WO2007113104A1 - Novel pore-forming precursors composition and porous dielectric layers obtained there from - Google Patents

Novel pore-forming precursors composition and porous dielectric layers obtained there from Download PDF

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WO2007113104A1
WO2007113104A1 PCT/EP2007/052661 EP2007052661W WO2007113104A1 WO 2007113104 A1 WO2007113104 A1 WO 2007113104A1 EP 2007052661 W EP2007052661 W EP 2007052661W WO 2007113104 A1 WO2007113104 A1 WO 2007113104A1
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formula
methyl
linear
oxabicyclo
pore
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Joanne Deval
Manon Vautier
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Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Priority claimed from FR0651126A external-priority patent/FR2899379B1/en
Priority claimed from FR0653576A external-priority patent/FR2905517B1/en
Application filed by Air Liquide SA, LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Priority to US12/295,606 priority Critical patent/US20090136667A1/en
Priority to EP07727138A priority patent/EP2004872A1/en
Priority to JP2009502025A priority patent/JP4960439B2/en
Publication of WO2007113104A1 publication Critical patent/WO2007113104A1/en
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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
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/56—After-treatment
    • 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
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • 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
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C23C16/401—Oxides containing silicon
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/65—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by treatments performed before or after the formation of the materials
    • H10P14/6516—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by treatments performed before or after the formation of the materials of treatments performed after formation of the materials
    • H10P14/6529—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by treatments performed before or after the formation of the materials of treatments performed after formation of the materials by exposure to a gas or vapour
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/63—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the formation processes
    • H10P14/6326—Deposition processes
    • H10P14/6328—Deposition from the gas or vapour phase
    • H10P14/6334—Deposition from the gas or vapour phase using decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition
    • H10P14/6336—Deposition from the gas or vapour phase using decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition in the presence of a plasma [PECVD]
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/66—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the type of materials
    • H10P14/665—Porous materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/66—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the type of materials
    • H10P14/668—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the type of materials the materials being characterised by the deposition precursor materials
    • H10P14/6681—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the type of materials the materials being characterised by the deposition precursor materials the precursor containing a compound comprising Si
    • H10P14/6684—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the type of materials the materials being characterised by the deposition precursor materials the precursor containing a compound comprising Si the compound comprising silicon and oxygen
    • H10P14/6686—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the type of materials the materials being characterised by the deposition precursor materials the precursor containing a compound comprising Si the compound comprising silicon and oxygen the compound being a molecule comprising at least one silicon-oxygen bond and the compound having hydrogen or an organic group attached to the silicon or oxygen, e.g. a siloxane
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/69—Inorganic materials
    • H10P14/692—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses
    • H10P14/6921—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses containing silicon
    • H10P14/6922—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses containing silicon the material containing Si, O and at least one of H, N, C, F or other non-metal elements, e.g. SiOC, SiOC:H or SiONC

Definitions

  • the present invention relates to pore-forming precursors which are able to generate matter- free volumes in a dielectric and also to the dielectric porous layers thus formed.
  • the insulating dielectric layers also called “interlayer dielectrics" used to separate metal interconnects between the various electrical circuits of an integrated circuit should have increasingly low dielectric constants. For this, it is possible to create porosity in the dielectric itself (i.e. to create solid-matter- free micro-cavities) and thus to profit from the dielectric constant of air, which is equal to 1.
  • ULK ultra-low dielectric constant or ultra-low- k porous materials.
  • conventional low dielectric constant precursors also called matrix precursors, are associated, at the time of depositing, with organic compounds, which are organic pore-forming compounds which allow pores to be created in the "matrix" precursor.
  • the hybrid film which is obtained for example by plasma enhanced chemical vapor deposition (PECVD) on a semiconductor substrate, is then subjected to a specific treatment (heating, exposure to ultraviolet radiation, electron bombardment), which results in the removal of a certain number of chemical molecules from the film (the organic molecules and/or their thermal decomposition products) and which creates solid-matter-free cavities in the "matrix" dielectric film (for example, an SiOCH film).
