Quality Assurance of IC Memories

1. Views on Quality and Reliability

Hitachi products should always meet individual users’ purposes and required quality levels, maintaining satisfactory

performance for general applications. Hitachi works continuously to assure high reliability standards for our IC

memories in actual usage. To meet user needs and to cover expanding applications, Hitachi has defined these goals:

1. Establish reliability by design during new product development.

2. Establish quality at all steps in the manufacturing process.

3. Strengthen the inspection process at all points.

The establishment of reliability targets is important in manufacturing and marketing, as well as in determining

function and price. Practically, the reliability targets cannot be determined from failure rates produced by any single

common test condition; they are based on many factors such as equipment characteristics, target system purposes,

derating applied during design, operating conditions, and maintenance requirements.

2.2 Reliability Design Factors

Timely analysis and execution are essential to achieve performance based on reliability targets. The primary design

items of interest are design standardization, device process and structural design, design review, and reliability

1. Design standardization

Design standardization requires the establishment of design rules and the specification of parts, materials, and

and layout design. Especially in the case of applying new processes or new materials, at Hitachi we study the

technology in depth prior to any detailed device development.

Quality Assurance of IC Memorie

3. Reliability testing by test site

The test site is also called the test pattern. It is a useful method for evaluating the reliability of complex ICs and

complicated functions.

a. The purposes for the test site are:

 To make clear definitions about mental failure modes

 To analyze relationships between failure modes and manufacturing processes and/or conditions

 Simplification of testing

2.3 Design Review

Design review is a method to systematically confirm whether or not a design satisfies the performance required by

users, whether it meets all specifications, and whether the technical items accumulated in test data and application

data are effectively utilized.

In addition, from the standpoint of comparisons to competitive products, a major focus of the design review is to

insure the quality and reliability of the product. At Hitachi, the design review is perform-ed as a part of new product

development, and when changing existing products.

The following items are considered in design review.

1. Describing the product based on specified design documents.

specialists. Generating tests, experiments, and calculations as needed to confirm the results of each design

7. Refering to past performance and failure experiences with similar devices. Confirming the prevention of any

repetition of such experience, and planning and executing a test program to prove this level of performance.

At Hitachi, design reviews including these steps of analysis and decision are made using individual check lists

according to each objective.

Quality Assurance of IC Memorie

3. Quality Assurance System of Semiconductor Devices

3.1 Activity of Quality Assurance

At Hitachi, these are the general purposes of quality assurance:

1. Problems are resolved within each step, so that by the final stage of production even very small potential failure

These are the purposes of qualification at Hitachi.

1. Qualify the product objectively from a customer standpoint (as by a third party).

2. Consider the failure experiences and data provided by customers.

3. Qualify every change in design and process.

4. Qualify, with special emphasis, all final choices of parts, materials, and processes.

5. Establish control points within the production procedure by considering the process ability and factors of

manufacturing variance.

Figure 1 shows the general outline of design qualification at Hitachi.

Quality Assurance of IC Memorie

Quality Assurance of IC Memorie

3.3 Quality and Reliability Control in Mass Production

Material, Parts

Inspection of

Material and Parts

100% Inspection

Quality Assurance of IC Memorie

3.3.1 Quality Control on Parts and Materials

Besides the qualification of parts and materials as stated in Section 3.2, the quality control of parts and materials

1. Technology meetings with vendors.

Quality Assurance of IC Memorie

The typical check points of parts and materials are shown in Table 1.

Quality Assurance of IC Memorie

3.3.2 Process Quality Control

following process. Especially for devices designed for high reliability, manufacturing lines are rigidly monitored

quality assurance procedures. Controlling quality during processing includes these items:

a. Control of conditions of equipment and workers

b. Sampling test of uncompleted products

c. Proposal and implementation of improvements in working conditions

d. Continuous worker education

e. Maintenance and improvement of yields

f. Identification of quality problems, and implementation of countermeasures to them

g. Communication of quality-related information

2. Quality control of manufacturing facilities and measuring equipment

Manufacturing facilities have been developed to answer the need for higher device performance and automated

production. It is also important to define and accurately measure quality and reliability.

3. Quality control of the manufacturing environment and submaterial

Final quality and reliability of devices are especially affected by manufacturing processes. We therefore

thoroughly control factors of the manufacturing environment, such as gases or pure water.

Dust control is critical to achieve higher integration and higher device reliability. To maintain and improve the

cleanliness of the manufacturing site, we take great care to keep buildings, facilities, air-conditioning systems,

materials, clothes, and all possible elements associated with production as clean and dust-free as we can. We

extend this effort to periodically check the ambient air in the manufacturing facility for floating dust, and we

check for any minute amounts which might have accumulated on the floor, other surfaces, or on any equipment.

Quality Assurance of IC Memorie