Compensation method and device for overlay error of photoetching process and photoetching machine

Abstract

The invention discloses a compensation method and device for an overlay error of a photoetching process and a photoetching machine, which can be used in the field of semiconductor manufacturing, and the method comprises the following steps: firstly, obtaining overlay error distribution data; then, on the basis of the overlay error distribution data and a cubic polynomial which is established in advance and used for representing the relation between the overlay error and the position coordinates, the estimated values of all coefficients in the cubic polynomial are determined, and error compensation parameters are obtained; then, determining a target compensation scheme based on the error compensation parameter and a function relationship between the compensation scheme and the error compensation parameter; the compensation scheme comprises compensation heat doses corresponding to at least 20 heat input areas and compensation stress corresponding to a plurality of stress compensation points; and finally, based on the target compensation scheme, applying a compensation heat dose to each heat input region of the mask, and applying a compensation stress to a stress compensation point of the mask. Therefore, stress compensation and pixel-level thermal compensation can be carried out on the mask plate, and the photoetching precision is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing technology, and in particular to a method, device and lithography machine for compensating overlay errors in a lithography process. Background Art

[0002] With the development of semiconductor technology, the integration of chips has been significantly improved, and the requirements for overlay errors in the photolithography process have become increasingly stringent.

[0003] In semiconductor manufacturing, overlay error refers to the offset between each circuit layer and can be quantitatively described as the coordinate deviation between the lithographic pattern and the reference pattern in the X and Y directions. Traditional projection lithography systems rely on optical lenses to compensate for overlay error. However, as technology nodes shrink, this compensation capability is gradually reaching its limit, making it difficult to meet current lithography quality requirements.

[0004] Therefore, how to reduce the overlay error of the photolithography process becomes a problem that needs to be solved. Summary of the Invention

[0005] Based on the above problems, the present application provides a method, device and lithography machine for compensating the overlay error of the lithography process, which can reduce the overlay error of the lithography process.

[0006] The embodiments of this application disclose the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides a method for compensating overlay error in a photolithography process, the method comprising:

[0008] Obtaining overlay error distribution data;

[0009] Based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates, determining estimated values ​​of coefficients of each term in the cubic polynomial to obtain error compensation parameters;

[0010] Determining a target compensation scheme based on the error compensation parameter and a functional relationship between the compensation scheme and the error compensation parameter; the compensation scheme includes a compensation thermal dose corresponding to each of at least 20 heat input areas and a compensation stress corresponding to each of a plurality of stress compensation points;

[0011] Based on the target compensation scheme, a compensation thermal dose is applied to each heat input region of the mask, and a compensation stress is applied to the stress compensation point of the mask.

[0012] Optionally, applying a compensation thermal dose to each heat input area of ​​the mask based on the target compensation scheme includes:

[0013] determining a heating pattern based on the compensated thermal doses corresponding to the respective heat input areas in the target compensation scheme;

[0014] Based on the heating pattern, the optical system is driven to modulate the heating light source, and the digital micromirror array is driven to reflect the modulated heating light source onto the mask, so as to apply a compensation thermal dose to each heat input area of ​​the mask.

[0015] Optionally, after driving the optical system to modulate the heating light source based on the heating pattern, and driving the digital micromirror array to reflect the modulated heating light source onto the reticle to apply a compensating thermal dose to each heat input area of ​​the reticle, the method further includes:

[0016] Obtain the current temperature of each heat input area through the temperature sensor;

[0017] Based on the current temperature of each heat input area and the target temperature of each heat input area after applying the compensation thermal dose, the state of each micromirror in the digital micromirror array is dynamically adjusted so that the current temperature approaches the target temperature.

[0018] Optionally, the number of the heat input areas is 143.

[0019] Optionally, the 143 heat input areas are arranged in an equally spaced square matrix with 11 heat input areas in the horizontal direction and 13 heat input areas in the vertical direction.

[0020] Optionally, the heat input area is a rectangle with a length of 3 mm and a width of 2 mm.

[0021] Optionally, determining estimated values ​​of coefficients of each term in the cubic polynomial based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates to obtain the error compensation parameters includes:

[0022] Based on the overlay error distribution data and a pre-established cubic polynomial for expressing the relationship between the overlay error and the position coordinates, estimated values ​​of coefficients in the cubic polynomial are determined by the least squares method to obtain error compensation parameters.

[0023] In a second aspect, an embodiment of the present application provides a device for compensating for overlay error in a photolithography process, the device comprising: an acquisition module, a parameter determination module, a solution determination module, and a compensation module;

[0024] The acquisition module is used to acquire overlay error distribution data under current lithography conditions;

[0025] The parameter determination module is configured to determine, based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates, estimated values ​​of coefficients of each term in the cubic polynomial to obtain error compensation parameters;

[0026] The scheme determination module is configured to determine a target compensation scheme based on the error compensation parameter and a functional relationship between the compensation scheme and the error compensation parameter; the compensation scheme includes a compensation thermal dose corresponding to each of at least 20 heat input areas and a compensation stress corresponding to each of a plurality of stress compensation points;

[0027] The compensation module is used to apply a compensation thermal dose to each heat input area of ​​the mask and apply a compensation stress to the stress compensation point of the mask based on the target compensation scheme.

[0028] In a third aspect, an embodiment of the present application provides a lithography machine, the lithography machine comprising: a controller, a stress actuator, and a local heating system;

[0029] The controller is electrically connected to the stress actuator and the local heating system;

[0030] The controller is used to drive the stress actuator to apply compensating stress to the stress compensation point of the mask according to the method for compensating the overlay error of the lithography process described in any embodiment of the first aspect, and to drive the local heating system to apply compensating thermal dose to each heat input area of ​​the mask.

[0031] Optionally, the local heating system includes a digital micromirror array, a heating light source, and an optical system;

[0032] The local heating system is used to respond to the drive of the controller, modulate the heating light source through the optical system, focus the heating light source on each micromirror in the digital micromirror array, and reflect the modulated heating light source onto the mask through the digital micromirror array to apply a compensating thermal dose to each heat input area of ​​the mask.

[0033] Compared with the prior art, this application has the following beneficial effects:

[0034] Based on the overlay error distribution data, the compensation stress required to compensate for the overlay error and the compensation thermal dose corresponding to at least 20 heat input areas are obtained, thereby realizing stress compensation and pixel-level thermal compensation of the mask to cause mask deformation, thereby accurately compensating for the overlay error existing in the lithography process. This can effectively reduce the overlay error of the lithography process, improve the lithography accuracy, realize high-precision pattern transfer for small feature size patterns, improve product reliability and yield, and reduce large-scale production costs.

[0035] In addition, the compensation method for lithography process overlay error provided in the embodiment of the present application can be applied to various lithography technologies such as extreme ultraviolet lithography (EUVL), deep ultraviolet lithography (DUVL), nanoimprint lithography (NIL), surface plasmon lithography (SPL), etc., and has strong versatility. Whether in the field of high-precision semiconductor manufacturing or in the field of micro-nano structure processing, it can provide a high-precision overlay error compensation solution based on thermal compensation and stress compensation to meet the needs of different processes and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 A flow chart of a method for compensating overlay errors in a photolithography process provided in an embodiment of the present application;

[0038] Figure 2 A schematic diagram of an overlay error compensation mechanism provided in an embodiment of the present application;

[0039] Figure 3 An overlay error distribution vector diagram provided in an embodiment of the present application;

[0040] Figure 4 A schematic diagram of a heating image of the compensation thermal dose corresponding to each heat input area provided in an embodiment of the present application;

[0041] Figure 5 A schematic diagram showing the stress distribution of the compensation stress corresponding to each stress compensation point provided in the embodiment of the present application;

[0042] Figure 6 A vector diagram of overlay error compensation provided in an embodiment of the present application;

[0043] Figure 7 An overlay residual distribution vector diagram provided in an embodiment of the present application;

[0044] Figure 8 A schematic diagram of the compensation effect of 24 times of overlay error compensation in the X direction provided in an embodiment of the present application;

[0045] Figure 9 A schematic diagram of the compensation effect of 24 times of overlay error compensation in the Y direction provided in an embodiment of the present application;

[0046] Figure 10A schematic diagram of a device for compensating overlay errors in a photolithography process provided in an embodiment of the present application. DETAILED DESCRIPTION

[0047] The method, device and lithography machine for compensating overlay errors in a lithography process provided in the present application can be used in the field of semiconductor manufacturing. The above is only an example and does not limit the application field of the method, device and lithography machine for compensating overlay errors in a lithography process provided in the present application.

[0048] The terms "first", "second", "third" and "fourth" in the specification, claims and drawings of this application are used to distinguish different objects rather than to limit a specific order.

[0049] In the embodiments of this application, words such as "as an example" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described in the embodiments of this application as "as an example" or "for example" should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "as an example" or "for example" is intended to present the relevant concepts in a concrete manner.

[0050] The terms used in the implementation section of this application are only used to explain the specific embodiments of this application and are not intended to limit this application.

[0051] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0052] See also Figure 1 , this figure is a flow chart of a photolithography process overlay error compensation method provided in an embodiment of the present application, which can be executed by a compensation model.