  • PECVD plasma enhanced chemical vapor deposition
  • the dielectric matrix is largely detailed in the herein above referenced patents or patent applications ; it generally consists of a material deposited using precursor molecules containing silicon, carbon, oxygen and hydrogen atoms, more particularly siloxanes such as TMCTS (1,3,5,7—tetramethyl cyclotetrasiloxane), OMCTS (octamethyl cyclotetrasiloxane) or certain silane derivatives such as DEOMS (diethoxymethylsilane).;
  • siloxanes such as TMCTS (1,3,5,7—tetramethyl cyclotetrasiloxane), OMCTS (octamethyl cyclotetrasiloxane) or certain silane derivatives such as DEOMS (diethoxymethylsilane).
  • the latter step conditions the final success of the production of these films and the mechanical quality of the layers depends essentially on the choice of the combination of the matrix constitutive compounds and of the pore-forming compounds.
  • the hybrid material should preferably be at the same time, able to release matter under the effect of a treatment, to keep a stable framework during both this withdrawal step, and the subsequent semiconductor fabrication steps, in particular during the polishing steps of the dielectric layers.
  • the invention intends to solve the stated problem by virtue of the selection of suitable organic pore-forming compounds which, in combination with the matrix constitutive compounds, will generate a film on a substrate that has an ultra-low dielectric constant, while at the same time allowing the film to have a good mechanical strength.
  • the organic precursors according to the invention make it possible to solve the problem thus stated.
  • the invention relates to a method of forming a low dielectric porous film on a substrate, comprising reacting at least a film matrix precursor compound having silicon, carbon, oxygen and hydrogen atoms, and either at least a pore-forming compound, of the formula (I):
  • R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
  • the invention relates to a method as hereinbefore defined, wherein the pore-forming compound is a compound of the formula (Ia):
  • R represents a 2,4-dimethyl-3- cyclohexenyl radical, its positional and/or steric isomers and its derivatives, wherein one or more cyclic carbon atom is substituted by at least one alkyl radical having from one to six carbon atoms.
  • the porous layer of low dielectric constant k dielectric film obtained by the hereinabove defined from at least one film matrix precursor compound and at least one pore-forming compound as hereinbefore defined is characterized in that it is composed of a plurality of first volumes comprising solid matter consisting of film matrix precursor compound and/or of derived matter, in particular derived subsequent to a heat treatment, of a plurality of second volumes not comprising solid matter and of a plurality of third volumes, generally arranged between at least one first and at least one second volume and representing less than 1% of the total volume of the porous layer, these third volumes consisting of at least one fraction of pore- forming compound and/or of derived matter, which may or may not be linked to the matrix precursor.
  • the dielectric constant of said porous layer being less than or equal to 2.5.
  • derived matter is intended to mean the products derived from these precursors and which, subsequent to the treatment undergone by the layer, such as for example, heat treatment or ion bombardment, have been converted alone or on contact with the matrix molecules, so as to generate non-gaseous products which are incapable of being eliminated by diffusing through the layer, as the gaseous products derived from the decomposition of the organic precursors generally do.
  • the invention relates to a method as hereinbefore defined, wherein the said film matrix precursor compound is selected from siloxanes or silane derivatives and more particularly from TMCTS
  • This layer can be obtained by deposition on a substrate of the 300 mm wafer type in a "PECVD-type" reactor by injection of both the film matrix precursor compound and the pore-forming compound using a carrier gas, such as for example Helium, and then by heat treatment at a temperature below approximately 400 0 C.
  • a carrier gas such as for example Helium
  • pore-forming compounds according to the invention are the following: Some of the molecules hereinabove mentioned are commercially available and relatively inexpensive; they have a moderate toxicity, a good volatility, and a reactive chemical function, for example, a carbon-carbon double bound, an epoxy function or a carbonyl function. They are generally chemically stable enough for packaging, transport and/or storage, and do not require the addition of a stabilizer.
  • products which could be pore-forming compounds such as, for example, alpha-terpinene or l-isopropyl-4-methyl-l,3- cyclohexadiene, are not stable at the air exposure and suffer an oxidative degradation to produce some oxidized products, which could, in certain cases, also be pore-forming precursor materials for the production of low dielectric constant layers and that can also be used in the fabrication of semiconductors, while at the same time being stable to storage in the air and not liable to degrade.
  • pore-forming compounds such as, for example, alpha-terpinene or l-isopropyl-4-methyl-l,3- cyclohexadiene
  • One method of preparing these novel pore-forming compounds therefore consists, starting from alpha-terpinene or limonene, in oxidizing these products, preferably at a temperature above ambient temperature. Further details on such an oxidation is found, for example, in the article entitled “Thermal Degradation of Terrenes: Camphene's, ⁇ 3 -Careen, Limonene and CC- Trepanned”; Environ. Sic. Techno. - 1999, 33, 4029-4033 or in the article entitled “Determination of Limonene Oxidation Products using SPUME and GC-MS", Journal of Chromatographic Science, Vol. 41, January 2003.
