Self-assembly Technology-The New Direction of Chip Manufacturing(2)
In other words, self-assembling nanostructures can be achieved using molecular engineering. These structures can be linear, cylindrical and they also fit the periodicity of our design. Having the ability to self-assemble these structures solves only half the problem when we use chemical engineering to make the nanoscale features required for transistors.Because they also have to be arranged so that transistors can form circuits.
For this problem, Karl Skjonnemand suggested that a wide-oriented structure could be used to fix the self-assembly structure. They are anchored in place so that the remaining self-assembled structures can be aligned in parallel with our steering structure. For example, it is very difficult for traditional projection technology to make a fine line of 40nm. We can make a 120nm guide structure first using ordinary projection technology, which will put three 40nm lines together allowing the material to be automatically reproduced in the most sophisticated detail.
However, there are other challenges, such as the need for the system to be perfectly aligned. Because any small flaw in the structure will cause the transistor to lose efficacy, chemical cleaning methods are used to eliminate the nanoscale minimum fault.
When will self-assembly technology be used in commerce?
In fact, prior to Karl Skjonnemand, a number of research institutions have tried to apply self-assembly technology to semiconductor chip manufacturing and made some breakthroughs in recent years.
Back in 2012, Belgium's research centre for microelectronics (IMEC) installed the world's first self-assembly line in its own factory where scientists improved materials and designs to reduce errors in self-assembled structures.
In addition, State University of New York (SUNY) also operated a self-assembling production line in the Center for Nanoscale Engineering in Albany.
At the Semicon West in 2014, An Steegen suggested that self-assembly technology appears to be an alternative to extreme ultraviolet photoetching to extend the life of existing photoetching. IMEC can now use self-assembly technology to design structures similar to Intel's latest chips, as small as 14 nanometers. Steegen suggested that the self-assembly technology was expected to replace EUV at that time.
Christopher Borst, associate professor of nanoengineering at the State University of New York's nanoscale engineering center, suggested its production lines now reliably produce repetitive lines and fin-like structures up to 18nm in detail. "We made some impressive structures," Borst said. "This method is already no problem with materials and manufacturing capabilities. "
In early 2016, researchers at the national institute of standards and technology (NIST) and IBM developed a trenching technology that could be used to build semiconductor chips through directed self-assembly. Obviously, this trenching technique is similar to the "steering structure" that Karl Skjonnemand described earlier for creating self-assembling semiconductor chips.
In 2017, a group of researchers from the Massachusetts institute of technology and the university of Chicago announced that they had found a way using "self-assembly" technology to develop narrower line widths that could potentially be used in standard mass-economy production devices.
Karen Gleason, vice provost and professor of chemical engineering at MIT, expressed that advanced chip processes often require very expensive EUV optical technology or create line-by-line images by scanning electron or ion beams on the surface of chip, which are too slow and expensive.
The MIT researchers' solution is to first use lithography now widely used to create circuit patterns on chip surfaces. Material layers using "block copolymers" later will naturally separate into alternate layers or other predictable patterns formed by spinning the coating solution. Block copolymers are chain molecules formed by two different polymers.
"The dimensions of the two blocks may determine the periodic layer dimensions or other patterns that will self-assemble at deposition. The latter protective polymer layer is first placed in block polymers and is managed by chemical vapor deposition (CVD). This process is key, which constrains the self-assembly of block polymers forcing them to form vertical rather than horizontal layers.The underlying lithographic pattern will guide the positioning of these layers, but the copolymer will naturally cause its width to be smaller than the baseline width. Meanwhile, because the top polymer layer can also be patterned, the system can be used to create more complex patterns, such as the interconnection of microchips."
the MIT researchers explained that most current chips use existing photolithography and CVD is easy to understand making it easier to implement the new technology with familiar equipment and materials.
In 2018, the research team of professor Miao Qian, department of chemistry, Chinese university of Hong Kong, invented organic semiconductor materials with unique self-assembling structure and synthesized Hpopylene derivative with different functional groups, and found a rare molecular stacking mode in its crystal structure. These hpopperylene derivatives have a twisted conjugate skeleton forming a unique brick structure in the crystals and maintain a fairly uniform two-dimensional pi-pi packing pattern independent of functional groups. At the same time, professor Miao Qian's research team has successfully prepared chemical and biological sensors with high selectivity and sensitivity based on the organic thin film transistor and micro flow pipeline
A stacking pattern of hpopylene derivatives
From the above figure, we can see that the stacking pattern of the organic semiconductor has a highly consistent periodic structure and each structure is less than 2nm in length and width.
For now, of course, using "self-assembly" technology to build semiconductor chips is still in the lab or pilot production stage and there are still some issues to be resolved before it be commercially available on a large scale.For example, Karl Skjonnemand mentioned that the "any minor defects in the structure" need to solve. Besides, there also needs to be a set of development tools that chip design companies can use to develop self-assembly technologies and materials.
However, compared with traditional semiconductor manufacturing technology, "self-assembly" technology will help to drive the improvement of chip manufacturing process and greatly reduce the cost of advanced chip manufacturing.
"Continue to expand the computing and digital revolution through self-assembling materials could be the dawn of a new era of molecular manufacturing. " Karl Skjonnemand said.