A method for adjusting the local thickness of photoresist

Abstract

The present invention provides a method for adjusting the local thickness of a photoresist. The method comprises: providing a semiconductor front layer structure, wherein the semiconductor front layer structure comprises Fin structures of different heights and a stacked structure covering the Fin structures of different heights; spin-coating a photoresist layer on the surface of the stacked structure, wherein the thickness of the photoresist layer in a first area of ​​the stacked structure surface is greater than the thickness of the photoresist layer in a second area; providing a photomask, wherein the photomask is formed with an auxiliary pattern for exposing the first area and a pattern for exposing the second area; the auxiliary pattern comprises a plurality of unit patterns distributed in an array; simultaneously exposing the first area and the second area of ​​the photoresist layer using the photomask, adjusting the exposure intensity so that after development of the first area, a portion of the surface of the first area is dissolved during development, the auxiliary pattern is not transferred to the photoresist layer in the first area, and the thickness of the photoresist layer in the first area is reduced after development; and simultaneously developing the second area so that the pattern is transferred to the photoresist layer in the second area.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, in particular to a method for adjusting the local thickness of a photoresist. Background Art

[0002] With the continuous advancement of process technology, fin transistor structures have become mainstream in processes below 14nm. Their 3D structure differs significantly from the 2D transistor structure used in previous (22nm) processes. Especially in the middle of the process, due to the presence of fins of varying heights, even with SOC (spin on carbon) or SOG (spin on glass) methods, the photoresist thickness in different graphic areas on the silicon wafer still varies significantly, posing a more severe challenge to photolithography technology.

[0003] Therefore, a new method needs to be proposed to solve the above problems. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for adjusting the local thickness of a photoresist, so as to solve the problem of uneven thickness of the photoresist layer on the stacked layer caused by Fin structures with different heights in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides a method for adjusting the local thickness of a photoresist, comprising at least:

[0006] Step 1: Providing a semiconductor front layer structure, the semiconductor front layer structure comprising a silicon substrate, an STI region located within the silicon substrate and isolating an active area, fin structures of different heights disposed on the silicon substrate within the active area; and a stacked structure covering the fin structures of different heights; the fin structures of different heights forming regions of different surface heights within the stacked structure;

[0007] Step 2: Spin-coating a photoresist layer on the surface of the stacked structure, wherein the photoresist layer is located in a first region where the surface of the stacked structure is high, and the thickness of the photoresist layer in the first region is H1; and the photoresist layer is located in a second region where the surface of the stacked structure is low, and the thickness of the photoresist layer in the second region is H2; and H1 is greater than H2;

[0008] Step 3: providing a photomask, wherein the photomask is formed with an auxiliary pattern for exposing the first region and a pattern for exposing the second region; the auxiliary pattern includes a plurality of unit patterns distributed in an array, and the number of rows and columns of the array is greater than 1;

[0009] Step 4: Use the photomask to simultaneously expose the first area and the second area of ​​the photoresist layer, and adjust the exposure intensity so that after the first area is developed, part of the surface thereof is dissolved with the development, and the auxiliary pattern is not transferred to the photoresist layer of the first area. After development, the thickness of the photoresist layer of the first area is H2; at the same time, after the second area is developed, the pattern is transferred to the photoresist layer of the second area.

[0010] Preferably, the stacked structure in step 1 includes NDC2, SiO2, NDC, NF, and TiN stacked in sequence from bottom to top on a silicon substrate.

[0011] Preferably, the unit pattern in step three is a strip-shaped rectangular structure.

[0012] Preferably, the spacing between the unit pattern and its adjacent unit pattern in step three is 40 nm.

[0013] Preferably, the CD of the unit pattern in step three is 30 nm.

[0014] Preferably, the photoresist in step 2 is a positive photoresist.

[0015] Preferably, in step 4, the thickness of the photoresist in the first region after development is equal to the thickness of the photoresist in the second region after development.

[0016] Preferably, the method is used for a process of a FinFET structure with a process node of 14 nm.

[0017] Preferably, the CD of the auxiliary pattern in step three is smaller than the minimum critical dimension in the design rule of the exposure layer.

