Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Diffusing a dopant
Reexamination Certificate
2002-06-10
2004-02-17
Whitehead, Jr., Carl (Department: 2813)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Diffusing a dopant
C438S675000, C438S684000, C438S960000, C257S003000, C257S774000
Reexamination Certificate
active
06693024
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the semiconductor technology field. More specifically, the present invention relates to a semiconductor component which is integrated in a semiconductor body or chip having a first and a second surface. Connection contacts are arranged at the surfaces for making contact with the semiconductor component.
Such a semiconductor component is, for example, a vertical transistor as it is described in Stengl/Tihanyi: “Leistungs-MOS-FET-Praxis” [Power MOSFETs in Practice], Pflaum Verlag, Munich 1992, page 37. That transistor has a heavily n-doped semiconductor substrate on which a more weakly n-doped epitaxial layer is applied. Arranged in the epitaxial layer are p-doped body zones wherein, in turn, n-doped source zones are arranged. In that component, contact is made with the source and body zones at a front side of the semiconductor body formed by the substrate and the epitaxial layer. The substrate forms a drain zone of the transistor, with which zone contact is made at a rear side of the semiconductor body.
The thickness and the doping of the epitaxial layer which acts as drift zone crucially determine the electrical properties of the known component, in particular the reverse voltage thereof and the on resistance thereof. The substrate on which the epitaxial layer is applied is doped as highly as possible in order to influence the on resistance as little as possible.
The heavily doped substrate essentially serves as a carrier and is required in order to be able to handle, during the fabrication method, a wafer wherein a multiplicity of such transistors are fabricated and from which the chips with the transistors are sawn at the-end of the fabrication method. A wafer having exclusively the thickness of the drift zone which determines the electrical properties is sufficient in theory, but in practice cannot be handled for the fabrication of the transistor since the thickness of the drift zone is usually so small that such a wafer would be completely unstable.
Further generally known vertical semiconductor components with connections at opposite surfaces of a semiconductor body are diodes which, for stability reasons, usually likewise have a substrate which is a good electrical conductor and to which—for example by means of epitaxy—semiconductor layers are applied which form a pn junction and whose doping and dimensions determine the electrical properties of the diode.
In order, on the one hand, to ensure sufficient mechanical stability of the wafer during fabrication, which can only be ensured by means of a certain thickness, and, on the other hand, to minimize the effects of this thickness required for fabrication on the component, further procedures are generally known in addition to the abovementioned possibility of applying epitaxial layers which determine the electrical properties to a substrate which is a good conductor.
Thus, it is generally known to provide a wafer having a doping which satisfies the requirements made of the doping in regions of the semiconductor component, for example the drift zone, and subsequently to thin the wafer in the regions which influence the electrical properties of the component.
Furthermore, it is generally known, if the intention is to dispense with an epitaxy, to use a more weakly doped wafer and to dope the wafer from a rear side by means of a deep diffusion, in order thus to produce a low resistance of the wafer in the regions which only contribute to the mechanical stability, and in order that contact can be made with semiconductor components formed above these regions from the rear side in a low-impedance manner.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method of fabricating a semiconductor component, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a process wherein a wafer wherein a multiplicity of components are fabricated is permitted to have a thickness which suffices for handling the wafer during the fabrication method, and wherein that region of the wafer or of the later chip which does not form an active region of the component has a low electrical resistance.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of fabricating a semiconductor component, which comprises the following steps:
providing a semiconductor body having a first and a second surface;
fabricating a multiplicity of pores in the semiconductor body, the pores proceeding from the first surface, extending into the semiconductor body, and ending below the second surface; and
increasing an electrical conductivity of the semiconductor body in the region of the pores.
In accordance with an added feature of the invention, regions of the semiconductor body that are uncovered in the pores are doped. In addition, diffusion may be carried out after the doping.
In accordance with another feature of the invention, the pores are at least partly filled with an electrically conductive material, such as a metal or a polysilicon.
With the above and other objects in view there is also provided, in accordance with the invention, a semiconductor component, comprising:
a semiconductor body having a first surface and a second surface each having connection contacts;
the semiconductor body having a multiplicity of pores formed therein extending into the semiconductor body, proceeding from the first surface and ending below the second surface, and wherein an electrical conductivity is increased in a region of the pores.
In other words, the novel method for fabricating a semiconductor component provides for a semiconductor body having a first and a second surface to be provided and for a multiplicity of pores to be produced which extend into the semiconductor body proceeding from the first surface and which end below the second surface. The electrical conductivity of the semiconductor body is subsequently increased in the region of the pores. This is done, for example, by indiffusion of dopant atoms into regions of the semiconductor body which are uncovered in the pores, and/or by filling the pores with an electrically conductive material, in particular a metal or polysilicon.
That region of the semiconductor body below the second surface which is not permeated by the pores can be utilized for realizing the active regions of the actual semiconductor components, for example a diode or a transistor. These active regions can be fabricated before the production of the pores or after the production of the pores. The depth to which the pores are introduced into the semiconductor body proceeding from the first surface is coordinated with the thickness of the semiconductor body or of the wafer which forms a multiplicity of the later semiconductor bodies/chips in such a way that a semiconductor layer having a thickness suitable for the realization of the desired component remains between that end of the pores which lies in the semiconductor body and the second surface. In this case, the method according to the invention is suitable in particular in the fabrication of PIN photodiodes.
The values for the penetration of the pores into the semiconductor body lie, for example, in the range of between 50% and 95% of the total thickness of the semiconductor body in the direction of the pores.
Electrically, the semiconductor body whose electrical conductivity has been increased in the region of the pores behaves approximately like a thin substrate which only has the thickness of that layer of the semiconductor body which is not permeated by pores, and with which contact can be made from the second surface of the semiconductor body via the porous region which is a good electrical conductor.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for fabricating a semiconductor component and semiconductor co
Lehmann Volker
Schubert Axel
Jr. Carl Whitehead
Smoot Stephen W.
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