CA1162326A - Forming impurity regions in semiconductor bodies by high energy ion irradiation, and semiconductor devices made thereby - Google Patents
Forming impurity regions in semiconductor bodies by high energy ion irradiation, and semiconductor devices made therebyInfo
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- CA1162326A CA1162326A CA000379841A CA379841A CA1162326A CA 1162326 A CA1162326 A CA 1162326A CA 000379841 A CA000379841 A CA 000379841A CA 379841 A CA379841 A CA 379841A CA 1162326 A CA1162326 A CA 1162326A
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- semiconductor body
- impurity region
- forming
- ion beam
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
- H01J37/302—Controlling tubes by external information, e.g. programme control
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
- H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
- H01J37/3171—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation for ion implantation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
- H01L21/26506—Bombardment with radiation with high-energy radiation producing ion implantation in group IV semiconductors
- H01L21/26513—Bombardment with radiation with high-energy radiation producing ion implantation in group IV semiconductors of electrically active species
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
- H01L21/2658—Bombardment with radiation with high-energy radiation producing ion implantation of a molecular ion, e.g. decaborane
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
- H01L21/266—Bombardment with radiation with high-energy radiation producing ion implantation using masks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/74—Making of localized buried regions, e.g. buried collector layers, internal connections substrate contacts
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/04—Means for controlling the discharge
- H01J2237/047—Changing particle velocity
- H01J2237/0475—Changing particle velocity decelerating
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/05—Arrangements for energy or mass analysis
- H01J2237/057—Energy or mass filtering
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/30—Electron or ion beam tubes for processing objects
- H01J2237/304—Controlling tubes
- H01J2237/30455—Correction during exposure
- H01J2237/30461—Correction during exposure pre-calculated
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/30—Electron or ion beam tubes for processing objects
- H01J2237/317—Processing objects on a microscale
- H01J2237/31701—Ion implantation
- H01J2237/31706—Ion implantation characterised by the area treated
- H01J2237/3171—Ion implantation characterised by the area treated patterned
- H01J2237/31711—Ion implantation characterised by the area treated patterned using mask
Abstract
22 46,767 ABSTRACT OF THE DISCLOSURE
Impurity regions and preferably buried impurity regions are formed of desired thicknesses and concentra-tion gradients in semiconductor bodies at a given distance from a selected surface of the body. A high energy ion beam of greater than 1.0 Mev. containing ions of an impur-ity to form a desired impurity region in the semiconductor body is formed to penetrate the body through the selected surface to a distance sufficient to form the impurity region. A beam modifier is formed of a given material and non-uniform shape to modify the ion energies on transmis-sion throughout to form the impurity region of a desired thickness and concentration gradient at a given distance from the selected surface of the semiconductor body on irradiation of the semiconductor body through the selected surface with the transmitted high energy ion beam. The semiconductor body is then positioned to be irradiated with the high energy ion beam through the beam modifier, and the semiconductor body is so irradiated until the impurity region of the desired thickness and concentration gradient is formed in the body at a desired distance from the selected surface. Preferably, there is a predeter-mined relative movement between the beam modifier and semiconductor body during irradiation to modulate the ion beam as desired to form the impurity region. The semicon-ductor body is also preferably annealed after irradiation to remove detrimental electrical characteristics caused by the irradiation from the semiconductor body,
Impurity regions and preferably buried impurity regions are formed of desired thicknesses and concentra-tion gradients in semiconductor bodies at a given distance from a selected surface of the body. A high energy ion beam of greater than 1.0 Mev. containing ions of an impur-ity to form a desired impurity region in the semiconductor body is formed to penetrate the body through the selected surface to a distance sufficient to form the impurity region. A beam modifier is formed of a given material and non-uniform shape to modify the ion energies on transmis-sion throughout to form the impurity region of a desired thickness and concentration gradient at a given distance from the selected surface of the semiconductor body on irradiation of the semiconductor body through the selected surface with the transmitted high energy ion beam. The semiconductor body is then positioned to be irradiated with the high energy ion beam through the beam modifier, and the semiconductor body is so irradiated until the impurity region of the desired thickness and concentration gradient is formed in the body at a desired distance from the selected surface. Preferably, there is a predeter-mined relative movement between the beam modifier and semiconductor body during irradiation to modulate the ion beam as desired to form the impurity region. The semicon-ductor body is also preferably annealed after irradiation to remove detrimental electrical characteristics caused by the irradiation from the semiconductor body,
Description
23~
1 46,767 FORMING IMPURITY REGIONS IN SEMICONDUCTOR
BODIES BY HIGH ENERGY ION IRRADIATION, AND SEMICONDUCTOR DEVICES MADE THEREBY
BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to semiconductor devices and particularly semiconductor devices having buried impurity regions Description of the Prior Art:
Semiconductor devices generally-require impurity regions in them to impart electrical characteristics.
These impurity regions are formed typically by diffusion of a selected impurity into the semiconductor body or the inclusion of the impurity in the semiconductor body during its formation, e.g., by epitaxial growth. Impurities usually used for such purpose are phosphorus, antimony, arsenic, boron, gallium, aluminum, and gold.
Formation of the impurity regions in semicon-ductor devices by diffusion has inherent limitations. The concentration of the impurity at the surface of the semi-conductor body through which it is diffused is normally fixed by the saturation solubility concentration of the impurity in the semiconductor material. This results in high impurity concentration at the surface of the semi-conductor body which both chemically and electrically degrade the surface portions of the body In addition, the thickness of the impurity region in the semiconductor body and the concentration gradient is fixed by th~ sur-face concentration, diffusion rate, temperature and time
1 46,767 FORMING IMPURITY REGIONS IN SEMICONDUCTOR
BODIES BY HIGH ENERGY ION IRRADIATION, AND SEMICONDUCTOR DEVICES MADE THEREBY
BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to semiconductor devices and particularly semiconductor devices having buried impurity regions Description of the Prior Art:
Semiconductor devices generally-require impurity regions in them to impart electrical characteristics.
These impurity regions are formed typically by diffusion of a selected impurity into the semiconductor body or the inclusion of the impurity in the semiconductor body during its formation, e.g., by epitaxial growth. Impurities usually used for such purpose are phosphorus, antimony, arsenic, boron, gallium, aluminum, and gold.
Formation of the impurity regions in semicon-ductor devices by diffusion has inherent limitations. The concentration of the impurity at the surface of the semi-conductor body through which it is diffused is normally fixed by the saturation solubility concentration of the impurity in the semiconductor material. This results in high impurity concentration at the surface of the semi-conductor body which both chemically and electrically degrade the surface portions of the body In addition, the thickness of the impurity region in the semiconductor body and the concentration gradient is fixed by th~ sur-face concentration, diffusion rate, temperature and time
2 46,767 of diffusion. The impurity region is thus restricted in its thickness and profile gradient and oftentimes requires considerable time to make. Additionally, the thickness of the impurity regions are often difficult to control with precision and may require simultaneous or successive diffusion of more than one impurity, e.g., boron and aluminum, to form the impurity region of the desired electrical characteristics.
Forming the impurity region by epitaxial growth similarly has inherent limitations. Epitaxial growths require careful preparation of the substrate, whether it be semiconductor or insulator, and careful control of the deposition system during the growth. Even with careful control, epitaxial semiconductor bodies are typically limited in their electrical characteristics by the pres-ence of fugitive impurities of low concentrations which somehow find their way into the system. Also, epitaxial growths are in general limited to rather narrow thickness-es which makes the application of that technique unuseful in making certain semiconductor devices, such as high-power devices Another technique used for forming shallow impurity regions of high concentration near the surface of semiconductor bodies is ion implantation. See, e.g., Ion Beams by Wilson and Rewer (1973), and Ion Implantation _ Semiconductors by Mayer, Eriksson and Davies (1970). In this technique, a low energy ion beam of generally about 20~ to 4Q0 Kev. was formed of ions of the impurity desired in the impurity region, and a major surface of semicon-ductor body bombarded with the ion beam. An impurityregion was thus formed adjacent the surface of the semi-conductor body of a few microns in thickness of high, fix concentration gradient.
Ion implantation has not been considered to be useful in making thick impurity regions penetrating beyond a few microns into the semiconductor body or impurity regions of controllable concentration gradient. The crucial limitation has been that the ion beam generators 1 16~326
Forming the impurity region by epitaxial growth similarly has inherent limitations. Epitaxial growths require careful preparation of the substrate, whether it be semiconductor or insulator, and careful control of the deposition system during the growth. Even with careful control, epitaxial semiconductor bodies are typically limited in their electrical characteristics by the pres-ence of fugitive impurities of low concentrations which somehow find their way into the system. Also, epitaxial growths are in general limited to rather narrow thickness-es which makes the application of that technique unuseful in making certain semiconductor devices, such as high-power devices Another technique used for forming shallow impurity regions of high concentration near the surface of semiconductor bodies is ion implantation. See, e.g., Ion Beams by Wilson and Rewer (1973), and Ion Implantation _ Semiconductors by Mayer, Eriksson and Davies (1970). In this technique, a low energy ion beam of generally about 20~ to 4Q0 Kev. was formed of ions of the impurity desired in the impurity region, and a major surface of semicon-ductor body bombarded with the ion beam. An impurityregion was thus formed adjacent the surface of the semi-conductor body of a few microns in thickness of high, fix concentration gradient.
Ion implantation has not been considered to be useful in making thick impurity regions penetrating beyond a few microns into the semiconductor body or impurity regions of controllable concentration gradient. The crucial limitation has been that the ion beam generators 1 16~326
3 46,767 available have produced monoenergetic ion beams which produced very narrow impurity regions of use at the sur-face of the semiconductor body. The thickness of the impurity region in the semiconductor body had been extend-ed by pivotally moving the body during ion implantation,but even with this technique, the thickness of the impur-ity region was typically less than 5 microns and of uncon-trolled impurity concentration gradient.
It has been known to interpose a scattering foil of metal, e.g., aluminum, of about one-half a mil in thickness between the ion beam source and semiconductor body. But these foils were necessarily uniform thickness to provide the desired scattering of the ion beam to provide a substantially uniform dosage over a large area of the semiconductor body. It was not conceived to shape a material of low scattering properties to modify and modulate the beam energy to tailor an impurity region of large thickness and variable concentration gradient.
The problems are compounded when it is desired to form a buried impurity region within a semiconductor body. ~ A buried impurity region is one in the interior of the body which has a high impurity concentration relative to the adjacent impurity region or regions between it and a working surface of the semiconductor device. Generally, such buried impurity regions are formed by a series of epitaxial growths or a combination of diffusion and epi-taxial growth. See, e.g., U.S. Patent No. 3,237,042, assigned to the same assignee as the present application.
These techniques are difficult and require considerable time to perform, and even then the yields of devices are relatively low. The formation of such buried impurity regions is also compounded by the difficulty in controll^
ing autodoping of the lower concentration impurity regions over the buried impurity regions and in turn the diffi-culty in controlling the thickness and concentation grad-ient of both the buried impurity region and the impurity region adjacent to it.
The present invention overcomes all of these 1 ~62326
It has been known to interpose a scattering foil of metal, e.g., aluminum, of about one-half a mil in thickness between the ion beam source and semiconductor body. But these foils were necessarily uniform thickness to provide the desired scattering of the ion beam to provide a substantially uniform dosage over a large area of the semiconductor body. It was not conceived to shape a material of low scattering properties to modify and modulate the beam energy to tailor an impurity region of large thickness and variable concentration gradient.
The problems are compounded when it is desired to form a buried impurity region within a semiconductor body. ~ A buried impurity region is one in the interior of the body which has a high impurity concentration relative to the adjacent impurity region or regions between it and a working surface of the semiconductor device. Generally, such buried impurity regions are formed by a series of epitaxial growths or a combination of diffusion and epi-taxial growth. See, e.g., U.S. Patent No. 3,237,042, assigned to the same assignee as the present application.
These techniques are difficult and require considerable time to perform, and even then the yields of devices are relatively low. The formation of such buried impurity regions is also compounded by the difficulty in controll^
ing autodoping of the lower concentration impurity regions over the buried impurity regions and in turn the diffi-culty in controlling the thickness and concentation grad-ient of both the buried impurity region and the impurity region adjacent to it.
The present invention overcomes all of these 1 ~62326
4 46,767 difficulties and disadvantages. It provides a way of rapidly forming impurity regions generally, and buried impurity regions in particular in a semiconductor body with a high degree of precision. Manufacturing yields can be greatly increased with accompanying marked decrease in production costs. Further, it enables the making of semiconductor devices heretofore not possible because of the restrictions on the concentration gradient by the inherent limitations of the formation techniques. The present invention provides a flexibility in forming con-centration gradients of impurity regions and the position-ing of impurity regions in the semiconductor body previ-ously unavailable.
SUMMARY OF THE INVENTION
The present invention is a method of forming an impurity region or regions in a semiconductor body by high energy ion irradiation. An ion beam is formed containing ions of an impurity desired to form an impurity region or regions in a selected semiconductor body. The ion beam is Z0 of such enérgy that it can penetrate the semiconductor body through a selected surface to a depth greater than the maximum depth of a desired impurity region from the selected surface.
A beam modifier is formed of a given material in a non-uniform shape to modify the energy of the radiation beam on transmission therethrough to form a transmitted `energy beam capable of forming an impurity region of a desired thickness and impurity gradient in the semicon-ductor body a given distance from a selected surface through which the semiconductor body is irradiated.
Preferably the beam modifier is made of a material such as aluminum, beryllium or radiation-resistant silicone or epoxy to reduce scattering ~nd to provide good resolution for the transmitted ion beam.
The impurity region is formed by positioning the selected surface of the semiconductor body to be exposed to the ion beam through the beam modifier. The beam transmitted through the beam modifier thus penetrates the ~ 18232~
46,767 semiconductor body through the selec~ed surface and forms the desired impurity region within the body. The thick-ness of the impurity region (i.e., its distance along the transmission direction of the ion beam) and its distance from the selected surface are accurately controlled by the energ~ of the ion beam and thickness of the beam modifier.
The impurity concentration profile of the impurity region is controlled with precision by the contour of the beam modifier and the predetermined relative movement between the beam ~odifier and the semiconductor body during dop-ing.
The present invention is particularly useful in preparing semicondùctor devices where buried regions and regions of previously unusual doping concentration gradi-ents are desired. In some embodiments the semiconductorbody may be preferably annealed after the doping operation to reduce the damage to the crystalline lattice of the semiconductor body.
Other details, objects and advantages of the 2~ invention become apparent as the following description of the presently preferred embodiments and presently prefer-red methods of practicing the same proceeds.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, the presently preferred embodiments of the invention and the presently preferred methods of practicing the invention are illu-strated in which:
Figure 1 is an elevational view in cross-section of a transistor with a buried collector region made in accordance with the present invention;
Fig. 2 is an elevational view in cross-section of a second transistor with a buried collector region made in accordance with the present invention;
Fig. 3 is an elevational view in cross-section of an integrated circuit made in accordance with the present invention;
Fig. 4 is an elevational view in cross-section of a semiconductor body wherein an impurity region is t 162326 6 46,767 formed in accordance with the present invention;
Fig. 5 is an elevational view in cross-section of a second semiconductor body in which an impurity region is formed in accordance with the present invention; and Fig. 6 is an elevational view in cross-section of a third semiconductor body formed in accordance with the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Fig. 1, a transistor is made with a buried collector region utilizing the present invention.
The transistor is formed in semiconductor body 10 having opposed major surfaces 11 and 12, which has been attached to substrate 13 at major surface 12 by alloying, electro-- static technique, epitaxial growth or some other means.
The semiconductor body is doped during manufacture to the desired impurity concentration for the collector region, e.g., 1 x 1013 to 1 x 1014 per cubic centimeter. Sub-strate 13 is preferably an insulator material appropriate for the particular application.
Base region 15 and emitter region 14 are formed by sequential diffusions of impurities of opposite conduc-tivity type, e.g., gallium and phosphorus, through major surface 11 using standard oxide masking and photoetch techniques. The impurity utilized in forming base region 14 is also of opposite conductivity type from the impuri-ties formed in the semiconductor body during its manufac-ture. PN junctions 17 and 18 are thus formed in the semiconductor body between emitter and base regions 14 and 15 and collector and base regions 15 and 16. The impurity concentration of base region 15 typically ranges from 1 x 1015 to 1 x 1017 per cubic centimeter, and the impur-ity concentration of emitter region typically ranges from 1 x 1017 to 1 x 1019 per cubic centimeter. Collector region 12 is formed of the impurity concentration in the remaining part of semiconductor body 10 using the irradia-tion technique hereinafter described.
Buried collector region 19 is then formed in the semiconductor body at a depth to provide the desired width 7 46,767 of collector region 16. The buried collector region is a conductor electrically connecting the transistor to anoth-er electrical component preferably in the same semicon-ductor body.
To forming collector region 19 an ion source is provided which is capable of emitting particles with molecular weight of at least one (1) to form ion beam 20.
Ion beam 20 is of an energy capable of penetrating semi-conductor body 10 through selected surface 11 to a depth greater than the desired depth of buried collector region 19 in the body.
The ion source may be any conveniently available source which emits ions of an impurity desired to form buried collector region with sufficient energy to pene-trate body 10 to at least the desired depth of the buriedcollector region. Preferably the ion source is a Van de Graaff accelerator emitting ions of boron because such particles are relatively inexpensive to accelerate to energy sufficient to penetrate the semi,conductor body to the desired depth. Other ions suitable to form impurities in semiconductor materials, such as phosphorus or alumi-num, may be utilized; however, ions having a molecular weight higher than 16 are presently impractical because available ion sources, e.g., Van de Graaff accelerators, do not generate high enough energy to cause penetration of such higher molecular weight particles into material to a significant depth. In any event, the ion selected must be of the same conductivity type as that utilized for col-lector region 16 to provide the desired electrical charac-teristics to the buried collector region.
The ion source is also preferably a monoenerget-ic source such as conventionally produced by Van de Graaff accelerators to permit the buried collector region to be more precisely controlled in thickness, width and dosage gradient. For this reason, higher molecular particles such as phosphorus or aluminum ions may be more useful in certain applications where higher resolution is desired for the impurity region because such ions have a narrower 1 ~62326 8 46,767 half-width to the defect generation distribution produced in semiconductor materials. The narrower the half-width the more precisely the impurity region desired for buried collector region 19 can be positioned in semiconductor body 10 and the more precisely the concentration and concentration grad~ent can be controlled.
Additionally, it should be observed that it may be appropriate in certain applications to use a non-mono-energetic radiation source or to modify a monoenergetic source so that it is not monoenergetic. For example, it may be more desirable to have a more uniform particle distribution over the area of semiconductor body 10 at a sacrifice of resolution of the depth of the impurity region. This can be done by utilization of a scattering foil (not shown) in the path of the ion beam 20 between the ion source and semiconductor body 10. Generally, however, a monoenergetic radiation source is preferred to provide the narrowest half-width for the defect generation distribution of the beam in the material and in turn the highest possible resolution for the impurity region formed in the semiconductor body.
Positioned between the ion beam 20 and semicon-ductor body 10 is beam modifier 21 Beam modifier 21 is selected of a material to allow transmission of ion beam 20 through it normally without substantially scattering of the beam, Although in some circumstances it may be ap-propriate to incorporate a scattering foil with beam modifier 21, typically it is desired that the transmitted ion beam 22 not be dispersed due to variations in the thickness of modifier 21. This improves the accuracy of the placement and resolution of the impurity region. Beam modifier 21 is of a material which modifies the energy of the transmitted ion beam, but is preferably selected from a material which does not modify the energy of the beam greatly per unit thickness. This permits the accuracy of the thickness and dosage gradient of the impurity region to be more precisely controlled without critically con-trolling dimensional tolerances of beam modifier 21 t 162326 9 46,767 Examples of such materials are those composed of low atomic number elements such as aluminum or beryllium. If the ion beam used not penetrated too deeply into semicon-ductor body, radiation resistance silicone and epoxy may be used. Also, the beam modifier is preferably made of a material that is easily worked to the desired shape as hereinafter explained.
Preferably semiconductor body 10 and beam modi-fier 21 are moved relative to each other through a prede-termined motion during the doping. This can be done byany suitable means. Beam modifier 21 is preferably oscil-lated normal to the path of ion beam 20 parallel to major surface 11 of semiconductor body 10 as indicated in Fig.
1. Alternatively, beam modifier 21 could be rotated or otherwise moved relative to semiconductor body 10, or semiconductor body 10 can be moved relative to beam modi-fier 21 in a predetermined path.
Given the ion source and the composition of the beam modifier 21, the thickness and impurity concentration gradient of the impurity region to be formed in semicon-ductor~body 10 becomes a function of the shape of the beam modifier 21 and the relative motion between the semicon-ductor body and the beam modifier doping. Typically the relative movement between the beam modifier and the body is fixed so that the thickness and impurity gradient of the impurity region becomes a function solely of the shape of the beam modifier.
One can therefore shape the beam modifier to correspond to any desired width and impurity concentration gradient desired for the impurity region and any desired distance between major surface 11 and impurity region 19 in the semiconductor body. To understand the relation, consider that the energy spectrum of ion beam 22 after transmission through beam modifier 21 corresponding to the desired positioning, width and impurity concentration gradient desired for buried collector impurity region 19 is represented by the mathematical function dn(Et)/dEt =
h(Et). Further, consider that the beam modifier shape , l 162326 46,767 corresponding to this energy spectrum is represented by the mathematical function F(~) = X, where X is the thick-ness of the modifier and ~ is the distance along the modifier from a coordinate. Also consider that ~ is a mathematical function of X, F(X).
Now consider the energy of transmitted ion beam 22 at a point at major surface 11. The ion beam directed at this point must pass through a thickness XQ of beam modifier 21 which will reduce the energy of the beam from E to E~. The flux density at the point on major surface 11 is 0 in ions per second, stated mathematically as d = dn/dt. Since beam modifier 21 moves horizontally as shown in Fig. 1 with a speed V = d ~ dt, the number of ions which strike the selected point on major surface 11 in a time dt is defined as dn = ~dt - 0/V~ d~. Since ~ = f~x) and d~ = df(x)/dx dx, dn = ~/V~ df(x)/dx.dx.
The variable x is the thickness of beam modifier 21 through which the ion beam passes to the point on major surface 11 at any moment in time and is functionally related to the energy of the ions emerging from the beam modifier in ion beam 22. Suppose that R (the range of the ions) and E (the energy of the ions) are related by the mathematical function R = g(E). The range of the incoming ion in beam 20 to the beam modifier is Rp - g(Ep), and the range of the exiting ions in beam 22 is R = g(E). The thickness of beam modifier 21 can be expressed as a mathe-matical function of the energy of the ion beam as follows:
x = Rp - R = g(Ep) - g(E).
Substituting this x in the preceding equation the ion reaching the selected point on major surface 11 can be stated as:
dn = d, df (gdEp(E)- g(E)~ . ~ , dE
The thickness of beam modifier 21 can thus be expressed mathematically in terms of the transmitted energy spectrum of the ion beam as follows:
-~ -` 1 16232~
11 46,767 df (g(Ep)E) g(E)) = ~ a~ ( ~ ) For complex energy spectra, dn/dE, the shape of the modifier 21 can be calculated by computer. For more simple spectra the shape can be determined by simple hand calculation.
