Process for obtaining porous semiconductor structures

The invention relates to the technology of semiconductor production, in particular to the processes for obtaining porous semiconductor structures.

The process of obtaining porous semiconductors is known by anodizing a semiconductor substrate coated with an open-layer layer [1]. The porosity degree, the pore directions and the pore distribution in the porous semiconductor are controlled by the electrochemical anodizing parameters.

It is known the process of obtaining the porous layers by anodizing, in which the degree of porosity, the pore dimensions and the pore distribution are controlled by forming on the surface of the material the starting points of the anodization [2]. These points are formed by applying pressure, focused ion beam, or using atomic force microscope (AFM) or tunneling microscope (STM). '

These procedures allow pore density steering in the transverse direction of the pore propagation direction. The disadvantage of these procedures is the impossibility of directing the pore density in the direction of pore propagation.

The problem of the invention consists in obtaining the porous semiconductor with longitudinal gradient of pore density.

The essence of the invention is that the surface of the semiconductor is deposited, the uncoated regions are implanted with high energy ions, then the mask is removed, and the surface of the semiconductor is subjected to electrochemical corrosion. The novelty is that, before corrosion, a layer of photoresist material is deposited on the surface of the semiconductor.

The result of the invention consists in obtaining the porous semiconductor with longitudinal gradient of the pore density, which is determined by the configuration of the semi-insulating regions.

The invention is explained by the illustrations in Figures 1 and 2, which represent:

Fig. 1. Schematic illustration of the process of forming the porous semiconductor with longitudinal gradient of pore density.

Fig. 2. SEM image of the section of a porous semiconductor with a longitudinal gradient of pore density.

Example of carrying out the invention:

Surface area of ​​an n-inP plate with orientation (100) and the concentration of electrons n = 10¹⁷ cm '³ (1) it is covered with a metal frame (2) in which windows (3) of triangular or circular fonn are opened.

The metal mask implants FT ions (4) with 3 MeV energy at dose 10¹³ cm '². Implantation in these conditions leads to the formation in the n-InP semiconductor plate of some insulating regions, the shape of which is determined by the shape of the metal grating.

Subsequently the metallic mask is removed and the entire surface of the n-InP plate in front of the face (5) is covered with a layer of photoresist SU-8, the anodizing electrical contract being formed on the surface opposite the face (5).

The plate is subsequently subjected to anodization in an HCL / H solution₂Keeping the current in the electrochemical circuit at 200 mA / cm². Anodization in these conditions leads to the formation of pores on the n-InP semiconductor plate, which propagates in the direction perpendicular to the beam (5). Because the propagation of pores in the semi-insulating regions of the platelet is impossible, the pores bypass these regions, which leads to the increase of the pore density between the semi-insulating regions.

As a result, a porous semiconductor with a pore density gradient in the pore propagation direction is shown in Fig. 2. This gradient is determined by the shape and topography of the semi-insulating regions, which, in turn, are determined by the topography of the metal grating through which the high-energy ions are implanted.

MD 2714 G2 2005.02.28 (57) Claim: