WO1995000676A1 - Ultrasonic enhancement of aluminum step coverage and apparatus - Google Patents

Ultrasonic enhancement of aluminum step coverage and apparatus Download PDF

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Publication number
WO1995000676A1
WO1995000676A1 PCT/US1994/006792 US9406792W WO9500676A1 WO 1995000676 A1 WO1995000676 A1 WO 1995000676A1 US 9406792 W US9406792 W US 9406792W WO 9500676 A1 WO9500676 A1 WO 9500676A1
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Prior art keywords
aluminum
ultrasonic energy
semiconductor
substrate
vias
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PCT/US1994/006792
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French (fr)
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Michael G. Ward
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Materials Research Corp
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Materials Research Corp
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Priority to EP94920227A priority Critical patent/EP0707662A4/en
Priority to AU71096/94A priority patent/AU7109694A/en
Priority to JP7502942A priority patent/JPH08511656A/en
Priority to KR1019950705653A priority patent/KR960703179A/en
Publication of WO1995000676A1 publication Critical patent/WO1995000676A1/en
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3471—Introduction of auxiliary energy into the plasma
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3435—Applying energy to the substrate during sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/04—Coating on selected surface areas, e.g. using masks
    • C23C14/046—Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/50—Substrate holders
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D64/00—Electrodes of devices having potential barriers
    • H10D64/01—Manufacture or treatment
    • H10D64/013—Manufacture or treatment of electrodes having a conductor capacitively coupled to a semiconductor by an insulator
    • H10D64/01302—Manufacture or treatment of electrodes having a conductor capacitively coupled to a semiconductor by an insulator the insulator being formed after the semiconductor body, the semiconductor being silicon
    • H10D64/01304—Manufacture or treatment of electrodes having a conductor capacitively coupled to a semiconductor by an insulator the insulator being formed after the semiconductor body, the semiconductor being silicon characterised by the conductor
    • H10D64/01306—Manufacture or treatment of electrodes having a conductor capacitively coupled to a semiconductor by an insulator the insulator being formed after the semiconductor body, the semiconductor being silicon characterised by the conductor the conductor comprising a layer of silicon contacting the insulator, e.g. polysilicon
    • H10D64/01308—Manufacture or treatment of electrodes having a conductor capacitively coupled to a semiconductor by an insulator the insulator being formed after the semiconductor body, the semiconductor being silicon characterised by the conductor the conductor comprising a layer of silicon contacting the insulator, e.g. polysilicon the conductor further comprising a non-elemental silicon additional conductive layer, e.g. a metal silicide layer formed by the reaction of silicon with an implanted metal
    • H10D64/01312—Manufacture or treatment of electrodes having a conductor capacitively coupled to a semiconductor by an insulator the insulator being formed after the semiconductor body, the semiconductor being silicon characterised by the conductor the conductor comprising a layer of silicon contacting the insulator, e.g. polysilicon the conductor further comprising a non-elemental silicon additional conductive layer, e.g. a metal silicide layer formed by the reaction of silicon with an implanted metal the additional layer comprising a metal or metal silicide formed by deposition, i.e. without a silicidation reaction, e.g. sputter deposition
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/32—Processing objects by plasma generation
    • H01J2237/33—Processing objects by plasma generation characterised by the type of processing
    • H01J2237/332—Coating
    • H01J2237/3322—Problems associated with coating
    • H01J2237/3327—Coating high aspect ratio workpieces

