CA1159918A - Ultra-thin film capacitor and method for manufacture thereof - Google Patents
Ultra-thin film capacitor and method for manufacture thereofInfo
- Publication number
- CA1159918A CA1159918A CA000358899A CA358899A CA1159918A CA 1159918 A CA1159918 A CA 1159918A CA 000358899 A CA000358899 A CA 000358899A CA 358899 A CA358899 A CA 358899A CA 1159918 A CA1159918 A CA 1159918A
- Authority
- CA
- Canada
- Prior art keywords
- metal
- film
- electrode
- metal oxide
- ions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/06—Solid dielectrics
- H01G4/08—Inorganic dielectrics
- H01G4/10—Metal-oxide dielectrics
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Semiconductor Integrated Circuits (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
- Apparatuses And Processes For Manufacturing Resistors (AREA)
Abstract
ULTRA-THIN FILM CAPACITOR
AND METHOD FOR MANUFACTURE THEREOF
Abstract A suitable substrate is provided to which is applied a metal electrically conductive film electrode. The substrate and electrically conductive electrode film are then exposed to ion beam implantation of O+ or N+ ions to impregnate the surface of the metal electrode with O+ or N+ ions. Thereafter, the substrate and electrically conductive film having implanted O+ or N+ ions is annealed so as to stabi-lize the oxide structure which has been implanted into the surface of the electrically conductive film to provide an ultra-thin dielectric film.
AND METHOD FOR MANUFACTURE THEREOF
Abstract A suitable substrate is provided to which is applied a metal electrically conductive film electrode. The substrate and electrically conductive electrode film are then exposed to ion beam implantation of O+ or N+ ions to impregnate the surface of the metal electrode with O+ or N+ ions. Thereafter, the substrate and electrically conductive film having implanted O+ or N+ ions is annealed so as to stabi-lize the oxide structure which has been implanted into the surface of the electrically conductive film to provide an ultra-thin dielectric film.
Description
ULT~A-THIN FILM CAPACITOR
AND METHOD FOR MANUFACTURE THEREOF
Field of the Invention The present invention relates, to an ultra-thin film capacitor having a metal oxide or metal nitride di-electric and to a method of forming an ultra-thin film capacitor.
Background of the Invention The manufacture of thin film capacitors is well ~10 known. One method for the manufacture of thin film capacitors is to first form a thin film of a metal, such as tantalum, as the first'electrode on a di-electric substrate. This composite is then placed in an anodizing bath to form a dielectric layer of _~
tantalum oxide on the tantalum film. This procedure requires a lengthy period of time, th,ereby adding greatly to the'cost of manufacturing a capacitor.
Furthermore, the tantalum oxide formed on the tantalum film by the anodizing technique is defi-cient in oxygen and a relatively thick coating of the tantalum oxide is required to provide acceptable capacitance parameters.
U. S. Patent 4,002,545 to Fehiner et al. describes an improved method of forming a thin film capacitor having a tantalum oxide dielectric. In the method of the Fehiner et al. patent, a non-tantalum elec-trically conductive film is applied to a dielectricsubstrate to form a first capacitor electrode. A
thin film of tantalum is then applied over the electrode to form an electrically conductive duple~
film. The substrate with the applied duplex film is then placed within a vacuum environment containing a mixture of oxygen and an inert gas. A film of tan-talum oxide is R-F sputtered over the duplex film within the vacuum environment. The dielectric substrate and duplex film with the tantalum oxide film applied thereon is then cooled and an electri-cally conductive film is applied over the film of tantalum oxide to form a counter capacitor elec-trode.
It is indicated in the Fehiner et al. patent that 20 the method of the patent cures the problem of oxygen deficiency which is encountered during R-F sputtering of a tantalum oxide film onto a tantalum substrate.
A basic disadvantage of the method of the Fehiner et al. patent and other known methods for making thin 25 film capacitors is that these methods cannot produce a dielectric thickness of less than about 2,000 A
which have suitable characteristics in respect to temperature coefficient of capacitance, leakage and loss, particularly at temperatures-above 200C. The 30 requirement for ultra-thin dielectric films has been accentuated recently due to the desire for increased packing densities. A requirement has been set for thin film capacitors having a dielectric constant (~) to thickness (expressed in Angstrom units) ratio 35 of greater than about 0.04. Since most metal oxides FI 9~79-058 1 1 599 ~8 suitable for use as a dielectric have a dielectric constant of ~rom about 15 to about 60, a thickness oE less than about 1,500 A must be established to meet the E/t requirement of greater than 0.04.
Accordingly, it is an object of this invention to provide an ultra-thin film capacitor of less than about 1500 A and a method of production of ultra-thin film capacitors which will have desired charac-teristics of capacitance, temperature coefficient of capacitance, leakage and loss.
Summary of the Invention Broadly, according to the present invention, a suit-able substrate is provided to which is applied a metal electrically conductive film electrode. The substrate is usually a dielectric or semiconductor material. The substrate and electrically conductive electrode film are then exposed to ion beam implan-tation of O+ or N+ ions to impregnate the surface of the metal with O+ or N+ ions. The ion beam implan-tation of O+ and N+ ions is sufficient to provide astoichiometric excess of O+ or N+ ions. Thereafter, the substrate and electrically conductive film having implanted O+ or N+ ions is annealed under predeter-mined tempera~ure and time conditions to stabilize the oxide structure which has been implanted into the surface of the electrically conductive film.
In an alternate embodiment of the present invention, a metal oxide coating is deposited on the metal coating. The metal oxide coating is then treated with O+ or N+ ion beam implantation. The provision of a metal oxide coating prior to the ion beam implantation step reduces the dosage level and time required to implant the O+ or N+ ions.
~I 9-79-058 Brief Description of the Drawings The principles of the invention will be more readily understood by the detailed description given here-inbelow in conjunction with the drawings which are briefly described below.
FIG. 1 is a schematic flow sheet of the various steps used in the method of the invention to provide ultra-thin film capacitors, FIG; 2 is a side, partially sectioned view of an ultra-thin film capacitor constructed in accordance with the method of the invention, and FIG. 3 is a side, partially sectioned view of an alternate embodiment of an ultra-thin film capacitor constructed in accordance with the method of the invention.
Detailed Description of the Invention It should be noted that the drawings are illustrative and symbolic of the invention and there is no in-tention to indioate scale or relative proportions of the elements shown therein. For ease of description, various aspects of the present invention will be described in connection with the formation of a tantalum oxide film suitable for use as an ultra-thin film dielectric in a capacitor.
Referring to FIG. 2 of the drawings, there is shown a substrate 11, which is usually a dielectric or semiconductor material, to which is applied a metallic electrically conductive thin film electrode 13. The electrode 13 is treated by the method of the invention to provide a layer 15 with implanted O+ or N+ ions.
A counter electrode 17 is applied to the oxide implanted layer 15. In FIG. 3, a metal oxide layer 1'3 is applied to the electrode 13 prior to treatment b~ the method of the invention to provide a layer 15 wi.th implan~ed O~ or N+ ions. In FIG. 3 the implant layer 15 can extend partially through layer 19 as shown in FIG. 3 or it can extend throughout layer 19. It is also possible to drive the implant layer 15 beneath the surface of the metal layer 13 of FIG.
AND METHOD FOR MANUFACTURE THEREOF
Field of the Invention The present invention relates, to an ultra-thin film capacitor having a metal oxide or metal nitride di-electric and to a method of forming an ultra-thin film capacitor.
Background of the Invention The manufacture of thin film capacitors is well ~10 known. One method for the manufacture of thin film capacitors is to first form a thin film of a metal, such as tantalum, as the first'electrode on a di-electric substrate. This composite is then placed in an anodizing bath to form a dielectric layer of _~
tantalum oxide on the tantalum film. This procedure requires a lengthy period of time, th,ereby adding greatly to the'cost of manufacturing a capacitor.
Furthermore, the tantalum oxide formed on the tantalum film by the anodizing technique is defi-cient in oxygen and a relatively thick coating of the tantalum oxide is required to provide acceptable capacitance parameters.
U. S. Patent 4,002,545 to Fehiner et al. describes an improved method of forming a thin film capacitor having a tantalum oxide dielectric. In the method of the Fehiner et al. patent, a non-tantalum elec-trically conductive film is applied to a dielectricsubstrate to form a first capacitor electrode. A
thin film of tantalum is then applied over the electrode to form an electrically conductive duple~
film. The substrate with the applied duplex film is then placed within a vacuum environment containing a mixture of oxygen and an inert gas. A film of tan-talum oxide is R-F sputtered over the duplex film within the vacuum environment. The dielectric substrate and duplex film with the tantalum oxide film applied thereon is then cooled and an electri-cally conductive film is applied over the film of tantalum oxide to form a counter capacitor elec-trode.
It is indicated in the Fehiner et al. patent that 20 the method of the patent cures the problem of oxygen deficiency which is encountered during R-F sputtering of a tantalum oxide film onto a tantalum substrate.
A basic disadvantage of the method of the Fehiner et al. patent and other known methods for making thin 25 film capacitors is that these methods cannot produce a dielectric thickness of less than about 2,000 A
which have suitable characteristics in respect to temperature coefficient of capacitance, leakage and loss, particularly at temperatures-above 200C. The 30 requirement for ultra-thin dielectric films has been accentuated recently due to the desire for increased packing densities. A requirement has been set for thin film capacitors having a dielectric constant (~) to thickness (expressed in Angstrom units) ratio 35 of greater than about 0.04. Since most metal oxides FI 9~79-058 1 1 599 ~8 suitable for use as a dielectric have a dielectric constant of ~rom about 15 to about 60, a thickness oE less than about 1,500 A must be established to meet the E/t requirement of greater than 0.04.
Accordingly, it is an object of this invention to provide an ultra-thin film capacitor of less than about 1500 A and a method of production of ultra-thin film capacitors which will have desired charac-teristics of capacitance, temperature coefficient of capacitance, leakage and loss.
Summary of the Invention Broadly, according to the present invention, a suit-able substrate is provided to which is applied a metal electrically conductive film electrode. The substrate is usually a dielectric or semiconductor material. The substrate and electrically conductive electrode film are then exposed to ion beam implan-tation of O+ or N+ ions to impregnate the surface of the metal with O+ or N+ ions. The ion beam implan-tation of O+ and N+ ions is sufficient to provide astoichiometric excess of O+ or N+ ions. Thereafter, the substrate and electrically conductive film having implanted O+ or N+ ions is annealed under predeter-mined tempera~ure and time conditions to stabilize the oxide structure which has been implanted into the surface of the electrically conductive film.
In an alternate embodiment of the present invention, a metal oxide coating is deposited on the metal coating. The metal oxide coating is then treated with O+ or N+ ion beam implantation. The provision of a metal oxide coating prior to the ion beam implantation step reduces the dosage level and time required to implant the O+ or N+ ions.
~I 9-79-058 Brief Description of the Drawings The principles of the invention will be more readily understood by the detailed description given here-inbelow in conjunction with the drawings which are briefly described below.
FIG. 1 is a schematic flow sheet of the various steps used in the method of the invention to provide ultra-thin film capacitors, FIG; 2 is a side, partially sectioned view of an ultra-thin film capacitor constructed in accordance with the method of the invention, and FIG. 3 is a side, partially sectioned view of an alternate embodiment of an ultra-thin film capacitor constructed in accordance with the method of the invention.
Detailed Description of the Invention It should be noted that the drawings are illustrative and symbolic of the invention and there is no in-tention to indioate scale or relative proportions of the elements shown therein. For ease of description, various aspects of the present invention will be described in connection with the formation of a tantalum oxide film suitable for use as an ultra-thin film dielectric in a capacitor.
Referring to FIG. 2 of the drawings, there is shown a substrate 11, which is usually a dielectric or semiconductor material, to which is applied a metallic electrically conductive thin film electrode 13. The electrode 13 is treated by the method of the invention to provide a layer 15 with implanted O+ or N+ ions.
A counter electrode 17 is applied to the oxide implanted layer 15. In FIG. 3, a metal oxide layer 1'3 is applied to the electrode 13 prior to treatment b~ the method of the invention to provide a layer 15 wi.th implan~ed O~ or N+ ions. In FIG. 3 the implant layer 15 can extend partially through layer 19 as shown in FIG. 3 or it can extend throughout layer 19. It is also possible to drive the implant layer 15 beneath the surface of the metal layer 13 of FIG.
2 by use of higher energy. In this embodiment, a dielectric layer 15 is formed in situ between the electrode 13 and a counter electrode 17.
As indicated in the discussion of the background of the invention, the provision of an ultra-thin di-electric film is related to high density computercircuit requirements ~or an ~/t ratio of greater than 0.04. From the required relationshipl it can be seen that those metal oxide dielectrics having a dielectric constant of 15 would require a thickness of less than 375 A. As used herein, the symbol "A" is used to designate Angstrom units. It is preferred to use metal oxides having a dielectric constant of at least about 20 requiring a minimum thickness of less than about 500 A.
Preferred metal oxides for use as the dielectric material of the present invention are those rare earth and transition metal oxides having a dielec-tric co~stant in excess of 15 and which can be converted to an amorphous structure during ion implantation treatment. Particularly preferred metal oxides for use as the dielectric are tantalum oxide, niobium oxide, titanium oxide and vanadium oxide. Hafnium oxide and zirconium oxide have de-sirable dielectric constants of about 30 but do not form amorphous structures on ion implant treatment FI 9-79-05~
~ 1 59gl3 in accordance with the invention. The desirability oE forming an amorphous structure during ion implant treatment is discussed hereinbelow under the step of forming the metal oxide coating by R-F sputtering.
Referring now to FIG. 1, the first step in the prep-aration of an ultra-thin film capacitor in accordance with the invention is to form a metal electrically conductive thin film electrode 13 on the surface of a substrate 11. The electrode 13 preferably has a thickness of from about 500 to about 10,000 A. The metal chosen for the electrically conductive thin film electrode 13 should be compatible with the metal oxide film 19 (if used) which is deposited in an alternate embodiment by a step to be described hereinbelow.
If a metal oxide deposition step is not used, the metal electrode 13 is next subjected to ion beam implantation. The dose requirements for effecting ion beam implantation of O+ or N+ ions to the de-sired thickness on the surface of the metal electrode13 are quite high and are generally within the range of from about 5 x 1016 to about 5 x 1017. An energy level of from about 1 keV to about 50 keV can be used for ion implantation. At a current level of 150~amp, a time of from about 4 to 20 hours is re-quired to attain the required dosage. The use of higher current levels would reduce the time re~uired to obtain the required dosage.
