Calculation method of exposure dose of photolithography machine

Abstract

The present application relates to the technical field of photolithography machines, and more specifically, to a method for calculating the exposure dose of a photolithography machine. A method for calculating the exposure dose of a photolithography machine is provided, comprising: providing a first reflectivity sensor and a second reflectivity sensor at a first beam splitter prism and a second beam splitter prism at both ends of a light homogenization system, respectively, to obtain the radiation flux transmitted from the hypotenuse of the first beam splitter prism and the second beam splitter prism after the light emitted by the light source is reflected by a silicon wafer, an objective lens, and a mask; determining the light energy loss rate of the light homogenization system, the reflectivity of the silicon wafer, and the reflectivity of the objective lens based on the radiation flux collected by the first beam splitter prism and the second beam splitter prism; and determining the radiation flux based on the light energy loss rate of the light homogenization system, the reflectivity of the silicon wafer, and the reflectivity of the objective lens. In this way, the exposure dose can be accurately, quickly, and in real time calculated in combination with the exposure time.

Description

Technical Field

[0001] The present application relates to the technical field of photolithography machines, and more specifically, to a method for calculating the exposure dose of a photolithography machine. Background Art

[0002] The photolithography machine is an important equipment in the semiconductor manufacturing process. Its function is to accurately transfer the circuit pattern in the mask (also known as the photomask) to the silicon wafer according to the predetermined size and position through the exposure process.

[0003] Exposure of silicon wafers is a core process in photolithography, and its quality directly impacts the success of IC manufacturing. Furthermore, exposure quality is strongly correlated with exposure dose, which is the linear product of radiation flux and exposure time. Therefore, effective control of radiation flux is crucial during the exposure process. Typically, this is accomplished by controlling the shutter angle to control the amount of light transmitted through the illumination system. However, the mask, lens, and silicon wafer all reflect light energy, so accurately determining the reduction in light energy by each component in the exposure system is crucial for accurate exposure dose control.

[0004] Based on this, it is desired to provide an improved method for calculating the exposure dose of a lithography machine. Summary of the Invention

[0005] An embodiment of the present application provides an exposure dose calculation method for a lithography machine, which calculates the radiation flux on the silicon wafer by calculating the reflectivity of some components in the exposure light system, and thus calculates the exposure dose accurately, quickly and in real time in combination with the exposure time.

[0006] According to one aspect of the present application, a method for calculating the exposure dose of a photolithography machine is provided, comprising: providing a first reflectivity sensor and a second reflectivity sensor at a first beam splitter prism and a second beam splitter prism at both ends of a light homogenizing system, respectively, to obtain a radiant flux of light emitted by a light source and transmitted from the hypotenuse of the first beam splitter prism and the second beam splitter prism after being reflected by a silicon wafer, an objective lens, and a mask; determining, based on the radiant flux collected by the first beam splitter prism and the second beam splitter prism, a light energy loss rate of the light homogenizing system, a reflectivity of the silicon wafer, and a reflectivity of the objective lens; and determining, based on the light energy loss rate of the light homogenizing system, the reflectivity of the silicon wafer, and the reflectivity of the objective lens, the radiant flux using the following formula:

[0007]

[0008] Among them, E 曝光 is the exposure radiation flux of a single point on the silicon wafer, E 光源 is the radiant flux emitted by the light source, η 匀光 R is the loss rate of light energy by the uniform light system,硅片 is the single reflectivity of the silicon wafer, R 物镜 is the single reflectivity of the objective lens, m is the number of times the radiation flux is reduced to nearly 0 after the light propagates through the exposure system and undergoes m times of attenuation, and n is the number of times the light reflected from the light source enters the exposure system.

[0009] In the above-mentioned method for calculating the exposure dose of the lithography machine, the light energy loss rate of the uniform light system is:

[0010]

[0011] where η 匀光 is the loss rate of light energy by the light homogenization system, E1 is the radiation flux collected by the first reflectivity sensor, and E2 is the radiation flux collected by the second reflectivity sensor.

[0012] In the above-mentioned method for calculating the exposure dose of the lithography machine, the single reflectivity of the silicon wafer is calculated as:

[0013]

[0014]

[0015] where R* 硅片 is the total reflectivity obtained after multiple reflections of the silicon wafer, R 硅片 is the single reflectivity of the silicon wafer, E4 is the radiation flux collected by the second reflectivity sensor when there is no silicon wafer reflection, R fm is the reflectivity parameter obtained by pre-calibration of the basic marking plate FM, and R* fm It is the overall reflectivity obtained after multiple reflections of the basic marking plate FM.

[0016] In the above-mentioned method for calculating the exposure dose of the lithography machine, the reflectivity of the objective lens is calculated as:

[0017]

[0018]

[0019] where R* 物镜 is the overall reflectivity obtained after multiple reflections of the objective lens, R 物镜 is the single reflectivity of the objective lens, and E5 is the radiation flux collected by the second reflectivity sensor when only the objective lens reflects.

[0020] In the above-mentioned method for calculating the exposure dose of the lithography machine, the overall reflectivity of the basic marking plate FM is:

[0021]

[0022] Among them Efm The radiation flux collected by the second reflectivity sensor when the wafer moving stage places the basic marking plate FM under the exposure area, R* fm is the overall reflectivity of the basic marker plate FM.

[0023] The method for calculating the exposure dose of the lithography machine further includes:

[0024] A first light intensity detector is provided, wherein the first light intensity detector is used to detect the intensity of light irradiated to the silicon wafer;

[0025] A second light intensity detector is provided, the second light intensity detector being used to detect the light intensity of the light emitted by the light source and transmitted from the oblique surface of the first beam splitter prism through the pupil conversion system; and

[0026] A third light intensity detector is provided, wherein the third light intensity detector is used to detect the light intensity of the light emitted by the light source after passing through the pupil conversion system, the first beam splitter prism, the uniform light system, the second beam splitter prism and the relay system;

[0027] The formula for determining the radiant flux based on the light energy loss rate of the light homogenization system, the reflectivity of the silicon wafer, and the reflectivity of the objective lens is:

[0028]

[0029] in:

[0030]

[0031] η 光瞳转换 is the light energy loss rate of the pupil conversion system, η 中继 is the light energy loss rate of the relay system, θ1 is the transmittance of the hypotenuse of the first beam splitter prism, θ2 is the transmittance of the hypotenuse of the second beam splitter prism, and η 整体 is the transmittance of light energy in the entire system.

[0032] In the above-mentioned method for calculating the exposure dose of the lithography machine, the light energy loss rate of the pupil conversion system is:

[0033]

[0034] Among them E 光源 is the intensity of the light emitted by the light source, E 棱镜 is the radiant flux emitted by the light source and entering the beam splitter prism 1, and:

[0035]

[0036] Where θ1 is the transmittance of the hypotenuse of the first beam splitter prism, and E EDis the radiation flux collected by the second light intensity detector.

[0037] In the above-mentioned method for calculating the exposure dose of the lithography machine, the light energy loss rate of the relay system is:

[0038]

[0039] Among them E 光强3 is the radiation flux collected by the third light intensity detector, θ2 is the transmittance of the hypotenuse of the second beam splitter prism, S 靶面 is the photosensitivity area of ​​the third light intensity detector.

[0040] The method for calculating the exposure dose of the lithography machine further includes:

[0041] Move the third light intensity detector to the exposure area, calculate its irradiation flux based on the output current or voltage, and combine it with the pattern area on the mask to obtain the amount of light energy that should be transmitted to the silicon wafer;

[0042] The mask moving stage is moved so that the mask is in the exposure area, and the silicon wafer moving stage is moved so that the first light intensity detector is located in the exposure area, and the irradiation flux is calculated based on the output voltage or current of the first light intensity detector;

[0043] Then the energy loss rate of light in the transparent area of ​​the mask and the objective lens as a whole is:

[0044]

[0045] where η p1+r E is the loss rate of the light energy of the transparent part of the mask and the projection lens as a whole, including the reflectivity of the lens. 光强1 is the radiation flux collected by the first light intensity detector, E 光强3 is the radiation flux collected by the third light intensity detector, S is the transmission area of ​​the mask, S 靶面 is the photosensitive surface area of ​​the third light intensity detector;

[0046] have:

[0047] .

[0048] In the above-mentioned method for calculating the exposure dose of the lithography machine, the mask is replaced with a second mask with an absorption film coated on the reflective surface and the same pattern as the mask. The reflectivity of the mask is:

[0049]

[0050] where R' 掩膜版is the overall reflectivity of the mask, E2 is the radiant flux collected by the second reflectivity sensor, and E3 is the radiant flux measured by the second reflectivity sensor after the original mask is replaced with the second mask;

[0051] Combined with the data from the light intensity detector, the radiant flux is determined using the following formula:

[0052]

[0053] Where k1 and k2 are calculated coefficients obtained by fitting through calibration calculation, and the values ​​of k1 and k2 are related to the reflectivity of the mask, objective lens and silicon wafer:

[0054]

[0055] where R' 物镜 is the overall reflectivity of the objective lens, and R' 硅片 is the overall reflectivity of the silicon wafer;

[0056] b is the constant term that appears after fitting.

[0057] The exposure dose calculation method of the lithography machine provided in the embodiment of the present application can calculate the radiation flux on the silicon wafer by calculating the reflectivity of some components in the exposure light system, and thus accurately, quickly and in real time calculate the exposure dose in combination with the exposure time. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Various other advantages and benefits of the present application will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The drawings in the specification are intended only to illustrate preferred embodiments and are not to be construed as limiting the present application. Obviously, the drawings described below are merely examples of the present application, and those skilled in the art can derive other drawings based on these drawings without inventive effort. Throughout the drawings, the same reference numerals denote the same components.

[0059] Figure 1 The figure shows a schematic configuration diagram of an exposure optical system applied to the exposure dose calculation method of the lithography machine according to an embodiment of the present application.

[0060] Figure 2 The diagram shows a schematic configuration diagram of an improved exposure optical system to which an exposure dose calculation method for a lithography machine according to an embodiment of the present application is applied.

[0061] Figure 3 A flowchart illustrating an exemplary application process of the exposure dose calculation method of a lithography machine according to an embodiment of the present application is illustrated.

[0062] Figure 4 The figure shows the comparison of the radiation flux reflected by the light intensity detector 2 before and after the mask is placed; the solid line is the measurement data corresponding to the radiation flux of the light intensity detector 2 before and after the mask is placed (6 origins represent 6 sets of measurement values), and the dotted line is the straight line fitted by the measurement data of the light intensity detector 2 before and after the mask is placed. The dotted line corresponds to Figure 4 The formula is: y=0.8454x+0.0201, R 2 =0.9941 represents the degree of linear approximation between the original data and the formula. The dotted line and the solid line in the figure are used to indicate that the radiation flux measured by the light intensity detector 2 before and after the mask is placed changes in basically the same trend.

[0063] Figure 5 The figure shows the changing trend of the radiation flux collected by the reflectivity sensor 1 when the distance between the two moving mirrors in the pupil shaping system changes; Figure 5 The solid line in the middle represents the change in the radiation flux collected by the reflectivity sensor 1 when the distance between the two moving mirrors in the pupil shaping system changes. The six origins represent the values ​​of the measurement points. The formula y=0.0001x+0.1009 in the figure is the straight line formula fitted based on the measurement points. R 2 =0.9304 represents the degree of linear approximation between the original measurement data and this formula. This formula corresponds to the dotted line in the figure. Comparing the solid and dotted lines shows that as the distance between the two moving mirrors increases, the radiation flux measured by reflectivity sensor 1 increases substantially according to the fitting curve y = 0.0001x + 0.1009. When the distance between the two moving mirrors of the pupil shaping system changes, the illumination method of the exposure system also changes, and the radiation flux collected by reflectivity sensor 1 changes synchronously, that is, the radiation flux in the exposure system changes.

[0064] Figure 6 and Figure 7 The figure shows a schematic diagram of the change in the radiation flux of the reflectivity sensor 2 after replacing a mask with a different reflectivity.

[0065] Figure 8 The figure shows a schematic diagram of the change of the radiation flux of the light intensity detector 2 according to the change of the reflectivity of some structures in the exposure light system. DETAILED DESCRIPTION

[0066] Below, the exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the exemplary embodiments described herein.

[0067] In the exposure optical system of a lithography machine, optical lenses are usually coated with various necessary films, but even anti-reflection films will have some energy absorbed and reflected; similarly, in the exposure optical system, both the mask and the silicon wafer have a relatively high reflectivity, so the light emitted from the light source and entering the exposure optical system cannot completely hit the silicon wafer, which poses a problem for the accurate calculation of the exposure irradiance and exposure dose. Therefore, in the exposure dose calculation method of the lithography machine according to the embodiment of the present application, two reflectivity sensors and their corresponding light collecting devices are added to the original exposure optical system. Here, the light collecting device includes but is not limited to lenses, reflectors and corresponding light-uniform guiding devices. The two added reflectivity sensors are respectively located next to the two dichroic prisms of the exposure optical system, and can collect the reflected light from the silicon wafer, the mask and the projection objective lens and use them for real-time calculation, such as Figure 1 As shown, this provides detailed parameters for more accurate calculation of exposure irradiance and control of exposure time. Figure 1 The figure shows a schematic configuration diagram of an exposure optical system applied to the exposure dose calculation method of the lithography machine according to an embodiment of the present application.

[0068] like Figure 1 As shown, the light source of the exposure optical system is, for example, a mercury lamp, and a reflective bowl is used to focus the light emitted by the light source. Next to the two dichroic prisms of the exposure optical system, there is a reflectivity sensor as a light intensity detector, namely reflectivity sensor 1 and reflectivity sensor 2 in the figure, and the corresponding prisms are dichroic prism 1 and dichroic prism 2 respectively. The reflectivity of the two dichroic prisms should be greater than 95%, the transmittance should be at least 1%, and the optical properties of dichroic prism 1 and dichroic prism 2 should be consistent. When executing the exposure process, after the light source emits light, the light travels along the dichroic prism. Figure 1 The path shown in Figure 1 is projected onto the silicon wafer. During this process, light is reflected by the wafer, reticle, and projection objective. The reflected light passes through the right beam splitter prism, and a portion of the light is transmitted through the hypotenuse of the beam splitter prism. Reflectance sensor 2 receives this light energy. The energy reflected by beam splitter prism 2 (excluding the transmitted portion) enters the homogenization system and then beam splitter prism 1. Some light is further transmitted through the oblique surface of beam splitter prism 1 and reaches reflectance sensor 1. The energy received by reflectance sensor 1 includes energy reflected from the wafer, reticle, and projection objective back to the exposure system and transmitted through the hypotenuse of beam splitter prism 1. However, it should be noted that this energy is attenuated by the homogenization system. The light reflectivity of the pupil conversion system and relay system is extremely low and is therefore not included in this calculation. Additionally, a light intensity detector can be placed near the wafer to monitor the irradiance per unit area on the wafer before the exposure process begins.

