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Abstract

The Helmholtz Innovation Lab BlitzLab is part of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). BlitzLab aims to develop and optimize methods of ultra-short-time annealing for various fields of application. This is done in cooperation with industrial partners. The primary goal is to disseminate and transfer these technologies to industry and application-oriented research areas. BlitzLab offers its cooperation partners access to a tempering laboratory with several flash lamp and laser systems and, in cooperation with the HZDR, to many other methods of material treatment and material analysis.

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Background

 

In the thermal treatment of materials using ultra-short time annealing (usA), high temperatures are applied for very short times (nano to milliseconds), so that only near surface regions of the material are exposed to the maximum temperature, while the majority is not or only moderately heated. The Innovation Lab focuses on usA technology for the fields of application like functional semiconductor layers, printed electronics and sensors and battery technology. Because usA enables a synthesis of new materials, further application fields are thinkable.

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Images & Videos

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Problem

During flash lamp annealing (FLA) an energy storage is discharged via a single flash lamp or a field of flash lamps. The resulting light pulse is absorbed by the substrate or wafer and converted into heat. The reflector maximizes the light intensity on the front side of the substrate, while an optional pre-heating system in the back (usually a heating plate or halogen lamp) preheats the substrate. This enables higher maximum temperatures to be reached while reducing thermal stresses.

The discharge of the energy storage device generates a current pulse, which is converted into a light pulse inside the flash lamp (Fig. 2). Pulse time and pulse shape are essentially determined by the electrotechnical circuit of the energy storage device (e.g. a specific coil-capacitor combination). Typical pulse times range from a few 100 µs to a few 10 ms. The pulse time roughly corresponds to the half width at full maximum of the light or current pulse.

These ultra-short annealing technologies have several advantages over conventional thermal treatments:

• Energy saving, since only regions near the surface are heated
• Process time savings (or higher throughput)
• Use of temperature-sensitive substrates, which are usually cheaper and less harmful to the environment
• Synthesis of new materials in thermal non-equilibrium

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Solution

The light pulse shows a broadband spectrum from UV to the near infrared range with a maximum in the blue-green spectral range. With increasing intensity of the light pulse there is a slight shift towards the UV range. In case the substrate is UV-incompatible, the UV component can be filtered out.

The light pulse is usually absorbed in the substrate’s near-surface regions. At the same time, the generated heat is dissipated by thermal conduction towards the backside. As a result, the temperature on the substrate surface rises, reaches a maximum value T_max and then drops to an equilibrium value T_equ. In contrast, the temperature on the backside rises continuously to T_equ. The thermal stress on the backside is therefore significantly lower than on the front side. The shorter the pulse time and the smaller the thermal conductivity of the substrate, the greater the difference between the front and backside.

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Advantages

• Significant savings of process time
• Significant energy savings
• Synthesis of new materials
• temperature-sensible substrates
• Access to the Blitzlab resources: Tooling, Technology, Know-How

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Scope of application

BlitzLab focuses on new materials and processes for the following application fields:

 

• electronics and printed electronics
• sensors and photovoltaics
• energy storage materials and technology

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Service

BlitzLab offers to customers:

• Processing of materials of your interest for industrial or scientific applications
• Research and validation projects on usA
• Process development for the thermal treatment of materials
• Services in the field of usA
• Methods of material analysis and ion beam technology in cooperation with the Ion Beam Center (IBC) at HZDR