UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001

October 31, 2002

NRC INFORMATION NOTICE 2002-32: ELECTROMIGRATION ON SEMICONDUCTOR 

INTEGRATED CIRCUITS

Addressees

All holders of operating licenses for nuclear power reactors except those who have ceased

operations and have certified that fuel has been permanently removed from the reactor vessel.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform

addressees of a failure mechanism identified in semiconductor components at the KashiwazakiKariwa Nuclear Power Station Unit 5 of the Tokyo Electric Power Company, Inc. (TEPCO). The

failure mechanism has been attributed to electromigration. It is expected that recipients will

review the information for applicability to their facilities and consider actions, as appropriate. 

Suggestions contained in this information notice are not NRC requirements; therefore, no

specific action or written response is required. 

Description of Circumstances

In July and September of 2001, control rods at the Kashiwazaki-Kariwa Nuclear Power Station

were temporarily rendered inoperable due to defective control rod transponder cards. The

Nuclear and Industrial Safety Agency (NISA) of Japan identified the failure mechanism as

integrated circuit (IC) wire breakage and attributed it to electromigration in aluminum (Al) wires

with small crystal grains. The root cause has been determined to be inadequate quality control

methods in the IC manufacturing process. All of the ICs that failed were traced to the HITACHI

Takasaki Works and were manufactured in September of 1986. Further investigation revealed

that between 1985 and 1990, ICs in which Al vapor was deposited by electron beam had small

Al crystal grains.

TEPCO implemented an action plan to evaluate other systems and replace transponder cards

where a single defect in an IC could affect plant safety functions or plant control. Other

businesses operating nuclear reactors where the same phenomenon has occurred have been

advised to develop appropriate management and maintenance plans and to report defects. 

ML023080088
IN 2002-32

Page 2 of 2

Discussion

Electromigration—the drift of metal atoms—is an age-related phenomenon that has been

confirmed to occur in Al wires and traces. It appears to correlate with high current densities in

traces or wires with small cross-sectional areas. The movement of the atoms creates voids that

may eventually present themselves as electrical interconnect failures. Recent research has

shown that this failure mode is strongly affected by the grain structure size of the Al trace or

wire, and can be delayed or overcome by metallurgical modifications to the microstructure. 

Other methods for reducing the effects of electromigration include limiting the current density

and minimizing flaws during the deposition process.

While electromigration has the potential to adversely affect all ICs that have Al wires with small

cross-sectional areas and operate at high current densities, the interconnect failure mechanism

would not be expected to occur simultaneously in redundant safety-related components. It is

also expected that failures in safety-related circuits due to manufacturing defects or operational

conditions would likely be detected by routine surveillance, testing, or diagnostics and that the

followup root cause analyses and corrective actions would address the generic aspects of the

failure. 

It is expected that 10 CFR Part 21, “Reporting of Defects and Noncompliance,” would be the

method used by licensees to notify the NRC of component failures. Therefore, IC failures due

to electromigration would be reportable under 10 CFR Part 21 for safety-related instrumentation

and control components. 

This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact the technical contact listed below

or the appropriate Office of Nuclear Reactor Regulation project manager.

/RA/

William D. Beckner, Program Director

Operating Reactor Improvements Program

Division of Regulatory Improvement Programs

Office of Nuclear Reactor Regulation

Technical contact: C. Graham, NRR

 (301) 415-3201

 E-mail: cxg2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices