A method for homogenizing light suitable for use in an illumination system of a photolithography machine

Abstract

The application discloses a light homogenizing method suitable for an illumination system of a photoetching machine and belongs to the technical field of the illumination system of the photoetching machine, which comprises the following steps: firstly, a model of the correction plate is established by using lighttools, and a round dot is plated on the surface of the correction plate; the radius, thickness, X-direction interval and Y-direction interval of the round dot are set; then, light source properties in the lighttools are set, and the non-uniform light is made to pass through the correction plate to reach a receiver on a receiving surface; then, the intervals of the round dot in the X and Y directions are added as optimization variables respectively, a grid evaluation function is added on the receiver, and changes in the grid data are set as a function of scaling target based on total power to adjust light homogeneity; subsequently, the lighttools optimizes the currently established model to obtain optimized X and Y direction intervals; the method provided by the application has wider applicability, can improve light homogeneity to more than 90%, and can also avoid excessive loss of light intensity, so that the stability of photoetching is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithography machine illumination system, and particularly relates to a light homogenization method suitable for a lithography machine illumination system. BACKGROUND

[0002] In the lithography machine illumination system, uniform illumination is an important technology to ensure that the line width of the processed line is uniform. In order to ensure that the line width meets the design index of the lithography machine, uniform light elements such as an integrating rod, a diffractive optical element, a microlens array, etc. are usually applied to the lithography machine illumination system. In addition to the above-mentioned common uniform light elements, there are static gray scale filtering method and dynamic gray scale filtering method. The static gray scale filtering method improves the light uniformity by plating a layer of optical film with a specific transmittance distribution on the correction plate, and the dynamic gray scale filtering method improves the light uniformity by changing the relative position of two correction plates plated with opposite transmittance distribution to obtain different transmittance distribution.

[0003] The integrating rod has the disadvantages of limiting the maximum aperture angle of illumination, and reducing the energy utilization rate due to multiple reflections of the light beam in the integrating rod; the diffractive optical element is limited by the diffraction effect, and the energy utilization rate is reduced; the static gray scale filtering method can only be used for illumination light field with specific light intensity distribution; and the dynamic gray scale filtering method has relatively limited correction ability and range.

[0004] The integral uniformity of the illumination light field is a key index, because the exposure dose of any view field point on the silicon wafer is the integral energy of the illumination light field in the scanning direction, and the integral uniformity of the illumination directly affects the feature size uniformity of the lithography machine.

[0005] When any lithography machine is used beyond the service life (i.e. the components are used beyond the service life), the transmittance of the lenses and the film layers in the illumination system will deteriorate due to long-time irradiation, which seriously affects the integral uniformity of the illumination light field. For example, the light beam of the laser or mercury lamp light source in the illumination system is focused from the emitter through an ellipsoidal bowl, and then uniformly homogenized through a microlens array; however, due to the aging of the optical components and the film layers, the uniformity of the light beam homogenized through the microlens array cannot meet the requirements of the process production, and the light intensity of each area on the exposure map pattern of the lithography machine is uneven. In order to solve the above-mentioned problems, the present application provides a light homogenization method suitable for a lithography machine illumination system. SUMMARY

[0006] The present application aims to provide a light homogenization method suitable for a lithography machine illumination system to solve the problems in the background art.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0008] A light uniformity method suitable for an illumination system of a photolithography machine, comprising the following steps:

[0009] Firstly, a model of the compensation plate is established by lighttools, and the surface is plated with dots by means of three-dimensional texture;

[0010] Secondly, the radius and thickness of the dots are set, and the X-direction interval and Y-direction interval are set respectively;

[0011] Then, the light source properties in lighttools are set, the light source is spatial distribution, the light uniformity is 60%, and the non-uniform light reaches the receiver on the receiving surface through the compensation plate;

[0012] Then, the intervals of the dots in the XY two directions are added as optimization variables respectively, and the grid evaluation function is added on the receiver, and the change in the grid data is set as the function of the scaling target based on the total power to adjust the light uniformity;

[0013] Then, lighttools optimizes the currently established model to obtain the optimized XY-direction interval.

[0014] As a further scheme of the present application, the compensation plate is composed of 1-3 single compensation plates.

[0015] As a further scheme of the present application, the intervals of the dots in the XY two directions are obtained by multiple repeated optimization.

[0016] As a further scheme of the present application, the dots are uniformly distributed on the compensation plate and are in the shape of a circle.

[0017] As a further scheme of the present application, comprising the following steps:

[0018] Firstly, a model of the compensation plate is established by lighttools, and the surface is plated with dots by means of three-dimensional texture;

[0019] Secondly, the radius and thickness of the dots are set, and the X-direction interval and Y-direction interval are set respectively;

[0020] Then, the light source properties in lighttools are set, the light source is spatial distribution, the light uniformity is 60%, and the non-uniform light reaches the receiver on the receiving surface through the compensation plate, the interval between the light source and the compensation plate is 0.01mm, and the interval between the compensation plate and the receiver is also 0.01mm.

[0021] Then the spacing of the dots in the XY two directions is added as an optimization variable, and a grid evaluation function is added to the receiver, and the change in the grid data is set as the scaling target based on the total power to adjust the light uniformity.

[0022] Then lighttools optimizes the model established at present to obtain the optimized spacing in the XY direction.

[0023] As a further scheme of the application, the spacing of the dots in the XY two directions is obtained through multiple iterations of optimization.

[0024] Compared with the prior art, the method provided by the application can use a single correction plate or at most three correction plates to be combined to target different transmittance distributions, and the correction plate does not have a limitation on the incident aperture angle, so the applicability is wider, and the relative positions of the multiple correction plates do not need to be changed. The method can greatly improve the light uniformity, and the uniformity is improved from 60%-70% to more than 90%, and the method can also avoid excessive loss of light intensity, so that the stability of photolithography is ensured. The method does not affect the optical path of the optical system, and the mechanical structure of the method is very simple because the correction plate does not need to be moved horizontally or vertically. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A compensation optical path schematic diagram is provided for the embodiment 1 of the application.

[0026] Figure 2 A schematic diagram of the distribution of the dots on the compensation device is provided for the embodiment 1 of the application.

[0027] Figure 3 A schematic diagram of the light with a uniformity of 60% on the receiver is provided for the embodiment 1 of the application.

[0028] Figure 4 A schematic diagram of the light uniformity after the second optimization of lighttools is provided for the embodiment 1 of the application.

[0029] Figure 5 A compensation optical path schematic diagram is provided for the embodiment 2 of the application.

[0030] Figure 6 A schematic diagram of the light uniformity after the optimization of lighttools is provided for the embodiment 2 of the application. DETAILED DESCRIPTION

[0031] The technical scheme of the application will be further described in detail in combination with the specific embodiments.

[0032] Embodiment 1

[0033] Referring to Figures 1 to 4 A light homogenization method suitable for an illumination system of a lithography machine, comprising the following steps:

[0034] Firstly, a model of the compensation plate is established by using lighttools, a correction plate with a size of 89mm*89mm and a thickness of 2.1mm is used, and a three-dimensional texture is used on the surface of the correction plate to coat the surface with round dots. A 5mm*5mm correction plate is used for observation during simulation;

[0035] Secondly, the radius and thickness of the round dots are set to 0.0023mm and 0.005mm respectively, and the X-direction interval and Y-direction interval are set to 0.07mm and 0.08mm respectively;

[0036] The light source properties in lighttools are set, the light source is spatially distributed, the light uniformity is 60%, and the inhomogeneous light reaches the receiver on the receiving surface through the correction plate, the interval between the light source and the correction plate is 0.01mm, and the interval between the correction plate and the receiver is also 0.01mm;

[0037] Then, the intervals of the round dots in the X and Y directions are added as optimization variables, and a grid evaluation function is added on the receiver, and the change in the grid data is set as a scaling target based on the total power to adjust the light uniformity;

[0038] After that, lighttools optimizes the currently established model to obtain the optimized X and Y direction intervals.

[0039] The optimized X and Y direction intervals on the correction plate are 0.0035365mm and 0.0053411mm respectively. After the first optimization by lighttools, the light uniformity is improved to 80.2%. After the second optimization, the X and Y direction intervals are 0.0036088mm and 0.0054314mm respectively, and the uniformity is 86.2%. Therefore, better optimization results can be achieved by repeated optimization.

