Applied Materials, Inc.

Etec Systems, Inc.

Robert Innes

Sergey Babin

Lee H Veneklasen

Robin Lynn Teitzel

David Trost

William A Eckes

Allan L Sagle

Chen Hwa

Jeffrey Varner

The present invention relates to methods of predicting proximity heating of resists in electron beam lithography in real-time as the writing proceeds enabling beam compensation in current and/or dwell time to be performed during writing. A method of using a precomputed kernel capable of proximity resist temperature evaluation in real-time as beam writing proceeds by scalar product of the kernel with a graded cell size coverage map. A shifted impulse response function is shown to give the kernel values accurate to within a few percent.

Real-time prediction of and correction of proximity resist heating in raster scan particle beam lithography

The present invention relates to methods and procedures for determining resist temperature during energy beam lithography and adjusting process parameters, including reducing the beam current, to compensate for increased resist sensitivity due to heating. The present invention relates to methods of predicting resist heating in real-time as the writing proceeds thereby enabling beam compensation to be performed in real-time. A linear superposition approximation is described that provides a procedure for estimating the resist temperature at the point presently being written from previously written points. The present invention makes use of the thermal history of the pattern previously written as that history is recorded in the line of pixels immediately preceding the line whose temperature is to be determined prior to e-beam exposure, and a single number representing the thermal history of lines written before the immediately preceding line. The iterative methods for calculating resist heating in the present invention may be implemented digitally on a variety of devices. In addition, specific analogue circuitry to reproduce this iterative method is described, leading to rapid calculations of resist heating. Advantages of the present invention include the prevention or mitigation of pattern blooming as incident electrons heat the resist and broaden the region of exposure.

Method and apparatus for real-time correction of resist heating in lithography

The present invention relates to methods of predicting proximity heating in real-time as the writing proceeds enabling beam compensation to be performed in real-time. Particular attention is given to vector scanning in which the pattern of writing does not follow prescribed kinematics, but the writing tends to cluster into cells. A library of standard cells is constructed. As writing of the pattern proceeds, the individual flashes are agglomerated into cells that are compared with standard cells to determine proximity heating in the resist as a function of the distance of the previously written cells from the point of present writing, and the elapsed time since writing a previously written cell. Present writing snaps to a sufficiently coarse space-time grid to limit the computational burden but fine enough the represent variations in temperature over space and time. Further agglomeration of cells into super-cells, super-super-cells, etc. are also described. An advantage of the present technique is its applicability to vector scanning and to stenciling techniques for writing patterns on the wafer surface, not dependent on foreknowledge of a particular pattern of writing, as is the case for raster or serpentine scanning.

Methods to predict and correct resist heating during lithography

The present invention relates to methods of predicting proximity heating of resists in electron beam lithography in real-time as the writing proceeds enabling beam compensation in current and/or dwell time to be performed during writing. A shifted impulse response function is shown to give proximity heating results accurate to within a few percent. A method of using a precomputed kernel capable of proximity resist temperature evaluation in real-time as beam writing proceeds.

Real-time prediction of proximity resist heating and correction of raster scan electron beam lithography

A shield assembly for reducing electron fogging effects in electron beam lithography. This shield, located between an electron beam column final aperture and the beam target, is of multiple vanes with sharp edges pointing towards the electron beam incident point on the target; the vanes are conically shaped and concentric around the electron beam path, which travels through the center of the assembly. Additionally, the sharp edges are such that they present oblique surfaces at the ends of the vanes angled between 10&deg; and 20&deg; relative to the outer vane surface and these oblique surfaces face towards the electron beam path. Furthermore, the shield assembly may also have the vanes angled towards the beam incident point such that the vertex of the conical vane assembly is coincident with the beam incident point.

Minimization of electron fogging in electron beam lithography

A laser beam or other parallel light beam divides at a beamsplitter into sample and reference beams. The sample beam reflects from a reflective surface back to the beamsplitter, and the reference beam reflects from a retroreflector back to the beamsplitter. The beams are then directed into a telescope. The angle between sample and reference beams at the telescope is proportional to the angle between the laser beam and the normal to the reflective surface. The telescope collects both sample beam and reference beam and transforms each beam into a sharply defined point image. The lateral separation between the two point images is proportional to the magnification of the telescope and to the angle formed at the telescope between the sample beam and the reference beam. If the reflective surface is accurately aligned relative to the laser beam, then the two point images are substantially superposed on one another. Alignment is performed by adjusting the orientation of the reflective surface, until the lateral separation between the two point images reaches zero or a predetermined value.

Laser reflector alignment

An electron beam pattern generating system for exposing a pattern on a substrate using a raster scan method. The system stores a rasterized representation of the pattern as a plurality of regular pixel dose exposure levels. These pixel dose exposure levels are evaluated by the system for one or more proximity effects and corrections to the dose exposure level and/or pixel location are calculated. The system includes apparatus for both calculation and storage of intermediate and final results as required. As they are calculated, the corrections are provided to an exposure dose modulator wherein they are applied to forming the pattern. Thus corrections for both long range and short range proximity effects due to both electron scattering and heating as well as for proximity effects due to global thermal expansion can be calculated and provided during run-time and a corrected pattern exposed.

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Richmond, CA, United States of America

Robert Innes