US-12625424-B2 - Method of annealing reflective photomask by using laser

US12625424B2US 12625424 B2US12625424 B2US 12625424B2US-12625424-B2

Abstract

A laser annealing method performed on a reflective photomask may include preparing a reflective photomask including a pattern area and a border area surrounding the pattern area and irradiating a laser beam onto the border area of the reflective photomask. The irradiating of the laser beam may include split-irradiating a plurality of laser beam spots onto the border area. Each of the plurality of laser beam spots may be shaped using a beam shaper. The beam shaper may include a blind area, a transparent area at a center of the blind area, and a semitransparent area between the blind area and the transparent area. Each of the plurality of laser beam spots may include a center portion passing through the transparent area and having a uniform energy profile and an edge portion passing through the semitransparent area and having an inclined energy profile.

Inventors

Hakseung Han
Sanguk Park
JONGJU PARK
Raewon Yi

Assignees

SAMSUNG ELECTRONICS CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20240214
Priority Date: 20200122

Claims (19)

1 . A laser annealing apparatus comprising: a laser source; a collimator; a beam shaper; a projection lens; and a mask stage, wherein the beam shaper comprises a blind area, a transparent area at a center of the blind area, and a semitransparent area between the blind area and the transparent area.
2 . The laser annealing apparatus of claim 1 , wherein the transparent area has a rectangular shape, and the semitransparent area has a frame shape surrounding the transparent area.
3 . The laser annealing apparatus of claim 1 , wherein the semitransparent area comprises bars or segments at opposite sides of the transparent area.
4 . The laser annealing apparatus of claim 1 , wherein the semitransparent area of the beam shaper has a transparency gradient which increases from the blind area toward the transparent area.
5 . The laser annealing apparatus of claim 4 , wherein the semitransparent area comprises a plurality of cut-out portions each having at least one of a stepped shape, a slit shape, a funnel shape, and a hole shape.
6 . The laser annealing apparatus of claim 4 , wherein the semitransparent area has a transparency variation at least three times over the semitransparent area.
7 . The laser annealing apparatus of claim 1 , wherein the beam shaper comprises a light blocking layer defining the blind area and a semitransparent layer defining the semitransparent area.
8 . The laser annealing apparatus of claim 7 , wherein the beam shaper further comprises a transparent substrate, and the light blocking layer and the semitransparent layer are on the transparent substrate.
9 . The laser annealing apparatus of claim 1 , wherein the transparent area is an empty space, and the semitransparent area comprises a plurality of cut-out portions.
10 . A laser annealing apparatus comprising: a laser source; a collimator; a beam shaper; a projection lens; and a mask stage, wherein the laser source generates a laser beam having a pulse shape, wherein the beam shaper shapes the laser beam into a plurality of laser beam spots, wherein an energy profile of a center portion of each of the plurality of laser beam spots is flat and has a width of about 100 μm to about 200 μm, and an energy profile of an edge portion of each of the plurality of laser beam spots is inclined and has a width of about 5 μm to about 50 μm.
11 . The laser annealing apparatus of claim 10 , wherein the laser beam is irradiated to the beam shaper through the collimator.
12 . The laser annealing apparatus of claim 11 , wherein an energy profile of the laser beam has a gaussian shape, and an energy profile of each of the plurality of laser beam spots has a top hat shape.
13 . The laser annealing apparatus of claim 11 , wherein the projection lens irradiates the plurality of laser beam spots onto a border area of a reflective photomask.
14 . The laser annealing apparatus of claim 11 , wherein a split pitch of the plurality of laser beam spots is less than a width of each of the plurality of laser beam spots.
15 . The laser annealing apparatus of claim 14 , wherein the split pitch of the plurality of laser beam spots is 0.5 to 0.9 times the width of each of the plurality of laser beam spots.
16 . The laser annealing apparatus of claim 11 , wherein the plurality of laser beam spots have a pulse shape, and a duration of a pulse of each of the plurality of laser beam spots is about 10 μs or less.
17 . The laser annealing apparatus of claim 11 , wherein a spot shape of each of the plurality of the laser beam spots is rectangular.
18 . The laser annealing apparatus of claim 11 , wherein each of the plurality of laser beam spots comprises a center portion where transmittance is not adjusted and an edge portion where transmittance is adjusted.
19 . The laser annealing apparatus of claim 10 , wherein the beam shaper shapes an energy profile of an edge portion of the laser beam to be inclined.

Description

CROSS-REFERENCE TO THE RELATED APPLICATION This application is a continuation of U.S. patent application Ser. No. 18/048,949, filed Oct. 24, 2022, which is a continuation of U.S. patent application Ser. No. 16/911,601, filed Jun. 25, 2020, which application claims priority from Korean Patent Application No. 10-2020-0008564, filed on Jan. 22, 2020, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entireties. BACKGROUND The inventive concept relates to a method of lowering a reflectance of a reflective photomask by using a laser annealing method and a laser annealing apparatus. A border area of a reflective photomask is an area where forming of a pattern is forbidden. Therefore, the border area should have a sufficiently low reflectance, and thus, should not reflect light. A laser annealing method has been proposed for lowering a reflectance of the border area. However, in a general laser annealing method, a very gentle slope occurs in an edge area of the border area, and due to this, a forbidden area is unnecessarily widened. Therefore, in a case which uses a very short pulsed laser, a very steep slope occurs in the edge area of the border area, and due to this, a reflection layer and/or an absorption layer are/is physically damaged (e.g., cracked). SUMMARY The example embodiments of the disclosure provide a method of annealing a border area of a reflective photomask by using a laser. The example embodiments of the disclosure provide a laser annealing method for adjusting a slope of an edge area of a border area. The example embodiments of the disclosure provide a laser annealing apparatus. Various objects of the disclosure will be described in detail in the detailed description. A method of annealing a reflective photomask by using a laser in accordance with an embodiment of the disclosure may include preparing a reflective photomask including a pattern area and a border area surrounding the pattern area and irradiating a laser beam onto the border area of the reflective photomask. The irradiating of the laser beam may include split-irradiating a plurality of laser beam spots onto the border area. Each of the plurality of laser beam spots may be shaped using a beam shaper. The beam shaper may include a blind area, a transparent area at a center of the blind area, and a semitransparent area between the blind area and the transparent area. Each of the plurality of laser beam spots may include a center portion passing through the transparent area and having a uniform energy profile and an edge portion passing through the semitransparent area and having an inclined energy profile that increases from an outer edge of the edge portion toward the center portion. A method of annealing a reflective photomask by using a laser in accordance with an embodiment of the disclosure may include preparing a reflective photomask including a pattern area, a non-pattern area surrounding the pattern area, and a border area between the pattern area and the non-pattern area and irradiating a laser beam onto the border area of the reflective photomask to recess the border area. The irradiating of the laser beam may include split-irradiating a plurality of laser beam spots onto the border area. Each of the plurality of laser beam spots may include a center portion where transmittance is not adjusted and an edge portion where transmittance is adjusted. A method of annealing a reflective photomask by using a laser in accordance with an embodiment of the disclosure may include placing a reflective photomask on a stage, generating, by a laser source, a laser beam to irradiate the laser beam onto a beam shaper, shaping, by the beam shaper, the laser beam into a laser beam spot, and irradiating the shaped laser beam spot onto a border area of the reflective photomask. The border area may include a recess area and an edge area. The shaped laser beam spot may be irradiated onto the recess area at a first energy and is irradiated onto the edge area at an energy less than the first energy. A laser annealing apparatus in accordance with an embodiment of the disclosure may include a laser source, a collimator, a beam shaper, a projection lens, and a mask stage. The beam shaper may include a blind area, a transparent area at a center of the blind area, and a semitransparent area between the blind area and the transparent area. A reflective photomask in accordance with an embodiment of the disclosure may include a pattern area, a non-pattern area, and a border area between the pattern area and the non-pattern area. The border area may include a recess area including a top surface lower than a top surface of the pattern area and a top surface of the non-pattern area and an edge area between the pattern area and the recess area. A width of the edge area may be equal to or less than 1/20 of a width of the border area. A beam shaper in accordance with an embodiment of the disclosure ma