Definitions

  • the active switching elements of integrated circuits are interconnected by metal lines deposited by various methods such as physical vapor deposition, chemical vapor deposition, and evaporation. Typically, several levels of metal lines are used in an integrated circuit to allow crossovers. At certain locations, electrical contact is made between lines at different levels. Such contacts are called vias.
  • the drive of integrated circuits to submicron geometry has resulted in vias and contacts of extreme aspect ratio and size. Filling submicron vias and contacts with a conducting metal is extremely difficult. If extreme care is not taken, voids will remain and the wafer must be discarded.
  • Aluminum thin film metallization is the primary material for conductor of metallization on large scale integrated (LSI) and very large scale integrated (VLSI) circuits. Manufacturers of these devices require the interlevel contact of a metal layer and the silicon layer beneath a dielectric. In addition, interconnects between metal layers separated by a dielectric ' may be necessary. To reach this end, the conductor metallization must cover vertical or near vertical surfaces in addition to the circuit areas of the substrate. Providing adequate material within the interconnect measured as step coverage, can become difficult depending on the aspect ratio, vertical wall angle, and thin film deposition technique. Physical vapor deposition primarily as evaporation or sputtering, is a method must commonly employed for aluminum deposition. The drawback of these line of site deposition techniques is the self-shadowing effect when any appreciable amount of material has been deposited. The self-shadowing limits step coverage and introduces defects into the interconnect metallization.
  • U.S. Patent 4,994,162 This uses a low temperature seed layer providing a continuous high quality diffusion path for subsequently deposited material to diffuse along.
  • a high temperature, low deposition rate step to allow efficient surface diffusion into the feature is employed followed by a high temperature, high deposition rate step to complete the deposition.
  • Bulk diffusion as a mechanism for via filling has also been proposed by Sugano et al in 1992 VMIC Conference Proceedings "Quarter micron whole filling with SiN sidewalls by aluminum high temperature sputtering.” With the
  • the driving force for via filling is the interface between a titanium surface layer and the deposited aluminum.
  • the process requires the presence of a continuous and high quality titanium surface on the sidewall of a via.
  • Tracy U.S. Patent 4,970,176 discloses a deposition of a relatively thick layer of aluminum at a first temperature and a subsequent deposition of a thin layer of aluminum at a high temperature. The specification indicates that the temperature increase acts to reflow the aluminum through grain growth and recrystallization.
  • bias deposition In addition to elevated substrate temperature, other techniques available to improve aluminum step coverage include bias deposition, collimation, and chemical vapor deposition. Each technique necessitates a compromise in processing and final film properties. Higher substrate temperatures and bias provide the driving force for aluminum mobility through thermal activation and physical resputtering respectively. However, film properties such as grain size, reflectivity, alloy precipitation and resistivity are significantly altered.
  • barrier layers between the aluminum and silicon may also be necessary to limit the aluminum silicon reaction at temperatures above 450 * C.
  • the use of titanium or titanium nitride layers underneath the aluminum will enhance surface mobility of the aluminum and elevated substrate temperatures. Any significant reaction between the aluminum and titanium, however, will significantly raise the film resistivity.
  • the present invention is premised on the realization that aluminum metal can be deposited onto substrates and the mobility enhanced through the application of ultrasonic energy.
  • the present invention is further premised on the realization that such ultrasonic energy enhanced mobility can be accomplished at temperatures significantly lower than those usually necessary for thermal energy mobility enhancement alone.
  • a semiconductor substrate is clamped to a block containing an ultrasonic wave generator capable of scanning a frequency range from 38kHz to about 42kHz.
  • Aluminum is sputter deposited as moderate heat is applied either through radiation lamps or through the block.
  • the present invention is a multi-step process which includes an initial aluminum deposition typically around 2000 angstroms at a substrate temperature of 100 to 300 * C.
  • ultrasonic energy is applied to the substrate along with a concurrent application of substrate heating typically from 350 to 500 "C.
  • the sputter deposition of material continues during the application of ultrasonic energy, but may be at a lower rate to allow time for the material to move into features of the wafer. This continues until the desired aluminum film thickness is achieved.
  • Fig. 1 is a cross-sectional diagrammatic depiction of the apparatus used in the present invention
  • Fig. 2 is an overhead view of the wafer holding mechanism used in the apparatus shown in Fig. 1;
  • Fig. 3 is a bottom view of the wafer holding mechanism used in the apparatus shown in Fig. 1. Detailed Description
  • the present invention is a method of filling vias and contacts in a semi-conductor wafer or substrate. It is particularly beneficial for filling vias and contacts having submicron diameters where the aspect ratio, that is the height to diameter ratio, is from 1 to about 4. In practicing the present invention, vias and contacts having diameters of 1 to about .1 microns and generally 1 to about .3 microns can be filled. For purposes of the present invention, vias and contacts will be collectively referred to simply as vias.
  • the present invention is basically a three step process.
  • aluminum or an aluminum alloy will be deposited at a relatively low temperature.
  • the wafer will be clamped to a block which includes an apparatus to generate ultrasonic energy transmitted through the clamped wafer.
  • the ultrasonic energy will be applied at the same time the wafer or substrate is heated and aluminum is deposited.
  • the via containing substrates which can be coated in the present invention include silicon substrates, boron trifluoride doped silica substrates, quartz substrates, and gallium arsenide substrates.
  • the aluminum layer can be 100% aluminum or more preferably an aluminum alloy such as aluminum silicon (1%), copper (.5%), aluminum-copper (1%), and aluminum-titanium (.15%).
  • the present invention is a modified sputtering system 11 which includes a chamber 12 which is a grounded vacuum tight enclosure.
  • the chamber is connected to a vacuum system (not shown) which can reduce the pressure to the desired levels typically down to 1 X 10 "8 torr or lower prior to sputtering.
  • the aluminum sputtering target 13 which is attached to the cathode 14 which in turn is attached to the negative terminal 15 of a DC power supply.
  • the positive terminal of the power supply is grounded.
  • Argon is introduced into the chamber and power is applied to the target to carry out the sputter deposition.
  • the anode substrate holder 16 As shown more particularly in Fig. 2 and Fig. 3, this includes a block 17 which supports a series of clamps 18 to hold the substrate 19. Beneath the block 17 is an apparatus adapted to provide ultrasonic energy through the block and ultimately apply it to the substrate. As shown in this Fig. 3, the mechanism is a series ultrasonic transducers 21 (nine shown) physically attached to the bottom side of the block 17.
  • the source of ultrasonic energy must provide from 38kHz up to about 42kHz frequency against the backside of the wafer.
  • the source of ultrasonic energy must be modulated across the wafer during deposition to avoid node formation.
  • Suitable transducers for example, can be purchased from Ultrasonic Corporation.
  • the mounting mechanism for the wafer can be modified to employ other clamping mechanisms such as an electrostatic clamping mechanism.
  • the multi-stepped deposition of the present invention is conducted in a multi-chambered sputtering unit which would include an etching chamber and at least three sputtering chambers.
  • a multi-chambered sputtering unit which would include an etching chamber and at least three sputtering chambers.
  • One of the sputtering chambers would incorporate the features shown in Fig. 1.
  • Multiple chamber sputtering apparatuses are known.
  • One for example is the Eclipse brand sputtering system sold by Materials Research Corporation, also referred to in U.S. Patent 4,994,162.
  • Other commercially available systems are equally suited.
  • the substrate or wafer is initially etched with argon gas to remove surface impurities. Heating the substrate also assists in removal of outgases. This is optional, but is preferred.
  • a barrier layer can be applied if desired.
  • a preferred barrier layer is titanium nitride, although zirconium nitrite, ruthenium oxide barrier layers as well as titanium tungsten layers can be utilized. Generally the thickness of the barrier layer will be about 1000 angstroms.
  • the initial aluminum alloy is applied in the third chamber. As indicated, this should be conducted at 100 to 300°C. with about lOO'C. preferred. Generally about
  • the ultrasonic energy will be applied starting at 38kHz and varying this up to about 42 kHz 100-300 times per second.
  • the substrate is heated to 300 to 450" C. while at the same time aluminum is deposited at a rate of 50 to 200 angstroms per second until 3000 to 8000 angstroms of aluminum film is deposited.

