As early as more than 60 years ago, American theoretical physicist Richard Feynman proposed: "In the future, we can arrange atom in the way we want!"
is aimed at the advanced process nodes of integrated circuits, with extremely small line width, ultra-high density, and three-dimensional integration of new materials and new device structures, putting forward extremely strict requirements on the accuracy and reliability of process technology .
Recently, the team of Huazhong University of Science and Technology proposed a high-precision thin film deposition solution that "simplifies the tradition" and used selective atomic layer deposition technology (ALD) to conduct dielectric layer stack deposition on a series of oxide substrates.
Compared with cumbersome multi-step processes such as lithography and etching, the above-mentioned selective atomic layer deposition can realize the "one-step" dielectric layer alignment growth on an oxide substrate. This method can improve the manufacturing efficiency and accuracy of integrated circuits and avoid overturning errors, which is expected to accelerate the progress of miniaturization processes in the semiconductor field and provide a new direction for the next generation of nano-manufacturing processes.
related achievements have attracted the attention of international semiconductor technology giants. TSMC, the world leader in advanced processes, believes that: "Selective ALD can better control the deposition process and is an enablement technology in the advanced nodes of semiconductor [1]."
South Korea Samsung commented on Applied Surface Science , saying: "Regional selective ALD Reducing the number of process steps to achieve self-aligned manufacturing is a way to save time and cost [2]. "Professor Gregory N. Parsons, founder of
ALD Academy and founder of North Carolina State University, told the media: "We are excited to witness the emergence of an innovative method transformation from top to bottom. Selective atomic layer deposition technology is expected to help the field of microelectronics. Materials and manufacturing methods proposed by the team of Huazhong University of Science and Technology are applied in the electronic manufacturing process [3]."
In addition, the team's series of papers based on selective atomic layer deposition technology have also received widespread attention from researchers in this field, including Japan TEL and South Korea SK Hynix , Belgium IMEC, US Lam Research and Applied Materials et al. [4-8].
On July 27, the relevant paper was published in Chemistry of Materials under the title "Surface Acidity-Induced Inherently Selective Atomic Layer Deposition of Tantalum Oxide on Dielectrics" [9].
The first author of this paper is Li Yicheng, a doctoral student at the School of Mechanical Science and Engineering, Huazhong University of Science and Technology, and the corresponding author of jointly is Associate Professor Cao Kun of Huazhong University of Science and Technology, and Professor Chen Rong of .
Use the "one-step method" to achieve selective growth of similar material surfaces
Atomic scale collaborative manufacturing technology is the key to breaking through the accuracy limit of micro-nano manufacturing, and is the design and manufacturing basis of functional structures, devices and systems with a characteristic scale ranging from atom to nanometer range. Therefore, the application of in micro-nano electronics, nanomaterials and other fields is conducive to the realization of large-scale manufacturing. The characteristic of the selective atomic layer deposition technology is "selective", that is, it grows only at a specific surface or at a specific location, while other surfaces not selected can remain unchanged.
The main breakthrough in this study is that the selective growth of oxide substrate materials with similar surface properties is achieved through the "one-step method". In previous studies, selective deposition depends on substrates with large differences in surface properties, such as metals and dielectrics or semiconductors and dielectrics.
reviewer evaluated the study: "This study is very interesting because it obtains inherent selectivity on substrates with similar chemical properties and is very high."
On the other hand, the advanced chip process relies on repeated deposition-lithography-etching multiple steps, and the "one-step method" can be used to simplify some cumbersome and complex process steps. selective deposition on the fine patterned structure defined by one lithography can effectively avoid lithography overprinting errors, and reduce the same-precision secondary lithography steps by replacing multiple steps in one step.
In previous studies, selective deposition was used as templates to block specific areas by using small molecule inhibitors, single-layer passivation films, etc. As the characteristic size was further reduced and the demand for three-dimensional nanostructures increased, it became difficult to select a suitable molecular template. Inherent selectivity ALD is an important method to simplify the process because it does not use passivation molecular layer templates and removal steps.
, especially in advanced processes below 10nm, due to the reduction of feature size, the interconnection density is further improved, and the number of layers is increased to more than 10 layers, with high process cost and low yield.
This method takes advantage of the difference between metal and oxide, and uses the selection of precursor , the reaction temperature and partial pressure of to achieve high-precision self-alignment of low-dielectric materials on the oxide surface, which has great development advantages.
Figure 丨 Surface acidity-induced intrinsic selective atomic layer deposition on surfaces of similar materials (Source: Chemistry of Materials, this team)
This study began with an accidental experimental discovery. In the research process, the biggest difficulty lies in how to achieve differentiated selective deposition on similar oxide surfaces. They have experienced repeated trial and error, adjustment, and a cycle of progress and rise.
The team introduced: "In this similar oxide surface, if we want to achieve selective deposition, we need a large number of process attempts to amplify its surface differences."
Researchers discovered a specific hydrogen transfer mechanism for the atomic layer deposition precursor to react on the oxide surface, and found that in this system, the acid-base difference of the oxide carrier is a key factor affecting the chemical adsorption of the precursor on the surface, thus achieving selective deposition.
bottom-up structure "built" layer by layer
Usually, the chip process reflects the performance of the chip. Scientists often use 28nm, 14nm, 7nm, 5nm, etc. to represent the advancedness of integrated circuits. The smaller the process performance, the better.
