Photolitography (intro, up to page 36) Flashcards
Absorption coefficient
The fractional decrease in the intensity of light
traveling through a material per unit distance traveled. Also called
Extinction Coefficient.
Adhesion promoter
A chemical that is applied to the surface of a wafer in
order to improve the adhesion of resist to the wafer, often by eliminating
water from the wafer surface.
Aerial image
An image of a mask pattern that is projected onto the
photoresist-coated wafer by an optical system.
Antireflective coating (ARC)
A coating that is placed on top (TARC, Top
Antireflective Coating) or below (BARC, Bottom Antireflective Coating) the
layer of resist to reduce the reflection of light, and hence, reduce the
detrimental effects of standing waves or thin-film interference.
Aspect ratio
The ratio of a feature’s height to its width.
Bake
Thermal annealing of the photoresist
Binary mask/ binary internsity mask
A mask made up of absorbing and transparent regions (for,example, one composed of chrome and glass) such that the transmittance of the mask is either 0 or 1.
Chemically amplified resist/CAR
A type of photoresist, most commonly
used for deep-UV processes, which, upon post-exposure bake, will multiply the number of chemical reactions through the use of chemical catalysis.
Catadioptric
An optical system made up of both refractive elements
lenses) and reflective elements (mirrors
Catoptric
An optical system made up of only reflective elements
mirrors
Critical dimension (CD)/Linewidth/feature width
The size (width) of a feature printed in resist, measured at a specific height above the substrate. (Over time, the meaning of “critical” has become vague, and it seems that any dimension worth measuring must be critical.)
Spatial coherence
The phase relationship of light at two different points in space at any instant in time. For mask illumination, the spatial coherence is determined by the range of angles incident on the mask.
Coherence illumination/Spatially coherent illumination
A type of illumination resulting from a point source of lightm that illuminates the mask with light from only one direction. This is more correctly
called spatially coherent illumination.
Condenser lens
Lens system in an optical projection system that prepares light to illuminate the mask.
Contrast enhancement layyer/material (CEL/CEM)
A highly bleachable coating on top of the photoresist that serves to enhance the contrast of an aerial image
projected through it. CEL results in improved resist sidewall angle, but at the cost of
reduced throughput. Condenser or
Mask or Proj
Corner rounding
The rounding of a nominally sharp, square corner of a printed lithographic feature due to the inherent resolution limits of the patterning process.
Cost of ownership
Cost estimate designed to help managers assessing the total cost of an investment, including the acquisition, the installation, the running cost and potentially the decommissioning. The running cost includes all the operational cost, including consumables, preventive and corrective maintenance, non-productive overhead,etc.
Deep ultraviolet(DUV)/deep-UV
A common though vague term used to describe light of a wavelength in the range of about 150 nm to 300 nm. Also called deep-UV.
Depth of focus (DOF)
The total range of focus that can be tolerated, i.e., the range of focus that keeps the resulting printed feature within a variety of specifications (such as linewidth, sidewall angle, resist loss, and exposure latitude).
Design rule
A geometrical rule that defines minimum widths and/or spacings used when laying out a mask pattern.
Design rule checker (DRC)
A software package that checks a chip design for compliance with a set of design rules.
Diffraction
The propagation of light in the presence of boundaries. It is this property of light that causes the wavefront to bend as it passes an edge.
Diffraction pattern
The pattern of light entering the objective lens due to diffraction by a mask.
Dioptric
An optical system made up of only refractive elements (lenses).
Dose-to-clear/clearing dose
The amount of exposure energy required to just clear the resist in a large clear area for a given process. Also called the clearing dose.
Exposure energy/exposure dose/dose
The amount of energy (per unit area) that the photoresist is subjected to
upon exposure by a lithographic exposure system. For optical lithography it is equal to the
light intensity times the exposure time. Also called the exposure dose, or simply dose.
Exposure field
The area of a wafer that is exposed at one time by the exposure tool.