Method for measuring a pattern signal with enhanced overlay accuracy

Abstract

The application provides a method for measuring a pattern signal of enhanced overlay precision, and the method comprises the following steps: providing a semiconductor structure, the semiconductor structure is formed with a front metal layer, and the front metal layer is formed with a front overlay mark; forming a high light absorption material layer above the front metal layer, and part of the high light absorption material layer is a grating structure; forming a via layer on the surface of the high light absorption material layer, and the via layer is formed with a via overlay mark, the alignment degree of the via overlay mark and the front overlay mark is used to determine the overlay precision between the via layer and the front metal layer; and the projection of the grating structure and the front overlay mark in the vertical direction has an overlapping area. The application solves the problem that the optical measurement signal of the front overlay mark is weak due to the existence of the high light absorption material, and the measurement of the overlay precision is seriously affected.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for enhancing the measurement signal of a pattern for overlay accuracy measurement. Background Technology

[0002] As the size of integrated circuit devices shrinks and the complexity of design and processes increases, the requirements for semiconductor manufacturing process control are also constantly increasing, thus requiring more precise measurements.

[0003] For photolithography, overlay accuracy is a very important process control parameter, especially for some critical layers, where the measurement and control of overlay have very high requirements.

[0004] Some materials with high light absorption can pose significant challenges to the measurement of overlay accuracy. For example, in LELE or back-end Meta-Via lithography processes, hard masks with high light absorption can strongly absorb the overlay measurement light source. In such cases, when measuring the overlay accuracy between the via layer and the preceding metal layer, it becomes impossible to obtain sufficient optical measurement signals, thus severely affecting the measurement accuracy of the overlay.

[0005] Currently, the common practice is to use an overlay mark windowing method, such as... Figure 1 As shown, etching a hard mask layer with high absorbency (i.e., a high-absorbency material layer) removes the hard mask layer located below the Mark region of the via layer, thereby increasing the optical signal intensity of the via layer to the preceding Metal layer. However, this method introduces a large open area of ​​the hard mask layer, which differs significantly from the actual pattern size within the cell, potentially causing defects in subsequent etching and polishing processes. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for enhancing the measurement signal of the overlay accuracy measurement pattern, which solves the problem that the presence of high absorbance materials makes the optical measurement signal of the previous overlay mark weak, thus seriously affecting the measurement of overlay accuracy.

[0007] To achieve the above and other related objectives, the present invention provides a method for enhancing the measurement signal of a pattern for overlay accuracy measurement, the method comprising:

[0008] A semiconductor structure is provided, wherein a front metal layer is formed on the semiconductor structure and a front overlay mark is formed on the front metal layer;

[0009] A high light-absorbing material layer is formed above the front metal layer, and a portion of the high light-absorbing material layer is a grating structure;

[0010] A via layer is formed on the surface of the high light-absorbing material layer, and the via layer has via overlay marks. The alignment degree between the via overlay marks and the previous overlay marks is used to determine the overlay accuracy between the via layer and the previous metal layer.

[0011] The grating structure and the projection of the previous layer overlay mark in the vertical direction have an overlapping area.

[0012] Optionally, the period of the grating structure is 100nm to 300nm, and the linewidth is 70nm to 100nm.

[0013] Optionally, the high light-absorbing material layer includes at least one of silicon oxide or silicon nitride.

[0014] Optionally, the high light-absorbing material layer is etched using an etching process to form the grating structure.

[0015] Optionally, the front layer overlay mark includes at least one front layer grating pattern group, and the front layer grating group includes a plurality of parallel first strip patterns; the through-hole overlay mark includes at least one through-hole grating pattern group, and the through-hole grating pattern group includes a plurality of parallel second strip patterns.

[0016] Optionally, the front layer overlay mark includes four front layer grating pattern groups, namely a first front layer grating pattern group, a second front layer grating pattern group, a third front layer grating pattern group, and a fourth front layer grating pattern group; the through-hole overlay mark includes four through-hole grating pattern groups, namely a first through-hole grating pattern group, a second through-hole grating pattern group, a third through-hole grating pattern group, and a fourth through-hole grating pattern group;

[0017] Wherein, the first front-layer grating pattern group and the first through-hole grating pattern group are arranged adjacently to form a rectangular first pattern, the second front-layer grating pattern group and the second through-hole grating pattern group are arranged adjacently to form a rectangular second pattern, the third front-layer grating pattern group and the third through-hole grating pattern group are arranged adjacently to form a rectangular third pattern, and the fourth front-layer grating pattern group and the fourth through-hole grating pattern group are arranged adjacently to form a rectangular fourth pattern;

[0018] The first, second, third, and fourth figures are arranged in a 2x2 matrix. In the first and third figures, the first and second strip figures extend along a first direction. In the second and fourth figures, the first and second strip figures extend along a second direction, and the first and second directions are orthogonal.

[0019] Optionally, the width of the first strip pattern is the same as the width of the second strip pattern.

[0020] Optionally, the semiconductor structure further includes a current metal layer, which is formed on the lower surface of the high light-absorbing material layer, above the previous metal layer, and with an interlayer dielectric layer between them.

[0021] Optionally, the metals of the front metal layer have a first gap-filling layer between them; the metals of the current metal layer have a second gap-filling layer between them.

[0022] Optionally, the front overlay mark is formed within the first gap filling layer.

[0023] Optionally, the materials of the first gap-filling layer and the second gap-filling layer include oxides.

[0024] As described above, the method for enhancing the overlay accuracy measurement signal of the present invention is to prepare a grating structure by fabricating a high light-absorbing material layer above the overlay mark of the previous metal layer, so that the required wavelength band has good light transmittance, thereby effectively increasing the measurement window of overlay accuracy and thus enhancing the process tolerance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of an existing Overlay Mark windowing method.

[0026] Figure 2 The flowchart shown is a method for measuring pattern measurement signals to enhance overlay accuracy according to the present invention.

[0027] Figure 3 The diagram shown is a cross-sectional view of the high light-absorbing material layer of the present invention after forming a grating structure.

[0028] Figure 4 The diagram shown is a schematic representation of the mask used for overlay markings according to the present invention.

[0029] Figure 5 The diagram shown is a schematic representation of the second graphic portion of the mask after the grating structure has been formed according to the present invention. Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] Please see Figures 1 to 5 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation, the shape, quantity and proportion of each component in the actual implementation can be arbitrarily changed, and the layout of the components may also be more complex.

[0032] like Figure 2 As shown, this embodiment provides a method for enhancing the measurement signal of a pattern for overlay accuracy measurement, the method comprising:

[0033] Step 1) Provide a semiconductor structure having a front metal layer formed thereon, and the front metal layer having a front overlay mark formed thereon;

[0034] Step 2) A high light-absorbing material layer is formed above the front metal layer, and a portion of the high light-absorbing material layer is a grating structure;

[0035] Step 3) A via layer is formed on the surface of the high light-absorbing material layer, and the via layer is formed with via overlay marks. The alignment degree between the via overlay marks and the previous overlay marks is used to determine the overlay accuracy between the via layer and the previous metal layer.

[0036] The grating structure and the projection of the previous layer overlay mark in the vertical direction have an overlapping area.

[0037] In this embodiment, the overlapping area between the projection of the grating structure and the previous layer overlay mark in the vertical direction indicates that the position of the grating structure is directly above the position of the previous layer overlay mark.

[0038] The method for enhancing the overlay accuracy measurement of graphic measurement signals provided in this embodiment will be described in detail below.

[0039] like Figure 3 As shown, in step 1), a semiconductor structure is provided, wherein a front metal layer is formed on the semiconductor structure and a front overlay mark is formed on the front metal layer.

[0040] Specifically, the semiconductor structure further includes a current metal layer, which is formed on the lower surface of the high light-absorbing material layer and above the previous metal layer, and an interlayer dielectric layer is formed between the current metal layer and the previous metal layer.

