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CN-121994818-A - Wafer surface defect detection optical system capable of recycling light energy

CN121994818ACN 121994818 ACN121994818 ACN 121994818ACN-121994818-A

Abstract

The invention relates to a wafer surface defect detection optical system with repeatable utilization of light energy, belongs to the technical field of laser detection, and particularly relates to detection of non-pattern wafer surface defect laser. The invention provides a wafer surface defect detection optical system capable of recycling light energy, which comprises a first objective lens and a second objective lens which are symmetrically arranged on two sides above a wafer, and a reflecting mirror group which is arranged on the outer side of the first objective lens and/or the second objective lens relative to the circle center of the wafer, wherein the reflecting mirror group comprises at least one reflecting element arranged on the outer side of the second objective lens. The invention can effectively recycle the light energy, and realizes the repeated circular focusing irradiation of the laser beam to the detection point on the surface of the wafer by matching the reflecting mirror group with the double objective lenses which are symmetrically arranged.

Inventors

  • LU GUOHUA
  • WANG DI
  • ZHANG FENG

Assignees

  • 江苏芯势科技有限公司

Dates

Publication Date
20260508
Application Date
20260316

Claims (10)

  1. 1. The wafer surface defect detection optical system capable of recycling light energy is characterized by comprising a first objective lens and a second objective lens which are symmetrically arranged on two sides above a wafer; the reflecting mirror group is arranged at the outer side of the first objective lens and/or the second objective lens relative to the circle center of the wafer, and comprises at least one reflecting element arranged at the outer side of the second objective lens; the laser beam is focused by a first objective lens to form a primary converging beam which is focused on an F point on the surface of a wafer, the F point is a focus, then the primary converging beam is reflected on the surface of the wafer to form a primary reflecting beam and a primary diverging beam, the primary reflecting beam is collimated by a second objective lens which is overlapped with the focus of the first objective lens, the collimated primary reflecting beam is reflected by a reflecting lens to form a primary reflecting beam which is parallel to the collimated primary reflecting beam and opposite in direction and is separated by a certain distance, the primary reflecting beam is again incident on the F point and is focused by the second objective lens, the secondary reflecting beam is reflected by the wafer again to form a secondary reflecting beam and a secondary diverging beam, the secondary reflecting beam is collimated by the reflecting lens, or the primary reflecting beam is focused on the F point again by the first objective lens after being processed by the reflecting lens, if other reflecting elements of the reflecting lens are arranged outside the first objective lens, the secondary reflecting beam which is parallel to the laser beam and identical in direction and is separated by a certain distance can be formed and is focused on the F point again after being reflected by the first objective lens, and the step is repeated to realize repeated focusing on the F point, thus at least two times of circularly irradiating the F point to focus the F point on the wafer, the energy of the wafer can be increased, if the scattered light is scattered by the particle is generated on the surface of the wafer, the scattered light energy is obviously higher than the energy of single irradiation after being collected by the light receiving assembly, so that the detection sensitivity is improved.
  2. 2. The wafer surface defect inspection optical system of claim 1 wherein the light receiving assembly comprises at least one light receiving objective lens located in an area above point F.
  3. 3. The optical system for detecting surface defects of a wafer according to claim 2, wherein the mirror group comprises a first mirror arranged outside the second mirror, the first mirror is of an isosceles right triangle structure, the bottom side of the first mirror faces the second mirror, the first mirror can generate a 180-degree retroflection effect on the primary reflection light beam to form a primary retroflection light beam and generate offset, the primary retroflection light beam does not coincide with the primary reflection light beam, the primary retroflection light beam enters the second mirror again and then converges at a point F, the point F is irradiated for the second time, and then reflected again by the surface of the wafer to form a secondary reflection light beam which enters the first objective, the second object is irradiated for the total of two times after being collimated.
  4. 4. The optical system for detecting surface defects of a wafer according to claim 3, wherein a vertical light receiving objective lens vertically facing the point F is arranged right above the point F.
  5. 5. The optical system for detecting surface defects of a wafer according to claim 2, wherein the reflecting mirror group comprises a first reflecting device and a second reflecting device which are respectively arranged on the outer sides of the first objective lens and the second objective lens, the first reflecting device and the second reflecting device are respectively composed of two mutually perpendicular and opposite small reflecting mirrors, the primary reflecting light beam can generate a 180-degree retroflection effect on the primary reflecting light beam after sequentially passing through the two small reflecting mirrors of the second reflecting device and form a primary retroflection light beam, the primary retroflection light beam is not overlapped with the primary reflecting light beam, the primary retroflection light beam is converged at a point F after entering the second objective lens again, the point F is irradiated for the second time, and then reflected again by the surface of the wafer to form a secondary retroflection light beam which enters the first objective lens, and passes through the two small reflecting mirrors of the first reflecting device in sequence after being collimated, the secondary retroflection light beam passes through the first objective lens and is focused at a point F again, and the point F is irradiated for three times in total.
  6. 6. The optical system for detecting surface defects of a wafer according to claim 5, wherein a first light receiving objective lens vertically facing the point F and a second light receiving objective lens obliquely facing the point F are arranged above the point F, the first light receiving objective lens collecting scattered light in a direction perpendicular to the wafer, and the second light receiving objective lens collecting scattered light at a larger angle with respect to a normal line of the wafer.
  7. 7. The optical system for detecting surface defects of a wafer according to claim 2, wherein the mirror group comprises a first mirror and a second mirror which are respectively arranged at the outer sides of the first objective lens and the second objective lens, the first mirror and the second mirror are both plane mirrors, the primary reflected light beam sequentially passes through the second mirror to reach the second mirror, then can generate a horizontal primary reflected light beam which faces one side of the first objective lens for the primary reflected light beam, the primary reflected light beam reaches the second mirror, the second mirror can reflect the primary reflected light beam to form a primary reflected deflection light beam to reach the first mirror, the secondary reflected light beam generated by the first mirror passes through the first objective lens and then is converged at the point F again, the point F is irradiated by the second mirror and then reflected again by the surface of the wafer to form a secondary reflected light beam to enter the second mirror, then the light beam motion can be circularly performed, and then, at least five times of subsequent arbitrary reflected light beams can be generated, and the secondary reflected light beam and any subsequent reflected light beams are parallel to the laser beam and do not coincide with the primary reflected light beam.
  8. 8. The wafer surface defect detection optical system of claim 7, wherein a tilted light receiving objective lens is disposed above the point F and tilted toward the point F for collecting scattered light at a larger angle relative to the wafer normal.
  9. 9. The optical system for detecting wafer surface defects according to claim 2, wherein the mirror group comprises a first mirror and a second mirror which are respectively arranged at the outer sides of the first objective lens and the second objective lens, a third mirror and a fourth mirror are respectively arranged beside the first mirror and the second mirror, the first mirror, the second mirror, the third mirror and the fourth mirror are all plane mirrors, the primary reflected light beam sequentially passes through the second mirror and then reaches the second mirror to generate a primary forward retroreflection front light beam for the primary reflected light beam, the primary retroreflection front light beam can reach the fourth mirror and is reflected by the fourth mirror to reach the third mirror, the third mirror can reflect a primary back light beam and reach the first mirror, the primary retroreflection light beam is reflected by the first mirror and then converged at the F point again after passing through the first objective lens, the F point is irradiated by the second mirror, then is reflected again by the wafer surface to form a secondary reflected light beam, the secondary reflected light beam can be circularly moved and generate a secondary and subsequent retroreflection front light beam, and the subsequent retroreflection front light beam can be reflected by the second mirror and at least coincide with the subsequent retroreflection front light beam and the subsequent retroreflection front light beam can be realized at least with the subsequent retroreflection front light beam and the subsequent retroreflection back light beam is not coincide with the subsequent retroreflection front light beam.
  10. 10. The optical system for detecting surface defects of a wafer according to claim 9, wherein a vertical light receiving objective lens vertically opposite to the point F is arranged right above the point F, and a plurality of beam expanding lenses respectively positioned on the optical paths of the intermediate beams of any number of times are arranged between the third reflecting mirror and the fourth reflecting mirror.

Description

Wafer surface defect detection optical system capable of recycling light energy Technical Field The invention relates to a wafer surface defect detection optical system with repeatable utilization of light energy, belongs to the technical field of laser detection, and particularly relates to detection of non-pattern wafer surface defect laser. Background The main technical scheme of the current wafer surface defect detection is that laser irradiates the wafer surface, meanwhile, the wafer moves linearly at a constant speed in a certain direction and rotates at a same step high speed, the wafer is scanned from the center to the edge of the wafer, the linear movement distance is the radius R of the wafer, therefore, the track of the laser on the wafer surface is a spiral line, when the laser irradiates a defect object, scattered light signals are generated, the scattered light signals are collected by a scattered light collecting system arranged right above a laser spot, and the position of the defect on the wafer surface can be determined by recording the time of the signals and the speed of the linear and rotary movement of the wafer. The industry adopts the basic principle to realize defect detection, such as patent CN119438221A, CN119901753A, CN120213941A, CN 120820548A. The high laser power is the key to obtaining a stronger light scattering signal, according to the light scattering principle, for particles with a certain size, the light scattering intensity is proportional to the energy of a laser beam and inversely proportional to the 4 th power of the wavelength, as the size of detected particles is smaller, the power of the laser is gradually increased in the industry, from tens of milliwatts to hundreds of milliwatts, even the current development is carried out to the watt level, the required wavelength is also developed from visible light to ultraviolet or even deep ultraviolet, extremely high technical requirements are provided for manufacturers of the laser, and extremely high cost burden and reliability risks are also provided for wafer surface defect detection equipment manufacturers. In addition, in consideration of the detection speed, the rotation scanning speed of the light spot during detection is related to the light spot focused on the surface of the wafer, and the larger the light spot is, the faster the scanning speed is, so the light spot cannot be reduced to the limit. However, the larger the spot, the corresponding decrease in the light energy density within the spot, resulting in a decrease in the intensity of scattered light. In the current industry, as described in the above patent, a laser emits a beam of laser to irradiate the area to be detected, and the detected object is a smooth wafer, so that the beam is reflected after irradiating the area to be detected, and the beam is not recycled, i.e. how much light energy is emitted by the laser, only how much light energy can be used during detection, and the particle is generally nano-sized, so that the actual light utilization rate is extremely low. Disclosure of Invention In order to solve the problems, the invention provides a wafer surface defect detection optical system with reusable light energy, which comprises a first objective lens and a second objective lens which are symmetrically arranged on two sides above a wafer, a reflector group, a lens assembly and a lens assembly, wherein the reflector group is arranged on the outer side of the first objective lens and/or the second objective lens relative to the center of the wafer, and comprises at least one reflecting element arranged on the outer side of the second objective lens; After the laser beam (namely incident light) is focused by a first objective lens, a primary converging light beam is formed by a certain inclination angle and focused on an F point on the surface of a wafer, the F point is taken as a focus, then the primary reflecting light beam is reflected on the surface of the wafer to form a primary reflecting light beam and a primary diverging light beam, the primary reflecting light beam is collimated by a second objective lens which coincides with the focus of the first objective lens, the primary reflecting light beam after collimation is reflected by a reflecting mirror group and forms a primary reflecting light beam which is parallel to the primary reflecting light beam after collimation and opposite in direction and is separated by a certain distance, the primary reflecting light beam is again incident on the F point by the second objective lens and is reflected again to form a secondary reflecting light beam and a secondary diverging light beam by the wafer, and the secondary reflecting light beam is collimated by the first objective lens; if other reflecting elements of the reflecting mirror group are arranged outside the first objective lens, secondary retroreflected light beams which are parallel to the laser beams, have the same direction and are s