[0018] As described above, the method for adjusting the local thickness of a photoresist according to the present invention has the following beneficial effects: By adding auxiliary patterns, the thickness of thick regions of the photoresist layer is reduced while allowing other exposure areas to be exposed normally to form a pattern. In thick regions of the photoresist layer, the overall light intensity and the CD of the auxiliary patterns are adjusted to partially dissolve the photoresist surface during development, thereby achieving the purpose of adjusting the local thickness of the photoresist. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown is a schematic cross-sectional structure diagram of a semiconductor front layer structure of the present invention;

[0020] Figure 2 A schematic diagram showing a photomask located on a semiconductor front layer structure according to the present invention;

[0021] Figure 3 Shown is a flow chart of the method for adjusting the local thickness of the photoresist in the present invention. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0023] See also Figures 1 to 3 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0024] The present invention provides a method for adjusting the local thickness of a photoresist, such as Figure 3 As shown, Figure 3 The flowchart of the method for adjusting the local thickness of the photoresist in the present invention is shown, and the method comprises at least the following steps:

[0025] Step 1: Provide a semiconductor front layer structure, the semiconductor front layer structure comprising a silicon substrate, an STI region located within the silicon substrate and isolating an active area, fin structures of different heights provided on the silicon substrate within the active area; and a stacked structure covering the fin structures of different heights; the fin structures of different heights enable the stacked structure to form regions with different surface heights; Figure 1 As shown, Figure 1 It is a schematic cross-sectional structural diagram of the semiconductor front layer structure of the present invention.

[0026] Furthermore, in the present invention, the stacking structure in step 1 of this embodiment includes NDC2, SiO2, NDC, NF, and TiN stacked in sequence from bottom to top on a silicon substrate.

[0027] like Figure 1 As shown, in step 1, a semiconductor front layer structure is provided, wherein the semiconductor front layer structure includes a silicon substrate 01, an STI region located in the silicon substrate 01 and isolating the active area, a fin structure of different heights is provided on the silicon substrate in the active area; and a stacked structure 02 ( Figure 1 Fin structures of different heights make the stacked structure form areas with different surface heights, which is intuitive for subsequent display. Figure 1The stacked structures with different heights are not shown in the figure; the stacked structure 02 in step one of this embodiment includes NDC2, SiO2, NDC, NF, and TiN stacked in sequence from bottom to top on a silicon substrate.

[0028] Step 2: Spin-coating a photoresist layer on the surface of the stacked structure, wherein the photoresist layer is located in a first region where the surface of the stacked structure is high, and the thickness of the photoresist layer in the first region is H1; and the photoresist layer is located in a second region where the surface of the stacked structure is low, and the thickness of the photoresist layer in the second region is H2; and H1 is greater than H2;

[0029] Furthermore, in the present invention, the photoresist layer in step 2 of this embodiment is a positive photoresist.

[0030] like Figure 1 As shown, in step 2, a photoresist layer 03 is spin-coated on the surface of the stacked structure 02, and the area where the photoresist layer 03 is at a high height on the surface of the stacked structure 02 is the first area, and the thickness of the photoresist layer 03 in the first area is H1; the area where the photoresist layer 03 is at a low height on the surface of the stacked structure 02 is the second area, and the thickness of the photoresist layer in the second area is H2; and H1 is greater than H2; therefore, the height difference between the photoresist layers in the first area and the second area is H1-H2; the photoresist layer in step 2 of this embodiment is a positive photoresist, that is, after the positive photoresist is exposed, the exposed part is developed and dissolved.

[0031] Step 3: providing a photomask, wherein the photomask is formed with an auxiliary pattern for exposing the first region and a pattern for exposing the second region; the auxiliary pattern includes a plurality of unit patterns distributed in an array, and the number of rows and columns of the array is greater than 1;

[0032] Furthermore, in the present invention, the unit pattern in step three of this embodiment is a strip-shaped rectangular structure.

[0033] Furthermore, in the present invention, the spacing between the unit pattern and its adjacent unit pattern in step three of this embodiment is 40 nm.

[0034] Furthermore, in the present invention, the CD of the unit pattern in step three of this embodiment is 30 nm.

[0035] Furthermore, in the present invention, the CD of the auxiliary pattern in step three of this embodiment is smaller than the minimum critical dimension in the design rule of the exposure layer.

[0036] like Figure 2 As shown, Figure 2The schematic diagram of the photomask on the semiconductor front layer structure in the present invention is shown. The step three provides a photomask 05, on which is formed an auxiliary pattern 04 for exposing the first area and a pattern for exposing the second area ( Figure 1 The auxiliary graphic 04 includes a plurality of unit graphics distributed in an array, and the number of rows and columns of the array is respectively greater than 1; that is, the unit graphics are arranged on the mask 05 in the form of rows and columns. The unit graphics in step three of this embodiment are strip-shaped rectangular structures. The spacing (trench) between the unit graphics in step three of this embodiment and its adjacent unit graphics is 40nm. The CD (critical dimension) of the unit graphics in step three of this embodiment is 30nm, that is, the pitch of the auxiliary graphics is 70nm. The CD of the auxiliary graphics 04 in step three of this embodiment is smaller than the minimum critical dimension in the design rule of the exposure layer. Therefore, the auxiliary graphics will not burst out on the photoresist due to exposure, and therefore the auxiliary graphics will not be transferred to the photoresist after development.

[0037] Step 4: Use the photomask to simultaneously expose the first area and the second area of ​​the photoresist layer, and adjust the exposure intensity so that after the first area is developed, part of the surface thereof is dissolved with the development, and the auxiliary pattern is not transferred to the photoresist layer of the first area. After development, the thickness of the photoresist layer of the first area is H2; at the same time, after the second area is developed, the pattern is transferred to the photoresist layer of the second area.

[0038] Furthermore, in the present invention, in step 4 of this embodiment, the thickness of the photoresist in the first region after development is equal to the thickness of the photoresist in the second region after development.

[0039] The method is used for a process of a FinFET structure with a process node of 14nm.

[0040] like Figure 2 As shown, in step 4, the first area and the second area of ​​the photoresist layer are exposed simultaneously by using the mask 05, and the exposure intensity is adjusted. The appropriate exposure intensity can make the first area develop and the surface of the photoresist layer in the area dissolve with the development, and the auxiliary pattern is not transferred to the photoresist layer in the first area. After development, the thickness of the photoresist layer in the first area is H2; at the same time, after the second area is developed, the pattern is transferred to the photoresist layer in the second area, forming a Figure 2 The photoresist pattern 06 in FIG. Figure 2 As shown, in step 4 of this embodiment, the thickness of the photoresist in the first region after development is equal to the thickness of the photoresist in the second region after development.

[0041] In summary, the present invention reduces the thickness of thick photoresist layers by adding auxiliary patterns, while allowing other exposed areas to form patterns normally. In thicker regions, the overall light intensity and the CD of the auxiliary patterns are adjusted to partially dissolve the photoresist surface during development, thereby achieving the goal of adjusting the local photoresist thickness. Therefore, the present invention effectively overcomes the shortcomings of the prior art and has high industrial applicability.

[0042] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may 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 one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for adjusting the local thickness of a photoresist, characterized in that: At least: Step 1: Providing a semiconductor front layer structure, the semiconductor front layer structure comprising a silicon substrate, an STI region located within the silicon substrate and isolating an active area, fin structures of different heights disposed on the silicon substrate within the active area; and a stacked structure covering the fin structures of different heights; the fin structures of different heights forming regions of different surface heights within the stacked structure; Step 2: Spin-coating a photoresist layer on the surface of the stacked structure, wherein the photoresist layer is located in a first region where the surface of the stacked structure is high, and the thickness of the photoresist layer in the first region is H1; and the photoresist layer is located in a second region where the surface of the stacked structure is low, and the thickness of the photoresist layer in the second region is H2; and H1 is greater than H2; Step 3: providing a photomask, wherein the photomask is formed with an auxiliary pattern for exposing the first region and a pattern for exposing the second region; the auxiliary pattern includes a plurality of unit patterns distributed in an array, and the number of rows and columns of the array is greater than 1; Step 4: Use the photomask to simultaneously expose the first area and the second area of ​​the photoresist layer, and adjust the exposure intensity so that after the first area is developed, part of the surface thereof is dissolved with the development, and the auxiliary pattern is not transferred to the photoresist layer of the first area. After development, the thickness of the photoresist layer of the first area is H2; at the same time, after the second area is developed, the pattern is transferred to the photoresist layer of the second area.

2. The method for adjusting the local thickness of the photoresist according to claim 1, wherein: The stacked structure in step 1 includes NDC2, SiO2, NDC, NF, and TiN stacked in sequence from bottom to top on a silicon substrate.

3. The method for adjusting the local thickness of the photoresist according to claim 1, wherein: The unit pattern in step three is a strip-shaped rectangular structure.

4. The method for adjusting the local thickness of the photoresist according to claim 1, wherein: The spacing between the unit pattern and its adjacent unit pattern in step 3 is 40 nm.

5. The method for adjusting the local thickness of the photoresist according to claim 3, wherein: The CD of the unit pattern in step 3 is 30 nm.

6. The method for adjusting the local thickness of the photoresist according to claim 1, wherein: The photoresist layer in step 2 is a positive photoresist.

7. The method for adjusting the local thickness of the photoresist according to claim 6, wherein: In step 4, the thickness of the photoresist in the first region after development is equal to the thickness of the photoresist in the second region after development.

8. The method for adjusting the local thickness of the photoresist according to claim 1, wherein: The method is used for a process of a FinFET structure with a process node of 14nm.

9. The method for adjusting the local thickness of the photoresist according to claim 1, wherein: The CD of the auxiliary pattern in step 3 is smaller than the minimum critical dimension in the design rule of the exposure layer.

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