JPS61253448A - Foreign matter inspecting device - Google Patents

Abstract

PURPOSE:To enable the performing of accurate and highly accurate inspection of foreign matters, by arranging a detector section, a computing section, an output section and the like to clearly distinguish signals generated from a pattern shape from specific signals generated from foreign matters. CONSTITUTION:After a semiconductor wafer 1 is placed on an XY table 3, a pattern detection system 6 is operated to detect a pattern 2 with an optical element 5 as electrical signal scanning the element pattern 2 on a wafer 1. The signal is distinguished with a detector section 8 from specific signals as such corresponding to the pattern. Then, the specific signals are sent out to a computing section 9 to be compared with pitch dimensions of a chip as reference. Then, an output section 10 compares the specific signals with all the signals detected by the detector section 8 while determining the difference therebetween to leave non-regular signals alone, which are outputted. Thus, a foreign matter or a pattern defect due to the foreign matter on the wafer 1 can be inspected by confirming the coordinate position of the signal.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an apparatus for inspecting foreign matter present on the element pattern of a semiconductor device, and in particular, to a highly accurate inspection by clearly distinguishing each detection signal of the element pattern and foreign matter. This invention relates to a foreign matter inspection device that can perform the following.

[Background technology]

Device patterns formed on semiconductor wafers often have pattern defects due to foreign matter adhering to the wafer, and for this reason, wafers on which no patterns are formed are inspected for foreign matter.

However, when inspecting a wafer on which no pattern is formed, it is not possible to correctly inspect for foreign matter adhesion or pattern defects in the actual manufacturing process, resulting in low inspection accuracy.

For this reason, attempts have been made to inspect actual foreign matter defects on wafers that have been patterned through a predetermined process. This method processes the detection signal when inspecting a pattern using a predetermined method, and detects the unique signal detected at that time (a signal with a sharper peak shape than a normal pattern detection signal) as a defect caused by a foreign object. This is the way to do it.

However, with this method, it is not possible to distinguish between a signal detected in an unusual state in a part of the pattern shape and a peculiar signal associated with the aforementioned pattern defect, and a normal pattern is treated as a defective pattern. Unfavorable results are likely to occur in terms of manufacturing yield of semiconductor devices, such as detection. In particular, signals based on such pattern shapes are not necessarily generated at specific pattern shape locations, but vary depending on the type of inspection equipment and the inspection conditions at the time, and it is important to set these signals uniquely. Therefore, it is extremely difficult to clearly distinguish these signals.

In addition, there is a document published by Press Journal Co., Ltd. [Semiconductor World (Semiconductor World)] that describes defect inspection due to foreign objects on wafers.
ctor World) J 19B4 June issue P112
There are ~119.

[Purpose of the invention]

An object of the present invention is to provide a foreign object inspection device that can clearly distinguish between signals generated due to the specificity of a pattern shape and signals generated from foreign objects and defects caused by foreign objects, thereby enabling highly accurate foreign object inspection. It's about doing.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, there is a detection section that detects a pattern signal from the object to be inspected and processes it to obtain a unique signal, and a detection section that compares and calculates this specific signal with reference to the pattern repetition pitch dimension of the object to be inspected, and calculates the pitch dimension and a predetermined pitch dimension. By including a calculation unit that extracts a related singular signal and an output unit that removes the signal extracted by this calculation unit from the singular signal and outputs the remaining signal, the pattern shape that is likely to occur at the same location of the pattern can be adjusted. The peculiar signal associated with the pattern shape on the object to be inspected is extracted by determining the peculiar signal by using its regularity, and by removing this signal from all detection signals, only the foreign object signal is detected and the foreign object is detected. Tests can be carried out.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Reference numeral 1 denotes a semiconductor wafer as an object to be inspected, and element patterns 2 corresponding to a plurality of chips are formed on the surface of the semiconductor wafer in the form of folds. This semiconductor wafer 1 is placed on a moving table such as an XY table 3 and is moved in the XY direction of the plane. Further, above the semiconductor wafer 1, a pattern detection system 6 including an optical system 4 and an optical element 5, the details of which are omitted, is arranged.
While scanning the element pattern 2, this is detected as an electrical signal. A signal processing system 7 is connected to this pattern detection system 6, and foreign matter inspection can be performed.

