IC Knowledge - Glossary

Glossary of Integrated Circuit Terminology - P

P-Type - a semiconductor material that has been doped so that there is a much larger number of mobile holes than there are mobile electrons.
PAC - see Photoactive Compound.
Package - a protective container for electronic components with terminals to provide electrical and or optical access.
Parameter - a numeric measure of some characteristic of a device.
Parasitic - an undesired attribute of a device or circuit such as, strap capacitance, leakage, or devices, that reduce the performance of a circuit or device from ideal performance without the parasitic.
Pareto Diagram - a bar chart that plots failure modes from left to right - largest cause of failure to least cause of failure. A tool for identifying the most significant problems to help prioritize improvement efforts.
Partial Coherence - the numerical aperture of the condenser lens of and optical system divided by the numerical aperture of the objective lens of the system.
Parts Per Million - one part in a million. Abbreviated ppm and commonly used to express defect levels or concentrations. Passivation - a final layer or layers put on semiconductors to protect them against contaminants and mechanical damage.
Passive Components - components that do not amplify or switch signals. Examples include, capacitors, resistors, transformers, inductors, etc.
Pattern Generator - a system that takes CAD data and generates patterns. The system typically has a light source, a variable shape aperture, a reduction lens system, a blanking aperture and a stepping mechanism. At one time these systems were widely used to make masks. The systems form various sized shapes by moving a set of blades, the shapes are exposed onto the mask through the reduction optics system, once a shape is exposed the light source is blocked by the blanking aperture and the system steps to a new position. Repeating these actions over and over allows complex patterns to be built up.
Patterning - creating an image in a photoresist layer. PC Board - Printed Circuit Board - an insulating board with patterned conductive layers on it. Components including ICs are soldered down to a PC board to build up complex electric circuits.
PECVD - Plasma Enhanced Chemical Vapor Deposition - a where a plasma is used to accelerate a CVD reaction.
Pellicle - a thin transparent layer stretched over a frame above the surface of a mask or reticle. Pellicles are used to block particles from reaching the mask or reticle surface where the particle would be in the focal plane. Any particles on the pellicle surface are out of the focal plane and should not form and image on the wafer being exposed.
PGA - Pin Grid Array - an style of integrated circuit package with an array of pins of pins designed to be inserted into a socket on a printed circuit board. PGAs support very high pin counts and account for approximately 1% of package types shipped on a unit shipment basis. The use of PGAs is declining.
pH - the hydrogen ion concentration in a liquid expressed as a negative logarithm so that a pH of 1 has twice the hydrogen ion concentration of a solution with a pH of 2. A pH of 7 is neutral, less than 7 is acidic and greater than 7 is alkali.
Phosgene - chemical formula COCl₂, phosgene is a very toxic gas with a TLV of 0.1ppm. Phosgene has a moldy, hay like odor and is irritating. Phosgene is a reaction product that can form during chlorinated furnace cleans if sufficient oxygen isn't present.
Phosphine - chemical formula PH₃, phosphine is pyrophoric and is a very toxic gas with a TLV of 0.3ppm. Phosphine is combustible in the range of 1.2-98% and has a decaying fish like order. Phosphine is used as a dopant gas during CVD and as an dopant source for ion implant.
Phosphoric Acid - chemical formula H₃PO₄, phosphoric acid a relatively strong acid primarily used as part of aluminum etches and to remove silicon nitride. Phosphoric acid is commonly sold as a 85% solution and has a density of 1.70Kg/L. Phosphoric acid burns on contact with skin or eyes and the vapors will irritate or burn eyes or lungs.
Phosphorus - atomic symbol, P, phosphorus is the 15th element in the periodic table (atomic number 15) with an atomic weight of 30.91. A group V element phosphorus is a donor in silicon, i.e., makes silicon N-type. Phosphorus a commonly used N-type dopant and has a relatively high diffusivity compared to arsenic and antimony, other common N-type dopants, and a diffusivity and similar to boron, the most common P-type dopant.
Phosphorus Oxychloride - chemical formula POCl₃, phosphorus oxychloride is a liquid at room temperature and was at one time widely used as a source of phosphorus during pre-deposition processes. During the pre-deposition process, Nitrogen gas is bubbled through heated phosphorus oxychloride liquid. The nitrogen gas leaves the bubbler carrying vapor of phosphorus oxychloride into the pre-deposition furnace. Phosphorus oxychloride's vapor pressure ranges from approximately 8m of Hg at 0oC, 3mm of Hg at 25oC to 12mm of Hg at 50oC.
Phosphorus Pentafluoride - chemical formula PF₅, phosphorus pentafluoride is corrosive irritating gas.
Photo Active Compound - the chemical compound in photoresist that reacts to light and undergoes or initiates a chemical change.
Photolithography - lithography where the pattern is defined by a photographic process.
Photomask - see Mask.
Photoplate - the mask plate prior to a pattern being formed.
Photoresist - a photo sensitive chemical resistant to acid. Photoresists may be liquids that are spun onto wafers, or solid sheets that are rolled onto printed circuit boards.
