JPS63111586A - Pattern defect inspecting method - Google Patents

Abstract

PURPOSE:To inspect a wafer pattern with high accuracy by comparing a suitable pattern stored in advance and a pattern to be inspected, with regard to each of an area consisting of a non-repeated pattern and an area consisting of a repeated pattern. CONSTITUTION:A chip 2 on a wafer 1 is brought to an enlargement image pickup through an objective lens 4 by a linear image sensor 3. The output of the linear image sensor 3 is converted to a digital signal by an A/D converter 5, and compared with the output of one of a non-repeated pattern storage part 6 or a repeated pattern storage part 7 by a comparator 8. The non-repeated pattern storage part 6 stores a non-defective pattern having no defect, which has been inspected in advance with regard to the area consisting of a non- repeated pattern, and the repeated pattern storage part 7 stores a unit exceeding one of the repeated pattern which has been extracted from a pattern to be inspected, with regard to the area consisting of the repeated pattern.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pattern defect inspection method, and in particular to a method for reliably and automatically detecting defects and foreign substances on (original plate) for printing reticle circuit patterns. Regarding the method.

[Conventional technology]

As the density of integrated circuits such as LSIs increases, the method of forming fine patterns is becoming more important. A reduction projection exposure apparatus developed as a means for forming this fine pattern has superior performance in resolution and alignment accuracy compared to conventional apparatus.

However, the exposure method is different from the conventional method, and the so-called exposure method is repeated for each tick. Since this is a step, and repeat method, if there is a foreign object on the reticle, this foreign object will be transferred to all steps and become a common defect. The product will be defective.

Therefore, it is essential to detect defects and foreign objects on this reticle with high reliability. As a conventional method for detecting this, there is a method of detecting a pattern on a wafer created by transfer using a reduction projection exposure apparatus. As an example of this, in Japanese Patent Application Laid-Open No. 58-32416, as shown in FIG. This is a comparative inspection of the two, and the presence of defects can be detected based on the difference between the two. Light 53 passes through an objective lens 50.51 to a glass plate 54 with a non-transparent transfer image 55.
and the light passing through it is 7 otomaru56,
By receiving the light at 57, it is converted into two electrical signals. These two signals pass through amplifiers 58 and 59 and enter a differential amplifier 6o, where the signals are compared and delivered to an output 62. At the output 62, if there is no difference in pattern between the tick 63 and the step 64, that is, if there is no defect, no signal is generated from the differential amplifier 60, but if there is a difference 61, a signal is generated. can detect the presence of defects. The reason why a transparent glass plate 54 is used instead of a wafer is to enhance the contrast of electrical signals.

In addition, as another conventional method, Japanese Patent Application Laid-Open No. 57-19653
As described in the above publication, there is a method of scanning one unit of a repeated portion of a pattern to be inspected and using this as a reference pattern. In FIG. 6, one unit in a repeated pattern of a pattern to be inspected 68 is scanned by an image sensor 66 through an objective lens 67, and the scanning signal is sent to an A/D converter 6.
After converting into a digital signal at step 9 and storing it in the memory 70,
The repetitive pattern of the pattern to be inspected is sequentially scanned, and the D/A of the reference pattern stored in the memory 7° by the comparing section 72 is performed.
Pattern inspection is performed by comparing with the analog signal after conversion. Since the step is a backlash pattern, two steps can be compared with one image sensor.

[Problem that the invention seeks to solve]

The above-mentioned first and second prior art techniques are based on the premise that a reticle having a plurality of identical chips is used. 9. A reticle with only one tip cannot be compared because there is no object to compare it with. There is a problem in that the number of cases of one degree increase will increase rapidly in the future as the number of cases increases, and it will not be possible to cope with this increase.

Furthermore, in the second prior art, it is possible to perform a comparative inspection of repeated patterns within a chip using this prior art, but for areas with repeated patterns, the pattern to be inspected is scanned at the start of inspection, and the reference pattern is scanned. create and
Since this pattern is not updated thereafter, there is a problem in that the pattern to be inspected cannot be compared with a reference pattern located at a distant position, and the comparison accuracy deteriorates.

The purpose of the present invention is to eliminate the problems of the prior art described above,
The objective is to highly accurately inspect a wafer pattern created by transferring it using a reduction projection exposure device.

[Means for solving problems]

The above object of the present invention is achieved by the following means.

(1) Comparatively inspect the test amount pattern with a defect-free inspected non-defective pattern previously stored in a memory or the like.

(2) Since the repeated pattern occupies about 95% of the total area of products such as memory devices, only one to several repeating units of the repeated pattern are stored and used for comparative inspection.

(3) In (2) above, the repeated pattern to be stored is extracted from the chip to be tested and used for comparative testing.

(4) Comparative inspection of adjacent repeating patterns is performed to improve accuracy.

(5) Comparison inspection is performed by comparing direct signals of pattern brightness.

C action] On a wafer created by transferring with a reduction projection exposure device 1/)
Since the /< turn is inspected, it is possible to check not only foreign matter or dust attached to the reticle or defects in the reticle pattern, but also foreign matter and dust in the optical path of the reduction projection exposure apparatus.

Since the pattern is compared with an inspected non-defective pattern stored in a memory or the like, it is possible to inspect not only a reticle having the same plurality of steps but also a reticle having only one step.

As for the repetitive pattern within the chip, only one to several units are stored and compared, so the storage capacity can be significantly reduced compared to the case where the entire one step is stored. Just the storage capacity.

