CN114649293A - Copper-tungsten electrical connection structure and forming method thereof - Google Patents

Copper-tungsten electrical connection structure and forming method thereof Download PDF

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Publication number
CN114649293A
CN114649293A CN202011501441.1A CN202011501441A CN114649293A CN 114649293 A CN114649293 A CN 114649293A CN 202011501441 A CN202011501441 A CN 202011501441A CN 114649293 A CN114649293 A CN 114649293A
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layer
barrier layer
copper
tungsten
forming
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胡杏
邹文
贺忻
李朝勇
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Galaxycore Shanghai Ltd Corp
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Galaxycore Shanghai Ltd Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
    • H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
    • H01L23/5226—Via connections in a multilevel interconnection structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/76841—Barrier, adhesion or liner layers
    • H01L21/76843—Barrier, adhesion or liner layers formed in openings in a dielectric
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/76841—Barrier, adhesion or liner layers
    • H01L21/76843—Barrier, adhesion or liner layers formed in openings in a dielectric
    • H01L21/76846—Layer combinations
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
    • H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
    • H01L23/532—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body characterised by the materials
    • H01L23/53204—Conductive materials
    • H01L23/53209—Conductive materials based on metals, e.g. alloys, metal silicides
    • H01L23/53228—Conductive materials based on metals, e.g. alloys, metal silicides the principal metal being copper
    • H01L23/53238—Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
    • H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
    • H01L23/532—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body characterised by the materials
    • H01L23/53204—Conductive materials
    • H01L23/53209—Conductive materials based on metals, e.g. alloys, metal silicides
    • H01L23/53257—Conductive materials based on metals, e.g. alloys, metal silicides the principal metal being a refractory metal
    • H01L23/53266—Additional layers associated with refractory-metal layers, e.g. adhesion, barrier, cladding layers

Abstract

A copper-tungsten electrical connection structure and a method of forming the same, the method comprising: forming a first barrier layer on the surface of the copper layer; forming a buffer layer on the surface of the first barrier layer; forming a second barrier layer on the surface of the buffer layer; and the tungsten layer is formed on the surface of the second barrier layer. The invention can meet various requirements of preventing metal diffusion, improving the stability of devices, reducing the production cost and the like.

Description

Copper-tungsten electrical connection structure and forming method thereof
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to a copper-tungsten electric connection structure and a forming method thereof.
Background
With the increase of integration level of semiconductor technology, the size of transistors is continuously reduced, and the complexity of interconnections in devices is further increased. Considering that the relative area provided by the surface energy of the wafer decreases with the size reduction, higher requirements are placed on the density and integration of the metal interconnects.
Taking the current multi-heavy metal interconnect process as an example, the process combination of via and metal plug is widely used due to its higher integration and better step coverage. Specifically, as the integration of bonded wafers increases, the size of through silicon vias needs to be reduced, and the aspect ratio of the through silicon vias needs to be increased. The metal plug can be used for connecting upper and lower layers of metal to realize the metal interconnection function.
It should be noted that the metal filled in the through hole is easily diffused to the upper metal layer or the lower metal layer, which affects the conductivity. In the prior art, a barrier layer can be formed to prevent metal diffusion, however, the prior barrier layer often has the problem of poor stability with adjacent materials or the problem of high production cost.
A method for forming a copper-tungsten electrical connection structure is urgently needed to satisfy various requirements of preventing metal diffusion, improving device stability, reducing production cost and the like.
Disclosure of Invention
The invention aims to provide a copper-tungsten electric connection structure and a forming method thereof, which can meet various requirements of preventing metal diffusion, improving the stability of a device, reducing the production cost and the like.
To solve the above technical problem, an embodiment of the present invention provides a method for forming a copper-tungsten electrical connection structure, including: forming a first barrier layer on the surface of the copper layer; forming a buffer layer on the surface of the first barrier layer; forming a second barrier layer on the surface of the buffer layer; and the tungsten layer is formed on the surface of the second barrier layer.
Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: tantalum nitride and tantalum silicon nitride; the buffer layer is made of tantalum; the material of the second barrier layer is selected from: tantalum nitride and tantalum silicon nitride.
Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: titanium nitride and titanium silicon nitride; the buffer layer is made of titanium; the material of the second barrier layer is selected from: titanium nitride and titanium silicon nitride.
Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: tungsten nitride; the buffer layer is made of titanium and/or tantalum; the material of the second barrier layer is selected from: tungsten nitride.
Optionally, before forming the first barrier layer on the surface of the copper layer, the method for forming the copper-tungsten electrical connection structure further includes: and cleaning the surface of the copper layer by adopting a reactive plasma cleaning process.
