Granted Patent B2

US 12,456,693 · App. 17/930,156 · Granted Oct 28, 2025

Inventor: Katsuya Kato (Yokkaichi, JP)

Assignee: Sandisk Technologies, Inc.

H01L23/544G03F7/0002G03F7/707G03F7/70716

Abstract

Claims (46)

1 . A method, comprising:

forming an alignment mark in a kerf region;

forming at least one material portion over the alignment mark;

patterning the at least one material portion to expose the alignment mark located in the kerf region;

forming a photoresist material layer over the patterned portions of the at least one material portion located in die regions and over the alignment mark located in the kerf region;

lithographically patterning the photoresist material layer into die-region photoresist material portions that are formed within die regions and kerf-region photoresist material portion that is formed within the kerf region; and

measuring an overlay between the kerf-region photoresist material portion and the alignment mark using radiation having a peak wavelength that is less than 380 nm and that is focused at a focal plane located a height that is vertically raised above a horizontal plane including a top surface of the alignment mark by a vertical distance that is in a range from 50% to 100% of a maximum thickness the kerf-region photoresist material portion.

2 . The method of claim 1 , wherein the radiation has a wavelength in a range from 150 nm to 260 nm.

3 . The method of claim 1 , further comprising determining a position of a previous alignment mark using visible light radiation having a peak wavelength of 400 nm or greater.

4 . The method of claim 1 , wherein an average thickness of the photoresist material layer is less than a total height of the at least one material portion.

5 . The method of claim 1 , wherein a portion of the photoresist material layer located within the kerf region has a top surface segment that is located below a horizontal plane including a topmost horizontal surface of the at least one material portion.

6 . The method of claim 1 , wherein an average thickness of the photoresist material layer is greater than 2 times the peak wavelength of the radiation.

7 . The method of claim 1 , wherein the one of the kerf-region photoresist material portion has a contoured top surface with a height variation that is at least 5% of an average height of the contoured top surface.

8 . The method of claim 7 , wherein a minimum height of the contoured top surface is greater than 2 times the peak wavelength of the radiation.

9 . The method of claim 7 , wherein a minimum height of the contoured top surface is greater than 10 times the peak wavelength of the radiation.

10 . The method of claim 1 , wherein the vertical distance is at least 5 times the peak wavelength of the radiation.

11 . The method of claim 1 , wherein:

the kerf-region photoresist material portion is formed with a first tapered sidewall and a second tapered sidewall having a same tilt direction in a vertical cross-sectional view;

a first angle between a horizonal plane including a top surface the alignment mark and the first tapered sidewall is an obtuse angle; and

a second angle between the horizontal plane and the second tapered sidewall is an acute angle.

12 . The method of claim 11 , wherein:

the alignment mark comprises two portions that are laterally spaced apart in a vertical cross-sectional view; and

an entirety of the kerf-region photoresist material portion is formed between the two portions of the proximal alignment mark in the vertical cross-sectional view.

13 . The method of claim 1 , wherein the at least one material portion comprises at least 100 repetitions of a unit layer stack that includes an insulating layer and a spacer material layer such that the insulating layers and the spacer material layers form an alternating stack along a vertical direction.

14 . The method of claim 13 , further comprising:

etching the alternating stack to form a staircase region in the alternating stack using the die-region photoresist material portions as a mask;

forming memory openings through the alternating stack; and

forming a memory opening fill structures in the memory openings, wherein each memory fill opening structure comprises a memory film and a vertical semiconductor channel.

15 . The method of claim 1 , wherein:

the at least one material portion has a thickness that is greater than 3 microns;

the photoresist material layer has a contoured top surface and has an average thickness that is less than 3 microns; and

a ratio of a reflectivity of the photoresist material layer to a reflectivity of a material of the proximal alignment mark is in a range from 1.5 to 2 at the peak wavelength of the radiation.

16 . An overlay measurement apparatus, comprising:

a chuck configured to mount a semiconductor wafer thereupon;

an ultraviolet radiation source configured to emit ultraviolet radiation having a peak wavelength of 380 nm or less;

a visible light source configurated to emit visible light;

a camera configured to sequentially generate images of an area with changes in a location of a focal plane along a vertical direction that is perpendicular to a top surface of the chuck; and

a controller configured to:

analyze the images generated by the camera based on the ultraviolet radiation reflected from the semiconductor wafer;

measure an overlay offset of an image of the top surface of a photoresist material portion relative to an alignment mark located within the semiconductor wafer in proximity to the photoresist material portion;

select the target focus horizontal plane at a location that has a vertical distance from a top surface of the semiconductor wafer that is in a range from 50% to 100% of a maximum height of the photoresist material portion; and

determine a position of a previous alignment mark based on reflection of the visible light emitted from the visible light source and reflected from the semiconductor wafer.

17 . The overlay measurement apparatus of claim 16 , wherein the controller is further configured to:

determine a height of a target focus horizontal plane at which a top surface of the photoresist material portion is located; and

change the focal plane of the camera to the target focus horizontal plane.

18 . The overlay measurement apparatus of claim 16 , wherein the ultraviolet radiation has a peak wavelength in a range from 150 nm to 260 nm.

Assignments (4)

Continuity (1)

References Cited (21)