CN113745095A - Method for cleaning metal oxide on bonding surface - Google Patents

Method for cleaning metal oxide on bonding surface Download PDF

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Publication number
CN113745095A
CN113745095A CN202111033900.2A CN202111033900A CN113745095A CN 113745095 A CN113745095 A CN 113745095A CN 202111033900 A CN202111033900 A CN 202111033900A CN 113745095 A CN113745095 A CN 113745095A
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silicon
oxygen
plasma
bonded
bonding
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刘天建
胡海威
田应超
曹瑞霞
李琳瑜
石林
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Hubei 3d Semiconductor Integrated Innovation Center Co ltd
Hubei Jiangcheng Laboratory
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Hubei 3d Semiconductor Integrated Innovation Center Co ltd
Hubei Jiangcheng Laboratory
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Priority to CN202111033900.2A priority Critical patent/CN113745095A/en
Publication of CN113745095A publication Critical patent/CN113745095A/en
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    • 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
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02041—Cleaning
    • H01L21/02057—Cleaning during device manufacture
    • H01L21/02068—Cleaning during device manufacture during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
    • 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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/02—Bonding areas ; Manufacturing methods related thereto
    • H01L24/03—Manufacturing methods
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/02—Bonding areas; Manufacturing methods related thereto
    • H01L2224/03—Manufacturing methods
    • H01L2224/038—Post-treatment of the bonding area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/02—Bonding areas; Manufacturing methods related thereto
    • H01L2224/03—Manufacturing methods
    • H01L2224/038—Post-treatment of the bonding area
    • H01L2224/0381—Cleaning, e.g. oxide removal step, desmearing

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  • Chemical & Material Sciences (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Physics & Mathematics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)
  • Cleaning Or Drying Semiconductors (AREA)

Abstract

The invention provides a method for cleaning metal oxide on a bonding surface, which is characterized in that an activation process is performed in a plasma activation chamber, and a reduction process is also performed at the same time, so that an additional plasma reaction chamber and process steps are not added, and equipment and cost required by the process are not increased; exciting mixed gas of hydrogen and nitrogen in the plasma activation chamber to be plasma, reducing the copper oxide thin layer through plasma bombardment to reduce the copper oxide to copper, so that the copper oxide thin layer on the surface of the bonded copper pad is reduced to the copper thin layer, thereby avoiding the influence of the copper oxide thin layer on the electrical connection after mixed bonding and improving the yield of products; the surface of the silicon-oxygen-containing insulating layer can be activated by combining the wafer with the water in the air when the wafer with the bonding interface preliminarily activated is taken out from the plasma activation chamber, so that the silicon-oxygen-containing insulating layer is bonded more easily during hybrid bonding, and the bonding strength of the silicon-oxygen-containing insulating layer is increased.

Description

Method for cleaning metal oxide on bonding surface
Technical Field
The invention relates to the technical field of semiconductors, in particular to a method for cleaning metal oxide on a bonding surface.
Background
With the semiconductor technology entering the post-molarity, chip structures are developing towards three dimensions in order to meet the requirements of high integration and high performance. The hybrid bonding technology can interconnect chips of different process node processes at high density, and realize system-level integration with smaller size, higher performance and lower power consumption. The existing hybrid bonding methods generally include wafer-to-wafer bonding (W2W), chip-to-chip bonding (C2C), and chip-to-wafer bonding (C2W), and these bonds generally adopt Cu — Cu hybrid bonding. The bump-free (bump) bonding process is mainly characterized in that the hybrid bonding technology is utilized to realize bonding between Cu and Cu, so that the size of a connecting unit can be greatly reduced, the minimum size can be smaller than 10 micrometers, higher I/O (input/output) connecting density is realized, and meanwhile, no lower filler is used, so that the heat dissipation performance of the connecting unit is good.
Cu on the bonding surface of the wafer and the chip is easily oxidized, and the generated CuO compound affects the electrical connection between the wafer and the chip and the bonding strength, thereby affecting the bonding yield.
Disclosure of Invention
The invention aims to provide a method for cleaning metal oxide on a mixed bonding surface, which can adjust a conventional plasma activation process, so that plasma activation of a mixed bonding interface and plasma cleaning of CuO are synchronously performed, the plasma activation ensures enough bonding strength, and the plasma cleaning provides enough electrical connection, thereby improving the bonding yield.
In order to solve the above problems, the present invention provides a method for cleaning a bonding surface metal oxide, comprising the steps of:
providing a structure to be bonded, wherein the structure to be bonded comprises a substrate and a mixed bonding structure formed on the substrate, the mixed bonding structure comprises a bonding copper pad and a silicon-oxygen-containing insulating layer, the silicon-oxygen-containing insulating layer is exposed out of the bonding copper pad, and a copper oxide thin layer is formed on the surface of the bonding copper pad;
placing the structure to be bonded on a carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to form plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the silicon-oxygen-containing insulating layer to complete preliminary activation of a mixed bonding interface of the structure to be bonded; and
and moving the structure to be bonded out of the plasma activation chamber, wherein silicon on the surface of the silicon-oxygen-containing insulating layer after silicon-oxygen bond breaking is combined with water molecules in the air to generate-SiOH groups so as to activate the surface of the silicon-oxygen-containing insulating layer.
Optionally, the proportion of the hydrogen gas in the mixed gas is less than 5%.
Further, the step of placing the structure to be bonded on a carrier of a plasma activation chamber, introducing a mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to form a plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the silicon-oxygen-containing insulating layer to complete preliminary activation of a mixed bonding interface of the structure to be bonded includes:
and placing the structure to be bonded on a carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, exciting the hydrogen into plasma of the hydrogen through the plasma activation chamber, exciting the nitrogen into plasma of the nitrogen through the plasma activation chamber, reducing the copper oxide thin layer through plasma bombardment of the hydrogen to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the silicon and oxygen-containing insulating layer through the plasma of the nitrogen to finish primary activation of a mixed bonding interface of the structure to be bonded.
Further, the hybrid bonding structure is a wafer, and the cleaning method includes the following steps:
providing a wafer to be bonded, wherein the wafer to be bonded comprises a first substrate and a first mixed bonding structure formed on the first substrate, the first mixed bonding structure comprises a first bonding copper pad and a first silicon-oxygen-containing insulating layer, the first silicon-oxygen-containing insulating layer is exposed out of the first bonding copper pad, and a copper oxide thin layer is formed on the surface of the first bonding copper pad;
placing the wafer to be bonded on a wafer carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to form plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the first silicon-oxygen containing insulating layer to finish primary activation of a mixed bonding interface of the wafer to be bonded;
and moving the wafer to be bonded out of the plasma activation chamber, wherein silicon of the silicon-oxygen containing insulating layer surface is subjected to silicon-oxygen bond breaking and is combined with water molecules in the air to generate-SiOH groups so as to activate the first silicon-oxygen containing insulating layer surface.
Further, the step of placing the wafer to be bonded on a wafer carrying platform of a plasma activation chamber, introducing a mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to become a plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the first silicon-oxygen-containing insulating layer to complete preliminary activation of a mixed bonding interface of the wafer to be bonded comprises the following steps:
placing the wafer to be bonded on a wafer carrying platform of a plasma activation chamber, and extracting gas in the plasma activation chamber;
introducing mixed gas of hydrogen and nitrogen, and exciting the mixed gas into plasma through the plasma activation chamber; and
and reducing the copper oxide thin layer by plasma bombardment so as to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the first silicon and oxygen containing insulating layer.
Further, the first substrate is a wafer-level substrate.
Further, the hybrid bonding structure is a chip, and the cleaning method includes the following steps:
providing a plurality of chips to be bonded, wherein the chips to be bonded comprise a second substrate and a second mixed bonding structure formed on the second substrate, the second mixed bonding structure comprises a second bonding copper pad and a second silicon-oxygen-containing insulating layer surrounding the second bonding copper pad, the second silicon-oxygen-containing insulating layer exposes out of the second bonding copper pad, and a copper oxide thin layer is formed on the surface of the second bonding copper pad;
uniformly placing a plurality of chips to be bonded on a chip carrying disc, then placing the chips into a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited into plasma by the plasma activation chamber, reducing the copper oxide thin layer by plasma bombardment so as to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the second silicon and oxygen-containing insulating layer so as to complete preliminary activation of a mixed bonding interface of the chips to be bonded;
and moving the chips to be bonded out of the plasma activation chamber, wherein silicon subjected to silicon-oxygen bond breaking on the surface of the second silicon-oxygen containing insulating layer is combined with water molecules in air to generate-SiOH groups so as to activate the surface of the second silicon-oxygen containing insulating layer.
Further, uniformly placing a plurality of chips to be bonded on a chip carrying disc, placing the chips into a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited into plasma by the plasma activation chamber, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the second silicon and oxygen-containing insulating layer to complete preliminary activation of a mixed bonding interface of the chips to be bonded, wherein the step of reducing the copper oxide thin layer into copper by plasma bombardment comprises the following steps:
uniformly placing a plurality of chips to be bonded on a chip carrying disc, then placing the chips into a plasma activation cavity, and extracting gas in the plasma activation cavity;
introducing mixed gas of hydrogen and nitrogen, and exciting the mixed gas into plasma through the plasma activation chamber; and
and reducing the copper oxide thin layer by plasma bombardment so as to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the second silicon and oxygen containing insulating layer.
Further, the second substrate is a chip-scale substrate.
Optionally, the silicon-oxygen containing insulating layer is a silicon dioxide insulating layer.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a cleaning method of a bonding surface metal oxide, which comprises the following steps: providing a structure to be bonded, wherein the structure to be bonded comprises a substrate and a mixed bonding structure formed on the substrate, the mixed bonding structure comprises a bonding copper pad and a silicon-oxygen-containing insulating layer, the silicon-oxygen-containing insulating layer is exposed out of the bonding copper pad, and a copper oxide thin layer is formed on the surface of the bonding copper pad; placing the structure to be bonded on a carrying table of a plasma activation chamber, introducing plasma of mixed gas of hydrogen and nitrogen, reducing the copper oxide thin layer through plasma bombardment so as to reduce the copper oxide into copper, and breaking a silicon-oxygen bond on the surface of the silicon-oxygen-containing insulating layer so as to complete preliminary activation of a mixed bonding interface of the structure to be bonded; and moving the structure to be bonded out of the plasma activation chamber, wherein silicon on the surface of the silicon-oxygen-containing insulating layer after silicon-oxygen bond breaking is combined with water molecules in air to generate-SiOH groups so as to activate the surface of the silicon-oxygen-containing insulating layer. According to the invention, the reduction process is carried out in the plasma activation chamber, so that the reduction process of the metal oxide is carried out while the mixed bonding interface is activated, the working procedures are not increased, and the cost is saved; the copper oxide thin layer is reduced to copper through plasma bombardment, so that the copper oxide thin layer on the surface of the bonding copper pad is reduced to the copper thin layer, the flatness of the bonding copper pad is improved, bubbles generated during bonding are reduced, the influence of the copper oxide thin layer on the electric connection after mixed bonding is reduced, the bonding strength of the bonding copper pad is improved, and the yield of products is improved; the surface of the silicon-oxygen-containing insulating layer is activated by taking the bonding structure out of the plasma activation chamber and water in the air, so that the silicon-oxygen-containing insulating layer is bonded more easily during hybrid bonding, and the bonding strength of the silicon-oxygen-containing insulating layer is increased.
In addition, the proportion of the hydrogen in the mixed gas is less than 5%, so that the invention does not use pure hydrogen for reduction, but uses the mixed gas of nitrogen and hydrogen, thereby preventing explosion and being safer.
Drawings
FIG. 1 is a schematic structural view of a bonding surface during a reductive ion bombardment process according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a bonding surface activation process on a silicon-oxygen-containing insulating layer according to an embodiment of the present invention.
Description of reference numerals:
11-a first silicon-oxygen containing insulating layer; 12-a first bonded copper pad; 13-thin layer of copper oxide.
Detailed Description
A method for cleaning a bonding surface of a metal oxide according to the present invention will be described in further detail below. The present invention will now be described in more detail with reference to the accompanying drawings, in which preferred embodiments of the invention are shown, it being understood that one skilled in the art may modify the invention herein described while still achieving the advantageous effects of the invention. Accordingly, the following description should be construed as broadly as possible to those skilled in the art and not as limiting the invention.
In the interest of clarity, not all features of an actual implementation are described. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific details must be set forth in order to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art.
In order to make the objects and features of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise ratio for the purpose of facilitating and distinctly aiding in the description of the embodiments of the invention.
The core of the invention is to provide a method for cleaning metal oxide on a bonding surface, which comprises the following steps:
providing a structure to be bonded, wherein the structure to be bonded comprises a substrate and a mixed bonding structure formed on the substrate, the mixed bonding structure comprises a bonding copper pad and a silicon-oxygen-containing insulating layer, the silicon-oxygen-containing insulating layer is exposed out of the bonding copper pad, and a copper oxide thin layer is formed on the surface of the bonding copper pad;
placing the structure to be bonded on a carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to form plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the silicon-oxygen-containing insulating layer to complete preliminary activation of a mixed bonding interface of the structure to be bonded; and
and moving the structure to be bonded out of the plasma activation chamber, wherein silicon on the surface of the silicon-oxygen-containing insulating layer after silicon-oxygen bond breaking is combined with water molecules in the air to generate-SiOH groups so as to activate the surface of the silicon-oxygen-containing insulating layer.
Example one
The embodiment provides a method for cleaning metal oxide on a bonding surface of a wafer, which comprises the following steps:
step S11: providing a wafer to be bonded, wherein the wafer to be bonded comprises a first substrate and a first mixed bonding structure formed on the first substrate, the first mixed bonding structure comprises a first bonding copper pad and a first silicon-oxygen-containing insulating layer, the first silicon-oxygen-containing insulating layer is exposed out of the first bonding copper pad, and a copper oxide thin layer is formed on the surface of the first bonding copper pad;
step S12: placing the wafer to be bonded on a wafer carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to form plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the first silicon-oxygen containing insulating layer to finish primary activation of a mixed bonding interface of the wafer to be bonded;
step S13: and placing the structure to be bonded on a carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, exciting the hydrogen into plasma of the hydrogen through the plasma activation chamber, exciting the nitrogen into plasma of the nitrogen through the plasma activation chamber, reducing the copper oxide thin layer through plasma bombardment of the hydrogen to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the silicon and oxygen-containing insulating layer through the plasma of the nitrogen to finish primary activation of a mixed bonding interface of the structure to be bonded.
The method for cleaning the metal oxide on the bonding surface of the wafer according to this embodiment will be described in detail below.
Step S11 is first executed: providing a wafer to be bonded, wherein the wafer to be bonded comprises a first substrate and a first mixed bonding structure formed on the first substrate, the first mixed bonding structure comprises a first bonding copper pad 12 and a first silicon-oxygen-containing insulating layer 11, the first silicon-oxygen-containing insulating layer 11 is exposed out of the first bonding copper pad 12, and a copper oxide thin layer 13 is formed on the surface of the first bonding copper pad 12.
The first substrate is a wafer-level substrate, the hybrid bonding structure comprises a first interconnection structure layer, a first silicon-oxygen-containing insulating layer 11 and a first bonding copper pad 12, the first interconnection structure layer can be one or more metal layers, and interconnection among different metal layers can be realized through electric connecting pieces such as contact plugs, connecting lines and/or via holes. The first interconnection structure layer comprises a first dielectric layer and a first metal interconnection structure, the first metal interconnection structure is embedded in the first dielectric layer, the first metal interconnection structure is electrically connected with a first bonding copper pad 12, and the first bonding copper pad 12 is embedded on the surface of the first silicon-oxygen-containing insulating layer 11, so that the first silicon-oxygen-containing insulating layer 11 is exposed out of the first bonding copper pad 12.
In this embodiment, the first silicon-oxygen-containing insulating layer 11 is, for example, a silicon dioxide insulating layer.
The first bonding copper pad 12 of the wafer to be bonded is easily oxidized before bonding to generate a thin copper oxide layer, and the thin copper oxide layer 13 has a large influence on the flatness of the hybrid bonding process and also on the electrical connection after hybrid bonding.
In order to solve the above problem, step S12 is executed to place the wafer to be bonded on the wafer carrying stage of the plasma activation chamber, and introduce a mixed gas of hydrogen and nitrogen, where after the mixed gas is excited by the plasma activation chamber to become a plasma, the copper oxide thin layer 13 is reduced by plasma bombardment to reduce the copper oxide to copper, and the silicon-oxygen bond on the surface of the first silicon-oxygen containing insulating layer 11 is broken to complete the preliminary activation of the mixed bonding interface of the wafer to be bonded. The step is carried out in the plasma activation chamber, no additional plasma reaction chamber and special copper oxide reduction process are added, no working procedure is added, and therefore the process cost is not increased.
In detail, firstly, the wafer to be bonded is placed on a wafer carrying platform of a plasma activation chamber, and gas in the plasma activation chamber is pumped out.
Next, as shown in fig. 1, a mixed gas of hydrogen and nitrogen is introduced, and the mixed gas is excited into plasma, i.e., hydrogen atoms (H), hydrogen ions (H +), nitrogen atoms (N), and nitrogen ions (N +), by the plasma activation chamber. Wherein the reducing plasma comprises hydrogen atoms (H) and hydrogen ions (H +), and the proportion of hydrogen gas in the mixed gas is less than 5%. The reducing plasma reacts with oxygen in the copper oxide to produce water (H)2O) and reducing the copper oxide to copper. The process step enables the copper oxide thin layer 13 on the surface of the first bonding copper pad 12 to be reduced into a copper thin layer, so that the flatness of the first bonding copper pad 12 is improved, the influence of the copper oxide thin layer 13 on the electrical connection after mixed bonding is reduced, the influence of the copper oxide thin layer 13 on the diffusion effect during Cu-Cu bonding in the mixed bonding process is eliminated, the bonding strength of the first bonding copper pad 12 is improved, and the yield of products is improved. In the process of the reduction reaction, a silicon-oxygen bond on the surface of the first silicon-oxygen containing insulating layer 11 is broken, so that a silicon-oxygen containing compound loses one electron, that is, silicon-oxygen containing positive charges, and the silicon-oxygen broken bond of the first silicon-oxygen containing insulating layer is realized, thereby being beneficial to realizing the activation of the first silicon-oxygen containing insulating layer.
In this embodiment, H and H2O and H + and H2Elaetrom ratio H of O2And H2The Elaeherm line of O is lower and is far lower than that of most metals and metal oxides, and the Gibbs free energy of the reaction of H and H + absorbing oxygen to form water is extremely low, namely the reaction is easy to occur at a lower temperature and copper oxide is easy to reduce. Therefore, the plasma activation chamber can be performed in a normal temperature environment without providing a high temperature environment, so that the reduction reaction does not need a harsh reaction environment.
As shown in fig. 2, step S13 is executed to move the wafer to be bonded out of the plasma activation chamber, and a-SiOH group is generated by the combination between silicon and water molecules in the air after the silicon-oxygen bond breaking on the surface of the first silicon-oxygen containing insulating layer 11, so as to perform a preliminary activation on the surface of the first silicon-oxygen containing insulating layer 11.
In this step, the wafer to be bonded is moved out of the plasma activation chamber, the wafer to be bonded contacts with the outside air, SiOH is generated by silicon which is subjected to silicon-oxygen bond breaking on the surface of the first silicon-oxygen containing insulating layer and water in the air, that is, an — SiOH group is generated between the silicon and water molecules, so that activation is completed on the surface of the first silicon-oxygen containing insulating layer, the first silicon-oxygen containing insulating layer in the hybrid bonding structure is bonded more easily, and the bonding strength of the first silicon-oxygen containing insulating layer 11 is increased.
Example two
Compared with the first embodiment, the following differences are provided: the embodiment provides a method for cleaning metal oxide on the bonding surface of a chip, which replaces the wafer in the first embodiment with the chip.
The method for cleaning the metal oxide on the bonding surface of the chip comprises the following steps:
step S21: providing a plurality of chips to be bonded, wherein the chips to be bonded comprise a second substrate and a second mixed bonding structure formed on the second substrate, the second mixed bonding structure comprises a second bonding copper pad and a second silicon-oxygen-containing insulating layer surrounding the second bonding copper pad, the second silicon-oxygen-containing insulating layer exposes the second bonding copper pad, a copper oxide thin layer is formed on the surface of the second bonding copper pad, and the second substrate is a chip-level substrate;
step S22: uniformly placing a plurality of chips to be bonded on a chip carrying disc, then placing the chips into a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited into plasma by the plasma activation chamber, reducing the copper oxide thin layer by plasma bombardment so as to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the second silicon and oxygen-containing insulating layer so as to complete preliminary activation of a mixed bonding interface of the chips to be bonded;
step S23: and moving the chips to be bonded out of the plasma activation chamber, wherein silicon subjected to silicon-oxygen bond breaking on the surface of the second silicon-oxygen containing insulating layer is combined with water molecules in air to generate-SiOH groups so as to activate the surface of the second silicon-oxygen containing insulating layer.
In summary, in the method for cleaning metal oxide on the bonding surface provided by the invention, an additional plasma reaction chamber is not required to be added, and simultaneously, the surfaces of the wafer to be bonded and the chip to be bonded are optimized, so that the mixed bonding requirement of the chip and the wafer can be met.
In addition, unless otherwise specified or indicated, the description of the terms "first" and "second" in the specification is only used for distinguishing various components, elements, steps and the like in the specification, and is not used for representing logical relationships or sequential relationships among the various components, elements, steps and the like.
It is to be understood that while the present invention has been described in conjunction with the preferred embodiments thereof, it is not intended to limit the invention to those embodiments. It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims (10)

1. A method of cleaning a bonding surface of a metal oxide, comprising the steps of:
providing a structure to be bonded, wherein the structure to be bonded comprises a substrate and a mixed bonding structure formed on the substrate, the mixed bonding structure comprises a bonding copper pad and a silicon-oxygen-containing insulating layer, the silicon-oxygen-containing insulating layer is exposed out of the bonding copper pad, and a copper oxide thin layer is formed on the surface of the bonding copper pad;
placing the structure to be bonded on a carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to form plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the silicon-oxygen-containing insulating layer to complete preliminary activation of a mixed bonding interface of the structure to be bonded; and
and moving the structure to be bonded out of the plasma activation chamber, wherein silicon on the surface of the silicon-oxygen-containing insulating layer after silicon-oxygen bond breaking is combined with water molecules in the air to generate-SiOH groups so as to activate the surface of the silicon-oxygen-containing insulating layer.
2. The cleaning method according to claim 1, wherein the hydrogen gas accounts for less than 5% of the mixed gas.
3. The cleaning method of claim 1, wherein the step of placing the structure to be bonded on a carrying table of a plasma activation chamber, introducing a mixed gas of hydrogen and nitrogen, after the mixed gas is excited into plasma by the plasma activation chamber, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide into copper, and breaking a silicon oxygen bond on the surface of the silicon oxygen-containing insulating layer to complete the primary activation of the mixed bonding interface of the structure to be bonded comprises the following steps:
and placing the structure to be bonded on a carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, exciting the hydrogen into plasma of the hydrogen through the plasma activation chamber, exciting the nitrogen into plasma of the nitrogen through the plasma activation chamber, reducing the copper oxide thin layer through plasma bombardment of the hydrogen to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the silicon and oxygen-containing insulating layer through the plasma of the nitrogen to finish primary activation of a mixed bonding interface of the structure to be bonded.
4. The cleaning method of claim 2, wherein the hybrid bonded structure is a wafer, the cleaning method comprising the steps of:
providing a wafer to be bonded, wherein the wafer to be bonded comprises a first substrate and a first mixed bonding structure formed on the first substrate, the first mixed bonding structure comprises a first bonding copper pad and a first silicon-oxygen-containing insulating layer, the first silicon-oxygen-containing insulating layer is exposed out of the first bonding copper pad, and a copper oxide thin layer is formed on the surface of the first bonding copper pad;
placing the wafer to be bonded on a wafer carrying platform of a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited by the plasma activation chamber to form plasma, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide to copper, and breaking a silicon-oxygen bond on the surface of the first silicon-oxygen containing insulating layer to finish primary activation of a mixed bonding interface of the wafer to be bonded; and
and moving the wafer to be bonded out of the plasma activation chamber, wherein silicon of the silicon-oxygen containing insulating layer surface is subjected to silicon-oxygen bond breaking and is combined with water molecules in the air to generate-SiOH groups so as to activate the first silicon-oxygen containing insulating layer surface.
5. The cleaning method of claim 4, wherein the step of placing the wafer to be bonded on a wafer carrying table of a plasma activation chamber, introducing a mixed gas of hydrogen and nitrogen, after the mixed gas is excited into plasma by the plasma activation chamber, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide into copper, and breaking silicon oxygen bonds on the surface of the first silicon oxygen-containing insulating layer to complete the preliminary activation of the mixed bonding interface of the wafer to be bonded comprises the following steps:
placing the wafer to be bonded on a wafer carrying platform of a plasma activation chamber, and extracting gas in the plasma activation chamber;
introducing mixed gas of hydrogen and nitrogen, and exciting the mixed gas into plasma through the plasma activation chamber; and
and reducing the copper oxide thin layer by plasma bombardment so as to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the first silicon and oxygen containing insulating layer.
6. The cleaning method of claim 4, wherein the first substrate is a wafer level substrate.
7. The cleaning method of claim 2, wherein the hybrid bond structure is a chip, the cleaning method comprising the steps of:
providing a plurality of chips to be bonded, wherein the chips to be bonded comprise a second substrate and a second mixed bonding structure formed on the second substrate, the second mixed bonding structure comprises a second bonding copper pad and a second silicon-oxygen-containing insulating layer surrounding the second bonding copper pad, the second silicon-oxygen-containing insulating layer exposes out of the second bonding copper pad, and a copper oxide thin layer is formed on the surface of the second bonding copper pad;
uniformly placing a plurality of chips to be bonded on a chip carrying disc, then placing the chips into a plasma activation chamber, introducing mixed gas of hydrogen and nitrogen, after the mixed gas is excited into plasma by the plasma activation chamber, reducing the copper oxide thin layer by plasma bombardment so as to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the second silicon and oxygen-containing insulating layer so as to complete preliminary activation of a mixed bonding interface of the chips to be bonded;
and moving the chips to be bonded out of the plasma activation chamber, wherein silicon subjected to silicon-oxygen bond breaking on the surface of the second silicon-oxygen containing insulating layer is combined with water molecules in air to generate-SiOH groups so as to activate the surface of the second silicon-oxygen containing insulating layer.
8. The cleaning method of claim 7, wherein the step of uniformly placing a plurality of the chips to be bonded on a chip carrier disc, then placing the chips in a plasma activation chamber, introducing a mixed gas of hydrogen and nitrogen, after the mixed gas is excited into plasma by the plasma activation chamber, reducing the copper oxide thin layer by plasma bombardment to reduce the copper oxide into copper, and breaking silicon oxygen bonds on the surface of the second silicon oxygen-containing insulating layer to complete the primary activation of the mixed bonding interface of the chips to be bonded comprises the following steps:
uniformly placing a plurality of chips to be bonded on a chip carrying disc, then placing the chips into a plasma activation cavity, and extracting gas in the plasma activation cavity;
introducing mixed gas of hydrogen and nitrogen, and exciting the mixed gas into plasma through the plasma activation chamber; and
and reducing the copper oxide thin layer by plasma bombardment so as to reduce the copper oxide into copper, and breaking bonds of silicon and oxygen on the surface of the second silicon and oxygen containing insulating layer.
9. The cleaning method of claim 7, wherein the second substrate is a chip-scale substrate.
10. The cleaning method of claim 1, wherein the silicon oxide-containing insulating layer is a silicon dioxide insulating layer.
CN202111033900.2A 2021-09-03 2021-09-03 Method for cleaning metal oxide on bonding surface Pending CN113745095A (en)

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Application publication date: 20211203