For example, consider where buried collector region 19 is to be rectangular with a constant impurity concentration gradient across its thickness x and area.
dn/dE = K (a constant) and R = g(E) = E/m, i.e., the range dependence on ion energy is linear with mass. The mathe-matical function shown above reduces to:
~Ep E~
df ~ m m) V K dE
d (E) 0 (m) Substituting x = Ep/m - E/m, the function fur-ther reduces to:
15 ~ = VK
x ~
The general solution to this equation is:
f(x) = V~_ mx + b = 1 Stated another way for x = F(R):
_ d + b~
x - VK VK m 20The constant b can be obtained by letting x be the thickness X (at ~ = 0) for the lowest energy in the spectrum:
b = X~ V~_ The length of the beam modifier, L, depends on X2, which is the thickness for E2. The beam modifier can thus be shaped as shown in Fig. 1 with sawteeth surfaces 23 having slope ~/VKm, where Xl is the largest thickness and X2 is the smallest thickness corresponding to the desired width of buried collector region 19. The beam modifier is preferably oscillated a large number of cycles l 162326 12 46,767 of the energy spectrum of the transmitted ion beam 22 to eliminate spec~rum distortions produced by small temporal fluctuations in the energy and density of ion beam 20 as it emitted from a typically ion source.
After beam modifier 21 is appropriately formed and positioned as described, the transistor as formed with emitter and base regions 14 and 15 is positioned with major surface 11, which has been selected for reference distance, to be exposed to the transmitted ion beam 22.
Semiconductor body 10 is then irradiated with ion beam 20 through oscillating beam modifier 21 to form buried col-lector region 19 having a constant impurity ConCentratiOn gradient. The ion dosage is selected to correspond to the desired impurity concentration in buried collector region.
Emitter electrodes 24 and gate electrode 25 are then formed on major surface 11 by standard metalizing and photoetch techniques. For a power device, lateral edges 26 may be beveled and passivated by standard techniques and electrode or other electrical components provided, to which buried collector region 19 connects.
Referring to Fig. 2 a transistor similar to that shown and described in connection with Fig. 1 is made utilizing the present invention to simultaneously form both buried collector region and the emitter region. The same elements have been eorrespondingly numbered with the prefix "1" before them. The transistor shown in Fig. 2 is rim gated instead of center gated as shown in Fig. l to provide for simultaneous formation of the emitter and buried collector regions.
The two impurities region are simultaneously formed by making beam modifier 121 in a step function shape. The shape of surfaces 123 control the depth, thickness and impurity concentration gradient of buried collector region 119 and the shape of surfaces 123' con-trol the thickness and impurity concentration gradient of emitter region 114. As shown, it is assumèd that a con-stant impwrity concentration gradient is desired in both impurities regions. An ion shield 127 is provided to mask ~ 16232~
13 46,767 section areas of the transistor and confine the emitter and buried collector regions 114 to certain parts of the semiconductor body 10. This is to thereafter permit gate electrode 125 to be formed on major surface 11 and made ohmic contact with base region 115. The dosage of ion beam is again controlled to provide the desired impurity concentration in the impurity regions.
Referring to Fig. 3, an MOS field effect tran-sistor is formed in an integrated circuit where the pres-ent invention is used to form the isolation impurity regions between the electrical compon~nts. The MOS field effect transistor is formed in a semiconductor body 210 formed on substrate 211, for example, by electrostatic or epitaxial techniques. Source and drain impurity region 212 and 213 are formed in the semiconductor body prefer-ably simultaneously by standard photoetching and diffusion techniques, and are spaced apart to form channel region 214 between them of the impurity formed in the semicon-ductor body during its making.
The semiconductor body is then positioned for irradiation through major surface 215 by ion beam 216 through beam modifier 217 which oscillates as indicated during the irradiation. The ion beam 216 is of sufficient energy to penetrate through semiconductor body 210 and the beam modifier 217 is shaped with sawtooth surfaces 218 to provide impurity regions 219 extending entirely through the semiconductor body with a constant impurity concentra-tion gradient. The scope of the sawteeth surfaces 218 and their lengths are selected to this end given the energy level of ion beam 216, the material of beam modifier 217, and the width of semiconductor body 210.
The conductivity type of the ion of ion beam 216 is also selected to be opposite to the impurity in semi-conductor body 210 to provide PN junctions in 220 the semiconductor body isolating the transistor from the remainder of the electrical components of the integered circuit in the body. Also ion shield 221 is interposed in the path of transmitted ion beam 222 to mask the area of 14 46,767 the semiconductor body containing the transistor from the ion beam.
As shown, the isolating impurity regions 219 can then be formed in semiconductor body 210 by irradiating semiconductor body through major surface 215 with trans-mitted ion beam 222. By this technique various electrical components in semiconductor body 10 can be electrically isolated rapidly and with high precision. Indeed, because of the high resolution and precise positioning of the isolating impurity regions 219, many more electrical components can be formed for a given area of major surface 215 of semiconductor body 210, and quality and performance of integered circuits can be increased.
Oxide layer 223 and passivating layer 224, 15source electrode 225, drains electrode 226 and gate elec-trode 227 are then sequentially formed on major surface 215 of semiconductor body 210 by standard oxide growth, photoetching and metalizing techniques to complete the transistor and the integered circuit.
2~Referring to Fig. 4, a semiconductor 310 is shown in which an impurity region with a variable concen-tration gradient is formed using the present invention.
The impurity region as shown is buried in the semiconduct-or body 310, or adjoining major surfaces 211 or 213 as desired. The impurity region can thus be used in various applications.
Fig. 4 shows the relation between the shape of beam modifier 313 and impurity region 314 formed in semi-conductor body 310. The surfaces 315, 316 and 317 are of shapes and lengths corresponding to the thicknesses and impurity concentration gradients of portions 318, 319 and 320, respectively. The maximum thickness of modifier 313 corresponds to the distance of impurity region 314 from major surface 311 given the material of modifier 313 and the energy of ion beam 320 to the beam modifier. The transmitted ion beam 321 thus corresponds to the desired overall positioning and impurity concentration profile of impurity 314 to be formed in semiconductor body 310.
15 46,767 The impurity region 314 is thus formed by posi-tioning the semiconductor body 310 for irradiation through major surface 311, selected for reference, by ion beam 320 transmitted through beam modifier 313; and irradiating 5semiconductor body 310 through major surface 311 with the modified ion beam 321 while modifier 313 is oscillated as indicated in Fig. 4. The relative shape of the dosage gradient of the impurity region 314 is shown by the small graph to the right of Fig. 4.
10Referring to Fig. 5, a second semiconductor body 1310 is shown in which an impurity region with an impurity concentration gradient is formed using the present inven-tion. The elements and their relation are the same as that described in connection with Figure 4 and are identi-fied with a prefix "1." The differences are the position-ing of impurity region 1314 adjoining major surface 1311, selected for reference, and the impurity concentration gradient of impurity region 1314 and corresponding shape of beam modified 1313. Shaped surfaces 1315 are parabolic providi~g a parabolic impurity concentration profile to impurity region 1314, as best shown by the small graph to the left of Fig. 5.
Referring to Fig. 6, a third semiconductor body 2310 is shown in which two impurity regions with different impurity concentration gradients are simultaneously formed using the present invention. The elements and their relation are the same as that described in connection with Fig. 4 and are identified with a prefix "2." The differ-ences are positioning and concentration gradients of the impurity regions and the corresponding shape of the beam modifier 2313. Shaped surfaces 2315 and 2316 are in step function relation, with surfaces 2315 corresponding to gaussion distribution concentration profile for buried impurity region 2318 and surfaces 2316 corresponding to an inverse gaussion distribution concentration profile for buried impurity region 2319. The concentration gradients of impurity regions 2318 and 2319 and their spatial rela tion to each other is best seen by the small graph to the l 16232~
16 46,767 left of Fig. 6.
As shown in Figs. 4, 5 and 6, the present inven-tion provides a flexibility in locating impurity regions and imparting concentrations profiles to such impurity regions heretofore not known. Furthermore, the present invention provides a speed and precision in forming impur-ity heretofore not known.
While presently preferred embodiments have been shown and described, it is distinctly understood that the invention may otherwise be variously performed and embod-ied within the scope of the following claims.
SUMMARY OF THE INVENTION
The present invention is a method of forming an impurity region or regions in a semiconductor body by high energy ion irradiation. An ion beam is formed containing ions of an impurity desired to form an impurity region or regions in a selected semiconductor body. The ion beam is Z0 of such enérgy that it can penetrate the semiconductor body through a selected surface to a depth greater than the maximum depth of a desired impurity region from the selected surface.
A beam modifier is formed of a given material in a non-uniform shape to modify the energy of the radiation beam on transmission therethrough to form a transmitted `energy beam capable of forming an impurity region of a desired thickness and impurity gradient in the semicon-ductor body a given distance from a selected surface through which the semiconductor body is irradiated.
Preferably the beam modifier is made of a material such as aluminum, beryllium or radiation-resistant silicone or epoxy to reduce scattering ~nd to provide good resolution for the transmitted ion beam.
The impurity region is formed by positioning the selected surface of the semiconductor body to be exposed to the ion beam through the beam modifier. The beam transmitted through the beam modifier thus penetrates the ~ 18232~
46,767 semiconductor body through the selec~ed surface and forms the desired impurity region within the body. The thick-ness of the impurity region (i.e., its distance along the transmission direction of the ion beam) and its distance from the selected surface are accurately controlled by the energ~ of the ion beam and thickness of the beam modifier.
The impurity concentration profile of the impurity region is controlled with precision by the contour of the beam modifier and the predetermined relative movement between the beam ~odifier and the semiconductor body during dop-ing.
The present invention is particularly useful in preparing semicondùctor devices where buried regions and regions of previously unusual doping concentration gradi-ents are desired. In some embodiments the semiconductorbody may be preferably annealed after the doping operation to reduce the damage to the crystalline lattice of the semiconductor body.
Other details, objects and advantages of the 2~ invention become apparent as the following description of the presently preferred embodiments and presently prefer-red methods of practicing the same proceeds.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, the presently preferred embodiments of the invention and the presently preferred methods of practicing the invention are illu-strated in which:
Figure 1 is an elevational view in cross-section of a transistor with a buried collector region made in accordance with the present invention;
Fig. 2 is an elevational view in cross-section of a second transistor with a buried collector region made in accordance with the present invention;
Fig. 3 is an elevational view in cross-section of an integrated circuit made in accordance with the present invention;
Fig. 4 is an elevational view in cross-section of a semiconductor body wherein an impurity region is t 162326 6 46,767 formed in accordance with the present invention;
Fig. 5 is an elevational view in cross-section of a second semiconductor body in which an impurity region is formed in accordance with the present invention; and Fig. 6 is an elevational view in cross-section of a third semiconductor body formed in accordance with the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Fig. 1, a transistor is made with a buried collector region utilizing the present invention.
The transistor is formed in semiconductor body 10 having opposed major surfaces 11 and 12, which has been attached to substrate 13 at major surface 12 by alloying, electro-- static technique, epitaxial growth or some other means.
The semiconductor body is doped during manufacture to the desired impurity concentration for the collector region, e.g., 1 x 1013 to 1 x 1014 per cubic centimeter. Sub-strate 13 is preferably an insulator material appropriate for the particular application.
Base region 15 and emitter region 14 are formed by sequential diffusions of impurities of opposite conduc-tivity type, e.g., gallium and phosphorus, through major surface 11 using standard oxide masking and photoetch techniques. The impurity utilized in forming base region 14 is also of opposite conductivity type from the impuri-ties formed in the semiconductor body during its manufac-ture. PN junctions 17 and 18 are thus formed in the semiconductor body between emitter and base regions 14 and 15 and collector and base regions 15 and 16. The impurity concentration of base region 15 typically ranges from 1 x 1015 to 1 x 1017 per cubic centimeter, and the impur-ity concentration of emitter region typically ranges from 1 x 1017 to 1 x 1019 per cubic centimeter. Collector region 12 is formed of the impurity concentration in the remaining part of semiconductor body 10 using the irradia-tion technique hereinafter described.
Buried collector region 19 is then formed in the semiconductor body at a depth to provide the desired width 7 46,767 of collector region 16. The buried collector region is a conductor electrically connecting the transistor to anoth-er electrical component preferably in the same semicon-ductor body.
To forming collector region 19 an ion source is provided which is capable of emitting particles with molecular weight of at least one (1) to form ion beam 20.
Ion beam 20 is of an energy capable of penetrating semi-conductor body 10 through selected surface 11 to a depth greater than the desired depth of buried collector region 19 in the body.
The ion source may be any conveniently available source which emits ions of an impurity desired to form buried collector region with sufficient energy to pene-trate body 10 to at least the desired depth of the buriedcollector region. Preferably the ion source is a Van de Graaff accelerator emitting ions of boron because such particles are relatively inexpensive to accelerate to energy sufficient to penetrate the semi,conductor body to the desired depth. Other ions suitable to form impurities in semiconductor materials, such as phosphorus or alumi-num, may be utilized; however, ions having a molecular weight higher than 16 are presently impractical because available ion sources, e.g., Van de Graaff accelerators, do not generate high enough energy to cause penetration of such higher molecular weight particles into material to a significant depth. In any event, the ion selected must be of the same conductivity type as that utilized for col-lector region 16 to provide the desired electrical charac-teristics to the buried collector region.
The ion source is also preferably a monoenerget-ic source such as conventionally produced by Van de Graaff accelerators to permit the buried collector region to be more precisely controlled in thickness, width and dosage gradient. For this reason, higher molecular particles such as phosphorus or aluminum ions may be more useful in certain applications where higher resolution is desired for the impurity region because such ions have a narrower 1 ~62326 8 46,767 half-width to the defect generation distribution produced in semiconductor materials. The narrower the half-width the more precisely the impurity region desired for buried collector region 19 can be positioned in semiconductor body 10 and the more precisely the concentration and concentration grad~ent can be controlled.
Additionally, it should be observed that it may be appropriate in certain applications to use a non-mono-energetic radiation source or to modify a monoenergetic source so that it is not monoenergetic. For example, it may be more desirable to have a more uniform particle distribution over the area of semiconductor body 10 at a sacrifice of resolution of the depth of the impurity region. This can be done by utilization of a scattering foil (not shown) in the path of the ion beam 20 between the ion source and semiconductor body 10. Generally, however, a monoenergetic radiation source is preferred to provide the narrowest half-width for the defect generation distribution of the beam in the material and in turn the highest possible resolution for the impurity region formed in the semiconductor body.
Positioned between the ion beam 20 and semicon-ductor body 10 is beam modifier 21 Beam modifier 21 is selected of a material to allow transmission of ion beam 20 through it normally without substantially scattering of the beam, Although in some circumstances it may be ap-propriate to incorporate a scattering foil with beam modifier 21, typically it is desired that the transmitted ion beam 22 not be dispersed due to variations in the thickness of modifier 21. This improves the accuracy of the placement and resolution of the impurity region. Beam modifier 21 is of a material which modifies the energy of the transmitted ion beam, but is preferably selected from a material which does not modify the energy of the beam greatly per unit thickness. This permits the accuracy of the thickness and dosage gradient of the impurity region to be more precisely controlled without critically con-trolling dimensional tolerances of beam modifier 21 t 162326 9 46,767 Examples of such materials are those composed of low atomic number elements such as aluminum or beryllium. If the ion beam used not penetrated too deeply into semicon-ductor body, radiation resistance silicone and epoxy may be used. Also, the beam modifier is preferably made of a material that is easily worked to the desired shape as hereinafter explained.
Preferably semiconductor body 10 and beam modi-fier 21 are moved relative to each other through a prede-termined motion during the doping. This can be done byany suitable means. Beam modifier 21 is preferably oscil-lated normal to the path of ion beam 20 parallel to major surface 11 of semiconductor body 10 as indicated in Fig.
1. Alternatively, beam modifier 21 could be rotated or otherwise moved relative to semiconductor body 10, or semiconductor body 10 can be moved relative to beam modi-fier 21 in a predetermined path.