  • Trivertal or 2,4-dimethyl-3-cyclohexane is a commercially available product, and is already in an oxidized state
  • a layer 2 was deposited, on a substrate 1, by the "PECVD” process, said layer consisting of a mixture of a "matrix” precursor 3 and of an organic precursor deposited using their gaseous phases.
  • the whole is subsequently subjected, in a manner known per se, to a heat treatment step, at a temperature of the order of approximately 300 0 C to 400 0 C, generally lasting several tens of minutes, possibly followed by an ion bombardment step, then optionally by a treatment in a moist atmosphere and they drying, as described, for example, in US-A-2005/0227502.
  • the matrix precursor volume 3 (also called first volume in the present application) generally consists of a single volume exhibiting continuity (giving the layer the desired mechanical strength), in which are located a plurality of second and third volumes 4 and 5.
  • the invention relates to a precursor mixture comprising at least a film matrix precursor compound having silicon, carbon, oxygen and hydrogen atoms, and either at least a pore-forming compound, of the formula (I):
  • R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
  • the invention relates to the use of a compound of the formula (I):
  • R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
  • porous layers which have a low dielectric constant usually less than 2.5 can be used in the fabrication of integrated circuits, flat screens, memories (in particular "random access” memories) and in any similar applications in which a low dielectric constant dielectric layer is used to isolate two electrical components
  • dielectric interconnection layers are electrical interconnection layers. They will more particularly be used in the circuits for interconnecting the various components of an integrated circuit, called BEOL ("Back end of the line").
  • Porous low k films have been obtained using the following process and conditions: The deposits were performed on a 6" plasma enhanced chemical vapor deposition (PECVD) reactor. Hybrid films obtained were then annealed in a tube furnace at temperatures between 400 0 C to 470 0 C for 15 to 60 minutes under N2 flow, with additives such as H2 or 02 at concentrations between 1% and 20%.
  • PECVD plasma enhanced chemical vapor deposition
  • Thickness and refractive index were measured on a Filmmetrics reflectometer. Dielectric constants were determined using a MDC mercury probe with a HP capacimeter.
  • Deposition was performed at pressures between 0.5 and 2 Torr, with radio- frequency power between IOOW and 250W at 13.56 MHz, by co-depositing a Si- based precursor (diethoxymethylsilane) with described pore-forming compounds (Trivertal) onto a silicon wafer.
  • Si- based precursor diethoxymethylsilane
  • Trivertal pore-forming compounds
  • Flow rates of diethoxymethylsilane and pore-forming compound were varying in the range 125-500 mg/min (TEOS equivalent on a thermal mass-flow meter). Helium was used at 500sccm as carrier gas. Deposition times ranges between 30s and 7 min. Thickness between lOOnm and 700nm was obtained. After annealing, thickness between 100 and 600nm was obtained. Refractive index between 1.29 and 1.35 was obtained, and k value between 2.1 and 2.5

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  • Engineering & Computer Science (AREA)
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  • General Chemical & Material Sciences (AREA)
  • Metallurgy (AREA)
  • Inorganic Chemistry (AREA)
  • Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
  • Formation Of Insulating Films (AREA)
  • Silicon Polymers (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Other Resins Obtained By Reactions Not Involving Carbon-To-Carbon Unsaturated Bonds (AREA)
  • Chemical Vapour Deposition (AREA)

Abstract

Method of forming a low dielectric k porous film on a substrate, comprising reacting at least a film matrix precursor compound having silicon, carbon, oxygen and hydrogen atoms, and either at least a pore-forming compound, of the formula (I) wherein R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, or at least one of the following pore-forming compounds: l-methyl-4-(l -methyl ethyl)-7-oxabicyclo[2.2.1.]heptane,1,3,3-trimethyl-2-oxabicyclo[2.2.1.]octane or 1,8-cineole, or l-methyl-4-(l -methyl ethenyl)-7-oxabicyclo[4.1.0.]heptane; New precursor precursor mixture, and the use of a compound of formula (I), as a pore- forming compound in a chemical vapor deposition of a low dielectric k film on a substrate.

Description

Novel pore-forming precursors composition and porous dielectric layers obtained there from
The present invention relates to pore-forming precursors which are able to generate matter- free volumes in a dielectric and also to the dielectric porous layers thus formed.
The insulating dielectric layers (also called "interlayer dielectrics") used to separate metal interconnects between the various electrical circuits of an integrated circuit should have increasingly low dielectric constants. For this, it is possible to create porosity in the dielectric itself (i.e. to create solid-matter- free micro-cavities) and thus to profit from the dielectric constant of air, which is equal to 1.
Reference is then made to ULK (or ultra-low dielectric constant or ultra-low- k) porous materials. In order to produce such porous layers, conventional low dielectric constant precursors, also called matrix precursors, are associated, at the time of depositing, with organic compounds, which are organic pore-forming compounds which allow pores to be created in the "matrix" precursor.
The hybrid film, which is obtained for example by plasma enhanced chemical vapor deposition (PECVD) on a semiconductor substrate, is then subjected to a specific treatment (heating, exposure to ultraviolet radiation, electron bombardment), which results in the removal of a certain number of chemical molecules from the film (the organic molecules and/or their thermal decomposition products) and which creates solid-matter-free cavities in the "matrix" dielectric film (for example, an SiOCH film). For further details on the formation of these films reference may be made, for example, to international Application WO 2005/112095, or to United States Patent Application Nr. US-A-2002/037442 or to United States Patent Nr. 6,312,793.
The objective of such films is to create a porosity in the dielectric matrix, without the structure of the film collapsing, i.e. to obtain a film that still has sufficient mechanical properties; the dielectric matrix is largely detailed in the herein above referenced patents or patent applications ; it generally consists of a material deposited using precursor molecules containing silicon, carbon, oxygen and hydrogen atoms, more particularly siloxanes such as TMCTS (1,3,5,7—tetramethyl cyclotetrasiloxane), OMCTS (octamethyl cyclotetrasiloxane) or certain silane derivatives such as DEOMS (diethoxymethylsilane).;
The latter step conditions the final success of the production of these films and the mechanical quality of the layers depends essentially on the choice of the combination of the matrix constitutive compounds and of the pore-forming compounds.
The hybrid material should preferably be at the same time, able to release matter under the effect of a treatment, to keep a stable framework during both this withdrawal step, and the subsequent semiconductor fabrication steps, in particular during the polishing steps of the dielectric layers.
The invention intends to solve the stated problem by virtue of the selection of suitable organic pore-forming compounds which, in combination with the matrix constitutive compounds, will generate a film on a substrate that has an ultra-low dielectric constant, while at the same time allowing the film to have a good mechanical strength.
The organic precursors according to the invention make it possible to solve the problem thus stated.
According to a first embodiment, the invention relates to a method of forming a low dielectric porous film on a substrate, comprising reacting at least a film matrix precursor compound having silicon, carbon, oxygen and hydrogen atoms, and either at least a pore-forming compound, of the formula (I):
Figure imgf000004_0001
wherein R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
- linear or branched alkyl radicals having from 1 to 4 carbon atoms; - linear or branched alkanoyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl oxy radicals having from 1 to 4 carbon atoms; or at least one of the following pore-forming compounds: l-methyl-4-(l -methyl ethyl)-7-oxabicyclo[2.2.1]heptane (more commonly known as 1,4-cineole) of the formula (II):
Figure imgf000005_0001
1,4 - cineole
(H) l,3,3-trimethyl-2-oxabicyclo[2.2.1]octane, or 1,8-cineole (or eucalyptol) of the formula:
Figure imgf000005_0002
1 ,8 - cineole
(in)
- or l-methyl-4-(l -methyl ethenyl)-7-oxabicyclo[4.1.0.]heptane, or limonene epoxide of the formula (IV):
Figure imgf000005_0003
limonene epoxide
(IV). According to a more specific embodiment, the invention relates to a method as hereinbefore defined, wherein the pore-forming compound is a compound of the formula (Ia):
2,4-dimethyl-3-cyclohexene carboxaldehyde, or trivertal
Figure imgf000006_0001
trivertal
(Ia)
corresponding to the formula (I), wherein R represents a 2,4-dimethyl-3- cyclohexenyl radical, its positional and/or steric isomers and its derivatives, wherein one or more cyclic carbon atom is substituted by at least one alkyl radical having from one to six carbon atoms.
The porous layer of low dielectric constant k dielectric film obtained by the hereinabove defined from at least one film matrix precursor compound and at least one pore-forming compound as hereinbefore defined, is characterized in that it is composed of a plurality of first volumes comprising solid matter consisting of film matrix precursor compound and/or of derived matter, in particular derived subsequent to a heat treatment, of a plurality of second volumes not comprising solid matter and of a plurality of third volumes, generally arranged between at least one first and at least one second volume and representing less than 1% of the total volume of the porous layer, these third volumes consisting of at least one fraction of pore- forming compound and/or of derived matter, which may or may not be linked to the matrix precursor. The dielectric constant of said porous layer being less than or equal to 2.5. The term "derived matter" is intended to mean the products derived from these precursors and which, subsequent to the treatment undergone by the layer, such as for example, heat treatment or ion bombardment, have been converted alone or on contact with the matrix molecules, so as to generate non-gaseous products which are incapable of being eliminated by diffusing through the layer, as the gaseous products derived from the decomposition of the organic precursors generally do.
According to a particular embodiment, the invention relates to a method as hereinbefore defined, wherein the said film matrix precursor compound is selected from siloxanes or silane derivatives and more particularly from TMCTS
(1,3,5,7-tetramethyl cyclotetrasiloxane), OMCTS (octamethyl cyclotetrasiloxane) and DEOMS (diethoxymethylsilane);
This layer can be obtained by deposition on a substrate of the 300 mm wafer type in a "PECVD-type" reactor by injection of both the film matrix precursor compound and the pore-forming compound using a carrier gas, such as for example Helium, and then by heat treatment at a temperature below approximately 4000C.
The advantages of the pore-forming compounds according to the invention are the following: Some of the molecules hereinabove mentioned are commercially available and relatively inexpensive; they have a moderate toxicity, a good volatility, and a reactive chemical function, for example, a carbon-carbon double bound, an epoxy function or a carbonyl function. They are generally chemically stable enough for packaging, transport and/or storage, and do not require the addition of a stabilizer.
However, it was observed that products which could be pore-forming compounds, such as, for example, alpha-terpinene or l-isopropyl-4-methyl-l,3- cyclohexadiene, are not stable at the air exposure and suffer an oxidative degradation to produce some oxidized products, which could, in certain cases, also be pore-forming precursor materials for the production of low dielectric constant layers and that can also be used in the fabrication of semiconductors, while at the same time being stable to storage in the air and not liable to degrade.
One method of preparing these novel pore-forming compounds therefore consists, starting from alpha-terpinene or limonene, in oxidizing these products, preferably at a temperature above ambient temperature. Further details on such an oxidation is found, for example, in the article entitled "Thermal Degradation of Terrenes: Camphene's, Δ3-Careen, Limonene and CC- Trepanned"; Environ. Sic. Techno. - 1999, 33, 4029-4033 or in the article entitled "Determination of Limonene Oxidation Products using SPUME and GC-MS", Journal of Chromatographic Science, Vol. 41, January 2003.
In particular, it has been demonstrated that, starting from the oxidation of alpha-trepanned, it is possible to generate:
- 1,4-cineole, or l-(l-methyl ethyl)-4-methyl-7-oxabicyclo[2.2.1.]heptane, a molecule of low toxicity;
1,8-cineole, or eucalyptol, or else l,3,3-tri-methyl-2- oxabicyclo[2.2.2.]octane, a molecule which is itself also of very low toxicity
Figure imgf000008_0001
alpha-terpinene 1,4 - cineole
Figure imgf000008_0002
alpha-terpinene 1,8 - cineole
oxidation of alpha-terpinene
Similarly, starting from limonene, it is possible to generate: limonene oxide or 4-isopropenyl-l -methyl- l-cyclo-hexene-l,2-epoxide:
Figure imgf000009_0001
limonene limonene epoxide oxidation of limonene to limonene epoxide
Trivertal or 2,4-dimethyl-3-cyclohexane, is a commercially available product, and is already in an oxidized state
Figure imgf000009_0002
trivertal
The single figure schematically shows the porous layer obtained according to the invention: A layer 2 was deposited, on a substrate 1, by the "PECVD" process, said layer consisting of a mixture of a "matrix" precursor 3 and of an organic precursor deposited using their gaseous phases. The whole is subsequently subjected, in a manner known per se, to a heat treatment step, at a temperature of the order of approximately 3000C to 4000C, generally lasting several tens of minutes, possibly followed by an ion bombardment step, then optionally by a treatment in a moist atmosphere and they drying, as described, for example, in US-A-2005/0227502. In the course of the heat treatment, the organic precursor is decomposed under the effect of the heat, giving rise to matter- free cavities 4, with, however, a few volumes 5 in which it is possible to identify residual organic matter that has not been completely decomposed, these volumes 5 being located between the matrix precursor volume 3 and the matter- free volumes 4. These volumes 5 will preferably always represent less than 1 vol% of the layer after thermal (or other) treatment, more preferably less than a few hundred ppm. The matrix precursor volume 3 (also called first volume in the present application) generally consists of a single volume exhibiting continuity (giving the layer the desired mechanical strength), in which are located a plurality of second and third volumes 4 and 5.