Optionally, the process parameters of the reactive plasma cleaning process are selected from one or more of the following: the process temperature is 30-200 ℃; the air pressure in the process chamber is 20-60 mTorr; the control power is 400-1200W; the gas in the process chamber comprises argon, helium and a hydrogen-containing gas.
Optionally, the copper-tungsten electrical connection structure is used to form a plug structure, and one end of the plug structure is connected to the surface of the copper layer; wherein the first barrier layer is further formed on an inner sidewall surface of the plug structure.
Optionally, the process of forming the second barrier layer on the surface of the buffer layer is selected from: when the depth-to-width ratio of the through hole for filling the plug structure is smaller than a preset threshold value, forming the second barrier layer by adopting a physical vapor deposition process; and when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold value, forming the second barrier layer by adopting a chemical vapor deposition process or an atomic layer deposition process.
Optionally, before forming the first barrier layer on the surface of the copper layer, the method for forming the copper-tungsten electrical connection structure further includes: providing a semiconductor substrate; forming a crystal face dielectric layer, a copper layer and a crystal back dielectric layer, wherein the crystal face dielectric layer is positioned on the first surface of the semiconductor substrate, and the crystal back dielectric layer is positioned on the second surface of the semiconductor substrate; forming a through hole penetrating through the crystal face dielectric layer, the semiconductor substrate and a part of the crystal back dielectric layer, wherein the bottom surface of the through hole is exposed out of the surface of the copper layer; forming a side wall dielectric layer on the surface of the inner side wall of the through hole; and the first barrier layer is also formed on the surface of the side wall dielectric layer.
To solve the above technical problem, an embodiment of the present invention provides a copper-tungsten electrical connection structure, including: the first barrier layer is positioned on the surface of the copper layer; the buffer layer is positioned on the surface of the first barrier layer; the second barrier layer is positioned on the surface of the buffer layer; wherein the tungsten layer is formed on the surface of the second barrier layer.
Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: tantalum nitride and tantalum silicon nitride; the buffer layer is made of tantalum; the material of the second barrier layer is selected from: tantalum nitride and tantalum silicon nitride.
Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: titanium nitride and titanium silicon nitride; the buffer layer is made of titanium; the material of the second barrier layer is selected from: titanium nitride and titanium silicon nitride.
Optionally, one or more of the following are satisfied: the material of the first barrier layer is selected from: tungsten nitride; the buffer layer is made of titanium and/or tantalum; the material of the second barrier layer is selected from: tungsten nitride.
Optionally, the copper-tungsten electrical connection structure is used for forming a plug structure, and one end of the plug structure is connected to the surface of the copper layer; wherein the first barrier layer is located on an inner sidewall surface of the plug structure.
Optionally, the forming process of the second barrier layer is selected from: when the aspect ratio of the through hole for filling the plug structure is smaller than a preset threshold value, the forming process of the second barrier layer is a physical vapor deposition process; and when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold value, the forming process of the second barrier layer is a chemical vapor deposition process or an atomic layer deposition process.
Optionally, the copper-tungsten electrical connection structure further includes: a semiconductor substrate; the semiconductor device comprises a crystal face dielectric layer, a copper layer and a crystal back dielectric layer, wherein the crystal face dielectric layer is positioned on a first surface of a semiconductor substrate, and the crystal back dielectric layer is positioned on a second surface of the semiconductor substrate; the through hole penetrates through the crystal face dielectric layer, the semiconductor substrate and a part of the crystal back dielectric layer, and the bottom surface of the through hole is exposed out of the surface of the copper layer; the side wall dielectric layer is positioned on the surface of the inner side wall of the through hole; and the first barrier layer is also formed on the surface of the side wall dielectric layer.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
in the embodiment of the invention, the first barrier layer, the buffer layer and the second barrier layer are sequentially arranged to serve as the electric connection structure between copper and tungsten, so that metal diffusion can be prevented by using the first barrier layer and the second barrier layer, and a good contact surface is provided for the first barrier layer and the second barrier layer by using the buffer layer, so that the stability and the reliability of the whole structure are improved, and various requirements of preventing metal diffusion, improving the stability of a device, reducing the production cost and the like are met.
Further, in an embodiment of the present invention, the material of the first barrier layer is selected from: tantalum nitride and tantalum silicon nitride (TaSiN); the buffer layer is made of tantalum; the material of the second barrier layer is selected from: tantalum nitride and tantalum silicon nitride. Because tantalum nitride and tantalum silicon nitride have better barrier property to copper diffusion and have better adhesiveness with copper, the contact resistance can be reduced while good contact with metal copper is realized. The tantalum is used as the buffer layer, so that the effects of balancing stress and absorbing stress of the upper layer material and the lower layer material can be achieved, a good contact surface can be provided for the second barrier layer, and the stability and the reliability of the whole structure can be improved. Because tantalum nitride and tantalum silicon nitride have better barrier property to tungsten diffusion and contact resistance with tungsten is lower, the metal tungsten diffusion can be prevented. And the tantalum nitride has a lower resistance temperature coefficient, the resistance change caused by the tantalum nitride along with the temperature change is smaller, in addition, the deposition of the metal tungsten on the tantalum nitride is not influenced by the surface roughness of the tantalum nitride, and the thickness consistency of the metal tungsten is better.
