US3645695A - Furnace apparatus for blocking sodium ions - Google Patents

Furnace apparatus for blocking sodium ions Download PDF

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US3645695A
US3645695A US866185A US3645695DA US3645695A US 3645695 A US3645695 A US 3645695A US 866185 A US866185 A US 866185A US 3645695D A US3645695D A US 3645695DA US 3645695 A US3645695 A US 3645695A
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furnace tube
mobile
metal film
insulator layer
silicon dioxide
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US866185A
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Ronald L Koepp
Stanley J Dudkowski
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NCR Voyix Corp
National Cash Register Co
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NCR Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F27D11/02—Ohmic resistance heating
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/0014—Devices wherein the heating current flows through particular resistances
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S148/00—Metal treatment
    • Y10S148/006—Apparatus
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S148/00—Metal treatment
    • Y10S148/053—Field effect transistors fets
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S148/00—Metal treatment
    • Y10S148/118—Oxide films

Definitions

  • ABSTRACT The present invention relates to a processing apparatus for growing and annealing a silicon dioxide insulator layer to obtain a mobile positive ion free silicon dioxide insulator layer, A mobile positive ion free silicon dioxide insulator layer is required in order to make a stable insulated gate field effect transistor.
  • the processing apparatus comprises a nonoxidizing high-melting-point platinum metal film coated quartz fumuce tube, potential means for placing a positive potential upon the platinum metal film coating of the platinum metal film coated quartz furnace tube to repel mobile ions therefrom, heater means for heating the interior of the quartz furnace tube, and gas means for passing oxygen gas through the platinum metal film coated quartz furnace tube.
  • a silicon wafer may be oxidized in said processing apparatus to form a relatively mobile positive ion free silicon dioxide insulator layer of an insulated gate field effect transistor upon the silicon wafer.
  • the silicon dioxide insulator layer is relatively uncontaminated by mobile positive ions which exist to the outside of the platinum metal film coated quartz furnace tube.
  • a silicon wafer which previously has been coated by a silicon dioxide insulator layer may be processed to remove mobile ions within the silicon dioxide insulator layer.
  • Mobile positive ions are repelled by the positive potential applied to the platinum metal film away from the outside of the quartz furnace tube, and mobile positive ions of the silicon dioxide insulator layer within the platinum metal film coated quartz tube are removed by the flowing oxygen gas due to the low-vapor pressure of the mobile positive ions.
  • Goetzberger does not disclose a metal film coated quartz furnace tube having a positive potential applied to the metal film to repel positive ions away from the exterior of the metal film and to allow a flowing oxidation gas to absorb positive ions from within a silicon dioxide layer.
  • Goetzberger has only a penetrable positive potential around a silicon wafer, by setting up an electric field between a positively charged wire electrode and the negatively charged wafer.
  • a potential difference is not set up between the metal film coating of a metal film coated quartz furnace tube and a silicon wafer, but the silicon wafer exists within a positive equipotential closed metal film.
  • the silicon wafer is not subjected to an electric field during its oxidation or during its annealing, but both during oxidation and during annealing, positive ions that may exist to the outside of the metal film coated quartz furnace tube are repelled and prevented from entering the metal film coated quartz furnace tube, as a result of a positive potential existing upon the metal film coating of the metal film coated quartz furnace tube with respect to ground.
  • positive ions are prevented from diffusing through the metal coated quartz furnace tube and combining with a silicon dioxide insulator layer during its formation upon the silicon wafer. Positive ions are also prevented from diffusing through the metal film coated quartz furnace tube to combine with a silicon dioxide insulator layer during its annealing. During annealing of the silicon dioxide insulator layer, positive ions emitted from the silicon dioxide insulator layer are absorbed in a flowing oxidation gas which is passed through the interior of the metal film coated quartz furnace tube.
  • the positively charged wire electrode of Goetzberger repels some positive ions that exist on the outside of the area between the positively charged wire electrode and the negatively charged silicon wafer, but does not repel positive ions which get into said area. In fact, positive ions which get into said area are absorbed by the negatively charged silicon wafer.
  • the processing apparatus of the present invention hinders the combination of positive ions which may enter within the metal-film-coated quartz furnace tube with a silicon dioxide insulator layer therein, due to the flushing of the metal-filmcoated quartz furnace tube with oxygen gas.
  • FIG. 1 is a perspective view of the processing apparatus of the present invention used as an annealing furnace.
  • FIG. 2 is a cross-sectional view of an externally coate processing furnace tube.
  • FIG. 5 is a cross-sectional view of an MOS field effect transistor having a positive sodium ion free silicon dioxide insulator layer.
  • FIG. 1 shows a processing apparatus for annealing a silicon dioxide insulator layer to deplete the concentration of positive ions therein.
