Photoetching exposure method

Abstract

The invention relates to the technical field of semiconductor integrated circuit manufacturing, in particular to a photoetching exposure method. Comprising the following steps: providing a semiconductor wafer, and forming a photoresist layer on the surface of the semiconductor wafer; determining a central exposure area of the semiconductor wafer; acquiring a fluctuation map of the photoresist layer in the central exposure area; based on the fluctuation map of the photoresist layer in the central exposure area, determining a symmetric central axis of the photoresist layer in the central exposure area; determining parts, which are centrosymmetric about the symmetric central axis, in the central exposure area as a first fluctuating part and a second fluctuating part; respectively determining optimal focusing planes of the first fluctuating part and the second fluctuating part; performing exposure operation on the photoresist layer at the position of the first fluctuating part by using the optimal focusing plane of the first fluctuating part; and performing exposure operation on the photoresist layer at the position of the second fluctuating part by using the optimal focusing plane of the second fluctuating part.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor integrated circuit manufacturing, and in particular to a photolithography exposure method. Background Art

[0002] In the semiconductor manufacturing process, photolithography and etching processes are widely used. The photolithography process mainly includes coating a photoresist layer, exposing and developing the photoresist layer to pattern the photoresist layer.

[0003] However, the substrate of the photolithography wafer may be flat or uneven. For the wafer with pattern formed by photolithography, the height difference of the wafer surface after coating the photoresist layer is caused by the unevenness of the wafer, and the subsequent exposure operation is prone to defocusing, which is not conducive to the uniformity of the key dimensions of the device. Summary of the invention

[0004] The present application provides a photolithography exposure method, which can solve the problem of exposure defocusing caused by the unevenness of the chip surface in the related art.

[0005] In order to solve the technical problems involved in the background technology, the present application provides a photolithography exposure method, which comprises the following steps:

[0006] Providing a semiconductor wafer, wherein a photoresist layer is formed on the surface of the semiconductor wafer;

[0007] determining a central exposure area of ​​the semiconductor wafer;

[0008] Obtaining a fluctuation map of the photoresist layer in the central exposure area;

[0009] Determining a symmetric central axis of the photoresist layer in the central exposure area based on a fluctuation map of the photoresist layer in the central exposure area;

[0010] Determining a portion of the central exposure area that is centrally symmetric about the central axis of symmetry as a first undulating portion and a second undulating portion;

[0011] Determining optimal focus planes for the first undulating portion and the second undulating portion, respectively;

[0012] performing an exposure operation on the photoresist layer at the position of the first undulating portion at a best focusing plane of the first undulating portion;

[0013] An exposure operation is performed on the photoresist layer at the position of the second undulating portion at a best focusing plane of the second undulating portion.

[0014] Optionally, the step of respectively determining the best focus planes of the first undulating portion and the second undulating portion comprises:

[0015] Acquiring height information of the surface of the photoresist layer at each position in the first undulating portion;

[0016] Calculate an average height of the first undulating portion based on the height information;

[0017] The position corresponding to the average height of the first undulating portion is the best focusing plane of the first undulating portion;

[0018] The position where the best focusing plane of the first undulating portion is centrally symmetric with respect to the central axis of symmetry is determined as the best focusing plane of the second undulating portion.

[0019] Optionally, the step of respectively determining the best focus planes of the first undulating portion and the second undulating portion comprises:

[0020] Acquiring height information of the surface of the photoresist layer at each position in the first undulating portion;

[0021] Calculate an average height of the first undulating portion based on the height information;

[0022] The plane corresponding to the average height of the first undulating portion is the best focusing plane of the first undulating portion;

[0023] Acquiring height information of the surface of the photoresist layer at each position in the second undulating portion;

[0024] Calculate an average height of the second undulating portion based on the height information;

[0025] The plane corresponding to the average height of the second undulating portion is the best focusing plane of the second undulating portion.

[0026] Optionally, the step of performing an exposure operation on the photoresist layer at the position of the first undulating portion using the best focusing plane of the first undulating portion comprises:

[0027] The second undulating portion is shielded, and the photoresist layer at the position of the first undulating portion is exposed with the best focusing plane of the first undulating portion.

[0028] Optionally, the step of performing an exposure operation on the photoresist layer at the position of the second undulating portion using the best focusing plane of the second undulating portion comprises:

[0029] The first undulating portion is shielded, and the photoresist layer at the position of the second undulating portion is exposed with the best focusing plane of the second undulating portion.

[0030] Optionally, the step of determining the symmetry center axis of the photoresist layer in the central exposure area based on the undulation map of the photoresist layer in the central exposure area comprises:

[0031] Determining an undulation period of the photoresist layer in the central exposure area based on an undulation map of the photoresist layer in the central exposure area;

[0032] The symmetry center axis of the undulation period of the photoresist layer in the central exposure area is determined as the symmetry center axis of the photoresist layer in the central exposure area.