[0053] As an example, the compensation model can be a finite element model. The input parameters of the compensation model may include, but are not limited to, physical parameters such as the thermal conductivity and expansion coefficient of the mask material, as well as environmental parameters such as the temperature changes in the lithography machine's operating environment. By coupling calculations of multiple physical fields, including temperature, stress, and deformation fields, and performing numerical simulations based on the compensation scheme, the reticle's response during the lithography process, such as its thermodynamic deformation response and mechanical response to stress loading, can be accurately predicted. The compensation model enables the calculation of error compensation parameters based on overlay error distribution data and rigorous simulation of overlay error compensation, further deriving the target compensation scheme.

[0054] In some embodiments, multiple compensation models can be pre-established based on various requirements, such as the lithography machine and / or mask used, and the required compensation accuracy. When selecting a compensation model, factors such as compensation accuracy, model computational capability, and model adaptability and scalability can be comprehensively considered to select an appropriate compensation model. Constraints are then set for the output of the compensation model (i.e., the target compensation solution) based on factors such as the process tolerance range, the corresponding equipment performance of each compensation item, and production efficiency, to ensure that the target compensation solution does not exceed the physical limits of the equipment or cause other process anomalies.

[0055] The method for compensating the overlay error of the photolithography process provided in the embodiment of the present application specifically includes:

[0056] S101: Acquire overlay error distribution data.

[0057] As an example, the current lithography parameters can be used to perform a lithography process on the wafer to obtain a lithography pattern; then the deviation between the lithography pattern and the reference pattern can be measured to obtain the overlay error distribution data corresponding to the current lithography parameters. For example, a high-resolution optical microscope with image recognition and measurement functions can be used to scan the displayed lithography pattern through an automated measurement system to accurately capture the offset of the lithography pattern on the X and Y axes, and obtain the overlay error δ between the lithography pattern and the reference pattern at each acquisition point on the wafer. x The measurement process must be carried out in a clean and temperature-stable environment to prevent external interference from affecting data accuracy.

[0058] Optionally, the overlay error distribution data can include the offset between the lithographic pattern and the reference pattern at each acquisition point, as well as parameters such as the error distribution pattern and root mean square error (RMS). The overlay error distribution data can be stored in a table or matrix format and, after digitization, packaged into a standard format suitable for input into a compensation model for use in subsequent steps to compensate for overlay errors. For example, the overlay error for each acquisition can be the sum of the absolute mean of the acquisition point offset values ​​and three times their standard deviation, |mean| + 3σ.

[0059] S102: Based on the overlay error distribution data and a pre-established cubic polynomial for expressing the relationship between the overlay error and the position coordinates, an estimated value of each coefficient in the cubic polynomial is determined to obtain an error compensation parameter.

[0060] Specifically, the cubic polynomial used to express the relationship between the overlay error and the position coordinates can be:

[0061] δx=k1+k3·x+k5·y+k7·x 2 +k9·xy+k 11 ·y 2 +k13 x 3 +k 15 ·x 2 y+k 17 ·xy 2 +k 19 ·y 3 ; δy=k2+k4·y+k6·x+k8·y 2 +k 10 ·xy+k 12 ·x 2 +k 14 y 3 +k 16 ·y 2 x+k 18 ·yx 2 +k 20 ·x 3 .

[0062] Among them, k1, k2,…, k 20 is the error compensation parameter for compensating the overlay error of the lithography machine; δ x is the overlay error measured in the X direction, and δy is the overlay error measured in the Y direction.

[0063] For example, the coefficients (i.e., error compensation parameters) in the cubic polynomial can be fitted by the least squares method to minimize the actual overlay error (δ x and δy) and the predicted overlay error (δx(x i ,y i ) and δy(x i ,y i )), that is:

[0064]

[0065] From this, the coefficients k1, k2, ..., k in the cubic polynomial can be determined. 20 The estimated value of is used to obtain the error compensation parameter.

[0066] Optionally, after obtaining the estimated values ​​of each coefficient, the P value can be used to measure the significance of the influence of each coefficient on the overlay error. Specifically, for each coefficient k j , the following hypothesis test can be performed:

[0067] Original assumption H0: k j =0, in this case, it means the coefficient k j There is no significant effect on the overlay error; alternative hypothesis H a :kj ≠0, in this case, it means the coefficient k j There is a significant impact on the overlay error.

[0068] The P-value is a concept used in hypothesis testing in statistics to measure the probability of a set of data occurring when the null hypothesis is true. A small P-value indicates that the observed data has a low probability of occurring when the original hypothesis is true. In this case, the original hypothesis can be rejected and the alternative hypothesis can be accepted. A large P-value indicates that the data is consistent with the original hypothesis, and there is insufficient evidence to reject the original hypothesis.