  • a 0.5-centimeter-thick furnace tube 12 has evaporated upon its inner surface 13 a 700- Angstrom-thick nonoxidizing, high-melting-point metal film 14 to form an inner wall therein.
  • the metal film 14 is preferably a platinum or rhodium film.
  • a tantalum or titanium film, with an oxygen-impervious silicon nitride layer thereon can be used.
  • the metal film 14, even through being an evaporated amorphous film on the furnace tube I2, is a good barrier to the passage of mobile ions, such as mobile positive sodium ions, due to its crystal structure.
  • a metal film 14 has been found to be necessary to make a resistively heated furnace tube, such as a quartz, aluminum oxide, silicon carbide, or silicon nitride furnace tube, impervious to ions, such as positive sodium ions, at high temperature.
  • a resistively heated furnace tube 12 will reach a temperature of approximately 1,100 C., at which temperature it is porous to positive sodium ions. That is, sodium ions are highly mobile in diffusing through the crystalline structure of the furnace tube 12.
  • a platinum film 14 should be as thick as 600 Angstroms to stop most of the mobile ions from getting therethrough. However, a thinner film would be fairly effective in stopping mobile ions. An evaporated platinum film 14 which is made thicker than 600 Angstroms is increasingly effective in stopping mobile ions. An evaporated platinum film 14 which is thicker than 6,000 Angstroms begins to peel from the quartz furnace tube 12. Therefore, a platinum film 14 which is between 600 and 6,000 Angstroms thick is preferred.
  • a platinum film 8 may be evaporated on the outside of a quartz furnace tube 6.
  • a platinum film 8 which is between 600 and 6,000 Angstroms thick is effective in stopping mobile ions from entering the interior of the quartz furnace tube 6.
  • mobile ions are located in the quartz furnace tube 6 itself, it is preferable that a platinum film be on the inside of the quartz furnace tube 6.
  • the platinum film 14 being on the inner surface of the fumace tube 12, hinders the mobile positive sodium ions within the wall of the furnace tube itself from diffusing into the interior of the furnace tube 12 at high temperature.
  • the platinum film 14 does not melt at 1,100 C. and does not oxidize at 1,100 C. in an oxidizing atmosphere.
  • Gold which also is a metal, melts near 1,063 C. Therefore, gold cannot be used to coat a quartz furnace tube 12 which is heated to 1,100 C.
  • Silver also melts below 1,100 C.
  • a copper film melts below 1,l00 C. Therefore a copper film may not be used to form a nonporous barrier to the passage of mobile ions into the interior of the quartz processing furnace tube 12 when it is used in a high-temperature oxidation processing apparatus.
  • a tantalum film 10 may be evaporated upon the inside surface of a quartz furnace tube 9.
  • the tantalum film l0 oxidizes in an oxidizing atmosphere, at 1,l00 C.
  • a layer 11 impervious to oxygen at high temperature such as a silicon nitride layer, is placed upon the exposed surface of the 700-Angstrom-thick tantalum film 10.
  • the silicon nitride layer 11 prevents oxygen in the interior of the tantalum-coated quartz furnace tube 9 from oxidizing the tantalum film 10.
  • the tantalum film 10 on the inner surface of the quartz furnace tube 9 prevents mobile ions from entering the interior of the quartz furnace tube 9.
  • a metal film is preferred for use in the processing apparatus of the present invention which has no mobile ions, has a highmelting point, and does not oxidize at a high temperature.
  • a platinum film is a very good metal film which has these properties.,Its atomic crystalline structure is fine enough to stop mobile ions from passing through it at high temperature.
  • the platinum film 14 having been evaporated is an amorphous platinum film.
  • the evaporation causes the platinum film, which is evaporated on the inside of a quartz tube, to be amorphous.
  • the evaporated film 14, being semicrystalline, is impervious to mobile ions.
  • a solid metal furnace tube such as a platinum furnace tube
  • a solid platinum furnace tube is impervious to mobile ions, such as mobile positive sodium ions, at a temperature of 1,100" C.
  • the inner wall of a solid platinum furnace tube is, of course, composed of a metal.
  • a battery 18 is attached to the end of the platinum film 14 by means of a lead 16.
  • the edge of the platinum film 14 will reach a temperature of only about 100 C., since it is notdirectly under the radiant heating coil 30.
  • the battery 18 applied a positive 500 volts potential, with respect to ground, to the 700-Angstrom-thick platinum film 14.
  • a silicon wafer holder 22 is laid within the platinum coated quartz furnace tube 12.
  • a silicon wafer 24, havinga 1,200- Angstrom-thick silicon oxide insulator layer 26, is held by the silicon wafer holder 22 within the platinum coated quartz furnace tube 12.
  • the resistance heating coil 30 is placed around the outside of the platinum-coated quartz furnace tube 12.
  • the platinum film 14 is held at a positive 500 volts with respect to ground. Heat from the' radiant heating coil 30, which is driven by an AC power source 34, raises the temperature of the silicon wafer 24 within the center of the platinumcoated quartz furnace tube to 600 C. A 100 cc./minute flowing oxygen gas from an oxygen container is passed through 95 C. water 32 within a container 33, and then through the platinum-coated quartz furnace tube 12 while it is being heated, for 60 minutes.
  • a 14-fold reduction in the number of mobile positive ions, including mobile positive sodium ions, within the silicon oxide insulator layer 26 is achieved, using a positively charged platinum-coated quartz furnace tube 12, over what can be obtained using an uncoated quartz furnace tube.
  • a threefold reduction in the number of mobile positive ions, including mobile positive sodium ions is achieved with the use of a positively charged platinum-coated quartz furnace tube 12, over what can be obtained with the use of an uncharged platinumcoated quartz furnace tube 12..
  • FIG. 4 shows a processing apparatus for oxidizing semiconductor material in a mobile-positive-ion-free furnace tube 40.
  • a platinum-coated quartz furnace tube 40 is positioned by a suitable means within a resistance heating coil 42.
  • a 700-Angstrom-thick platinum film 44 is evaporated upon the inside surface 45 of the quartz furnace tube 40.
  • Oxygen gas is pased through the quartz furnace tube 40 from an oxygen container 48 at the rate of 300 cc./minute.
  • Radiant heat, from the resistance heating coil 42 which is driven by an AC power source 50, raises the temperature inside the quartz furnace tube 40 to l,l C.
  • a positive potential of +500 volts from a battery 60 is attached to the platinum film 44 by means of a lead 62, with respect to ground.
  • the oxygen gas in the platinum-coated quartz furnace tube 40 grows a relatively mobile-positive-ion-free silicon oxide insulator layer 70 on a silicon wafer 72, which is placed on a silicon wafer holder 74 in the platinum-coated quartz furnace tube 40.
  • An exit port 80 allows the oxygen gas to exit from the quartz furnace tube 40.
  • An MOO-Angstrom silicon oxide insulator layer 70 is grown upon an N-type'silicon wafer 72, having P-type source and drain regions diffused therein, by oxidizing it for 180 minutes.
  • the silicon oxide insulator layer 70 which is produced has a IO-fold reduction in the concentration of mobile positively charged ions therein over a silicon dioxide insu lator layer that is produced in a quartz furnace tube which does not have a platinum film thereon.
  • a twofold reduction in the concentration of mobile positive ions is produced therein from a silicon dioxide insulator layer produced in a platinum coated quartz furnace tube 40 which does not have a positive potential applied to the platinum film 44.
  • FIG. 5 shows an MOS field effect transistor having a mobile-positive-ion-free silicon dioxide insulator layer 70 therein. As shown in FIG. 5, the silicon dioxide layer 70 is selectively etched so as only to extend from the edge of the P- type source region 99 to the edge of the P-type drain region 92.
  • a small area of a partially processed silicon wafer 72 can then be fabricated into a completed metal-silicon oxide-silicon (MOS) field effect transistor 100, as shown in FIG. 5.
  • a gate electrode 102 such as an aluminum gate electrode, is deposited by vacuum evaporation upon the silicon oxide layer 70 through an evaporation mask.
  • a source electrode 103 and a drain electrode 105 are attached to the P-type source region 99 and to the P-type drain region 92, also by vacuum deposition.
  • a metal-silicon oxide-silicon (MOS) field effect transistor is thereby produced.
  • mobile-positive-sodium-ion-free silicon dioxide layer 70 therefore, aids in producing an MOS field effect transistor 100, which begins to conduct a source-drain current, at a small 3 volts threshold voltage from a.,battery 110.
  • the amount of source-drain current from the battery 112 also does not appreciably drift for a given gate voltage, under the periodic operation of the MOS field effect transistor 100. That is, the processing apparatusof the present invention aids in producing a silicon dioxide insulator layer 70, upon a silicon wafer 72, in such a way as to retard the trapping of mobile positive sodium ions within the silicon dioxide insulator layer 70 of the MOS field effect transistor [00.
  • the decreased drift in the source-drain current for a given gate voltage, in the MOS field effect transistor 100, is due to the near lack of mobile positive' sodium ions in the silicon dioxide insulator layer 70. If sodium atoms couldmigrate within the silicon dioxide insulator layer 70, a greater negative threshold voltage than 3 volts would be required, the added gate voltage being necessary to make up for the charge concentration of positive sodium atoms in the silicon dioxide insulator layer 70.
  • An impervious processing furnace tube whose inner wall surface is coated with an amorphous nonoxidizing high-melting-point nonporous metal film of thickness between approximately 600 and 6,000 Angstroms, which is a nonporous barrier to the passage of mobile positive sodium ions into the interior of the processing furnace tube between a temperature of approximately 600 C. and 1,200 C., the impervious processing furnace tube having a wall thickness of approximately 0.5 centimeters.
  • An impervious quartz processing furnace tube composed of a processing furnace tube whose inner wall surface is successively coated with a high-melting-point nonporous metal filrn of a thickness between approximately 600 and 6,000 Angstroms and a silicon nitride oxygen-impervious layer to prevent oxidation of said metal film, the metal film being a nonporous barrier to the passage of mobile positive sodium ions into the interior of the processing furnace tube between a temperature of approximately 600 C. and 1,200 C., the impervious-processingfurnace tube having a wall thickness of approximately.0.5 centimeters.
  • a processing. apparatus for processing semiconductor material in a mobile-sodium-ion-free furnace tube comprising:
  • an impervious processing furnace tube having a wall thickness of approximately 0.5 centimeters and a thin nonoxidizing, high-melting-point nonporous metal film thickness between approximately 600 and 6,000 Angstroms coated upon said furnace tube to shield the interior of said tube from mobile sodium ions between a temperature of approximately 600 C. and [200 C.;
  • positive potential means connected to said metal film to place a positive potential thereon for further hindering mobile positive sodium ions from entering the interior of said furnace tube;
  • gas means connected to said tube for passing a gas through said furnace tube to flush mobile ions from the interior of said furnace tube.

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  • General Engineering & Computer Science (AREA)
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  • Electrodes Of Semiconductors (AREA)

Abstract

The present invention relates to a processing apparatus for growing and annealing a silicon dioxide insulator layer to obtain a mobile positive ion free silicon dioxide insulator layer. A mobile positive ion free silicon dioxide insulator layer is required in order to make a stable insulated gate field effect transistor. The processing apparatus comprises a nonoxidizing high-melting-point platinum metal film coated quartz furnace tube, potential means for placing a positive potential upon the platinum metal film coating of the platinum metal film coated quartz furnace tube to repel mobile ions therefrom, heater means for heating the interior of the quartz furnace tube, and gas means for passing oxygen gas through the platinum metal film coated quartz furnace tube. A silicon wafer may be oxidized in said processing apparatus to form a relatively mobile positive ion free silicon dioxide insulator layer of an insulated gate field effect transistor upon the silicon wafer. The silicon dioxide insulator layer is relatively uncontaminated by mobile positive ions which exist to the outside of the platinum metal film coated quartz furnace tube. A silicon wafer which previously has been coated by a silicon dioxide insulator layer may be processed to remove mobile ions within the silicon dioxide insulator layer. Mobile positive ions are repelled by the positive potential applied to the platinum metal film away from the outside of the quartz furnace tube, and mobile positive ions of the silicon dioxide insulator layer within the platinum metal film coated quartz tube are removed by the flowing oxygen gas due to the low-vapor pressure of the mobile positive ions.

