# US 11,305,372 B2 · Method of assembly by direct bonding between two elements, each element comprising portions of metal and dielectric materials

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- Number: US 11,305,372 B2
- Document ID: US11305372B2
- Status: Granted
- Kind: B2
- Application number: 14/504,701
- Filed: 2014-10-02
- Published: 2015-04-09
- Granted: 2022-04-19
- Earliest claimed: 2013-10-03
- Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives
- Applicants: Commissariat A L'energie Atomique Et Aux Energies Alternatives
- Inventors: Lea Di Cioccio; Yann Beilliard
- Web page: https://patentgrep.com/patent/US11305372B2

## CPC

- B23K 20/002: {specially adapted for particular articles or work (B23K20/129 takes precedence)}
- B23K 20/24: Preliminary treatment
- B23K 31/02: relating to soldering or welding
- H05K 3/4611: {by laminating two or more circuit boards (H05K3/4652 takes precedence)}
- H10P 10/128: {by direct semiconductor to semiconductor bonding}
- H10W 72/011: {Apparatus therefor}
- H10W 80/00: Direct bonding of chips, wafers or substrates
- H10W 90/00: Package configurations
- B23K 2101/36: Electric or electronic devices
- H10W 72/019: {of bond pads}
- H10W 72/01951: {Changing the shapes of bond pads}
- H10W 72/0198: {batch processes}
- H10W 72/07178: {Means for aligning}
- H10W 72/90: Bond pads, in general
- H10W 72/9226: {with via interconnections}
- H10W 72/923: {Bond pads having multiple stacked layers}
- H10W 72/9415: {relative to the surface, e.g. recessed, protruding}
- H10W 72/952: {comprising metals or metalloids, e.g. PbSn, Ag or Cu}
- H10W 72/953: {not comprising solid metals or solid metalloids, e.g. polymers, ceramics or liquids}
- H10W 72/957: {Multiple bond pads having different materials}
- H10W 72/963: {Providing mechanical bonding or support, e.g. dummy bond pads}
- H10W 72/967: {Multiple bond pads having different functions}
- H10W 80/035: {by heating, e.g. melting or causing diffusion}
- H10W 80/102: {Controlling the environment during the bonding, e.g. the temperature or pressure}
- H10W 80/168: {using guiding structures}
- H10W 80/301: {Bonding techniques, e.g. hybrid bonding}
- H10W 80/312: {characterised by the direct bonding of electrically conductive pads}
- H10W 80/327: {characterised by the direct bonding of insulating parts, e.g. of silicon oxide layers}
- H10W 90/722: {between stacked chips}
- H10W 90/792: {between multiple chips}
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

Method of assembly of a first element (I) and a second element (II) each having an assembly surface, at least one of the assembly surfaces comprising recessed metal portions (6, 106) surrounded by dielectric materials (4, 104) comprising: A) a step to bring the two assembly surfaces into contact without application of pressure such that direct bonding is obtained between the assembly surfaces, said first and second assemblies (I, II) forming a stack with a given thickness (e), B) a heat treatment step of said stack during which the back faces (10, 110) of the first (I) and the second (II) elements are held in position so that they are held at a fixed distance (E) between the given stack thickness+/−2 nm.

## Claims

### Claim 1

A method of assembly of a first element and a second element each having a back face and an assembly surface by direct bonding, at least the assembly surface of the first element comprising at least one first portion with at least one first metal part surrounded by at least one dielectric material, said first metal part having a free surface recessed from the dielectric material at said assembly surface, said method comprising:
a step A) to bring the two assembly surfaces into contact such that direct bonding is obtained between the assembly surfaces, said step taking place at ambient temperature, said first and second elements forming a stack with a thickness, and
a step B) taking place after step A), said step B) comprising
B1) a step to hold the back faces of the first and the second elements in position so that they are immobilized,
B2) a step to apply a heat treatment to said stack, wherein
during a first phase of the heat treatment, the back faces of the first and second elements are held in place and a first heat treatment temperature between 50° and 400° C. is constantly applied to the stack for a first time period, and
during a second phase of the heat treatment, the first and second elements are no longer held in place and a second heat treatment temperature between 50° and 400° C. is constantly applied to the stack for a second time period.

### Claim 2 (depends on 1)

The assembly method according to claim 1, in which during step B1 and the first phase of B2, the back faces of the first and second elements are held in position such that they are held at a fixed distance between the stack thickness−1 nm and the stack thickness+1 nm.

### Claim 3 (depends on 1)

The assembly method according to claim 1, in which the assembly surface of the second element comprises at least one second portion having a second metal part surrounded by at least one dielectric material, said second metal part having a free surface recessed from the dielectric material at said assembly surface, and in which contact is made during step A) so as to align the first metal part of the first element and the second metal part of the second element.

### Claim 4 (depends on 1)

The assembly method according to claim 1, in which during step B1 and the first phase of B2, the stack is placed in a holding device with two planar members positioned in plane arrangement with the back faces of the first and second elements, respectively, a distance separating the members being between the stack thickness−2 nm and the stack thickness+2 nm.

### Claim 5 (depends on 3)

The assembly method according to claim 3, in which the respective recess of the surfaces of the first and second metal parts from the dielectric material is less than or equal to 20 nm.

### Claim 6 (depends on 1)

The assembly method according to claim 1, in which step A) takes place at ambient temperature and atmospheric pressure.

### Claim 7 (depends on 1)

The assembly method according to claim 1, said stack being curved, said method comprises a stack flattening step after step A) and before and/or during the heat treatment in order to eliminate said curvature.

### Claim 8 (depends on 7)

The assembly method according to claim 7, in which a force of less than 3 kN is applied to the stack so as eliminate the curvature.

### Claim 9 (depends on 1)

The assembly method according to claim 1, in which, before step A), there is at least one assembly surface polishing step such that roughness of the assembly surfaces is less than 0.7 nm RMS, and hydrophily is less than 20°.

### Claim 10 (depends on 4)

The assembly method according to claim 4, the planar members of said holding device are at least as large as a surface area of the back faces of the first and second elements.

### Claim 11 (depends on 3)

The assembly method according to claim 3, in which the first and second metal parts are made of copper, aluminum, tungsten, or titanium, and the dielectric material is an oxide or a nitride.

### Claim 12 (depends on 1)

The assembly method according to claim 1, in which several first elements are assembled to several second elements simultaneously.

### Claim 13 (depends on 3)

The assembly method according to claim 3, in which the first and the second elements are microelectronic and/or nanoelectronic substrates, the first and second metal parts forming electrical interconnections.

### Claim 14 (depends on 11)

The assembly method according to claim 11, wherein the dielectric material is an oxide comprising one of SiO2, SiOCH and Al2O3 or the dielectric material is a nitride comprising Si3N4.

### Claim 15 (depends on 1)

The assembly method according to claim 1, wherein the second heat treatment temperature is selected as a function of a distance of the recess of the free surface of the first metal part from the dielectric material at the assembly surface at a beginning of the heat treatment.

### Claim 16 (depends on 1)

The assembly method according to claim 1, wherein the first heat treatment temperature is equal to the second heat treatment temperature.

### Claim 17 (depends on 1)

The assembly method according to claim 1, wherein the second heat treatment temperature is lower than the first heat treatment temperature.