CN114624968A

CN114624968A - Photoetching exposure method

Info

Publication number: CN114624968A
Application number: CN202011445044.7A
Authority: CN
Inventors: 刘涛
Original assignee: Shanghai Industrial Utechnology Research Institute
Current assignee: Shanghai Industrial Utechnology Research Institute
Priority date: 2020-12-08
Filing date: 2020-12-08
Publication date: 2022-06-14

Abstract

The invention provides a photoetching exposure method, which comprises the following steps: 1) forming a photoresist layer on a substrate; 2) photoetching the photoresist layer by adopting a projection type exposure machine table to form an alignment pattern; 3) moving the substrate to a contact type exposure machine, aligning the photomask on the contact type exposure machine with the substrate based on the alignment pattern, and storing the coordinate of the photomask and the coordinate of the alignment pattern on the substrate; 4) and switching the contact type exposure machine table to a non-alignment mode, fixing and keeping the positions of the photomask and the photomask clamp unchanged through the coordinates of the photomask, fixing and keeping the position of the substrate chuck unchanged through the coordinates of the alignment pattern, and sequentially putting the wafer to be exposed into the substrate chuck for exposure treatment. The invention can effectively solve the problems of OVL offset and rotation offset of the front layer exposure of the contact exposure machine, so that the subsequent projection exposure provides higher possibility and precision, and the process capability is greatly improved.

Description

Photoetching exposure method

Technical Field

The invention belongs to the field of semiconductor integrated circuit manufacturing, and particularly relates to a photoetching exposure method.

Background

With the increasing integration of semiconductor chips, the feature size of transistors is continuously reduced to nanoscale, and the production process is more and more complicated. In production, the three-dimensional structure of various components is decomposed into dozens of layers of two-dimensional photoetching patterns. To achieve good device performance, the individual lithographic patterns must have not only precise feature line widths, but also ensure precise alignment registration (Overlay) between layers, the result of the inversion process, or the precision with which each successive pattern matches the previous layer, is referred to as registration. Overlay accuracy measurement is usually to place an Overlay accuracy measurement pattern (Overlay Mark) in each of the patterns of the upper and lower lithography layers, and to ensure alignment between the two lithography layers by measuring the deviation of the relative positions of the two Overlay patterns.

With the rapid development of integrated circuits, various requirements are becoming more and more complex. Although Micro Electro Mechanical Systems (MEMS) have been developed for decades, demand for MEMS device products such as gyroscopes, Radio Frequency (RF) MEMS devices, and MEMS microphones has been rising with rapid development of industries such as smart phones, automotive electronics, medical electronics, and internet of things. This is also inevitable in the manufacturing process of MEMS components and faces various challenges.

In the field of semiconductor MEMS manufacturing, exposure is divided into exposure modes such as contact (Aligner) exposure and projection (Stepper) exposure. The contact exposure machine (Aligner) is usually manual, the machine is simple, the wafer needs to be manually placed on the Chuck (Chuck) for operation, and the Chuck (Chuck) has mobility due to the requirement of alignment. The contact (Aligner) exposure tool exposes the Mask (Mask) without the tool automatically aligning the alignment marks (Mark) on the Mask to position the Mask (Mask) when the Mask is loaded, so the contact (Aligner) exposure tool has position uncertainty for the front layer (First) exposure. The projection type (Stepper) exposure photoetching machine has high automation degree, can automatically position a notch (notch) and the position of a wafer, and can also grab the coordinate on a Mask (Mask) so as to position the Mask (Mask), the exposure position of a front layer (First) can be relatively fixed in a very small deviation, and the wafer exposed by the projection type (Stepper) exposure front layer (First) can grab a positioning mark on a projection type (Stepper) exposure machine subsequently to automatically align.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a lithography exposure method for solving the problems of overlay accuracy (OVL) scanning directionality error and rotation deviation in the prior art when a contact (Aligner) exposure tool is used to work the front layer and a projection (Stepper) exposure tool is used to work the subsequent layer.

To achieve the above and other related objects, the present invention provides a lithography exposure method comprising the steps of: 1) providing a substrate, and forming a photoresist layer on the substrate; 2) carrying out photoetching treatment on the photoresist layer by adopting a projection type exposure machine table based on a preset alignment pattern so as to form an alignment pattern on a specific coordinate of the substrate; 3) moving the substrate to a contact exposure machine, aligning a photomask on the contact exposure machine with the substrate based on the alignment pattern, and storing the coordinate of the photomask and the coordinate of the alignment pattern on the substrate; 4) and switching the contact type exposure machine table to a non-alignment mode, fixing and keeping the positions of the photomask and the photomask clamp unchanged through the saved coordinates of the photomask, fixing and keeping the position of the substrate chuck unchanged through the coordinates of the alignment pattern, and sequentially putting the wafers to be exposed into the substrate chuck for exposure treatment.

Optionally, in step 2), the number of the alignment patterns is 1, and the alignment patterns are located at the center of the substrate.

