There are many aspects of wafer grinding that make this process a success or a failure. These include die strength, Die roughness, Grinding wheels, Automated measurements, and more. Read on to learn more. We will discuss some of these key factors in this article. The best way to ensure a successful wafer grinding process is to do research and experiment with different processes. And as you do so, you will be able to choose the right option for your manufacturing needs.
Die strength
In the field of semiconductor fabrication, die strength is an important factor affecting the performance of the die used in wafer grinding. This property determines the reliability of the die under various conditions, and it determines the manufacturability of the process. The die’s strength is also affected by surface conditions, the type of substrate it is attached to, and temperature excursions. Most high-power applications mount the die directly onto a high-conductivity material. This mismatch in the thermal coefficient of expansion (TCE) causes a significant amount of mechanical stress on the die, especially during temperature excursions. Similarly, fatigue strength of a die is lower than static strength.
The backside surface of a silicon wafer demonstrates a scratch pattern. The depth of the scratch depends on the grit size of the wheel, and the vertical pressure applied during the grinding process. As a result, finer grit results in smaller scratches. The deeper the scratches, the lower the strength of silicon. Thus, a smooth backside surface is essential to minimize the impact of scratches on the wafer’s strength.
To investigate how to measure the die strength, the team used silicon wafers ground with different grit sizes. It was found that a 2000-grit grinding process required 50 percent more stress to break the die than a 1200-grit grinding process. They compared the two-grit grinding processes using different abrasive materials and tested the strength of the dies by rupturing a ball.
While the operation conditions of the two-abrasive members in wafer grinding were similar, their grain sizes were different. This was largely due to the different grinding process and abrasive member A used in the experiments. The results revealed that the two-abrasive member A and B were capable of delivering similar grain sizes, but different operational conditions. The results indicated that the DBG process is more efficient for wafer grinding than the combined TGM and dry polishing processes.
Die roughness
The use of full area representation of die roughness when wafer grinding opens up new opportunities for describing grinding processes. For example, it is possible to measure the quality of the surface from edge to center of a die. In addition, it is possible to compare waviness and warpage in a full-area representation. Both of these aspects are important in quality assurance and are worth investigating. Below are three examples of the impact of die roughness.
Fine-grained wafers have the best surface finish, while coarse-grained wafers have greater roughness. In contrast, polished surfaces have the lowest warpage and best die strength. This process requires a separate step of mechanical polishing, which removes only 2 to 3um of material from the surface. CMP is also an effective process for achieving the highest planarization, but is more expensive and dirty. Also, it requires mounting the wafer to a backing film. Lastly, backing films are difficult to remove and leave residue on the front side of the wafer.
A new method for measuring die surface roughness during wafer grinding utilizes a scattered-light sensor technique. The technique combines surface roughness measurement with deflectometry to measure form and waviness. The measurement accuracy is 0.1 nm. The method has been validated for high-precision measurements and has demonstrated excellent accuracy. A new sensor is currently available for measuring the full surface of a wafer.
A common problem with backside grinding is a reduction of wafer thickness. It also introduces intrinsic stress and subsurface microcracks into the wafer. Both of these conditions make the wafer brittle, and it is likely to crack during transport and singulation. Additionally, the dies obtained after wafer grinding can also break down during downstream processes. Removing subsurface microcracks and stress from wafers is desirable for recovery of wafer strength and preserving the surface roughness.
Grinding wheels
When it comes to abrasive grains, the IF Series in-feed grinding wheels are excellent for silicon, crystals, and compound semiconductors. These wheels come in environmentally-friendly packages with an ABS or PP resin. The diamond grit on these wheels helps improve process quality and wheel life. The IF Series in-feed grinding wheels are capable of precision grinding to planarize etched wafers. To improve process quality and increase wheel life, these wheels are packaged with an environmentally-friendly plastic resin.
The Wafer Grinding Wheel market report includes comprehensive market statistics that identify the growth drivers, challenges, and opportunities. This report also outlines competitive data type analysis, including revenue and sales of Wafer Grinding Wheel. It also examines regional and country development trends. The report also highlights the global market’s size, share, and forecast. Once the grinding process is complete, the resulting wafer is ready for further processing.
The IC silicon wafer manufacturing industry requires high-quality silicon wafer grinding wheels. The high-quality silicon wafers produced by this process can achieve nano-scale roughness and damage layer thickness. Abrasive wheels for the IC silicon wafer industry must be able to meet these demands, as well as low price. They must also have self-dressing capabilities and low wear on the surface of the wafer. Moreover, the product must have good life span.
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Automated measurements
The manufacturing of microchips and other technologies often requires precise measurements to ensure that the final product is as high-quality and reliable as possible. Manufacturing tolerances are a crucial aspect, as even small deviations can affect downstream steps, resulting in lower yields, reduced efficiency, and decreased reliability. Automatic measurements for wafer grinding will provide an additional layer of confidence to the process.
The method comprises one or more pressure transducers that measure the pressure on the surface of the wafer before grinding. These pressure transducers are capable of factoring out the initial pressure to obtain a predetermined final pressure. The measurement system will automatically adjust to compensate for any variations.
The Park NX-Wafer features a fully automated tip exchange system that can seamlessly continue automated measurement routines. The system automatically calibrates the cantilever position based on the reference pattern. It also provides fast, reliable, and accurate measurements, with a 99% success rate.
TAIKO process
The TAIKO process is a back grinding method that thins the inner circumference of a wafer while leaving an edge on the outermost circumference. The process is highly effective in reducing warpage and risks associated with handling thin wafers. It also prevents out-gassing from the wafer during high-temperature processes. Lastly, TAIKO minimizes the possibility of chipping and cracking due to warpage.
The Taiko grinding process leaves a ring of silicon on the outer edge of a wafer. This ring allows backside processing without requiring major changes in the equipment. The ring is then removed before dicing or assembly. Taiko grinding is available to Optim customers either on their own product or blank test wafers. It is highly recommended that all IC manufacturers use this process to reduce the warpage and increase the yield of their ICs.
Wafer grinding is a necessary step for semiconductor device fabrication. It reduces the thickness of a wafer, allowing high-density packaging and stacking of integrated circuits. Wafers are made of silicon and are usually 200-300 mm in diameter. In addition to being thick, silicon wafers are thick enough to provide minimum mechanical stability and avoid warping during high-temperature processing.
The described method begins with a too-bowed wafer. The front part of the wafer is excised, and the marginal portion is trimmed to a desired thickness. Then, the rear part of the wafer is polished by dicing or by grinding technics. A second, optional step involves a ring-cutting process. This step requires an extra step of polishing to ensure that the wafer has a smooth surface.
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