Aerial Blank Inspection (ABI): This is the process by which mask blanks for the photolithographic process of producing silicon wafers are inspected. The push towards features sizes that have to be reproduced using EUVL, requires a very low rate of defects on the mask with a correspondingly tight tolerance on the maximum defect sizes permissible. The term aerial arises because the systems resemble the operation of a microscope with the blanks being illuminated with the EUV radiation.
The word is derived from the Greek Actinism meaning radiant force. Its use is in the context of the technological application of radiation, as in the modification of material properties, such as with the photochemical reactions of the photographic process. Actinic Inspection Tools (AIT) are important in the field of silicon wafer patterning-mask production, as mask defects have to be detected, and repaired when possible, before the costly mass production of the wafers is instigated. In this context the term refers to the inspection of the masks at the same wavelength of radiation (at wavelength) as they are to be used in the photolithographic wafer fabrication process.
Aerial Image Measurement System (AIMS): This is an optical technique developed to evaluate the printability of features in a lithographic system. It is required to monitor the quality of the masks used in wafer fabrication, analysing the effect of potential defects, the effectiveness of mask repairs and the properties of mask features that are used to enhance the printing of certain aspects of the pattern information. AIMS negates the need to print the mask pattern using a stepper printer and makes use of sophisticated algorithms to interpret the properties of the mask from the aerial images that are captured.
Aerial Pattern Mask Inspection (APMI): Once a blank mask has been inspected and accepted it has to be patterned with the required details for the particular lithographic stage it is required for. The next generation of masks for the EUV wavelengths will need to make use of reflective structures based upon multi-layer mirror technology for the patterning process, to allow efficient reflection of the radiation on to the substrate for pattern transfer. These multi-layered masks are more complex and more vulnerable to defects, environmental effects and general damage and therefore a high degree of mask integrity has to be insured before they are committed to the high volume production process, which is what the APMI process aims to achieve.
(Discharge Produced Plasma) In DPP, electrical energy is used to ionize a gas (or mixture of gases), heating it to produce a high density plasma. Depending on the gas(es) used, their partial pressures, the amount and frequency of the power input, light in the EUV range (i.e., 13.5 nm) can be produced. This process is highly efficient since electrical energy is directly converted into plasma energy.
(Extreme Ultra Violet lithography) Also known as EUV lithography is a next-generation lithography using the 13.5 nm wavelength. EUV is a significant departure from the deep ultraviolet (DUV) lithography used today. EUV lithography takes place in a vacuum as all matter absorbs EUV radiation. All the optical elements, including the photomask, must make use of defect-free Mo/Si multilayer which reflects light by means of interlayer interference; any one of these mirrors will absorb around 30% of the incident light. EUV source development has focused on plasmas generated by laser (LPP) or discharge (DPP) pulses. The mirror responsible for collecting the light is directly exposed to the plasma and is therefore vulnerable to damage from the high-energy ions and other debris.
(High Volume Manufacturing) This acronym is used often in the semiconductor manufacturing sector to identify a production system or process that performs to set industrial requirements. The requirements of the HVM become a benchmark that determines whether a process can be economical and of quality. For EUVL HVM, the desired throughput is 100 wafers per hour.
(Laser Produced Plasma) Relates to plasma produced by laser irradiation of a substance. Generally created by directing a laser at a target composed of a liquid, a solid, or a partially condensed gas. As the substance absorbs the high energy, energetic disassociation of the substance creates an ionized atmosphere (plasma). Depending on the power, frequency and the substance irradiated, the plasma can produce a wide range of energetic EUV photons. Two disadvantages of an LPP source is that the conversion of electrical energy into plasma is through an intermediate stage (the laser). LPP was the first EUV light source developed for the EUVL project in the United States at the end of the 90s. The conversion efficiency from laser power to EUV emission power is high but the system wide efficiency is poor, when the rather small efficiency of electrical to laser power is taken into consideration.
Microchips are generally the basic components of modern miniaturized electronics. The chip is a series of electrical circuits built into a tiny wafer of silicon or another semiconductor. These circuits may be made by exposing the chip to a high temperature vapor of controlled composition. The vapor deposits a thin layer on the silicon to produce complex layers of materials such as those found in transistors.
In the photolithography process, elements to be created on the IC are reproduced in a pattern of transparent and opaque areas on the surface of a quartz plate called a photomask. The scanner passes light through the photomask, forming an image of the photomask pattern. The image is focused and reduced by a lens, and projected onto the surface of a silicon wafer that is coated with a photosensitive material called a photoresist. After exposure in the scanner, the coated wafer is developed like photographic film.