Semiconductor device manufacturing: process – Radiation or energy treatment modifying properties of...
Reexamination Certificate
1999-12-20
2001-10-09
Le, Vu A. (Department: 2824)
Semiconductor device manufacturing: process
Radiation or energy treatment modifying properties of...
C438S799000, C219S413000
Reexamination Certificate
active
06300256
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for producing electrically conductive passages in semiconductor components and to a device for implementing the process.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,159,215 disclosed a process for penetrating a semi-conducting body of a semiconductor component consisting of doped silicon, germanium, or the like whereby, the semiconductor component has opposite-lying outer surfaces, with an alloy with aluminum as the carrier material and phosphorus, arsenic, or antimony as the doping by means of temperature gradient zone melting. The semiconductor component is positioned in a metal vapor chamber and an aluminum-antimony layer with a layer thickness of 0.5 &mgr;m to 25 &mgr;m is applied to one of the two opposite-lying surfaces of the semiconductor component. By means of photo-lithography, the migration areas are fixed and the thus prepared component is positioned in a thermo-migration device. Through a temperature gradient of around 50° C. between the warmer base surface and the cooler upper surface applied to the semi-conducting body over a sufficient period of time, the alloy penetrates the semiconducting body.
Subsequently, the alloy areas on the base surface of the semiconductor component are etched away or grinded off, and the channels of re-crystallized semiconductor material and detached metal produced by means of thermo-migration remain.
Channels of this nature running from one outer surface to the opposite-lying outer surface of a semiconductor component are used in particular with SMD (Surface Mounted Devices) components, which are formed in such a way that the contact points of both electrodes can be positioned on one outer surface (of the rear side) of the component. A component of this nature can be connected with its rear side to a circuit board provided with suitable contact areas, without the need for additional wires or other connecting components.
A particular field of application is opto-electronic sensor components, i.e. radiation receptors that convert electro-magnetic radiation energy (photons) into electric signals and which are of great significance in measuring technology. For example, in position measuring systems, such as length and angle measuring systems, (of the incremental or absolute type), several radiation receptors (especially photo-elements) are positioned behind a grid structure.
Radiation receptors of this nature are, as a rule, formed as blocking layer photo detectors. They contain a PN, PIN, MS or MOS junction, in which the conversion of electro-magnetic radiation energy into an electric signal takes place by means of the photo blocking layer effect. To be able to measure and evaluate an electric signal, a radiation receptor should be provided with electric contacts and connected to a suitable electric switch. This integration into an electric switch frequently occurs on a circuit board, whereby receptors are preferably formed as SMD components.
For the purpose of producing an electrically conductive connection from one surface to the opposite-lying outer surface of a semi-conducting body, a cylindrical semi-conducting channel of the p-type is, for example, produced between the p-conducting layer and the rear-side upper surface of the semi-conductor component, whereby this channel preferably has a diameter of 30 &mgr;m to 100 &mgr;m and, in addition to other connection processes, can be produced by means of thermo-migration.
The principle of thermo-migration is based upon the fact that the solubility of metal doping substances in semi-conducting materials, e.g. silicon, is temperature-dependent and increases with increasing temperature. If between the two opposite-lying outer surfaces of a sufficiently heated semi-conductor component a temperature gradient is produced and a suitable metal doping substance (e.g. aluminum for p-doping of n-conducting areas) is applied to the cooler outer surface of the component, the metal doping substance migrates to the opposite-lying warmer outer surface of the semi-conductor component. Through corresponding structuring of the cooler outer surface, to which the doping substance is applied (e.g. with the help of oxide layers), the formation of such channels can be achieved as desired.
U.S. Pat. No. 4,221,956 and U.S. Pat. No. 4,224,504 disclosed the carrying out of the migration process in a closed chamber and the placing of the semi-conductor on webs with a fixed distance in relation to the cooling device.
WO 83 03710 disclosed a process for carrying out the thermo-migration process on semi-conductors, whereby the correspondingly prepared semi-conductor is placed with one outer surface on an essentially even outer surface of a heat source, so that it lies on the outer surface of the heat source. The semi-conductor is heated, so that a temperature difference between the two outer surfaces of the semi-conductor is formed. Droplets of material with opposing conduction applied to the semiconductor thereby travel through the semi-conductor, and form conducting connections between the two outer surfaces. Subsequently, the heating element is cooled and the semi-conductor is removed. Through the direct contact between the semi-conductor and the heat source, a high temperature gradient is produced in the semi-conductor and thus the process is accelerated. A disadvantage of the state of technology is that even temperature guiding of this nature is barely possible.
It is an object of the present invention that during the production of semiconductor components by means of thermo-migration, the adjustment of the outer surface temperature of the semiconductor during the process be guided so that a sure penetration of conductive passage channels through the semi-conductor wafer with fixed pn-passages is possible in a minimum time, whereby the doping of the semi-conductor components is not influenced as a result of the heating of the semiconductor wafer, and whereby the form of the semi-conductor wafer is not changed. In addition, interactions between the outer surface of the heat source and/or the cooling device and the wafer are intended to be avoided.
SUMMARY OF THE INVENTION
The outer surface temperature of the semi-conductor is measured on at least one temperature measurement point and this temperature forms the basis for controlling the total efficiency of the heat input into the semi-conductor and/or the efficiency distribution of the heat input over the upper surface of the semi-conductor to be heated. This control is achieved through changing the distances between the semi-conductor and the heating and/or the cooling element.
Through targeted temperature control over the time period of the thermo-migration process and over the entire area of a semi-conductor wafer, the process according to the invention ensures penetration of the semi-conducting bodies of the semi-conductor components positioned on the semi-conductor wafer. This is achieved with the simultaneous exclusion of impurities during the process and in minimum time. Furthermore, the method ensures that the doping of the semi-conductor components is not influenced as a result of the heating of the semi-conductor wafer and that the form of the semi-conductor wafer is not influenced for example, through buckling, as a result of the heat radiation affecting the semi-conductor wafer.
In a preferred embodiment of the invention the semi-conductor is positioned in a closed system preferably filled with an inert gas that is a good heat conductor. By placing the semi-conductor in a closed system filled with an inert gas, impurities are avoided on the semi-conductor. Furthermore, the heat flow for both heating one outer surface of the semi-conductor and cooling the other outer surface are optimized. It is thereby preferable to use helium in the laminar flow area at a pressure of 0.1 mbar to 30 mbar.
Furthermore, the effectiveness and controllability of the heat distribution on the semi-conductor is improved in that the outer surfaces of the semi-conductor are positioned in areas that are separated from on
Arnold Rene
Kriegel Bernd
Kudella Frank
Christie Parker & Hale LLP
Dr. Johannes Heidenhain GmbH
Le Vu A.
Smith Bradley
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