Given the ion source and the composition of the beam modifier 21, the thickness and impurity concentration gradient of the impurity region to be formed in semicon-ductor~body 10 becomes a function of the shape of the beam modifier 21 and the relative motion between the semicon-ductor body and the beam modifier doping. Typically the relative movement between the beam modifier and the body is fixed so that the thickness and impurity gradient of the impurity region becomes a function solely of the shape of the beam modifier.
One can therefore shape the beam modifier to correspond to any desired width and impurity concentration gradient desired for the impurity region and any desired distance between major surface 11 and impurity region 19 in the semiconductor body. To understand the relation, consider that the energy spectrum of ion beam 22 after transmission through beam modifier 21 corresponding to the desired positioning, width and impurity concentration gradient desired for buried collector impurity region 19 is represented by the mathematical function dn(Et)/dEt =
h(Et). Further, consider that the beam modifier shape , l 162326 46,767 corresponding to this energy spectrum is represented by the mathematical function F(~) = X, where X is the thick-ness of the modifier and ~ is the distance along the modifier from a coordinate. Also consider that ~ is a mathematical function of X, F(X).
Now consider the energy of transmitted ion beam 22 at a point at major surface 11. The ion beam directed at this point must pass through a thickness XQ of beam modifier 21 which will reduce the energy of the beam from E to E~. The flux density at the point on major surface 11 is 0 in ions per second, stated mathematically as d = dn/dt. Since beam modifier 21 moves horizontally as shown in Fig. 1 with a speed V = d ~ dt, the number of ions which strike the selected point on major surface 11 in a time dt is defined as dn = ~dt - 0/V~ d~. Since ~ = f~x) and d~ = df(x)/dx dx, dn = ~/V~ df(x)/dx.dx.
The variable x is the thickness of beam modifier 21 through which the ion beam passes to the point on major surface 11 at any moment in time and is functionally related to the energy of the ions emerging from the beam modifier in ion beam 22. Suppose that R (the range of the ions) and E (the energy of the ions) are related by the mathematical function R = g(E). The range of the incoming ion in beam 20 to the beam modifier is Rp - g(Ep), and the range of the exiting ions in beam 22 is R = g(E). The thickness of beam modifier 21 can be expressed as a mathe-matical function of the energy of the ion beam as follows:
x = Rp - R = g(Ep) - g(E).
Substituting this x in the preceding equation the ion reaching the selected point on major surface 11 can be stated as:
dn = d, df (gdEp(E)- g(E)~ . ~ , dE
The thickness of beam modifier 21 can thus be expressed mathematically in terms of the transmitted energy spectrum of the ion beam as follows:
-~ -` 1 16232~
11 46,767 df (g(Ep)E) g(E)) = ~ a~ ( ~ ) For complex energy spectra, dn/dE, the shape of the modifier 21 can be calculated by computer. For more simple spectra the shape can be determined by simple hand calculation.
For example, consider where buried collector region 19 is to be rectangular with a constant impurity concentration gradient across its thickness x and area.
dn/dE = K (a constant) and R = g(E) = E/m, i.e., the range dependence on ion energy is linear with mass. The mathe-matical function shown above reduces to:
~Ep E~
df ~ m m) V K dE
d (E) 0 (m) Substituting x = Ep/m - E/m, the function fur-ther reduces to:
15 ~ = VK
x ~
The general solution to this equation is:
f(x) = V~_ mx + b = 1 Stated another way for x = F(R):
_ d + b~
x - VK VK m 20The constant b can be obtained by letting x be the thickness X (at ~ = 0) for the lowest energy in the spectrum:
b = X~ V~_ The length of the beam modifier, L, depends on X2, which is the thickness for E2. The beam modifier can thus be shaped as shown in Fig. 1 with sawteeth surfaces 23 having slope ~/VKm, where Xl is the largest thickness and X2 is the smallest thickness corresponding to the desired width of buried collector region 19. The beam modifier is preferably oscillated a large number of cycles l 162326 12 46,767 of the energy spectrum of the transmitted ion beam 22 to eliminate spec~rum distortions produced by small temporal fluctuations in the energy and density of ion beam 20 as it emitted from a typically ion source.
After beam modifier 21 is appropriately formed and positioned as described, the transistor as formed with emitter and base regions 14 and 15 is positioned with major surface 11, which has been selected for reference distance, to be exposed to the transmitted ion beam 22.
Semiconductor body 10 is then irradiated with ion beam 20 through oscillating beam modifier 21 to form buried col-lector region 19 having a constant impurity ConCentratiOn gradient. The ion dosage is selected to correspond to the desired impurity concentration in buried collector region.
Emitter electrodes 24 and gate electrode 25 are then formed on major surface 11 by standard metalizing and photoetch techniques. For a power device, lateral edges 26 may be beveled and passivated by standard techniques and electrode or other electrical components provided, to which buried collector region 19 connects.
Referring to Fig. 2 a transistor similar to that shown and described in connection with Fig. 1 is made utilizing the present invention to simultaneously form both buried collector region and the emitter region. The same elements have been eorrespondingly numbered with the prefix "1" before them. The transistor shown in Fig. 2 is rim gated instead of center gated as shown in Fig. l to provide for simultaneous formation of the emitter and buried collector regions.
The two impurities region are simultaneously formed by making beam modifier 121 in a step function shape. The shape of surfaces 123 control the depth, thickness and impurity concentration gradient of buried collector region 119 and the shape of surfaces 123' con-trol the thickness and impurity concentration gradient of emitter region 114. As shown, it is assumèd that a con-stant impwrity concentration gradient is desired in both impurities regions. An ion shield 127 is provided to mask ~ 16232~
13 46,767 section areas of the transistor and confine the emitter and buried collector regions 114 to certain parts of the semiconductor body 10. This is to thereafter permit gate electrode 125 to be formed on major surface 11 and made ohmic contact with base region 115. The dosage of ion beam is again controlled to provide the desired impurity concentration in the impurity regions.
Referring to Fig. 3, an MOS field effect tran-sistor is formed in an integrated circuit where the pres-ent invention is used to form the isolation impurity regions between the electrical compon~nts. The MOS field effect transistor is formed in a semiconductor body 210 formed on substrate 211, for example, by electrostatic or epitaxial techniques. Source and drain impurity region 212 and 213 are formed in the semiconductor body prefer-ably simultaneously by standard photoetching and diffusion techniques, and are spaced apart to form channel region 214 between them of the impurity formed in the semicon-ductor body during its making.
The semiconductor body is then positioned for irradiation through major surface 215 by ion beam 216 through beam modifier 217 which oscillates as indicated during the irradiation. The ion beam 216 is of sufficient energy to penetrate through semiconductor body 210 and the beam modifier 217 is shaped with sawtooth surfaces 218 to provide impurity regions 219 extending entirely through the semiconductor body with a constant impurity concentra-tion gradient. The scope of the sawteeth surfaces 218 and their lengths are selected to this end given the energy level of ion beam 216, the material of beam modifier 217, and the width of semiconductor body 210.
The conductivity type of the ion of ion beam 216 is also selected to be opposite to the impurity in semi-conductor body 210 to provide PN junctions in 220 the semiconductor body isolating the transistor from the remainder of the electrical components of the integered circuit in the body. Also ion shield 221 is interposed in the path of transmitted ion beam 222 to mask the area of 14 46,767 the semiconductor body containing the transistor from the ion beam.
As shown, the isolating impurity regions 219 can then be formed in semiconductor body 210 by irradiating semiconductor body through major surface 215 with trans-mitted ion beam 222. By this technique various electrical components in semiconductor body 10 can be electrically isolated rapidly and with high precision. Indeed, because of the high resolution and precise positioning of the isolating impurity regions 219, many more electrical components can be formed for a given area of major surface 215 of semiconductor body 210, and quality and performance of integered circuits can be increased.
Oxide layer 223 and passivating layer 224, 15source electrode 225, drains electrode 226 and gate elec-trode 227 are then sequentially formed on major surface 215 of semiconductor body 210 by standard oxide growth, photoetching and metalizing techniques to complete the transistor and the integered circuit.
