Survey of critical failure events in on-chip interconnect by fault tree analysis

To enhance the humidity reliability of copper (Cu) metallization used in memory LSIs, nitrogen (N)-doped amorphous-carbon (a-C:N) deposited by sputtering on the Cu surface is proposed. Since the preparation of a-C:N film can be achieved at room temperature, the process temperature is compatible with LSIs fabrication. After the high-temperature/humidity storage test, the a-C:N layer was found to be an excellent barrier to protect the Cu surface from oxidation and avoid the increase of Cu sheet resistance. Depth profiles imply no oxidation occurs on the underlying Cu surface. An appropriate concentration of N-doping is considered to prevent the penetration of moisture with the effects of the repulsive force between both N and O atoms. The proposed method is promising as a practical method to improve the reliability of Cu metallization for long-term storage.

Section: Experimental Methodsmentioning

confidence: 99%

“…1,2) Therefore, the reliability of Cu metallization became a serious concern to maintain the conductive property. [3][4][5][6][7] For instance, surface of Cu bond pad, which is such a critical part, must have additional materials to prevent an inherent issue of Cu oxidation during operating in ambient moisture.…”

Section: Introductionmentioning

confidence: 99%

Efficient moisture barrier of nitrogen-doped amorphous-carbon layer by room temperature fabrication for copper metallization

Gomasang

Ueno

2020

“…Cu bonding pads have been considered the critical parts for Cu-oxide formation because they were primarily exposed to air during the wire bonding process and moisture may probably diffuse through the package to oxidize the Cu pads during operation, leading to the failures of the electrical connection or resistance increase. [17][18][19] Applying an appropriate barrier coated on the Cu surface is a potential method to avoid Cu oxidation. However, wire-bondability on the coated Cu should be confirmed for the application.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen-doped amorphous carbon coating on copper pads for direct wire bonding with a long-term humidity reliability

Gomasang

Nakajima

Ueno

2021

To improve the long-term reliability of copper (Cu) pads used in LSIs, nitrogen-doped amorphous carbon (a-C:N) coating is applied to the Cu pads with direct wire-bonding to prevent Cu oxidation in humidity. To obtain a thin barrier, the thickness optimization of a-C:N layer was carried out under temperature humidity storage (THS) testing at the conditions of 85 °C/85% relative humidity. Cu pad chains coated with the optimized a-C:N film were fabricated by direct bonding with aluminum (Al) wires. The electrical connection up to 210 bonds was obtained with the 10 and 15 nm thick a-C:N coated Cu pads. The reliability test of the pad-chains under the THS was carried out, and a 15 nm thick a-C:N can preserve the electrical connection along 100 h of the THS test. The a-C:N coating is expected to improve the humidity reliability of Cu pads with direct wire-bonding for long-term data storage.

“…6,7) In the long-term storage, reliability against moisture is considered as one of the critical issues for metallization. 8) To test the reliability against moisture, temperature humidity storage (THS) tests have been adopted, and the lifetime has been predicted by the Peck's model. [9][10][11][12][13] The lifetime prediction models are mostly based on the test results for Al-based metallization, however, the prediction model for Cu-based metallization is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Lifetime prediction model of Cu-based metallization against moisture under temperature and humidity accelerations

Gomasang¹,

Ogiue²,

Yokogawa³

et al. 2019

To establish the lifetime prediction model for Cu-based metallization against moisture, temperature humidity storage test under the various accelerated conditions is performed. The increase of Cu sheet resistance induced by Cu-oxidation is measured by a four-point probe method. X-ray photoelectron spectroscopy analysis is carried out to investigate the variation of oxidized Cu. The activation energy and the humidity acceleration factor for Cu-based metallization have been derived by the statistical analysis to predict the lifetime against moisture for the first time. The results indicate that Cu-based metallization is comparatively more sensitive to the temperature than humidity at around the practical use condition.