Glossary

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butting error -

A measure of the misalignment between adjacent scan areas when using the vector scan technique.

 

electron beam lithography -

A process for transfering the circuit layout onto a substrate. A more detailed description is available.

 

flood dispense -

A technique used to dispense substance onto a wafer.

 

Guassian round beam -

A type of beam used for electron lithography techniques. Normally one fourth the smallest pattern dimension.

 

lateral magnification error -

A geometric effect which occurs in lithography methods involving a mask. As the radiation source is concentrated in a single point, and the mask is seperated from the substrate, the angle at which the radiation passes through the mask differs. In the center of the wafer, the radiation is perpendicular to the wafer, but out towards the edges of the wafer the angle is acute. Therefore, a general enlargement of the features takes place, with features further out from the center being enlarged more than features closer in. Another geometric effect in such systems is shadow printing.

 

mask-

A device for delineating the areas of a wafer which should be exposed. Typically, a mask is a composed of a non-absorbing substrate and a layer of absorbing material on top of it. The pattern data is used in removing areas of the absorbing material. See specifically x-ray mask.

 

pattern data -

The data describing the circuit layout.

 

pattern dimension -

The size measure of shapes in the circuit layout.

 

raster scan -

A scanning technique where the beam scans line by line a section of the surface. The beam is turned on or off depending on whether the current pixel is to be exposed or not. Compare with vector scan. A more detailed comparison is available.

 

shadow printing -

A geometric effect which occurs in lithography methods involving a mask. If the exposing radiation cannot be tightly focused, then a small zone of "shadow" is created at the edges of surface features which is only partially exposed. This effect reduces the attainable resolution of such lithography systems. Another geometric effect in such systems is lateral magnification error.

 

spin coating -

A technique used to coat wafers with a given substance. The substance is first dispensed onto the wafer by way of flood dispense or spread dispense. The wafer can either be stationary (see static dispense) or moving (see dynamic dispense). Once the substance has been dispensed, the wafer is spun up to high speed and the substance spreads evenly and dries. The higher the spin acceleration, the more uniform the coating. Alternatives include: vapor priming (in some cases).

 

vapor priming -

A technique used to coat wafers with a given substance. The substance is first vaporized, and then the wafer is exposed to the vapor. Advantages are more efficient use of substance, decreased contamination from particles in original solution, and that multiple wafer can be coated simultaneously. Alternatives include: spin coating.

 

variable shaped beam -

A type of beam used for electron beam lithography techniques. Two square aperatures are used to size a rectangle appropriate for the current feature.

 

vector scan -

A scanning technique where the beam is positioned over an area of the substrate, and the features in that area (according to the pattern data) are drawn out using lines. The beam remains on at all times. Compare with raster scan. A more detailed comparison is available.

 

x-ray mask -

A device for delineating the areas of a wafer which should be exposed to x-rays during the exposure stage of x-ray lithography. The x-ray absorber is usually gold (Au). There is not yet a standard substrate material for x-ray masks, though the most promising is a combination of boron nitride and polyimide. See also mask.