[0069] Specifically, Figure 1 The reflectivity calculation process of each part in is as follows:

[0070] First, as mentioned above, in the exposure process, the reflectivity sensor 2 receives the light energy reflected back from the mask, silicon wafer, and projection lens and transmitted from the hypotenuse of the beam splitter 2, while the reflectivity sensor 1 receives the light energy reflected back from the mask, silicon wafer, and projection lens after being deducted by the uniform light system and transmitted from the hypotenuse of the beam splitter 1. Combining the transmittance and reflectivity of the hypotenuses of beam splitters 1 and 2 with the energy received by the reflectivity sensors 1 and 2, the deduction rate of the light energy by the uniform light system can be obtained. The specific calculation formula is:

[0071]

[0072] where η 匀光 is the light energy loss rate of the uniform light system, E1 is the radiation flux collected by the reflectivity sensor 1, and E2 is the radiation flux collected by the reflectivity sensor 2.

[0073] Furthermore, as mentioned above, the reflectivity sensor 2 receives the light energy reflected by the mask, silicon wafer, and projection lens, which enters the beam splitter prism 2 and is transmitted from its hypotenuse. Therefore, the reflectivity of the silicon wafer is calculated first.

[0074] Specifically, first replace the silicon wafer with another non-reflective material or a displacement motion stage so that the silicon wafer is not in the exposure area. Then, the reflectivity sensor 2 receives the light energy reflected by the mask and projection lens, entering the beam splitter prism 2 and transmitting out of its hypotenuse. Combined with the data from the light intensity detector and sorted, the reflectivity of the silicon wafer can be obtained as follows:

[0075]

[0076] where R* 硅片 is the overall reflectivity obtained after multiple reflections of the silicon wafer, and E4 is the radiation flux collected by the reflectivity sensor 2 when there is no reflection from the silicon wafer.

[0077] Here, to calculate the single reflectivity of the silicon wafer, it is necessary to use the following formula:

[0078]

[0079] where R 硅片 is the single reflectivity of the silicon wafer, R fm is the reflectivity parameter obtained by pre-calibration of the basic marking plate FM (the basic marking plate FM is fixed on the silicon wafer moving stage and moves synchronously with the silicon wafer moving stage. The basic marking plate FM is set on the side of the silicon wafer moving stage for placing the silicon wafer), that is, it is a preset parameter, and R* fm is the overall reflectivity obtained after multiple reflections of the basic marker plate FM, which is calculated as follows:

[0080] By moving the silicon wafer motion stage so that the basic marking plate FM (also referred to as FM plate or fm) is located under the exposure area, the radiation flux received by the reflectivity sensor 2 at this time is the radiation flux of light reflected back from the mask, projection lens and fm plate into the beam splitter prism 2 and transmitted from its hypotenuse. The overall reflectivity of the basic marking plate FM can be obtained as:

[0081]

[0082] Among them E fm The radiation flux collected by the second reflectivity sensor when the wafer moving stage places the basic marking plate FM under the exposure area, R* fm is the overall reflectivity of the basic marker plate FM.

[0083] Then, calculate the reflectivity of the projection objective:

[0084] If both the silicon wafer and the mask are replaced with a material that does not reflect light, the radiation flux collected by the reflectivity sensor 2 is the light reflected back by the projection lens into the beam splitter prism 2 and transmitted from its hypotenuse. The reflectivity of the projection lens can be obtained as:

[0085]

[0086] where R* 物镜 is the overall reflectivity obtained after multiple reflections, and E5 is the radiation flux collected by the reflectivity sensor 2 when only the projection objective lens reflects.

[0087] Similarly, it is also necessary to calculate the single reflectivity of the objective lens, that is:

[0088]

[0089] That is, because the reflection between two adjacent objects with the same reflective properties is continuous, the reflected energy will gradually approach 0, that is, the light intensity received by the silicon wafer and the projection lens surface should be a constant value. Therefore, in the exposure dose calculation method of the lithography machine according to the embodiment of the present application, the formula form of the radiation flux is an integral or cumulative fitting, as shown below:

[0090]

[0091] Where m is the number of times the radiation flux is reduced to nearly 0 after the light propagates through the exposure system and undergoes m attenuations, and n is the number of times the light reflected from the light source enters the exposure system.

[0092] Therefore, the formula for calculating the radiant flux on the silicon wafer is:

[0093]

[0094] Then, based on the radiation flux, or irradiance, combined with the exposure time, the exposure dose can be calculated.

[0095] Furthermore, if the attenuation of the radiation flux by the pupil conversion system and the relay system is considered, the following can be further improved: Figure 1 The exposure optical system shown here. Figure 2 The diagram shows a schematic configuration diagram of an improved exposure optical system to which an exposure dose calculation method for a lithography machine according to an embodiment of the present application is applied.

