Photomask position accuracy compensation method
Patent Information
- Application Number
- CN202611332392.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-31
- Publication Date
- 2026-10-13
AI Technical Summary
然而，在被拆分的多张独立光掩模的制造环节中，现行的光掩模位置精度控制范式，在制造阶段仅针对单一光掩模相对于其设计基准进行独立的精度校正，完全忽略了多张光掩模之间（即层与层之间）潜在的相对位置误差
[0025]在本发明提供的光掩模位置精度补偿方法中，提供前层光掩模，采集前层光掩模的位置精度数据，并根据前层光掩模的位置精度数据构建前层光掩模的位置精度模型；根据前层光掩模的位置精度模型获得后层光掩模的补偿参考量；提供补偿强度系数和误差传递权重系数，根据补偿强度系数、误差传递权重系数和后层光掩模的补偿参考量获得后层光掩模的补偿修正量；将后层光掩模的补偿修正量导入曝光控制系统中，并利用曝光控制系统制备后层光掩模时进行位置精度补偿，以制备获得后层光掩模。本发明中采集前层光掩模的实际位置精度数据，前层光掩模的实际位置精度数据带有真实误差信息，将实际位置精度数据作为后层光掩模的对准基准，实现层级误差传递补偿，避免全局线性对准带来的残留误差，提高前层光掩模和后层光掩模之间的对准精度，并引入补偿强度系数和误差传递权重系数，在逐层误差传递补偿过程中避免过补偿，进一步提高补偿精度。
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Figure CN122902157A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for compensating for the positional accuracy of a photomask. Background Technology
[0002] In multi-exposure processes, a complex circuit pattern is typically broken down into multiple independent photomasks, which are then precisely stitched together through multiple exposure and etching steps to form the final target pattern. This "split-stitch" approach makes the overlay accuracy between each exposure a core factor determining the final product yield. However, in the manufacturing process of these multiple independent photomasks, current photomask position accuracy control paradigms only perform independent accuracy correction on a single photomask relative to its design baseline during the manufacturing stage, completely ignoring the potential relative positional errors between multiple photomasks (i.e., between layers).
[0003] Therefore, in the manufacturing process of multi-exposure masks where the interlayer overlay accuracy is extremely high, establishing and implementing a method for controlling the interlayer overlay accuracy of the photomask itself is a key and necessary step to improve the yield of the final product and break through the bottleneck of advanced processes. Summary of the Invention
[0004] The purpose of this invention is to provide a method for compensating the positional accuracy of photomasks, thereby achieving layer error propagation compensation and improving the alignment accuracy between the front and back photomasks.
[0005] To achieve the above objectives, the present invention provides a method for compensating the positional accuracy of a photomask, comprising:
[0006] A front-layer photomask is provided, positional accuracy data of the front-layer photomask is collected, and a positional accuracy model of the front-layer photomask is constructed based on the positional accuracy data of the front-layer photomask.
[0007] The compensation reference value of the back photomask is obtained based on the positional accuracy model of the front photomask.
[0008] Provide a compensation intensity coefficient and an error propagation weighting coefficient, and obtain the compensation correction amount of the back-layer photomask based on the compensation intensity coefficient, the error propagation weighting coefficient, and the compensation reference amount of the back-layer photomask; and,
[0009] The compensation correction amount of the back photomask is introduced into the exposure control system, and the position accuracy compensation is performed when the back photomask is prepared using the exposure control system, so as to prepare the back photomask.
[0010] Optionally, the position accuracy data includes X-direction offset, Y-direction offset, rotation error, scaling error, orthogonality deviation, and local nonlinear distortion.
[0011] Optionally, the front photomask has multiple measurement points, and the positional accuracy data of some of the measurement points is collected as the positional accuracy data of the front photomask.
[0012] Optionally, when collecting positional accuracy data of some of the measurement points, the step of obtaining the compensation reference value of the rear photomask based on the positional accuracy model of the front photomask includes:
[0013] Interpolation and coordinate mapping are performed in the position accuracy model of the front photomask to obtain the position accuracy data of all the measurement points;
[0014] All measurement points on the front photomask are used as alignment reference points for the back photomask. The positional accuracy data of each measurement point is used as the compensation reference value of the corresponding alignment reference point. All the compensation reference values of the alignment reference points are used as the compensation reference values of the back photomask.
[0015] Optionally, the compensation strength coefficient is taken as 0.5 to 1.5.
[0016] Optionally, the formula for the error propagation weighting coefficient is W. N =e -k*(N-1) Where k is the attenuation factor, with a value ranging from 0.1 to 0.5, N is the layer of the back photomask, and W N The error propagation weighting coefficient for the back-layer photomask.
[0017] Optionally, the farther the layer of the back photomask is from the layer of the front photomask, the larger the value of k; the closer the layer of the back photomask is to the layer of the front photomask, the smaller the value of k.
[0018] Optionally, the product of the compensation intensity coefficient, the error propagation weighting coefficient, and the compensation reference amount of the back-layer photomask can be used as the compensation correction amount of the back-layer photomask.
[0019] Optionally, after preparing the back photomask, the process further includes:
[0020] Collect the positional accuracy data of the back-layer photomask;
[0021] Determine whether the positional accuracy data of the back-layer photomask exceeds a preset tolerance range. If it does, adjust the compensation intensity coefficient or the error propagation weighting coefficient.
[0022] Optionally, after preparing the back photomask, the process further includes:
[0023] Measure the overlay error between the rear photomask and the front photomask;
[0024] Determine whether the overlay error is greater than a preset overlay error. If it is greater than the preset overlay error, then feed the overlay error back to the position accuracy model of the front photomask.
[0025] In the photomask position accuracy compensation method provided by this invention, a front-layer photomask is provided, position accuracy data of the front-layer photomask is collected, and a position accuracy model of the front-layer photomask is constructed based on the position accuracy data of the front-layer photomask; a compensation reference amount for the back-layer photomask is obtained based on the position accuracy model of the front-layer photomask; a compensation intensity coefficient and an error propagation weight coefficient are provided, and a compensation correction amount for the back-layer photomask is obtained based on the compensation intensity coefficient, the error propagation weight coefficient, and the compensation reference amount of the back-layer photomask; the compensation correction amount of the back-layer photomask is imported into the exposure control system, and position accuracy compensation is performed when the back-layer photomask is prepared using the exposure control system, so as to prepare and obtain the back-layer photomask. In this invention, the actual positional accuracy data of the front-layer photomask is collected. This data contains real error information. The actual positional accuracy data is used as the alignment reference for the back-layer photomask to achieve layer-by-layer error propagation compensation, avoid residual errors caused by global linear alignment, improve the alignment accuracy between the front-layer and back-layer photomasks, and introduce compensation intensity coefficient and error propagation weight coefficient to avoid overcompensation during the layer-by-layer error propagation compensation process, thereby further improving the compensation accuracy. Attached Figure Description
[0026] Figure 1 This is a flowchart of a photomask position accuracy compensation method provided in an embodiment of the present invention. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The accompanying drawings are all in a very simplified form and are not drawn to scale, only used to conveniently and clearly assist in illustrating the objectives of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structures; in particular, different proportions are sometimes used because different drawings need to show different focuses.
[0028] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
[0029] In the description of this application, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are used only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the equipment or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.
[0030] Furthermore, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.
[0031] Figure 1 This is a flowchart illustrating a photomask position accuracy compensation method provided in this embodiment. Please refer to... Figure 1 This embodiment provides a method for compensating the positional accuracy of a photomask, including:
[0032] Step S1: Provide a front-layer photomask, collect the positional accuracy data of the front-layer photomask, and construct a positional accuracy model of the front-layer photomask based on the positional accuracy data of the front-layer photomask;
[0033] Step S2: Obtain the compensation reference value of the back photomask based on the position accuracy model of the front photomask;
[0034] Step S3: Provide the compensation intensity coefficient and the error propagation weight coefficient, and obtain the compensation correction amount of the back layer photomask based on the compensation intensity coefficient, the error propagation weight coefficient and the compensation reference amount of the back layer photomask;
[0035] Step S4: The compensation correction amount of the back photomask is imported into the exposure control system, and the position accuracy compensation is performed when the back photomask is prepared using the exposure control system, so as to prepare the back photomask.
[0036] The following is a detailed description of a photomask position accuracy compensation method provided in this embodiment.
[0037] Step S1: In multiple exposure technology, a complex or high-precision circuit pattern (multiple pattern) is typically divided into multiple independent photomasks with hierarchical relationships, and these photomasks are then fabricated separately. Each photomask is generally fabricated based on a design reference, ignoring the relative positional errors between layers. Therefore, this embodiment uses the positional accuracy data of the previous photomask to achieve positional accuracy transfer compensation between layers, thereby enabling positional accuracy compensation when fabricating subsequent photomasks. In this embodiment, a circuit pattern (multiple pattern) is divided into multiple independent photomasks with hierarchical relationships. For example, a circuit pattern is divided into three independent photomasks with hierarchical relationships: a first-layer photomask, a second-layer photomask, and a third-layer photomask. The circuit pattern is obtained by sequentially exposing the first-layer photomask, the second-layer photomask, and the third-layer photomask.
[0038] A front-layer photomask is provided. For example, the front-layer photomask can be the first layer among multiple photomasks. During exposure, the first-layer photomask is exposed first to obtain the pattern. Therefore, the front-layer photomask is first prepared according to the design reference. During preparation, actual positional errors generally occur. Considering the relative positional error between the front-layer and rear-layer photomasks, the actual positional accuracy data of the front-layer photomask is used as the alignment reference for the preparation of the rear-layer photomask. The front-layer and rear-layer photomasks constitute a multi-pattern photomask. The positional accuracy data of the front-layer photomask is collected. Specifically, the front-layer photomask has multiple measurement points, which are evenly distributed on the front-layer photomask. The positional accuracy data of some measurement points is collected. Since the number of measurement points is large, partial collection can significantly save collection time. The collected positional accuracy data of the measurement points is used as the positional accuracy data of the front-layer photomask. In this embodiment, the position accuracy data includes X-direction offset, Y-direction offset, rotation error, scaling error, orthogonality deviation, and local nonlinear distortion. Each measurement point has position accuracy data of the above items, but is not limited to the above data.
[0039] Furthermore, a positional accuracy model of the front-layer photomask is constructed based on the positional accuracy data of the front-layer photomask. The positional accuracy model of the front-layer photomask includes the positional accuracy data of the collected measurement points. The positional accuracy model of the front-layer photomask is stored in the form of a discrete grid or a continuous function for easy subsequent use.
[0040] Step S2: Obtain the compensation reference value of the back optical mask based on the positional accuracy model of the front optical mask. Specifically, when collecting positional accuracy data of some measurement points, the positional accuracy model of the front optical mask is called, and interpolation and coordinate mapping are performed in the positional accuracy model of the front optical mask. Since only some positional accuracy data of measurement points were collected in step S1, the positional accuracy model only includes the positional accuracy data of the collected measurement points. It is also necessary to obtain the positional accuracy data of the uncollected measurement points. Therefore, interpolation and coordinate mapping are performed in the positional accuracy model of the front optical mask. For example, interpolation and coordinate mapping are performed based on the positional accuracy data of two adjacent collected measurement points to obtain the positional accuracy data of the uncollected measurement points between the two adjacent collected measurement points. That is, the positional accuracy data of the uncollected measurement points is obtained by interpolation and coordinate mapping in the positional accuracy model of the front optical mask, thereby obtaining the positional accuracy data of all measurement points. Furthermore, all measurement points on the front photomask are used as alignment reference points for the back photomask. The positional accuracy data of each measurement point is used as the compensation reference value of the corresponding alignment reference point, and the compensation reference values of all alignment reference points are used as the compensation reference values of the back photomask.
[0041] In this embodiment, the actual positional accuracy data of the prepared front-layer photomask contains real error information. The actual positional accuracy data is used as the alignment reference for the back-layer photomask to achieve layer error propagation compensation, avoid residual errors caused by global linear alignment (aligning with the design reference each time) (avoiding error accumulation), and effectively reduce the relative error between the front-layer and back-layer photomasks.
[0042] Step S3: If the compensation reference value of the back-layer photomask obtained in step S2 is used directly for compensation, compensation accuracy issues may occur, such as overcompensation or undercompensation. Therefore, a compensation intensity coefficient and an error propagation weighting coefficient are needed to correct the compensation reference value of the back-layer photomask. The compensation intensity coefficient and error propagation weighting coefficient are provided. The compensation intensity coefficient ranges from 0.5 to 1.5, with a value of 1 indicating 100% compensation. The compensation intensity coefficient (empirical default value) is obtained through a feedforward control algorithm; for example, the initial compensation intensity coefficient is set to 1. The compensation intensity coefficient allows for predictive adjustment of the back-layer photomask's position parameters, such as the workpiece stage coordinates of the exposure equipment, the photomask rotation angle, the scaling factor, and the exposure field distortion correction coefficient.
[0043] The formula for the error propagation weighting coefficient is W. N =e -k*(N-1) Where e is the natural base (approximately 2.718), k is the attenuation factor, with a value ranging from 0.1 to 0.5, N is the layer of the subsequent photomask, i.e., the Nth photomask layer, and W NThis is the error propagation weighting coefficient for the Nth layer photomask (i.e., the back photomask). N can be less than or equal to 5, indicating that the multi-pattern photomask can be split into a maximum of 5 layers, but is not limited to this. The further the layer of the back photomask is from the layer of the front photomask, the larger the value of k; the closer the layer of the back photomask is to the layer of the front photomask, the smaller the value of k. For example, if the front photomask is layer 1 and the back photomask is layer 2 or layer 5, layer 2 is closest to the layer of the front photomask, and layer 5 is farthest from the layer of the front photomask. Therefore, when the back photomask is layer 2, it belongs to near-layer errors (such as layers 1-3 in the front), and high-weight compensation is used. That is, the closer the layer of the back photomask is to the layer of the front photomask, the smaller the value of k. N The larger the value of k, for example, k is less than or equal to 0.2. When the back layer photomask is the 5th layer, it belongs to the far-layer error (such as the first 3 layers or more) and is compensated with low weight. That is, the farther the layer level of the back layer photomask is from the layer level of the front layer photomask, the larger the value of k. N The smaller the value of k, for example, k is greater than 0.2. In the process of layer-by-layer error propagation, instead of passing all the errors of the previous optical mask to the subsequent optical mask for compensation, a weighted attenuation function is introduced to avoid overcompensation.
[0044] The compensation correction amount of the back-layer optical mask is obtained based on the compensation intensity coefficient, the error propagation weight coefficient, and the compensation reference amount of the back-layer optical mask. Specifically, the product of the compensation intensity coefficient, the error propagation weight coefficient, and the compensation reference amount of the back-layer optical mask is used as the compensation correction amount of the back-layer optical mask.
[0045] Step S4: The compensation correction amount of the back photomask is imported into the exposure control system. The compensation correction amount of the back photomask is the compensation correction amount of multiple alignment reference points. The position parameters of the alignment reference points when preparing the back photomask are compensated and corrected by the compensation correction amount of each alignment reference point. Then, the position accuracy compensation is performed when preparing the back photomask using the exposure control system, that is, the preparation is carried out according to the position parameters of the compensated alignment reference points to obtain the back photomask.
[0046] Further, after preparing the back-layer photomask, positional accuracy data of the back-layer photomask is collected. Specifically, positional accuracy data of the alignment reference points in the back-layer photomask is collected. This positional accuracy data includes X-direction offset, Y-direction offset, rotation error, scaling error, orthogonality deviation, and local nonlinear distortion. Each alignment reference point has positional accuracy data for the above items, but is not limited to the above data. It is determined whether the positional accuracy data of the back-layer photomask exceeds a preset tolerance range. If it does, the compensation intensity coefficient or error propagation weight coefficient is adjusted (selected according to actual needs). Specifically, if the positional accuracy data of the back-layer photomask negatively exceeds the preset tolerance range, it indicates that the compensation in step S4 is undercompensated, requiring an increase in the compensation intensity coefficient or a decrease in the error propagation weight coefficient; if the positional accuracy data of the back-layer photomask positively exceeds the preset tolerance range, it indicates that the compensation in step S4 is overcompensated, requiring a decrease in the compensation intensity coefficient or an increase in the error propagation weight coefficient. The above steps achieve real-time self-verification and rollback adjustment after the back-layer photomask is prepared.
[0047] Furthermore, after preparing the back-layer photomask, the method further includes: measuring the overlay error between the back-layer photomask and the front-layer photomask, determining whether the overlay error is greater than a preset overlay error, and if it is greater than the preset overlay error, feeding the overlay error back to the position accuracy model of the front-layer photomask to correct the position accuracy data of the measurement points in the position accuracy model, achieving reverse alignment and forming a closed-loop feedback with the forward layer compensation, thereby further improving the overall alignment accuracy between the multi-layer photomasks.
[0048] In summary, the photomask position accuracy compensation method provided by this invention includes: providing a front-layer photomask; collecting position accuracy data of the front-layer photomask; constructing a position accuracy model of the front-layer photomask based on the position accuracy data; obtaining a compensation reference value for the back-layer photomask based on the position accuracy model of the front-layer photomask; providing a compensation intensity coefficient and an error propagation weight coefficient; obtaining a compensation correction value for the back-layer photomask based on the compensation intensity coefficient, the error propagation weight coefficient, and the compensation reference value of the back-layer photomask; importing the compensation correction value of the back-layer photomask into the exposure control system; and using the exposure control system to perform position accuracy compensation when preparing the back-layer photomask to prepare and obtain the back-layer photomask. In this invention, the actual positional accuracy data of the front-layer photomask is collected. This data contains real error information. The actual positional accuracy data is used as the alignment reference for the back-layer photomask to achieve layer-by-layer error propagation compensation, avoid residual errors caused by global linear alignment, improve the alignment accuracy between the front-layer and back-layer photomasks, and introduce compensation intensity coefficient and error propagation weight coefficient to avoid overcompensation during the layer-by-layer error propagation compensation process, thereby further improving the compensation accuracy.
[0049] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.
Claims
1. A method for compensating the positional accuracy of a photomask, characterized in that, include: A front-layer photomask is provided, positional accuracy data of the front-layer photomask is collected, and a positional accuracy model of the front-layer photomask is constructed based on the positional accuracy data of the front-layer photomask. The compensation reference value of the back photomask is obtained based on the positional accuracy model of the front photomask. Provide a compensation intensity coefficient and an error propagation weight coefficient, and obtain the compensation correction amount of the back layer photomask based on the compensation intensity coefficient, the error propagation weight coefficient and the compensation reference amount of the back layer photomask; as well as, The compensation correction amount of the back photomask is introduced into the exposure control system, and the position accuracy compensation is performed when the back photomask is prepared using the exposure control system, so as to prepare the back photomask.
2. The photomask position accuracy compensation method as described in claim 1, characterized in that, The position accuracy data includes X-direction offset, Y-direction offset, rotation error, scaling error, orthogonality deviation, and local nonlinear distortion.
3. The photomask position accuracy compensation method as described in claim 1, characterized in that, The front photomask has multiple measurement points, and the positional accuracy data of some of the measurement points is collected as the positional accuracy data of the front photomask.
4. The photomask position accuracy compensation method as described in claim 3, characterized in that, When collecting positional accuracy data of some of the measurement points, the step of obtaining the compensation reference value of the rear optical mask based on the positional accuracy model of the front optical mask includes: Interpolation and coordinate mapping are performed in the position accuracy model of the front photomask to obtain the position accuracy data of all the measurement points; All measurement points on the front photomask are used as alignment reference points for the back photomask. The positional accuracy data of each measurement point is used as the compensation reference value of the corresponding alignment reference point. All the compensation reference values of the alignment reference points are used as the compensation reference values of the back photomask.
5. The photomask position accuracy compensation method as described in claim 1, characterized in that, The value of the compensation strength coefficient is 0.5 to 1.
5.
6. The photomask position accuracy compensation method as described in claim 1, characterized in that, The formula for the error propagation weighting coefficient is W. N =e -k*(N-1) Where k is the attenuation factor, with a value ranging from 0.1 to 0.5, N is the layer of the back photomask, and W N The error propagation weighting coefficient for the back-layer photomask.
7. The photomask position accuracy compensation method as described in claim 6, characterized in that, The farther the layer of the back photomask is from the layer of the front photomask, the larger the value of k; the closer the layer of the back photomask is to the layer of the front photomask, the smaller the value of k.
8. The photomask position accuracy compensation method as described in claim 1, characterized in that, The product of the compensation intensity coefficient, the error propagation weighting coefficient, and the compensation reference value of the back-layer photomask is used as the compensation correction amount of the back-layer photomask.
9. The photomask position accuracy compensation method as described in claim 1, characterized in that, After preparing the back-layer photomask, the process further includes: Collect the positional accuracy data of the back-layer photomask; Determine whether the positional accuracy data of the back-layer photomask exceeds a preset tolerance range. If it does, adjust the compensation intensity coefficient or the error propagation weighting coefficient.
10. The photomask position accuracy compensation method as described in claim 1, characterized in that, After preparing the back-layer photomask, the process further includes: Measure the overlay error between the rear photomask and the front photomask; Determine whether the overlay error is greater than a preset overlay error. If it is greater than the preset overlay error, then feed the overlay error back to the position accuracy model of the front photomask.