As indicated, either O~ or N~ ions can be used for 30 this step to provide either an oxide or nitride coating on the surface of the electrode 13. The ion beam implantation is continued until the desired dosage of oxide or nitride coating is implanted on the surface of the thin film electrode 13. For 1 1~9918 tantalum having a dielectric constant of 25, the thickness of the coating should be less than about 6~5 A to meet the /t requirement of greater than 0.04.
D~lring ion implantation in the metal, the surface of the metal is sputtered off due to the high dosage requirement. During the at~ainment of an ion im-plant depth of about 600 A, the surface sputtering will remove from about 500 A to about 1,000 A of the metal.
It has been determined that the dosage requirements and the time ~or effecting ion beam implantation can be greatly reduced if a metal oxide film is first formed on the surface of the thin film electrode 13.
The metal used to form the thin film electrode should be compatible with the metal oxide which is formed thereon. The metal will usually be the metal of the metal oxide coating, however, other metals or polycrystalline Si electroaes can be utilized for certain purposes. The metal oxide coating is formed on the electrode 13 by any suitable method, such as R-F sputtering.
In a preferred method for forming the metal oxide coating, the composite formed by coating the elec-trode 13 on the dielectric substrate 11 is disposedwithin a typical R-F sputtering apparatus (not shown) having a target material of the desired metal oxide. The desired metal oxide can also be formed by reactive deposition of the metal in an Ar/O2 gas mixture having a sufficiently high level of oxygen.
During R-F sputtering in vacuum, a quantity of a mixtuxe of an inert ionizable gas and oxygen is introduced into the R-F sputtering apparatus. Gen-erally, the proportions of the oxygen and inert gas FI 9-79-~58 are from about 2 to about 5G% by volume of oxygen and from about 50 to about 98~ by volume of the inert gas. Suitable inert gases include argon, xenon, krypton or the like.
In accordance with known technology, sputtering of a metal oxide in an oxygen containing vacuum environ-ment cures the non-stoichiometric condition encoun-tered during R-F sputtering of a metal oxide; that is, the resulting metal oxide layer or film is significantly less oxygen deficient. However, the metal oxide film formed by RF sputtering can exhibit local regions with crystalline structure, which causes high current flow through the crystallites of the structure. The process of the present invention wherein O+ or N+ is implanted within the metal oxide coating changes the crystalline structure to an amorphous structure. An amorphous structure is highly desirable to provide suitable capacitor parameters. It is known that the structure provided 20 by anodizing a metal oxide dielectric onto the sur-face of a metal is an amorphous structure. However, anodized films have entrapment and corrosion problems when used at the thickness required by the ultra-thin film capacitors of the present in~ention.
25 After the metal oxide film is coated onto the metal electrode 13, the composite structure is subjected to ion beam implantation as set forth in the discus-sion of the capacitor formed using only the metal electrode. The dosage requirements to effect suffi-30 cient O+ or N~ ion implantation are significantlyreduced with the use of a metal oxide film and a power setting of from about 1 to about 50 keV at a current level of 150~amp for a period of from about 1 minute to about 2 hours is sufficient. For this 35 reason, the use o~ the metal oxide coating prior to J 159gl8 g ion beam treatment is preferred. Preferakly the ion beam implantation of O+ or N+ ions for this embodi-ment is continued until the dosage i5 in the range of from about 1 x 1014 to about 1 x 1016 ions/cm2.
Higher dosage levels can be used but do not provide any significant benefits.
After subjecting the composite structure to ion beam implantation, the composite structure is transferred to an annealing oven. It has been determined that an annealing step sets the ions which have been im-planted into the surface of the composite structure and greatly enhances the stability o the capacitor during operation. Annealing conditions of from about 150 to about 400C in an oxygen ambient for O+
ion implantation and a nitrogen ambient for N+ ion implantation for a period of from about 1 to about 5 hours are suitable to affect annealing and healing of the surface damage caused,by ion beam implan-tation.
Examples The following examples further illustrate various features of the invention but are intended to in no way limit the scope of the invention which is de-fined in the appended claims.
E-xample 1 An ultra-thin film capacitor having the configuration of FIG. 2 was prepared.
A thin film of tantalum was sputtered~onto a silicon dioxide substrate. The thickness of the tantalum 30 film was about 2,500 A. The composite structure having the tantalum film thereon was exposed to O~
I 1 5~91~
ion be~m implantation. The exposure was at an ion beam energy of 30 keV for 10 hours. At the end of the ion beam exposure a film of about 600 A having an O+ concentration of 1.4 x 1017ions/cm2 had been formed. The structure was then annealed in air at a t~mperature of 400C for a period of 60 minutes to stabilize the implanted film.
A counter electrode of aluminum was then applied to the composite structure by vacuum deposition. The counter electrode had a thickness of 5,000 A.
The resulting capacitor had a capacitance of about 600 pF or ~3.35 x 10 15 -2 and a breakdown voltage o~ about 5 V. Breakdown~voltage is defined as that voltage necessary to produce a leakage current equal to or greater than 10 4 amp. The leakage current at 1 volts was about 10 9 amp.
