JP2793666B2 - Stepper alignment accuracy monitoring method and apparatus - Google Patents

Description

The present invention relates to a method and an apparatus for manufacturing a semiconductor integrated circuit,
Particularly, a stepper suitable for forming an integrated circuit having stable element characteristics by improving the accuracy of pattern superposition with a base in an exposure step by a reduction projection exposure apparatus (abbreviated as a stepper) for forming a pattern of a semiconductor integrated circuit. The present invention relates to a method and an apparatus for monitoring the accuracy of alignment.

[Conventional technology]

2. Description of the Related Art Conventionally, in a method and equipment for manufacturing a semiconductor integrated circuit, circuit patterns of circuit elements are sequentially formed on a silicon wafer, and the cross section has a multi-layer structure. Is an important point in manufacturing, but in order to form several million elements or more on one chip, especially with the advancement of miniaturization, the wiring of the upper layer connected to the element formed in the lower layer is required. Alignment is an important manufacturing point. This circuit pattern alignment method has been developed as an alignment technique for an exposure apparatus of a semiconductor manufacturing facility, particularly for a reduction projection exposure apparatus (stepper). However, if the alignment of the stepper itself causes a failure of the device or the accuracy of the entire device is degraded, the device itself does not know even if an inaccurate alignment is actually performed, and for the first time due to defective element characteristics after manufacturing, etc. There were many problems of understanding. For this reason, an alignment inspection device that determines alignment accuracy has been developed and put into practical use as an inspection device separate from a stepper. By combining such a manufacturing facility and an inspection device that determines the processing result, the alignment accuracy can be improved. Judgments are made to manufacture semiconductors. Related methods and apparatuses of this type include, for example, “Submicron Lithography General Technical Data” (Showa 60, Science Forum, pp.403 to 404).
On page 12 there are those that discuss dimensional inspections and the like.

[Problems to be solved by the invention]

The above prior art only determines the processing accuracy of the manufacturing equipment, in particular, only determines whether the alignment error amount of the stepper is within the standard compared to the manufacturing error standard.If the alignment error is out of the standard, the processing condition of the stepper is determined. No consideration has been given to the method of changing to the optimum processing conditions, and in the case of a non-standard alignment error, it is necessary to stop the stepper and perform experiments to set new processing conditions. For one or two days, there is a problem in that productivity cannot be reduced because the semiconductor integrated circuit manufacturing facility cannot be used.

The present invention analyzes a matching error factor based on a matching error specified by an inspection device, calculates a change item of a processing condition of a stepper and a change amount thereof, and resets the value to the stepper. In addition to the processing conditions of the stepper, in addition to calculating the time-series fluctuation and the amount of fluctuation of items necessary for maintaining the stepper itself in a processable state,
It is an object of the present invention to provide a stepper alignment accuracy monitoring method and apparatus for specifying the change item.

[Means for solving the problem]

In order to achieve the above object, a method and an apparatus for monitoring the end accuracy of a stepper according to the present invention transfer alignment error measurement data of an alignment accuracy inspection device and processing condition data of a stepper to a computer by communication from each facility. This allows the computer to handle the processing conditions of the stepper and the alignment error measurement data on a computer. Here, the offset of the wafer, the wafer rotation, the pitch deviation on the wafer, and the chip (shot) unit as the error factors of the alignment error measurement data. Analyzing the distortion, reduction rate and chip rotation rate, converting the values related to the wafer from the analyzed values, in particular, the offset amount, which is the main factor of the pattern shift on the wafer, into the offset amount of the processing condition of the stepper, This can be automatically set as a correction value of the processing condition of the stepper.

In addition, as an item that keeps the equipment itself in a workable state, the history of error factor data such as reduction rate and rotation is accumulated on a computer, and the time series fluctuation is output, so the state of the equipment changes in any direction. Or, for example, whether the reduction rate is moving in a small direction or in a large direction, so that it is possible to assist in deciding when to adjust equipment and items to be adjusted. .

[Action]

The method and the apparatus for monitoring the alignment accuracy of the stepper are described below. First, for example, as shown in FIG. 3, for the analysis of the alignment error, the point of each rectangular end from the origin of the n-layer and the (n-1) -th concentric rectangle is designed. calculating a position vector, each of X, Y direction of the n layer and the underlying n-1 layer and the deviation amount X _2, Y midpoint and X ₁ of a length of _2, the difference ΔX between the point Y ₂ of It is calculated as ΔY. This shift amount is simply a shift between the centers of the concentric rectangles in the X and Y directions, and the cause of this shift error has not been analyzed. Therefore, next, as shown in FIGS. 4 (a) to 4 (d), an offset which is a shift amount of the same component of each chip in the X and Y directions, a regular pitch shift in the X or Y direction, and It can be analyzed into a component that is a difference between a chip displacement due to wafer rotation and a reduction ratio due to a stepper lens. For this purpose, the shift amount of each component is formulated using the shift amount obtained in FIG. 3, and each shift component can be calculated by the least square method.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing an embodiment of a stepper alignment accuracy monitoring method and apparatus according to the present invention. First
In the figure, a stepper 201 and an alignment inspection device 202 are connected to respective stepper processing condition data transfer units 205 and 204 via an inspection data / processing condition data transfer signal line 206, and further processed by a processing condition data transfer unit 205. The test data transfer unit 204 is connected to the computer 101 via the data transfer line 207.

In the above configuration, when a wafer to be manufactured in the semiconductor integrated circuit manufacturing facility arrives at the stepper 201, the first wafer is exposed, and after the development and baking process, the alignment inspection apparatus 202 performs the stepper 201 exposure. It is determined whether or not the processing state, that is, the alignment accuracy with the base is within the manufacturing standard. In the determination, if the alignment error on the wafer is smaller than the standard error, conventionally, the manufacturing has only been continued. This corresponds to the content of the item of the determination process shown in FIG. However, according to the present invention, if the alignment error is larger than the standard error as determined in the following FIG. 2, a value to be changed as the processing condition of the stepper 201 is calculated and reset by analyzing the factors of the alignment error. it can.

FIG. 2 is a flow chart of a first embodiment of the stepper alignment accuracy monitoring method of FIG. In FIG. 2, after the wafer is processed by the stepper 201 and the alignment inspection device 202 and the alignment inspection, the computer 101 receives and captures the processing condition data of the stepper 201 and the processing result data of the alignment inspection device 202, that is, the alignment inspection data. (Step 2a) Here, the cause of the alignment error is analyzed for the alignment inspection data (Step 2b), and the alignment error and the manufacturing standard error are determined (Step 2c). In this determination, if the misalignment error is smaller than the manufacturing standard error, product production is continued. If the misalignment error is larger than the manufacturing standard error, the amount of change in the offset of the misalignment error factor is calculated (step 2d). Then, the offset amount is set in the stepper 201 again as the processing condition of the stepper 201 (step 2).
e). As a result, the stepper 201 is reset, and the alignment accuracy of the second wafer processed under the processing conditions falls within the manufacturing standard.

FIG. 3 is a diagram illustrating the principle of calculating the amount of misalignment in FIG.
In FIG. 3, a method of calculating the amount of misalignment of the processing result of the wafer with the stepper 201 is, for example, a design in which the position vector of each rectangular end point from the origin 0 of the n-layer and the (n-1) -th layer of the concentric rectangular pattern is designed. It is calculated, and difference ΔX of each X and Y directions of a simple n-layer and the underlying (n-1) layers of the misalignment amount of the length of the center point and X ₁ of the length of X ₂ midpoint With the midpoint of the length of Y ₂
It is calculated as the difference ΔY at the midpoint of the length of Y _1. This is just
Although the shift amount is only in the X and Y directions, according to the present invention, the cause of the misalignment error is analyzed as shown in FIG.

FIGS. 4 (a), (b), (c), and (d) are diagrams illustrating the principle of analysis of the alignment error factors in FIG. FIG. 4 (a),
4 (b), (c) and (d), the offset of the same component of each chip in the X and Y directions called the wafer offset in FIG. 4 (a) and the pitch offset in FIG. 4 (b). Error components such as a regular displacement in the X direction or the Y direction, a chip displacement due to the rotation of the wafer in FIG. 4C, and a difference in reduction ratio due to the stepper lens in FIG. 4D. Can be analyzed. These can be easily obtained by formulating the shift amount of each component using the alignment shift amount calculated in FIG. 3 and calculating each shift component by the least square method.

