摘要:

We report on the fabrication of quasi‐one‐dimensional wires on modulation‐doped GaAs/AlGaAs using a novel conformable x‐ray mask technology which allows us to expose arbitrary sized samples, including samples much smaller than the membrane area, using our laboratory’s standard 31 mm‐diam silicon‐nitride x‐ray mask. After optical alignment, the sample and mask are brought into contact electrically, and then loaded into a specially designed cartridge which allows a vacuum to be pulled between mask and substrate. The vacuum causes the x‐ray mask to conform around the sample. We find that a vacuum hold down is necessary to allow easy separation of the sample from the mask with minimal risk to both.  

ISSN:1071-1023    

DOI:10.1116/1.585911

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Membranes are in wide use today as microsensors, vacuum windows, and lithography mask substrates. They are fragile and difficult to protect, however. We show that membrane strength, and thus process yield, are increased by a newly designed ‘‘skirted’’ membrane. This structure strengthens the attachment of membrane to support, reinforcing a region where fractures usually originate. The skirt design was applied to polysilicon membranes on glass supports, used for x‐ray lithography mask blanks, and was shown to increase strength three times over polysilicon or silicon‐rich nitride membranes on silicon supports, to anaverageof 1.5 GPa. More significantly, skirted polysilicon membranes exhibit fracture pressure differentials that are six times higher in the same comparison, having tremendous impact on process and application durability.

ISSN:1071-1023    

DOI:10.1116/1.585912

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

In this article, results will be presented on how different x‐ray mask substrate materials affect the quality of the alignment signal acquired through them. By affecting the signal quality, the different materials ultimately have a significant impact on the capability of the alignment system to discern the position of the alignment marks precisely. Data will also be presented on position measurement repeatability as a function of mark depth for the different mask materials. In the experiments, in‐house grown SiC and diamond films were used. Vendor SiC and SiN materials were also used. For comparison and reference, signals were acquired through polyimide and B‐doped Si as well. The alignment was done with a lab‐based Suss ALX100 system. Since the primary alignment effect of membrane materials is to reduce signal‐to‐noise ratio, mark recognition repeatability and signal contrast was used as the comparative performance criteria. Experiments were done in both bright field and nonscanning dark field modes from alignment marks with depths between 5 and 150 nm. The effects of the substrate material became more evident when it was attempted to align using shallow marks. The vendor SiC and diamond exhibited poor recognition repeatability when marks of less than 45 nm in depth were used in bright field or 75 nm in dark field. Antireflective coatings seem useful in improving the performance of some of these materials, especially in bright field alignment. With a one sigma repeatability budget of 10 nm, current alignment systems may have difficulties in reproducibly locating shallow marks (below 20 nm), which may be found on some of the very demanding levels, when aligning through any of the candidate materials. The need may exist for careful processing of the marks and/or improvement in the aligners ability to see through rough or highly absorbing mask materials.

ISSN:1071-1023    

DOI:10.1116/1.585913

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Finite element modeling is used in this article to describe the elastic deformation of x‐ray lithography masks due to chucking in the electron‐beam writer or the lithographic tool. The total overlay budget for the lithography of 0.25 μm ground rule devices is less than 0.1 μm (3 σ) including all possible sources of error. Chuck induced random deformation of x‐ray masks can contribute a significant amount to this overlay error [A. Chenetal., J. Vac. Sci. Technol. B10, XXXX (1992)]. In addition, errors could arise also if different chucking techniques are used in the writing and exposure tools [A. Chen, S. Lalapet and J. R. Malonado, J. Vac. Technol. B9, 3306 (1991)]. Based on the state of the art of the precision and accuracy of mask aligners and e‐beam writers, it is required that the mask deformation due to chucking should be kept below 10 nm (3 σ). Several finite element models were constructed to simulate x‐ray lithography masks under different chucking methods: (a) an idealized kinematic chucking, (b) full surface chucking, e.g., chucked by a vacuum ring, and (c) three point chucking. The maximum in‐plane deformation of the x‐ray mask membrane was normalized to the ratio of the modulus of elasticity of the mask support structure (Pyrex; trademark of Cornia Glass) and the chuck material. The calculated in‐plane deformations of the x‐ray mask membrane were compared among the various chucking techniques mentioned above. The results are helpful in the design of aligner and exposure tools from the point of view of selecting proper chuck materials and methods to minimize mask membrane deformations.  

ISSN:1071-1023    

DOI:10.1116/1.585914

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The influence of diffraction on the shape and size of features printed using x‐ray proximity printing is reviewed, and the effect of image blurring on these results is described. Diffraction can alter the shape of a printed feature, and the systematic shape changes observed in resist images can be explained using simple scaling based on Fresnel diffraction. In addition, the linewidth change with exposure dose is independent of feature type and size, and depends only on the square root of the mask to wafer gap. The shape of printed features and the linewidth change with dose can be modified by smearing the aerial image at the wafer plane. This can be achieved by adding beam divergence or by varying the angle of incidence of the x‐ray beam onto the mask (wobbling). A technique for incorporating wobble into an exposure system is described, and exposures of contact holes, spaces, lines, and line‐space arrays using this technique are presented. For example, 0.35 μm square contact holes normally print diamond shaped at a 40 μm gap. However, the same contact holes are round in resist when 4 mrad of wobble is incorporated into the exposure. The linewidth change for a 10% increase in dose is 24 nm at a 40 μm gap with 5 mrad of wobble. This linewidth change with exposure dose is larger than the 20 nm measured for exposures at a 40 μm gap without wobble. Finally, wobbling during exposure can either increase or decrease the absolute linewidth of a feature in resist at a given exposure dose.

ISSN:1071-1023    

DOI:10.1116/1.585915

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Diamond layers are of special interest for x‐ray mask fabrication because of their excellent optical and mechanical properties. Using a plasma activated chemical vapor deposition process, 2–5 μm thick diamond layers were deposited and characterized. Microhardness and Young’s modulus are found to be very close to the literature values of bulk diamond. A standard isotropic etching process was applied for membrane fabrication. The optical transparency and the thickness homogeneity were measured. Concerning surface roughness, scanning electron micrographs and atomic force measurements were evaluated. After irradiation of diamond masks with synchrotron light, a slight increase of optical transparency was found.

ISSN:1071-1023    

DOI:10.1116/1.585916

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A technique for replicating x‐ray masks with no magnification of the master mask pattern has been developed. This technique uses a raster scanning pattern with a synchrotron x‐ray source to eliminate pattern magnification due to the source divergence. Kinematic mounts were employed to reduce clamping induced distortions in the mask replication process and the metrology tool. Finite element analysis of the thermal response of the clamped master and replicate masks during exposure indicates the temperature increase of the two membranes during exposure is matched, so that thermal distortions are not transferred to the printed pattern.

ISSN:1071-1023    

DOI:10.1116/1.585917

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

During 1991 the Oxford Instruments’ compact synchrotron x‐ray source Helios was installed at IBM’s Advanced Lithography Facility, following factory tests in Oxford during 1990. The machine has met or exceeded all performance specifications at the East Fishkill site. Since January, 1992 it has been run routinely for lithography development work. Running and reliability statistics are being generated, and the results for the first five months are presented here.

ISSN:1071-1023    

DOI:10.1116/1.585918

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This article describes the CXrL aligner, an experimental x‐ray proximity lithography system developed at the University of Wisconsin Center for X‐Ray Lithography. The main features of the aligner are (1) exposure in an atmospheric He environment; (2) mask to wafer alignment error detection and correction during exposure; and (3) mask to wafer continuous gap setting based on capacitance gauges. The aligner consists of a three‐axes two‐state alignment system for continuous alignment error detection and a piezobased precision mechanical stage for alignment error correction. The wafer is held by a flat vacuum chuck and the mask is held by three vacuum suction cups located around the glass ring. Since the optical system is located outside of the synchrotron radiation path, alignment can be performed during the exposure. We have obtained a noise equivalent misalignment of 2 nm with an alignment signal response time less than 10 ms. An alignment signal repeatability (3σ) better than 0.06 μm has been achieved. In the preliminary evaluation of x‐ray printed patterns, we obtained an overlay accuracy of 0.18 μm, to which the measurement error contributes most.  

ISSN:1071-1023    

DOI:10.1116/1.585919

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A vertical stepper for synchrotron radiation (SR) x‐ray lithography has been developed. Evaluation tests have been done with SR light from the superconducting compact synchrotron ‘‘AURORA’’ located in SHI‐Tanashi Works, Tokyo. An overlay accuracy of less than 0.08 μm was obtained. A 0.2 μm line‐and‐space pattern was successfully resolved with a high‐aspect ratio. The designed specifications have been attained. The system is ready for the future generation ultra‐large‐scale integration applications.

ISSN:1071-1023    

DOI:10.1116/1.585920

出版商:American Vacuum Society    

年代:1992

数据来源: AIP