Take the chip of the 5nm process in a mobile phone processor as an example. At such a small scale and such a high density, its manufacturing challenges are huge. can gradually improve the processing accuracy limit through innovation in principle and method improvement in basic research on selective deposition, which is expected to solve the problem of practical and complex nanostructure manufacturing.
At present, atomic layer deposition technology and selective atomic layer deposition are still in the exploration stage around the world. In other words, in atomic deposition technology, China and foreign countries are in a state of "parallel".
"This technology will take a long process in the field of chips. But it is worth noting that once foreign countries start to apply this technology to the field of chips, since we have developed abroad almost at the same time and have a similar technical level, we can achieve the technology's independence without being 'bottled'." The team said.
Figure丨Professor Chen Rong's team Selective Atomic Layer Deposition Group (Source: this team)
Of course, chip process is only one of the application scenarios of this technology. Growing on metals and growing high dielectric constant materials on some self-aligning growth with the metal gate surface can expand the process window so that the process can be truly used in the industry, including the research and development of related equipment, etc., so that the process and equipment can be matched.
is different from the bottom-up of general chemical deposition methods. Atomic layer deposition develops from top to bottom, which is equivalent to subverting the traditional processing and manufacturing process. From bottom to top, it means that unlike traditional top-down lithography, etching and other processes, "bottom-up" layer by layer "build" the structure like Lego building blocks , which can make the structure more refined and meet the market demand for the development of the integrated circuit field miniaturization.
The team introduced: "Selective deposition is the transformative technology expected by the industry. IMEC, Lam Research, TSMC, etc. are actively developing related technologies."
reports show that the fastest growing equipment in the integrated circuit industry and reaching double-digit numbers are lithography machine and atomic layer deposition equipment. This shows that atomic layer deposition is essential in the future advanced chip manufacturing process, and it is also one of the fastest growing directions in this field.
It is reported that the team has obtained basic display samples and is undergoing industrial transformation of technology with related companies. The team said, "In the future, we will strengthen cooperation with enterprises more to truly use the process in chip manufacturing. At the same time, we will also solve some engineering problems." If this technology is applied to the production line in the future, more problems that fit the actual production, such as process reliability, impact on process yield, process cost, etc.
33Deeply cultivated atomic layer deposition for more than ten years, and worked tirelessly for the ultimate solution in the field of nanomanufacturing
Professor Chen Rong is one of the earliest research scholars in selective atomic layer deposition technology, and has both relevant experience in industry and scientific research. She graduated from , Stanford University, and her research direction is the application of atomic layer deposition technology in the high-k/metal gate technology process in chips.
After graduating from his doctorate, Chen Rong held senior technical positions at American Applied Materials Company and the Intel Research Institute of the United States, engaged in the research and development of electronic device preparation process and related process equipment. In 2011, she returned to China and joined Huazhong University of Science and Technology and established an independent research team.
Professor Chen Rong's research group has been exploring the direction of atomic deposition technology for many years. The research directions of the research group include selective atomic layer deposition method, preparation and modification of nanoparticle , flexible electronic manufacturing thin film growth process and equipment, photoelectric display, and preparation of photoelectric conversion device.
They also developed theoretical innovations and application expansions in different processes around atomic layer deposition technology. The team revealed the positioning and growth mechanism driven by the precursor bonding energy and the substrate surface adsorption energy, established selective partition judgment criteria, and proposed the crystal surface selective ALD process for the first time, with the accuracy breaking to the atomic level [10-14].
Picture丨Professor Chen Rong's team photo (Source: this team)
theory, facing the manufacturing accuracy requirements of atomic scale, the team further proposed the selective growth mechanism at the crystal surface/site of the same material. By studying the most basic reaction mechanism of the surface, including using quantum mechanics first principle calculation to study surface reactions, including some basic problems such as adsorption barriers, to explain the source of selective deposition.
At present, the research team has also carried out industry-university-research cooperation with related companies in semiconductor manufacturing processes, luminous displays, optical communications and other technologies. Some research results have been transformed, and it is expected to further promote engineering applications. In the future, they will also explore atomic layer deposition to a wider application areas, such as photovoltaic , sensors, optical coating , etc.
At the atomic level, they have new forces, new possibilities, new effects, manufacturing and reproduction problems will be very different.For example, to achieve high-precision nanofabrication, it is necessary to conduct in-depth research on the mechanism of atomic deposition; although characterization technology is booming, there is still a lot of room for improvement in single-atom characterization and manipulation technology; in order to achieve complex nanostructure manufacturing, multi-process coupled for multiple materials is essential. But researchers are actively exploring how to achieve process integration.
In addition to manufacturing films and nanostructures with high precision, accuracy and processing efficiency are also factors that inhibit each other. How to achieve high-precision large-scale manufacturing in emerging applications, such as display panels, solar cell packaging, etc. In order to meet the requirements of accuracy and efficiency in corresponding large-area manufacturing,
proposed a continuous spatial isolation ALD method to achieve rapid manufacturing on nanoscale formats with atomic accuracy, which is also the fastest internationally reported. Large-format atomic accuracy uniform deposition of nano-laminated films is achieved.
integrated circuit manufacturing is a typical representative of micro-nano manufacturing. As semiconductor manufacturing process nodes move to the near-atomic scale, manufacturing accuracy must be at the atomic level. Using atoms as the basic construction of "building blocks" units is built. Building in a bottom-up way is a long-term dream and is considered to be the "ultimate solution in the field of nano-manufacturing."
Reference:
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