[0096] like Figure 2 As shown, the improved exposure optical system is compared with Figure 1 The exposure optical system shown in the figure adds light intensity detectors 1, 2, and 3. Furthermore, light intensity detector 2 may include a corresponding light-collecting device, including but not limited to a reflector, a lens assembly, a diffuser, and a pinhole. This light-collecting device should be placed in front of the detector along the direction of light incidence. Furthermore, reflectivity sensors 1 and 2 may also include corresponding light-collecting devices, including but not limited to a reflector, a lens assembly, a diffuser, and a pinhole. This light-collecting device should be placed in front of the reflectivity sensors along the direction of light incidence.

[0097] Therefore, in the exposure dose calculation method of the lithography machine according to an embodiment of the present application, the first reflectivity sensor and the second reflectivity sensor respectively include corresponding light collecting devices, and the light collecting devices include at least one of a reflector, a lens group, a scattering plate and a small hole, and are arranged in front of the first reflectivity sensor and the second reflectivity sensor along the light incident direction.

[0098] As mentioned above, the reflectivity of beam splitter 1 and beam splitter 2 should be greater than 95%, and the transmittance should be at least 1%. Therefore, a portion of the light emitted by the light source will be transmitted through the oblique surface of beam splitter 1 and collected by light intensity detector 2. It is worth noting that reflectivity sensors 1 and 2 will only receive the radiation flux reflected from the reflective structure, entering the exposure optical system and transmitting through the oblique edges of beam splitter 1 and beam splitter 2, and light intensity detector 2 can only receive the radiation flux emitted by the light source, entering the exposure optical system, and transmitting through the oblique edge of beam splitter 1. Therefore, the radiation flux of the light emitted by the light source and entering beam splitter 1 after being deflected by the pupil conversion system is:

[0099]

[0100] Among them E 棱镜 is the radiation flux emitted by the light source and entering the dichroic prism 1, θ1 is the transmittance of the hypotenuse of the dichroic prism 1, and E EDis the radiation flux collected by the light intensity detector 2. The light emitted by the light source will pass through a certain device, such as a reflective bowl, to be concentrated, and then the pupil conversion system will produce a loss of light energy. In this way, after calibrating the energy emitted by the light source, the loss rate of light energy by the pupil conversion system can be obtained as:

[0101]

[0102] Among them E 光源 is the intensity of the light emitted by the light source, η 光瞳转换 is the light energy loss rate of the pupil conversion system.

[0103] If it is difficult to calibrate the light source energy, the loss rate of light energy by the pupil conversion system can be ignored. That is, the pupil conversion system and the light source can be regarded as a whole, and the radiation flux emitted from the pupil conversion system can be regarded as the radiation flux emitted by the light source after a certain attenuation. The energy of the light source can be obtained as E 光源 =E 棱镜 .

[0104] In addition, the light intensity detector 3 is located next to the mask. The motion stage moves the mask so that the light hits the light intensity detector 3. At this time, the light path is as follows: after the light source emits light, the light passes through the pupil conversion system, the beam splitter prism 1, the uniform light system, the beam splitter prism 2, the relay system, and finally hits the light intensity detector 3. Combining the data of the light intensity detector 3, the loss rate of the relay system on the light radiation flux can be obtained:

[0105]

[0106] Among them, η 中继 is the loss rate of light energy by the relay system, E 光强3 is the radiation flux collected by the light intensity detector 3, and θ2 is the transmittance of the hypotenuse of the dichroic prism 2.

[0107] By calculating the reflectivity of the mask, projection lens, and silicon wafer, as well as the light loss rate of the pupil conversion system, uniform light system, and relay system, the radiation flux on the silicon wafer can be calculated similarly to the above formula:

[0108]

[0109] in:

[0110]

[0111] where η 整体 Indicates the transmittance of light energy in the entire system.

[0112] Furthermore, by checking the data from light intensity detector 2, we can know the intensity of the light emitted by the light source and reaching the beam splitter prism 1 after passing through the pupil conversion system. And by checking the data from light intensity detector 1, we can know the irradiance per unit area of ​​the exposure optical system on the silicon wafer (note that this is the irradiance when there is no reflection from the silicon wafer). Therefore, by combining the data from the reflectivity sensor and light intensity detector obtained above with the set exposure time, we can calculate the exposure dose on the silicon wafer. The calculation process is roughly as follows:

[0113] First, move the light intensity detector 3 below the exposure area, and calculate its irradiance (radiant flux per unit area) based on the output current / voltage. Then, the light energy that should be transmitted to the silicon wafer can be obtained by combining the pattern area on the mask. At this time, the mask moving stage is shifted so that the mask is within the exposure area, and the silicon wafer moving stage is shifted so that the light intensity detector 1 is within the exposure area. The irradiance is calculated based on its output voltage / current. The light energy loss rate of the mask transparent area and the projection objective lens as a whole (including the reflectivity of the projection objective lens) can be obtained as follows:

[0114]

[0115] where η p1+r E is the energy loss rate of the light transmitted by the mask and the projection lens as a whole, 光强1 is the radiation flux collected by the light intensity detector 1, E 光强3 is the radiation flux collected by the light intensity detector 3, S is the transparent area of ​​the mask (i.e. the area of ​​the pattern to be exposed), S 靶面 is the photosensitive surface area of ​​the light intensity detector 3.

