Troubleshooting manufacturing process needs more comprehensive analysis of the wafers in different process steps. Often these tests are out of scope of in-line and offline process control tools. For this purpose Semilab can offer state-of-the art laboratory tools with multiple capabilities.
These advanced metrology tools can be effectively used in the research and development field to introduce new methods and techniques for high efficiency solar cell production.
Semilab is open for cooperation with customers to improve the tool performance and introduce new applications to cover future metrology needs.
The measurement tools were designed to achieve good tool performance, user-friendly operation and low cost of ownership.
The applications include the following:
Deep Level Transient Spectroscopy (DLTS) is a powerful technology for the detection and identification of electrically active defects (known as traps) in semiconductors, due to contamination or crystal defects. It is an extremely versatile method for determining all parameters associated with deep traps including energy level, capture cross section and concentration distribution. It permits identification of the impurities and is capable of detecting contamination concentrations below 5*107 atoms/cm3.
DLTS is a destructive technique, as it requires forming either a Schottky diode or a p-n junction with a small sample, usually cut from a complete wafer.
Semilab’s DLTS system is composed either of the DLS-83D, DLS-1000 or DLS-1100 and one of the four cryostats Semilab offers.
Majority carrier traps are observed by the application of a reverse bias pulse, while minority carrier traps can be observed by the application of a forward bias pulse.
The technique works by observing the capacitance transient associated with the change in depletion region width as the diode returns to equilibrium from an initial non-equilibrium state.
Capacitance transients generated by changing of the Voltage:
Because the emission process is very fast, the capacitance transient is small and noisy. In order to slow down the emission process, different kind of cryostats can be used for cooling the sample (usually in the range from 30 K to room temperature 300 K or above). The result of the cooling is a longer transient. By using a lock-in averaging technique, peaks at a particular emission rate are detected as a function of temperature. By looking for emissions at different frequencies and monitoring the temperature of the associated peak, an Arrhenius plot allows for the deduction of a trap's activation energy. By varying the pulse width, it is possible to determine the capture cross section precisely.
Sample quality test by I-V, C-V
Interfacing to a broad range of cryostats
Complete range of measurement modes:
Optional digital or analog control of settings to allow real ease of operation
DLS-1000 is an improved, high sensitivity system. It is eight times more sensitive than its predecessor, the DLS-83D.
The DLS-1000 offers a fully automatic measurement mode as well as providing complete interpretation of the measured data, including impurity identification and concentration determination without any need for user interaction.
The deep level transient spectroscopy (DLTS) is the best technique for monitoring and characterizing deep levels caused by intentionally or unintentionally introduced impurities and defects in semiconductor materials and complete devices. It is an extremely versatile method for determining all parameters associated with deep traps including energy level, capture cross section and concentration distribution. It permits identification of the impurities and is capable of detecting contamination concentrations below 2*108 atoms/cm3.
Semilab offers the following Cryostats to use with the DLS tools:
Automatic He (closed cycle) vacuum cryostat: 30 K–325 K. Controller is commercial LakeShore – controlled by the DLS control software.
Vacuum cryostats require vacuum pump (not included by default)
DLS-1100 Deep Level Transient Spectrometer provides metrology of the highest sensitivity for characterization and identification of impurities for the wafer maker market.
The new technologies - a low-vibration cryostat with improved signal-tonoise ratio, a more accurate temperature controller and
the improved evaluation software - allow for automatic control of the experimental parameters and automatic evaluation of impurity concentration, activation energy and for cross section captures on semiconductor samples.
Electrically active defects’ identification and complete range of measurement modes, including:
DLS-1100 system can be combined with different cryostats capable of measuring with different temperature ranges: