Korvus Technology

Thin Film Resistors: A Deep Dive

A myriad of components drive the electronics industry, including a well-known, integral part called the thin film resistor. A thin film resistor can be manufactured in miniscule sizes and to extremely exacting specifications, making it a ubiquitous part in electronic devices.

In this article, we’ll explain the details behind these components; from their structure, different types of resistors and the thin film deposition process behind them.

pvd coating in process in a thin film deposition system

 Understanding Thin Film Resistors

 The purpose of thin film and chip resistors is to restrict electrical current that can flow through a circuit. “Thin” refers to the fact that the resistive element is deposited as a thin film on a glass or ceramic base.

These components are favored across electronic, instrumentation, medical devices, and automotive applications, where accurate and stable resistance values and voltage control are essential performance elements.

What Is a Thin Film Resistor?

A thin film resistor is a component designed to provide a specific resistance to the flow of electric current in a circuit. It earned its name thanks to the thin film of resistive material that gets deposited onto an insulating substrate, which is what ultimately forms the resistor. This thin film-resistive material is typically made of nichrome or tantalum.

The underlying purpose is to resist or oppose the flow of current that passes through it.

The Construction Process of Thin Film Resistors 

Unlike thick film resistors, which are coated with a resistive paste screen on a ceramic body and resistance values get adjusted with a rudimentary trimming cut where all the current passes through, a thin film resistor undergoes a much more complex manufacturing process utilising a uniform metallic film.

 The manufacturing process includes deposition of a resistive metallic layer, which is extremely stable and serves to calibrate the resistance value. Further, the laser trimming process is more precise and uniform, allowing more evenly distributed current.

A deposition technique that is used in the manufacture of both thin film and thin film chip resistors is called physical vapour deposition (PVD); it is a form of vacuum deposition transporting material to the substrate where it then ultimately condenses to a thin film.

The Evolution of Thin Film Resistors

Resistors have been around since the early days of electronics, though they were very limited in terms of precision and stability. By the 1950s, however, thin film technology had been adopted as an alternative to bulkier wire-round resistors.

As the microelectronics field emerged in the 1970s, thin film deposition techniques began to evolve, and the 1970s saw the advent of higher performance materials.

Some of the most transformative inventions were the use of integrated circuits and photolithography techniques.

Ongoing advancements continue to be the norm thanks to continuing pressures of miniaturisation, materials innovation, and automation.

The Anatomy of a Thin Film Resistor

Various components contribute to the functionality and performance of a thin film resistor.

Components of Resistors

 The following components can be found in a thin film resistor:

 Substrate

  • Thin film resistive layer
  • Conductive terminals
  • Passivation resistive layer
  • Bonding pads

Types of Resistors

There are several types of resistors, not just thin film and thin film chip resistors, including but not limited to the following:

  • Fixed carbon and wire-wound resistors
  • Variable resistors
  • Specialised film and chip resistors
  • Network resistors
  • Variable resistors
  • Surface mount resistors
  • Power resistors

The most notable characteristics of the thin film resistor family are high tolerance levels, a lower temperature coefficient, and capabilities for higher-rated power. Thin films also boast lower parasitic inductance and lower capacitance.

A thin film resistor has a wider array of industry applications compared to thick film resistors. While thin film varieties are 0.1 microns thick, thick film resistors can be thicker by a factor of 1,000. This difference between a thin and thick film resistor affects accuracy and the acceptable temperature range, so a thin film resistor is more commonly used in precision applications.  

The Deposition Process Behind Thin Film Resistor Production

Without question, the deposition process plays an essential role in the production of a thin film resistor because it is determinant of its performance characteristics and reliability.

pvd coating in progress inside a thin film deposition system

 The Deposition Process

The deposition process includes a long list of detailed steps:

  1. Substrate preparation
  2. Cleaning and surface treatment
  3. Application of a masking layer
  4. Deposition of thin film through physical vapor deposition or chemical vapor deposition
  5. Heat treatment
  6. Etching
  7. Application of a passivation layer
  8. Quality control and testing

Semiconductor Materials in Thin Film Resistors

The choice of semiconductor materials is also important, as the selection criteria involves evaluating their specific electrical properties, stability, cost, and overall compatibility with the deposition process.

Options for semiconductor materials in thin films include:

  • Nichrome
  • Tantalum Nitride
  • Silicon
  • Aluminum
  • Platinum
  • Gold 

Manufacturing Thin Film Resistors With Korvus Technology

The HEX Series from Korvus Technology is a unique thin film deposition system for creating thin film resistors. If you are looking to expand your capabilities, we invite you to contact us and explore our custom solutions. We will be happy to discuss your project and help you identify which system is right for you.

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