METHOD OF FORMING OVERLAY MARK STRUCTURE
A method of forming an overlay mark structure includes the following steps. An insulation layer is formed on a substrate. A first overlay mark is formed in the insulation layer. A metal layer is formed on the substrate. The metal layer covers the insulation layer and the first overlay mark. The metal layer on the first overlay mark is removed. A top surface of the first overlay mark is lower than a top surface of the insulation layer after the step of removing the metal layer on the first overlay mark. A second overlay mark is formed on the metal layer. In the method of forming the overlay mark structure, the first overlay mark may not be covered by the metal layer for avoiding influences on related measurements, and the second overlay mark may be formed on the metal layer for avoiding related defects generated by the height difference.
The present invention relates to a method of forming an overlay mark structure, and more particularly, to a method of forming an overlay mark structure including two overlay marks.
2. Description of the Prior ArtThe manufacture of integrated circuits keeps improving as the related technologies progress. Many kinds of electric circuits may be integrated and formed on a single chip. The semiconductor process for manufacturing chips may include many steps, such as a deposition process for forming a thin film, a photoresist coating process, an exposure process, and a develop process for forming a patterned photoresist, and an etching process for patterning the thin film. In the exposure process, a photomask having a pattern to be formed has to be aligned with a base layer pattern on a wafer for transferring the pattern to a specific location on the wafer. The alignment condition maybe monitored by measuring the relative position between overlay marks of different layers for reducing the influence of process variations on the production yield. However, as the semiconductor process becomes complicated, the overlay masks of different layers may influence each other during the processes, and problems about the manufacturing and the measurements of the overlay marks are generated accordingly and have to be solved.
SUMMARY OF THE INVENTIONA method of forming an overlay mark structure is provided in the present invention. Apart of a metal layer is removed while another part of the metal layer remains for avoiding influences of the metal layer covering an overlay mark on related measurements, and another overlay mark may be formed on the metal layer for avoiding related defects generated by the height difference.
According to an embodiment of the present invention, a method of forming an overlay mark structure is provided. The method includes the following steps. Firstly, an insulation layer is formed on a substrate. A first overlay mark is formed in the insulation layer. A metal layer is formed on the substrate, and the metal layer covers the insulation layer and the first overlay mark. The metal layer on the first overlay mark is removed, and a top surface of the first overlay mark is lower than a top surface of the insulation layer after the step of removing the metal layer on the first overlay mark. A second overlay mark is formed on the metal layer.
In the method of forming the overlay mark structure according to the present invention, the metal layer is partially removed only. Therefore, the first overlay mark may not be covered by the metal layer, and the second overlay mark may be formed on the remaining metal layer. The influence of the metal layer covering the first overlay mark on the related measurements may be avoided by removing the metal layer on the first overlay mark. In addition, related defects generated by the height difference cause by the metal layer may be avoided by forming the second overlay mark on the metal layer.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
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In some embodiments, the first overlay mark OM1 may include an insulation material 31, and the material composition of the insulation material 31 maybe different from the material composition of the insulation layer 30. For example, when the insulation layer 30 is oxide, the insulation material 31 may include a material having an etching selectivity to the insulation layer 30, such as silicon nitride or silicon carbonitride (SiCN), but not limited thereto. In some embodiments, the first overlay mark OM1 may be formed by a conductive material according to some considerations. Additionally, the first overlay mark OM1 may include a plurality of first sections 31A buried in the insulation layer 30, and the method of forming the first sections 31A may include forming a plurality of trenches in the insulation layer 30 by an etching approach, forming the insulation material 31 on the insulation layer 30 and filling the trenches with the insulation material 31, and then performing a planarization process and/or an etching back process for removing the insulation material 31 outside the trenches and forming the first sections 31A in the insulation layer 30. Therefore, the first sections 31A may be formed by the insulation material 31, and the top surface of the insulation layer 30 and the top surface of the first overlay mark OM1 and the first sections 31A may be coplanar, but not limited thereto. Additionally, in some embodiments, other insulation layers, such as a native oxide layer and/or a silicon carbonitride layer, may be located between the insulation layer 30 and the substrate 10 and located between the first overlay mark OM1 and the substrate 10, but not limited thereto. In this embodiment, a main region (not shown in
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In some embodiments, an organic dielectric layer 51 and an anti-reflection layer 52 may be formed covering the metal layer 40, the cap layer 43, the first overlay mark OM1 and the insulation layer 30 after the step of removing the metal layer 40 on the first overlay mark OM1 and before the step of forming the second overlay mark OM2, and the second overlay mark OM2 may be formed on the anti-reflection layer 52, but not limited thereto. The organic dielectric layer 51 may include an organic distribution layer (ODL) or other suitable organic dielectric materials, and the anti-reflection layer 52 may include a silicon-containing hard mask bottom anti-reflecting coating (SHB) or other suitable anti-reflection materials. As shown in
The alignment condition of the exposure process for forming the second overlay mark OM2 maybe confirmed by measuring the relative positions of the first overlay mark OM1 and the second overlay mark OM2 with an optical measurement from top view, and the influence on the yield of the final product may be avoided by reworking when the alignment variation is out of specification. Therefore, by the manufacturing method of the present invention, the metal layer 40 on the first overlay mark OM1 maybe removed for avoiding the influence of the metal layer 40 on the optical measurements performed to the first overlay mark OM1. In addition, when the second overlay mark OM2 is formed by a photoresist material and the metal layer 40 on the overlay mark region R1 is removed completely, the photoresist material on the metal layer 40 above the main region will be higher than the photoresist material on the overlay mark region R1, a defocus issue may occur to the photoresist material on the overlay mark region R1 during the exposure process, and the second overlay mark OM2 cannot be formed successfully. Therefore, by the manufacturing method of the present invention, the second overlay mark OM2 may be formed on the metal layer 40 remaining on the overlay mark region R1, and related defects generated by the height difference cause by the metal layer 40 may be avoided accordingly.
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The following description will detail the different embodiments of the present invention. To simplify the description, identical components in each of the following embodiments are marked with identical symbols. For making it easier to understand the differences between the embodiments, the following description will detail the dissimilarities among different embodiments and the identical features will not be redundantly described.
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The method in this embodiment may further include forming a plurality of isolation structures 31B on the main region R2, and the isolation structures 31B may be formed in the insulation layer 30 on the main region R2. In some embodiments, the first overlay mark OM1 located on the overlay mark region R1 and the isolation structures 31B located on the main region R2 may be formed concurrently by the same process, but not limited thereto. The method of forming the isolation structures 31B may include forming a plurality of trenches in the insulation layer 30 on the main region R2 by etching, forming the insulation material 31 on the insulation layer 30 and filling the trenches with the insulation material 31, and then performing a planarization process and/or an etching back process for removing the insulation material 31 outside the trenches and forming the isolation structures 31B in the insulation layer 30. In other words, the first overlay mark OM1 and the isolation structure 31B may be formed concurrently by the same material and the same process, and the material composition of the first overlay mark OM1 maybe identical to the material composition of the isolation structures 31B accordingly.
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To summarize the above descriptions, in the method of forming the overlay mark structure according to the present invention, the metal layer on the overlay mark region may be partially removed only. Therefore, the first overlay mark may not be covered by the metal layer, and the second overlay mark may be formed on the metal layer remaining on the overlay mark region. The influence of the metal layer covering the first overlay mark on the related optical measurements may be avoided by removing the metal layer on the first overlay mark. In addition, related defects generated by the height difference cause by the metal layer may be avoided by forming the second overlay mark on the metal layer located on the overlay mark region, and the manufacturing yield may be improved accordingly.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Claims
1. A method of forming an overlay mark structure, comprising:
- forming an insulation layer on a substrate;
- forming a first overlay mark in the insulation layer;
- forming a metal layer on the substrate, wherein the metal layer covers the insulation layer and the first overlay mark;
- removing the metal layer on the first overlay mark, wherein a top surface of the first overlay mark is lower than a top surface of the insulation layer after the step of removing the metal layer on the first overlay mark; and
- forming a second overlay mark on the metal layer.
2. The method of forming the overlay mark structure according to claim 1, wherein a projection pattern of the first overlay mark in a thickness direction of the substrate surrounds at least a part of a projection pattern of the second overlay mark in the thickness direction of the substrate.
3. The method of forming the overlay mark structure according to claim 1, wherein a main region and an overlay mark region are defined on the substrate, and the first overlay mark and the second overlay mark are formed on the overlay mark region.
4. The method of forming the overlay mark structure according to claim 3, further comprising:
- forming isolation structures on the main region; and
- forming a storage node contact structure between two of the isolation structures adjacent to each other, wherein the first overlay mark and the isolation structures are formed concurrently by the same process.
5. The method of forming the overlay mark structure according to claim 4, wherein a material composition of the first overlay mark is identical to a material composition of the isolation structures.
6. The method of forming the overlay mark structure according to claim 5, wherein the first overlay mark comprises an insulation material.
7. The method of forming the overlay mark structure according to claim 4, wherein the metal layer is further formed on the storage node contact structure.
8. The method of forming the overlay mark structure according to claim 7, further comprising:
- forming a patterned mask layer on the metal layer on the main region, wherein the patterned mask layer and the second overlay mark are formed concurrently by the same process.
9. The method of forming the overlay mark structure according to claim 8, wherein a material composition of the second overlay mark is identical to a material composition of the patterned mask layer.
10. The method of forming the overlay mark structure according to claim 9, wherein the second overlay mark comprises a photoresist material.
11. The method of forming the overlay mark structure according to claim 8, further comprising:
- performing a patterning process to the metal layer on the main region with the patterned mask layer as a mask, wherein a least a part of the metal layer on the main region is patterned to be a storage node pad on the storage node contact structure.
12. The method of forming the overlay mark structure according to claim 1, further comprising:
- forming an anti-reflection layer covering the metal layer, the first overlay mark and the insulation layer after the step of removing the metal layer on the first overlay mark and before the step of forming the second overlay mark, wherein the second overlay mark is formed on the anti-reflection layer.
13. The method of forming the overlay mark structure according to claim 1, further comprising:
- forming a cap layer on the metal layer before the step of removing the metal layer on the first overlay mark, wherein a part of the cap layer overlaps the first overlay mark; and
- removing the cap layer above the first overlay mark before the step of forming the second overlay mark.
14. The method of forming the overlay mark structure according to claim 13, wherein a part of the cap layer is located between the second overlay mark and the metal layer in a thickness direction of the substrate.
Type: Application
Filed: Jul 31, 2018
Publication Date: Jan 9, 2020
Inventors: Zheng-Feng Chen (New Taipei City), Sho-Shen Lee (New Taipei City), En-Chiuan Liou (Tainan City), Hsiao-Lin Hsu (Yunlin County), Yi-Ting Chen (Tainan City), Lu-Wei Kuo (Yilan County)
Application Number: 16/049,826