CN-122018229-A - Inspection method of multilayer multi-material photomask

CN122018229ACN 122018229 ACN122018229 ACN 122018229ACN-122018229-A

Abstract

The invention relates to a method for inspecting a multi-layer multi-material photomask, which comprises the following steps of S1, constructing an inspection Database, creating a three-dimensional data architecture representing the corresponding position material and height attribute of the photomask, generating a two-dimensional design layout Database only comprising the characteristics of a light transmission area and a light shielding area, S2, performing light calibration and inspection, namely performing light intensity calibration, setting a gray-scale lower limit and a gray-scale upper limit, thereby creating a full-coverage detection gray-scale range, performing Die-to-Database defect detection, and S3, analyzing and judging. The inspection method of the multilayer multi-material photomask can effectively adapt to the height difference and the material optical characteristic difference of the surface of the photomask, improve the imaging quality and the signal-to-noise ratio, reduce false defect signals and reliably identify real defects by constructing a three-dimensional data architecture, generating a two-dimensional design layout Database and carrying out light intensity calibration and Die-to-Database detection.

Inventors

GAN WEI
Tian Zhengzhou
LIAO DECAI
WU HONGBIN
BAO REN

Assignees

广州新锐光掩模科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260403

Claims (5)

1. A method of inspecting a multi-layer, multi-material photomask, comprising the steps of: s1, constructing a checking database: s1-1, establishing a three-dimensional data architecture representing the material and the height attribute of the corresponding position of a photomask according to the design graph, the material distribution and different process steps of the photomask through data processing; S1-2, acquiring multi-layer exposure data for constructing the photomask, performing Boolean logic operation on the multi-layer exposure data based on the logic of the three-dimensional data architecture, mapping the three-dimensional features with different heights onto a two-dimensional plane, and finally generating a two-dimensional design layout database only comprising the features of a light transmission area and a light shielding area; s2, light calibration and inspection: S2-1, calibrating light intensity, namely selecting a region corresponding to the maximum light shielding layer height and a light-transmitting substrate region without a light shielding material on an actual photomask as calibration points based on the height and material information in the three-dimensional data architecture, calibrating a minimum light flux value of the maximum light shielding layer region as a gray scale lower limit and calibrating a maximum light flux value of the light-transmitting substrate region as a gray scale upper limit in a transmission light mode, so as to establish a full-coverage detection gray scale range; S2-2, performing Die-to-Database defect detection, namely performing image acquisition on an actual photomask by using transmitted light, and performing Die-to-Database comparison detection on an actually acquired image and a two-dimensional design layout Database generated in the step S1-2 by using a gray scale range established in the step S2-1 so that image signals of all other light shielding material areas lower than the maximum light shielding layer height are contained in a gray scale threshold value of a light shielding area; S3, analyzing and judging that after the image of the actual photomask is acquired under the optimal optical parameters and the focusing state, the system compares the acquired image data of the actual photomask with the corresponding expected data in the two-dimensional design layout database, so that the defect position of the actual photomask is distinguished.
2. The method according to claim 1, wherein in the step S1-2, the two-dimensional layout database is a black-and-white region database, and is a two-dimensional layout at the same height.
3. The method of inspecting a multi-layer and multi-material photomask according to claim 1, wherein in the step S2-1, the region of the photomask having the greatest height of the chrome layer is selected as the lower limit of the gray scale value, the chrome-free quartz substrate region is selected as the upper limit of the gray scale value, and a dynamic detection range of 0-255 is established, so that the gray scale value of the chrome layer height lower than the maximum height naturally falls within the threshold value determination range of the light shielding region under the imaging of transmitted light.
4. The method of inspecting a multi-layer, multi-material photomask of claim 1, wherein in step S2-2 the system automatically focuses on areas of different heights of the photomask to ensure that layers of different heights are in the best focus plane when capturing images.
5. The method for inspecting multi-layer multi-material photomask according to claim 1, wherein in the step S2-1, the light intensity calibration is performed by selecting the area corresponding to the highest chrome layer height and the chrome-free quartz substrate area on the actual photomask as calibration points based on the height and material information in the three-dimensional data structure, and calibrating the minimum light flux value of the highest chrome layer area as a gray-scale lower limit and the maximum light flux value of the quartz substrate area as a gray-scale upper limit in the transmitted light and/or reflected light mode, thereby establishing a full-coverage detection gray-scale range.

Description

Inspection method of multilayer multi-material photomask Technical Field The invention relates to the technical field of semiconductor lithography, in particular to a method for inspecting a multi-layer multi-material photomask. Background Photomasks are critical features in the lithographic process that serve as templates for patterning semiconductor wafers. With the continued pursuit of moore's law and the advent of new device architectures (e.g., three-dimensional integrated circuits, microelectromechanical systems, and advanced packaging), photomask technology is also becoming increasingly complex. These advanced photomasks are no longer composed of simple planar patterns of a single material. Instead, they incorporate three-dimensional topologies of different heights on a single substrate, and employ multiple materials (e.g., chromium layers of different thicknesses and types) to achieve specific optical and performance goals. In the field of photomask detection, no experience and precedent can be referred to for the product, and due to the parameter limitation of a detection machine, focusing and light calibration of each material and each height are required to be carried out, so that the type of the material and the corresponding light signal value are confirmed. The product can not be clearly imaged in the whole domain when a single focal plane is used in a detection machine, and the problem that the optimal signal to noise ratio of all areas can not be obtained simultaneously due to single detection parameters caused by the difference of optical characteristics of materials can not be solved, so that whether defects exist on the product can not be identified. The technical problems existing in the prior art are as follows: 1. Limited focal depth and defocus problems the focal depth of conventional optical inspection systems is limited. When inspecting masks with significant height drops, it is not possible to have all structures remain in a clear focal plane at the same time. 2. Material response non-uniformity problems different materials (e.g. thick, thin different chrome films) have unique optical properties. Thus, they produce different responses when interacting with a given test wavelength and illumination condition. 3. Signal crosstalk and spurious defects problems signals from adjacent or underlying structures may interfere when attempting to inspect a particular layer or level. This interference manifests itself as optical crosstalk, complicating image analysis. Disclosure of Invention Therefore, the invention aims to provide a method for inspecting a multilayer multi-material photomask, which can effectively adapt to the height difference and the material optical characteristic difference of the surface of the photomask, improve imaging quality and signal-to-noise ratio, reduce false defect signals and reliably identify real defects. In order to solve the technical problems, the invention provides a method for inspecting a multi-layer multi-material photomask, which comprises the following steps: s1, constructing a checking database: s1-1, establishing a three-dimensional data architecture representing the material and the height attribute of the corresponding position of a photomask according to the design graph, the material distribution and different process steps of the photomask through data processing; S1-2, acquiring multi-layer exposure data for constructing the photomask, performing Boolean logic operation on the multi-layer exposure data based on the logic of the three-dimensional data architecture, mapping the three-dimensional features with different heights onto a two-dimensional plane, and finally generating a two-dimensional design layout database only comprising the features of a light transmission area and a light shielding area; s2, light calibration and inspection: S2-1, calibrating light intensity, namely selecting a region corresponding to the maximum light shielding layer height and a light-transmitting substrate region without a light shielding material on an actual photomask as calibration points based on the height and material information in the three-dimensional data architecture, calibrating a minimum light flux value of the maximum light shielding layer region as a gray scale lower limit and calibrating a maximum light flux value of the light-transmitting substrate region as a gray scale upper limit in a transmission light mode, so as to establish a full-coverage detection gray scale range; S2-2, performing Die-to-Database defect detection, namely performing image acquisition on an actual photomask by using transmitted light, and performing Die-to-Database comparison detection on an actually acquired image and a two-dimensional design layout Database generated in the step S1-2 by using a gray scale range established in the step S2-1 so that image signals of all other light shielding material areas lower than the maximum light shielding layer height are contai