Example 2 An ultra-thin film capacitor was made in accordance with the structure of FIG. 3. A tantalum coated silicon dioxide dielectric was formed as discussed in Example 1. The composite structure was placed in an R-F sputtering appaxatus. The composite struc-ture was exposed to a tantalum oxide target after a vacuum of about 10 6 Torr was drawn. A quantity of 25 a mixture of oxygen and argon gas was introduced into the apparatus until the vacuum enviroD ent reached 5 x 10 3 Torr. The oxygen-inert gas mixture contained about 10~ by volume of oxygen. The R-F
sputtering apparatus was adjusted to energize the 30 tantalum oxide target and sputtering was continued until a layer of tantalum oxide having a thickness of 500 A was obtained.
I lS9gl8 --11~
The tantalum oxide film was then exposed to O~ ion beam treatment at 30 keV for about 30 minutes to produce a uniform amorphous oxide layer. The ion beam treatment was sufficient to implant 2 x 1015 ions/cm2.
The structure was then annealed in oxygen at a temperature of 200C for a period of 60 minutes to complete the oxidization and stabilize the struc-ture. Thereafter samples with both aluminum and gold counter electrodes were pr~pared having a thickness of 5,000 A by vacuum evaporation.
The resulting capacitor had a capacitance of 875 pfd and a breakdown voltage of about 5 volts. The leakage current at 1 volt was less than 10 10 amp for Au electrode samples; samples with Al electrodes yielded higher leakage (10 9~. The O+ implanted Ta2O5 samples with Au electrodes were stable and yielded low leakage (~10 11 amp at 1 volt) following a 300C anneal treatment. This high temperature stability is an important property for capacitors to withstand processing temperatures.
Although the present invention has been described with respect to details of certain embodiments thereof it is not intended that such details be limitations on the scope of the-claims except insofar as set forth in the following claims.
~I 9-79~058
As indicated in the discussion of the background of the invention, the provision of an ultra-thin di-electric film is related to high density computercircuit requirements ~or an ~/t ratio of greater than 0.04. From the required relationshipl it can be seen that those metal oxide dielectrics having a dielectric constant of 15 would require a thickness of less than 375 A. As used herein, the symbol "A" is used to designate Angstrom units. It is preferred to use metal oxides having a dielectric constant of at least about 20 requiring a minimum thickness of less than about 500 A.
Preferred metal oxides for use as the dielectric material of the present invention are those rare earth and transition metal oxides having a dielec-tric co~stant in excess of 15 and which can be converted to an amorphous structure during ion implantation treatment. Particularly preferred metal oxides for use as the dielectric are tantalum oxide, niobium oxide, titanium oxide and vanadium oxide. Hafnium oxide and zirconium oxide have de-sirable dielectric constants of about 30 but do not form amorphous structures on ion implant treatment FI 9-79-05~
~ 1 59gl3 in accordance with the invention. The desirability oE forming an amorphous structure during ion implant treatment is discussed hereinbelow under the step of forming the metal oxide coating by R-F sputtering.
Referring now to FIG. 1, the first step in the prep-aration of an ultra-thin film capacitor in accordance with the invention is to form a metal electrically conductive thin film electrode 13 on the surface of a substrate 11. The electrode 13 preferably has a thickness of from about 500 to about 10,000 A. The metal chosen for the electrically conductive thin film electrode 13 should be compatible with the metal oxide film 19 (if used) which is deposited in an alternate embodiment by a step to be described hereinbelow.
If a metal oxide deposition step is not used, the metal electrode 13 is next subjected to ion beam implantation. The dose requirements for effecting ion beam implantation of O+ or N+ ions to the de-sired thickness on the surface of the metal electrode13 are quite high and are generally within the range of from about 5 x 1016 to about 5 x 1017. An energy level of from about 1 keV to about 50 keV can be used for ion implantation. At a current level of 150~amp, a time of from about 4 to 20 hours is re-quired to attain the required dosage. The use of higher current levels would reduce the time re~uired to obtain the required dosage.
As indicated, either O~ or N~ ions can be used for 30 this step to provide either an oxide or nitride coating on the surface of the electrode 13. The ion beam implantation is continued until the desired dosage of oxide or nitride coating is implanted on the surface of the thin film electrode 13. For 1 1~9918 tantalum having a dielectric constant of 25, the thickness of the coating should be less than about 6~5 A to meet the /t requirement of greater than 0.04.
D~lring ion implantation in the metal, the surface of the metal is sputtered off due to the high dosage requirement. During the at~ainment of an ion im-plant depth of about 600 A, the surface sputtering will remove from about 500 A to about 1,000 A of the metal.
It has been determined that the dosage requirements and the time ~or effecting ion beam implantation can be greatly reduced if a metal oxide film is first formed on the surface of the thin film electrode 13.
The metal used to form the thin film electrode should be compatible with the metal oxide which is formed thereon. The metal will usually be the metal of the metal oxide coating, however, other metals or polycrystalline Si electroaes can be utilized for certain purposes. The metal oxide coating is formed on the electrode 13 by any suitable method, such as R-F sputtering.
