In the operation of semiconductor devices, temperature constantly influences their performance and lifespan. Even slight temperature changes can enhance a device's efficiency or lead to its rapid degradation. Excessive heat can cause circuit failure, while excessively low temperatures may hinder normal functionality. Many distributors offer a wide range of electronic components to cater to diverse application needs, like BTS50085-1TMA

This article delves into various practical methods for measuring the temperature of semiconductor devices, along with the scientific principles behind them, to help readers better understand the importance of temperature monitoring.

Principles of Temperature Measurement

1.PN Junction-Based Measurement

The forward voltage of a PN junction decreases as temperature increases, following the formula:

where Vf is the forward voltage, V0 is the initial voltage, α is the temperature coefficient (typically 2 mV/°C), and T is the temperature in degrees Celsius.

This characteristic can be used for temperature measurement by monitoring the forward voltage of the PN junction. By applying a known current and measuring the resulting Vf, the temperature can be calculated using the above equation.

2.Thermistor-Based Measurement

The resistance of a thermistor changes with temperature according to the formula:

where R(T) is the resistance, R0 is the resistance at a reference temperature, B is the material's thermal coefficient, and T is the absolute temperature in Kelvin. Thermistors are widely used for temperature measurement by monitoring resistance changes. By applying the above formula, the temperature can be accurately determined, making them ideal for precision applications.

3.Power-Based Measurement

The relationship between power consumption and temperature rise can be expressed as:

where P is the device's power dissipation, k is the thermal resistance, Tj is the junction temperature, and Ta is the ambient temperature. By measuring P, the temperature rise can be deduced, allowing the estimation of Tj.

Infrared thermography can be combined with power-based calculations to map the temperature distribution across the device. This approach provides a detailed visualization of thermal hotspots and overall heat dissipation.

Common Measurement Methods

1.Contact Measurement

The direct contact measurement method involves placing a thermocouple or temperature sensor on the surface of a semiconductor to obtain temperature data. This approach provides accurate localized temperature readings and is commonly used for temperature studies and calibration tests in laboratory settings.

However, this method has certain limitations. Physical contact may interfere with the normal operation of the device, making it challenging to accurately capture rapid temperature changes during dynamic processes. Additionally, the size and sensitivity of the sensor may restrict its application to small semiconductor devices.

2.Non-Contact Measurement

Infrared Thermography: This method utilizes the relationship between radiation intensity and temperature. Infrared cameras detect the infrared radiation emitted by an object, which is directly related to its temperature. It allows for real-time, non-invasive temperature measurements.

Laser Raman Spectroscopy: This technique measures the frequency shifts in the Raman scattered light caused by changes in the material's lattice vibrations, which are temperature-dependent. By analyzing these shifts, the temperature of a semiconductor or other material can be accurately determined.

Application Examples

Example 1: Temperature Monitoring and Dynamic Adjustment in Power Transistors

In power transistors, real-time temperature monitoring is critical to ensure reliability and prevent overheating. By using the formula P=k⋅(Tj−Ta), the junction temperature Tj can be calculated based on power consumption and thermal resistance:

Scenario: A power transistor dissipates P=20 W under normal operation. The thermal resistance k is 2 °C/W, and the ambient temperature Ta is 25 °C.

Calculation:

To dynamically adjust the operating parameters and prevent overheating, temperature sensors or thermal feedback circuits can be used to modulate input power or activate cooling mechanisms, keeping Tj below the critical threshold.

Example 2: Integrating thermal simulations and measurements to optimize chip design and heat dissipation structures.

Example 2: Optimizing Heat Dissipation in Chip Design via Simulation and Measurement

In chip design, thermal management is vital to maintaining performance and preventing failures. By combining heat simulations and direct measurements, designers can optimize the chip layout and cooling strategies.

Scenario: A chip generates 10 W of heat. Using a thermal simulation, a heat sink with thermal resistance ksink=1.5 °C/W is selected. Infrared thermography confirms the temperature distribution, and the results show a maximum Tj of 75 °C.

Optimization: The design is modified by adding copper thermal vias to enhance heat transfer, reducing ksink to 1.2 °C/W.

Revised Calculation:

By integrating simulation and measurement, the optimized design achieves better thermal performance, ensuring long-term chip stability and efficiency.