The microstructure (patterning) of silicon is one of the key steps in the manufacture of integrated circuits (IC), which is the cornerstone of modern electronics. Microstructure is achieved through a series of processes, including photolithography to produce a template (mask) with a desired structure, etching under controlled conditions to remove materials, and/or ion implantation or diffusion through the mask. ) introducing foreign atoms such as boron or phosphorus into silicon. A typical microstructure process uses a photolithography mask method to generate arbitrary patterns on a silicon substrate from top to bottom.

Researchers at the Leibniz-Dresden Institute of Polymerization in Germany reported a new bottom-up fabrication method of microstructures, which can realize the patterning of N-doped silicon substrates without using etching masks or templates during the etching process. On the contrary, the structured process developed here includes simple alkaline etching under illumination, and it is changed from 0.25 to 1? Remote control of p-doped micron-scale implantation under uniform n-doped layer with depth of m The microstructure of this process can be realized because the embedded implant acts as a micro photovoltaic cell under illumination, generating an electron flow and increasing the negative surface charge in the area above the implant. The locally increased surface charge leads to the local protection of the natural silicon oxide layer from alkaline etching, which ultimately leads to the microstructure of the substrate. In this way, a substrate with a thick and uniform N-doped silicon layer on its top can be constructed, thereby reducing the need for expensive and time-consuming photolithography steps. Related papers were published in Advanced Functional Materials.

Paper link:

https://doi . org/ 10. 1002/adfm . 202 100 105

Figure 1. Schematic diagram of initial substrate for selective etching experiment

Figure 2. (a, c, e) topographic map of atomic force microscope

Figure 3. The schematic diagram of the mechanism responsible for self-replication proposed in this paper.

Figure 4. Atomic force microscope images show the time-related results of selective etching of implants on samples buried under 250nm epitaxial silicon.

Figure 5. Illustration of an example structure herein

To sum up, a new microstructure process is developed in this paper, which is used to bury the P-doped implantation region in the internal structure of N-doped silicon substrate. This process includes simple alkaline etching under illumination and leads to the replication of buried patterns. The microstructure appears because the embedded implantation structure provides remote control in the etching process, and acts as a micro photovoltaic cell, and its irradiation generates a photogenerated electron flux from the embedded implantation to the surface. Electrons accumulated on the surface increase the surface negative charge in the area above these implants. The local increase of surface charge leads to the protection of natural silicon oxide layer from alkaline corrosion in the area buried above the implant, which is the reason for silicon corrosion selectivity. By studying the mechanism behind the development process, this paper holds that this method is bottom-up rather than top-down (text: SSC)