Full-area representation of warpage, waviness, and roughness opens up new possibilities for characterizing grinding processes. With this new capability, the center area of a wafer grinding can be checked for quality from its edges. Using such a tool, manufacturers can improve their quality control and yield. Here are the advantages and disadvantages of back grinding. You should also know the tools used in back grinding. After all, the process may seem expensive at first, but over time it can lead to near-perfect flatness.
Disadvantages of back grinding
Back grinding is the process of reducing the thickness of a wafer through a process called tape lamination. This process involves adhering an adhesive tape to the front of the wafer. During back grinding, silicon compound spreads outward in all directions.
However, back grinding can be disadvantageous. Back grinding can result in the reduced thickness of the wafer, and the thinner the wafer is, the better. This process allows a higher stacking density, but also lowers performance. In addition, the process is expensive and requires the use of high-quality materials. Further, back grinding can reduce the thickness of wafers to a point where a back-ground wafer may be thinner than a normal one.
Another disadvantage of back grinding is that it creates a lot of silicon dross. It is important to ensure that your equipment is capable of recycling the silicon dross after grinding. Otherwise, it can lead to brittle wafers. It is also expensive to purchase specialized tools for back grinding. Back grinding is a good choice if you want to achieve super-fine polishing.
Electronic devices and passive components may protrude from the active surface of the wafer. In such cases, it is important to grind back the surface of the wafer so that bumps do not remain exposed to the environment. The back surface of the wafer also helps prevent damage to any electrical components or wires on the wafer.
Lapping is a very inefficient process. As a result, it is not a good choice for large-scale manufacturing. But if you need a smaller scale production process, back grinding can be a good choice.
Techniques to reduce waviness structures in wafers
While waviness is not easy to quantify using conventional methods, minimizing its effect on wafer quality requires post-slicing processing operations that lead to time and material loss. As wafer processing continues to improve, techniques that reduce waviness are needed.
To achieve this, the processor 20 calculates a statistical parameter of waviness from a plurality of positions of the wafer. For example, the processor 20 calculates a waviness capability parameter, which is the average waviness value minus three standard deviations from each site. The paper presents a finite-element analysis of soft-pad grinding of wire-sawn silicon wafers and discusses mechanisms of waviness reduction.
Optical detection systems can also be used to detect defects on nonpatterned wafers. Optical systems that use sub-100 nm sensitivity are based on similar operating principles as those used in larger-scale defect detection. They use DUV illumination-enhanced optical systems. This technique requires high-precision and repeatability in the motion control of the wafer stage.
Proton induced exfoliation is one promising kerfless method. The technique can be applied in a wide variety of semiconductor applications. This technique is effective for thin wafers and improves light trapping properties. However, the cost of a special proton implanter is prohibitive, and is likely to limit its commercialization.
Electrochemical defect delineation is another method for identifying defects on silicon wafers. This method involves electrically connecting the surface of the silicon wafer to a control voltage within a certain range. The silicon wafer is then exposed to an electrolyte. The electrolyte is removed by the method, revealing defects and metal contamination. For the same reason, this technique is effective for thin-film SOI and SOS silicon wafers.
Processes to achieve near-perfect flatness after back grinding
There are several different types of back grinding. These processes have the advantage of minimizing the possibility of debris or warpage of the ultra-thin wafer. In addition to reducing debris, they also provide near-perfect flatness on the sample. The following paragraphs describe the different types of back grinding. These methods are based on the requirements of each manufacturer.
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Tools used for back grinding
The process releases the pieces, and the result is minimal backside chipping. Tools used for back grinding wafers include diamond backgrounding wheels. In addition to diamond backgrounding wheels, other tools used in this process include a grinding wheel, a chuck table, and a polishing pad.
This reduces the number of steps required during scribing and packaging. The process minimizes chip damage by reducing the thickness of a silicon wafer. Tools used for back grinding wafer may include diamond or alumina back grinding wheels. Depending on the thickness and shape of a silicon wafer, they may include an assortment of tools.
In a multi-step process, tools used for back wafer are different. In the first step, large grit wheels are used to remove a majority of the excess wafer thickness. A second step uses fine grit to polish the wafer, and a third step is to remove any remaining material. Wafers with 200 mm in diameter usually start at 720 um, and coarse grinding removes about ninety percent of the excess material.
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