Method for compensating and correcting critical dimension uniformity of critical level

Abstract

The invention provides a method for correcting critical dimension uniformity of a critical level. The method comprises the following steps: acquiring critical dimension data of a photoetching mask, first critical dimension data after wafer development and before etching and second critical dimension data after etching; calculating a first compensation value for compensating the mask effect based on the key size data of the mask; calculating a second compensation value for compensating the etching process effect based on the first and second critical dimension data; and combining the first compensation value and the second compensation value to generate a final compensation value, and applying the final compensation value to subsequent photoetching exposure. According to the invention, error sources are split and respectively compensated, and the mask COA data and a small amount of etching deviation data are used for replacing large-scale online measurement, so that the measurement cost is remarkably reduced, the formula updating process after equipment maintenance is simplified, and the compensation precision and the production efficiency are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a method for correcting critical layer critical dimension uniformity. BACKGROUND

[0002] In the manufacturing process of semiconductor integrated circuits, with the continuous improvement of device integration and the continuous reduction of technology nodes, for example, the gate critical dimension (CD) of transistors in logic circuits is continuously reduced, and the accuracy requirements for size control in each process step are increasingly stringent. Among them, the within-wafer uniformity (CDU) of the critical dimension after the final etching after the patterning process is one of the key indicators that affect device performance and yield.

[0003] The critical dimension uniformity after the final etching is usually affected by multiple upstream factors, mainly including two aspects: first, the critical dimension non-uniformity of the photomask used in the photolithography process itself; second, the inherent process non-uniformity of the etching equipment (such as the etching chamber), such as the center-edge effect caused by plasma distribution, gas flow or temperature gradient.

[0004] In order to compensate for the influence caused by the above factors and improve the uniformity of the final CD, the existing technology usually adopts a dose mapper (DOMA) compensation scheme. Specifically, this scheme measures the CD data after the final etching by selecting a large number of measurement points (such as tens of thousands of points) on the wafer, then establishes a unified compensation model based on these massive measured data, and generates a dose map, which is applied in the subsequent photolithography exposure step of the wafer to adjust the exposure dose of different regions differently, thereby compensating for the non-uniformity of the CD.

[0005] However, the above-mentioned prior art scheme has the following defects: first, this scheme needs to perform large-scale on-line measurement of the wafer, which will occupy a large amount of expensive measurement equipment time, increasing production cost and time cost; second, when the etching equipment is routinely maintained, its etching rate or uniformity characteristics in the chamber may change, at which time it is necessary to repeat the aforementioned large-scale measurement and modeling process to update the compensation scheme, resulting in very cumbersome recipe maintenance work, slow response speed, lack of flexibility and efficiency. Therefore, the industry urgently needs a more efficient and lower maintenance cost CD uniformity correction method. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a method for correcting critical layer critical dimension uniformity, to solve the problem that the CDU compensation scheme in the prior art relies on large-scale on-line measurement, occupies a lot of time, has high cost, and the recipe is complicated to update after equipment maintenance.

[0007] To achieve the above object and other related objects, the present application provides a method for correcting critical dimension uniformity of a key layer, comprising:

[0008] Step one, obtaining critical dimension data of a photomask used by a wafer to be processed, and first critical dimension data of the wafer before etching after development and second critical dimension data of the wafer after etching;

[0009] Step two, calculating a first compensation value for compensating for self-effect of the photomask based on the critical dimension data of the photomask;

[0010] Step three, calculating a second compensation value for compensating for etching process effect based on the first critical dimension data and the second critical dimension data;

[0011] Step four, merging the first compensation value and the second compensation value to generate a final compensation value; and

[0012] Step five, applying the final compensation value to adjust exposure dose when performing photolithography exposure on a subsequent wafer.

[0013] Preferably, in step one, the critical dimension data of the photomask is derived from factory certification data of the photomask.

[0014] Preferably, in step two, the first compensation value is a first exposure dose map converted from a deviation between the critical dimension data of the photomask and a preset design value through a mask error enhancement factor.

[0015] Preferably, in step three, the second compensation value is a second exposure dose map converted from a difference between an actual etching deviation calculated from the first critical dimension data and the second critical dimension data and a target etching deviation.

[0016] Preferably, in step one, the first critical dimension data and the second critical dimension data are obtained by measuring a predetermined number of points in each exposure field on the wafer.

[0017] Preferably, the predetermined number of points is 5 points.

[0018] Preferably, in step four, the merging is superimposing a first exposure dose map represented by the first compensation value and a second exposure dose map represented by the second compensation value to generate the final compensation value.

[0019] Preferably, the method further comprises: after maintenance of the etching equipment used to generate the second compensation value, determining whether the etching process effect has changed by re-acquiring and comparing the first critical dimension data and the second critical dimension data; and when the etching process effect has not changed significantly, continuing to apply the final compensation value without recalculating the first compensation value.

