2. Introduction
Purpose
To explain the characteristics and features of the RTAN Series Precision Tantalum Nitride Thin Film Resistors
Objectives
To provide an overview of the materials, design, and processing of the RTAN series and highlight the performance benefits of the product
Content
14 pages
Welcome to Stackpole’s RTAN product training module. This training module will highlight the materials, design, and processing features of the RTAN series product. It will help the viewer understand the performance advantages of tantalum nitride resistor technology over other resistor technologies.

3. Overview Construction and Design Resistive Layer Forming Features
High Density Substrate
Tantalum Nitride Film
Gold inner terminations
Tantalum Pentoxide passivation
Comparison data
Operational life
Biased humidity
Comparison characteristics
Conclusion
Both TaN and NiCr thin film resistors are manufactured using a deposition method called sputtering. But there are unique design and material choices which differentiate products from various manufacturers. Understanding these unique aspects and their effect on the performance of the resistor will demonstrate the outstanding capability of the RTAN series chip resistors from Stackpole.

4. Construction Design
Most thin film chip resistors utilize standard alumina substrates and don’t employ any sort of moisture passivation layer. They also have terminations composed of a high percentage of silver. Stackpole’s RTAN uses a high density substrate, a tantalum pentoxide moisture barrier, gold inner terminations, and adds an auxiliary electrode for superior connection integrity.

5. RTAN Substrate Material
The high density ceramic improves thermal conduction and material strength. High density alumina also eliminates pinholes which provide a valley for moisture to collect, increasing the potential for corrosion. The end result is improved load life performance compared to standard nichrome thin film chip resistors.

6. Film Properties
Nichrome resistive film will dissolve and evaporate in the presence of water. This leads initially to increasing resistance values and eventually open circuit failure. The RTAN series is protected by the tantalum pentoxide barrier layer and will not dissolve or evaporate under continued exposure to high levels of moisture.

7. RTAN Electrode Material
The gold inner terminations of the RTAN series are superior to the silver based terminations for standard thin film chips. Gold is the most chemically stable of the common metals which provides better overall stability for the resistor both electrically and mechanically. Gold is also impervious to sulfur contamination meaning the RTAN also has outstanding anti-sulfur performance.

8. Passivation Protection
A key factor in the performance of tantalum nitride thin film chips is the forming of the moisture protective layer. The protective layer must be distinct to properly protect the resistor element. The RTAN utilizes a relatively thick tantalum pentoxide layer with no interface between it and the tantalum nitride element film. This helps to improve the biased humidity performance.

9. Resistive Layer Forming And Design
Stackpole’s resistive layer of a tantalum nitride chip resistor is formed using photolithography and a mask. It is important to properly size and align the resistive element with the terminations for the best long term reliability and consistent electrical and environmental performance.

10. High Temperature Operation Comparison of TaN & NiCr
High temperature operational life testing of the RTAN compared to standard nichrome demonstrates the superior electrical and environmental stability of the series. For comparison, general purpose thick film chips would experience resistance shifts of typically 2% or more shift under the same conditions.

11. Biased Humidity Comparison of TaN & NiCr
Biased humidity performance of the RTAN series also shows significant improvement over standard and passivated nichrome thin film chips. While resistance shifts of up to 0.2% are very good for thin film resistors under this type of test, that level of instability may not be acceptable for precision applications where absolute tolerances of 0.1% or better are required.

12. Tantalum Nitride Product Comparison
Stackpole’s RTAN compares favorably in terms of electrical performance versus other products currently available. In addition to being AEC-Q200 qualified, the RTAN meets the industry’s most stringent anti-sulfur test standards.

13. Future Trends Expansion of sizes – 0201, 1210, 2010, 2512
Value range expansion – higher and lower resistance values for the 0402 and 0603 sizes
TCR range expansion – 15 ppm and 10 ppm TCR available soon
Apply the technology to a MELF package
Stackpole plans to expand the RTAN series in response to market demand. Along with investigating smaller and larger case sizes, lower resistance values are being developed, particularly in the smaller case sizes. 10 ppm and 15 ppm TCR options are under internal qualification and will be available in the near future.

14. Summary The RTAN Precision Thin Film Chip Series Utilizes:
High density alumina substrate for better thermal conductivity and material strength
Thicker, distinct tantalum pentoxide layer for superior moisture protection
Gold inner terminations for improved anti-sulfur performance
Mask design and alignment to ensure consistent electrical and environmental performance and long term reliability
Stackpole’s TaN offering provides customers with high reliability precision performance at an extremely competitive price
In conclusion, while there is an abundance of thin film chip resistors currently available on the market, few are able to provide the performance benefits of the RTAN series from Stackpole. The combination of anti-moisture and anti-sulfur capability with the outstanding stability over the life of the product make the RTAN series stand out from all other products.