[0069] The P value can be calculated by the t-test, t statistic t j It can be expressed as:

[0070]

[0071] in, is the estimated coefficient k j The numerical value of is the coefficient k j The standard deviation of .

[0072] Based on the t distribution and t value, the coefficient k can be calculated j Corresponding P value: P-value = 2×prob(T>|t j |). That is, the P value is T>|t j |Probability.

[0073] In order to express the coefficient k more intuitively j The significance level of the overlay error can be measured by introducing the LogWorth value and converting the P value into a logarithmic scale: LogWorth = -log 10 (P-value).

[0074] For each compensation scheme, the LogWorth calculated is selected, and the parameter k with LogWorth>1.3 is selected. j To simplify the model, all parameters k that have a significant impact on the overlay error are j As the error compensation parameter, the polynomial terms corresponding to all error compensation parameters are summarized as the key polynomial terms that affect the actual overlay error.

[0075] S103: Determine a target compensation scheme based on the error compensation parameter and a functional relationship between the compensation scheme and the error compensation parameter.

[0076] The compensation scheme includes compensation thermal doses corresponding to at least 20 heat input areas and compensation stresses corresponding to multiple stress compensation points.

[0077] like Figure 2 As shown, this figure is a schematic diagram of an overlay error compensation mechanism provided in an embodiment of the present application. A lithographic light source (Lithographic light source) illuminates the mask (Mask), and the light is further irradiated to the surface of the wafer (Wafer) through a projection lens (Projection lens), thereby forming a lithographic pattern on the photoresist on the surface of the wafer. In an embodiment of the present application, in order to perform overlay error compensation, the mask can be divided into at least 20 heat input (Heat input) areas, so that pixel level heat (Pixel level heat) can be provided to each heat input area respectively, and at least 20 thermal compensation schemes can be designed; a plurality of stress actuators can be arranged around the mask, so that peripheral stress (Peripheral stress) can be applied to the mask through the stress actuator, and a variety of stress compensation schemes can be designed.

[0078] For example, the mask can be divided into 143 heat input areas, and the 143 heat input areas can be arranged into an equally spaced square matrix with 11 heat input areas in the horizontal direction and 13 heat input areas in the vertical direction, where each heat input area can be a rectangle with a length of 3 mm and a width of 2 mm; 16 stress actuators can be set around the mask, and every 4 stress actuators are set on the same side of the mask, so that 16 stress compensation schemes for the hinges on all sides that provide peripheral stress are designed under the premise of satisfying the basic principles of elastic deformation and torque balance of the mask.

[0079] It is understandable that the number and size of the heat input areas can be flexibly set according to the needs and the capabilities of the local heating system. For example, the size of the heat input area can be reduced and the heat input area can be set to a rectangle with a length of 1.5 mm and a width of 1 mm, and the number of heat input areas can be increased accordingly so that the array composed of all heat input areas can cover the entire mask.

[0080] As an example, a statistical analysis of the functional relationships between all compensation schemes and error compensation parameters can be performed to establish a functional relationship between the compensation schemes and the error compensation parameters. For example, for 143 thermal compensation schemes and 16 stress compensation schemes, statistical analysis can be used to determine the distribution of error compensation parameters corresponding to each compensation scheme. Through algorithmic optimization, the functional relationships between 159 compensation schemes and error compensation parameters can be derived.

[0081] The error compensation parameters are k1, k2,…, k 20 For example, the functional relationship between the 159 compensation schemes and the error compensation parameters is as follows:

[0082]

[0083] Among them, h1,h2,……,h 143 are the compensation thermal doses corresponding to the 143 heat input areas; f1, f2, ..., f 16 These are the compensation stresses at the stress compensation points corresponding to the 16 stress compensation schemes.

[0084] By utilizing the functional relationship between the compensation scheme and the error compensation parameters, the compensation model can simulate and calculate the compensation amount required to reduce the overlay error based on the measured overlay error data, derive the compensation requirements for each heat input area and stress compensation point, and determine the target compensation scheme.

[0085] S104: Based on the target compensation scheme, applying a compensation thermal dose to each heat input region of the mask, and applying a compensation stress to the stress compensation point of the mask.

[0086] As an example, the compensation thermal dose corresponding to each heat input region in the local target compensation scheme can be used to drive the local heating system to apply the compensation thermal dose to each heat input region of the mask.

[0087] The local heating system can include a digital micro-mirror array (DMD), a heating light source, and an optical system. The DMD is a micro-electromechanical system (MEMS) device consisting of millions of tiny tiltable mirrors, each of which can be independently controlled to control the distribution of the heating beam, thereby achieving local heating. The heating light source can be an ultraviolet (UV) light source or a deep ultraviolet (DUV) light source. The optical system includes lenses, reflectors, and apertures to focus the light from the light source onto the DMD and project the light reflected by the DMD onto the wafer surface.

[0088] Based on the compensation thermal dose corresponding to each heat input area in the target compensation scheme, a heating pattern can be determined; then, based on the heating pattern, the optical system can be driven to modulate the heating light source and focus the heating light source on each micromirror in the digital micromirror array; the reflection direction and intensity of the heating light source are adjusted by the digital micromirror array, and the modulated heating light source is modulated into a specific light intensity distribution according to the heating pattern and reflected onto the mask, so as to apply a compensation thermal dose to each heat input area of ​​the mask, thereby changing the thermal expansion shape of the mask through local heating and correcting the overlay error.

[0089] Optionally, after applying a compensating thermal dose to each heat input region of the reticle, a temperature sensor can be used to obtain the current temperature of each heat input region. Based on the current temperature of each heat input region and the target temperature of each heat input region after applying the compensating thermal dose, the state of each micromirror in the digital micromirror array is dynamically adjusted to bring the current temperature closer to the target temperature. For example, a proportional-integral-derivative (PID) control algorithm can be used to dynamically adjust the state of each micromirror in the digital micromirror array based on feedback signals from the temperature sensor to precisely control the local heating process. The target temperature can be calculated based on the initial temperature of the reticle before overlay error compensation and the thermal compensation dose corresponding to each heat input region in the target compensation scheme.

[0090] As an example, the stress actuator may be driven based on the compensation stress corresponding to each stress compensation point in the target compensation solution to apply the compensation stress to the stress compensation point of the mask.

[0091] Through thermal compensation and stress compensation, the overlay error caused by factors such as thermal effects, stress changes, mask errors, process fluctuations and environmental fluctuations in the lithography process can be effectively dealt with. The compensation scheme can be dynamically adjusted according to the latest overlay error distribution data. Even under extreme process conditions, the high stability and reliability of the lithography process can be guaranteed, ensuring that the lithography process can achieve the predetermined accuracy.

[0092] Therefore, in the embodiment of the present application, the compensation stress required to compensate for the overlay error and the compensation thermal dose corresponding to each of at least 20 heat input areas are obtained based on the overlay error distribution data, thereby realizing stress compensation and pixel-level thermal compensation of the mask to cause deformation of the mask, thereby accurately compensating for the overlay error existing in the lithography process, which can effectively reduce the overlay error of the lithography process, improve the lithography accuracy, realize high-precision pattern transfer for small feature size patterns, improve product reliability and yield, and reduce large-scale production costs.

[0093] In addition, the compensation method for lithography process overlay error provided in the embodiment of the present application can be applied to various lithography technologies such as extreme ultraviolet lithography (EUVL), deep ultraviolet lithography (DUVL), nanoimprint lithography (NIL), surface plasmon lithography (SPL), etc., and has strong versatility. Whether in the field of high-precision semiconductor manufacturing or in the field of micro-nano structure processing, it can provide a high-precision overlay error compensation solution based on thermal compensation and stress compensation to meet the needs of different processes and equipment.

[0094] The following is an example of compensation for overlay error in the photolithography process provided in this application:

[0095] See also Figure 3, This figure is a distribution vector diagram of overlay error provided by the embodiment of the present application, and the overlay error of each point in the field is The distribution is displayed in the form of a vector diagram, and the overlay error |mean|+3σ in the X and Y directions is marked in the vector diagram. The overlay error in the X direction can be recorded as OVLx, and the overlay error in the Y direction can be recorded as OVLy. This more intuitively shows the distribution of overlay error and helps technicians quickly understand the overlay error that will be caused by lithography under current conditions. Figure 3 (a) is the original overlay error distribution vector diagram, and the corresponding instance is denoted as instance 1; Figure 3 (b) is the overlay error distribution vector diagram with only high-order terms, and the corresponding example is recorded as Example 2. The high-order terms refer to the cubic terms in the cubic polynomial used to express the relationship between the overlay error and the position coordinates.

[0096] Will Figure 3 The overlay error distribution vector diagram shown is input into the compensation model, which then executes steps S101 to S104 to automatically calculate and execute a target compensation solution that minimizes the overlay error based on the overlay error distribution data. The overlay error compensation calculation can be accurate to the nanometer level.

[0097] After obtaining the target compensation scheme, the compensation model can draw the heating image of the compensated thermal dose corresponding to each heat input area according to the target compensation scheme (such as Figure 4 ) and the stress distribution table of the compensation stress corresponding to each stress compensation point (such as Figure 5 ) to visually demonstrate the compensation needs of different areas. Figure 4 (a) is the heating image corresponding to Example 1, Figure 4 Middle (b) is the heating image corresponding to Example 2.

[0098] The compensation model can then be based on Figure 4 The heating images shown, and Figure 5 The stress distribution table shown is plotted as Figure 6 The overlay error compensation vector diagram is shown to facilitate the evaluation of the compensation effect of the compensation scheme on the overlay error. Figure 6 (a) is the vector diagram of the overlay error compensation corresponding to Example 1; Figure 6 (b) is the vector diagram of the overlay error compensation corresponding to Example 2. If the compensation effect is not ideal, the target compensation scheme can be re-determined through the compensation model until the compensation accuracy reaches the expected level.

[0099] After completing the compensation for the overlay error of the lithography process, the lithography results of the wafers of the current batch that have undergone the lithography process can be measured to confirm whether the actual compensation effect has reached the expected target. At the same time, through the analysis and measurement of the lithography accuracy of the current batch, the effectiveness of the target compensation scheme can be further evaluated, and through steps S101 to S104, the compensation model can be adjusted based on the current compensation effect to continuously optimize the compensation model.

[0100] Optionally, the historical overlay error distribution data of multiple executions of the lithography process can be combined to analyze the trend of changes in the residual overlay error after multiple overlay error compensations, predict the possible overlay error range and compensation requirements for the next batch, adjust parameters in the compensation model such as the compensation thermal dose and compensation stress, optimize the target compensation scheme for the next overlay error compensation, and improve the overlay error compensation effect.

[0101] In order to verify the overlay error compensation effect after executing the target compensation scheme, the overlay errors after compensation of Example 1 and Example 2 were measured point by point, and the following results were obtained: Figure 7 The overlay residual distribution vector diagram is shown. Figure 7 (a) is the overlay residual distribution vector corresponding to Example 1; Figure 7 (b) is the overlay residual distribution vector diagram corresponding to Example 2. It can be seen that in Example 1, the overlay error in the X direction is reduced from 39.6047nm to 0.69671nm, and 98.24% of the overlay error is compensated. The overlay error in the Y direction is reduced from 28.3453nm to 0.55769nm, and 98.03% of the overlay error is compensated. In Example 2, the overlay error in the X direction is reduced from 3.2387nm to 0.58615nm, and 81.90% of the overlay error is compensated. The overlay error in the Y direction is reduced from 3.7295nm to 0.4935nm, and 86.77% of the overlay error is compensated.

[0102] By using the method for compensating the overlay error of the lithography process provided in the embodiment of the present application, 24 overlay error compensations are performed on the original overlay error. The compensation effect in the X direction is as follows: Figure 8 As shown in Figure 2, the average compensation efficiency can reach 98.05%. The compensation effect in the Y direction is as follows: Figure 9 As shown in the figure, the average compensation efficiency can reach 98.11%. The superposition error |mean|+3σ can be reduced to below 1nm, significantly improving the reliability of circuit connections in semiconductor devices and meeting the precision requirements of advanced process nodes.

[0103] As an example, in each embodiment of the present application, the photolithography process may specifically include the following steps:

[0104] S1: The photoresist-coated wafer is placed on the wafer stage within the lithography machine using a robotic arm. A suction cup or vacuum suction method can be used to secure the wafer to prevent displacement during exposure. The reticle is then placed on the mask stage within the lithography machine using a robotic arm. A mechanical clamp or vacuum suction method can be used to secure the reticle to prevent displacement or deformation during exposure. The patterned surface of the reticle faces the wafer surface and is aligned with the axis of the light source.

[0105] After the wafer and reticle are placed in the lithography machine, the machine's alignment system must align the wafer and reticle. For example, the system might first adjust the wafer position to achieve initial alignment with the wafer stage; then adjust the reticle position to achieve initial alignment with the reticle stage; and finally, align the wafer and reticle.

[0106] The alignment between the wafer and the reticle can be performed first through coarse alignment, followed by fine alignment. Coarse alignment typically requires only two alignment marks, such as two widely spaced alignment marks on the wafer. Fine alignment requires multiple alignment marks, such as at least 20. By locating multiple alignment marks, the alignment system can calculate the exact position of the wafer and reticle during exposure, minimizing overlay errors.

[0107] S2: The wafer coated with photoresist is exposed to light by the light source in the photolithography machine. The photoresist undergoes a chemical reaction under the light and forms a corresponding photolithography pattern according to the pattern of the mask.

[0108] S3: Place the wafer in a developer to remove the exposed photoresist (positive photoresist) or the unexposed photoresist (negative photoresist) to obtain a photoresist mask.

[0109] Among them, the lithography machine is a key tool for performing the lithography process. The appropriate type of lithography machine can be selected according to the type of lithography technology used. For example, the corresponding type of lithography machine can be selected for lithography processes such as extreme ultraviolet lithography (EUVL), deep ultraviolet lithography (DUVL), nanoimprint lithography (NIL) or surface plasma lithography (SPL). The lithography machine needs to operate in a clean room environment and be equipped with a high-precision alignment system to ensure precise docking between the mask and the wafer. During the operation of the lithography machine, the environmental conditions such as temperature, humidity and pressure of the environment in which the lithography machine is located need to be strictly controlled to avoid the impact of environmental changes on the lithography accuracy.

[0110] A reticle is a precise, high-resolution template typically made of a stable, heat-resistant material like quartz or glass. The reticle contains micron- or submicron-scale patterns. During the photolithography process, a light source illuminates the reticle in a lithography machine, transferring the pattern from the reticle to the photoresist on the side of the reticle facing away from the light source, creating the corresponding pattern.

[0111] The wafer can be a finely processed semiconductor substrate; the wafer surface can be polished or cleaned to remove surface impurities or oxide layers, thereby ensuring that the wafer surface cleanliness is within the process tolerances; the semiconductor substrate is made of silicon, germanium, quartz glass, or other semiconductor materials; the photoresist on the wafer surface can be applied by methods such as spin coating, ensuring that the thickness of the applied photoresist layer is uniform and within the process tolerances. Optionally, before applying the photoresist to the wafer surface, a layer of auxiliary transition material or anti-reflective coating can be pre-applied to the wafer surface to reduce the impact of reflected light on the exposure effect.

[0112] See also Figure 10 , this figure is a schematic diagram of a compensation device for overlay error in a photolithography process provided by an embodiment of the present application, the device comprising: an acquisition module 1001, a parameter determination module 1002, a solution determination module 1003 and a compensation module 1004;

[0113] An acquisition module 1001 is used to acquire overlay error distribution data under current lithography conditions;

[0114] A parameter determination module 1002 is configured to determine estimated values ​​of coefficients of each term in a cubic polynomial based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates, thereby obtaining error compensation parameters.

[0115] A scheme determination module 1003 is configured to determine a target compensation scheme based on the error compensation parameter and a functional relationship between the compensation scheme and the error compensation parameter; the compensation scheme includes a compensation thermal dose corresponding to each of at least 20 heat input regions and a compensation stress corresponding to each of a plurality of stress compensation points;

[0116] The compensation module 1004 is configured to apply a compensation thermal dose to each heat input region of the mask and apply a compensation stress to a stress compensation point of the mask based on a target compensation scheme.

[0117] Therefore, in the embodiment of the present application, the compensation stress required to compensate for the overlay error and the compensation thermal dose corresponding to each of at least 20 heat input areas are obtained based on the overlay error distribution data, thereby realizing stress compensation and pixel-level thermal compensation of the mask to cause deformation of the mask, thereby accurately compensating for the overlay error existing in the lithography process, which can effectively reduce the overlay error of the lithography process, improve the lithography accuracy, realize high-precision pattern transfer for small feature size patterns, improve product reliability and yield, and reduce large-scale production costs.

[0118] Optionally, the compensation module 1004 is specifically used to determine a heating pattern based on the compensation thermal dose corresponding to each heat input area in the target compensation scheme; based on the heating pattern, drive the optical system to modulate the heating light source, and drive the digital micromirror array to reflect the modulated heating light source onto the mask to apply a compensation thermal dose to each heat input area of ​​the mask.

[0119] Optionally, the parameter determination module 1002 is specifically configured to determine estimated values ​​of coefficients in the cubic polynomial by least squares method based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates, thereby obtaining error compensation parameters.

[0120] In some embodiments, the device for compensating for overlay errors in a lithography process further includes a temperature adjustment module for obtaining the current temperature of each heat input area through a temperature sensor; based on the current temperature of each heat input area and the target temperature of each heat input area after applying a compensating thermal dose, the state of each micromirror in the digital micromirror array is dynamically adjusted so that the current temperature approaches the target temperature.

[0121] In addition, the present application also provides a lithography machine, including a controller, a stress actuator, and a local heating system;

[0122] a controller electrically connected to the stress actuator and the local heating system;

[0123] A controller is used to drive the stress actuator to apply compensating stress to the stress compensation points of the mask according to the method for compensating overlay errors in the lithography process provided in any of the above embodiments, and to drive the local heating system to apply compensating thermal doses to various heat input areas of the mask.

[0124] The local heating system includes a digital micromirror array, a heating light source, and an optical system. In response to a controller drive, the local heating system modulates the heating light source through the optical system, focuses the heating light source onto each micromirror in the digital micromirror array, and reflects the modulated heating light source onto the reticle through the digital micromirror array to apply a compensating thermal dose to each heat input area of ​​the reticle.

[0125] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments. The device and system embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components indicated as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art can understand and implement it without expending creative work.

[0126] The above is merely one specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for compensating overlay error in a photolithography process, characterized in that: The method comprises: Obtaining overlay error distribution data; Based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates, determining estimated values ​​of coefficients of each term in the cubic polynomial to obtain error compensation parameters; Determining a target compensation scheme based on the error compensation parameter and a functional relationship between the compensation scheme and the error compensation parameter; the compensation scheme includes a compensation thermal dose corresponding to each of at least 20 heat input areas and a compensation stress corresponding to each of a plurality of stress compensation points; Based on the target compensation scheme, a compensation thermal dose is applied to each heat input region of the mask, and a compensation stress is applied to the stress compensation point of the mask.

2. The method according to claim 1, characterized in that Applying a compensation thermal dose to each heat input area of ​​the mask based on the target compensation scheme includes: determining a heating pattern based on the compensated thermal doses corresponding to the respective heat input areas in the target compensation scheme; Based on the heating pattern, the optical system is driven to modulate the heating light source, and the digital micromirror array is driven to reflect the modulated heating light source onto the mask, so as to apply a compensation thermal dose to each heat input area of ​​the mask.

3. The method according to claim 2, characterized in that After driving the optical system to modulate the heating light source based on the heating pattern, and driving the digital micromirror array to reflect the modulated heating light source onto the reticle to apply a compensating thermal dose to each heat input area of ​​the reticle, the method further includes: Obtain the current temperature of each heat input area through the temperature sensor; Based on the current temperature of each heat input area and the target temperature of each heat input area after applying the compensation thermal dose, the state of each micromirror in the digital micromirror array is dynamically adjusted so that the current temperature approaches the target temperature.

4. The method according to claim 1, wherein The number of the heat input areas is 143.

5. The method according to claim 4, characterized in that The 143 heat input areas are arranged in an equally spaced square matrix with 11 heat input areas in the horizontal direction and 13 heat input areas in the vertical direction.

6. The method according to claim 1, characterized in that The heat input area is a rectangle with a length of 3 mm and a width of 2 mm.

7. The method according to claim 1, characterized in that Determining estimated values ​​of coefficients of each term in the cubic polynomial based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates to obtain error compensation parameters includes: Based on the overlay error distribution data and a pre-established cubic polynomial for expressing the relationship between the overlay error and the position coordinates, estimated values ​​of coefficients in the cubic polynomial are determined by the least squares method to obtain error compensation parameters.

8. A device for compensating overlay error in a photolithography process, characterized in that: The device includes: an acquisition module, a parameter determination module, a solution determination module and a compensation module; The acquisition module is used to acquire overlay error distribution data under current lithography conditions; The parameter determination module is configured to determine, based on the overlay error distribution data and a pre-established cubic polynomial for representing the relationship between the overlay error and the position coordinates, estimated values ​​of coefficients of each term in the cubic polynomial to obtain error compensation parameters; The scheme determination module is configured to determine a target compensation scheme based on the error compensation parameter and a functional relationship between the compensation scheme and the error compensation parameter; the compensation scheme includes a compensation thermal dose corresponding to each of at least 20 heat input areas and a compensation stress corresponding to each of a plurality of stress compensation points; The compensation module is used to apply a compensation thermal dose to each heat input area of ​​the mask and apply a compensation stress to the stress compensation point of the mask based on the target compensation scheme.

9. A photolithography machine, characterized in that: The photolithography machine includes: a controller, a stress actuator and a local heating system; The controller is electrically connected to the stress actuator and the local heating system; The controller is used to drive the stress actuator to apply compensating stress to the stress compensation points of the mask according to the method for compensating overlay errors in a lithography process according to any one of claims 1 to 7, and to drive the local heating system to apply compensating thermal doses to various heat input areas of the mask.

10. The photolithography machine according to claim 9, characterized in that: The local heating system includes a digital micromirror array, a heating light source and an optical system; The local heating system is used to respond to the drive of the controller, modulate the heating light source through the optical system, focus the heating light source on each micromirror in the digital micromirror array, and reflect the modulated heating light source onto the mask through the digital micromirror array to apply a compensating thermal dose to each heat input area of ​​the mask.

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