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CN-121978874-A - Overlay mark structure, manufacturing method thereof and overlay mark size selection method

CN121978874ACN 121978874 ACN121978874 ACN 121978874ACN-121978874-A

Abstract

The invention provides an overlay mark structure, a manufacturing method thereof and an overlay mark size selection method, wherein the overlay mark structure comprises a mark groove formed in a photoresist layer, the depth of the mark groove is smaller than the thickness of the photoresist layer, and the width of the mark groove is smaller than 2 mu m. According to the invention, through the design of the narrow mark groove, the overlay measurement error caused by the shape distortion of the overlay mark itself due to the asymmetry of the surrounding patterns can be effectively reduced, the process robustness and the measurement accuracy of the overlay mark are fundamentally improved, and the product yield is further improved.

Inventors

  • LIU HUALONG
  • ZHANG XIANGPING

Assignees

  • 合肥晶合集成电路股份有限公司

Dates

Publication Date
20260505
Application Date
20260407

Claims (10)

  1. 1. An overlay mark structure, comprising a mark trench formed in a photoresist layer, wherein the depth of the mark trench is smaller than the thickness of the photoresist layer, and the width of the mark trench is smaller than 2 μm.
  2. 2. The overlay mark structure of claim 1, wherein the mark trench has a trench width of 0.3 μm to 2.0 μm.
  3. 3. The overlay mark structure of claim 1, wherein the mark trench has a depth greater than or equal to 0.15 μm and less than a thickness of the photoresist layer, wherein the thickness of the photoresist layer is greater than 2 μm.
  4. 4. A method for manufacturing an overlay mark structure, which is characterized by comprising the following steps: Coating a photoresist layer on a substrate; And forming a mark groove with a groove width smaller than 2 mu m in the photoresist layer through a photoetching process, wherein the depth of the mark groove is smaller than the thickness of the photoresist layer.
  5. 5. An overlay mark size selection method is characterized by comprising the following steps: providing a test photomask, wherein a plurality of overlay mark patterns with different widths and a plurality of CD bar patterns with different widths are integrated on a layout of the test photomask, and the widths of the overlay mark patterns are smaller than 2 mu m; providing a first substrate, wherein a first photoresist layer is formed on the first substrate, and a plurality of first mark grooves with different widths and a plurality of first CD bar grooves with different widths are formed in the first photoresist layer by using the test photomask through a photoetching process; measuring the width of the first CD bar groove, and screening out the optimal photoetching conditions of the photoetching process according to the width of the groove; providing a second substrate, wherein a second photoresist layer is formed on the second substrate, and a plurality of second mark grooves with different widths and a plurality of second CD bar grooves with different widths are formed under the optimal photoetching conditions by using the test photomask through a photoetching process; And measuring the groove depth of the second marking groove, and screening out a target marking groove according to the groove depth.
  6. 6. The overlay mark size selection method of claim 5, wherein the CD bar pattern has a width in the range of 0.5 μm to 4 μm and the overlay mark pattern has a width in the range of 0.3 μm to 2 μm.
  7. 7. The overlay mark size selection method as recited in claim 5, wherein two critical lithography conditions are provided during exposure of the lithography process, the two critical lithography conditions including a focus and an exposure dose, In exposure, the focal length is changed in a set step along one direction of the first substrate, and the exposure dose is changed in a set step along the other direction, so as to form a series of exposure areas with different combinations of focal length and exposure dose on the first substrate, wherein the one direction is perpendicular to the other direction.
  8. 8. The overlay mark size selection method of claim 5, wherein measuring a trench width of the first CD bar trench and screening out optimal lithographic conditions of the lithographic process based on the trench width further comprises: slicing the first substrate to prepare a first FEM structure, and measuring a CD bar graph in each exposure area through the first FEM structure to obtain a CD value under each photoetching condition; Drawing a poisson curve for each fixed exposure dose by taking the focal length as an abscissa and the CD value as an ordinate; and confirming the optimal photoetching conditions of the photoetching process according to the poisson curve.
  9. 9. The overlay mark size selection method of claim 5 or 8, wherein the optimal lithographic conditions comprise an optimal focus and an optimal exposure dose.
  10. 10. The overlay mark size selection method of claim 5, wherein screening the target mark trench according to the trench depth further comprises: And selecting the second marking groove with the groove depth larger than 0.15 mu m and the minimum value as the target marking groove.

Description

Overlay mark structure, manufacturing method thereof and overlay mark size selection method Technical Field The invention relates to the technical field of semiconductor manufacturing, in particular to an overlay mark structure, a manufacturing method thereof and an overlay mark size selection method. Background In the integrated circuit manufacturing process, the alignment accuracy of the photolithography process directly affects the device performance and yield. The excessive overlay error may cause defects such as leakage, open circuit or short circuit of the device. Therefore, the high-precision overlay measurement technology becomes a key link for guaranteeing the process stability and the product reliability. Currently, the industry typically makes specific overlay marks on the chip surface and obtains overlay bias data by optical or electron beam metrology equipment. However, in practice it has been found that when the pattern distribution around the overlay mark is asymmetric, the mark itself tends to form an asymmetric topography during photolithography and subsequent processing. This problem is particularly pronounced in thick film resist processes, where the generation of gases (e.g., N 2) within the resist film and the uneven thermal expansion profile during post-exposure bake results in an asymmetric tapered structure of the overlay mark profile (as shown in fig. 1, the longitudinal cross section of the mark in the form of a trapezoid is asymmetric at both waists, i.e., the values of a and b are different), thereby severely affecting the overlay measurement accuracy. Disclosure of Invention The invention aims to provide an overlay mark structure, a manufacturing method thereof and an overlay mark size selection method, which can effectively reduce the influence of the shape asymmetry of an overlay mark on a measurement error on the premise of meeting the requirements of a process on the thickness of a photoresist and not reducing the thickness of the photoresist and not changing the process flow. The invention provides an overlay mark structure, which comprises a mark groove formed in a photoresist layer, wherein the depth of the mark groove is smaller than the thickness of the photoresist layer, and the width of the mark groove is smaller than 2 mu m. In some embodiments, the marking trenches have a trench width of 0.3 μm to 2.0 μm. In some embodiments, the marking trench has a depth greater than or equal to 0.15 μm and less than a thickness of the photoresist layer, wherein the thickness of the photoresist layer is greater than 2 μm. On the other hand, the invention also discloses a manufacturing method of the overlay mark structure, which comprises the following steps: Coating a photoresist layer on a substrate; And forming a mark groove with a groove width smaller than 2 mu m in the photoresist layer through a photoetching process, wherein the depth of the mark groove is smaller than the thickness of the photoresist layer. In yet another aspect, the present invention also provides an overlay mark size selection method, comprising the steps of: providing a test photomask, wherein a plurality of overlay mark patterns with different widths and a plurality of CD bar patterns with different widths are integrated on a layout of the test photomask, and the widths of the overlay mark patterns are smaller than 2 mu m; providing a first substrate, wherein a first photoresist layer is formed on the first substrate, and a plurality of first mark grooves with different widths and a plurality of first CD bar grooves with different widths are formed in the first photoresist layer by using the test photomask through a photoetching process; measuring the width of the first CD bar groove, and screening out the optimal photoetching conditions of the photoetching process according to the width of the groove; providing a second substrate, wherein a second photoresist layer is formed on the second substrate, and a plurality of second mark grooves with different widths and a plurality of second CD bar grooves with different widths are formed under the optimal photoetching conditions by using the test photomask through a photoetching process; And measuring the groove depth of the second marking groove, and screening out a target marking groove according to the groove depth. In some embodiments, the CD bar pattern has a width ranging from 0.5 μm to 4 μm and the overlay mark pattern has a width ranging from 0.3 μm to 2 μm. In some embodiments, during exposure of the lithographic process, two critical lithographic conditions are provided, both of which include focus and exposure dose, In exposure, the focal length is changed in a set step along one direction of the first substrate, and the exposure dose is changed in a set step along the other direction, so as to form a series of exposure areas with different combinations of focal length and exposure dose on the first substrate, wherein the one direction is perpendic