According to another embodiment the invention relates to a precursor mixture comprising at least a film matrix precursor compound having silicon, carbon, oxygen and hydrogen atoms, and either at least a pore-forming compound, of the formula (I):
Figure imgf000010_0001
wherein R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
- linear or branched alkyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl oxy radicals having from 1 to 4 carbon atoms; or at least one of the following pore-forming compounds: l-methyl-4-(l -methyl ethyl)-7-oxabicyclo[2.2.1.]heptane of the formula (II):
Figure imgf000010_0002
1,4 - cineole
(H) l,3,3-trimethyl-2-oxabicyclo[2.2.1.]octane, or 1,8-cineole (or eucalyptol) of the formula:
Figure imgf000011_0001
1 ,8 - cineole (III)
- or l-methyl-4-(l -methyl ethenyl)-7-oxabicyclo[4.1.0.]heptane or limonene epoxide of the formula (IV):
Figure imgf000011_0002
limonene epoxide
(IV), and more specifically to a precursor mixture as hereinabove defined, wherein the pore- forming compound is a compound of the formula (Ia):
Figure imgf000011_0003
trivertal
(Ia) corresponding to the formula (I), wherein R represents a 2,4-dimethyl-3- cyclohexenyl radical.
According to another embodiment, the invention relates to the use of a compound of the formula (I):
Figure imgf000012_0001
(I)
wherein R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
- linear or branched alkyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl radicals having from 1 to 4 carbon atoms; - linear or branched alkanoyl oxy radicals having from 1 to 4 carbon atoms; or of the following compounds: l-methyl-4-(l -methyl ethyl)-7-oxabicyclo[2.2.1.]heptane of the formula (II):
Figure imgf000012_0002
1 A - cineole (II) l,3,3-trimethyl-2-oxabicyclo[2.2.1.]octane, or 1,8-cineole (or eucalyptol) of the formula:
Figure imgf000013_0001
1 ,8 - cineole
(III)
- or l-methyl-4-(l -methyl ethenyl)-7-oxabicyclo[4.1.0.]heptane or limonene epoxide of the formula (IV):
Figure imgf000013_0002
limonene epoxide
(IV).
as a pore-forming compound in a chemical vapor deposition of a low dielectric k film on a substrate.
These porous layers which have a low dielectric constant usually less than 2.5 can be used in the fabrication of integrated circuits, flat screens, memories (in particular "random access" memories) and in any similar applications in which a low dielectric constant dielectric layer is used to isolate two electrical components
(dielectric interconnection layers). They will more particularly be used in the circuits for interconnecting the various components of an integrated circuit, called BEOL ("Back end of the line").
Porous low k films have been obtained using the following process and conditions: The deposits were performed on a 6" plasma enhanced chemical vapor deposition (PECVD) reactor. Hybrid films obtained were then annealed in a tube furnace at temperatures between 4000C to 4700C for 15 to 60 minutes under N2 flow, with additives such as H2 or 02 at concentrations between 1% and 20%.
Thickness and refractive index were measured on a Filmmetrics reflectometer. Dielectric constants were determined using a MDC mercury probe with a HP capacimeter.
Deposition was performed at pressures between 0.5 and 2 Torr, with radio- frequency power between IOOW and 250W at 13.56 MHz, by co-depositing a Si- based precursor (diethoxymethylsilane) with described pore-forming compounds (Trivertal) onto a silicon wafer.
