In a particle-optical projection system a pattern is imaged onto a target by means of energetic electrically charged particles. The pattern is represented in a patterned beam of said charged particles emerging from the object plane through at least one cross-over; it is imaged into an image with a given size and distortion. To compensate for the Z-deviation of the image position from the actual positioning of the target (Z denotes an axial coordinate substantially parallel to the optical axis), without changing the size of the image, the system includes a position detector for measuring the Z-position of several locations of the target, and a controller for calculating modifications of selected lens parameters of the final particle-optical lens and controlling said lens parameters according to said modifications.

Particle-optical projection system

An projection exposure apparatus and method for illuminating a transfer pattern and forming an image upon a mask for exposure from the illumination light and transfer exposing the image of the pattern of the mask under the illumination light Switching is performed between a normal illumination condition and a modified illumination condition based upon the numerical aperture of the illumination light; wherein the normal illumination condition occurs when the light quantity distribution at the illumination pupil plane is in a first region, including the optical-axis; and the modified illumination condition occurs when the light quantity distribution at the illumination pupil plane is in a second region, not including the optical-axis and wherein the pupil plane is an optical Fourier conversion surface of a pattern surface of the mask in an illumination system

Exposure apparatus and method

Lithography is a field in which advances proceed at a swift pace. This book was written to address several needs, and the revisions for the second edition were made with those original objectives in mind. Many new topics have been included in this text commensurate with the progress that has taken place during the past few years, and several subjects are discussed in more detail. This book is intended to serve as an introduction to the science of microlithography for people who are unfamiliar with the subject. Topics directly related to the tools used to manufacture integrated circuits are addressed in depth, including such topics as overlay, the stages of exposure, tools, and light sources. This text also contains numerous references for students who want to investigate particular topics in more detail, and they provide the experienced lithographer with lists of references by topic as well. It is expected that the reader of this book will have a foundation in basic physics and chemistry. No topics will require knowledge of mathematics beyond elementary calculus.

Principles of Lithography

A memory circuit power management system and method are provided. In use, an interface circuit is in communication with a plurality of physical memory circuits and a system. The interface circuit is operable to interface the physical memory circuits and the system for simulating at least one virtual memory circuit with a first power behavior that is different from a second power behavior of the physical memory circuits.

System and method for power management in memory systems

There is disclosed a method for forming micro patterns in a semiconductor integrated circuit device with high productivity and high accuracy. A photolithography having high throughput and electron beam lithography using a reticle and having relatively high throughput and high resolution are selectively used so as to obtain highest throughput while satisfying accuracy and resolution required for each product/layer. In the case of using the electron beam lithography, a non-complementary reticle and a complementary reticle are selectively used so as to obtain highest throughput while satisfying required accuracy and resolution. Thus, productivity and integration can be improved for the semiconductor integrated circuit device.

Semiconductor device and a manufacturing method of the same

The imaging concept of electron projection lithography (EPL) with silicon stencil reticle is explained. A silicon membrane thickness of 1 - 4 micrometer is suitable for the reticle. A scattering contrast of greater than 99% is expected. Nikon EB stepper's dynamic writing strategy of discrete exposure on a sub-field by sub-field basis with deflection control of the electron beam is explained. The basic system configuration of EB stepper is introduced. Examples of error budget for CD variation and Overlay/Stitching are shown. Nikon's policy for countermeasures for critical issues such as proximity effect correction, sub-field/complementary stitching and wafer heating influence are explained. For extensibility down to 70 nm and below, both exposure tool and reticle should be improved.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Nikon EB stepper: its system concept and countermeasures for critical issues

Segmented reticles are disclosed for used with charged-particle-beam projection-microlithography apparatus. Such reticles comprise multiple mask subfields and a support grid, of intersecting struts, having an upstream-facing surface and a downstream-facing surface. Alignment marks are situated on the upstream- or downstream-facing surface. The projection-microlithography apparatus comprise a beam source, an illumination system, and a subfield-selection deflector. A second deflector downstream of the reticle further deflects the beam to impart a change in a parameter of the beam to correct reticle distortion. A correction-optical system can further change one or more characteristics of the beam downstream of the reticle to correct reticle distortion. A detector determines actual alignment-mark positions relative to ideal positions, and a controller calculates therefrom a required change to be imparted to the charged particle beam to correct the reticle distortion.

Projection-microlithography apparatus, masks, and related methods incorporating reticle-distortion measurement and correction

Evaluation methods are disclosed for evaluating the image-forming performance of charged-particle-beam microlithography systems, especially with regard to astigmatism and focus. In an embodiment, a subfield containing an evaluation pattern is subdivided into multiple regions. In the various regions, the respective line-and-space (L/S) pattern elements are oriented such that the elements in one region extend in a direction that intersects the direction, in the object plane of orientation of the pattern element in another region. The evaluation pattern is transferred lithographically to a resist film on a substrate. The developed resist, when observed at a magnification at which individual L/S pattern elements are not resolved, reveals a “shadow region” having a particular profile. The profile is a function of one or more parameters (e.g., astigmatism and focus) of image-forming performance.

Methods for determining focus and astigmatism in charged-particle-beam microlithography

Charged-particle-beam (CPB) projection-exposure methods, apparatus, and reticles are disclosed that can be used for efficiently and accurately measuring and correcting various reticle distortions. A reticle is segmented into multiple exposure units grouped into stripes. In a stripe, peripheral exposure units define second alignment marks for measuring reticle distortion arising from loading the reticle in the CPB projection-exposure apparatus. The reticle includes struts arranged into a grillage separating individual exposure units from one another. The struts define first alignment marks for measuring reticle distortion arising from reticle fabrication. The positions of the first alignment marks are measured in advance to obtain distortion data for each respective exposure unit. After loading the reticle in the CPB projection-exposure apparatus, the positions of the second alignment marks 51 are measured to obtain data on reticle distortion arising from loading the reticle. These data are used to calculate the actual distortion of each exposure unit, and projection parameters are adjusted to correct for such actual distortion during projection-exposure.

Charged-particle-beam microlithographic methods for correction of reticle distortions

Methods and devices are provided for performing adjustments of illumination uniformity obtained from a charged-particle illumination-optical system as used, e.g., in a charged-particle-beam (CPB) microlithography apparatus. The adjustments are based on measurements of illumination-beam current density. The device includes an aperture plate (desirably a silicon membrane), defining a tiny measurement aperture (desirably about 1 μm diameter), mounted on the reticle stage at the reticle plane. The illumination beam is scanned over the aperture. Charged particles of the beam passing through the aperture are directed to a beam-current detector on or at the substrate stage. The membrane desirably has a thickness of about 1 to 3 μm. The measurement aperture allows the distribution of current density of the illumination beam to be measured highly accurately. The thinness of the membrane allows the membrane to scatter incident CPB radiation rather than absorbing the radiation, thereby preventing thermal deformation of the membrane.

Takehisa Yahiro

Papers

Nikon EB stepper: its system concept and countermeasures for critical issues

Projection-microlithography apparatus, masks, and related methods incorporating reticle-distortion measurement and correction

Methods for determining focus and astigmatism in charged-particle-beam microlithography

Charged-particle-beam microlithographic methods for correction of reticle distortions

Devices for measuring and adjusting illumination uniformity obtained from a charged-particle illumination-optical system