[0116] Therefore, the transmittance η of the entire exposure optical system to light energy is 整体 for:

[0117]

[0118] That is, the above formula can calculate and fit the loss suffered by light during propagation and the energy extreme value reached at each point after n reflections. Combined with the data of the light intensity detector and the data of the reflectivity sensor, the above has obtained the overall reflectivity of multiple reflections of the silicon wafer, mask, and objective lens through calculation. It can be obtained that during exposure, the reflectivity sensor 1 receives the light reflected back to the exposure system by the mask, silicon wafer, and objective lens and lost by the uniform light system. It can be obtained that the light reflected back by the mask, silicon wafer, and objective lens enters the exposure optical system the same number of times as the light emitted by the light source. Therefore, it can be obtained that the proportion of the mask, silicon wafer, and objective lens received by the reflectivity sensor should be the same as the proportion of their overall reflectivity.

[0119] In another example, the mask is replaced with a second mask with an absorbent film coated on the reflective surface and the same pattern as the mask. The reflectivity sensor 2 now receives the light energy reflected by the silicon wafer and the projection lens, entering the beam splitter prism 2 and transmitting out of its hypotenuse. Combined with the data from the light intensity detector, the reflectivity of the mask can be obtained as follows:

[0120]

[0121] Where E3 is the radiation flux measured by the second reflectivity sensor after the original mask is replaced with the second mask. This needs to be calibrated before exposure.

[0122] And, combined with the data from the light intensity detector, we can get:

[0123]

[0124] Among them, k1 and k2 are the calculation coefficients obtained after fitting by the traditional calibration calculation method. The coefficient of k should be consistent with R' 掩膜版 , R' 硅片 , R' 物镜 , that is, the overall reflectivity of the mask, objective lens and silicon wafer is related, for example:

[0125]

[0126] Since other lenses in the exposure light system may also have reflectivity after coating, the above coefficients will vary with the exposure system structure. b is a constant term that appears after fitting and can be 0. This formula fits the complex reflection process of the exposure light system into a single process of reflected light. The specific reflectivity is calculated through the similar linear relationship between the radiant flux of the light intensity detector and the reflectivity sensor. Combined with the calibration relationship between light intensity detector 2 and light intensity detector 1 and the radiant flux data from reflectivity sensor 1, the final radiant flux impinging on the silicon wafer can be determined. Compared to calculations based solely on reflectivity, this calculation method can more simply and quickly fit the exposure dose calculation formula and is applicable to most exposure system structures.

[0127] In addition, when performing multi-mask rotation exposure, the reflectivity of different masks and silicon wafers after exposure is different from that of the previous masks and silicon wafers. In this case, the reflectivity calculation scheme mentioned in the exposure dose calculation method of the lithography machine according to the embodiment of the present application is used (which can be written into the program to calculate the corresponding reflectivity in real time based on the mask and silicon wafer used for exposure) to obtain the reflectivity of the mask and silicon wafer in real time, and calculate the radiation flux hitting the silicon wafer accordingly. Then, the exposure time is inferred based on the exposure dose required for this exposure to complete an accurate exposure. The specific process is as follows. Figure 3 shown. Figure 3A flowchart illustrating an exemplary application process of the exposure dose calculation method of a lithography machine according to an embodiment of the present application is illustrated.

[0128] Compared to other existing exposure dose calculation schemes, the exposure dose calculation method for a lithography machine according to the embodiments of this application adds a light intensity detector and a reflectivity sensor to the traditional calculation method to calculate the specific reflectivity of certain structures in the exposure light system. Compared to traditional exposure dose calculation schemes, the incorporation of the concept of reflectivity increases the accuracy of the physical-level fitting of the exposure dose calculation scheme and reduces parameter uncertainty in the exposure dose fitting algorithm. This significantly improves the efficiency and accuracy of the formula fitting of the exposure dose calculation scheme.

[0129] Furthermore, the exposure dose calculation method for a lithography machine according to an embodiment of the present application is also applicable to use during multi-plate rotation exposure. That is, during multi-plate rotation exposure, the mask and silicon wafer are replaced, which results in the exposure time calculated based on the original reflectivity being unsuitable for the new exposure. The exposure dose calculation method for a lithography machine according to an embodiment of the present application can calculate the reflectivity of each component in the exposure system and the exposure irradiance on the silicon wafer in a short period of time, thereby calculating the exposure time corresponding to the required exposure dose. This greatly increases the control accuracy of the exposure dose, reduces the time required for multi-plate rotation exposure, and improves the working efficiency of the lithography machine.

