V - Index of

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• QUALITY ASSURANCE OF IC MEMORY
1. VIEWS ON QUALITY AND
RELIABILITY
Hitachi basic views on quality are to meet individual
users' purpose and their required quality level and
also to maintain the satisfied level for general application.
Hitachi has made efforts to assure the
standardized reliability of our IC memories in actual
usage. To meet users' requests and to cover expanding
application, Hitachi performs the followings;
(1) Establish the reliability in design at the stage of
new product development.
(2) Establish the quality at all steps in manufacturing
process.
(3) Intensify the inspection and the assurance of reliability
of products.
(4) Improve the product quality based on marketing
data.
Furthermore, to get higher quality and reliability,
we cooperate with our research laboratories.
With the views and methods mentioned above,
Hitachi makes the best efforts to meet the users' requirements.
2. RELIABILITY DESIGN OF
SEMICONDUCTOR DEVICES
2.1 Reliability Target
Establishment of reliability target is important in
manufacturing and marketing as well as function
and price. It is not practical to determine the reliability
target based on the failure rate at a single
common test condition. So, the reliability target is
determined based on many factors such as each
characteristics of equipment, reliability target of
system, derating applied in design, operating condition
and maintenance.
2.2 Reliability Design
Timely study and execution are essential to achieve
the reliability based on reliability targets. The main
items are the design standardization, device design
including process and structural design, design
review and reliability test.
(1) Design Standard ization
Design standardization needs establishing design
rules and standardizing parts, material, and
process. When design rules are established on
circuit, cell, and layout design, critical items
about quality and reliability should be examined.
Therefore, in using standardized
process or material, even newly developed products
would have high reliability, with the exception
of special requirement on function.
(2) Device Design
It is important for device design to consider
total balance of process design, structure
design, circuit and layout design. Especially in
case of applying new process or new material,
we deeply study the technology prior to development
of the device.
(3) Reliability Test by Test Site
Test site is sometimes called Test Pattern. It is
useful method for evaluating reliability of
designing and processing ICs with complicated
functions_
1. Purposes of Test Site are as follows;
• Making clear about fundamental failure mode;
• Analysis of relation between failure mode and
manufacturing process condition.
• Analysis of failure mechanism.
• Establishment of QC point in manufacturing.
2. Effects of evaluation by Test Site are as follows;
• Common fundamental failure mode and
failure mechanism in devices can be evaluated.
• Factors dominating failure mode can be
picked up, and compared with the process
having been experienced in field.
• Able to analyze relation between failure
causes and manufacturing factors.
• Easy to ru n tests.
2.3 Design Review
Design review is a method to confirm systematically
whether or not design satisfies the performance
required including by users, follows the specified
ways, and whether or not the technical items
accumulated in test data and application data are
effectively applied.
In addition, from the standpoint of competition
with other products, the major purpose of design
review is to insure quality and reliability of the
product. In Hitachi, design review is performed
in designing new products and also in changing
products.
The followings are the items to consider at design
review.
(1) Describe the products based on specified design
documents.
(2) Considering the documents from the standpoint
of each participant, plan and execute the subprogram
such as calculation, experiments and
investigation if unclear matter is found.
(3) Determine the contents and methods of reliability
test based on design document and drawing.
~HITACHI
HItachI America Ltd. • 2210 O'Toole Avenue • San Jose, CA 95131 • (408) 435-8300 19