The quality, price, delivery and service of a product are all important elements but the most important thing as long as the product exists is the quality of the product and the continuing service to the user of the product.
In the semiconductor industry, the quality levels required by products are very high. On the other hand, high quality control is required in the mass-production systems with very advanced technology such as the process control capability seen in the “wafer process” or the minute work seen in the “assembly process”.
A brief description of the quality-guaranteeing activities is given below.
3.1 Mass production procedures
From trial production in development through trial mass production until mass production, a series of type approval tests are carried out for performance and reliability, along with an examination of a typical design illustration. Fig.3.1 shows a quality-guarantee system illustration from development through mass production.
The next chapter provides information on the reliability tests and reliability confirmation in the type-approval tests.
3.2 Environmental control
In the semiconductor industry, the environment greatly effects product quality and control limits are established to control the environment precisely and monitor dust, moisture and temperature. The same measures are taken with the gas and water used in the factory.
3.3 Periodic inspection of manufacturing equipment, instrumentation and maintenance control
The semiconductor industry is a manufacturing industry and control of the manufacturing equipment and Instrumentation is important in device production. Regular checks and maintenance are performed to prevent any decline in accuracy, faults, etc., in the device.
3.4 Material purchasing control
Strict analysis and inspection are performed using spectrum analysis etc. based on receipt inspection norms. After sufficient sample examination has been performed to confirm the quality of the supplied materials and all problems solved, formal delivery begins. Due consideration is also given to the quality control of the supplier’s manufacturing process.
3.5 Manufacturing process control
The conditions that greatly influence quality control, such as purity of demineralized water atmosphere, furnace temperature, gas flow rate, etc., are measured by instruments mounted on the respective parts, automatically recorded and checked by engineers using check sheets. Moreover, processes that can have a larger effect on characteristics, such as depth of diffusion, surface concentration, etc. are recorded and used in the control data for working conditions. In addition, to assure stable quality, control is performed with data acquisition regarding the assembly processes which affect the wire-bond process’ adhesion pressure, strength control, etc.
3.6 Intermediate and final inspections
Our policy on intermediate and final inspections is thus: With the aim of measuring the reduction in variation and
improving the maintenance of quality, and thus producing better products, data on the product’s quality characteristics,
such as appearance, size, structure, and electrical characteristics, etc., are returned to the first manufacturing stage.
Intermediate inspections include wafer test and assembly process sampling inspections. All are carried out by two independent checks: one by the works section, based on the motto of “making quality from the manufacturing process”, and one by the quality-control section. By correcting quality according to the independent checks, we are able to check on points that are hard to discover in the finished product. After product completion the final inspection is conducted as a finished-goods inspection. Finally, electrical properties and external appearance are inspected.
From the viewpoint of the customer who will use the product, to confirm the total performance and quality of the product, before the product is stored it is again sampled and subjected to quality guaranteeing inspections for external appearance, electrical characteristics and reliability. The quality of the warehouse is also strictly checked for each lot.
3.7 Quality information
Various data on quality, such as inspection results and customer information, is created mainly in the quality guaranteeing section, and is rapidly sent to the related section including a manufacturing department for the continued improvement of quality.