[0130] Experimental Verification Description

[0131] In traditional solutions, the radiation flux of light intensity detector 2 and light intensity detector 1 are used to fit the formula to obtain the exposure dose, and the output value of the detector is calibrated before exposure to monitor the radiation flux hitting the silicon wafer in real time during the exposure process. However, in the actual exposure process, structures with reflective properties will reflect light to the light source, such as the reflective bowl of the light source, and return it to the exposure system.

[0132] The following data is from the light intensity detector 2 and reflectivity sensor 1, obtained with and without a mask or wafer (a type of material with high reflectivity). This data is derived by using a moving mirror in the pupil conversion system to change the illumination method. (The following data is compared with and without a mask. The overall reflectivity of the mask is approximately 50%, a known reticle reflectivity that can be used to calibrate the reflectivity sensor.) The pupil conversion system has two moving mirrors, and the illumination method can be changed by varying the distance between the two mirrors.

[0133]

Table 1

[0134]

[0135]

Table 2

[0136]

[0137] It can be seen from Table 1 and Table 2 that the moving mirror spacing in the pupil conversion system of the exposure system will affect the radiation flux collected by the light intensity detector 2 and the reflectivity sensor 1, that is, the moving mirror spacing in the pupil conversion system will affect the radiation flux of the entire exposure system, that is, it will affect the exposure radiation flux.

[0138] Figure 4 The figure shows the comparison of the radiation flux reflected by the light intensity detector 2 before and after the mask is placed. Figure 4 As shown, from the comparison data, it can be seen that the radiation flux of the light intensity detector 2 increases by a certain percentage after the mask is placed, that is, after the mask is placed, not only the radiation flux of the reflectivity sensor will increase to a certain extent, but the light intensity detector 2 will also be affected.

[0139] Figure 5 The figure shows the comparison of the radiation flux reflected by the light intensity detector 2 before and after the placement of the mask and the silicon wafer. Figure 5 As shown, when optical structures with reflective properties such as masks and silicon wafers are placed, the radiation flux collected by the light intensity detector 2 will also change, which verifies the above-mentioned "structures with reflective properties will reflect light to the light source and return it to the exposure optical system."

[0140] When the reflectivity of reflective objects such as the mask is different, the radiation flux collected by the corresponding light intensity detector 2, reflectivity sensor 1 and reflectivity sensor 2 will also change. Figure 5 The comparative changes in the radiation flux of the light intensity detector 2 and the reflectivity sensor 1 when using three masks with different reflectivities of approximately 40%, 50% and 60% are listed.

[0141] Figure 6 and Figure 7 The figure shows the change of the radiation flux of the reflectivity sensor 2 after replacing the mask with different reflectivity. Figure 6 and Figure 7 As shown, it can be understood that the reflectivity change of the structure in the exposure light system will affect the radiation flux in the entire system, and thus affect the calculation of the exposure dose.

[0142] Figure 8 The figure shows the change of the radiation flux of the light intensity detector 2 according to the change of the reflectivity of some structures in the exposure light system. Figure 8 As shown, combined Figure 6 and Figure 7 It can be understood that the radiation flux of the reflectivity sensor and the light intensity detector is positively correlated with the reflectivity of some structures of the exposure light system, that is, different reflectivities will cause changes in the radiation flux of the reflectivity sensor and the light intensity detector.

[0143] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to necessarily being implemented using the above specific details.

[0144] The block diagrams of the devices, devices, equipment, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "include," "comprise," "have," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0145] It should also be noted that in the apparatus, device, and method of the present application, each component or each step can be decomposed and / or recombined, and such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0146] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0147] The above description has been provided for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for calculating the exposure dose of a lithography machine, wherein: include: A first reflectivity sensor and a second reflectivity sensor are respectively provided at the first beam splitter prism and the second beam splitter prism at both ends of the light homogenization system to obtain the radiation flux of the light emitted by the light source and transmitted from the hypotenuse of the first beam splitter prism and the second beam splitter prism after being reflected by the silicon wafer, the objective lens and the mask; Determining the light energy loss rate of the light homogenization system, the reflectivity of the silicon wafer, and the reflectivity of the objective lens based on the radiation flux collected by the first beam splitter prism and the second beam splitter prism; as well as, Based on the light energy loss rate of the light homogenization system, the reflectivity of the silicon wafer, and the reflectivity of the objective lens, the radiant flux is determined by the following formula: ； Among them, E 曝光 is the exposure radiation flux of a single point on the silicon wafer, E 光源 is the radiant flux emitted by the light source, η 匀光 R is the loss rate of light energy by the uniform light system, 硅片 is the single reflectivity of the silicon wafer, R 物镜 is the single reflectivity of the objective lens, m is the number of times the radiation flux is reduced to nearly 0 after the light propagates through the exposure system and undergoes m times of attenuation, and n is the number of times the light reflected from the light source enters the exposure system.

2. The method for calculating the exposure dose of a lithography machine according to claim 1, wherein: The light energy loss rate of the uniform light system is: ； where η 匀光 is the loss rate of light energy by the light homogenization system, E1 is the radiation flux collected by the first reflectivity sensor, and E2 is the radiation flux collected by the second reflectivity sensor.

3. The method for calculating the exposure dose of a lithography machine according to claim 2, wherein: The single reflectivity of the silicon wafer is calculated as: ； ； where R* 硅片 is the total reflectivity obtained after multiple reflections of the silicon wafer, R 硅片 is the single reflectivity of the silicon wafer, E4 is the radiation flux collected by the second reflectivity sensor when there is no silicon wafer reflection, R fm is the reflectivity parameter obtained by pre-calibration of the basic marking plate FM, and R* fm It is the overall reflectivity obtained after multiple reflections of the basic marking plate FM.

4. The method for calculating the exposure dose of a lithography machine according to claim 3, wherein: The reflectivity of the objective lens is calculated as: ； ； where R* 物镜 is the overall reflectivity obtained after multiple reflections of the objective lens, R 物镜 is the single reflectivity of the objective lens, and E5 is the radiation flux collected by the second reflectivity sensor when only the objective lens reflects.

5. The method for calculating the exposure dose of a lithography machine according to claim 3 or 4, wherein: The overall reflectivity of the base marker plate FM is: ； Among them E fm The radiation flux collected by the second reflectivity sensor when the wafer moving stage places the basic marking plate FM under the exposure area, R* fm is the overall reflectivity of the basic marker plate FM.

6. The method for calculating the exposure dose of a lithography machine according to claim 1, wherein: Further including: A first light intensity detector is provided, wherein the first light intensity detector is used to detect the intensity of light irradiated to the silicon wafer; A second light intensity detector is provided, the second light intensity detector being used to detect the light intensity of the light emitted by the light source and transmitted from the oblique surface of the first beam splitter prism through the pupil conversion system; and A third light intensity detector is provided, wherein the third light intensity detector is used to detect the light intensity of the light emitted by the light source after passing through the pupil conversion system, the first beam splitter prism, the uniform light system, the second beam splitter prism and the relay system; The formula for determining the radiant flux based on the light energy loss rate of the light homogenization system, the reflectivity of the silicon wafer, and the reflectivity of the objective lens is: ； in: ； η 光瞳转换 is the light energy loss rate of the pupil conversion system, η 中继 is the light energy loss rate of the relay system, θ1 is the transmittance of the hypotenuse of the first beam splitter prism, θ2 is the transmittance of the hypotenuse of the second beam splitter prism, and η 整体 is the transmittance of light energy in the entire system.

7. The method for calculating the exposure dose of a lithography machine according to claim 6, wherein: The light energy loss rate of the pupil conversion system is: ； Among them E 光源 is the intensity of the light emitted by the light source, E 棱镜 is the radiant flux emitted by the light source and entering the beam splitter prism 1, and: ； Where θ1 is the transmittance of the hypotenuse of the first beam splitter prism, and E ED is the radiation flux collected by the second light intensity detector.

8. The method for calculating the exposure dose of a lithography machine according to claim 7, wherein: The loss rate of light energy by the relay system is: ； Among them E 光强3 is the radiation flux collected by the third light intensity detector, θ2 is the transmittance of the hypotenuse of the second beam splitter prism, S 靶面 is the photosensitivity area of ​​the third light intensity detector.

9. The method for calculating the exposure dose of a lithography machine according to claim 6, wherein: Further including: Move the third light intensity detector to the exposure area, calculate its irradiation flux based on the output current or voltage, and combine it with the pattern area on the mask to obtain the amount of light energy that should be transmitted to the silicon wafer; The mask moving stage is moved so that the mask is in the exposure area, and the silicon wafer moving stage is moved so that the first light intensity detector is located in the exposure area, and the irradiation flux is calculated based on the output voltage or current of the first light intensity detector; Then the energy loss rate of light in the transparent area of ​​the mask and the objective lens as a whole is: ； where η p1+r E is the loss rate of the light energy of the transparent part of the mask and the projection lens as a whole, including the reflectivity of the lens. 光强1 is the radiation flux collected by the first light intensity detector, E 光强3 is the radiation flux collected by the third light intensity detector, S is the transmission area of ​​the mask, S 靶面 is the photosensitive surface area of ​​the third light intensity detector; have: 。 10. The method for calculating the exposure dose of a lithography machine according to claim 1, wherein: The mask is replaced with a second mask with an absorption film coated on the reflective surface and the same pattern as the mask. The reflectivity of the mask is: ； where R' 掩膜版 is the overall reflectivity of the mask, E2 is the radiant flux collected by the second reflectivity sensor, and E3 is the radiant flux measured by the second reflectivity sensor after the original mask is replaced with the second mask; Combined with the data from the light intensity detector, the radiant flux is determined using the following formula: ； Where k1 and k2 are calculated coefficients obtained by fitting through calibration calculation, and the values ​​of k1 and k2 are related to the reflectivity of the mask, objective lens and silicon wafer: ； where R' 物镜 is the overall reflectivity of the objective lens, and R' 硅片 is the overall reflectivity of the silicon wafer; b is the constant term that appears after fitting.

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