[0041] In this embodiment, the material of the front dielectric layer includes silicon oxide, which is deposited by plasma-enhanced chemical vapor deposition.

[0042] Specifically, the metals of the front metal layer have a first gap-filling layer between them; the metals of the current metal layer have a second gap-filling layer between them.

[0043] like Figure 3 As shown, in this embodiment, the metal in the front metal layer is not shown; instead, the first gap-filling layer between the metals and the front overlay mark formed within the first gap-filling layer are shown. Similarly, the metal in the current metal layer is also not shown; instead, the second gap-filling layer between the metals is shown.

[0044] Specifically, the front overlay mark is formed within the first gap filling layer.

[0045] As an example, the materials of the first gap-filling layer and the second gap-filling layer include oxides.

[0046] In step 2), a high light-absorbing material layer is formed above the front metal layer, and a portion of the high light-absorbing material layer is a grating structure.

[0047] Specifically, the period of the grating structure is 100nm to 300nm, and the linewidth is 70nm to 100nm.

[0048] Specifically, the high light-absorbing material layer includes at least one of silicon oxide or silicon nitride.

[0049] In this embodiment, the high light-absorbing material layer includes a silicon oxide layer and a silicon nitride layer, and the silicon nitride layer is formed on the surface of the silicon oxide layer.

[0050] Specifically, the high light-absorbing material layer is etched using an etching process to form the grating structure.

[0051] In this embodiment, by fabricating a high-absorbent material layer above the front overlay mark into a grating structure and rationally designing its pitch and linewidth (CD), it can have a better light transmittance in the required wavelength band. Furthermore, by selecting an appropriate measurement wavelength, the optical signal of the front overlay mark can be enhanced, thereby increasing the process tolerance.

[0052] In step 3), a through-hole layer is formed on the surface of the high light-absorbing material layer, and the through-hole layer is formed with through-hole overlay marks. The alignment degree between the through-hole overlay marks and the previous layer overlay marks is used to determine the overlay accuracy between the through-hole layer and the previous metal layer.

[0053] In this embodiment, the via layer includes a spin-coated filling layer, an anti-reflective layer, and a photoresist layer. The spin-coated filling layer fills the gaps in the grating structure and extends to the surface of the high-absorbency material layer. The anti-reflective layer is formed on the surface of the spin-coated filling layer, and the photoresist layer is formed on the surface of the anti-reflective layer. The via overlay mark is formed within the photoresist layer by processing the photoresist layer.

[0054] Specifically, the front layer overlay mark includes at least one front layer grating pattern group, and the front layer grating group includes multiple parallel first strip patterns; the through hole overlay mark includes at least one through hole grating pattern group, and the through hole grating pattern group includes multiple parallel second strip patterns.

[0055] More specifically, the front layer overlay mark includes four front layer grating pattern groups, namely the first front layer grating pattern group 11, the second front layer grating pattern group 12, the third front layer grating pattern group 13, and the fourth front layer grating pattern group 14; the through hole overlay mark includes four through hole grating pattern groups, namely the first through hole grating pattern group 21, the second through hole grating pattern group 22, the third through hole grating pattern group 23, and the fourth through hole grating pattern group 24;

[0056] Wherein, the first front-layer grating pattern group 11 and the first through-hole grating pattern group 21 are arranged adjacently to form a rectangular first pattern 10, the second front-layer grating pattern group 12 and the second through-hole grating pattern group 22 are arranged adjacently to form a rectangular second pattern 20, the third front-layer grating pattern group 13 and the third through-hole grating pattern group 23 are arranged adjacently to form a rectangular third pattern 30, and the fourth front-layer grating pattern group 14 and the fourth through-hole grating pattern group 24 are arranged adjacently to form a rectangular fourth pattern 40;

[0057] The first, second, third, and fourth figures are arranged in a 2x2 matrix. In the first figure 10 and the third figure 30, the first and second stripe figures extend along a first direction X; in the second figure 20 and the fourth figure 40, the first and second stripe figures extend along a second direction Y, and the first direction X and the second direction Y are orthogonal (e.g., ...). Figure 4 (As shown).

[0058] As an example, the width of the first strip is the same as the width of the second strip.

[0059] Figure 5 The image shows a photomask pattern of the front overlay mark and the grating structure. In this embodiment, the optical signal intensity is enhanced by forming the grating structure above the front overlay mark, thereby avoiding interference when measuring its overlay accuracy.

[0060] In summary, the method for enhancing the measurement signal of overlay accuracy in this invention, by fabricating a high-absorbent material layer above the overlay mark of the previous metal layer into a grating structure, allows for better light transmittance in the required wavelength band, thereby effectively increasing the measurement window for overlay accuracy and enhancing process tolerance. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0061] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for enhancing the measurement signal of a pattern for overlay accuracy measurement, characterized in that, The method includes: A semiconductor structure is provided, wherein a front metal layer is formed on the semiconductor structure and a front overlay mark is formed on the front metal layer; A high light-absorbing material layer is formed above the front metal layer, and a portion of the high light-absorbing material layer is a grating structure; A via layer is formed on the surface of the high light-absorbing material layer, and the via layer has via overlay marks. The alignment degree between the via overlay marks and the previous overlay marks is used to determine the overlay accuracy between the via layer and the previous metal layer. The grating structure and the projection of the previous layer overlay mark in the vertical direction have an overlapping area.

2. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 1, characterized in that, The period of the grating structure is 100nm to 300nm, and the linewidth is 70nm to 100nm.

3. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 1 or 2, characterized in that, The high light-absorbing material layer includes at least one of silicon oxide or silicon nitride.

4. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 3, characterized in that, The high light-absorbing material layer is etched using an etching process to form the grating structure.

5. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 1, characterized in that, The front layer overlay mark includes at least one front layer grating pattern group, and the front layer grating pattern group includes a plurality of parallel first strip patterns; the through hole overlay mark includes at least one through hole grating pattern group, and the through hole grating pattern group includes a plurality of parallel second strip patterns.

6. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 5, characterized in that, The front layer overlay mark includes four front layer grating pattern groups, namely the first front layer grating pattern group, the second front layer grating pattern group, the third front layer grating pattern group, and the fourth front layer grating pattern group; the through hole overlay mark includes four through hole grating pattern groups, namely the first through hole grating pattern group, the second through hole grating pattern group, the third through hole grating pattern group, and the fourth through hole grating pattern group. Wherein, the first front-layer grating pattern group and the first through-hole grating pattern group are arranged adjacently to form a rectangular first pattern, the second front-layer grating pattern group and the second through-hole grating pattern group are arranged adjacently to form a rectangular second pattern, the third front-layer grating pattern group and the third through-hole grating pattern group are arranged adjacently to form a rectangular third pattern, and the fourth front-layer grating pattern group and the fourth through-hole grating pattern group are arranged adjacently to form a rectangular fourth pattern; The first, second, third, and fourth figures are arranged in a 2x2 matrix. In the first and third figures, the first and second stripes extend along a first direction. In the second and fourth figures, the first and second stripes extend along a second direction, and the first and second directions are orthogonal.

7. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 6, characterized in that, The width of the first strip is the same as the width of the second strip.

8. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 1, characterized in that, The semiconductor structure further includes a current metal layer, which is formed on the lower surface of the high light-absorbing material layer and above the previous metal layer, and an interlayer dielectric layer is formed between the current metal layer and the previous metal layer.

9. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 8, characterized in that, The metals of the front metal layer have a first gap-filling layer between them; the metals of the current metal layer have a second gap-filling layer between them.

10. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 9, characterized in that, The front layer overlay mark is formed within the first gap filling layer.

11. The method for enhancing the measurement signal of a pattern for overlay accuracy measurement according to claim 10, characterized in that, The materials of the first gap filling layer and the second gap filling layer include oxides.

Images