As described above, according to the embodiment shown in FIG. 1, it is possible to analyze the factors of the alignment error caused by the apparatus that are not related to the type of the reticle (mask) or the dimensional standard without being caused by the manufacturing process by analyzing the factors of the alignment accuracy error. In addition, this factor can be detected by a simple calculation or indirect measurement in the past, and if the value was within the operable range of the apparatus in each inspection, the work was performed as it was thereafter, however,
Also in this case, it was not possible to judge how to make the next transition only by grasping the temporary state of the apparatus. According to the present invention, the cause of the alignment error caused by this apparatus can be analyzed, and furthermore, the computer 101
Thus, the management of the history of each alignment error factor of the apparatus can be performed.

5 (a), (b), (c), (d), (e),
(F) is a graph of a change example of an analysis value and a cumulative sum of an alignment error factor caused by the apparatus in FIG. FIG. 5 (a) to (f)
5 (a), 5 (b) and 5 (c) show the change of the analysis value of the factors of the alignment error of the reduction ratio (times) ^-1 , the pitch shift (μm) and the rotation (deg ') by date, respectively. Shown, fifth
Figures (d), (e), and (f) show the change with time of the cumulative sum of the respective alignment error factors. Fig. 5 (a)-
As shown in (f), the analysis value of the alignment error factor based on the normal measurement value does not indicate the direction of change of the value. However, using the measured value, the analysis by the statistical processing such as the cumulative sum method of the alignment error factor is performed. Therefore, it is possible to grasp the direction of the change of the cause of the alignment error and the like, so that the apparatus can be manually adjusted as shown in FIG.

FIG. 6 is a flow chart of a second embodiment of the stepper alignment accuracy monitoring method of FIG. In FIG. 6, after the analysis of the matching error factors, the computer 101 accumulates the data of the matching error factors (test 6a), analyzes the history of the matching error factors from the data (step 6b), and from this analysis, Understand the trends of change (Step 6c)
It is determined whether the tendency of the change of the error factor caused by the device exceeds the standard (step 6d). Here, if there is no change in the error factor that exceeds the standard, the production of the product is continued, but even if there is an item that exceeds the standard due to the tendency, it was not possible to judge any item conventionally, but according to the present invention, at a glance The device can be adjusted by judging which item is wrong (Step 6e), and after the determination of the pass / fail of the adjustment (Step 6f), the product can be manufactured.

FIG. 7 is a block diagram showing another embodiment of the method and apparatus for monitoring the alignment accuracy of a stepper according to the present invention. FIG. 7 shows an embodiment of an alignment accuracy monitoring method and apparatus for a large number of steppers, and the same reference numerals as those in FIG. 1 denote corresponding parts. In the above configuration, an inspection apparatus for inspecting the processing results of n steppers 201-1 to 201-n.
The inspection is performed at 202, and the inspection data is managed by the computer 101.
The functions of the computer 101 are almost the same as those shown in FIGS. 2 to 6 in the embodiment of FIG. 1, but by managing n devices at once, the difference between the same models and the The difference between different models can be managed, and separate instruction contents such as equipment improvement can be calculated.

In the above embodiment, the semiconductor manufacturing method can be supported by outputting the correction value of the processing setting condition of the stepper or the like. Further, a correction value or the like of the processing setting condition of the stepper can be transmitted to the stepper and set. Further, a configuration may be adopted in which a means for analyzing the cause of the alignment accuracy error is incorporated in the alignment inspection apparatus, and a correction value or the like of the processing setting condition of the stepper is output to the stepper.