Further, in an embodiment of the present invention, the material of the first barrier layer is selected from: titanium nitride and titanium silicon nitride; the buffer layer is made of titanium; the material of the second barrier layer is selected from: titanium nitride and titanium silicon nitride. Titanium nitride and titanium silicon nitride have better barrier property to copper diffusion and tungsten diffusion, and the resistance of titanium nitride is smaller, for example, the resistance of titanium nitride is smaller than that of tantalum nitride under the condition of the same thickness, so that the electrical property of the device is improved. Compared with the prior art that the single-layer titanium nitride is adopted to block copper diffusion and tungsten diffusion, and the problems of falling, breaking and the like caused by stress are possible.
Further, in an embodiment of the present invention, the material of the first barrier layer is selected from: tungsten nitride; the buffer layer is made of titanium and/or tantalum; the material of the second barrier layer is selected from: tungsten nitride. Tungsten nitride all has better barrier property to copper diffusion and tungsten diffusion, and its barrier capacity is greater than tantalum nitride and titanium nitride even when thickness is less, when copper tungsten electric connection structure is used for forming the plug structure, if be used for filling when the size of the through-hole of plug structure is less (for example less than 600nm), owing to be provided with barrier layer and buffer layer, can show and reduce actual through-hole size, influence through-hole resistance, form the tungsten nitride thin layer through adopting atomic layer deposition technology this moment, help satisfying through-hole size and block the demand simultaneously. And the buffer layer is added between the tungsten nitride, so that the effects of balancing the stress of the upper layer material and the lower layer material and absorbing the stress can be achieved, and the stability and the reliability of the whole structure can be improved.
Further, the process for forming the second barrier layer on the surface of the buffer layer is selected from: when the aspect ratio of the through hole for filling the plug structure is smaller than a preset threshold (for example, the aspect ratio of the filling hole is smaller than 1:3), a physical vapor deposition process is adopted to form the second barrier layer, and the second barrier layer is preferentially selected to be subjected to physical vapor deposition, so that the whole process flow is simpler, the whole process of tantalum nitride, tantalum and tantalum nitride can be completed in one reaction cavity, and the problems of large contact resistance, reliability and the like caused by oxidation of some metal surfaces due to vacuum breaking can be avoided; when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold (for example, the aspect ratio of the filling hole is greater than or equal to 1:3), the second barrier layer is formed by adopting a chemical vapor deposition process or an atomic layer deposition process, and the two methods have better step coverage. Atomic layer deposition can deposit thinner thickness, which can effectively reduce contact resistance.
Further, a through hole penetrating through the crystal face dielectric layer, the semiconductor substrate and a part of the crystal back dielectric layer can be formed, the surface of the copper layer is exposed out of the bottom surface of the through hole, a side wall dielectric layer is formed on the surface of the inner side wall of the through hole, and the first barrier layer is formed on the surface of the side wall dielectric layer besides the surface of the copper layer, so that the copper-tungsten electric connection structure forms a plug structure filled in the silicon through hole, and the electric performance of the plug structure is improved.
Drawings
FIG. 1 is a flow chart of a method for forming a copper-tungsten electrical connection structure according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of a copper-tungsten electrical connection structure according to an embodiment of the present invention;
fig. 3 to fig. 5 are schematic cross-sectional views of devices corresponding to steps in a method for forming a copper-tungsten electrical connection structure according to an embodiment of the invention.
Detailed Description
As described above, the metal filled in the via hole is easily diffused to the upper metal layer or the lower metal layer, which affects the conductivity.
The inventor of the present invention has found that, in the prior art, a barrier layer can be formed to prevent metal diffusion, however, the prior barrier layer often has a problem of poor stability with adjacent materials (such as metal filled in a via hole, an upper metal layer or a lower metal layer), for example, a single barrier layer is adopted to cause excessive stress. There may also be a problem in that the production cost is high, for example, an adhesion layer between the barrier layer and the metal layer is formed using an additional adhesion material, resulting in an increase in the production cost.
In the embodiment of the invention, the first barrier layer, the buffer layer and the second barrier layer are sequentially arranged to serve as the electric connection structure between copper and tungsten, so that metal diffusion can be prevented by using the first barrier layer and the second barrier layer, and a good contact surface is provided for the first barrier layer and the second barrier layer by using the buffer layer, so that the stability and the reliability of the whole structure are improved, and various requirements of preventing metal diffusion, improving the stability of a device, reducing the production cost and the like are met.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, fig. 1 is a flowchart illustrating a method for forming a copper-tungsten electrical connection structure according to an embodiment of the present invention. The method for forming the copper-tungsten electrical connection structure may include steps S11 to S13:
step S11: forming a first barrier layer on the surface of the copper layer;
step S12: forming a buffer layer on the surface of the first barrier layer;
step S13: and forming a second barrier layer on the surface of the buffer layer, wherein the tungsten layer is formed on the surface of the second barrier layer.
The above steps will be described with reference to fig. 2.
Referring to fig. 2, fig. 2 is a schematic cross-sectional structure diagram of a copper-tungsten electrical connection structure according to an embodiment of the present invention.
Specifically, the copper-tungsten electrical connection structure may include a first barrier layer 102, a buffer layer 103, and a second barrier layer 105.
The first barrier layer 102 may be formed on a surface of the copper layer 101, a buffer layer 103 may be formed on the surface of the first barrier layer 102, a second barrier layer 104 may be formed on the surface of the buffer layer 103, and a tungsten layer 105 may be formed on the surface of the second barrier layer 104.
Further, the first barrier layer 102 has a barrier capability against copper diffusion, thereby realizing a function of blocking copper diffusion.
Further, the adhesion between the first barrier layer 102 and the copper is greater than or equal to a first predetermined adhesion threshold.
In the embodiment of the invention, the first barrier layer 102 is arranged to have better adhesion with copper, so that good contact with metal copper can be realized.
Further, the stress of the buffer layer 103 may be smaller than a predetermined stress range.
In the embodiment of the present invention, by setting the stress of the buffer layer 103 to be smaller than the preset stress range, the effects of equalizing the stress of the upper and lower layer materials and absorbing the stress can be achieved, and a good contact surface can be provided for the second barrier layer 104, which is beneficial to improving the stability and reliability of the whole structure.
Further, the second barrier layer 104 has a barrier capability against tungsten diffusion, thereby achieving a function of blocking tungsten diffusion.
Further, the adhesion between the second barrier layer 104 and the tungsten is greater than or equal to a second predetermined adhesion threshold.
In the embodiment of the present invention, by setting the second barrier layer 104 to have a better adhesion property with tungsten, good contact with metal tungsten can be achieved, and compared with the prior art in which an adhesion layer between a barrier layer and a metal layer is formed by using an additional adhesion material, by using the technical scheme of the embodiment of the present invention, diffusion of metal tungsten can be prevented, and production cost can be reduced.
In a first specific implementation of an embodiment of the present invention, the material of which the first barrier layer 102 may be provided is selected from: tantalum nitride and tantalum silicon nitride; the buffer layer 103 is made of tantalum; the material of the second barrier layer 104 is selected from: tantalum nitride and tantalum silicon nitride.
In the embodiment of the invention, because the tantalum nitride and the tantalum silicon nitride (TaSiN) have better barrier property to copper diffusion and better adhesion between the tantalum nitride and the tantalum silicon nitride (TaSiN) and copper, the contact resistance can be reduced while good contact with metal copper is realized. The tantalum is used as the buffer layer 103, so that the stress and the absorption stress of the upper layer material and the lower layer material can be balanced, a good contact surface can be provided for the second barrier layer, and the stability and the reliability of the whole structure can be improved. Because tantalum nitride and tantalum silicon nitride have better barrier property to tungsten diffusion and contact resistance with tungsten is lower, the metal tungsten diffusion can be prevented. And the tantalum nitride has a lower resistance temperature coefficient, the resistance change caused by the tantalum nitride along with the temperature change is smaller, in addition, the deposition of the metal tungsten on the tantalum nitride is not influenced by the surface roughness of the tantalum nitride, and the thickness consistency of the metal tungsten is better.
In a second specific implementation of an embodiment of the present invention, the material of which the first barrier layer 102 may be provided is selected from: titanium nitride and titanium silicon nitride; the buffer layer 103 is made of titanium; the material of the second barrier layer 104 is selected from: titanium nitride and titanium silicon nitride.