Description

United States Patent Koepp et a1.
[54] FURNACE APPARATUS FOR BLOCKING SODIUM IONS [72] Inventors: Ronald L. Koepp, Dayton; Stanley J. Dudkowski, Kettering, both of Ohio [73] Assignee: The National Cash Register Company,
Dayton, Ohio [22] Filed: Oct. 14, 1969 1211 Appl. No.: 866,185
[52] US. Cl. ..23/252 R, 13/1, 13/20, 23/277, 117/95, 117/107, 117/227, 117/229,
[51] Int. Cl. ..B0lj l/00,C23c 11/00 [58] Field ofSearch ..23/252, 277, 288 J, 288 M; 118/48, 49, 49.1, 49.5; 117/95, 229, 107 US, 227,
Primary ExaminerJoseph Scovronek Att0rneyLouis A. Kline, John .1. Callahan and John P. Tarlano 1 Feb. 29, 1972 [57] ABSTRACT The present invention relates to a processing apparatus for growing and annealing a silicon dioxide insulator layer to obtain a mobile positive ion free silicon dioxide insulator layer, A mobile positive ion free silicon dioxide insulator layer is required in order to make a stable insulated gate field effect transistor. The processing apparatus comprises a nonoxidizing high-melting-point platinum metal film coated quartz fumuce tube, potential means for placing a positive potential upon the platinum metal film coating of the platinum metal film coated quartz furnace tube to repel mobile ions therefrom, heater means for heating the interior of the quartz furnace tube, and gas means for passing oxygen gas through the platinum metal film coated quartz furnace tube. A silicon wafer may be oxidized in said processing apparatus to form a relatively mobile positive ion free silicon dioxide insulator layer of an insulated gate field effect transistor upon the silicon wafer. The silicon dioxide insulator layer is relatively uncontaminated by mobile positive ions which exist to the outside of the platinum metal film coated quartz furnace tube. A silicon wafer which previously has been coated by a silicon dioxide insulator layer may be processed to remove mobile ions within the silicon dioxide insulator layer. Mobile positive ions are repelled by the positive potential applied to the platinum metal film away from the outside of the quartz furnace tube, and mobile positive ions of the silicon dioxide insulator layer within the platinum metal film coated quartz tube are removed by the flowing oxygen gas due to the low-vapor pressure of the mobile positive ions.
4 Claims, 5 Drawing Figures FURNACE APPARATUS FOR BLOCKING SODIUM IONS BACKGROUND OF THE INVENTION U.S. Pat. No. 3,380,852, issued Apr. 30, 1968, on the application of Adolf Goetzberger, discloses a method of forming a relatively uncontaminated silicon oxide layer upon a silicon wafer, comprising placing a silicon wafer within a quartz furnace tube, placing a wire electrode in close spatial relation above the silicon wafer, applying'a positive potential to the electrode with respect to the silicon wafer, and oxidizing the silicon wafer with the positive potential applied to the electrode. Goetzberger states that charges from the positively charged electrode neutralize negative ions within the silicon dioxide layer, so as to form a relatively uncontaminated silicon dioxide layer.
'Goetzberger does not disclose a metal film coated quartz furnace tube having a positive potential applied to the metal film to repel positive ions away from the exterior of the metal film and to allow a flowing oxidation gas to absorb positive ions from within a silicon dioxide layer. Goetzberger has only a penetrable positive potential around a silicon wafer, by setting up an electric field between a positively charged wire electrode and the negatively charged wafer.
In the processing apparatus of the present invention, a potential difference is not set up between the metal film coating of a metal film coated quartz furnace tube and a silicon wafer, but the silicon wafer exists within a positive equipotential closed metal film. The silicon wafer is not subjected to an electric field during its oxidation or during its annealing, but both during oxidation and during annealing, positive ions that may exist to the outside of the metal film coated quartz furnace tube are repelled and prevented from entering the metal film coated quartz furnace tube, as a result of a positive potential existing upon the metal film coating of the metal film coated quartz furnace tube with respect to ground. Therefore positive ions are prevented from diffusing through the metal coated quartz furnace tube and combining with a silicon dioxide insulator layer during its formation upon the silicon wafer. Positive ions are also prevented from diffusing through the metal film coated quartz furnace tube to combine with a silicon dioxide insulator layer during its annealing. During annealing of the silicon dioxide insulator layer, positive ions emitted from the silicon dioxide insulator layer are absorbed in a flowing oxidation gas which is passed through the interior of the metal film coated quartz furnace tube.
The positively charged wire electrode of Goetzberger repels some positive ions that exist on the outside of the area between the positively charged wire electrode and the negatively charged silicon wafer, but does not repel positive ions which get into said area. In fact, positive ions which get into said area are absorbed by the negatively charged silicon wafer.
The processing apparatus of the present invention hinders the combination of positive ions which may enter within the metal-film-coated quartz furnace tube with a silicon dioxide insulator layer therein, due to the flushing of the metal-filmcoated quartz furnace tube with oxygen gas.
SUMMARY OF THE INVENTION DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of the processing apparatus of the present invention used as an annealing furnace.
FIG. 2 is a cross-sectional view of an externally coate processing furnace tube.
processing apparatus of the present invention used as an oxidation furnace.
FIG. 5 is a cross-sectional view of an MOS field effect transistor having a positive sodium ion free silicon dioxide insulator layer.