[0033] Optionally, after the first undulating portion and the second undulating portion are exposed, the critical dimensions of the photolithographic pattern are monitored to determine whether the critical dimensions of the photolithographic pattern meet the design rules. The technical solution of the present application has at least the following advantages: by grouping the photoresist layers in the central exposure area and exposing the respective parts according to the corresponding best focusing plane, the problem of exposure defocus due to the unevenness of the wafer surface can be reduced, and the uniformity of the critical dimensions of the pattern can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A schematic diagram of a photolithography exposure method provided in an embodiment of the present application is shown;

[0036] Figure 2 A schematic diagram showing a central exposure area of ​​a semiconductor wafer;

[0037] Figure 3 The undulation map of the photoresist layer in the central exposure area is shown;

[0038] Figure 4 A schematic diagram of a photoresist layer showing an undulation cycle;

[0039] Figure 5 A schematic diagram is shown after determining the best focusing planes of the first undulating part and the second undulating part. DETAILED DESCRIPTION

[0040] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0041] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0042] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0043] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0044] Figure 1 A schematic diagram of a photolithography exposure method according to an embodiment of the present application is shown. Figure 1 It can be seen that the photolithography exposure method includes the following steps:

[0045] Step S1: providing a semiconductor wafer, a photoresist layer being formed on the surface of the semiconductor wafer.

[0046] In the process of making the photoresist layer, the photoresist layer is baked after coating to solidify the photoresist layer. The coating and baking process will cause the photoresist layer in the central area of ​​the semiconductor wafer to have an undulating morphology.

[0047] Step S2: determining the central exposure area of ​​the semiconductor wafer.

[0048] When performing an exposure operation on a semiconductor wafer, the semiconductor wafer is scanned according to a specific exposure area. The central exposure area is an exposure area located at the center of the semiconductor wafer. The photoresist layer in the central exposure area of ​​the semiconductor wafer will have an undulating morphology.

[0049] Reference Figure 2 , which shows a schematic diagram of the central exposure area of ​​a semiconductor wafer, Figure 2 The red area in the central exposure area 110 of the semiconductor wafer 100 represents a recessed area. Figure 2 The green area of ​​the central exposure region 110 of the semiconductor wafer 100 represents a protruding area.

[0050] Step S3: obtaining a relief map of the photoresist layer in the central exposure area.

[0051] Reference Figure 3 , which shows the undulation map of the photoresist layer in the central exposure area. Figure 3 It includes X-axis, Y-axis and Z-axis, where X-axis represents Figure 2 The vertical direction in the Y axis represents Figure 2 The Z axis represents the height information.

[0052] from Figure 3 It can be seen that the central exposure area of ​​the undulation map is divided into multiple positions, each of which corresponds to height information.

[0053] Step S4: determining a symmetric central axis of the photoresist layer in the central exposure area based on a relief map of the photoresist layer in the central exposure area.

[0054] Exemplarily, step S4 may be implemented based on the following steps S41 to S42:

[0055] Step S41: determining the fluctuation period of the photoresist layer in the central exposure area based on the fluctuation map of the photoresist layer in the central exposure area.

[0056] Step S42: determining the symmetry center axis of the undulation period of the photoresist layer in the central exposure area as the symmetry center axis of the photoresist layer in the central exposure area.

[0057] Reference Figure 4 , which shows a schematic diagram of a photoresist layer with an undulating cycle, from Figure 4 The central axis of symmetry in this undulating cycle can be seen in the figure.

[0058] Step S5: Determine the portion of the central exposure area that is centrally symmetric about the central axis of symmetry as a first undulating portion and a second undulating portion.

[0059] Continue to refer to Figure 4 The photoresist layer of one undulation period includes a first undulation portion and a second undulation portion. The first undulation portion and the second undulation portion are centrally symmetric about a symmetry central axis in the undulation period.

[0060] Step S6: determining the best focusing planes of the first undulating portion and the second undulating portion respectively.

[0061] Exemplarily, step S6 may be implemented according to the following steps S161 to S164:

[0062] Step S161: Acquire height information of the surface of the photoresist layer at each position in the first undulating portion.

[0063] Step S162: Calculate the average height of the first undulating portion based on the height information.

[0064] Step S163: The position corresponding to the average height of the first undulating portion is the best focusing plane of the first undulating portion.

[0065] Step S164: Determine the position of the best focusing plane of the first undulating portion that is centrally symmetric about the central axis of symmetry as the best focusing plane of the second undulating portion.

[0066] In other embodiments, step S6 can also be implemented by the following process:

[0067] Step S261: Acquire height information of the surface of the photoresist layer at each position in the first undulating portion.

[0068] Step S262: Calculate the average height of the first undulating portion based on the height information.

