On July 1st, Toshiba Corporation's Semiconductor Company and Storage Products Company consolidated to form Semiconductor & Storage Products Company.This page describes reliability information of semiconductor products.
Factors Affecting Reliability
[As of April, 2011]
Design Factors
Product reliability is basically determined in the product design phase.
Table 1 lists the semiconductor design factors that should be taken into consideration during semiconductor design. The three major design categories are pattern, manufacturing process and package.
With integrated circuit design, for example, the dimensions of the transistor (bipolar or MOS) and other factors that affect performance are determined during the pattern design phase from the functional characteristics required of the device. Transistors are then combined and connected to obtain certain functions. At this time, continuous efforts are made, in order to minimize the lengths of the wiring between transistors and the chip size , to decrease to the extent possible the individual transistor size, resistance, wiring width and wiring interval dimensions.
At present, this process is automated by computers and design is performed according to predefined design rules. Related factors listed in Table 1 and so on are incorporated into design rules and checked by computer.
In the manufacturing process design phase, the manufacturing process is designed to realize high efficiency and the expected characteristics based on the designed pattern. The manufacturing process is broadly divided into two processes: (1) the wafer process, which puts the transistors, diodes and resistors on the silicon substrate in accordance with the design pattern, and (2) the assembly process, which consists of dicing of the pattern developed on the wafer, die bonding, wire bonding and sealing to form the final product structure.
During the wafer process, various manufacturing techniques are used to accurately reproduce the size and shape of the diffusion layer, oxide film and metal wiring formed on the wafer. Continuous efforts are made to maintain consistency in these characteristics. In addition, processing precision is incorporated into the design rules and fed back to pattern design.
In the package design phase, packages are designed to mechanically and thermally protect components on the diced silicon substrate from the stress of use, making the product into a form that is easy to use. There are two major types of packages: hermetically sealed, with an internal cavity structure, and resin-encapsulated, in which the device is buried in the resin. Materials such as glass, ceramic, metal and resin are used in package construction.
| Factor Affecting Reliability | Related Factors | Failure Mode | ||
|---|---|---|---|---|
| Pattern Design |
Transistor (bipolar) | Size and shape (collector, base, emitter), impurity concentration, diffusion depth | Characteristic failure | |
| Transistor (MOS) | Size and shape (W/L), gate film thickness | Characteristic failure | ||
| Isolation | Width, diffusion depth, impurity concentration | Parasitic transistor, leakage, improper breakdown voltage | ||
| Resistance (diffusion) |
Size and shape, diffusion depth, impurity concentration | Characteristic failure, improper breakdown voltage, short | ||
| Resistance (polysilicon) | Size and shape, impurity concentration, film thickness | Characteristic failure, open | ||
| Metallization (aluminum) | Size and shape, film thickness | Electromigration, open, short | ||
| Metallization (polysilicon) | Size and shape, film thickness, impurity concentration | Characteristic failure, open | ||
| Metallization contact | Size and shape, contact combination (Al-silicon, Al-polysilicon, etc.) | Open, short (spike) | ||
| Bonding pad | Size and dimension, wiring lead shape | Improper bonding, open | ||
| Bonding pad layout | Bonding pad spacing, package, relative bonding positions | Bonding wire open/short, bonding wire displacement (resin mold) | ||
| I/O protection circuit |
Protective resistance, protective diode/transistor | Electrostatic breakdown, surge damage | ||
| Manufacturing Process Design |
Photoengraving process (PEP) |
Photoresist application |
Film thickness, dust, foreign particle adherence, photoresist material | Improper PEP pattern (open/short characteristic failure), pinhole |
| Mask alignment |
Alignment accuracy | Characteristic failure | ||
| Exposure | Time, intensity of illumination | Improper PEP pattern (open/short characteristic failure) | ||
| Development | Time, developing solution | Improper PEP pattern (open/short characteristic failure) | ||
| Etching | Time, temperature, etching solution | Improper PEP pattern (open/short characteristic failure) | ||
| Oxide film formation (thermal oxidation method) |
Temperature, time, reaction gas, film thickness | Characteristic failure (Vth, hFE, etc.), TDDB | ||
| Oxide film formation (CVD method) |
Temperature, time, reaction gas, film thickness | Characteristic failure (Vth, hFE, leakage, etc.) | ||
| Diffusion (thermal diffusion) |
Temperature, time, impurity concentration, diffusion depth | Characteristic failure, improper breakdown voltage | ||
| Diffusion (ion implantation) |
Acceleration voltage, dosage, ion source implantation depth | Characteristic failure | ||
| Electrode formation (aluminum) |
Deposition method, temperature, film thickness | Characteristic failure, open, short | ||
| Electrode formation (polysilicon) | Temperature, time, reaction gas, film thickness | Characteristic failure, open, short | ||
| Dicing | Dicing method, wafer thickness | Die crack, flaw, open, short | ||
| Die bonding | Die bonding method, temperature, die bonding material (Au-Si, epoxy, etc.) | Characteristic failure (unstable operation) | ||
| Wire bonding | Wire bonding method (thermal compression, ultrasonic bonding, etc.), wire material (Au, Al), wire diameter | Open, short | ||
| Encapsulation (resin molding) |
Molding method, temperature, time, material characteristics (thermal expansion coefficient, impurities) | Characteristic failure, die crack, void, open, short, wire corrosion breakage | ||
| External lead forming | Lead forming method, size and shape | Broken package, lead shape abnormality, lead damage | ||
| External lead finishing | Treatment method (plating/dipping), protective material (gold, tin, solder, etc.) | Rusting, insufficient contact, improper soldering | ||
| Marking | Temperature, time, marking method | Marking erosion | ||
| Sealing method | Glass, metal welding, metal fusion, resin bonding, sealing condition | Hermetic fault, characteristic failure, large electrical leakage current, wire corrosion breakage | ||
| Package Design (Hermetically -Sealed) |
Sealing gas | Chemical reaction, moisture content | Characteristic failure, large electrical leakage, wire corrosion breakage | |
| Package material | Glass, ceramics, metal, resin, thermal expansion, mechanical strength | Package damage, hermetic fault, characteristic failure, thermal runaway | ||
| Package shape and size | Chip size correlation, seal width tolerance | Hermetic fault, characteristic failure | ||
| Lead material | Electrical conductivity, hardness, thermal expansion, corrosion resistance, mechanical strength | Insufficient contact, lead damage | ||
| Plating material | Plating composition, temperature, electrical current | Poor solderability, whiskers | ||
| Package Design (Resin Molding) |
External lead shape and size | Lead cross-sectional shape, tensile strength, bending strength | Lead damage | |
| Molding method | Transfer mold, bonding, etc. | Open, short (bonding wire) | ||
| Molding resin material | Base resin, hardening agent, chemical resistance, impurities, thermal expansion, thermal conductivity | Characteristic failure, open, short (bonding wire), wire corrosion breakage | ||
| Package shape and size | Chip size correlation, seal size, tolerance | Missing lead, open, short, wire corrosion breakage | ||
| Molding conditions | Temperature, time, pressure | Open, short (bonding wire), bonding wire displacement | ||
| Lead material | Electrical conductivity, hardness, thermal expansion, corrosion resistance, mechanical strength | Insufficient contact, lead damage | ||
| Plating material | Plating composition, temperature, electrical current | Poor solderability, whiskers | ||
On July 1st, Toshiba Corporation's Semiconductor Company and Storage Products Company consolidated to form Semiconductor & Storage Products Company.This page describes reliability information of semiconductor products.