Optionally, in step 2), the number of the alignment patterns is more than 2.

Optionally, the number of the alignment patterns is 2, and the alignment patterns are symmetrically distributed in the diameter direction of the substrate.

Optionally, the number of the alignment patterns is 4, and the alignment patterns are distributed on the substrate in a rectangular or trapezoidal manner.

Optionally, the shape of the alignment pattern is rectangular.

Optionally, the photomask used in exposing the wafer to be exposed in step 3) and the photomask used in exposing the wafer to be exposed in step 4) are the same photomask.

Optionally, the alignment pattern formed in step 2) is a pattern on a specific position on the photomask in step 3) and step 4).

Optionally, step 3) further comprises: and obtaining and storing the position information of the photomask clamp based on the coordinates of the photomask, and obtaining and storing the position information of the substrate chuck based on the coordinates of the alignment pattern.

Optionally, step 3) is followed by a step of storing the substrate with the alignment pattern for subsequent alignment.

As described above, the lithography exposure method of the present invention has the following advantageous effects:

the invention utilizes the characteristic that a projection (Stepper) exposure machine can freely position with high precision, and uses the photoetching process to manufacture the alignment pattern mark on the substrate, so that the substrate has alignment performance in a contact (Aligner) exposure machine, the substrate with the alignment pattern and the photomask are aligned, the position of a wafer chuck after alignment and the position of a photomask clamp are automatically stored, and the position of the contact exposure machine cannot have great deviation when the contact exposure machine uses the stored position to expose again.

Drawings

FIG. 1 is a flowchart illustrating a photolithography exposure method according to an embodiment of the present invention.

Fig. 2 to 6 are schematic structural diagrams of steps of a photolithography exposure method according to an embodiment of the present invention, in which fig. 4 is a schematic top-view structural diagram of the structure in fig. 3, and fig. 5 and 6 are schematic alignment pattern structures according to other embodiments.

Description of the element reference numerals

101 substrate

102 photoresist layer

103 alignment pattern

S11-S14

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

In the context of this application, a structure described as a first feature being "on" a second feature may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.

In the process of the MEMS manufacturing process, there are situations in which a contact (Aligner) exposure tool is used to operate the front layer and a projection (Stepper) exposure tool is used to operate the subsequent layer. Alignment precision (OVL) scanning directionality errors and rotational deviations may exist due to stage characteristics of the contact (Aligner) exposure stage prior to operation of the stage, resulting in deviations of alignment marks (marks) during alignment of the subsequent projection (Stepper) exposure stage. The adjustment is performed manually by skilled technicians on a wafer-by-wafer basis, and the adjustment range may be too wide to allow continued operation.

In order to solve the problem that overlay accuracy (OVL) scanning directionality error and rotational deviation exist when a contact (Aligner) exposure machine is used to operate a front layer and a projection (Stepper) exposure machine is used to operate a subsequent layer in the prior art, as shown in fig. 1 to 5, the present embodiment provides a lithography exposure method, which includes the following steps:

as shown in fig. 1 and fig. 2 to 3, step 1) S11 is first performed to provide a substrate 101, and a photoresist layer 102 is formed on the substrate 101.

The substrate 101 may be a silicon substrate, a photoresist layer 102 is formed on the substrate 101 through a spin coating process, and then the photoresist layer 102 is baked to cure the photoresist layer 102.

As shown in fig. 1 and fig. 4 to 6, step 2) is then performed to perform a photolithography process on the photoresist layer 102 using a projection (Stepper) exposure machine based on a predetermined alignment pattern 103, so as to form the alignment pattern 103 on the specific coordinates of the substrate 101.

Specifically, based on a projection (Stepper) exposure machine, a specific mask and an exposure menu are used to expose the photoresist layer 102, and then a developing process is performed to form an alignment pattern 103 on specific coordinates of the substrate 101, where the alignment pattern 103 is used for alignment by a subsequent projection (Stepper) exposure machine. Since the projection (Stepper) exposure tool has an automatic alignment function, the alignment pattern 103 with precise coordinates can be obtained on the substrate 101.

The number of the alignment patterns 103 may be 2 or more. In this embodiment, as shown in fig. 4, the number of the alignment patterns 103 is 2, and the alignment patterns are symmetrically distributed in the diameter direction of the substrate 101. By arranging the 2 alignment patterns 103 in the diameter direction, the wafer can be ensured not to generate side offset in the alignment process of a subsequent contact (Aligner) exposure machine, so that the alignment accuracy is improved.

In another embodiment, as shown in fig. 5, there may be 4 alignment patterns 103, and 4 alignment patterns 103 are distributed on the substrate 101 in a rectangular or trapezoidal shape.

