A corporate researcher requested the following.
Hi, I am looking for a lab that can help to measure the MCL value (Minority Carrier Lifetime) of pure silicon wafer. Hopefully, you have a lead on this matter. Let me know if we can discuss further.
We would like to measure the “Bulk” MCL of a 4” round pure silicon wafer. I assume it should be a nondestructive test.
We would like to measure about 9 points on the wafer as image or 5 points (1 center and 4 corners). But if one point is all that they can, we can explore it as well
UniversitWafer, Inc. Replied
Do you have information on their purity? Are they polished or etched or different? Tentatively pure virgin Si wafer How many would you like to measure? 1 wafer for now.Can you send a photo of box with the wafers?
I am familiar that Usually the wafer is measured in just one point (center) for MCC Lifetime. I have to ask if more points can be measured.
Reference #277641 for specs and pricing.
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9-Point Minority Carrier Lifetime
A semiconductor physics researcher requested the following answer:
Question:
Do you have the data for minority carrier lifetime of Si wafer of following specification?
Answer:
Minority carrier lifetime of Si wafer : >100us Please let us know if you need anything else.
Reference #201773 for specs and pricing.
Minority carrier lifetime is a critical parameter in semiconductor devices, and understanding its importance requires a bit of background knowledge on how semiconductors function.
1. Semiconductors and Carriers:In semiconductors, there are two types of charge carriers: electrons (n-type carriers) and holes (p-type carriers). When an external voltage is applied, these carriers move, resulting in current flow. The majority carriers are those that are abundant in a given type of semiconductor (for instance, electrons in n-type semiconductors), while the minority carriers are less in number (holes in n-type semiconductors).
2. What is Minority Carrier Lifetime?Minority carrier lifetime refers to the average time a minority carrier exists before it recombines with a majority carrier. This recombination results in the annihilation of both carriers and cessation of current due to them. In essence, it's a measure of how long a minority carrier can effectively contribute to current flow before it disappears.
3. Importance of Minority Carrier Lifetime:
Solar Cells: In photovoltaic (PV) cells, when photons hit the semiconductor material, they generate electron-hole pairs. The efficiency with which these carriers can be separated and collected determines the cell's efficiency. A longer minority carrier lifetime means these carriers can travel longer distances without recombining, leading to higher efficiencies.
Bipolar Junction Transistors (BJTs): In BJTs, the operation of the transistor depends on the injection and recombination of minority carriers. A longer minority carrier lifetime ensures a more efficient operation and amplification.
LEDs and Lasers: In light-emitting diodes (LEDs) and semiconductor lasers, the emitted light results from the recombination of electrons and holes. The brightness and efficiency of these devices can be influenced by the minority carrier lifetime.
Reduced Power Loss: In devices like diodes and transistors, recombination of carriers can lead to power loss. A longer minority carrier lifetime reduces this loss, resulting in more energy-efficient devices.
Device Speed and Frequency Response: In high-frequency applications, the speed at which a device can operate is influenced by how fast carriers can be injected and collected. A longer minority carrier lifetime can affect this speed.
4. Influence on Device Characteristics: The minority carrier lifetime affects various parameters like diffusion length (how far carriers can travel), which in turn affects junction depths, device structures, and ultimately the performance of semiconductor devices.
5. Impact on Device Reliability: High recombination rates can lead to local heating and hot spots in semiconductor devices. By optimizing minority carrier lifetime, device reliability and lifetime can be enhanced.
In conclusion, minority carrier lifetime plays a pivotal role in determining the performance, efficiency, and reliability of a wide range of semiconductor devices. Understanding and optimizing this parameter is crucial for device design and advancement in the semiconductor industry.
The minority carrier lifetime in a pure silicon wafer is a crucial parameter that can vary based on the quality of the silicon, the presence of defects, impurities, and the methodologies used in its preparation. In the context of a perfectly pure and defect-free silicon, which is an ideal rather than the norm, the minority carrier lifetime can be relatively long.
In practice, however:
Intrinsic Silicon: For high-quality intrinsic (undoped) silicon, the minority carrier lifetime can range from microseconds (µs) to milliseconds (ms).
Doped Silicon: When silicon is doped to make it either p-type or n-type, the carrier lifetime typically decreases because of the increased number of recombination centers. In practical, commercially available doped silicon wafers, carrier lifetimes might often be in the range of microseconds.
Impact of Defects and Impurities: Even trace amounts of certain impurities or defects can have a significant impact on carrier lifetime. For instance, metals like iron or gold can drastically reduce the minority carrier lifetime in silicon.
Measurement Techniques: There are different techniques to measure minority carrier lifetime, like the photoconductance decay method, time-resolved photoluminescence, etc. The values can vary slightly depending on the measurement technique used.
It's important to note that while there are general ranges, the exact value for a specific silicon wafer would need to be determined experimentally. If you're working with a specific silicon wafer or need precise values, it's recommended to refer to the manufacturer's specifications or conduct direct measurements using appropriate equipment.
An R&D Engineer needed help with the following:
We would like to order 25x DSP, n-typ, FZ, 100mm, 1-0-0, 275 µm and 100x DSP, n-typ, FZ, 150mm, 1-0-0, 275 µm with the following minimum requirements: 4” Material 6” Material Resistivity (Ohm-cm): < 3 Minority carrier lifetime (ms): > 5.8 > 13 Thickness (µm): 280 ± 10 Total Thickness Variation (µm): < 3 < 1.5 Bow (µm): < 2 < 3.5 Could you provide those and if send a quotation for that?
University Wafer, Inc. Replied:
The geometric specifications, specifically TTV, Bow and thickness tolerance, are extremely difficult. We can meet them, but the wafers would be very expensive. Also, I am surprised at the very tight specification on Bow without there being a corresponding specification on Warp. Please check if you can loosen some of your specifications.
We do have available 100mmØ FZ ingot and 150mmØ FZ ingot with resistivity <3 Ohmcm. However, I question if the Minority Charge Carrier Lifetime that you specified is achievable at the specified doping level (at Ro<3 Ohmcm).
The 100mmØ FZ ingot that we have available has resistivity (0.98-1.02)Ohmcm, but MCC Lifetime has not been measured on it.
Another such FZ ingot, from the same manufacturing process, with resistivity of 110 Ohmcm has measured MCC Lifetime of 11,558µs but with doping 30 to 100 times heavier, the MCC lifetime is bound to be much shorter.
The 150mmØ FZ ingot that we have available, with resistivity (1.01-1.02)Ohmcm, has measured MCC Lifetime of 1,571µs, but that is much shorter than you specified. Another such FZ ingot from the same manufacturing process, with resistivity of 16.8 Ohmcm has MCC Lifetime of 14,467µs but with heavier doping, the MCC lifetime is bound to be shorter.
If the ingots that we have available would be suitable for you then we would be happy to prepare a price quotation for the wafers that you specified.