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EP-4160195-B1 - THIN FILM CHARACTERISTIC MEASURING APPARATUS

EP4160195B1EP 4160195 B1EP4160195 B1EP 4160195B1EP-4160195-B1

Inventors

  • PARK, JUN
  • AHN, SEH WON
  • JUNG, YUN SUK

Dates

Publication Date
20260506
Application Date
20200601

Claims (15)

  1. A thin film characteristic measuring apparatus used for measuring a thickness or a width of a thin film of a subject, the apparatus comprising: a light source (10) configured by a superluminescent diode (SLD); a first reflection mirror (30) reflecting a ray irradiated from the light source (10); a first actuator (35) reciprocating and tilting a first reflection mirror (30) in a predetermined angle range; a lens assembly (70) including a plurality of lenses, and in which the ray reflected by the first reflection mirror (30) is incident and transmitted; a first transparent plate (50) through which the ray irradiated from the light source (10) is transmitted; a third actuator (55) reciprocating and tilting the first transparent plate (50) in a predetermined angle range; a second transparent plate (60) through which the ray transmitted through the first transparent plate (50) is transmitted; and a fourth actuator (65) reciprocating and tilting the second transparent plate (60) in a predetermined angle range, wherein a tilting axis of the first transparent plate (50) and a tilting axis of the second transparent plate (60) are different from each other, wherein the ray transmitted through the second transparent plate (60) is reflected by the first reflection mirror (30), wherein , when the main rays of the ray are incident on the lens assembly (70) with a predetermined angle range to the optical axis (OA) of the lens assembly (70) while being incident on the lens assembly (70) from an on-axis position, the lens assembly (70) is configured so that an angle between a main ray of the rays transmitted through the lens assembly (70) and an optical axis (OA) of the lense assembly is equal to or smaller than an angle between the main ray (R1) incident on the lens assembly (70) and the optical axis (OA) of the lens assembly, and the main rays transmitted through the lens assembly (70) are parallel to each other or substantially parallel and, when the ray (R1) is incident on the lens assembly (70) from an off-axis position, the ray (R2) transmitted through the lens assembly forms an inclination with the optical axis (OA) of the lens assembly, so that a ray (R2) may be incident on the surface of an object with a direction perpendicular to the surface of said object, such that even though the main rays of the ray (R1) incident on the lens assembly (70) form different angles with the direction of the optical axis (OA) of the lens assembly (70), the main rays of the ray (R2) transmitted through the lens assembly and incident on the object are parallel to each other or substantially parallel to each other.
  2. The thin film characteristic measuring apparatus of claim 1, wherein when the angle between the main ray of the ray incident on the lens assembly (70) and the optical axis is 0 to 3.7°, the angle between the main ray of the ray transmitted through the lens assembly (70) and the optical axis is 0 to 0.1°.
  3. The thin film characteristic measuring apparatus of claim 1, wherein the light source (10) includes the optical fiber (11) delivering the ray, and the thin film characteristic measuring apparatus further includes a collimator (20) positioned between the light source (10) and the first reflection mirror (30), and the numerical aperture (NA) of the collimator is larger than the NA of the optical fiber.
  4. The thin film characteristic measuring apparatus of claim 1, further comprising: a second reflection mirror (40) reflecting the ray reflected by the first reflection mirror (30); and a second actuator (45) reciprocating and tilting the second reflection mirror (40) in a predetermined angle range, wherein the ray reflected by the second reflection mirror (40) is incident on the lens assembly (70).
  5. The thin film characteristic measuring apparatus of claim 4, wherein the ray transmitted through the second transparent plate (60) is refracted by the first reflection mirror (30) and the second reflection mirror (40), and then incident on the lens assembly (70).
  6. The thin film characteristic measuring apparatus of claim 1, wherein the lens assembly (70) includes: a first lens (71) configured by a negative lens, a second lens (72) disposed behind the first lens (71), and configured by a positive lens, a third lens (73) disposed in front of the first lens (71), and configured by the positive lens, a fourth lens (74) disposed between the third lens (73) and the first lens, and configured by a positive lens, and a fifth lens (75) disposed between the third lens (73) and the first lens (71), and configured by a negative lens.
  7. The thin film characteristic measuring apparatus of claim 6, wherein the lens assembly (70) further includes a sixth lens (76) disposed between the fifth lens (75) and the first lens (71), and configured by the positive lens, and the fourth lens (74) is disposed in front of the fifth lens (75) .
  8. The thin film characteristic measuring apparatus of claim 7, wherein when the angle between the main ray of the ray incident on the lens assembly (70) and the optical axis is 0 to 3.7°, the angle between the main ray of the ray transmitted through the lens assembly (70) and the optical axis is 0 to 0.1°.
  9. The thin film characteristic measuring apparatus of claim 7, wherein FL1 which is a sum of focal distances of the third lens (73), the fourth lens (74), the fifth lens (75), and the sixth lens (76) is shorter than FL2 which is a sum of focal distances of the third lens (73), the fourth lens (74), the fifth lens (75), the sixth lens (76), and the first lens (71), and a focal distance FL3 of the second lens (72) is longer than the FL1 and shorter than the FL2.
  10. The thin film characteristic measuring apparatus of claim 7, wherein when a diameter of an area formed by a ray incident on the third lens (73) parallel to the optical axis of the lens assembly (70) is D1, a diameter of an area formed when the ray transmitted through the lens assembly (70) touches a surface of the subject is D2, the sum of the focal distances of the third lens (73), the fourth lens (74), the fifth lens (75), the sixth lens (76), and the first lens (71) is FL2, and the focal distance of the second lens (72) is FL3, a value of FL3/FL2 is within a range of ±10% of a value of D2/D1.
  11. The thin film characteristic measuring apparatus of claim 7, wherein when a distance between the first reflection mirror (39) and the third lens (73) is L1, and a distance between the second lens (72) and the subject is L2, L1 and L2 are 20 mm or more, and an effective focal distance of the lens assembly (70) is 85 mm.
  12. The thin film characteristic measuring apparatus of claim 7, wherein the first lens (71) is an asymmetrical biconcave lens, the second lens (72) is a plano-convex lens, the third lens (73) is a positive meniscus lens, the fourth lens (74) is an asymmetrical double-convex lens, the fifth lens (75) is a plano-concave lens, and the sixth lens (76) is an asymmetrical double-convex lens.
  13. The thin film characteristic measuring apparatus of claim 6, wherein the thin film characteristic measuring apparatus includes a collimator (20) positioned between the light source (10) and the first reflection mirror (30), and a case (100) to which the lens assembly (70) and the first actuator (35) are fixed, and which accommodates the first reflection mirror (30), and is opened toward the collimator (20).
  14. The thin film characteristic measuring apparatus of claim 13, wherein a plurality of heat dissipation fins (36) is formed in the first actuator (35).
  15. The thin film characteristic measuring apparatus of claim 6, wherein the thin film characteristic measuring apparatus further includes a diffractive optical element positioned between the light source (10) and the lens assembly (70).

Description

TECHNICAL FIELD The present invention is an apparatus used to measure the characteristics of a thin film of a subject by using an interference phenomenon between wavelengths of reflected ray after being irradiated to the subject. BACKGROUND In optical disks, semiconductors, batteries, and various displays, thin films constituting each of these are formed, and in the manufacturing process thereof, measurement of the thickness and refractive index of the thin film is required. The thickness and refractive index of the thin film may be measured by reflectometry, and the reflectometer may correspond to a thin film layer measurement system. The reflectometer is a non-contact, non-destructive measuring apparatus that can measure the characteristics of a multi-layer thin film, and has the advantage of being able to measure without special preparation or processing of a subject. In this regard, US Patent No. 7286242 B2 (hereinafter, 'prior document') discloses Apparatus for Measuring Characteristics of Thin Film by Means of Two-dimensional Detector and Method of Measuring the Same. The thickness of the thin film may be measured on a sample substrate made of a substrate and a thin film by the apparatus according to the prior document. A ray irradiated from a light source is incident on a substrate having a thin film through a beam splitter and a lens 26. Among the ray incident on the sample substrate, some is reflected from the surface of the thin film, and the other part may be reflected at the boundary between the substrate and the thin film after passing through the thin film, and the two reflected rays have differences in optical paths. As such, the rays reflected from different surfaces of the sample substrate have differences in optical paths, and an interference phenomenon occurs due to the differences in optical paths. In addition, the differences in paths occur for each wavelength, and constructive interference or destructive interference is generated according to the wavelength of the light beam. The rays reflected from the sample substrate are projected on a spectroscope, and the spectroscope analyzes the projected reflected ray to obtain the intensity of the reflected ray as a function of the light wavelength. The result passes through a numeric converter and an information processor, and the thickness, refractive index, etc. of the thin film of the sample substrate are calculated accordingly to obtain a measured value. However, in the case of the apparatus and method according to the prior art, since only the thickness measurement can be made at any one spot of the sample substrate, the development of a thin film characteristic measuring apparatus capable of variously adjusting a position, a method, etc., to be measured is required. DISCLOSURE OF INVENTION TECHNICAL PROBLEM An object to be achieved by the present invention is to provide a thin film characteristic measuring apparatus that can effectively and accurately measure the thickness and/or width of a thin film of a subject in a region exceeding the size (diameter) of a ray irradiated to the subject. Another object to be achieved by the present invention is to provide a thin film characteristic measuring apparatus in which a ray irradiated to a subject is repeatedly deformed at a position thereof, and is incident and reflected in a direction perpendicular to the surface of the subject. Yet another object to be achieved by the present invention is to provide a thin film characteristic measuring apparatus which can effectively measure a thin film of a subject having a curved surface. Still yet another object to be achieved by the present invention is to provide a thin film characteristic measuring apparatus which can simultaneously measure several parts of the subject. US 2018/164089 A1 relates to a device and a method for optically measuring distances. US 2019/044494 A1 relates to a method of manufacturing a substrate for an acoustic wave device. US 5 087 987 A relates to a color-corrected telecentric lens used in an optical scanning system. US 2020/103220 A1 relates to a thickness measuring apparatus for measuring the thickness of a wafer by applying light having a transmission wavelength region to the wafer. US 2012/176623 A1 relates to an apparatus and a method for measuring characteristics of multi-layered thin films. The invention is defined by independent claim 1. Further embodiments of the invention are defined by the dependent claims. A thin film characteristic measuring apparatus according to an embodiment of the present invention is an apparatus used for measuring a thickness and/or a width of a thin film of a subject. The thin film characteristic measuring apparatus includes a light source, a first reflection mirror, a first actuator, and a lens assembly. The light source may be configured by a superluminescent diode (SLD). The first reflection mirror reflects a ray irradiated from the light source. The first actuator reciprocates and ti