Ultraviolet heterogeneous material optical filter for semiconductor detection

Abstract

The invention belongs to the field of optical filters, and particularly relates to an ultraviolet heterogeneous material optical filter for semiconductor detection, which is composed of a substrate and a basic film system plated on the substrate, and the structure of the basic film system is Sk (bHaLHaLbHcL) nA, wherein S is a glass substrate, A is air, H is a high-refractive-index material, L is a low-refractive-index material, k is a wavelength coefficient, a, b and c are matching coefficients, spectral passband ripples are adjusted through the matching coefficients, and n is the total circulation number of the film system to determine the gradient and cut-off depth of the film system. The method is simple and easy to implement, the influence of the ultraviolet heterogeneous material on the spectral characteristics can be effectively eliminated, and the spectral pattern is ensured.

Description

Technical Field

[0001] The invention belongs to the field of optical filters, and in particular relates to an ultraviolet inhomogeneous material filter for semiconductor detection. Background Art

[0002] In optical detection systems, filters mainly play the role of screening specific bands of light and filtering out interfering light signals in other bands. With the continuous development of DUV (deep ultraviolet) and EUV (extreme ultraviolet) lithography technology, semiconductor integrated circuit process nodes are constantly upgraded, the physical scale of corresponding integrated circuit devices is reduced, and the scale of defects that need to be detected is also continuously reduced, which also puts higher requirements on the spatial resolution accuracy of semiconductor detection technology. The most effective way to improve the detection resolution is to use a shorter wavelength light source. The wavelength of the light source used by the current advanced detection and measurement equipment has reached the DUV band, which can stably detect wafer defects less than 14nm. As the light source band comes to the ultraviolet region, especially the DUV and EUV bands, the available coating materials are extremely limited, and most materials are inhomogeneous materials after coating, that is, the refractive index is non-uniform, such as HfO2, Al2O3, LaF3, etc. Refractive index non-uniformity can lead to deterioration of the spectral characteristics of the filter (such as the half-wave hole of the regular film short-wave pass filter and the passband ripple of the depth-optimized filter). Therefore, it is urgent to develop a design method for ultraviolet non-homogeneous material filters for semiconductor detection that can improve the spectral characteristics. Summary of the invention

[0003] The present invention aims to overcome the shortcomings of the prior art and provide a method which is simple and easy to implement, can effectively eliminate the influence of ultraviolet inhomogeneous materials on the deterioration of spectral characteristics, and ensure the spectral spectrum of ultraviolet inhomogeneous material filters for semiconductor detection.

[0004] To solve the above technical problems, the present invention is achieved as follows:

[0005] The ultraviolet non-homogeneous material filter for semiconductor detection is composed of a substrate and a basic film system coated thereon, and the structure of the basic film system is:

[0006] S|k(bHaLHaLbHcL)^n|A; where: S is the glass substrate, A is air, H is the high refractive index material, L is the low refractive index material, k is the wavelength coefficient, a, b, c are matching coefficients, and the spectral passband ripple is adjusted by the matching coefficient. n is the total number of cycles of the film system, which determines the steepness and cutoff depth of the film system. Adjust the wavelength position of the wavelength coefficient k.

[0007] Furthermore, the thickness of H and L are both film layers with an optical thickness of λ0 / 4.

[0008] Furthermore, the H is made of HfO2, Al2O3 or LaF3 optical thin film material; and the L is made of SiO2 optical thin film material.

[0009] Furthermore, the value range of a and b is 0.1-0.3; the value range of c is 0.2-0.6.

[0010] As the wavelength of the light source reaches the ultraviolet region, the available coating materials are extremely limited, and most materials are non-homogeneous after coating, that is, the refractive index is non-uniform. The non-uniformity of the refractive index will lead to the deterioration of the spectral characteristics of the filter, such as: the half-wave hole of the regular film short-wave filter and the passband ripple of the depth-optimized filter. The present invention can improve this phenomenon. The present invention has the following characteristics:

[0011] 1. It can effectively eliminate the influence of ultraviolet non-homogeneous materials on spectral characteristics.

[0012] 2. After the film system is deeply optimized, the spectral spectrum can still be guaranteed.