[0069] Step S263: the plane corresponding to the average height of the first undulating portion is the best focusing plane of the first undulating portion.

[0070] Step S264: obtaining height information of the surface of the photoresist layer at each position in the second undulating portion.

[0071] Step S265: Calculate the average height of the second undulating portion based on the height information.

[0072] Step S266: The plane corresponding to the average height of the second undulating portion is the best focusing plane of the second undulating portion.

[0073] Reference Figure 5 , which shows a schematic diagram after determining the best focusing planes of the first undulating part and the second undulating part.

[0074] Step S7: performing an exposure operation on the photoresist layer at the position of the first undulating portion with the best focusing plane of the first undulating portion.

[0075] Exemplarily, the second undulating portion may be shielded, and the photoresist layer at the position of the first undulating portion may be exposed with the best focusing plane of the first undulating portion.

[0076] Step S8: performing an exposure operation on the photoresist layer at the position of the second undulating portion with the best focusing plane of the second undulating portion.

[0077] Exemplarily, the first undulating portion may be shielded, and the photoresist layer at the position of the second undulating portion may be exposed with the best focusing plane of the second undulating portion.

[0078] After the first undulating portion and the second undulating portion are exposed, the critical dimension of the photolithography pattern is monitored to determine whether the critical dimension of the photolithography pattern complies with the design rule.

[0079] This embodiment groups the photoresist layers in the central exposure area and exposes the respective parts in groups according to the corresponding optimal focusing planes, thereby reducing the problem of exposure defocus due to the unevenness of the chip surface and improving the uniformity of the key dimensions of the graphics.

[0080] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A photolithography exposure method, characterized in that: The photolithography exposure method comprises the following steps: Providing a semiconductor wafer, wherein a photoresist layer is formed on the surface of the semiconductor wafer; determining a central exposure area of ​​the semiconductor wafer; Obtaining a fluctuation map of the photoresist layer in the central exposure area; Determining a symmetric central axis of the photoresist layer in the central exposure area based on a fluctuation map of the photoresist layer in the central exposure area; Determining a portion of the central exposure area that is centrally symmetric about the central axis of symmetry as a first undulating portion and a second undulating portion; Determining optimal focus planes for the first undulating portion and the second undulating portion, respectively; performing an exposure operation on the photoresist layer at the position of the first undulating portion at a best focusing plane of the first undulating portion; An exposure operation is performed on the photoresist layer at the position of the second undulating portion at a best focusing plane of the second undulating portion.

2. The photolithography exposure method according to claim 1, wherein: The step of respectively determining the best focus planes of the first undulating portion and the second undulating portion comprises: Acquiring height information of the surface of the photoresist layer at each position in the first undulating portion; Calculate an average height of the first undulating portion based on the height information; The position corresponding to the average height of the first undulating portion is the best focusing plane of the first undulating portion; The position where the best focusing plane of the first undulating portion is centrally symmetric with respect to the central axis of symmetry is determined as the best focusing plane of the second undulating portion.

3. The photolithography exposure method according to claim 1, wherein: The step of respectively determining the best focus planes of the first undulating portion and the second undulating portion comprises: Acquiring height information of the surface of the photoresist layer at each position in the first undulating portion; Calculate an average height of the first undulating portion based on the height information; The plane corresponding to the average height of the first undulating portion is the best focusing plane of the first undulating portion; Acquiring height information of the surface of the photoresist layer at each position in the second undulating portion; Calculate an average height of the second undulating portion based on the height information; The plane corresponding to the average height of the second undulating portion is the best focusing plane of the second undulating portion.

4. The photolithography exposure method according to claim 1, wherein: The step of performing an exposure operation on the photoresist layer at the position of the first undulating portion using the best focusing plane of the first undulating portion comprises: The second undulating portion is shielded, and the photoresist layer at the position of the first undulating portion is exposed with the best focusing plane of the first undulating portion.

5. The photolithography exposure method according to claim 1, wherein: The step of performing an exposure operation on the photoresist layer at the position of the second undulating portion using the best focusing plane of the second undulating portion comprises: The first undulating portion is shielded, and the photoresist layer at the position of the second undulating portion is exposed with the best focusing plane of the second undulating portion.

6. The photolithography exposure method according to claim 1, wherein: The step of determining the symmetry center axis of the photoresist layer in the central exposure area based on the undulation map of the photoresist layer in the central exposure area comprises: Determining an undulation period of the photoresist layer in the central exposure area based on an undulation map of the photoresist layer in the central exposure area; The symmetry center axis of the undulation period of the photoresist layer in the central exposure area is determined as the symmetry center axis of the photoresist layer in the central exposure area.

7. The photolithography exposure method according to claim 1, wherein: After performing an exposure operation on the first undulating portion and the second undulating portion, a critical dimension of the photolithography pattern is monitored to determine whether the critical dimension of the photolithography pattern complies with a design rule.

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