fundamental imaging ray of the lens system was implemented and next generation lithography-commensurate performance was demonstrated. The present work addresses the question of whether general types of CVAL with different configurations of the optical elements are practical and acceptable in performance. Specifically, an analysis is presented of the performance trends of such optics in terms of blur and distortion depending on configuration, number and position of the optical elements in the system, as well as their relative drive requirements.

A novel deflection system has been developed which essentially eliminates off-axis aberrations including the transverse chromatic aberrations by employing a variable axis lens (VAL) which shifts the electron optical axis in synchronism with the deflected beam. The system comprises two precision pole piece lenses to achieve telecentricity, two composite predeflection yokes, and two yokes positioned in the pole piece region of the final lens. The field of the latter yokes satisfies the condition for shifting the electron optical axis by the distance r. This condition is 1B(y)r(z) = 1/2 B(L) (z)r, where B(y)r denotes the deflection field of the yoke in the r direction, and B(L) the lens field on the geometrical lens axis. To successfully utilize this concept, higher order terms of the field expansions have been included in the field matching by designing yokes which satisfy first and third order conditions and dynamic focus correction coils whose field is proportional to B\\(L) (z). The theoretical analysis of the VAL concept will be discussed together with experimental results demonstrating proper shift of the electron optical axis through elimination of transverse chromatic aberrations and coma.

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