Method for determining optimal exposure focal length difference
By obtaining the exposure data set of semiconductor products, the mapping relationship between the optimal exposure focal distance difference and the graphics spacing is obtained, which solves the problem of manual judgment of the optimal exposure focal distance difference and poor accuracy, and achieves faster and more accurate determination of the exposure focal distance.
Patent Information
- Application Number
- CN202510295158.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-12
- Publication Date
- 2025-05-30
AI Technical Summary
In the prior art, it takes a long time to judge the optimal exposure focal distance by manual means and has poor accuracy.
By obtaining exposure data sets of multiple types of semiconductor products, the mapping relationship between the optimal exposure focal distance difference and the graphic spacing is obtained, and the optimal exposure focal distance difference of the target type product is determined based on the mapping relationship and the graphic spacing of the target type product.
The problem of manually determining the optimal exposure focal distance for each product takes a long time and poor accuracy is solved, and the optimal exposure focal distance difference is achieved faster and more accurately.
Smart Images
Figure CN120065641A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of semiconductor devices and integrated circuits, and particularly to a method for determining the optimal exposure focal length difference. Background Art
[0002] In the semiconductor integrated circuit manufacturing industry, in order to meet the high-energy implantation requirements of small areas, ultra-thick photoresist can be used in the lithography process to expose small-sized patterns. This process is commonly used in the manufacturing process of pixel units of complementary metal oxide semiconductor contact image sensors (CIS). For the above-mentioned exposure with a high aspect ratio, a double-exposure process is usually adopted to achieve it.
[0003] For the double-exposure process, there is a focal length difference (focus offset) between the first exposure and the second exposure. The magnitude of the focal length difference is an important parameter for measuring the process level, which directly affects the profile of the photoresist after exposure, and thus affects the device performance. In view of this, in related technologies, workers will collect focus depth-exposure energy-matrix (FEM) critical dimension (CD) images and the profiles of sliced photoresists with different focal length differences to determine the optimal exposure focal length difference. However, using the manual method to determine the optimal exposure focal length difference takes a long time and has poor accuracy. Summary of the Invention
[0004] This application provides a method for determining the optimal exposure focal length difference, which can solve the problems that the manual method for determining the optimal exposure focal length difference in related technologies takes a long time and has poor accuracy. The method includes:
[0005] Obtain exposure data sets of multiple types of semiconductor products. The exposure data sets include the optimal exposure focal length difference and the pattern pitch of the corresponding type of products. The optimal exposure focal length difference is the difference in exposure focal lengths with the largest exposure process window in the double-exposure process;
[0006] Fit a mapping relationship according to the exposure data sets. The mapping relationship is used to characterize the relationship between the optimal exposure focal length difference and the pattern pitch;
[0007] Determine the optimal exposure focal length difference of the target type of product according to the mapping relationship and the pattern pitch of the target type of product.
[0008] In some embodiments, the mapping relationship between the optimal exposure focal length difference and the pattern pitch is a binomial relationship.
[0009] In some embodiments, obtaining the mapping relationship by fitting according to the exposure data set includes:
[0010] Fitting the parameters in the theoretical binomial relationship according to the theoretical binomial relationship and the exposure data set;
[0011] Adding the parameters to the theoretical binomial relationship to obtain the mapping relationship.
[0012] In some embodiments, the theoretical binomial relationship is derived from the Rayleigh formula and the depth of field formula.
[0013] In some embodiments, the theoretical binomial relationship is:
[0014]
[0015] where F / O is the optimal exposure focal length difference, pitch is the pattern pitch, λ is the exposure wavelength in the double exposure process, and k 1 、k 2 are constants.
[0016] The technical solution of the present application has at least the following advantages:
[0017] By obtaining the exposure data sets of various types of semiconductor products, fitting the mapping relationship between the optimal exposure focal length difference and the pattern pitch according to the exposure data sets, and then determining the optimal exposure focal length difference of the double exposure process of the product according to the mapping relationship and the pattern pitch of the target type product, the problem that it takes a long time and has poor accuracy to determine the optimal exposure focal length difference of each product manually is solved. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0019] Figure 1 is a flowchart of a method for determining the optimal exposure focal length difference provided by an exemplary embodiment of the present application;
[0020] Figure 2 is a schematic diagram of the imaging of the first exposure in the double exposure process;
[0021] Figure 3It is a schematic diagram of imaging in the second exposure of a double-exposure process. Detailed implementation manners
[0022] The technical solutions in the present application will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are only a part rather than all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application shall fall within the protection scope of the present application.
[0023] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is 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 thus should not be construed as a limitation to the present application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.
[0024] In the description of the present application, it should be noted that unless otherwise clearly defined 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 directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.
[0025] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
[0026] Refer to Figure 1 , which shows a flowchart of a method for determining the optimal exposure focal length difference provided by an exemplary embodiment of the present application. As Figure 1 shown, the method includes:
[0027] Step S1, obtaining exposure data sets of multiple types of semiconductor products. The exposure data set includes the optimal exposure focal length difference and the pattern pitch of the corresponding type of product. The optimal exposure focal length difference is the difference in exposure focal lengths with the largest exposure process window in a double-exposure process.
[0028] The semiconductor products involved in the embodiments of the present application are products that require two exposures during the manufacturing process. The type of semiconductor product can be set according to requirements. For example, different types can be different semiconductor devices, such as complementary metal oxide semiconductor (CMOS) devices, flash memory devices, complementary metal oxide semiconductor contact image sensor (CIS) devices, etc.; or, different types refer to the same semiconductor device but with different structures; or, different types refer to the same semiconductor device but with different manufacturing processes; or, different types refer to the same semiconductor device but with different CDs.
[0029] For any type of semiconductor product, the morphology of the photoresist after two exposures can be observed manually to obtain the optimal exposure focal length difference of the product of this type (for example, for any type of product, samples with different exposure focal length differences (the difference between the exposure focal length of the first exposure and the exposure focal length of the second exposure) can be obtained, and the exposure focal length corresponding to the sample with the largest process window is determined as the optimal exposure focal length difference). At the same time, the pitch of the pattern of the product is obtained, and an exposure data set for each type of semiconductor product is obtained.
[0030] Step S2: Fit a mapping relationship according to the exposure data set, and this mapping relationship is used to characterize the relationship between the optimal exposure focal length difference and the pitch.
[0031] Among them, the mapping relationship between the optimal exposure focal length difference and the pitch is a binomial relationship. Step S2 includes, but is not limited to: fitting the parameters in the theoretical binomial relationship according to the theoretical binomial relationship and the exposure data set, and adding the parameters to the theoretical binomial relationship to obtain this mapping relationship. Among them, the theoretical binomial relationship is derived from the Rayleigh formula and the depth of field formula.
[0032] Exemplarily, as Figure 2 and Figure 3 shown, the parallel light during the exposure process converges to the focus after passing through the lens of the exposure machine. After the exposure focal length of the first exposure is determined, the relationship between the optimal exposure focal length difference and the depth of field is:
[0033]
[0034] Among them, F / O is the optimal exposure focal length difference, DOF is the depth of field (depth of field, DOF), A 1 is the radius of the lens, A is the radius of the blur spot, and further:
[0035] F / O = KDOF(1.2)
[0036] Combined with Rayleigh's formula:
[0037] R = pitch / 2(1.3)
[0038]
[0039] where pitch is the pattern pitch, k 1 is parameter 1 (constant), λ is the exposure wavelength in the double-exposure process, R is the resolution of the exposure machine, NA is the numerical aperture of the exposure machine, and the depth-of-field formula:
[0040]
[0041] k 2 is parameter 2 (constant). Combining with formula (1.2), the theoretical binomial relationship is obtained:
[0042]
[0043] Furthermore, substituting the exposure data set into the theoretical binomial relationship (1.6), the parameters k 1 and k 2 in the theoretical binomial relationship are obtained by fitting, and then the mapping relationship is obtained.
[0044] Step S3: Determine the optimal exposure focal length difference of the target type product according to the mapping relationship and the pattern pitch of the target type product.
[0045] Exemplarily, after determining the mapping relationship and the pattern pitch of the target type product, the pattern pitch can be substituted into formula (1.6) to obtain the optimal exposure focal length difference of the target type product.
[0046] In summary, in the embodiments of the present application, by obtaining the exposure data sets of multiple types of semiconductor products, the mapping relationship between the optimal exposure focal length difference and the pattern pitch is obtained by fitting according to the exposure data sets, and then the optimal exposure focal length difference of the double-exposure process of the product is determined according to the mapping relationship and the pattern pitch of the target type product, which solves the problems that it takes a long time and has poor accuracy to determine the optimal exposure focal length difference of each product manually.
[0047] Obviously, the above embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill 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 enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.
Claims
1. A method for determining an optimal exposure focal length difference, characterized in that: include: Acquire exposure data groups of multiple types of semiconductor products, wherein the exposure data groups include optimal exposure focal length differences and pattern spacings of corresponding types of products, wherein the optimal exposure focal length difference is a difference in the maximum exposure focal length of an exposure process window in two exposure processes; A mapping relationship is obtained by fitting the exposure data group, wherein the mapping relationship is used to characterize the relationship between the optimal exposure focal length difference and the pattern spacing; The optimal exposure focal length difference of the target type product is determined according to the mapping relationship and the pattern spacing of the target type product.
2. The method according to claim 1, characterized in that The mapping relationship between the optimal exposure focal length difference and the pattern spacing is a binomial relationship.
3. The method according to claim 2, characterized in that The step of fitting the mapping relationship according to the exposure data group includes: According to the theoretical binomial relationship and the exposure data group, the parameters in the theoretical binomial relationship are obtained by fitting; The mapping relationship is obtained by adding the parameter to the theoretical binomial relationship.
4. The method according to claim 3, characterized in that The theoretical binomial relationship is derived based on the Rayleigh formula and the depth of field formula.
5. The method according to claim 4, characterized in that The theoretical binomial relationship is: Among them, F / O is the optimal exposure focal length difference, pitch is the pattern spacing, λ is the exposure wavelength in the two exposure processes, and k1 and k2 are constants.