Photoresist Coating - the process of coating a wafer with photoresist. Most commonly photoresist is spun onto a wafer at high speed to form a thin uniform layer.
Photoresist Developing - a process where an image exposed into photoresist is developed to create a pattern.
Physical Vapor Deposition - a process where a film is deposited on a wafer by a physical process, for example, evaporation or sputtering.
Pico - prefix meaning one trillionth (x10^-12), symbol is p.
Pin Grid Array - see PGA.
Pinhole - a small undesired hole in a photoresist film, deposited or grown film or opaque area on a photomask.
PLA - Programmable Logic Array - an array of logic elements that can be programmed to perform various functions.
Planar Process - an IC made in such a way that all of the PN junctions intersect the top surface of the semiconductor. In planar processing photolithography and etching create openings in films on the surface of the wafer and the opening define diffused and or implanted junctions formed into the wafer.
Planarize - a process where something is made more flat.
Plasma - a gas weekly ionized to produce electron - ion pairs and neutral chemically reactive specie.
Plasma Etch - a technique whereby radio or microwave frequency radiation is coupled into a low pressure gas to ionize the gas producing disassociation of the gas molecules into more reactive specie. Compounds containing halogens such as, fluorine (F), chlorine (Cl) or bromine (Br) are typically used as etch gases. When the compounds disassociate in the plasma, the resulting highly reactive halogen atoms or halogen compounds perform chemical etching in a generally isotropic manner. Typical plasma etching conditions are high pressure, low ionization levels and low ion energies relative to other dry etch techniques.
PLCC - Plastic Leadless Chip Carrier - a relatively high pin count package that along with QFPs makes up approximately 19% of IC packages on a unit basis. PLCC usage is declining.
PM - see Preventive Maintenance
PMOS - a MOS device that uses holes as the carrier, holes carry a positive charge hence PMOS.
PN Junction - an area in a semiconductor where a P type material and an N type material are in direct contact.
Poly - abbreviation for polysilicon.
Polycide - a silicide formed over polysilicon. Widely used in DRAMs.
Polycrystalline - a material made up of grains of crystalline material where the grains are randomly oriented relative to each other. The material has short range but no long range order.
Polysilicon - silicion with randomly oriented grains where each grain is made up of single crystalline material.
Positive Photoresist - a type of photoresist that has a higher developer dissolution rate after being exposed to light..
Post Exposure Bake (PEB) - a bake performed after exposure but prior to develop on chemically amplified photoresists. PEB aids in the exposure induced photo reaction.
Pre-Deposition - a technique where a dopant is deposited onto a wafer prior to a diffusion step. In order to perform pre-deposition, a carrier gas is bubbled through a liquid containing the dopant of interest and the carrier gas carries the dopant vapors into a furnace at high temperature. The dopant diffuses into the wafer and also forms a highly doped glass layer on the wafer surface.
Preventive Maintenance - maintenance preformed to equipment to try to prevent future random failures of the equipment or cleans to improve the quality of the equipment output. Preventive maintenance is performed on a scheduled basis based on elapsed time, number of runs or number of wafers processed.
Probe Card - a card that hold a number of tiny needles with specific spacings designed to make contact with bond pads so that die can be tested in wafer form.
Probe Yield - see Die Yield.
Prober - a piece of equipment that holds a probe card and under control of an automatic tester, steps the probe card across a wafer touching the probe card needles down on each die. Modern probers accept input and output cassettes of wafers and automatically shuttle the wafers onto the prober chuck, probe the wafers, and then shuttle the wafers back out into the output cassette. The prober may also include an inker to dispense ink on the bad die.
Probing - the process of probing/testing die in wafer form.
Process - may be used to refer to a process step or process flow depending on the context.
Process Capability - a comparison of the actual variability of a process to the process specification.
Process Capability Index - the number of standard deviations between the process mean and the closest process specification limit divided by 3, abbreviation Cpk. For example, if there are 6 standard deviations between the mean and the nearest specification limit the process Cpk is 2.0. Generally speaking a Cpk >1.3 is considered capable (4 std deviations) and >2.0 is excellent.
Process Control Charts - a graphical method for determining whether process variability is special cause or common cause.
Process Flow - a set of process steps and order for performing the process steps to produce a desired result.
Process Integration - the act of integrating a set of process steps to create a process flow.
Process Step - an individual activity that changes the characteristics of a section or surface of a wafer.
Projection Aligner - an alignment system in which a mask and wafer are separated by a significant distance and the mask pattern is focused onto the wafer, aligned and exposed. Projection printing was invented in 1973 and by the mid 1970s had largely replaced contact and proximity aligners.
Projection Printer - see Projection Aligner.
PROM - Programmable Read Only Memory - a type of memory that may be programmed once and then the data can never be changed again.
Proximity Aligner - an alignment system in which a mask and wafer are separated by a few microns in distance and the mask pattern is aligned and exposed onto the wafer.
Proximity Printer - see Proximity Aligner.
PVD - see Physical Vapor Deposition.
Pyrophoric - a material that automatically ignites on exposure to oxygen or oxygen containing species.