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Abstract

A method and apparatus for sputter depositing aluminum onto a semiconductor substrate (19) to fill micron and submicron vias utilizes ultrasonic energy to ensure adequate filling of the vias. The semiconductor is supported on a block (16) and heated and subjected to ultrasonic energy greater than 25kHz as aluminum is sputter deposited onto the substrate surface (19). The frequency of the ultrasonic energy is varied from 35 to 42kHz as the aluminum is deposited in order to avoid standing wave or node formation along the substrate surface. This permits an efficient high quality application of aluminum and filling of vias on a semiconductor substrate.

Description

Ultrasonic Enhancement Of Aluminum Step Coverage And Apparatus Background Of The Invention
The active switching elements of integrated circuits are interconnected by metal lines deposited by various methods such as physical vapor deposition, chemical vapor deposition, and evaporation. Typically, several levels of metal lines are used in an integrated circuit to allow crossovers. At certain locations, electrical contact is made between lines at different levels. Such contacts are called vias. The drive of integrated circuits to submicron geometry has resulted in vias and contacts of extreme aspect ratio and size. Filling submicron vias and contacts with a conducting metal is extremely difficult. If extreme care is not taken, voids will remain and the wafer must be discarded.
Aluminum thin film metallization is the primary material for conductor of metallization on large scale integrated (LSI) and very large scale integrated (VLSI) circuits. Manufacturers of these devices require the interlevel contact of a metal layer and the silicon layer beneath a dielectric. In addition, interconnects between metal layers separated by a dielectric ' may be necessary. To reach this end, the conductor metallization must cover vertical or near vertical surfaces in addition to the circuit areas of the substrate. Providing adequate material within the interconnect measured as step coverage, can become difficult depending on the aspect ratio, vertical wall angle, and thin film deposition technique. Physical vapor deposition primarily as evaporation or sputtering, is a method must commonly employed for aluminum deposition. The drawback of these line of site deposition techniques is the self-shadowing effect when any appreciable amount of material has been deposited. The self-shadowing limits step coverage and introduces defects into the interconnect metallization.
Various methods have been proposed for filling interconnecting vias and contacts with aluminum. Surface diffusion is used to move sputter deposited aluminum into vias at temperatures of approximately 450 "C. This is disclosed for example in Armstrong et al
U.S. Patent 4,994,162. This uses a low temperature seed layer providing a continuous high quality diffusion path for subsequently deposited material to diffuse along. A high temperature, low deposition rate step to allow efficient surface diffusion into the feature is employed followed by a high temperature, high deposition rate step to complete the deposition. Bulk diffusion as a mechanism for via filling has also been proposed by Sugano et al in 1992 VMIC Conference Proceedings "Quarter micron whole filling with SiN sidewalls by aluminum high temperature sputtering." With the
Sugano process, the driving force for via filling is the interface between a titanium surface layer and the deposited aluminum. The process requires the presence of a continuous and high quality titanium surface on the sidewall of a via.
Further, Tracy U.S. Patent 4,970,176 discloses a deposition of a relatively thick layer of aluminum at a first temperature and a subsequent deposition of a thin layer of aluminum at a high temperature. The specification indicates that the temperature increase acts to reflow the aluminum through grain growth and recrystallization.
In addition to elevated substrate temperature, other techniques available to improve aluminum step coverage include bias deposition, collimation, and chemical vapor deposition. Each technique necessitates a compromise in processing and final film properties. Higher substrate temperatures and bias provide the driving force for aluminum mobility through thermal activation and physical resputtering respectively. However, film properties such as grain size, reflectivity, alloy precipitation and resistivity are significantly altered.
The use of barrier layers between the aluminum and silicon may also be necessary to limit the aluminum silicon reaction at temperatures above 450* C. The use of titanium or titanium nitride layers underneath the aluminum will enhance surface mobility of the aluminum and elevated substrate temperatures. Any significant reaction between the aluminum and titanium, however, will significantly raise the film resistivity.
Collimation of the sputtered aluminum will reduce the deposition rate to 10-20% of the noncoUimated and provide significant step coverage improvements at the bottom of the interconnect only. Finally, chemical vapor deposition of aluminum films free of contamination with the necessary silicon and copper dopants is very difficult.
Summary of the Invention
The present invention is premised on the realization that aluminum metal can be deposited onto substrates and the mobility enhanced through the application of ultrasonic energy. The present invention is further premised on the realization that such ultrasonic energy enhanced mobility can be accomplished at temperatures significantly lower than those usually necessary for thermal energy mobility enhancement alone.
According to the present invention, a semiconductor substrate is clamped to a block containing an ultrasonic wave generator capable of scanning a frequency range from 38kHz to about 42kHz. Aluminum is sputter deposited as moderate heat is applied either through radiation lamps or through the block.
In a preferred embodiment, the present invention is a multi- step process which includes an initial aluminum deposition typically around 2000 angstroms at a substrate temperature of 100 to 300 *C. During a second aluminum deposit, ultrasonic energy is applied to the substrate along with a concurrent application of substrate heating typically from 350 to 500 "C. The sputter deposition of material continues during the application of ultrasonic energy, but may be at a lower rate to allow time for the material to move into features of the wafer. This continues until the desired aluminum film thickness is achieved. The objects and advantages of the present invention will be further appreciated in light of the following detailed description and drawings in which:
Brief Description of the Drawings
Fig. 1 is a cross-sectional diagrammatic depiction of the apparatus used in the present invention;
Fig. 2 is an overhead view of the wafer holding mechanism used in the apparatus shown in Fig. 1; and
Fig. 3 is a bottom view of the wafer holding mechanism used in the apparatus shown in Fig. 1. Detailed Description
The present invention is a method of filling vias and contacts in a semi-conductor wafer or substrate. It is particularly beneficial for filling vias and contacts having submicron diameters where the aspect ratio, that is the height to diameter ratio, is from 1 to about 4. In practicing the present invention, vias and contacts having diameters of 1 to about .1 microns and generally 1 to about .3 microns can be filled. For purposes of the present invention, vias and contacts will be collectively referred to simply as vias.
The present invention is basically a three step process. In the initial step, aluminum or an aluminum alloy will be deposited at a relatively low temperature. In the second step, the wafer will be clamped to a block which includes an apparatus to generate ultrasonic energy transmitted through the clamped wafer. Then, in a concurrent step, the ultrasonic energy will be applied at the same time the wafer or substrate is heated and aluminum is deposited.
The via containing substrates which can be coated in the present invention include silicon substrates, boron trifluoride doped silica substrates, quartz substrates, and gallium arsenide substrates. The aluminum layer can be 100% aluminum or more preferably an aluminum alloy such as aluminum silicon (1%), copper (.5%), aluminum-copper (1%), and aluminum-titanium (.15%).
As shown diagrammatically in Fig. 1, the present invention is a modified sputtering system 11 which includes a chamber 12 which is a grounded vacuum tight enclosure. The chamber is connected to a vacuum system (not shown) which can reduce the pressure to the desired levels typically down to 1 X 10"8 torr or lower prior to sputtering.
Within the chamber is the aluminum sputtering target 13 which is attached to the cathode 14 which in turn is attached to the negative terminal 15 of a DC power supply. The positive terminal of the power supply is grounded. Argon is introduced into the chamber and power is applied to the target to carry out the sputter deposition.
Below the target is the anode substrate holder 16. As shown more particularly in Fig. 2 and Fig. 3, this includes a block 17 which supports a series of clamps 18 to hold the substrate 19. Beneath the block 17 is an apparatus adapted to provide ultrasonic energy through the block and ultimately apply it to the substrate. As shown in this Fig. 3, the mechanism is a series ultrasonic transducers 21 (nine shown) physically attached to the bottom side of the block 17.
More particularly, the source of ultrasonic energy must provide from 38kHz up to about 42kHz frequency against the backside of the wafer. The source of ultrasonic energy must be modulated across the wafer during deposition to avoid node formation. Suitable transducers, for example, can be purchased from Ultrasonic Corporation.
Alternately, the mounting mechanism for the wafer can be modified to employ other clamping mechanisms such as an electrostatic clamping mechanism.
Preferably, the multi-stepped deposition of the present invention is conducted in a multi-chambered sputtering unit which would include an etching chamber and at least three sputtering chambers. One of the sputtering chambers would incorporate the features shown in Fig. 1. Multiple chamber sputtering apparatuses are known. One for example is the Eclipse brand sputtering system sold by Materials Research Corporation, also referred to in U.S. Patent 4,994,162. Other commercially available systems are equally suited.
In the first chamber, the substrate or wafer is initially etched with argon gas to remove surface impurities. Heating the substrate also assists in removal of outgases. This is optional, but is preferred.
The substrate is then transferred to a second chamber where a barrier layer can be applied if desired. A preferred barrier layer is titanium nitride, although zirconium nitrite, ruthenium oxide barrier layers as well as titanium tungsten layers can be utilized. Generally the thickness of the barrier layer will be about 1000 angstroms. The initial aluminum alloy is applied in the third chamber. As indicated, this should be conducted at 100 to 300°C. with about lOO'C. preferred. Generally about
1500 angstroms of the initial aluminum layer will be deposited. This is conducted without the application of ultrasonic energy.
In the final wafer or substrate onto the block and clamping it in position. In an initial deposition, 1000 to 3000 angstroms of aluminum or aluminum alloy will be deposited at 100 to 300 °C. at a deposition rate of 150 to 250 angstroms per second. In a second step, the ultrasonic energy will be applied starting at 38kHz and varying this up to about 42 kHz 100-300 times per second. At this time, either by heating the block or by utilizing a heating lamp, the substrate is heated to 300 to 450" C. while at the same time aluminum is deposited at a rate of 50 to 200 angstroms per second until 3000 to 8000 angstroms of aluminum film is deposited.
Using this method, the vias are effectively filled without permitting gaps or other incontinuities in the vias and surface substrate which could cause a malfunction of the wafer. Further, because the temperature of this system operates preferably at less than 450° C, the negative film effects caused by the higher temperatures are avoided. This provides a reliable and efficient method of filling vias with aluminum. Due to the application of the ultrasonic energy, excessive time and temperature are not required. Thus, quality is not sacrificed in order to provide adequate via coverage. The preceding has been a description of the present invention along with the preferred method currently known of practicing the present invention. However, the invention should only be defined by the appended claims wherein I claim:

Claims

1. A method of filling vias in a semiconductor substrate comprising: sputter depositing a film of aluminum over a first surface of said semiconductor and covering said vias; concurrently applying ultrasonic energy to a second surface of said substrate aluminum is deposited.
2. The method claimed in claim 1 wherein said ultrasonic energy is applied at a frequency greater than 25kHz.
3. The method claimed in claim 2 wherein said ultrasonic energy is applied at a frequency of from greater than 38kHz up to 42kHz.
4. The method claimed in claim 1 wherein said ultrasonic energy is modulated as said aluminum is deposited.
5. The method claimed in claim 1 comprising initially depositing 1000 to 3000 angstroms of aluminum over said surface without the application of ultrasonic energy and subsequently applying 3000 to 8000 angstroms of aluminum with the application of ultrasonic energy.
6. The method claimed in claim 4 wherein said first layer is applied at a temperature of 100 to 300 *C. and said second layer is applied at a temperature of 350 to 500' C.
7. The method of filling vias in a semiconductor substrate comprising: sputter depositing 1000 to 3000 angstroms of aluminum over the surface of said substrate covering said via without the application of ultrasonic energy at a temperature of 100 to 300" C; applying 3000 to 8000 angstroms of aluminum over the surface of said substrate and over said vias at a temperature of 350 to 500 'C. while applying ultrasonic energy to said substrate at a frequency of 38 to 42kHz while modulating said frequency.
8. An apparatus for sputter depositing aluminum onto a semiconductor comprising a semiconductor support; means to sputter deposit aluminum onto a semiconductor supported on said support; means to clamp said semiconductor to said support; means to apply ultrasonic energy to a semiconductor supported and clamped on said support as aluminum is deposited from said means to sputter aluminum onto said semiconductor.
9. The apparatus claimed in claim 8 wherein said support comprises: a block and wherein a plurality of ultrasonic transducers are affixed to a bottom surface of said block.
10. The apparatus claimed in claim 9 wherein said means to clamp said wafer to said support comprises a bracket adapted to fix said semiconductor to said block.
11. The apparatus claimed in claim 9 wherein said means to clamp said wafer to said support comprises an electrostatic holder.
PCT/US1994/006792 1993-06-17 1994-06-15 Ultrasonic enhancement of aluminum step coverage and apparatus Ceased WO1995000676A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP94920227A EP0707662A4 (en) 1993-06-17 1994-06-15 Ultrasonic enhancement of aluminum step coverage and apparatus
AU71096/94A AU7109694A (en) 1993-06-17 1994-06-15 Ultrasonic enhancement of aluminum step coverage and apparatus
JP7502942A JPH08511656A (en) 1993-06-17 1994-06-15 Ultrasonic strengthening of aluminum step coating and equipment
KR1019950705653A KR960703179A (en) 1993-06-17 1994-06-15 Ultrasonic Enhancement of Aluminum Step Coverage and Apparatus

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US7943893A 1993-06-17 1993-06-17
US08/079,438 1993-06-17

Publications (1)

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WO1995000676A1 true WO1995000676A1 (en) 1995-01-05

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US (1) US5520784A (en)
EP (1) EP0707662A4 (en)
JP (1) JPH08511656A (en)
KR (1) KR960703179A (en)
AU (1) AU7109694A (en)
CA (1) CA2162596A1 (en)
TW (1) TW239900B (en)
WO (1) WO1995000676A1 (en)

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US7253109B2 (en) * 1997-11-26 2007-08-07 Applied Materials, Inc. Method of depositing a tantalum nitride/tantalum diffusion barrier layer system
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US6766813B1 (en) * 2000-08-01 2004-07-27 Board Of Regents, The University Of Texas System Apparatus and method for cleaning a wafer
US6896774B2 (en) * 2003-03-06 2005-05-24 Intel Corporation Acoustic streaming of condensate during sputtered metal vapor deposition
US20100209623A1 (en) * 2009-02-18 2010-08-19 Electronics And Telecommunications Research Institute Apparatus for growing large area vanadium dioxide thin film and method of growing large area oxide thin film in the apparatus

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Also Published As

Publication number Publication date
EP0707662A1 (en) 1996-04-24
EP0707662A4 (en) 1998-02-25
TW239900B (en) 1995-02-01
CA2162596A1 (en) 1995-01-05
US5520784A (en) 1996-05-28
KR960703179A (en) 1996-06-19
AU7109694A (en) 1995-01-17
JPH08511656A (en) 1996-12-03

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