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a processing apparatus for annealing a silicon dioxide insulator layer to deplete the concentration of positive ions therein. As shown in FIG. 1, a 0.5-centimeter-thick furnace tube 12 has evaporated upon its inner surface 13 a 700- Angstrom-thick nonoxidizing, high-melting-point metal film 14 to form an inner wall therein. The metal film 14 is preferably a platinum or rhodium film. However, a tantalum or titanium film, with an oxygen-impervious silicon nitride layer thereon, can be used. The metal film 14, even through being an evaporated amorphous film on the furnace tube I2, is a good barrier to the passage of mobile ions, such as mobile positive sodium ions, due to its crystal structure.
In accordance with the present invention, a metal film 14 has been found to be necessary to make a resistively heated furnace tube, such as a quartz, aluminum oxide, silicon carbide, or silicon nitride furnace tube, impervious to ions, such as positive sodium ions, at high temperature. A resistively heated furnace tube 12 will reach a temperature of approximately 1,100 C., at which temperature it is porous to positive sodium ions. That is, sodium ions are highly mobile in diffusing through the crystalline structure of the furnace tube 12.
A platinum film 14 should be as thick as 600 Angstroms to stop most of the mobile ions from getting therethrough. However, a thinner film would be fairly effective in stopping mobile ions. An evaporated platinum film 14 which is made thicker than 600 Angstroms is increasingly effective in stopping mobile ions. An evaporated platinum film 14 which is thicker than 6,000 Angstroms begins to peel from the quartz furnace tube 12. Therefore, a platinum film 14 which is between 600 and 6,000 Angstroms thick is preferred.
As shown in FIG. 2, a platinum film 8 may be evaporated on the outside of a quartz furnace tube 6. Such a platinum film 8 which is between 600 and 6,000 Angstroms thick is effective in stopping mobile ions from entering the interior of the quartz furnace tube 6. However, since mobile ions are located in the quartz furnace tube 6 itself, it is preferable that a platinum film be on the inside of the quartz furnace tube 6.
In FIG. 1, the platinum film 14, being on the inner surface of the fumace tube 12, hinders the mobile positive sodium ions within the wall of the furnace tube itself from diffusing into the interior of the furnace tube 12 at high temperature. The platinum film 14 does not melt at 1,100 C. and does not oxidize at 1,100 C. in an oxidizing atmosphere. Gold, which also is a metal, melts near 1,063 C. Therefore, gold cannot be used to coat a quartz furnace tube 12 which is heated to 1,100 C. Silver also melts below 1,100 C. A copper film melts below 1,l00 C. Therefore a copper film may not be used to form a nonporous barrier to the passage of mobile ions into the interior of the quartz processing furnace tube 12 when it is used in a high-temperature oxidation processing apparatus.
As shown in FIG. 3, a tantalum film 10 may be evaporated upon the inside surface of a quartz furnace tube 9. The tantalum film l0 oxidizes in an oxidizing atmosphere, at 1,l00 C. However, a layer 11 impervious to oxygen at high temperature, such as a silicon nitride layer, is placed upon the exposed surface of the 700-Angstrom-thick tantalum film 10. The silicon nitride layer 11 prevents oxygen in the interior of the tantalum-coated quartz furnace tube 9 from oxidizing the tantalum film 10. The tantalum film 10 on the inner surface of the quartz furnace tube 9 prevents mobile ions from entering the interior of the quartz furnace tube 9.
A metal film is preferred for use in the processing apparatus of the present invention which has no mobile ions, has a highmelting point, and does not oxidize at a high temperature. A platinum film is a very good metal film which has these properties.,Its atomic crystalline structure is fine enough to stop mobile ions from passing through it at high temperature.
As shown in FIG. 1, the platinum film 14, having been evaporated, is an amorphous platinum film. The evaporation causes the platinum film, which is evaporated on the inside of a quartz tube, to be amorphous. However, the evaporated film 14, being semicrystalline, is impervious to mobile ions.
It is to be observed that a solid metal furnace tube, such as a platinum furnace tube, can be used in place of a metal-filmcoated furnace tube. A solid platinum furnace tube is impervious to mobile ions, such as mobile positive sodium ions, at a temperature of 1,100" C. The inner wall of a solid platinum furnace tube is, of course, composed of a metal.
As shown in FIG. 1, a battery 18 is attached to the end of the platinum film 14 by means of a lead 16. The edge of the platinum film 14 will reach a temperature of only about 100 C., since it is notdirectly under the radiant heating coil 30. The battery 18 applied a positive 500 volts potential, with respect to ground, to the 700-Angstrom-thick platinum film 14. By applying a positive potential to the platinum film 14 on the furnace tube 12, one can further hinder the passage of mobile positive sodium ions from the outside of the tube 12 into the interior of the furnace tube 12.
A silicon wafer holder 22 is laid within the platinum coated quartz furnace tube 12. A silicon wafer 24, havinga 1,200- Angstrom-thick silicon oxide insulator layer 26, is held by the silicon wafer holder 22 within the platinum coated quartz furnace tube 12. The resistance heating coil 30 is placed around the outside of the platinum-coated quartz furnace tube 12.
The platinum film 14 is held at a positive 500 volts with respect to ground. Heat from the' radiant heating coil 30, which is driven by an AC power source 34, raises the temperature of the silicon wafer 24 within the center of the platinumcoated quartz furnace tube to 600 C. A 100 cc./minute flowing oxygen gas from an oxygen container is passed through 95 C. water 32 within a container 33, and then through the platinum-coated quartz furnace tube 12 while it is being heated, for 60 minutes. In accordance with the present invention, a 14-fold reduction in the number of mobile positive ions, including mobile positive sodium ions, within the silicon oxide insulator layer 26 is achieved, using a positively charged platinum-coated quartz furnace tube 12, over what can be obtained using an uncoated quartz furnace tube. A threefold reduction in the number of mobile positive ions, including mobile positive sodium ions, is achieved with the use of a positively charged platinum-coated quartz furnace tube 12, over what can be obtained with the use of an uncharged platinumcoated quartz furnace tube 12..
