Device and method applicable for measuring ultrathin thickness of film on substrate

Patent metadata

Field	Value
Publication number	US-2021199428-A1
Application number	US-201916730236-A
Country	US
Kind code	A1
Filing date	Dec 30, 2019
Priority date	Dec 30, 2019
Publication date	Jul 1, 2021
Grant date	—

Abstract

The present disclosure relates to a device and a method for measuring a thickness of an ultrathin film on a solid substrate. The thickness of the target ultrathin film is measured from the intensity of the fluorescence converted by the substrate and leaking and tunneling through the target ultrathin film at low detection angle. The fluorescence generated from the substrate has sufficient and stable high intensity, and therefore can provide fluorescence signal strong enough to make the measurement performed rapidly and precisely. The detection angle is small, and therefore the noise ratio is low, and efficiency of thickness measurement according to the method disclosed herein is high. The thickness measurement method can be applied into In-line product measurement without using standard sample, and therefore the thickness of the product can be measured rapidly and efficiently.

First claim

What is claimed is:

1 . A device for measuring a thickness of a target ultrathin film on a substrate, and the device comprising:
a radiation source configured to project an excitation radiation toward an upper surface of the target ultrathin film with an incident angle θ 1 with respect to the upper surface, wherein the incident angle θ 1 is near 90°; and a fluorescence X-ray detector configured to measure a fluorescence X-ray converted from the excitation radiation by the substrate with a grazing detection angle θ 2 with respect to the upper surface, over a preset grazing angular range.

2 . The device according to claim 1 , wherein the target ultrathin film has the thickness of a few nanometers (nm) or less.

3 . The device according to claim 1 , wherein the thickness of the target ultrathin film is 0.2 nm to 2 nm.

4 . The device according to claim 1 , wherein an energy of the excitation radiation is sufficiently high to excite the fluorescence X-ray from the substrate.

5 . The device according to claim 1 , wherein the excitation radiation comprises an X-ray beam or an electron beam.

6 . The device according to claim 1 , wherein the fluorescence X-ray detector is capable of scanning through a preset angular range with an angular step less than or equal to one hundredth of the preset angular range, an angular range is between 0° and 2° or beyond.

7 . The device according to claim 1 , further comprises a collimator configured to enable a detection of angular window or opening δθ 2 at least a tenth of total angular range of the grazing detection angle θ 2 or less.

8 . The device according to claim 1 , wherein the target ultrathin film has an X-ray scattering length density higher than an X-ray scattering length density of the substrate.

9 . The device according to claim 7 , wherein a test sample comprises the target ultrathin film and the substrate, the collimator is configured to control a detection of the fluorescence X-ray with the angular window or opening δθ 2 at any given the grazing detection angle θ 2 .

10 . The device according to claim 9 , wherein the collimator is configured to be between the test sample and the fluorescence X-ray detector.

11 . The device according to claim 8 , wherein the substrate comprises multiple layers of different materials or a single material layer including a silicon wafer, a GaAs wafer, or an InP wafer, the fluorescence X-ray includes those from one or more layers comprising the substrate, or from one or more elements comprising the substrate.

12 . The device according to claim 1 , wherein the fluorescence X-ray detector is capable of discerning energies and/or wavelengths of the fluorescence X-ray observed, thereby, to collect intensities of all of the fluorescence energies or wavelengths selected concurrently.

13 . A method for measuring a thickness of a target ultrathin film over a substrate, comprising:
projecting an excitation radiation toward an upper surface of the target ultrathin film with an incident angle θ 1 with respect to the upper surface of the target ultrathin film, wherein a range of the incident angle θ 1 is over 45° to 90°; and detecting a fluorescence X-ray converted from the excitation radiation by the substrate with a grazing detection angle θ 2 defined with respect to the upper surface of the target ultrathin film, wherein the grazing detection angle θ 2 is 2°≥θ 2 ≥0° or beyond.

14 . The method according to claim 13 , wherein the excitation radiation comprises an X-ray beam or an electron beam with its energy sufficiently high to excite the fluorescence X-ray from one or more preselected element in layers of the substrate.

15 . The method according to claim 13 , comprising detecting fluorescence X-ray intensities with a plurality of the grazing detection angles θ 2 , wherein a fluorescence X-ray detector is capable of measuring a distribution of the fluorescence X-ray intensities as a function of a fluorescence wavelength or energy; thereby to concurrently measure the fluorescence X-ray intensities originated from one or more layers comprising the substrate or from one or more elements of a compound substrate comprising InP, or GaAs.

16 . The method according to claim 13 , comprising calculating the thickness of the target ultrathin film based on an angular dependence of measured fluorescence X-ray intensities after the measured fluorescence X-ray being normalized with a fluorescence X-ray intensity measured in the absence of the target ultrathin film at the grazing detection angle θ 2 .

17 . The method according to claim 13 , wherein the target ultrathin film has the thickness less than a few nanometers.

18 . The method according to claim 13 , wherein the thickness of the target ultrathin film is 0.2 nm to 2 nm.

19 . The method according to claim 13 , further comprising a collimator to define an angular resolution δθ 2 of the fluorescence X-ray measured and leaked through the target ultrathin film, the value of the angular resolution OK is set to be at least a tenth of total angular range of the grazing detection angle θ 2 or less.

20 . The method according to claim 13 , further comprising a radiation source and a fluorescence X-ray detector, wherein the radiation source is configured to project the excitation radiation to generate the fluorescence X-ray from the substrate, the fluorescence X-ray detector is configured to receive the fluorescence X-ray leaked through the target ultrathin film over a range of the grazing detection angle θ 2 .

21 . The method according to claim 20 , wherein a device comprises a collimator installed in front of the fluorescence X-ray detector, both the collimator and the fluorescence X-ray detector are capable of moving in unity over a present angular range of the grazing detection angle θ 2 with an angular step size less than an angular resolution δθ 2 defined by the collimator.

22 . The method according to claim 13 , wherein the substrate is either a single layer structure or a multi-layer structure.

Assignees

• Ind Tech Res Inst

Inventors

• Liu Chun-Ting
• Chang Han-Yu
• He Bo-Ching
• Chen Guo-Dung
• Wu Wen-Li
• Fu Wei-En

Classifications

• H10P74/203

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• G01N2223/6116

  semiconductor wafer · CPC title

• G01N2223/61

  thin films, coatings · CPC title

• G01N2223/079

  incident electron beam and measuring excited X-rays · CPC title

• G01N2223/076

  X-ray fluorescence · CPC title