In a preferred method for forming the metal oxide coating, the composite formed by coating the elec-trode 13 on the dielectric substrate 11 is disposedwithin a typical R-F sputtering apparatus (not shown) having a target material of the desired metal oxide. The desired metal oxide can also be formed by reactive deposition of the metal in an Ar/O2 gas mixture having a sufficiently high level of oxygen.
During R-F sputtering in vacuum, a quantity of a mixtuxe of an inert ionizable gas and oxygen is introduced into the R-F sputtering apparatus. Gen-erally, the proportions of the oxygen and inert gas FI 9-79-~58 are from about 2 to about 5G% by volume of oxygen and from about 50 to about 98~ by volume of the inert gas. Suitable inert gases include argon, xenon, krypton or the like.
In accordance with known technology, sputtering of a metal oxide in an oxygen containing vacuum environ-ment cures the non-stoichiometric condition encoun-tered during R-F sputtering of a metal oxide; that is, the resulting metal oxide layer or film is significantly less oxygen deficient. However, the metal oxide film formed by RF sputtering can exhibit local regions with crystalline structure, which causes high current flow through the crystallites of the structure. The process of the present invention wherein O+ or N+ is implanted within the metal oxide coating changes the crystalline structure to an amorphous structure. An amorphous structure is highly desirable to provide suitable capacitor parameters. It is known that the structure provided 20 by anodizing a metal oxide dielectric onto the sur-face of a metal is an amorphous structure. However, anodized films have entrapment and corrosion problems when used at the thickness required by the ultra-thin film capacitors of the present in~ention.
25 After the metal oxide film is coated onto the metal electrode 13, the composite structure is subjected to ion beam implantation as set forth in the discus-sion of the capacitor formed using only the metal electrode. The dosage requirements to effect suffi-30 cient O+ or N~ ion implantation are significantlyreduced with the use of a metal oxide film and a power setting of from about 1 to about 50 keV at a current level of 150~amp for a period of from about 1 minute to about 2 hours is sufficient. For this 35 reason, the use o~ the metal oxide coating prior to J 159gl8 g ion beam treatment is preferred. Preferakly the ion beam implantation of O+ or N+ ions for this embodi-ment is continued until the dosage i5 in the range of from about 1 x 1014 to about 1 x 1016 ions/cm2.
Higher dosage levels can be used but do not provide any significant benefits.
After subjecting the composite structure to ion beam implantation, the composite structure is transferred to an annealing oven. It has been determined that an annealing step sets the ions which have been im-planted into the surface of the composite structure and greatly enhances the stability o the capacitor during operation. Annealing conditions of from about 150 to about 400C in an oxygen ambient for O+
ion implantation and a nitrogen ambient for N+ ion implantation for a period of from about 1 to about 5 hours are suitable to affect annealing and healing of the surface damage caused,by ion beam implan-tation.
Examples The following examples further illustrate various features of the invention but are intended to in no way limit the scope of the invention which is de-fined in the appended claims.
E-xample 1 An ultra-thin film capacitor having the configuration of FIG. 2 was prepared.
A thin film of tantalum was sputtered~onto a silicon dioxide substrate. The thickness of the tantalum 30 film was about 2,500 A. The composite structure having the tantalum film thereon was exposed to O~
I 1 5~91~
ion be~m implantation. The exposure was at an ion beam energy of 30 keV for 10 hours. At the end of the ion beam exposure a film of about 600 A having an O+ concentration of 1.4 x 1017ions/cm2 had been formed. The structure was then annealed in air at a t~mperature of 400C for a period of 60 minutes to stabilize the implanted film.
A counter electrode of aluminum was then applied to the composite structure by vacuum deposition. The counter electrode had a thickness of 5,000 A.
The resulting capacitor had a capacitance of about 600 pF or ~3.35 x 10 15 -2 and a breakdown voltage o~ about 5 V. Breakdown~voltage is defined as that voltage necessary to produce a leakage current equal to or greater than 10 4 amp. The leakage current at 1 volts was about 10 9 amp.
Example 2 An ultra-thin film capacitor was made in accordance with the structure of FIG. 3. A tantalum coated silicon dioxide dielectric was formed as discussed in Example 1. The composite structure was placed in an R-F sputtering appaxatus. The composite struc-ture was exposed to a tantalum oxide target after a vacuum of about 10 6 Torr was drawn. A quantity of 25 a mixture of oxygen and argon gas was introduced into the apparatus until the vacuum enviroD ent reached 5 x 10 3 Torr. The oxygen-inert gas mixture contained about 10~ by volume of oxygen. The R-F
sputtering apparatus was adjusted to energize the 30 tantalum oxide target and sputtering was continued until a layer of tantalum oxide having a thickness of 500 A was obtained.
I lS9gl8 --11~
The tantalum oxide film was then exposed to O~ ion beam treatment at 30 keV for about 30 minutes to produce a uniform amorphous oxide layer. The ion beam treatment was sufficient to implant 2 x 1015 ions/cm2.