FIG. 4 shows a processing apparatus for oxidizing semiconductor material in a mobile-positive-ion-free furnace tube 40. As shown in FIG. 4, a platinum-coated quartz furnace tube 40 is positioned by a suitable means within a resistance heating coil 42. A 700-Angstrom-thick platinum film 44 is evaporated upon the inside surface 45 of the quartz furnace tube 40. Oxygen gas is pased through the quartz furnace tube 40 from an oxygen container 48 at the rate of 300 cc./minute. Radiant heat, from the resistance heating coil 42, which is driven by an AC power source 50, raises the temperature inside the quartz furnace tube 40 to l,l C. A positive potential of +500 volts from a battery 60 is attached to the platinum film 44 by means of a lead 62, with respect to ground. The oxygen gas in the platinum-coated quartz furnace tube 40 grows a relatively mobile-positive-ion-free silicon oxide insulator layer 70 on a silicon wafer 72, which is placed on a silicon wafer holder 74 in the platinum-coated quartz furnace tube 40. An exit port 80 allows the oxygen gas to exit from the quartz furnace tube 40. An MOO-Angstrom silicon oxide insulator layer 70 is grown upon an N-type'silicon wafer 72, having P-type source and drain regions diffused therein, by oxidizing it for 180 minutes.
It is found that the silicon oxide insulator layer 70 which is produced has a IO-fold reduction in the concentration of mobile positively charged ions therein over a silicon dioxide insu lator layer that is produced in a quartz furnace tube which does not have a platinum film thereon. A twofold reduction in the concentration of mobile positive ions is produced therein from a silicon dioxide insulator layer produced in a platinum coated quartz furnace tube 40 which does not have a positive potential applied to the platinum film 44.
FIG. 5 shows an MOS field effect transistor having a mobile-positive-ion-free silicon dioxide insulator layer 70 therein. As shown in FIG. 5, the silicon dioxide layer 70 is selectively etched so as only to extend from the edge of the P- type source region 99 to the edge of the P-type drain region 92.
A small area of a partially processed silicon wafer 72 can then be fabricated into a completed metal-silicon oxide-silicon (MOS) field effect transistor 100, as shown in FIG. 5. A gate electrode 102, such as an aluminum gate electrode, is deposited by vacuum evaporation upon the silicon oxide layer 70 through an evaporation mask. A source electrode 103 and a drain electrode 105 are attached to the P-type source region 99 and to the P-type drain region 92, also by vacuum deposition. A metal-silicon oxide-silicon (MOS) field effect transistor is thereby produced.
Due to the formation of the silicon oxide insulator layer 70 within a mobile-positive-sodium-ion free environment, mobile positive sodium ions are not trapped within the silicon dioxide insulator layer 70 of the MOS field effect transistor 100. The
mobile-positive-sodium-ion-free silicon dioxide layer 70, therefore, aids in producing an MOS field effect transistor 100, which begins to conduct a source-drain current, at a small 3 volts threshold voltage from a.,battery 110. The amount of source-drain current from the battery 112 also does not appreciably drift for a given gate voltage, under the periodic operation of the MOS field effect transistor 100. That is, the processing apparatusof the present invention aids in producing a silicon dioxide insulator layer 70, upon a silicon wafer 72, in such a way as to retard the trapping of mobile positive sodium ions within the silicon dioxide insulator layer 70 of the MOS field effect transistor [00. The decreased drift in the source-drain current for a given gate voltage, in the MOS field effect transistor 100, is due to the near lack of mobile positive' sodium ions in the silicon dioxide insulator layer 70. If sodium atoms couldmigrate within the silicon dioxide insulator layer 70, a greater negative threshold voltage than 3 volts would be required, the added gate voltage being necessary to make up for the charge concentration of positive sodium atoms in the silicon dioxide insulator layer 70.
What is claimed is: A t
1. An impervious processing furnace tube whose inner wall surface is coated with an amorphous nonoxidizing high-melting-point nonporous metal film of thickness between approximately 600 and 6,000 Angstroms, which is a nonporous barrier to the passage of mobile positive sodium ions into the interior of the processing furnace tube between a temperature of approximately 600 C. and 1,200 C., the impervious processing furnace tube having a wall thickness of approximately 0.5 centimeters. i I
2. An impervious quartz processing furnace tube composed of a processing furnace tube whose inner wall surface is successively coated with a high-melting-point nonporous metal filrn of a thickness between approximately 600 and 6,000 Angstroms and a silicon nitride oxygen-impervious layer to prevent oxidation of said metal film, the metal film being a nonporous barrier to the passage of mobile positive sodium ions into the interior of the processing furnace tube between a temperature of approximately 600 C. and 1,200 C., the impervious-processingfurnace tube having a wall thickness of approximately.0.5 centimeters.
3. A processing. apparatus for processing semiconductor material in a mobile-sodium-ion-free furnace tube comprising:
material in a mobile-sodium-ion-free furnace tube, comprising:
an impervious processing furnace tube having a wall thickness of approximately 0.5 centimeters and a thin nonoxidizing, high-melting-point nonporous metal film thickness between approximately 600 and 6,000 Angstroms coated upon said furnace tube to shield the interior of said tube from mobile sodium ions between a temperature of approximately 600 C. and [200 C.;
positive potential means connected to said metal film to place a positive potential thereon for further hindering mobile positive sodium ions from entering the interior of said furnace tube; and
gas means connected to said tube for passing a gas through said furnace tube to flush mobile ions from the interior of said furnace tube.