The signal processing system 7 includes a detection section 8 that is directly connected to the pattern detection system 6 and processes the detected signal and detects a signal unique to the pattern detection signal, A calculation unit 9 performs a comparison calculation using the pitch dimension of the chip as a reference, extracts only the signal having a predetermined relationship with the pitch dimension of the chip, and calculates its coordinate position; and an output section 10 for removing all the signals and outputting only the remaining signals.

Note that a storage section 11 is connected to the calculation section 9 and the output section 10, and stores the coordinate position of the extracted signal and the coordinate position of the remaining signals.

Next, a foreign matter inspection method using the inspection apparatus having the above configuration will be explained.

After placing the semiconductor wafer 1 on the XY table 3, the pattern detection system 6 is operated, and the optical element 5 detects the element pattern 2 as an electrical signal while scanning the element pattern 2 on the wafer 1 as usual. . The detected pattern signal is compared with a threshold value set to a predetermined value, for example, in the detection unit 8, and a signal corresponding to the pattern and a
Other signals, that is, singular signals, are distinguished. In this example, as shown in FIG. 2, singular signals can be detected at a plurality of locations on the semiconductor wafer 1, and the coordinate positions of each of these singular signals are detected.

Then, these unique signals Sl, S2, . That is, using the coordinate position (XI, Yl) of one singular signal S1 among the singular signals as a reference, other singular signals S2. S3...Sn coordinate position (X2. Y2), (Xa, Ya) - (Xn
, Yn) in each of the X and Y directions, and the respective distances L1. L2...Ln are compared with the pitch p. In this case, if the pitch dimensions are different in the X direction and the Y direction, it is important to compare the corresponding dimensions. Through this comparison, only signals at coordinate positions whose respective distances are integer multiples of the pitch p are extracted. At this time, for a few signals other than the singular signal s1 used as a reference, the distances from other signals using this as a reference are calculated and compared with the pitch p, and the pitch p
All singular signals that are integral multiples of are extracted. The signals extracted in this way are repeated in accordance with the chip dimensions, and their occurrence is regular, so it is clear that they are unique signals that are characterized by being generated by a specific pattern on the device pattern. It is. This singular signal and its coordinate position are preferably stored in the storage unit 11.

Next, the output unit 10 compares all the signals detected by the detection unit 8 with this singular signal and calculates the difference between the two to obtain a signal from which the singular signal caused by the pattern shape has been removed, that is, Only irregular signals are left and output. Therefore, this output signal is a unique signal generated by a foreign object, and by checking the coordinate position of this signal, it is possible to inspect the semiconductor wafer 1 for a foreign object or a pattern defect caused by the foreign object.

Note that this remaining signal and its coordinate position are stored in the storage unit 1.
Remember it in 1.

According to this inspection, it is possible to perform foreign object inspection even on semiconductor wafers that have already been patterned, so it is possible to inspect the actual state of foreign object adhesion that has gone through the manufacturing process and its defect status, and to obtain accurate inspection information. This is extremely effective in actual defect countermeasures.

Here, as a scanning method for pattern inspection of the semiconductor wafer 1, a rotational scanning method as shown in FIG. 3 can also be used. That is, as shown in the figure, the wafer 1 is rotated on the table 3, and the detection system 6 is rotated in one direction (for example, the X direction).
The pattern detection signal is sent to the rotation angle θ and the radius r.
It can be found in polar coordinates. Then, the singular signal among the detected signals is calculated as the X and Y coordinates in the processing circuit 20 shown in FIG. 4 in the same manner as in the previous example, and furthermore, only the peculiar signal due to the foreign object can be output in the same manner.

In addition, in FIG. 4, the coordinate information of a regular singular signal obtained from the previous test and stored in the storage unit 11 is used, and this is compared in the X and Y directions in the comparators 21 and 22. By performing a logical product of the two using the gate 23, foreign matter and defects caused by foreign matter can be inspected.

In the figure, Xa and Ya are the displacement amounts of the wafer rotation center with respect to the true center of the wafer 1, and are used as correction signals when converting the obtained polar coordinate signal into XY coordinates.
Yi is the coordinate position of the previously detected regular and singular signal, and is used as a comparison signal in the comparators 21 and 22.

In this method of inspecting semiconductor wafer patterns using polar coordinates, signal detection can be performed easily and at high speed, and inspection time can be shortened and inspection accuracy can be improved.

〔effect〕

(1) A detection unit that detects a singular signal from the wafer pattern detection signal, a calculation unit that extracts only regular signals from this singular signal, and removes this regular signal from all signals of the detection unit. Since it is equipped with an output section that outputs only the remaining signal, it is possible to clearly distinguish between a peculiar signal caused by a pattern shape and a peculiar signal caused by a foreign object.
Even on wafers on which patterns have been formed, foreign matter inspection can be performed accurately and with high precision.

(2) Since foreign matter inspection can be performed accurately even on wafers after pattern formation, true foreign matter inspection can be realized in the state after the manufacturing process, and defect countermeasures can be quickly taken.

(3) By the functions of the detection section, the calculation section, and the output section, only the signal due to foreign matter can be automatically outputted from the detected singular signals, so that full automation of the inspection can be achieved.

(4) Even if a polar coordinate system is used for pattern detection, it is possible to inspect foreign objects and improve the inspection speed.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, it is not necessary to perform the above-mentioned inspection process on all wafers, but only the first wafer is subjected to the above-mentioned inspection process, and subsequent wafers are inspected using the regularity data (stored in the storage unit) obtained in the previous process. The configuration may be such that only the foreign object signal is output using the foreign object data).

[Application field]

The above explanation has mainly been about the application of the invention made by the present inventor to pattern inspection of semiconductor wafers, which is the background field of application, but the invention is not limited to this, and is not limited to this. If so, it can be applied to, for example, pattern inspection of photomasks.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram of a wafer surface for explaining an inspection method, and Fig. 3 is similar to Fig. 2 for explaining another inspection method. Figure 4 is the processing circuit diagram. DESCRIPTION OF SYMBOLS 1... Semiconductor wafer (object to be inspected), 2... Element pattern, 3... XY table, 5... Optical element, 6...
... Pattern detection system, 7... Signal processing system, 8... Detection section, 9... Calculation section, 10... Output section, 11...
Storage section, 2o... Processing circuit, 21.22... Comparator, 23... Gate. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A detection unit that detects a pattern signal from an object to be inspected and processes it to obtain a unique signal, and a comparison calculation of this singular signal using the pattern repetition pitch dimension of the object to be inspected as a reference. A foreign object characterized by comprising: a calculation unit that extracts a singular signal having a predetermined relationship with the pitch dimension; and an output unit that removes the signal extracted by the calculation unit from the singular signal and outputs the remaining signal. Inspection equipment. 2. The foreign object inspection device according to claim 1, wherein the calculation unit extracts the singular signal whose coordinate position is an integral multiple of the pitch dimension. 3. The foreign object inspection device according to claim 1 or 2, wherein the detection section detects a pattern in the rotational direction of the object to be inspected and determines the polar coordinate position of the singular signal. 4. A patent claim that obtains the coordinate position of a unique signal, compares this coordinate position with the pitch dimension, extracts a signal that has a predetermined relationship, and outputs the coordinate position excluding the coordinate position of the extracted signal. A foreign matter inspection device according to any one of items 1 to 3.