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]
Manufacturing Process Factors
The semiconductor manufacturing process includes various steps, such as heat treatment, chemical treatment, processing, testing and inspection. These steps involve a great number of factors that affect reliability. Factors that degrade reliability include processing variances (dimensions, property values, etc.) that inevitably occur during product manufacturing, defects and damage that occur in the manufacturing process, handling errors due to human error, and equipment operation errors.
The semiconductor manufacturing process is extremely complicated, requiring great precision. In addition, because product characteristics are extremely sensitive, it is essential to fully understand the factors that affect reliability and take corrective actions to prevent each factor from occurring.
Table 1 shows the factors affecting reliability that are related to the semiconductor manufacturing process.
The manufacturing process repeats several processes to form the elements of the semiconductor product, such as the transistors, resistors and capacitors that are placed on the silicon substrate, and then interconnects these elements to form a single circuit. These processes are adversely affected by dust and therefore take place in cleanrooms. It is critical that the particle originated from equipments and instruments as well as the dust level inside cleanrooms should be controlled at the submicron level. Such contaminates greatly affect reliability.
Of the factors listed in Table 1, those related to the wafer (silicon substrate) are most fundamental to the product. Factors such as crystal defects, resistivity dispersion, surface contamination and surface flaws directly affect product characteristics.
The assembly process begins with dicing. In this process, the die bonding, wire bonding and sealing processes are particularly critical. Die bonding and wire bonding are the processes used to secure the chip and bond the electrodes to the exterior. Since junctions are formed between different materials, changes in temperature and other physical forces (such as vibration, shock and acceleration) result in die cracks or open faults, either of which can be fatal to the product.
In the case of resin encapsulation, impurities in the sealing resin (such as sodium, potassium or chlorine), moisture adsorption, thermal expansion and mold shrinkage are critical. These can result in failures such as corrosion, characteristic failure, bonding wire breakage and die cracks. In the case of hermetic sealing, critical points include the moisture content and other impurities in the sealing gas, and the presence of conductive foreign matter. These can adhere to the chip surface and cause failures such as increased leakage current or faulty operation.
| Process Affecting Reliability | Related Item on Device | Related Factors | Failure Mode | ||
|---|---|---|---|---|---|
| Wafer Process | Wafer (silicon substrate) | Silicon bulk | Resistivity distribution, variation, crystal defect, surface dirt, cracks, flaws, warping, distortion | Characteristic failure, unstable operation, short, open | |
| Oxide film formation | Field oxide film, gate oxide film, interlayer insulator, surface protection film | Pinholes, cracks, uneven thickness, contamination, step coverage faults | Reversed surface, channel leakage, Vth shift, degraded breakdown voltage, hfe shift, noise, unstable operation | ||
| Photo-Engraving Process (PEP) | Resist application | Transistor, diode, resistance, metallization, shape and size, contact | Improper film thickness, poor uniformity, dirt, foreign particles, residual photoresist | Characteristic failure, pinholes, large leakage current | |
| Mask alignment | Transistor, diode, resistance, metallization, shape and size, contact | Misalignment, dirt, foreign particle adhesion, flaws | Characteristic failure, pinholes, large leakage current | ||
| Exposure | Transistor, diode, resistance, metallization, shape and size, contact | Insufficient/Excessive exposure | Characteristic failure | ||
| Development | Transistor, diode, resistance, metallization, shape and size, contact | Insufficient/Excessive development | Characteristic failure | ||
| Etching | Transistor, diode, resistance, metallization, shape and size, contact | Insufficient/Excessive etching, etching temperature faulty, insufficient washing | Characteristic failure, characteristic fluctuation | ||
| Diffusion (thermal diffusion) | Transistor, diode, diffusion resistance, isolation, contact | Abnormal diffusion (transverse, depth), impurity separation, crystal defects, improper impurity concentration | Characteristic failure, degraded breakdown voltage, open, short, unstable operation | ||
| Diffusion (ion implantation) | Transistor, diffusion resistance, contact | Oxide film, silicon bulk damage, insufficient dosage, insufficient implantation depth | Characteristic failure, degraded breakdown voltage, open, short, unstable operation | ||
| Electrode formation (aluminum) | Transistor electrode, internal wiring, contact, MOS gate electrode | Flaws, voids, step coverage, delamination, faulty thickness, meltdown, spike, contamination, electromigration | Open, short, increased wiring resistance, wire corrosion breakage | ||
| Electrode forming(polysilicon) | MOS gate electrode, resistance, internal wiring, contact | Flaws, step coverage, delamination, faulty thickness, meltdown | Open, short, increased wiring resistance | ||
| Assembly Process | Dicing | Chip periphery | Flaws, cracks, contamination | Characteristic failure, increased leakage current, degraded breakdown voltage, wire corrosion breakage | |
| Die bonding | Chip adhesive | Insufficient chip adhesion, adhesive debris, degasification (resin bonding material) | Characteristic failure, unstable operation, increased leakage current, short, improper spacing | ||
| Wire bonding | Bonding wire connection area | Insufficient/Excessive bonding pressure, improper bonding ground, improper bonding loop shape, wire flaws, contamination, wire adhesion | Open, short (package, substrate), broken wire, peeled bonding | ||
| Sealing (resin molding) | Package | Improper forming (bond, cracks), bonding wire displacement, improper lead frame sealing, molding shrinkage distortion, moisture absorption | Bonding wire open/short, wire corrosion breakage (chip, metal wiring), die cracks, characteristic failure | ||
| External lead forming | Lead terminal | Improper shape, damage, improper terminal strength | Open, improper contact | ||
| External lead surface finishing | Lead terminal | Oxidation, rusting, residual surface treatment solution (insufficient washing) | Open, improper contact, leakage between terminals | ||
| Marking | Product mark | Wrong mark, improper mark | Breakage due to misuse | ||
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.