Claims (3)

  1. 2. An impervious quartz processing furnace tube composed of a processing furnace tube whose inner wall surface is successively coated with a high-melting-point nonporous metal film of a thickness between approximately 600 and 6,000 Angstroms and a silicon nitride oxygen-impervious layer to prevent oxidation of said metal film, the metal film being a nonporous barrier to the passage of mobile positive sodium ions into the interior of the processing furnace tube between a temperature of approximately 600* C. and 1,200* C., the impervious processing furnace tube having a wall thickness of approximately 0.5 centimeters.
  2. 3. A processing apparatus for processing semiconductor material in a mobile-sodium-ion-free furnace tube comprising: an impervious processing furnace tube having a wall thickness of approximately 0.5 centimeters and a thin nonoxidizing, high-melting-point nonporous metal film of a thickness between approximately 600 and 6,000 Angstroms coated upon said furnace tube, to shield the interior of said furnace tube from mobile sodium ions between a temperaturE of approximately 600* C. and 1,200* C., and a positive potential means connected to said metal film to place a positive potential thereon for further hindering mobile positive sodium ions from entering the interior of said furnace tube.
  3. 4. A processing apparatus for processing semiconductor material in a mobile-sodium-ion-free furnace tube, comprising: an impervious processing furnace tube having a wall thickness of approximately 0.5 centimeters and a thin nonoxidizing, high-melting-point nonporous metal film thickness between approximately 600 and 6,000 Angstroms coated upon said furnace tube to shield the interior of said tube from mobile sodium ions between a temperature of approximately 600* C. and 1,200* C.; positive potential means connected to said metal film to place a positive potential thereon for further hindering mobile positive sodium ions from entering the interior of said furnace tube; and gas means connected to said tube for passing a gas through said furnace tube to flush mobile ions from the interior of said furnace tube.
US866185A 1969-10-14 1969-10-14 Furnace apparatus for blocking sodium ions Expired - Lifetime US3645695A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3742904A (en) * 1971-06-03 1973-07-03 Motorola Inc Steam generator and gas insertion device
US3925583A (en) * 1972-02-11 1975-12-09 Heraeus Schott Quarzschmelze Composite quartz glass body
US4154192A (en) * 1976-12-10 1979-05-15 Mitsubishi Denki Kabushiki Kaisha Manufacturing apparatus for semiconductor devices
US4587928A (en) * 1975-12-24 1986-05-13 Tokyo Shibaura Electric Co., Ltd. Apparatus for producing a semiconductor device
US4592307A (en) * 1985-02-28 1986-06-03 Rca Corporation Vapor phase deposition apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63105255U (en) * 1986-12-26 1988-07-07

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2746888A (en) * 1952-07-05 1956-05-22 Du Pont Method of forming titanium coating on refractory body
US3010092A (en) * 1958-08-05 1961-11-21 Bourns Inc Variable resistor
US3112215A (en) * 1959-10-09 1963-11-26 Lonza Ag Preparation of catalytically active coatings
US3446659A (en) * 1966-09-16 1969-05-27 Texas Instruments Inc Apparatus and process for growing noncontaminated thermal oxide on silicon
US3507627A (en) * 1964-05-22 1970-04-21 Prototech Inc Heating and catalytic chemical reaction apparatus
US3516850A (en) * 1966-09-16 1970-06-23 Texas Instruments Inc Process for metal coating a hydrogen permeable material

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2746888A (en) * 1952-07-05 1956-05-22 Du Pont Method of forming titanium coating on refractory body
US3010092A (en) * 1958-08-05 1961-11-21 Bourns Inc Variable resistor
US3112215A (en) * 1959-10-09 1963-11-26 Lonza Ag Preparation of catalytically active coatings
US3507627A (en) * 1964-05-22 1970-04-21 Prototech Inc Heating and catalytic chemical reaction apparatus
US3446659A (en) * 1966-09-16 1969-05-27 Texas Instruments Inc Apparatus and process for growing noncontaminated thermal oxide on silicon
US3516850A (en) * 1966-09-16 1970-06-23 Texas Instruments Inc Process for metal coating a hydrogen permeable material

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3742904A (en) * 1971-06-03 1973-07-03 Motorola Inc Steam generator and gas insertion device
US3925583A (en) * 1972-02-11 1975-12-09 Heraeus Schott Quarzschmelze Composite quartz glass body
US4587928A (en) * 1975-12-24 1986-05-13 Tokyo Shibaura Electric Co., Ltd. Apparatus for producing a semiconductor device
US4154192A (en) * 1976-12-10 1979-05-15 Mitsubishi Denki Kabushiki Kaisha Manufacturing apparatus for semiconductor devices
US4592307A (en) * 1985-02-28 1986-06-03 Rca Corporation Vapor phase deposition apparatus

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ES384378A1 (en) 1973-02-16
CA961385A (en) 1975-01-21
CH515613A (en) 1971-11-15
GB1260070A (en) 1972-01-12
FR2064318A1 (en) 1971-07-23
JPS4922781B1 (en) 1974-06-11
DE2049904A1 (en) 1971-05-13
FR2064318B1 (en) 1976-09-03
BE757500A (en) 1971-03-16

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