[0040] Embodiment 2

[0041] Referring to Figures 5 to 6 A light homogenization method suitable for an illumination system of a lithography machine, comprising the following steps:

[0042] Firstly, a model of the compensation plate is established by using lighttools, two correction plates with a size of 5mm*5mm and a thickness of 2.1mm are used, and a three-dimensional texture is used on the surface of the correction plate to coat the surface with round dots. A 5mm*5mm correction plate is used for observation during simulation;

[0043] Second, the radius of the circle point is set to 0.0023mm and 0.005mm respectively, and the X direction interval is set to 0.07mm and the Y direction interval is set to 0.08mm respectively;

[0044] Then, the light source properties in lighttools are set, the light source is spatial distribution, the light uniformity is 60%, and the non-uniform light reaches the receiver on the receiving surface through the correction plate, the interval between the light source and the correction plate is 0.01mm, and the interval between the correction plate and the receiver is also 0.01mm;

[0045] Then, the intervals of the circle points in XY directions are added as optimization variables respectively, and the grid evaluation function is added on the receiver, and the change in the grid data is set as the scaling target based on the total power to adjust the light uniformity;

[0046] Then, lighttools optimizes the current established model to obtain the optimized XY direction interval.

[0047] The first correction plate obtained after optimization has an X direction interval of 0.020098mm and a Y direction interval of 0.008261mm, and the second correction plate has an X direction interval of 0.002643mm and a Y direction interval of 0.040006mm, and at this time the light uniformity reaches 95.25%.

[0048] In summary: the key innovation point of the present application is the distribution rule of the coordinate radius of the dots on the correction plate and on the surface of the correction plate, because the radius size, interval and coordinate of the dots in each square region on the correction plate are the key factors affecting the light uniformity and light intensity. Because the radius of the two adjacent dots is small and the interval is close, the interval can be approximately regarded as a slit, and when the light beam passes through the slit, the light beam will have interference phenomenon due to the wave nature of light. Therefore, multiple adjacent dots can form multiple slits, and when the light beam passes through each slit, the corresponding interference phenomenon will occur, and the superposition of multiple interference phenomena will make the light field also superimposed together, thereby improving the light uniformity. When the interval of the dots is too large, the wave nature of light is not reflected, and the interference phenomenon does not exist, so the light uniformity cannot be improved; multiple adjacent dots can form multiple slits, and when the light beam passes through each slit, the corresponding interference phenomenon will occur, and the superposition of multiple interference phenomena will make the light field also superimposed together, thereby improving the light uniformity. Therefore, the more the number of dots, the more the slits formed by the adjacent dots, and the more the light field that can be superimposed by the interference phenomenon, so the light uniformity can be better. Only when the radius of the dot on the surface of the correction plate is small enough, the dot can be approximately regarded as a point. A large number of dots are distributed in the square regions divided by the cross lines. In each square region, the dots are distributed according to a certain rule, and the overall shape is circular. Therefore, the light with poor uniformity after passing through the microlens array can be greatly improved in uniformity by the compensation method.

[0049] The method provided by the present application can use one or at most three correction plates to be combined for different transmittance distributions, and the correction plate has no limitation on the incident aperture angle, so the applicability is wider, and the relative positions of the multiple correction plates do not need to be changed. The method of the present application can greatly improve the light uniformity, and the uniformity is improved from 60%-70% to more than 90%, and the light intensity loss can also be avoided, thereby ensuring the stability of the photolithography; the method of the present application does not affect the optical path of the optical system, and the mechanical structure of the method is very simple because the correction plate does not need to be moved horizontally or vertically.

[0050] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0051] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes only one independent technical solution, and the specification is described in this way only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for homogenizing light suitable for use in an illumination system of a photolithography machine, characterized in that, The method comprises the following steps: First, a model of the correction plate is established by using lighttools, a 89mm*89mm*2.1mm correction plate is used, and a three-dimensional texture is used to simulate a surface plated with round dots, and a 5mm*5mm correction plate is taken for observation in simulation; Secondly, the radius and thickness of the round dots are set as 0.0023mm and 0.005mm respectively, and the interval of adjacent round dots in the X direction and the Y direction is set as 0.07mm and 0.08mm respectively; Then, the light source properties in lighttools are set, the light source is spatially distributed, the light uniformity is 60%, the non-uniform light reaches the receiver on the receiving surface through the correction plate, the interval between the light source and the correction plate is 0.01mm, and the interval between the correction plate and the receiver is also 0.01mm; Then, the intervals of the round dots in the XY directions are added as optimization variables respectively, and a grid evaluation function is added on the receiver, and the change in the grid data is set as a scaling target based on the total power to adjust the light uniformity; Then, lighttools optimizes the current established model to obtain the optimized XY direction interval; The correction plate is composed of 1-3 single correction plates.

2. The method of claim 1, wherein the light is uniform. The intervals of the round dots in the XY directions are obtained through multiple iterations.

3. The method of claim 1, wherein the light is uniform. The round dots are uniformly distributed on the correction plate and have a circular shape.

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