JPH087154B2 - Foreign matter inspection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign substance inspection technique, and more particularly, in the inspection of a foreign substance adhered to a semiconductor wafer having an element pattern formed thereon, the detection signals of the element pattern and the foreign substance can be clearly distinguished from each other to achieve a highly accurate inspection. The present invention relates to a foreign material inspection technique capable of performing

[0002]

2. Description of the Related Art A defect of a pattern of an element pattern formed on a semiconductor wafer is often caused by a foreign substance attached on the wafer. Therefore, the foreign substance on the wafer on which the pattern is not formed is detected. However, in the inspection of a wafer on which no pattern is formed, it is not possible to correctly inspect for adhesion of foreign matters and pattern defects in the actual manufacturing process, and the inspection accuracy becomes low.

Therefore, attempts have been made to inspect actual foreign matter defects on a wafer formed by a pattern through a predetermined process. This method processes a detection signal when a pattern is inspected by a predetermined method, and detects a peculiar signal detected at that time (a signal having a sharp peak shape compared to a normal pattern detection signal) as a defect due to a foreign substance. Is the way to do it.

Incidentally, as a description of the defect inspection on the wafer due to foreign matter, etc., "Semiconductor World (Semico World)" issued by Press Journal Co., Ltd.
nductor World) "June 1984 issue, P112-119
There is.

[0005]

However, in this method, it is possible to distinguish between a signal detected in an abnormal state in a part of a pattern and a peculiar signal associated with the above-mentioned pattern defect. This is not possible, and a normal pattern is detected as a defective pattern, which is not preferable in terms of manufacturing yield of semiconductor devices. It does not always occur at a specific pattern shape location, but it changes depending on the type of inspection equipment and the inspection conditions at each time, so it is difficult to set this uniquely, and therefore these signals are clearly distinguished. Is extremely difficult.

An object of the present invention is to provide a foreign matter inspection technique capable of highly accurately performing a foreign matter inspection on a semiconductor wafer having an element pattern formed thereon.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0008]

Of the inventions disclosed in the present application, a representative one will be briefly described below.
It is as follows.

That is, in a foreign matter inspection method for a plurality of semiconductor wafers on which element patterns are formed, a pattern signal from one of the plurality of semiconductor wafers is detected and processed to obtain a first signal. Of the singular signal of the first and the position information of the first singular signal
And a plurality of semiconductors, the second step of comparing the repetitive pitch dimensions of the element patterns on the semiconductor wafer with each other as a reference, extracting the positional information of the second peculiar signal having a predetermined relationship with the pitch dimension and storing it in the storage unit The pattern signal from the second semiconductor wafer in the wafer is detected and processed to generate a third signal.
Determining the position information of the singular signal, excluding the third singular signal having the same position information as the position information of the second singular signal, and executing the third step of outputting the remaining signal. Is.

[0010]

[0011]

[0012]

[0013]

According to the foreign matter inspection technique of the present invention described above, for example, by utilizing the regularity of the peculiar signal due to the pattern shape which is likely to occur at the same position of the element pattern repeatedly formed on the semiconductor wafer at a predetermined pitch. It is possible to detect only the foreign particle signal by making a judgment and extracting a peculiar signal associated with the pattern shape on the semiconductor wafer, and removing this signal from all detection signals, so the signal from the background element pattern is taken into consideration. Without doing so, it becomes possible to detect a finer foreign substance with high accuracy by setting a lower threshold value or the like. Further, in the first semiconductor wafer among the plurality of semiconductor wafers, the positional information of the second peculiar signal peculiar to the pitch dimension and the like of the element pattern formed in the semiconductor wafer group is stored, and thereafter, In the other second semiconductor wafer, the step of extracting the second unique signal unique to the pitch dimension of the element pattern or the like can be omitted by using the stored position information of the second unique signal. Therefore, it is possible to quickly inspect a plurality of semiconductor wafers.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is an overall configuration diagram showing an example of the configuration of an inspection apparatus for carrying out a foreign substance inspection method which is an embodiment of the present invention.

In the figure, reference numeral 1 is a semiconductor wafer as an object to be inspected, and element patterns 2 corresponding to a plurality of chips are formed in a grid pattern on the surface thereof. The semiconductor wafer 1 is placed on a moving table such as an XY table 3,
It is moved in the plane XY direction. In addition, the semiconductor wafer 1
A pattern detection system 6 including an optical system 4 and an optical element 5 whose details are omitted is arranged above the above, and this is detected as an electric signal while scanning the element pattern 2.
A signal processing system 7 can be connected to the pattern detection system 6 to inspect foreign matters.

The signal processing system 7 is directly connected to the pattern detection system 6 to process a detected signal and to detect a signal peculiar to the pattern detection signal, and the detected portion 8. The arithmetic operation unit 9 which performs a comparison operation on the peculiar signal based on the chip pitch dimension to extract only the signal having a predetermined relationship with the chip pitch dimension and obtains the coordinate position thereof, and the extracted signal The output unit 10 removes all the detected signals and outputs only the remaining signals.

A storage unit 11 is connected to the arithmetic unit 9 and the output unit 10 to store the coordinate position of the extracted signal and the coordinate position of the remaining signals.

Next, an example of the operation of the foreign substance inspection method by the inspection device having the above-mentioned structure will be described.

After the semiconductor wafer 1 is placed on the XY table 3, the pattern detection system 6 is operated, and the element pattern 2 is electrically driven by the optical element 5 while scanning the element pattern 2 on the semiconductor wafer 1 as usual. Detect as a signal. The detected pattern signal is compared in the detection unit 8 with a threshold value set to a predetermined value, for example, and a signal corresponding to the pattern is distinguished from a signal not corresponding to the pattern, that is, a peculiar signal. In this example, as shown in FIG. 2, peculiar signals (first peculiar signals) can be detected at a plurality of locations on the semiconductor wafer 1, and respective coordinate positions of these peculiar signals are detected (first step). ).

Then, these peculiar signals S ₁ , S ₂ ...
The coordinate position of S _n is sent to the calculation unit 9, where the comparison is performed based on the chip pitch dimension p as shown in FIG. That is, the coordinate position of the other specific signals S _2, S ₃ ··· S _n as a specific signal coordinate position (X1, Y1), relative to the start of the S ₁ in the specific signal (X2, Y2), (X
3, Y3) ... (Xn, Yn) relative distance is X, Y
Calculation is performed for each direction, and the respective distances L ₁ , L ₂ ...
L _n is compared with the pitch p. In this case, when the pitch dimensions are different in the X-axis direction and the Y-axis direction, it is important to perform comparison with corresponding dimensions. Then, by this comparison, only the signals at the coordinate positions in which the respective distances are in an integral multiple of the pitch p are extracted. At this time, with respect to a few signals other than the specific signal S _{1 used} as the reference, the distances to other signals using this reference are calculated and compared with the pitch p, and the relationship between the pitch p and an integer multiple is calculated. Extract all singular signals that The signal extracted in this way is repeated corresponding to the chip size and its generation is regular, so that it is not a characterized unique signal generated by a specific pattern on the element pattern 2. It's obvious. The peculiar signal (second peculiar signal) and its coordinate position are stored in the storage unit 11 (second step).

Then, the output section 10 compares all the signals (the first peculiar signal or the third peculiar signal) detected by the detecting section 8 with this peculiar signal, and by taking the difference between them, Only the signal from which the peculiar signal caused by the pattern shape is removed, that is, the signal having no regularity is left and output. Therefore, the output signal is a peculiar signal generated by the foreign matter, and the foreign matter or the pattern defect due to the foreign matter on the semiconductor wafer 1 can be inspected by confirming the coordinate position of this signal (third stage).

The remaining signal and its coordinate position are stored in the storage unit 11.

By the way, for example, when inspecting a plurality of semiconductor wafers 1 of the same type, it is not necessary to perform the inspecting steps consisting of the above-mentioned first to third steps on all the semiconductor wafers 1, and the earliest step is performed. The inspection process including the first to third stages is performed only on the semiconductor wafer 1, and for the subsequent semiconductor wafers 1, the data obtained in the second stage of the first semiconductor wafer 1 and stored in the storage unit 11. The second step may be omitted by using (coordinate information of the peculiar signal from the background element pattern 2). This makes it possible to speed up the inspection.

As described above, according to the foreign matter inspection method of the present embodiment, the foreign matter inspection can be performed on the semiconductor wafer 1 on which the element pattern 2 has already been formed. And its defect state can be inspected, and accurate inspection information can be obtained, which is extremely effective in actual countermeasures against defects.

(Embodiment 2) Here, as the scanning method in the pattern inspection of the semiconductor wafer 1, the rotary scanning method as shown in FIG. 3 can be used. That is, as shown in the figure, the semiconductor wafer 1 is rotated on the XY table 3, and the pattern detection system 6 is reciprocally scanned in one direction (for example, the X direction), and the pattern detection signal is represented by polar coordinates of the rotation angle θ and the radius r. Can be found at. Then, the peculiar signal in the detected signals is calculated as X and Y coordinates by the processing circuit 20 shown in FIG. 4 as in the previous example, and only the peculiar signal due to the foreign matter can be output in the same manner.

In FIG. 4, the coordinate information of the peculiar singular signal obtained by the inspection of the previous example and stored in the storage unit 11 is used, and this is used in the comparators 21 and 22 in the X and Y directions. By making a comparison and taking the logical product of both by the gate 23, it is possible to inspect the foreign substance and the defect due to the foreign substance. In the figure, X _a and Y _a are displacement positions of the wafer rotation center with respect to the true center of the semiconductor wafer 1, and are used as correction signals when the obtained polar coordinate signal is converted into XY coordinates, and X _i and Y a are also used. _i is the coordinate position of the previously detected regular singular signal, and the comparator 21,
It is used as a comparison signal in 22.

In this semiconductor wafer pattern detection method 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.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

[0030]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1). In a foreign matter inspection method for a plurality of semiconductor wafers having element patterns formed thereon, a pattern signal from one of the plurality of semiconductor wafers is detected and processed. First to obtain first singular signal
And the position information of the first peculiar signal are compared with each other on the basis of the repeating pitch dimension of the element pattern on the first semiconductor wafer, and the second dimension having a predetermined relationship with the pitch dimension.
The position information of the peculiar signal of the
And the pattern signal from the second semiconductor wafer among the plurality of semiconductor wafers is detected and processed to obtain the positional information of the third unique signal, and the positional information of the third unique signal is the second information. Exclude the same position information of the singular signal of
Since the third step of outputting the remaining signal is executed, it is possible to clearly distinguish the peculiar signal generated as noise due to the element pattern shape of the base and the peculiar signal generated by the foreign matter,
It is possible to accurately and highly accurately inspect foreign matters even on a patterned wafer.

(2) Since the foreign matter inspection can be performed accurately even on the semiconductor wafer after the element pattern is formed, the true foreign matter inspection in the state after the manufacturing process can be realized,
It is possible to quickly deal with defects and the like.

(3) Foreign matter can be inspected even if a polar coordinate system is used for pattern detection, and the inspection speed can be improved.

(4). When inspecting a plurality of semiconductor wafers of the same type, for the second and subsequent semiconductor wafers,
Since the second step can be omitted, the foreign matter inspection can be speeded up.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an inspection apparatus in which a foreign matter inspection method according to an embodiment of the present invention is implemented.

FIG. 2 is a schematic view of a wafer surface for explaining an example of the operation of the foreign matter inspection method according to the embodiment of the present invention.

FIG. 3 is a conceptual diagram for explaining an example of the operation of a foreign matter inspection method that is another embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a processing circuit for realizing a foreign matter inspection method according to another embodiment of the present invention.

[Explanation of symbols]

 1 Semiconductor Wafer 2 Element Pattern 3 XY Table 4 Optical System 5 Optical Element 6 Pattern Detection System 7 Signal Processing System 8 Detecting Section 9 Computing Section 10 Output Section 11 Storage Section 20 Processing Circuit 21 Comparator 22 Comparator 23 Gate

Claims (1)

[Claims] 1. A method for inspecting foreign matter on a plurality of semiconductor wafers having element patterns formed thereon, wherein the first semiconductor wafer is one of the plurality of semiconductor wafers.
Detecting the pattern signal from C and processing it;
And a position information of the first peculiar signal is obtained from the first semiconductor wafer.
C based on the repeating pitch dimension of the element pattern
Comparing as a quasi-standard,
2) extracting the position information of the singular signal and storing it in the storage unit;
From step 2 and a second semiconductor wafer of the plurality of semiconductor wafers
To detect and process the pattern signal of
The position information is obtained, and the position information of the third peculiar signal is
The same information as the position information of the second singular signal is excluded, and the remaining
And a third step of outputting a signal of