Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Diffusing a dopant
Reexamination Certificate
2002-06-20
2004-09-28
Nhu, David (Department: 2818)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Diffusing a dopant
C438S548000, C438S551000, C438S735000
Reexamination Certificate
active
06797597
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority from prior French Patent Application No. 0108192, filed Jun. 21, 2001, the disclosure of which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a process for treating complementary regions of the surface of a substrate and to a semiconductor product thus obtained by this process. More particularly, the present invention the field of fabricating semiconductor products and its applications lie in particular in the treatment of substrates by different treatment steps on complementary regions of their surfaces.
2. Description of Related Art
The term “substrate” is used to denote a support, which has possibly already received various treatments of varied kinds and intended to receive at least one additional treatment. The surface of this support is in general plane or approximately plane in order to be able to use the usual treatment tools and methods for plane surfaces in the field of the fabrication of semiconductor products. These tools and methods possibly being adapted in the case of surfaces which are not strictly plane, for example using devices for the development of a cylindrical surface.
The term “semiconductor product” is used to denote a substrate intended in its final application to support electronic components. This is therefore in general a semi-finished product appearing in the course of the fabrication of a number of components carried by a single support.
The surface treatments considered by the invention may be of very varied kinds, for example implantation of atomic or ionic species, deposition of chemical species, etching, treatment of the surface using a physical principle, especially by bombardment or irradiation, surface treatment according to a chemical principle, especially by surface reaction or by sensitization, and more. The feature of the surface treatments relating to the invention is the need for direct access to the region of the surface to be treated, possibly access by exposure of this exposed region, access by contact, especially for contacting with a liquid solution, and other surface treatments. One particularly widely used surface treatment is the implantation of arsenic or phosphorus into a silicon substrate in order to impart n-type semiconductor behavior on it, or the implantation of boron or boron fluoride in order to impart p-type semiconductor behavior on it. More generally, the two surface treatments of the regions of the first group of regions and of the second group of regions are, respectively, two treatments of the substrate by implantation of atomic or ionic species so as to create two different dopings.
As a matter of fact, in the above technical field, it is frequently the case to have to apply different treatments to complementary regions of the surface of a substrate. This occurs when a first group of regions has to receive a first surface treatment, while a second group of regions has to receive a second surface treatment, without the first or the second regions being subjected to the effects of the surface treatment intended for the other region.
The expression “groups of complementary regions with respect to the surface portion of the substrate” is understood to mean that this surface portion is divided into two groups of regions so that joining the regions of these two groups of regions reconstitutes the initial surface portion of the substrate in its entirety and without any overlap of parts of regions. The selective exposure of the regions of a group of regions to a surface treatment which is intended for it without the regions of the other group of regions being subjected to the effects of this surface treatment requires placing, on the latter regions, one or more screen layers capable of blocking the effects of the treatment on the substrate surface thus protected. Since the two groups of regions have to receive a respective surface treatment exclusively with respect to the regions of the other group of regions, two steps of depositing screen layers are necessary, successively on the regions of each of the two groups of regions, before the surface treatment intended for this group of regions is applied.
These screen layers must therefore leave exposed the regions that have to receive the effects of the surface treatment which is intended for them. Their depositions must therefore be selective, this selectivity resulting from the use of respective specific masks, which differentiate the regions of one of the two groups of regions with respect to those of the other group of regions. Each mask is positioned with respect to the substrate with a precision of about 0.10 to 0.18 &mgr;m, using identification marks for aligning the mask with respect to the substrate, and with a procedure consisting of several repeated steps of progressively readjusting the position of the mask. According to the existing methods, these operations of positioning the mask are carried out during each deposition of the screen layers, that is to say at least twice in the case considered here of two different surface treatments applied to two groups of complementary regions of the substrate surface.
However, the imprecision in positioning the aforementioned masks prevents the regions of one group of regions being contiguous with regions of the other group of regions, that is to say there is a residual substrate band between the regions of each group of regions which is either not subjected to either the first or the second treatment, or is successively subjected to the effects of both surface treatments. This results, in the first case, in the formation of parts of the surface of the substrate which are not treated, and therefore lost from the standpoint of the fabrication of electronic circuits. Furthermore, a substrate band which is not treated by any of the two surface treatments is in an uncontrolled electrical state which may affect the subsequent operation of the electronic circuits. This is particularly so for a pure silicon substrate when the two surface treatments consist of implantations of doping species defining the electrical behavior of the implanted regions. In the second case, this results in the formation, between regions belonging to different groups of regions, of substrate bands receiving successively both surface treatments. Such regions are also deleterious, for the same reasons as those mentioned above, in particular in the aforementioned case of doping treatments of a pure silicon substrate. Accordingly, a need exists to overcome the problems of a “residual substrate band” and to provide a product and process with little or no “residual substrate band.”
SUMMARY OF THE INVENTION
One object of the present invention is to provide a process which comprises the use of only a single mask for carrying out two different surface treatments intended for separate regions, and therefore comprising only a single operation of positioning the mask with respect to the substrate.
The invention relates more particularly to a process for treating a surface portion of a substrate comprising a first group of regions intended to receive a first surface treatment and a second group of regions intended to receive a second surface treatment different from the first surface treatment, the two groups of regions each comprising at least one region and being mutually complementary with respect to the surface portion, wherein:
a step of selectively protecting the regions of the second group of regions against the effects of the first surface treatment is carried out by the selective deposition of at least one layer formed from first materials on the regions, using a mask which differentiates the regions belonging to the first group of regions from the regions belonging to the second group of regions;
the first surface treatment is applied so that it has an effect only on the regions of the first group of regions;
a step of selectively protecting the regions of the fir
Coronel Phillipe
Ferreira Paul
Gibbons Jon A.
STMicroelectronics S.A.
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