The structure was then annealed in oxygen at a temperature of 200C for a period of 60 minutes to complete the oxidization and stabilize the struc-ture. Thereafter samples with both aluminum and gold counter electrodes were pr~pared having a thickness of 5,000 A by vacuum evaporation.
The resulting capacitor had a capacitance of 875 pfd and a breakdown voltage of about 5 volts. The leakage current at 1 volt was less than 10 10 amp for Au electrode samples; samples with Al electrodes yielded higher leakage (10 9~. The O+ implanted Ta2O5 samples with Au electrodes were stable and yielded low leakage (~10 11 amp at 1 volt) following a 300C anneal treatment. This high temperature stability is an important property for capacitors to withstand processing temperatures.
Although the present invention has been described with respect to details of certain embodiments thereof it is not intended that such details be limitations on the scope of the-claims except insofar as set forth in the following claims.
~I 9-79~058
Claims (10)
1. A method for manufacture of an ultra-thin film capacitor comprising:
providing a substrate;
applying to said substrate a metal electrically conductive film to form a composite having a first capacitor electrode;
applying, by sputtering, a film selected from the group consisting of metal oxide films and metal nitride films to the surface of said first electrode;
subjecting the surface of said metal oxide and metal nitride film to ion implantation treatment to implant ions selected from the group consisting of O+ and N+ ions in the surface of said first electrode;
subjecting said composite to annealing heat treatment to provide an ultra-thin dielectric film adjacent the surface of said first electrode; and applying an electrically conductive film to said composite to form a counter capacitor electrode.
providing a substrate;
applying to said substrate a metal electrically conductive film to form a composite having a first capacitor electrode;
applying, by sputtering, a film selected from the group consisting of metal oxide films and metal nitride films to the surface of said first electrode;
subjecting the surface of said metal oxide and metal nitride film to ion implantation treatment to implant ions selected from the group consisting of O+ and N+ ions in the surface of said first electrode;
subjecting said composite to annealing heat treatment to provide an ultra-thin dielectric film adjacent the surface of said first electrode; and applying an electrically conductive film to said composite to form a counter capacitor electrode.
2. A method for manufacture of an ultra-thin film capacitor comprising:
providing a substrate, applying to said substrate a metal electrically conductive film to form a composite having a first capacitor electrode, applying by sputtering a film selected from the group consisting of metal oxide films and metal nitride films to the surface of said first electrode, the metal of said metal oxide or metal nitride films is selected from the group consisting of tantalum, niobium, titanium, vanadium, hafnium, and zirconium;
subjecting the surface of said metal oxide or metal nitride film to ion implantation treatment to implant ions selected from the group consisting of O+ and N+ ions in the surface of said metal oxide or metal nitride film to form a metal oxide or metal nitride layer having a dielectric constant of from about 15 to about 60;
subjecting said composite to annealing heat treatment of from about 150°C to about 400°C for a period of from about 1 to about 5 hours in an ambient atmosphere selected from oxygen and nitrogen to provide an ultra-thin dielectric film having a dielectric constant to film thickness (expressed in Angstroms) ratio of greater than 0.04, adjacent the surface of said first electrode, and applying a metal electrically conductive film to said composite to form a counter capacitor electrode.
providing a substrate, applying to said substrate a metal electrically conductive film to form a composite having a first capacitor electrode, applying by sputtering a film selected from the group consisting of metal oxide films and metal nitride films to the surface of said first electrode, the metal of said metal oxide or metal nitride films is selected from the group consisting of tantalum, niobium, titanium, vanadium, hafnium, and zirconium;
subjecting the surface of said metal oxide or metal nitride film to ion implantation treatment to implant ions selected from the group consisting of O+ and N+ ions in the surface of said metal oxide or metal nitride film to form a metal oxide or metal nitride layer having a dielectric constant of from about 15 to about 60;
subjecting said composite to annealing heat treatment of from about 150°C to about 400°C for a period of from about 1 to about 5 hours in an ambient atmosphere selected from oxygen and nitrogen to provide an ultra-thin dielectric film having a dielectric constant to film thickness (expressed in Angstroms) ratio of greater than 0.04, adjacent the surface of said first electrode, and applying a metal electrically conductive film to said composite to form a counter capacitor electrode.
3. A method in accordance with claim 1 or claim 2 wherein said metal oxide or metal nitride layer formed by ion implantation is selected from the group consisting of rare earth and transition metal oxides and nitrides having a dielectric constant in excess of 15.
4. A method in accordance with claim 1 wherein the metal of said metal oxide or metal nitride layer formed by ion implantation treatment is selected from the group consisting of tantalum, niobium, titanium, vanadium, hafnium and zirconium.
5. A method in accordance with claim 1 wherein the dielectric constant to thickness ratio of said dielectric film formed by ion implantation treatment is greater than 0.04.
6. A method in accordance with claim 1 or claim 2 wherein the dosage level of ion implantation treatment is such as to implant from 5 x 1016 to 5 x 1017 ions/cm2.
7. A method in accordance with claim 1 or claim 2 wherein said ion implantation treatment is sufficient to implant ions at a level of from about 1014 to 1016 ions/cm2.