In an embodiment of the present invention, the material of the first barrier layer 102 is selected from: titanium nitride and titanium silicon nitride; the buffer layer is made of titanium; the material of the second barrier layer 104 is selected from: titanium nitride and titanium silicon nitride. Titanium nitride and titanium silicon nitride have better barrier property to copper diffusion and tungsten diffusion, and the resistance of titanium nitride is smaller, for example, the resistance of titanium nitride is smaller than that of tantalum nitride under the condition of the same thickness, so that the electrical property of the device is improved. Compared with the prior art that the single-layer titanium nitride is adopted to block copper diffusion and tungsten diffusion, and the problems of falling, breaking and the like (for example, the single-layer titanium nitride is likely to occur when the thickness exceeds 300A) can be caused by stress, by adopting the scheme of the embodiment of the invention, the buffer layer 103 is added between the titanium nitrides, the effects of balancing the stress of the upper layer material and the lower layer material and absorbing the stress can be achieved, and the stability and the reliability of the whole structure can be improved.
In a third specific implementation of an embodiment of the present invention, the material of which the first barrier layer 102 may be provided is selected from: tungsten nitride; the buffer layer 103 is made of titanium and/or tantalum; the material of the second barrier layer 104 is selected from: tungsten nitride.
In an embodiment of the present invention, the material of the first barrier layer 102 is selected from: tungsten nitride; the buffer layer is made of titanium and/or tantalum; the material of the second barrier layer 104 is selected from: tungsten nitride. Tungsten nitride has better barrier property to copper diffusion and tungsten diffusion, the barrier capability of the copper-tungsten electrical connection structure is even larger than that of tantalum nitride and titanium nitride when the thickness of the copper-tungsten electrical connection structure is smaller, when the size of a through hole for filling the plug structure is smaller (for example, smaller than 600nm), the actual size of the through hole can be obviously reduced due to the arrangement of the barrier layer and the buffer layer 103, the resistance value of the through hole is influenced, and at the moment, the tungsten nitride thin layer is formed by adopting an atomic layer deposition process, so that the size and the barrier requirement of the through hole can be favorably met (for example, the tungsten nitride thin layer with the thickness of 40-100A can meet the requirement of a semiconductor device). And the buffer layer 103 is added between the tungsten nitrides, so that the effects of balancing the stress of the upper layer material and the lower layer material and absorbing the stress can be achieved, and the stability and the reliability of the whole structure can be improved.
Further, before forming the first barrier layer on the surface of the copper layer, the method for forming the copper-tungsten electrical connection structure may further include: and cleaning the surface of the copper layer by adopting a reactive plasma cleaning process.
Further, the process parameters of the reactive plasma cleaning process may be selected from one or more of: the process temperature is 30-200 ℃; the air pressure in the process chamber is 20-60 mTorr; the control power is 400-1200W; the gases in the process chamber include argon, helium, and a hydrogen-containing gas.
Specifically, a large amount of inert gas (e.g., including argon or helium) may be introduced into the reaction chamber to raise the temperature of the wafer surface to about 30-200 ℃, and then a mixed gas of the inert gas (e.g., including argon or helium) and a hydrogen-containing gas is continuously introduced, the chamber pressure is maintained at about 20-60mTorr, and the control power is about 400-.
In the embodiment of the invention, the reactive plasma cleaning process can be used for cleaning (Clean) the surface of the copper layer, removing metal oxide, reducing contact resistance, increasing density of an insulating film and providing a good contact surface for the buffer layer and the second barrier layer.
In the embodiment of the invention, the first barrier layer 102, the buffer layer 103 and the second barrier layer 104 are sequentially arranged to serve as an electrical connection structure between copper and tungsten, so that metal diffusion can be prevented by using the first barrier layer 102 and the second barrier layer 104, and a good contact surface is provided for the first barrier layer 102 and the second barrier layer 104 by using the buffer layer, so that the stability and reliability of the whole structure are improved, and various requirements of preventing metal diffusion, improving the stability of a device, reducing the production cost and the like are met.
In another copper-tungsten electrical connection structure according to an embodiment of the present invention, the copper-tungsten electrical connection structure may be used to form a plug structure.
Referring to fig. 3 to 5, fig. 3 to 5 are schematic cross-sectional views of devices corresponding to steps in a method for forming a copper-tungsten electrical connection structure according to an embodiment of the present invention.
Referring to fig. 3, a semiconductor substrate 200 is provided, and a crystal plane dielectric layer 212, a copper layer 220 and a crystal back dielectric layer 211 are formed, wherein the crystal plane dielectric layer 212 is located on a first surface of the semiconductor substrate 200, and the crystal back dielectric layer 211 is located on a second surface of the semiconductor substrate 200. The surface of the back side dielectric layer 211 may be bonded to a Carrier Wafer (Carrier Wafer) 201.
Specifically, the semiconductor substrate 200 may be a silicon substrate, or the material of the semiconductor substrate 200 may also be a material suitably applied to an image sensor, such as germanium, silicon carbide, gallium arsenide, or indium gallium arsenide, and the semiconductor substrate 200 may also be a silicon substrate on the surface of an insulator or a germanium substrate on the surface of an insulator, or a substrate on which an epitaxial layer (Epi layer) is grown. And forming a through hole penetrating through the crystal plane dielectric layer 212, the semiconductor substrate 200 and a part of the crystal back dielectric layer 211, wherein the bottom surface of the through hole is exposed out of the surface of the copper layer 220.
Further, before forming a through hole penetrating through the crystal plane dielectric layer 212, the semiconductor substrate 200 and a portion of the back crystal dielectric layer 211, the method may further include: providing a Carrier Wafer (Carrier Wafer), bonding the front surface of the Carrier Wafer with the front surface (including the back crystal dielectric layer 211 and the copper layer 220) of the semiconductor substrate 200, then overturning the bonded device, and performing thinning treatment from the back surface of the semiconductor substrate 200.
It is noted that the step of forming the via hole through the crystalline plane dielectric layer 212, the semiconductor substrate 200 and a portion of the back crystal dielectric layer 211 is also performed from the back side of the semiconductor substrate 200. A crystalline plane dielectric layer 212 is shown in figure 3 on the back side of the semiconductor substrate 200.
It is understood that, in a specific implementation manner of the embodiment of the present invention, the formation of the crystalline plane dielectric layer 212, the copper layer 220 and the back crystal dielectric layer 211 may be performed by first forming the back crystal dielectric layer 211, then forming the copper layer 220 in the back crystal dielectric layer 211, then bonding the carrier and the semiconductor substrate 200, and turning over to form the crystalline plane dielectric layer 212. However, in the embodiment of the present invention, the crystallographic plane dielectric layer 212, the copper layer 220, and the back-side dielectric layer 211 may be formed by other process sequences, and the specific process parameters are not limited.
Forming a through hole penetrating through the crystal plane dielectric layer 212, the semiconductor substrate 200 and a part of the crystal back dielectric layer 211, wherein the step of forming a sidewall dielectric layer 230 on the inner sidewall surface of the through hole may include: forming an initial through hole (not shown) penetrating through the crystal plane dielectric layer 212, the semiconductor substrate 200 and a part of the back crystal dielectric layer 211 by using an etching process, wherein a preset distance is formed between the bottom surface of the initial through hole and the surface of the copper layer 220; forming a protective dielectric layer (not shown) on the back surface of the semiconductor substrate 200 and the bottom and sidewall surfaces of the initial through hole, wherein the protective dielectric layer is used for protecting the sidewall surface of the initial through hole; and etching the initial through hole to obtain the through hole.
The bottom surface of the through hole is exposed out of the surface of the copper layer 220, and the remaining protective dielectric layer after etching is a sidewall dielectric layer 230 formed on the surface of the inner sidewall of the through hole. The material of the crystal plane dielectric layer 212 and the crystal back dielectric layer 211 may be selected from silicon oxide and silicon nitride, and the crystal plane dielectric layer 212 and the crystal back dielectric layer 211 may also be a stacked layer of silicon oxide and silicon nitride to reduce the stress of the device.
In the embodiment of the present invention, a through hole penetrating through the crystal plane dielectric layer 212, the semiconductor substrate 200 and a part of the crystal back dielectric layer 211 may be formed, the bottom surface of the through hole exposes the surface of the copper layer 220, a sidewall dielectric layer 230 is formed on the surface of the inner sidewall of the through hole, and the first blocking layer 240 is formed on the surface of the sidewall dielectric layer 230 in addition to the surface of the copper layer 220, so that the copper-tungsten electrical connection structure forms a plug structure filled in the silicon through hole, thereby improving the electrical performance of the plug structure.
Referring to fig. 4, a sidewall dielectric layer 230 is formed on the inner sidewall surface of the via, a first barrier layer 240 is formed on the surface of the sidewall dielectric layer 230, a buffer layer 250 is formed on the surface of the first barrier layer 240, and a second barrier layer 260 is formed on the surface of the buffer layer 250.
It is understood that the first barrier layer 240 is formed not only on the surface of the sidewall dielectric layer 230, but also on the surface of the copper layer 220.
In the copper-tungsten electrical connection structure shown in fig. 3 to 5, the first barrier layer 240, the buffer layer 250, and the second barrier layer 260 are used to form a plug structure, one end of which is connected to the surface of the copper layer 220, and the other end of which is connected to the surface of the tungsten layer 270.
The plug structure may further include a sidewall dielectric layer 230, and the first barrier layer 240 is further formed on an inner sidewall surface of the plug structure, that is, on a surface of the sidewall dielectric layer 230.
Further, the process of forming the second barrier layer 260 on the surface of the buffer layer 250 may be selected from: when the depth-to-width ratio of the through hole for filling the plug structure is smaller than a preset threshold value, forming the second barrier layer by adopting a physical vapor deposition process; and when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold value, forming the second barrier layer by adopting a chemical vapor deposition process or an atomic layer deposition process.
In the embodiment of the present invention, the process for forming the second barrier layer 260 on the surface of the buffer layer is selected from: when the aspect ratio of the through hole for filling the plug structure is smaller than a preset threshold (for example, the aspect ratio of the filling hole is smaller than 1:3), a physical vapor deposition process can be adopted to form the second barrier layer, and the second barrier layer is preferentially selected to be physical vapor deposition, so that the whole process flow is simpler, the whole process of tantalum nitride, tantalum and tantalum nitride can be completed in one reaction chamber, and the problems of contact resistance increase, reliability and the like caused by vacuum breaking of some metal surface oxidation zones can be avoided.
In one specific application of the embodiments of the present invention, the film thickness of the second barrier layer 260 in this case may be greater than 100A-300A.
In the embodiment of the invention, when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold (for example, the aspect ratio of the filling hole is greater than or equal to 1:3), the second barrier layer is formed by using a chemical vapor deposition process or an atomic layer deposition process, and the two methods have better step coverage. The atomic layer deposition can deposit thinner thickness and can effectively reduce the contact resistance
In one specific application of the embodiments of the present invention, the thickness of the second barrier layer 260 in this case may be 10A-150A.
For more details of the first barrier layer 240, the buffer layer 250 and the second barrier layer 260, please refer to the foregoing description and the related descriptions in fig. 1 to fig. 2, which are not repeated herein.
Referring to fig. 5, a tungsten layer 270 is formed on a surface of the second barrier layer 260 to prevent diffusion of tungsten metal by the second barrier layer 260.
In an embodiment of the present invention, a copper-tungsten electrical connection structure is further disclosed, and referring to fig. 5, the copper-tungsten electrical connection structure may include: a first barrier layer 240 on the surface of the copper layer 220; a buffer layer 250 on a surface of the first barrier layer 240; a second barrier layer 240 on a surface of the buffer layer 250; wherein the tungsten layer 270 is formed on the surface of the second barrier layer 240.
Further, one or more of the following may be satisfied: the material of the first barrier layer 240 is selected from: tantalum nitride and tantalum silicon nitride; the buffer layer 250 is made of tantalum; the material of the second barrier layer 260 is selected from: tantalum nitride and tantalum silicon nitride.
Further, one or more of the following may be satisfied: the material of the first barrier layer 240 is selected from: titanium nitride and titanium silicon nitride; the buffer layer 250 is made of titanium; the material of the second barrier layer 260 is selected from: titanium nitride and titanium silicon nitride.
Further, one or more of the following may be satisfied: the material of the first barrier layer 240 is selected from: tungsten nitride; the buffer layer 250 is made of titanium and/or tantalum; the material of the second barrier layer 260 is selected from: tungsten nitride.
Further, the copper-tungsten electrical connection structure is used to form a plug structure, and one end of the plug structure is connected to the surface of the copper layer 220; wherein the first barrier layer 240 is located on the inner sidewall surface of the plug structure.
Further, the formation process of the second barrier layer 260 is selected from: when the aspect ratio of the via hole for filling the plug structure is smaller than a preset threshold, the forming process of the second barrier layer 260 is a physical vapor deposition process; when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold, the forming process of the second barrier layer 260 is a chemical vapor deposition process or an atomic layer deposition process.
Further, the copper-tungsten electrical connection structure further comprises: a semiconductor substrate 200; a crystal plane dielectric layer 212, a copper layer 220 and a crystal back dielectric layer 211, wherein the crystal plane dielectric layer 212 is located on the first surface of the semiconductor substrate 200, and the crystal back dielectric layer 211 is located on the second surface of the semiconductor substrate 200; a through hole penetrating through the crystal plane dielectric layer 212, the semiconductor substrate and a part of the crystal back dielectric layer 211, wherein the bottom surface of the through hole is exposed out of the surface of the copper layer 220; a sidewall dielectric layer 230 on the inner sidewall surface of the via; the first barrier layer 240 is further formed on the surface of the sidewall dielectric layer 230.
In the embodiment of the present invention, by sequentially disposing the first barrier layer 240, the buffer layer 250, and the second barrier layer 260 as an electrical connection structure between copper and tungsten, metal diffusion can be prevented by using the first barrier layer 240 and the second barrier layer 260, and a good contact surface is provided for the first barrier layer 240 and the second barrier layer 260 by using the buffer layer, so that stability and reliability of the entire structure are improved, and various requirements of preventing metal diffusion, improving stability of a device, reducing production cost, and the like are met.
For the principle, specific implementation and beneficial effects of the copper-tungsten electrical connection structure, please refer to the related description of the formation method of the copper-tungsten electrical connection structure, which is not repeated herein.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (13)

1. A method for forming a copper-tungsten electrical connection structure is characterized by comprising the following steps:
forming a first barrier layer on the surface of the copper layer;
forming a buffer layer on the surface of the first barrier layer;
forming a second barrier layer on the surface of the buffer layer;
and the tungsten layer is formed on the surface of the second barrier layer.
2. The method of forming a copper-tungsten electrical connection structure according to claim 1, wherein one or more of the following is satisfied:
the material of the first barrier layer is selected from: tantalum nitride and tantalum silicon nitride;
the buffer layer is made of tantalum;
the material of the second barrier layer is selected from: tantalum nitride and tantalum silicon nitride.
3. The method of forming a copper-tungsten electrical connection structure according to claim 1, wherein one or more of the following is satisfied:
the material of the first barrier layer is selected from: titanium nitride and titanium silicon nitride;
the buffer layer is made of titanium;
the material of the second barrier layer is selected from: titanium nitride and titanium silicon nitride.
4. The method of forming a copper-tungsten electrical connection structure according to claim 1, wherein one or more of the following is satisfied:
the material of the first barrier layer is selected from: tungsten nitride;
the buffer layer is made of titanium and/or tantalum;
the material of the second barrier layer is selected from: tungsten nitride.
5. The method as claimed in claim 1, further comprising, before forming the first barrier layer on the surface of the copper layer:
and cleaning the surface of the copper layer by adopting a reactive plasma cleaning process.
6. The method as claimed in claim 5, wherein the process parameters of the reactive plasma cleaning process are selected from one or more of the following:
the process temperature is 30-200 ℃;
the air pressure in the process chamber is 20-60 mTorr;
the control power is 400-1200W;
the gas in the process chamber comprises argon, helium and a hydrogen-containing gas.
7. The method as claimed in claim 1, wherein the copper-tungsten electrical connection structure is used to form a plug structure, one end of the plug structure is connected to the surface of the copper layer;
wherein the first barrier layer is further formed on an inner sidewall surface of the plug structure.
8. The method as claimed in claim 7, wherein the process of forming the second barrier layer on the surface of the buffer layer is selected from:
when the depth-to-width ratio of the through hole for filling the plug structure is smaller than a preset threshold value, forming the second barrier layer by adopting a physical vapor deposition process;
and when the aspect ratio of the through hole for filling the plug structure is greater than or equal to the preset threshold value, forming the second barrier layer by adopting a chemical vapor deposition process or an atomic layer deposition process.
9. The method of claim 1, wherein prior to forming the first barrier layer on the surface of the copper layer, the method further comprises:
providing a semiconductor substrate;
forming a crystal face dielectric layer, a copper layer and a crystal back dielectric layer, wherein the crystal face dielectric layer is positioned on the first surface of the semiconductor substrate, and the crystal back dielectric layer is positioned on the second surface of the semiconductor substrate;
forming a through hole penetrating through the crystal face dielectric layer, the semiconductor substrate and a part of the crystal back dielectric layer, wherein the bottom surface of the through hole is exposed out of the surface of the copper layer;
forming a side wall dielectric layer on the surface of the inner side wall of the through hole;
and the first barrier layer is also formed on the surface of the side wall dielectric layer.
10. A copper-tungsten electrical connection structure, comprising:
the first barrier layer is positioned on the surface of the copper layer;
the buffer layer is positioned on the surface of the first barrier layer;
the second barrier layer is positioned on the surface of the buffer layer;
and the tungsten layer is formed on the surface of the second barrier layer.
11. The copper-tungsten electrical connection structure of claim 10, wherein one or more of the following is satisfied:
the material of the first barrier layer is selected from: tantalum nitride and tantalum silicon nitride;
the buffer layer is made of tantalum;
the material of the second barrier layer is selected from: tantalum nitride and tantalum silicon nitride.
12. The copper-tungsten electrical connection structure of claim 10, wherein one or more of the following is satisfied:
the material of the first barrier layer is selected from: titanium nitride and titanium silicon nitride;
the buffer layer is made of titanium;
the material of the second barrier layer is selected from: titanium nitride and titanium silicon nitride.
13. The copper-tungsten electrical connection structure of claim 10, wherein one or more of the following is satisfied:
the material of the first barrier layer is selected from: tungsten nitride;
the buffer layer is made of titanium and/or tantalum;
the material of the second barrier layer is selected from: tungsten nitride.
CN202011501441.1A 2020-12-17 2020-12-17 Copper-tungsten electrical connection structure and forming method thereof Pending CN114649293A (en)

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