2~Referring to Fig. 4, a semiconductor 310 is shown in which an impurity region with a variable concen-tration gradient is formed using the present invention.
The impurity region as shown is buried in the semiconduct-or body 310, or adjoining major surfaces 211 or 213 as desired. The impurity region can thus be used in various applications.
Fig. 4 shows the relation between the shape of beam modifier 313 and impurity region 314 formed in semi-conductor body 310. The surfaces 315, 316 and 317 are of shapes and lengths corresponding to the thicknesses and impurity concentration gradients of portions 318, 319 and 320, respectively. The maximum thickness of modifier 313 corresponds to the distance of impurity region 314 from major surface 311 given the material of modifier 313 and the energy of ion beam 320 to the beam modifier. The transmitted ion beam 321 thus corresponds to the desired overall positioning and impurity concentration profile of impurity 314 to be formed in semiconductor body 310.
15 46,767 The impurity region 314 is thus formed by posi-tioning the semiconductor body 310 for irradiation through major surface 311, selected for reference, by ion beam 320 transmitted through beam modifier 313; and irradiating 5semiconductor body 310 through major surface 311 with the modified ion beam 321 while modifier 313 is oscillated as indicated in Fig. 4. The relative shape of the dosage gradient of the impurity region 314 is shown by the small graph to the right of Fig. 4.
10Referring to Fig. 5, a second semiconductor body 1310 is shown in which an impurity region with an impurity concentration gradient is formed using the present inven-tion. The elements and their relation are the same as that described in connection with Figure 4 and are identi-fied with a prefix "1." The differences are the position-ing of impurity region 1314 adjoining major surface 1311, selected for reference, and the impurity concentration gradient of impurity region 1314 and corresponding shape of beam modified 1313. Shaped surfaces 1315 are parabolic providi~g a parabolic impurity concentration profile to impurity region 1314, as best shown by the small graph to the left of Fig. 5.
Referring to Fig. 6, a third semiconductor body 2310 is shown in which two impurity regions with different impurity concentration gradients are simultaneously formed using the present invention. The elements and their relation are the same as that described in connection with Fig. 4 and are identified with a prefix "2." The differ-ences are positioning and concentration gradients of the impurity regions and the corresponding shape of the beam modifier 2313. Shaped surfaces 2315 and 2316 are in step function relation, with surfaces 2315 corresponding to gaussion distribution concentration profile for buried impurity region 2318 and surfaces 2316 corresponding to an inverse gaussion distribution concentration profile for buried impurity region 2319. The concentration gradients of impurity regions 2318 and 2319 and their spatial rela tion to each other is best seen by the small graph to the l 16232~
16 46,767 left of Fig. 6.
As shown in Figs. 4, 5 and 6, the present inven-tion provides a flexibility in locating impurity regions and imparting concentrations profiles to such impurity regions heretofore not known. Furthermore, the present invention provides a speed and precision in forming impur-ity heretofore not known.
While presently preferred embodiments have been shown and described, it is distinctly understood that the invention may otherwise be variously performed and embod-ied within the scope of the following claims.
Claims (14)
1. A method of forming an impurity region in a semiconductor body comprising the steps of:
A. forming an ion beam containing ions of an impurity to form a desired impurity region in a selected semiconductor body;
B. forming a beam modifier of a given material and non-uniform shape to modify the energy of said ion beam on transmission therethrough to shape to modify said ion beam on transmission therethrough to form an impurity region of a desired thickness and concentration gradient in the semiconductor body on irradiation of the semicon-ductor body through a selected surface with said transmit-ted ion beam;
C. positioning the selected surface of the semiconductor body to be irradiated with said ion beam through said beam modifier; and D. thereafter irradiating the semiconductor body with the ion beam through the beam modifier until the impurity region of the desired thickness and concentration gradient is formed in the semiconductor body.
A. forming an ion beam containing ions of an impurity to form a desired impurity region in a selected semiconductor body;
B. forming a beam modifier of a given material and non-uniform shape to modify the energy of said ion beam on transmission therethrough to shape to modify said ion beam on transmission therethrough to form an impurity region of a desired thickness and concentration gradient in the semiconductor body on irradiation of the semicon-ductor body through a selected surface with said transmit-ted ion beam;
C. positioning the selected surface of the semiconductor body to be irradiated with said ion beam through said beam modifier; and D. thereafter irradiating the semiconductor body with the ion beam through the beam modifier until the impurity region of the desired thickness and concentration gradient is formed in the semiconductor body.
2. A method of forming an impurity region in a semiconductor body as set forth in Claim 1 comprising in addition:
E. thereafter annealing the semiconductor body to remove detrimental electrical characteristics caused by irradiation from the semiconductor body.
E. thereafter annealing the semiconductor body to remove detrimental electrical characteristics caused by irradiation from the semiconductor body.
3. A method of forming an impurity region in a semiconductor body as set forth in Claim 1 wherein:
18 46,767 the beam modifier is formed with reference to a predetermined movement of the modifier relative to semi-conductor body during irradiation to form the impurity region of the desired thickness and concentration gradi-ent; and the beam modifier is moved relative to the semiconductor body through said predetermined movement during the irradiation to form the impurity region in the semiconductor body.
18 46,767 the beam modifier is formed with reference to a predetermined movement of the modifier relative to semi-conductor body during irradiation to form the impurity region of the desired thickness and concentration gradi-ent; and the beam modifier is moved relative to the semiconductor body through said predetermined movement during the irradiation to form the impurity region in the semiconductor body.
4. A method of forming an impurity region of a semiconductor body as set forth in Claim 3 wherein:
the ion beam is substantially monoenergetic.
the ion beam is substantially monoenergetic.
5. A method of forming an impurity region of a semiconductor body as set forth in Claim 1 wherein:
the beam modifier is formed with reference to a predetermined movement of the semiconductor body relative to the beam modifier during irradiation to form the impur-ity region of the desired thickness and concentration gradient; and the semiconductor body is moved relative to the semiconductor body through said predetermined movement during the irradiation to form the impurity region in the semiconductor body.
the beam modifier is formed with reference to a predetermined movement of the semiconductor body relative to the beam modifier during irradiation to form the impur-ity region of the desired thickness and concentration gradient; and the semiconductor body is moved relative to the semiconductor body through said predetermined movement during the irradiation to form the impurity region in the semiconductor body.
6. A method of forming an impurity region of a semiconductor body as set forth in Claim 5 wherein:
the ion beam is substantially monoenergetic.
the ion beam is substantially monoenergetic.
7. A method of forming an impurity region of a semiconductor body as set forth in Claim 1 wherein:
at least two non-contagious impurity regions are formed in the semiconductor body simultaneously.
at least two non-contagious impurity regions are formed in the semiconductor body simultaneously.
8. A method of forming a buried impurity region in a semiconductor body comprising the steps of:
A. forming an ion beam containing ions of an impurity and energy to penetrate a selected semiconductor body through a selected surface to form a desired buried impurity region in the semiconductor body;
B. forming a beam modifier of a given material and non-uniform shape to modify the energy of said ion 19 46,767 beam on transmission throughout to form a buried impurity region of a desired thickness and concentration gradient at a given distance from the selected surface in the semiconductor body on irradiation of the semiconductor body through the selected surface with said transmitted ion beam;
C. positioning the selected surface of the semiconductor body to be irradiated with said ion beam through said beam modifier; and D. thereafter irradiating the semiconductor body with the ion beam through the beam modifier until the buried impurity region of the desired thickness and con-centration gradient is formed in the semiconductor body a given depth from the selected surface.
A. forming an ion beam containing ions of an impurity and energy to penetrate a selected semiconductor body through a selected surface to form a desired buried impurity region in the semiconductor body;
B. forming a beam modifier of a given material and non-uniform shape to modify the energy of said ion 19 46,767 beam on transmission throughout to form a buried impurity region of a desired thickness and concentration gradient at a given distance from the selected surface in the semiconductor body on irradiation of the semiconductor body through the selected surface with said transmitted ion beam;
C. positioning the selected surface of the semiconductor body to be irradiated with said ion beam through said beam modifier; and D. thereafter irradiating the semiconductor body with the ion beam through the beam modifier until the buried impurity region of the desired thickness and con-centration gradient is formed in the semiconductor body a given depth from the selected surface.