Flow rates of diethoxymethylsilane and pore-forming compound were varying in the range 125-500 mg/min (TEOS equivalent on a thermal mass-flow meter). Helium was used at 500sccm as carrier gas. Deposition times ranges between 30s and 7 min. Thickness between lOOnm and 700nm was obtained. After annealing, thickness between 100 and 600nm was obtained. Refractive index between 1.29 and 1.35 was obtained, and k value between 2.1 and 2.5

Claims

Claims
1. Method of forming a low dielectric k porous film on a substrate, comprising reacting at least a film matrix precursor compound having silicon, carbon, oxygen and hydrogen atoms, and either at least a pore-forming compound, of the formula (I):
Figure imgf000015_0001
wherein R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
- linear or branched alkyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl oxy radicals having from 1 to 4 carbon atoms; or at least one of the following pore-forming compounds: l-methyl-4-(l -methyl ethyl)-7-oxabicyclo[2.2.1.]heptane of the formula (II):
Figure imgf000015_0002
1,4 - cineole
(H) l,3,3-trimethyl-2-oxabicyclo[2.2.1.]octane or 1,8-cineole (or eucalyptol) of the formula:
Figure imgf000016_0001
1 ,8 - cineole
(III)
- or l-methyl-4-(l -methyl ethenyl)-7-oxabicyclo[4.1.0.]heptane or limonene epoxide of the formula (IV):
Figure imgf000016_0002
limonene epoxide
(IV).
2. Method according to Claim 2, wherein the pore-forming compound is a compound of the formula (Ia):
Figure imgf000017_0001
trivertal
(Ia)
corresponding to the formula (I), wherein R represents a 2,4-dimethyl-3- cyclohexenyl radical.
3. Method according to Claim 1 or to Claim 2, wherein the said film matrix precursor compound is selected from siloxanes or silane derivatives.
4. Method according to claim 3, wherein the said film matrix precursor compound is selected from TMCTS (1,3,5,7-tetramethyl cyclotetrasiloxane),
OMCTS (octamethyl cyclotetrasiloxane) and DEOMS (diethoxymethylsilane).
5. Precursor mixture comprising at least a film matrix precursor compound having silicon, carbon, oxygen and hydrogen atoms, and either at least a pore- forming compound, of the formula (I):
Figure imgf000017_0002
wherein R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or unsaturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from: - linear or branched alkyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl oxy radicals having from 1 to 4 carbon atoms; or at least one of the following pore-forming compounds: l-methyl-4-(l -methyl ethyl)-7-oxabicyclo[2.2.1]heptane of the formula (II):
Figure imgf000018_0001
1,4 - cineole
(H)
l,3,3-trimethyl-2-oxabicyclo[2.2.1]octane or 1,8-cineole (or eucalyptol) of the formula:
Figure imgf000018_0002
1 ,8 - cineole
(in)
- or l-methyl-4-(l -methyl ethenyl)-7-oxabicyclo[4.1.0]heptane or limonene epoxide of the formula (IV):
Figure imgf000019_0001
limonene epoxide
(IV).
6. Precursor mixture as defined in Claim 5, wherein the pore-forming compound is a compound of the formula (Ia):
Figure imgf000019_0002
trivertal
(Ia)
corresponding to the formula (I), wherein R represents a 2,4-dimethyl-3- cyclohexenyl radical.
7. Use of a compound of the formula (I):
Figure imgf000019_0003
(I) wherein R represents: either a linear or branched, saturated or non saturated hydrocarbon radical, or a cyclic saturated or non saturated hydrocarbon radical, said cyclic or non cyclic radical being not substituted or substituted by one or more radicals selected from:
- linear or branched alkyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl radicals having from 1 to 4 carbon atoms;
- linear or branched alkanoyl oxy radicals having from 1 to 4 carbon atoms; or of the following compounds: l-methyl-4-(l -methyl ethyl)-7-oxabicyclo[2.2.1]heptane of the formula (II):
Figure imgf000020_0001
1,4 - cineole
(H)
l,3,3-trimethyl-2-oxabicyclo[2.2.1]octane, or 1,8-cineole (or eucalyptol) of the formula:
Figure imgf000020_0002
1 ,8 - cineole .„,. - or l-methyl-4-(l -methyl ethenyl)-7-oxabicyclo[4.1.0]heptane or limonene epoxide of the formula (IV):
Figure imgf000021_0001
limonene epoxide
(IV).
as a pore-forming compound in a chemical vapor deposition of a low dielectric k film on a substrate.
PCT/EP2007/052661 2006-03-31 2007-03-20 Novel pore-forming precursors composition and porous dielectric layers obtained there from Ceased WO2007113104A1 (en)

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