Semiconductor Materials Briefs

Want to learn more about semiconductor materials? The Semiconductor Materials Briefs discuss materials that are used to manufacture semiconductors. Materials range from the substrate (in most cases silicon), patterning, to materials used to protect and connect chips to the outside world (packaging). The briefs include category descriptions, technology trends, and historical market data.

  

SEMI Materials Brief: Silicon-on-Insulator (SOI) Wafers (PDF)
Silicon-on-insulator (SOI) wafers were first developed for military applications in the 1960s. During the past 45 years, SOI technology has evolved and is being be adopted in the production of very sophisticated semiconductor devices.

SEMI Materials Brief: Sputtering Targets (PDF)
Sputtering is a type of physical vapor deposition (PVD) that is used to deposit thin films onto various surfaces (e.g. semiconductor wafers) by physical means, as compared to chemical vapor deposition (CVD). In PVD, the target source is bombarded with argon ions, which knock off atoms from the target that coat a receiving wafer creating a uniform metal film on the wafer.

SEMI Materials Brief: Semiconductor Process Chemicals (PDF)
The International Technology Road Map for Semiconductors (ITRS) outlines increasingly higher chemical purity levels required by the semiconductor industry. Currently, there are several grades of chemicals available, and the migration to the highest purity levels has been relatively slow. This can be attributed to the substantially higher costs associated with producing these chemicals and their associated higher prices.

SEMI Materials Brief: Organic Substrates (PDF)
In the past decade, high volume IC packaging has shifted from the era of ceramic packages to organic substrate-based packages, especially the plastic ball grid array (PBGA). The shift from ceramic to laminate substrates for packaging central processing unit (CPU) microprocessors facilitated this migration to organic substrates by providing a volume application that enabled the technology to mature faster. Flex circuit or tape substrates are a niche market for large die packaging, but are also used in volume for chip scale packages (CSPs) including some stacked die packages. Increasingly many of the new CSP designs are using a rigid laminate substrate rather than flex circuit.

SEMI Materials Brief: Leadframes (PDF)
A leadframe consists of a die mounting paddle and lead fingers. The die paddle serves primarily to mechanically support the die during package manufacture. The lead fingers connect the die to the circuitry external to the package.

SEMI Materials Brief: Die Attach Materials (PDF)
Die attach materials provide the mechanical and thermal connection between the semiconductor device and the package. These materials are used in paste, tape or solder form. This market brief covers paste and tape materials only.

SEMI Materials Brief: Encapsulant Materials (PDF)
Encapsulant materials are polymeric-based materials used to provide mechanical and environmental protection of a semiconductor device. Mold compounds, underfill, and liquid encapsulants fall into this category. At the most basic level, these materials are formulated using a combination of raw materials: organic resins, fillers, catalysts, and a pigment or coloration. Additives include flame retardants, adhesion promoters, mold release materials, ion traps, and stress relievers.

SEMI Materials Brief: Bonding Wire (PDF)
Wire bonding is used throughout the microelectronics industry as a means of interconnecting chips, substrates, and output pins. Wire forms the connections between the bond pad on the IC and the bonding fingers of the leadframe, plastic laminate, or ceramic substrate. The bonding method utilized is a function of the wire material and the substrate.

SEMI Materials Brief: Semiconductor Photoresists (PDF)
Improvements in semiconductor performance continue to be made, largely driven by advances in optical lithography equipment, photomask, and photoresist (resist) materials. In particular, the design and development of photoresists that are sensitive to short exposure wavelengths have enabled the industry to migrate to smaller device sizes. Photoresist allows precise pattern formation upon exposure to light through a template called a photomask and subsequent etching of portions of the photoresist, resulting in the permanent transfer of patterns to the wafer substrate.

SEMI Materials Brief: Prime Polished Silicon Wafers (PDF)
A wafer is a thin slice of semiconducting material upon which microcircuits are constructed by doping (via diffusion or ion implantation), chemical etching, and deposition of various materials.

SEMI Materials Brief: Semiconductor Photoresist Removers (PDF)
Removal Materials are wet chemical solutions used to remove the photoresist left on the wafer after processing as well as for cleaning wafers immediately after etch processes on aluminum (Al), tungsten (W), titanium (Ti), titanium nitride (TiN), dielectric oxides, and polysilicon surfaces. Resist removal for greater than 0.50 micron geometries is referred to as a wet-wet process, since these chemical solutions are used to remove both the photoresist mask and photoresist residues.

SEMI Materials Brief: Polycrystalline Silicon (PDF)
Polycrystalline silicon, also called poly or polysilicon, is one of the purest materials ever manufactured by mankind. Nonetheless, much work is still being done to reduce metal contamination levels and improve uniformity. It is used as the charge material in the silicon ingot growth process and therefore dictates the purity of wafers.

Materials Brief: Semiconductor Photomasks (PDF)
A photomask, also called a reticle, is a transparent glass or quartz plate with an array of patterns or images. These materials permit the passage of light in intricate and precise patterns. The patterns or images emerge by creating transparent and opaque regions on the plate through the photolithography process in semiconductor manufacturing. Each pattern consists of opaque and transparent areas that precisely control the passage of light to cast the image of the size and shape of the device elements in a semiconductor circuit.

SEMI Materials Brief: Epitaxial or Epi Silicon Wafers (PDF)
There are two types of epitaxial or epi silicon wafers used in the semiconductor industry: discrete and MOS.

SEMI Materials Brief: Chemical Mechanical Planarization Materials (PDF)
The manufacture of a semiconductor device is essentially achieved by building alternating layers of metal and insulator materials on a silicon substrate. Prior to the 1990s Chemical Mechanical Planarization (CMP) was looked on as too "dirty" to be included in high-precision fabrication processes, since abrasion tends to create particles and the abrasives themselves are not without impurities. However, given the small size and complexity of today’s advanced semiconductor devices, it is essential that these layers be extremely flat for lithographic processing. In order to achieve the required flatness, CMP is utilized.

SEMI Materials Brief: Semiconductor Photoresists Developers (PDF)
Aqueous or water-based developers are used in the lithography process to pattern photoresist films immediately after the exposure process. For positive photoresists, the developer removes film in the exposed wafer regions to produce device patterns. For negative photoresists, the developer removes film in the unexposed wafer regions to produce device patterns.

SEMI Materials Brief: Semiconductor Anti-Reflective Coatings (PDF)
Extending performance of lithography and photoresists to meet shrinking device requirements is challenged by film properties on levels such as polysilicon, aluminum, and copper. Patterning devices during lithography exposure is difficult due to the highly reflective nature of these films, varying photoresist thickness, and device topography. In order to minimize these effects, materials called anti-reflective coatings (ARC) are applied to wafers either immediately before or after photoresist coating.