# US 2019/0378769 A1 · Method of and system for determining an overlay or alignment error between a first and a second device layer of a multilayer semiconductor device

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- Number: US 2019/0378769 A1
- Document ID: US20190378769A1
- Status: Published application
- Kind: A1
- Application number: 16/477,347
- Filed: 2018-01-11
- Published: 2019-12-12
- Earliest claimed: 2017-01-13
- Assignees: Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO
- Applicants: Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO
- Inventors: Violeta Navarro Paredes; Maarten Hubertus van Es; Hamed Sadeghian Marnani
- Web page: https://patentgrep.com/patent/US20190378769A1

## CPC

- G01Q 60/32: AC mode
- G03F 7/70633: {Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching}
- H10P 72/50: for positioning, orientation or alignment
- H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects}
- G01Q 60/38: Probes, their manufacture, or their related instrumentation, e.g. holders
- G01Q: SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

The present document relates to a method of determining an overlay or alignment error between a first and a second device layer of a multilayer semiconductor device (26) using an atomic force microscopy system (20). The system comprises a scan head (22) including a probe (28). The probe includes a cantilever and a probe tip (30). The method comprises moving the probe tip and the semiconductor device relative to each other for scanning of the surface of the semiconductor device with the probe tip, wherein the probe tip is intermittently or continuously in contact with the surface during scanning. During scanning a signal application actuator (70) applies an acoustic input signal to the substrate, and motion of the probe tip is monitored with a tip position detector for obtaining an output signal, to be analyzed for mapping subsurface structures in different device layers. The signal application actuator includes a shear wave actuator to apply a shear acoustic wave (90) in the substrate. The output signal (39) is indicative of torsional deflection of the probe tip. The document further describes a system.

## Claims

### Claim 1

A method of determining an overlay or alignment error between a first device layer and a second device layer of a multilayer semiconductor device on a substrate using an atomic force microscopy system, wherein the atomic force microscopy system comprises a scan head including a probe, and the probe comprises a cantilever and a probe tip arranged on the cantilever, wherein the method comprises:
moving the probe tip and the multilayer semiconductor device relative to each other in one or more directions parallel to a surface of the multilayer semiconductor device for performing a scanning of the surface with the probe tip, wherein the probe tip is intermittently or continuously in contact with the surface during said scanning;
applying, during said scanning; and using a signal application actuator, an acoustic input signal to the substrate;
monitoring a motion of the probe tip relative to the scan head with a probe tip position detector during said scanning for obtaining an output signal; and
analyzing the output signal for generating a mapping of a one or more subsurface structures below the surface of the multilayer semiconductor device, the one or more subsurface structures being located in at least one of the first device layer or the second device layer, and
determining the overlay or alignment error between the first device layer and the second device layer based on the mapping;
wherein the signal application actuator includes a shear wave actuator, and
wherein the applying an acoustic input signal comprises applying an acoustic input signal to the substrate using at least the shear wave actuator to provide a shear acoustic wave in the substrate, and
wherein the output signal at least includes a sensor signal component indicative of a torsional deflection of the probe tip, and
wherein the method includes obtaining said sensor signal component indicative of the torsional deflection of the probe tip.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the acoustic input signal comprises an input signal component having a frequency within a range of 20% from at least one mode of torsional resonance of the cantilever.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the acoustic input signal comprises an input signal component having a frequency within a range of 100 kilohertz to 50 megahertz.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the signal application actuator, in addition to the shear wave actuator, comprises a further actuator cooperating with the cantilever or the probe tip, and
wherein the method comprises applying a flexural vibration signal to the cantilever or the probe tip using the further actuator.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the flexural vibration signal comprises at least one flexural signal component having a frequency in a range between 10 kilohertz to 2200 megahertz.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the acoustic input signal comprises multiple input signal components at various frequencies, the multiple input signal components including:
a first input signal component at a first frequency, and
a second input signal component at a second frequency,
wherein the first frequency and the second frequency are within one of the group consisting of:
a range of 20% from a mode of torsional resonance of the cantilever; and
a range of 20% from a mode of flexural resonance of the cantilever.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the analyzing the output signal decouples each of the multiple output signal components pertaining to different signal components of said multiple signal components or said sensor signal component indicative of a torsional deflection.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the acoustic input signal applied to the substrate for providing the shear acoustic wave in the substrate comprises an input signal component having a frequency within a range of 50 megahertz to 500 gigahertz.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the acoustic input signal comprises a third input signal component at a third frequency and a fourth input signal component at a fourth frequency,
wherein the third input signal component and, the fourth input signal component together provide a mixed acoustic signal,
wherein the mixed acoustic signal comprises a fifth signal component having a frequency equal to a difference between the third frequency and the fourth frequency,
wherein at least one of:
the frequency of the fifth signal component is below 1 gigahertz; and/or
the frequency of the fifth signal component is within a range of 20% from a mode of flexural or torsional resonance of the cantilever.

### Claim 10

An atomic force microscopy system for determining an overlay or alignment error between a first device layer and a second device layer of a multilayer semiconductor device on a substrate, wherein the system comprises:
a substrate carrier for supporting the substrate;
a scan head including a probe, and wherein the probe comprises a cantilever and a probe tip arranged on the cantilever;
an actuator configured to move the substrate carrier or the scan head, such as to move the probe tip and the multilayer semiconductor device relative to each other in one or more directions parallel to a surface of the multilayer semiconductor device for performing a scanning of the surface with the probe tip, wherein the probe tip is intermittently or continuously in contact with the surface during said scanning;
a signal application actuator for applying, during said scanning, an acoustic input signal to the substrate;
a probe tip position detector for monitoring a motion of the probe tip relative to the scan head during said scanning for obtaining an output signal; and
a signal analyzer configured for;
analyzing the output signal for generating a mapping of a one or more subsurface structures located in at least one of the first device layer or the second device layer, and
determining the overlay or alignment error between the first device layer and the second device layer based on the mapping;
wherein the signal application actuator includes a shear wave actuator for applying a shear acoustic wave in the substrate; and
wherein the signal analyzer is configured for obtaining from the output signal a signal component indicative of a torsional deflection of the probe tip.

### Claim 11 (depends on 10)

The system according to claim 10, wherein the signal application actuator is configured for providing the acoustic input signal including an input signal component having a frequency within a range of 100 kilohertz to 50 megahertz.

### Claim 12 (depends on 10)

The system according to claim 10, wherein the signal application actuator further comprises a further actuator cooperating with the cantilever or the probe tip, and
wherein the further actuator is configured for applying a flexural vibration signal to the cantilever or the probe tip.

### Claim 13 (depends on 10)

The system according to claim 10, wherein the analyzer is configured for analyzing the output signal such as to decouple output signal components pertaining to different signal components included in the output signal, wherein each of the different signal components is associated with a different frequency or frequency range.

### Claim 14 (depends on 10)

The system according to claim 10, wherein the shear wave actuator is configured for providing the shear acoustic wave of the acoustic input signal including an input signal component having a frequency within a range of 50 megahertz to 500 gigahertz, and
wherein the shear wave actuator is configured for applying the shear acoustic wave of the acoustic input signal comprising a third input signal component at a third frequency and a fourth input signal component at a fourth frequency,
wherein the third input signal component and the fourth input signal component-together provide a mixed acoustic signal comprising a fifth signal component having a frequency equal to a difference be the third frequency and the fourth frequency, and
wherein the frequency of the fifth signal component is below 1 gigahertz.

### Claim 15 (depends on 14)

The system according to claim 14, wherein for applying the acoustic input signal by a photo-thermal acoustic stimulation, the shear wave actuator includes a pulsed laser for providing a pulse of optical radiation having a time-varying intensity,
wherein the pulsed laser is configured for impinging the pulse of optical radiation on a layer of absorbing material located on a side face of the substrate,
wherein the side face is transverse to the surface of the substrate,
wherein the absorbing material is configured for absorbing optical energy of the optical radiation, and
wherein for applying the shear acoustic wave including the third and fourth frequency, the layer of absorbing material includes at least one of the group consisting of:
a first portion having a first thickness which is inversely proportional to the third frequency,
a second portion having a second thickness which is inversely proportional to the fourth frequency; and
a multiple absorption layer wherein each absorption layer has a thickness corresponding with at least one of the third or fourth frequency.

### Claim 16 (depends on 10)

The system according to claim 10, wherein the signal application actuator is configured for providing the acoustic input signal including an input signal component having a frequency within a range of 100 kilohertz to 10 megahertz.

### Claim 17 (depends on 10)

The system according to claim 10, wherein the signal application actuator is configured for providing the acoustic input signal including an input signal component having a frequency within a range of 50 megahertz to 500 gigahertz.

### Claim 18 (depends on 1)

The method according to claim 1, wherein the acoustic input signal comprises an input signal component having a frequency within a range of 100 kilohertz to 10 megahertz.