Application
CONTAMINATION ANALYSIS
Semilab offers various solutions to analyze semiconductor samples. These are all aimed to give as much information on the subject as possible to help people understand the sources of the behavior and properties of their samples and the effects of the used processes.
Using the state-of-the-art Deep Level Transient Spectroscopy (DLTS) setup of the Semilab DLS-1000, it is possible to perform qualitative and quantile analysis of the electrically active impurities in the semiconductor, although this is a destructive technique. This method provides information about the activation energy of the impurity and cross-section capture. It also allows the detection of concentration impurities down to 2×108 atoms/cm3,depending on the doping concertation.
Figure 1. Contamination analysis
Technology
DEEP LEVEL TRANSIENT SPECTROSCOPY
The Deep Level Transient Spectroscopy (DLTS) is a powerful technology for the detection and identification of electrically active defects (known as traps) in semiconductors. These can occur due to contamination or crystal defects. It is an extremely versatile method for determining all parameters associated with deep traps, including energy level, capturing cross-section and concentration distribution. It allows the identification of the impurities and is capable of detecting contamination concentrations below 2×108 atoms/cm3.
DLTS is a destructive technique, as it requires the forming of either a Schottky-diode, or a p-n junction with a small sample, usually cut from a complete wafer.
The system is composed either of the DLS-83D, or DLS-1000 and one of the four cryostats that Semilab offers.
Figure 2. Measurement results
The majority carrier traps are observed by the application of a reverse bias pulse, while the 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.
Figure 3. Capacitance transients generated by voltage change
As 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 the deduction of a trap's activation energy. By varying the pulse width, it is possible to determine the capture cross-section precisely.
Figure 4. DLTS peak identification
Figure 5. Activation energies for various impurities
ARRHENIUS PLOT LIBRARY:
Figure 6. Measurement results
Figure 7. Measurement results
FEATURES
- State-of-the-art contamination identification with the highest sensitivity available on the market
- Complete range of measurement modes, including temperature scan, frequency scan, depth profiling, C-V characterization, capture cross-section measurement, optical injection, conductance transient measurements
- Controlled by user-friendly GUI
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Sample quality test by I-V and C-V
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Full computer control with extensive software support featuring the latest evaluation procedures of physics of deep levels developed, library database for accurate contamination determination
- Different cryostats with wide temperature ranges are available, depending on the application requirements
Product Line
DLS
Interfacing to a broad range of cryostats
Complete range of measurement modes:
- Temperature scan
- Frequency scan
- Depth profiling
- C-V characterization
- Capture cross-section measurement
- Optical injection
- Conductance transient measurements
Optional digital or analog control of settings to allow real ease of operation
- Sample quality test by I-V, C-V
- Full computer control with extensive software support, complete library database for accurate contamination identification
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Products
DLS-1000
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.
Key Features
- Highest sensitivity (2*108 atoms/cm3) for detection of trace levels of contamination
- Interfacing to a broad range of cryostats
- Wide range of measurement modes:
- temperature scan
- frequency scan
- depth profiling
- C-V characterization
- capture cross section measurement
- optical injection
- conductance transient measurements
- controlled by digital and analog settings to allow real ease of operation
- sample quality test by I-V, C-V
- full computer control with extensive software support, complete library database for accurate contamination identification
DLS-83D
The DLS-83D offers a fully automatic measurement mode, as well as provides 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, capturing cross-section and concentration distribution. It allows the identification of the impurities, and is capable of detecting contamination concentrations below 109 atoms/cm3.
Features and system specifications:
- Highest sensitivity (109 atoms/cm3) for detection of trace levels of contamination
- Interfacing to a broad range of cryostats
- Wide range of measurement modes:
- temperature scan
- frequency scan
- depth profiling
- C-V characterization
- capture cross-section measurement
- optical injection
- constant capacitance feedback loop
- conductance transient measurements
- MOS interface state density distribution
- controlled by digital and analog settings to allow real ease of operation
- sample quality test by I-V, C-V
- full computer control with extensive software support, complete library database for accurate contamination identification
Cryostats for DLS
Semilab offers the following Cryostats to use with the DLS tools:
- Bath type cryostat: 80 K-450 K –– heating is computer-controlled – controller built into DLS-1000. Convectional (in LN2 atmosphere)
- Automatic LN2 cryostat 80 K-550 K (maximum 800 K optional). Sample in the vacuum chamber – requires computer-controlled heating and cooling (by LN2 boiling), requires controller – built into the DOS PC and cryostat control unit.
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Automatic He (closed cycle) vacuum cryostat: 30 K–325 K. Controller is commercial LakeShore – controlled by the DLS control software.
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Vacuum cryostats require vacuum pump (not included by default)