〔The invention's effect〕

According to the present invention, since the processing conditions and processing state inspection results of the stepper in the semiconductor manufacturing equipment can be grasped, the number of trials performed each time a reticle is changed by the stepper can be halved, and the operation rate of the stepper can be reduced. In addition, it is possible to improve the throughput by about 15%, to improve the throughput, and to shorten the time until the product is completed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a stepper alignment accuracy monitoring method and apparatus according to the present invention, and FIG.
FIG. 3 is a flowchart of a first embodiment of the method of monitoring the alignment accuracy of the stepper, FIG. 3 is a diagram illustrating the principle of calculating the amount of alignment deviation in FIG. 1, and FIGS. 4 (a) to (d) are alignment diagrams in FIG. 5 (a) to 5 (f) are graphs of the cumulative sum of the analysis values of the alignment error factors shown in FIG. 1, and FIG. 6 is a graph of the stepper alignment accuracy monitoring method of FIG. FIG. 7 is a flow chart of the second embodiment, and FIG. 7 is a block diagram showing another embodiment of the method and apparatus for monitoring the alignment accuracy of a stepper according to the present invention. 101: Computer, 201, 201-f to 201-n: Stepper, 2
02… Alignment inspection device, 204… Inspection data transfer unit, 205 …… Stepper processing condition data transfer unit, 206
…… Inspection data / processing condition data transfer signal line, 207 ……
Data transfer line.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tsutomu Okabe 5-20-1, Kamisumihoncho, Kodaira-shi, Tokyo Inside Musashi Plant of Hitachi, Ltd. (56) References JP-A-3-185807 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (7)

(57) [Claims] A computer for receiving processing setting conditions of a stepper, which is a reduced projection exposure apparatus of a semiconductor manufacturing facility, and an inspection result of an alignment inspection apparatus for inspecting alignment accuracy of a semiconductor integrated circuit pattern processed by the stepper. Analyzing the alignment accuracy error factor of the inspection result, outputting a correction value of the processing setting condition of the stepper, and accumulating the alignment accuracy error factor caused by the stepper as a result of analyzing the alignment accuracy error factor, And outputting a change in an error factor of the alignment accuracy of the state of the stepper at the time of processing the semiconductor integrated circuit processed by the step (c). 2. The method according to claim 1, wherein a plurality of steppers are used, and a transition of an alignment accuracy error factor of the individual steppers is compared between the individual steppers.
2. The method according to claim 1, wherein the processing characteristics unique to the individual stepper are output. 3. The stepper assembly according to claim 1, wherein at the time of manufacturing the semiconductor integrated circuit, manufacturing of the semiconductor integrated circuit is supported at least by outputting a correction value of a processing setting condition. Accuracy monitoring method. 4. When manufacturing a semiconductor integrated circuit, processing of a lower layer is performed under processing setting conditions of a stepper, and a factor of an alignment accuracy error with the lower layer is analyzed at the time of exposure in a next upper layer processing step. By outputting the correction value of the processing setting condition of the above, while supporting the setting of the processing conditions of the upper layer stepper, accumulating the alignment accuracy error factor caused by the stepper as a result of analyzing the alignment accuracy error factor,
What is claimed is: 1. A method for monitoring the accuracy of a stepper, comprising: outputting a transition of an error factor of accuracy of alignment of a stepper at the time of processing a semiconductor integrated circuit processed by the stepper. 5. A transmitting means for transmitting processing setting conditions of a stepper, which is a reduction projection exposure apparatus of a semiconductor manufacturing facility, and transmitting an inspection result of an alignment inspection apparatus for inspecting alignment accuracy of a semiconductor integrated circuit pattern processed by the stepper. The computer includes a transmission unit and a computer having a reception unit that receives transmission data from the two transmission units. The computer analyzes a cause of an error in the alignment accuracy of the inspection result as reception data, and based on the analysis result, A stepper alignment accuracy monitoring device, wherein a correction value of a processing setting condition of a stepper is calculated and output. 6. A transmission device for transmitting a correction value of a processing setting condition of a stepper from a computer to a stepper, a reception device for receiving the transmission data by the stepper, and a device for setting the reception data to the stepper. The alignment accuracy monitoring device for a stepper according to claim 5, wherein: 7. A computer which incorporates a function of analyzing a cause of alignment error of a computer into an alignment inspection apparatus and outputs a correction value of a processing setting condition of a stepper to the stepper based on the cause of alignment error. Item 5. A stepper alignment accuracy monitoring device according to Item 5.