[0013] 3. The method is simple and easy, can be completed using Macleod film design software, and has high preparability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. The protection scope of the present invention is not limited to the following description.

[0015] Figure 1 It is the structural diagram of the membrane system of the present invention;

[0016] Figure 2 This is a spectrum curve diagram of the conventional film structure of the present invention;

[0017] Figure 3 This is a spectrum curve diagram of the conventional film structure HfO2 with inhomogeneous simulation plating;

[0018] Figure 4 It is a graph showing the film structure of the present invention and a simulated actual plating spectrum curve. DETAILED DESCRIPTION

[0019] As shown in the figure, the ultraviolet inhomogeneous material filter for semiconductor detection is composed of a substrate and a basic film system coated thereon. The structure of the basic film system is:

[0020] S|k(bHaLHaLbHcL)^n|A; wherein: S is a glass substrate, A is air, H is a high refractive index material, L is a low refractive index material, k is a wavelength coefficient, a, b, c are matching coefficients, and the spectral passband ripples are adjusted by the matching coefficients. n is the total number of cycles of the film system, which determines the steepness and cutoff depth of the film system. The thickness of H and L are both film layers with an optical thickness of λ0 / 4. H is made of HfO2, Al2O3 or LaF3 optical thin film material; L is made of SiO2 optical thin film material. The matching coefficients a, b, and c of the present invention have a and b values ​​ranging from 0.1 to 0.3; c values ​​ranging from 0.2 to 0.6. For inhomogeneous materials in the film structure, the degree of inhomogeneity of the material refractive index δ is brought into the film design software.

[0021] Taking the spectral requirements: light incident at 0°, UV short-wave filter; T>90%@250~275nm; T<0.1%@280~520nm as an example, 4 conventional film structures (0.5LH0.5L)^n are connected in series, and the designed spectral curve is as follows Figure 2 Since HfO2 has a non-uniform refractive index during the actual coating process, this film system is used to simulate the actual coating results. Figure 3 .

[0022] According to the method of the present invention, the first three membrane stacks are connected in series using a conventional membrane system structure (0.5LH0.5L)^n, and the membrane stack near the half-wave hole is connected using a patented membrane system basic structure (bHaLHaLbHcL)^n; high and low materials H: HfO2; L: SiO2 are selected; initial matching coefficients a, b, c are given, a = 0.15; b = 0.17; c = 0.36. According to the cutoff depth, the appropriate number of cycles m = 13 is given;

[0023] The final initial membrane stack is:

[0024] (0.5LH0.5L) 13 1.2(0.5LH0.5L) 13 1.4(0.5LH0.5L) 13 1.62(0.17H0.15LH0.15L0.17H0.36L) 13

[0025] The target value was set using Macleod film design software, and the HfO2 refractive index non-uniformity degree δ = -0.07 was input into the software. The Conjugate and Optimac combined optimization methods were used to obtain the final film system based on the actual calculation results. The thickness distribution of each layer in the design is shown in Table 1, and the design curve is shown in Figure 4 .

[0026] Table 1: Thickness distribution of each layer

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[0030]

[0031]

[0032]

[0033] It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the protection scope of the present invention.

Claims

1. An ultraviolet inhomogeneous material filter for semiconductor detection, characterized in that: It consists of a substrate and a basic film system coated thereon, and the structure of the basic film system is: S|k(bHaLHaLbHcL)^n|A; where: S is the glass substrate, A is air, H is the high refractive index material, L is the low refractive index material, k is the wavelength coefficient, a, b, c are the matching coefficients, and the spectral passband ripple is adjusted by the matching coefficient. n is the total number of cycles of the film system, which determines the steepness and cutoff depth of the film system.

2. The ultraviolet inhomogeneous material filter for semiconductor detection according to claim 1, characterized in that: The thickness of H and L are both film layers with an optical thickness of λ0 / 4.

3. The ultraviolet inhomogeneous material filter for semiconductor detection according to claim 2, characterized in that: The H is made of HfO2, Al2O3 or LaF3 optical thin film material; the L is made of SiO2 optical thin film material.

4. The ultraviolet inhomogeneous material filter for semiconductor detection according to claim 3, characterized in that: The value range of a and b is 0.1~0.3; the value range of c is 0.2~0.6.

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