[0020] As described above, the method for correcting critical layer critical dimension uniformity of the present application has the following beneficial effects:

[0021] 1. The present application compensates for errors introduced by the mask itself by using the factory certification data of the photomask, replacing the need for tens of thousands of final size measurements on wafers in the prior art. At the same time, only a small number of measurements of the sizes after development and etching are needed to calculate the etching process deviation. This greatly reduces the occupancy time of expensive measurement equipment, significantly reducing production costs and data collection cycles.

[0022] 2. The present application divides error sources into relatively fixed mask effects and possibly changing etching effects. When the etching equipment is maintained, only a small number of measurements are needed to quickly verify whether the etching deviation has changed. If there is no significant change, the entire compensation scheme does not need to be updated, and in particular, the first compensation value representing the mask effect does not need to be recalculated. This makes the later maintenance of the compensation formula very simple and fast, reduces the cost of human maintenance, and improves the flexibility and response speed of the production line.

[0023] 3. The present application realizes compensation for different error sources by modeling and compensating for the exposure field-level errors caused by the photomask and the wafer-level errors caused by the etching process. Compared to the traditional scheme of mixing all errors for processing, the physical meaning is clearer, and the compensation model is more targeted and accurate, thereby being able to more effectively improve the uniformity of the final critical dimension and enhance the device performance and yield. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A schematic diagram of the method for correcting critical layer critical dimension uniformity of the present application is shown. DETAILED DESCRIPTION

[0025] The embodiments of the present application are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure in the specification. The present application can also be implemented or applied through other different embodiments, and various modifications or changes can be made to the details in the specification without departing from the spirit of the present application.

[0026] The embodiment of the present application provides a method for correcting critical dimension uniformity of a key layer, which splits factors affecting final critical dimension uniformity (CDU) into self-effect of a photolithography mask and etching process effect, calculates compensation values for the two effects respectively, and finally combines the compensation values to generate a unified exposure dose adjustment scheme. Compared with a traditional hybrid compensation method, the method can more accurately and efficiently improve size uniformity of a key pattern on a semiconductor wafer. By using the method, dependence on online measurement data is reduced, production cost is reduced, a post-maintenance process of a process recipe is simplified, and process stability is enhanced.

[0027] Please refer to Figure 1 The method specifically comprises the following steps:

[0028] Step one, obtain critical dimension data of a photolithography mask used for processing a target wafer, and first critical dimension data of the wafer after development (ADI) and second critical dimension data of the wafer after etching (AEI). This step is a data preparation stage, which provides basic data for subsequent calculation of error compensation of different sources.

[0029] In some embodiments, in step one, the critical dimension data of the photolithography mask is obtained from Certificate of Analysis (COA) data of the photolithography mask. By using the COA data provided by a mask supplier, high-density and high-precision mask pattern size information can be obtained. This method replaces the practice of measuring tens of thousands of wafer measurement points on a production line in the traditional technology, fundamentally avoids the problem of occupying a large amount of time of expensive measurement equipment, greatly saves data acquisition cost and time, and directly obtains accurate data for compensation from the error source.

[0030] In some embodiments, in step one, the first critical dimension data and the second critical dimension data are obtained by measuring a predetermined number of points in each exposure field (shot) on the wafer.

[0031] In some embodiments, the predetermined number of points is 5 points. This sparse sampling measurement strategy, for example, measuring only 5 points in each exposure field, is sufficient to represent the systematic deviation of the wafer level introduced by the etching equipment, such as the center-edge effect. Compared with the full map measurement scheme of measuring 50 points or more in each exposure field in the prior art, the number of measurement points of the present application is greatly reduced, further reducing the measurement load and time cost, and improving the production efficiency.

[0032] Step two, based on the critical dimension data of the photomask, calculate the first compensation value for compensating the photomask self-effect. This step aims to precisely offset the CD non-uniformity at the shot level caused by the mask manufacturing tolerance.

[0033] In some embodiments, in step two, the first compensation value is a first exposure dose map converted from the deviation between the actual critical dimension recorded in the COA data of the photomask and the preset ideal design value, and through a mask error enhancement factor (MEEF). MEEF is a key physical quantity that characterizes the amplification of mask errors by the photolithography process. By introducing MEEF for conversion, it can be ensured that the calculated dose compensation can precisely offset the actual CD deviation caused by mask errors on the wafer, thereby achieving precise control of the CD distribution within the exposure field.

[0034] Step three, based on the first critical dimension data and the second critical dimension data, calculate the second compensation value for compensating the etching process effect. This step focuses on solving the wafer-level CD non-uniformity caused by the etching process itself, such as plasma density, gas flow field or temperature field non-uniformity in the etching chamber, etc.

[0035] In some embodiments, in step three, the second compensation value is a second exposure dose map converted from the difference between the actual etching deviation calculated from the first critical dimension data (ADI CD) and the second critical dimension data (AEI CD) and the target etching deviation. By directly measuring the change in CD before and after etching (i.e. etching deviation), the influence of the etching process on different regions of the wafer can be accurately quantified. Comparing this actual deviation map with the desired, uniform target deviation can generate a compensation dose map specifically for correcting etching non-uniformity.

[0036] Step four, merge the first compensation value and the second compensation value to generate the final compensation value. This step integrates the two compensation schemes calculated for the mask effect and the etching effect respectively, forming a comprehensive compensation scheme.

[0037] In some embodiments, the merging in step four is a numerical superposition of the first exposure dose map represented by the first compensation value and the second exposure dose map represented by the second compensation value to generate the final compensation value, which is embodied as a final, comprehensive exposure dose map (Dose Map). This merging method separately handles the error sources at the exposure field level (mask) and the wafer level (etching), achieving coordinated compensation of multi-source errors, with clear physical meaning and explicit compensation logic. Compared with the traditional compensation method of fitting the final CD, it has higher accuracy and robustness.

[0038] Step five, when the subsequent wafer is exposed to lithography, the final compensation value is applied to adjust the exposure dose. By loading the final generated compensation dose map into the exposure machine, the exposure machine can apply precisely adjusted exposure energy to different locations on the wafer, thereby pre-compensating the size deviation of the subsequent etching process and the mask version itself at the beginning of the pattern formation, and finally obtaining a highly uniform critical dimension.

[0039] The method of the embodiment of the present application further comprises: after the etching equipment used to generate the second compensation value is maintained, determining whether the etching process effect has changed by re-acquiring and comparing the first critical dimension data and the second critical dimension data; and when the etching process effect has not changed significantly (for example, the etching rate or the etching uniformity map has not changed), continuing to apply the final compensation value generated before without re-calculating the first compensation value. This is a significant advantage of the method of the present application. Since the first compensation value representing the mask effect is fixed, after the etching equipment is maintained, the maintenance personnel only need to perform a small amount of ADI-AEI deviation measurement to quickly determine whether the etching process characteristics have drifted. If there is no significant change, the entire compensation scheme does not need to be updated, thereby greatly simplifying the later maintenance work of the process recipe, avoiding tedious repeated modeling, reducing the cost of manual maintenance, and improving the response speed and adaptability of the production line to changes in the state of the equipment.

[0040] In a specific application case, the method provided by the present application is applied to CDU correction of a certain trench critical level. Before the method is applied, the measured wafer CD standard deviation (sigma) is 1.33 nm. After the split compensation scheme provided by the present application is applied, the measured wafer CD standard deviation is significantly reduced to 0.65 nm, with an improvement of 51.12%. This actual data powerfully proves the effectiveness of the method of the present application, indicating that the method can stably and reliably improve the size control precision of the critical level, which plays a crucial role in improving the electrical performance consistency, stability and final product yield of semiconductor devices at advanced technology nodes.

[0041] It should be noted that the diagrams provided in the embodiments only illustrate the basic concept of the present application in a schematic manner, and only show the components related to the present application in the diagrams, not the number, shape and size of the components when actually implemented. The actual implementation of each component can be arbitrarily changed in terms of type, number and proportion, and the layout pattern of the components can also be more complex.

[0042] The above embodiments are only illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A method for correcting the uniformity of key dimensions in key layers, characterized in that, At least including: Step 1: Obtain the key dimension data of the photomask used for the wafer to be processed, as well as the first key dimension data of the wafer before etching after development and the second key dimension data after etching; Step 2: Based on the key dimension data of the photomask, calculate the first compensation value used to compensate for the effects of the photomask itself; Step 3: Based on the first critical dimension data and the second critical dimension data, calculate the second compensation value used to compensate for the etching process effect; Step 4: Combine the first compensation value and the second compensation value to generate the final compensation value; and Step 5: When performing photolithography on subsequent wafers, apply the final compensation value to adjust the exposure dose.

2. The method for correcting the uniformity of key dimensions at key levels according to claim 1, characterized in that: In step one, the key dimension data of the photomask comes from the factory certification data of the photomask.

3. The method for correcting the uniformity of key dimensions at key levels according to claim 1, characterized in that: In step two, the first compensation value is the first exposure dose map obtained by converting the key size data of the photomask with the preset design value through the photomask error enhancement factor.

4. The method for correcting the uniformity of key dimensions at key levels according to claim 1, characterized in that: In step three, the second compensation value is a second exposure dose map derived from the difference between the actual etching deviation and the target etching deviation calculated from the first critical dimension data and the second critical dimension data.

5. The method for correcting the uniformity of key dimensions at key levels according to claim 1, characterized in that: In step one, the first critical dimension data and the second critical dimension data are obtained by measuring a predetermined number of points selected within each exposure field on the wafer.

6. The method for correcting the uniformity of key dimensions at key levels according to claim 5, characterized in that: The predetermined number of points is 5 points.

7. The method for correcting the uniformity of key dimensions at key levels according to claim 1, characterized in that: In step four, the merging is to superimpose the first exposure dose map represented by the first compensation value and the second exposure dose map represented by the second compensation value to generate the final compensation value.

8. The method for correcting the uniformity of key dimensions at key levels according to claim 1, characterized in that: The method further includes: after maintenance of the etching equipment used to generate the second compensation value, determining whether the etching process effect has changed by re-acquiring and comparing the first critical dimension data and the second critical dimension data; and when the etching process effect has not changed significantly, continuing to apply the final compensation value without recalculating the first compensation value.

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