9. A method of forming a buried impurity region as set forth in Claim 8 comprising in addition:
thereafter annealing the semiconductor body to remove detrimental electrical characteristics caused by irradiation from the semiconductor body.
thereafter annealing the semiconductor body to remove detrimental electrical characteristics caused by irradiation from the semiconductor body.
10. A method of forming a buried impurity region in a semiconductor body as set forth in Claim 8 wherein:
the beam modifier is formed with reference to a predetermined movement of the modifier relative to the semiconductor body during irradiation to form the impurity region of the desired thickness and concentration gradi-ent; and the beam modifier is moved relative to the semiconductor body through said predetermined movement during the irradiation to form the impurity region in the semiconductor body.
the beam modifier is formed with reference to a predetermined movement of the modifier relative to the semiconductor body during irradiation to form the impurity region of the desired thickness and concentration gradi-ent; and the beam modifier is moved relative to the semiconductor body through said predetermined movement during the irradiation to form the impurity region in the semiconductor body.
11. A method of forming a buried impurity region in a semiconductor body as set forth in Claim 10 wherein:
the ion beam is substantially monoenergetic
the ion beam is substantially monoenergetic
12. A method of forming a buried impurity region in a semiconductor body as set forth in Claim wherein:
46,767 the beam modifier is formed with reference to a predetermined movement of the semiconductor body relative to the beam modifier during irradiation to form the impur-ity region of a desired thickness and concentration gradi-ent; and the semiconductor body is moved relative to the semiconductor body through said predetermined movment during the irradiation to form the impurity region in the semiconductor body.
46,767 the beam modifier is formed with reference to a predetermined movement of the semiconductor body relative to the beam modifier during irradiation to form the impur-ity region of a desired thickness and concentration gradi-ent; and the semiconductor body is moved relative to the semiconductor body through said predetermined movment during the irradiation to form the impurity region in the semiconductor body.
13. A method of forming a buried impurity region in a semiconductor body as set forth in Claim 12 wherein:
the ion beam is substantially monoenergetic.
the ion beam is substantially monoenergetic.
14. A method of forming a buried impurity region of a semiconductor body as set forth in claim 1 where-in:
at least two non-contagious impurity regions are formed in the semiconductor body simultaneously.
at least two non-contagious impurity regions are formed in the semiconductor body simultaneously.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US16024480A | 1980-06-17 | 1980-06-17 | |
| US160,244 | 1980-06-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162326A true CA1162326A (en) | 1984-02-14 |
Family
ID=22576117
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000379841A Expired CA1162326A (en) | 1980-06-17 | 1981-06-16 | Forming impurity regions in semiconductor bodies by high energy ion irradiation, and semiconductor devices made thereby |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS586301B2 (en) |
| BE (1) | BE889247A (en) |
| BR (1) | BR8103773A (en) |
| CA (1) | CA1162326A (en) |
| DE (1) | DE3123949A1 (en) |
| FR (1) | FR2484701A1 (en) |
| GB (1) | GB2078441A (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6039686U (en) * | 1983-08-24 | 1985-03-19 | 株式会社 大喜 | Bon lantern |
| DE3402653A1 (en) * | 1984-01-26 | 1985-08-01 | Siemens AG, 1000 Berlin und 8000 München | Method for producing specially doped regions in semiconductor material |
| GB2156383A (en) * | 1984-02-06 | 1985-10-09 | Plessey Co Plc | Infra-red material structures |
| DE3404834A1 (en) * | 1984-02-08 | 1985-08-08 | Hahn-Meitner-Institut für Kernforschung Berlin GmbH, 1000 Berlin | SEMICONDUCTOR POWER COMPONENT, IN PARTICULAR THYRISTOR AND GRIDISTOR, AND METHOD FOR THE PRODUCTION THEREOF |
| JPS623776A (en) * | 1985-06-29 | 1987-01-09 | Zojirushi Vacuum Bottle Co | Thawing of frozen food and apparatus for controlling same |
| JPH0334488Y2 (en) * | 1985-09-19 | 1991-07-22 | ||
| SE454309B (en) * | 1986-08-29 | 1988-04-18 | Stiftelsen Inst Mikrovags | PROCEDURE TO MAKE THIN LEADING OR SEMI-CONDUCTIVE LAYERS EMBEDDED IN SILICONE MEDIUM ATLANT IMPLANTATION |
| US4816421A (en) * | 1986-11-24 | 1989-03-28 | American Telephone And Telegraph Company, At&T Bell Laboratories | Method of making a heteroepitaxial structure by mesotaxy induced by buried implantation |
| JPH05198666A (en) * | 1991-11-20 | 1993-08-06 | Mitsubishi Electric Corp | Semiconductor device and manufacture thereof |
| EP0584436A1 (en) * | 1992-08-26 | 1994-03-02 | Co.Ri.M.Me. Consorzio Per La Ricerca Sulla Microelettronica Nel Mezzogiorno | Process for forming buried regions, having different doping concentration, in monolitic semiconductor devices |
| US5317787B1 (en) * | 1992-10-01 | 1995-11-28 | Thomas & Betts Corp | Cable tie having improved tail gripping and holding feature |
| US5364800A (en) * | 1993-06-24 | 1994-11-15 | Texas Instruments Incorporated | Varying the thickness of the surface silicon layer in a silicon-on-insulator substrate |
| DE10006523A1 (en) * | 2000-02-15 | 2001-08-23 | Infineon Technologies Ag | Implantation mask for high energy ion implantation |
| JP2007287973A (en) * | 2006-04-18 | 2007-11-01 | Toyota Motor Corp | Stencil mask, its utilization method, and charged particle injector utilizing it |
| DE102015202121B4 (en) * | 2015-02-06 | 2017-09-14 | Infineon Technologies Ag | SiC based super-barrier semiconductor devices and methods of making them |
| DE102015114429B4 (en) | 2015-08-28 | 2017-05-11 | Infineon Technologies Ag | A particle irradiation apparatus, a beam modifier apparatus and a method of manufacturing a semiconductor device having a junction termination extension zone |
| DE102016110429A1 (en) | 2016-06-06 | 2017-12-07 | Infineon Technologies Ag | Energy filter for processing a power semiconductor device |
| CN111599504B (en) * | 2020-05-29 | 2022-05-17 | 中国科学院近代物理研究所 | Heavy ion irradiation system and irradiation method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4968660A (en) * | 1972-11-04 | 1974-07-03 | ||
| US4035226A (en) * | 1975-04-14 | 1977-07-12 | Rca Corporation | Method of preparing portions of a semiconductor wafer surface for further processing |
| US4257825A (en) * | 1978-08-30 | 1981-03-24 | U.S. Philips Corporation | Method of manufacturing semiconductor devices having improvements in device reliability by thermally treating selectively implanted test figures in wafers |
-
1981
- 1981-06-01 GB GB8116666A patent/GB2078441A/en not_active Withdrawn
- 1981-06-15 BR BR8103773A patent/BR8103773A/en unknown
- 1981-06-16 CA CA000379841A patent/CA1162326A/en not_active Expired
- 1981-06-16 DE DE19813123949 patent/DE3123949A1/en not_active Withdrawn
- 1981-06-16 BE BE0/205118A patent/BE889247A/en not_active IP Right Cessation
- 1981-06-16 FR FR8111869A patent/FR2484701A1/en not_active Withdrawn
- 1981-06-17 JP JP56092406A patent/JPS586301B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2484701A1 (en) | 1981-12-18 |
| BE889247A (en) | 1981-12-16 |
| GB2078441A (en) | 1982-01-06 |
| JPS586301B2 (en) | 1983-02-03 |
| BR8103773A (en) | 1982-03-09 |
| JPS5727027A (en) | 1982-02-13 |
| DE3123949A1 (en) | 1982-02-04 |
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