8. The method of claim 1 wherein said applying said first electrode is in an oxygen containing vacuum environment.
9. The method of claim 2 wherein said applying by sputtering is in an oxygen containing vacuum environment.
10. The method of claim 8 or claim 9 wherein said oxygen containing environment is about 2 to 50 percent by volume with the remaining gaseous volume being composed of an inert gas.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US8971079A | 1979-10-30 | 1979-10-30 | |
| US089,710 | 1979-10-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1159918A true CA1159918A (en) | 1984-01-03 |
Family
ID=22219201
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000358899A Expired CA1159918A (en) | 1979-10-30 | 1980-08-25 | Ultra-thin film capacitor and method for manufacture thereof |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0027885B1 (en) |
| JP (1) | JPS6030092B2 (en) |
| AT (1) | ATE8312T1 (en) |
| CA (1) | CA1159918A (en) |
| DE (1) | DE3068441D1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62193275A (en) * | 1986-02-12 | 1987-08-25 | シ−メンス、アクチエンゲゼルシヤフト | Three-dimensional one transistor cell device and manufactureof the same |
| JPH01225149A (en) * | 1988-03-04 | 1989-09-08 | Toshiba Corp | Capacitor and manufacture thereof |
| US5175518A (en) * | 1991-10-15 | 1992-12-29 | Watkins-Johnson Company | Wide percentage bandwidth microwave filter network and method of manufacturing same |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4000055A (en) * | 1972-01-14 | 1976-12-28 | Western Electric Company, Inc. | Method of depositing nitrogen-doped beta tantalum |
| US4038167A (en) * | 1976-02-09 | 1977-07-26 | Corning Glass Works | Method of forming a thin film capacitor |
-
1980
- 1980-08-01 JP JP55105181A patent/JPS6030092B2/en not_active Expired
- 1980-08-25 CA CA000358899A patent/CA1159918A/en not_active Expired
- 1980-09-15 EP EP80105497A patent/EP0027885B1/en not_active Expired
- 1980-09-15 AT AT80105497T patent/ATE8312T1/en not_active IP Right Cessation
- 1980-09-15 DE DE8080105497T patent/DE3068441D1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0027885A1 (en) | 1981-05-06 |
| DE3068441D1 (en) | 1984-08-09 |
| JPS5667919A (en) | 1981-06-08 |
| EP0027885B1 (en) | 1984-07-04 |
| JPS6030092B2 (en) | 1985-07-15 |
| ATE8312T1 (en) | 1984-07-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4333808A (en) | Method for manufacture of ultra-thin film capacitor | |
| US6514814B2 (en) | Capacitor containing amorphous and polycrystalline ferroelectric films and fabrication method therefor, and method for forming amorphous ferroelectric film | |
| US5973911A (en) | Ferroelectric thin-film capacitor | |
| Lee et al. | Microstructure dependence of electrical properties of (Ba0. 5Sr0. 5) TiO3 thin films deposited on Pt/SiO2/Si | |
| Hwang et al. | Deposition of extremely thin (Ba, Sr) TiO3 thin films for ultra‐large‐scale integrated dynamic random access memory application | |
| US6075691A (en) | Thin film capacitors and process for making them | |
| EP0826237B1 (en) | METHOD OF FORMING A Ta205 DIELECTRIC LAYER | |
| US4364099A (en) | Tantalum thin film capacitor | |
| US6018454A (en) | Metallized film, a production method thereof, and a capacitor using it | |
| Belii et al. | Formation of chemical compounds by ion bombardment of thin transition metal films | |
| Roberts et al. | Selective Studies of Crystalline Ta2 O 5 Films | |
| Belkind et al. | Optical properties of RuO2 films deposited by reactive sputtering | |
| EP0166205B1 (en) | Method of producing electrolytic capacitor with al-ti anode body | |
| CA1159918A (en) | Ultra-thin film capacitor and method for manufacture thereof | |
| Shen et al. | Oxygen-related dielectric relaxation and leakage characteristics of Pt/(Ba, Sr) TiO 3/Pt thin-film capacitors | |
| US5948216A (en) | Method for making thin film tantalum oxide layers with enhanced dielectric properties and capacitors employing such layers | |
| EP0079437B1 (en) | Thin film capacitor | |
| Hwang et al. | Variations of the leakage current density and the dielectric constant of Pt/(Ba, Sr) TiO 3/Pt capacitors by annealing under a N 2 atmosphere | |
| KR102276021B1 (en) | Method of manufacturing a strontium titanate based dielectric layer having high dielectric constant and low leakage current density and method of manufacturing a capacitor including the strontium titanate based dielectric layer | |
| Campbell | Electrolytic capacitors | |
| US3502949A (en) | Thin film solid electrolyte capacitor | |
| JPH059710A (en) | Production of aluminum electrode for electrolytic capacitor | |
| JP3597217B2 (en) | Method of forming dielectric film | |
| JPS60107838A (en) | Manufacture of semiconductor device | |
| JPH0367346B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |