CN107561875B - Overlay error measurement and problem assessment method - Google Patents
Overlay error measurement and problem assessment method Download PDFInfo
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- CN107561875B CN107561875B CN201710796702.9A CN201710796702A CN107561875B CN 107561875 B CN107561875 B CN 107561875B CN 201710796702 A CN201710796702 A CN 201710796702A CN 107561875 B CN107561875 B CN 107561875B
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Abstract
The invention provides a method for measuring overlay error and evaluating problems, which comprises the following steps: inputting an overlay error measurement scheme, inputting measurement identification information of all overlay errors, inputting target upper and lower limits and an overlay error abnormity evaluation standard, completing data collection, comparing a measurement value with the upper and lower limits, marking an exceeded data point as a problem point, judging whether a new data collection scheme needs to be added according to the evaluation standard, if the proportion of the problem point exceeds a set value, generating an overlay error abnormity report, otherwise, judging which measurement identifications need to be brought into the new data collection scheme for measurement according to the evaluation standard, if the newly obtained measurement data contains problem points, marking the problem points until the measurement data of the overlay errors fall within the target upper and lower limits, and generating an overlay error problem and problem influence degree report. The method can reduce the time for determining the range of the overlay error problem, obtain the overlay error problem and the problem influence degree, and facilitate the judgment of engineers and the adoption of the next processing scheme.
Description
Technical Field
The invention relates to the field of microelectronic photoetching technology, in particular to an intelligent overlay error measurement and problem evaluation method.
Background
The pattern (current layer) remaining on the photoresist after exposure and development must be aligned with the pattern (previous layer) already present on the wafer substrate to ensure proper connection between the parts of the device. Too large an alignment error is one of the main causes of short and open circuits of the device, which greatly affects the yield of the device. In the integrated circuit manufacturing process, there is a special equipment to determine overlay error by measuring the relative position between the current layer pattern and the previous layer pattern on the wafer. Patterns on the wafer that are specifically used to measure overlay error are overlay marks that have been placed in designated areas during mask design, usually at the edges of the exposure unit, and with modified overlay marks placed near the devices in the exposure unit. Overlay error quantitatively describes the deviation of the current layer from the previous layer along the X and Y directions, and the distribution of this deviation on the wafer surface, which is a key indicator for detecting the quality of the photolithography process, and ideally, the overlay error is zero when the patterns of the current layer and the previous layer are perfectly aligned.
Regarding the measurement of overlay error, the method commonly used in the industry is performed according to a predetermined measurement scheme, which includes which exposure units are measured on the wafer, which overlay marks are measured in one exposure unit, as shown in fig. one (a) (b), and a total of 117 overlay marks are measured for four positions of each exposure unit of thirteen fixed exposure units, respectively for 36 overlay marks of four positions of each exposure unit of nine fixed exposure units. The engineer judges the overlay error between the current layer and the previous layer based on the data obtained by the fixed measurement scheme, and when the overlay error of one or more measurement points is abnormal, the measurement scheme needs to be additionally established to judge the range of the problem area, so that a next processing method is adopted. The problem of the general method is that the time required for establishing a new measurement scheme after finding a problem is long, the time for loading and unloading wafers is additionally increased, the productivity is affected, an abnormal point may appear at any position, and the omission is easily caused when a problem area is artificially judged. At present, the demand of the industry for the productivity of semiconductors is higher and higher, the measurement of the photolithography process also faces a great challenge, and how to improve the measurement speed without missing the problem point is the problem to be faced.
Disclosure of Invention
The invention provides an intelligent overlay error measurement and problem evaluation method, which reduces the time for determining the overlay error problem range, obtains the overlay error problem and the problem influence degree at one time, and is convenient for engineers to judge and adopt the next processing scheme.
In order to achieve the above object, the present invention provides a method for overlay error measurement and problem evaluation, comprising the following steps:
inputting a normal fixed overlay error measurement scheme;
inputting all available information of overlay error measurement marks on the wafer;
inputting corresponding target upper and lower limits of the overlay error and an overlay error abnormal evaluation standard;
finishing normal fixed alignment error data collection, wherein in the measurement process, when a measurement value of a measurement identifier is obtained, the system automatically compares the measurement value with the upper limit and the lower limit of a target, if the measurement values are within the range of the upper limit and the lower limit of the target, an alignment error report is directly generated, and if a data point exceeding the upper limit and the lower limit of the target exists, the alignment error report is marked out to start the next step;
aiming at the marked problem points, the system automatically judges whether a new data collection scheme needs to be added or not according to an evaluation standard, if the proportion of the problem points exceeds a set value, an overlay error abnormal report is directly generated, and if the proportion is within the range of the set value, the next step is started;
the system automatically judges which measurement identifications need to be brought into a new data collection scheme for measurement according to an evaluation standard, if the newly obtained measurement data are within the range of the target upper limit and the target lower limit, the next step is started, if the newly obtained measurement data still have problem points exceeding the target upper limit and the target lower limit, the problem points are marked, and the step is repeated;
and repeating the steps until the measured data of the overlay error all fall within the target upper and lower limit ranges, and generating an overlay error problem and a problem influence degree report.
Further, the total available overlay error metrology marks include all metrology marks near the edge of the exposure unit and the device in the exposure unit.
Further, the overlay error abnormity evaluation standard sets the proportion of the problem points, and the proportion is set based on different overlay error precision requirements.
Further, the overlay error anomaly evaluation criterion sets a distance from the problem point from the wafer population, and the metrology targets within the distance range are incorporated into the new data collection scheme, and the distance is set based on different metrology target distribution densities.
Furthermore, the overlay error anomaly evaluation criterion sets a distance from the center of the exposure unit where the problem point is located from the aspect of the exposure unit, the measurement identifier having the same relative position coordinate as the problem point in the exposure unit within the distance range is included in a new data collection scheme, and the distance is set based on different distribution densities of the exposure unit.
Furthermore, when the measurement mark within the specified distance range of the problem point marked by the distance is measured, the measured point is skipped.
The invention provides an intelligent overlay error measurement and problem evaluation method. Firstly, inputting a normal fixed overlay error measurement scheme, then inputting information of all available overlay error measurement marks on a wafer, then inputting corresponding target upper and lower limits of overlay errors and an overlay error abnormity evaluation standard, then completing normal fixed overlay error data collection, wherein in the measurement process, every time a measurement value of one measurement mark is obtained, the system automatically compares the measurement value with the target upper and lower limits, data points exceeding the target upper and lower limits are marked, aiming at the marked problem points, the system automatically judges whether a new data collection scheme needs to be added or not according to the evaluation standard, if the proportion of the problem points exceeds a set value, an overlay error abnormity report is directly generated, if the proportion is within the set value range, the system automatically judges which measurement marks need to be included in the new data collection scheme for measurement according to the evaluation standard, and if the newly obtained measurement data still has the problem points exceeding the target upper limit and the target lower limit, marking the problem points, and repeating the steps until the measurement data of the overlay error fall within the target upper limit and the target lower limit, and generating an overlay error problem and problem influence degree report. The intelligent overlay error measurement and problem evaluation method provided by the invention can reduce the time for determining the overlay error problem range, obtain the overlay error problem and the problem influence degree at one time, and facilitate the judgment of engineers and the adoption of the next processing scheme.
Drawings
FIG. 1a is a schematic diagram showing four positions of each exposure unit of nine exposure units fixed for measurement.
FIG. 1b is a schematic diagram showing nine positions of each exposure unit of thirteen exposure units fixed for measurement.
FIG. 2 is a flowchart of a method for overlay error measurement and problem evaluation according to a preferred embodiment of the present invention.
Detailed Description
The following description will be given with reference to the accompanying drawings, but the present invention is not limited to the following embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is noted that the drawings are in greatly simplified form and that non-precision ratios are used for convenience and clarity only to aid in the description of the embodiments of the invention.
Referring to fig. 2, fig. 2 is a flowchart illustrating a method for overlay error measurement and problem evaluation according to a preferred embodiment of the invention. The invention provides a method for measuring overlay error and evaluating problems, which comprises the following steps:
SO 1: inputting a normal fixed overlay error measurement scheme; in the preferred embodiment, nine exposure units as shown in fig. one (a) each have information of four positions; a normal fixed overlay error measurement scheme includes, but is not limited to, a data collection scheme of four positions per exposure unit for nine exposure units and nine positions per exposure unit for thirteen exposure units as shown in FIGS. one (a) (b);
SO 2: inputting all available information of overlay error measurement marks on the wafer; specifically, inputting information of each measurement identifier of each exposure unit on a wafer;
SO 3: inputting corresponding target upper and lower limits of the overlay error and an overlay error abnormal evaluation standard; in the preferred embodiment, the target upper and lower limits of the input overlay error are ± 8nm, and the evaluation standard of the overlay error anomaly: the proportion of the problem points is 17 percent of the threshold value; the overall layer distance of the wafer is 7mm, and the layer distance of the exposure unit is 21 mm;
SO 4: finishing normal fixed alignment error data collection, wherein in the measurement process, when a measurement value of a measurement identifier is obtained, the system automatically compares the measurement value with the upper limit and the lower limit of a target, if the measurement values are within the range of the upper limit and the lower limit of the target, an alignment error report is directly generated, and if a data point exceeding the upper limit and the lower limit of the target exists, the alignment error report is marked out to start the next step; in this embodiment, specifically, in order to complete normal fixed alignment error data collection, in the measurement process, each time a measurement value of a measurement identifier is obtained, the system automatically compares the measurement value with the target upper and lower limits of ± 8nm, if the measurement values are within the range of ± 8nm, an alignment error report is directly generated, and if a data point exceeding the range of ± 8nm exists, the alignment error report is marked as SO 5;
SO 5: aiming at the marked problem points, the system automatically judges whether a new data collection scheme needs to be added or not according to an evaluation standard, if the proportion of the problem points exceeds a set value, an overlay error abnormal report is directly generated, and if the proportion is within the range of the set value, the next step is started; in this embodiment, the specific operation is that for the marked problem points, the system automatically determines whether a new data collection scheme needs to be added according to an evaluation standard, if the number of the marked problem points is 7, and the proportion of the marked problem points is 19.44% larger than the threshold value 17%, it indicates that the overlay error of the wafer has a large problem, and an overlay error abnormal report is directly generated, and if the number of the marked problem points is 1, and the proportion of the marked problem points is 2.78% smaller than the threshold value 17%, SO6 is started;
SO 6: the system automatically judges which measurement identifications need to be brought into a new data collection scheme for measurement according to an evaluation standard, if the newly obtained measurement data are within the range of the target upper limit and the target lower limit, the next step is started, if the newly obtained measurement data still have problem points exceeding the target upper limit and the target lower limit, the problem points are marked, and the step is repeated; in this embodiment, the specific processing flow is as follows: the system automatically judges which measurement identifiers need to be brought into a new data collection scheme for measurement according to an evaluation standard, brings the measurement identifiers within a range of 7mm from the 1 problem point and the measurement identifiers in the exposure unit within a range of 21mm from the center of the exposure unit where the 1 problem point is located and which have the same relative position coordinates as the problem point (in the exposure unit) into the new data collection scheme, starts SO7 if the newly obtained measurement data are within +/-8 nm of the upper and lower target limits, marks the newly obtained measurement data if the newly obtained measurement data still have the problem points exceeding +/-8 nm of the upper and lower target limits, and repeats SO 6;
SO 7: and repeating the steps until the measured data of the overlay error all fall within the target upper and lower limit ranges, and generating an overlay error problem and a problem influence degree report.
Further, the total available overlay error metrology marks include all metrology marks near the edge of the exposure unit and the device in the exposure unit.
Further, the overlay error abnormity evaluation standard sets the proportion of the problem points, and the proportion is set based on different overlay error precision requirements.
Further, the overlay error anomaly evaluation criterion sets a distance from the problem point from the wafer population, and the metrology targets within the distance range are incorporated into the new data collection scheme, and the distance is set based on different metrology target distribution densities.
Furthermore, the overlay error anomaly evaluation criterion sets a distance from the center of the exposure unit where the problem point is located from the aspect of the exposure unit, the measurement identifier having the same relative position coordinate as the problem point in the exposure unit within the distance range is included in a new data collection scheme, and the distance is set based on different distribution densities of the exposure unit.
Furthermore, when the measurement mark within the specified distance range of the problem point marked by the distance is measured, the measured point is skipped.
In summary, the present invention provides an intelligent overlay error measurement and problem assessment method. Firstly, inputting a normal fixed overlay error measurement scheme, then inputting information of all available overlay error measurement marks on a wafer, then inputting corresponding target upper and lower limits of overlay errors and an overlay error abnormity evaluation standard, then completing normal fixed overlay error data collection, wherein in the measurement process, every time a measurement value of one measurement mark is obtained, the system automatically compares the measurement value with the target upper and lower limits, data points exceeding the target upper and lower limits are marked, aiming at the marked problem points, the system automatically judges whether a new data collection scheme needs to be added or not according to the evaluation standard, if the proportion of the problem points exceeds a set value, an overlay error abnormity report is directly generated, if the proportion is within the set value range, the system automatically judges which measurement marks need to be included in the new data collection scheme for measurement according to the evaluation standard, and if the newly obtained measurement data still has the problem points exceeding the target upper limit and the target lower limit, marking the problem points, and repeating the steps until the measurement data of the overlay error fall within the target upper limit and the target lower limit, and generating an overlay error problem and problem influence degree report. The intelligent overlay error measurement and problem evaluation method provided by the invention can reduce the time for determining the overlay error problem range, obtain the overlay error problem and the problem influence degree at one time, and facilitate the judgment of engineers and the adoption of the next processing scheme.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.
Claims (6)
1. A method for overlay error measurement and problem assessment, comprising the steps of:
inputting a normal fixed overlay error measurement scheme;
inputting all available information of overlay error measurement marks on the wafer;
inputting corresponding target upper and lower limits of the overlay error and an overlay error abnormal evaluation standard;
finishing normal fixed alignment error data collection, wherein in the measurement process, when a measurement value of a measurement identifier is obtained, the system automatically compares the measurement value with the upper limit and the lower limit of a target, if the measurement values are within the range of the upper limit and the lower limit of the target, an alignment error report is directly generated, and if a data point exceeding the upper limit and the lower limit of the target exists, the alignment error report is marked out to start the next step;
aiming at the marked problem points, the system automatically judges whether a new data collection scheme needs to be added or not according to an evaluation standard, if the proportion of the problem points exceeds a set value, an overlay error abnormal report is directly generated, and if the proportion is within the range of the set value, the next step is started;
the system automatically judges which measurement marks need to be brought into a new data collection scheme for measurement according to the evaluation standard, if the newly obtained measurement data are within the range of the target upper limit and the target lower limit, the next step is started, if the newly obtained measurement data still have the problem points exceeding the target upper limit and the target lower limit, the problem points are marked, the step is repeated,
measuring the measurement identifier included in the new data collection scheme to measure the measurement identifier in a specified distance range of the problem point marked by the distance mark, and including the measurement identifier in the distance range of the problem point and the measurement identifier which is in the central distance range of the exposure unit in which the problem point is located and has the same relative position coordinate with the problem point in the exposure unit in the central distance range of the exposure unit in which the problem point is located in the new data collection scheme;
and repeating the steps until the measured data of the overlay error all fall within the target upper and lower limit ranges, and generating an overlay error problem and a problem influence degree report.
2. The method of overlay error measurement and problem assessment according to claim 1, wherein said all available overlay error metrology marks comprise all metrology marks near the edge of an exposure unit and devices in an exposure unit.
3. The method of claim 1, wherein the overlay error anomaly evaluation criterion sets a ratio of problem points, the ratio being set based on different overlay error accuracy requirements.
4. The method of claim 1, wherein the overlay error anomaly evaluation criterion is based on wafer population, and wherein a distance from the problem point is set, and metrology marks within the distance range are included in the new data collection scheme, and the distance is set based on different metrology mark distribution densities.
5. The method of claim 1, wherein the overlay error anomaly evaluation criterion is set from the exposure unit level, and a distance from the center of the exposure unit where the problem point is located is set, and measurement identifiers with the same relative position coordinates as the problem point in the exposure units within the distance range are included in the new data collection scheme, and the distance is set based on different distribution densities of the exposure units.
6. The method of claim 1, wherein measuring the measurement flag within a predetermined distance range from the marked problem point skips the measured point.
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| JP2005301156A (en) * | 2004-04-15 | 2005-10-27 | Sony Corp | Inspection method and apparatus for mask defect, and method for creating reference for mask inspection |
| CN1699916A (en) * | 2004-03-25 | 2005-11-23 | 株式会社三丰 | System and method for excluding extraneous features from image inspection operations |
| CN102683238A (en) * | 2012-05-04 | 2012-09-19 | 上海华力微电子有限公司 | Method for improving line width measurement accuracy alignment of picture |
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| JPH02253484A (en) * | 1989-03-28 | 1990-10-12 | Toppan Printing Co Ltd | Method and device for automatically setting threshold value for binarization |
| CN1699916A (en) * | 2004-03-25 | 2005-11-23 | 株式会社三丰 | System and method for excluding extraneous features from image inspection operations |
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