In another embodiment, as shown in fig. 6, the number of the alignment patterns 103 is 1, and the alignment patterns 103 are located at the center of the substrate 101. This example is based on the wafer is the circular of strict centre of a circle symmetry, so only need make 1 counterpoint figure 103 in the centre of a circle of wafer, alright guarantee follow-up contact (Aligner) exposure machine platform counterpoint in-process wafer can not produce the skew, only need 1 counterpoint figure 103 just can satisfy the counterpoint demand, the structure is comparatively simple effective, can avoid because counterpoint figure 103 is too much to cause counterpoint figure 103 to damage easily or collapse and cause the problem of counterpoint failure, and, be favorable to follow-up substrate 101 as the storage of standard plate.

In this embodiment, the shape of the alignment patterns 103 is rectangular, which can reduce the requirement of the photolithography process compared with the alignment patterns 103 with other shapes.

As shown in fig. 1, step 3) S13 is performed next, the substrate 101 is moved to a contact exposure machine, the photomask on the contact exposure machine is aligned with the substrate 101 based on the alignment pattern 103, and the coordinates of the photomask and the coordinates of the alignment pattern 103 on the substrate 101 at this time are stored. Then, position information of the photomask holder is obtained and stored based on the coordinates of the photomask, and position information of the substrate chuck is obtained and stored based on the coordinates of the alignment pattern 103.

In this embodiment, after completing the alignment of the contact exposure tool, the substrate 101 with the alignment pattern 103 is saved for subsequent alignment.

In this embodiment, the alignment pattern 103 formed in step 2) is a pattern on a specific position on the photomask in step 3), so that the photomask only needs to be mounted on the photomask holder and then aligned, and after alignment, the photomask does not need to be replaced, and the photomask is directly used for exposure processing of a subsequent wafer, so as to avoid an alignment error caused when the photomask is replaced, thereby greatly improving the alignment accuracy.

As shown in fig. 1, step 4) S14 is finally performed, in which the contact exposure machine is switched to the non-alignment mode, the positions of the photomask and the photomask holder are fixed and kept unchanged by the stored coordinates of the photomask, the position of the substrate chuck is fixed and kept unchanged by the coordinates of the alignment pattern 103, and the wafers to be exposed are sequentially placed in the substrate chuck for exposure processing.

In this embodiment, the photomask used in exposing the wafer to be exposed in step 3) and the photomask used in exposing the wafer to be exposed in step 4) are the same photomask, and in this step, the photomask aligned in step 3) can be directly used for exposure processing of a subsequent wafer, so as to avoid alignment errors caused by replacement of the photomask, thereby greatly improving the alignment accuracy.

Of course, when the positions of the mask chuck and/or the substrate chuck are moved too much, the mask chuck and the substrate chuck can be repositioned by retrieving the position information of the mask chuck and the position information of the substrate chuck stored in step 3), so as to achieve accurate alignment.

Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A lithographic exposure method, characterized in that it comprises the steps of:

1) providing a substrate, and forming a photoresist layer on the substrate;

2) carrying out photoetching treatment on the photoresist layer by adopting a projection type exposure machine table based on a preset alignment pattern so as to form an alignment pattern on a specific coordinate of the substrate;

3) moving the substrate to a contact type exposure machine, aligning a photomask on the contact type exposure machine with the substrate based on the alignment pattern, and storing the coordinate of the photomask and the coordinate of the alignment pattern on the substrate;

4) and switching the contact type exposure machine table to a non-alignment mode, fixing and keeping the positions of the photomask and the photomask clamp unchanged through the saved coordinates of the photomask, fixing and keeping the position of the substrate chuck unchanged through the coordinates of the alignment pattern, and sequentially putting the wafers to be exposed into the substrate chuck for exposure treatment.

2. The lithographic exposure method of claim 1, wherein: in the step 2), the number of the alignment patterns is 1, and the alignment patterns are positioned at the center of the circle of the substrate.

3. The lithographic exposure method of claim 1, wherein: in the step 2), the number of the alignment patterns is more than 2.

4. The lithographic exposure method according to claim 3, characterized in that: the number of the alignment patterns is 2, and the alignment patterns are symmetrically distributed in the diameter direction of the substrate.

5. The lithographic exposure method according to claim 3, characterized in that: the number of the alignment patterns is 4, and the alignment patterns are distributed on the substrate in a rectangular or trapezoidal mode.

6. The lithographic exposure method of claim 1, wherein: the shape of the alignment pattern is rectangular.

7. The lithographic exposure method of claim 1, wherein: the photomask in the step 3) and the photomask used in the step 4) for exposing the wafer to be exposed are the same photomask.

8. The lithographic exposure method of claim 7, wherein: the alignment pattern formed in step 2) is a pattern on a specific position on the photomask in step 3) and step 4).

9. The lithographic exposure method of claim 1, wherein: step 3) also includes: and obtaining and storing the position information of the photomask clamp based on the coordinates of the photomask, and obtaining and storing the position information of the substrate chuck based on the coordinates of the alignment pattern.

10. The lithographic exposure method of claim 1, wherein: the step 3) is followed by a step of storing the substrate with the alignment pattern for subsequent alignment.