CS200046B1 - Method of showing-up of planar diffusion structure no the silicon surface - Google Patents

Description

The invention relates to a process for visualizing a plenum diffusion structure on a silicon surface in the course of an elective diffusion of a dopant from a gaseous mixture of bound chlorine-containing compounds into a silicon oxide surface.

The prior art method for contacting structures uses resolution by etching silicon in an acidic environment with a mixture of acids comprising HPF and nitric acid HNO 3 via a resist mask. Etching creates a protrusion structure that is retained even after diffusion and is used to align the contact masks. The disadvantage of this procedure is that / a · a sufficiently thick layer of silicon (3 to 5 µm for the ground surface) must be etched for good visibility of the surface structure. Another method used is the so-called reoxidation of the silicon surface, where the visibility of the structure occurs as follows. First, oxidation, masking and etching of the oxide through the resist mask are carried out, followed by a second oxidation in which a new oxide layer grows on the plates which have been etched. By applying a mask of the same shape as in the first stage of the process, the plenum dlt fusion structure becomes visible. The disadvantage of this process is the time-consuming double oxidation and masking. It is also known to selectively diffuse from a gaseous mixture of bound phosphorus containing compounds, for example POCly.

The disadvantages of the above-mentioned methods are overcome by the method according to the invention which solves the object

200 046, so that during the last third of the diffusion time a non-oxidizing environment is created in the diffusion space with a maximum content of 0.1% by volume of oxygen 0 ^ ·

The visibility of the sheet-like structure of the semiconductor device according to the invention is carried out in a diffusion operation by adjusting the diffusion reaction conditions using bound chlorine-containing diffusers. As _{a result of the} absence of oxygen in the carrier gas, thermal decomposition produces one of the decomposition products free chlorine which etches silicon. Silicon dioxide passivates silicon from the effects of free chlorine. Due to the etching of silicon, the surface roughness is changed, which, when illuminated in a microscope, appears to change the contrast, acidic bonding, and the melting did not result in a noticeable deep etching and thus removal of the highest doped layer. Another advantage is the greater reproducibility of the process, a more pronounced differentiation of the sheet-like structure, less labor and chemical savings compared to the prior art. ^{And the} technological process of production is simpler.

Exemplary embodiment

Diffusion of phosphorus from liquid phosphorus oxychloride POCly Diffusion takes place for 2 hours at a diffusion temperature of 1230 ° C. The carrier gas has a nitrogen flow of 1 l / mln, 0.1 l / mln of oxygen and is saturated vapors of phosphorus oxychloride. Saturation takes place at a diffusant temperature of 4-15 ° C and a flow rate of 0.1 l / min of nitrogen. For the optical resolution of the diffusion structure, the oxygen flow is stopped at the last hour of diffusion.

After etching the molten glass in hydrofluoric acid, the plate is ready for conventional contacting without further operations.

The process can also be used for diffusion of B, Aa, provided that chlorine-containing diffusers are used, or by adding chlorine, to a flow rate of 1% in the absence of oxygen gas.

Claims (1)

SUBJECT OF THE INVENTION A method of visualizing a plenum diffusion structure on a silicon surface by selectively diffusing impurities from gaseous and mixed chlorine-containing compounds into the silicon oxide surface by thermal decomposition, characterized in that a non-oxidizing environment with a maximum content of 0 is formed in the diffusion space. 1% oxygen Og.