The brightness comparison is performed not by comparing binary signals of black and white, but by comparing multi-value signals of brightness, so that accurate inspection can be performed.

Since the repeated pattern to be memorized is extracted from the pattern to be inspected, patterns made using the same reduction projection exposure apparatus and the same gross conditions are detected and compared using the same illumination conditions and the same pattern detector. There is no difference in brightness between the patterns to be compared, and minute defects can be detected. Furthermore, inspection accuracy is improved by constantly performing a comparative inspection of adjacent repeating patterns.

Since all comparisons are made using multivalued digital signals,
Highly reproducible and highly accurate inspection becomes possible.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Figure 1 shows a reticle with a circuit pattern that is 5 or 10 times larger than the circuit pattern that will actually be printed.
The original plate) is transferred onto a reduction projection exposure device to form a 1-degree vertical pattern on the reticle, and Step 2 on the resulting pattern 11 is used as an IJ near image centimeter to detect the presence of defects and J% objects on the reticle. 3, an enlarged image is taken through the objective lens 4. IJ near image centimeter 3
The output is converted into a digital signal by the A/D converter 5, and compared with the output of either the non-repeating pattern storage section 6 or the repeating pattern storage section 7 in the comparator 8. The selection between a non-repetitive pattern and a repeating pattern is performed by a switching circuit 9. The self-scanning direction of the image centimeter 6 and the position of the XY table 10 that moves in a direction perpendicular thereto are scaled 11. The coordinate detection circuit 12 detects the position, and the memory control circuit 15 controls the non-repeating pattern storage section 6, the repeating pattern storage section 7, and the switching circuit 9 based on this position.

The XY table 10 is a table controlled by a calculator 14 and driven by a drive circuit 15.

Next, the operation shown in FIG. 1 will be explained using FIG. 2.

FIG. 2 is a diagram showing an example of the chip 2, which includes a non-repetitive pattern portion 16 and a repeating pattern portion 17 occupying a large area within the step. Non-repeating pattern! 1s1
18. Partially enlarged view of 6. A partially enlarged view of the A-turn pattern portion 17 is shown in 19. One unit of the repeating pattern is 20.

In Figure 2, the position of linear image sensor f3 is 21
1, the switching circuit 9 in FIG. compare. The non-repetitive pattern storage section 6 operates in synchronization with the position of the linear image sensor 3,
To prevent positional deviation between patterns to be compared.

When the linear image sensor 3 is at position 22, the switching circuit 9 is set to the B side, and the defect-free inspected non-defective pattern stored in the repeating pattern storage section 7 and A/
The D-converted outputs of the linear image processor 3 are compared. Repeat pattern storage section 7 is IJ air image seven?
It operates in synchronization with the position No. 3, and repeatedly generates patterns so that no positional deviation occurs between the patterns to be compared.

In order to store the brightness of a good pattern in the non-repetitive pattern storage section 6, as shown in FIG. There is a method of detecting a pattern and inputting the output of the M/D converter 5 to the non-repetitive pattern storage section 6. This is an example of creating a non-defective pattern to be compared with the actual pattern.b In addition, a non-defective pattern may be created by rounding the pattern corners by taking into account process conditions and the like from design data.

Non-repetitive pattern storage unit 6. The brightness of the pattern is stored in the repeated pattern storage section 7 along with the coordinates of the steps, and is read out by the coordinate detection circuit 12.

FIG. 3 is a diagram showing the area to be stored in percent. The non-repetitive pattern storage section 6 stores the shaded portion 23, and the repetitive pattern storage section 7 stores the diagonal shaded portion 24. Here, these hatched areas are normal patterns without defects.

The repeating pattern 24 has a size that allows one to several repeating units 20 (Fig. i 2) to be included.

For repetitive patterns, lighting,
In terms of accuracy, it is best to extract υ based on the TEG to be tested, since it can cancel out differences in detector characteristics. Therefore, the output of the A/D converter 5 is input to the repetitive pattern storage section 7 and used for inspection.

In addition, if the repeated pattern to be stored is rewritten each time in the repeated pattern storage section 7 and adjacent or neighboring patterns are compared, detection accuracy can be further improved, making it possible to perform a more accurate comparative inspection. . As shown in FIG. 4, when inspecting the area 26, it is compared with the area 25 input to the repetitive pattern recording section 7. Then, in order to inspect the primary area 27, the area 26 is repeatedly input into the pattern storage section 7, and the e-memory contents are rewritten. In the repetition pattern W517, this rewriting is repeated.

Target patterns include single-layer cyst patterns and product multi-layer patterns, and in either case, they are stored as multiplexed information and used for comparative inspection.

Furthermore, although a linear image sensor is used as the photoelectric converter in FIG. 1, any sensor such as a TV left camera photomultiplier can be used.

Furthermore, unlike the inspection method that compares the design data of the circuit pattern used when designing the reticle, this method uses an actual comparison method, so it has the advantage of being able to take into account the characteristics of the manufacturing process and having high inspection reliability.

That is, since the circuit pattern on the wafer cannot be made to have exactly the same shape as the explanatory data, in the case of an inspection method that compares it with design data, many false alarms occur and the reliability of the inspection becomes extremely low. In this embodiment, this actual comparison method is further improved in accuracy, and the reliability of the inspection can be greatly improved.

In addition, in this example, a pattern transferred and formed on a wafer by a reduction projection exposure device was inspected, but a pattern transferred and formed by an exposure device using X-rays (X-ray stepper) was also inspected. It goes without saying that item 4 can be done.

Further, in this embodiment, an example was shown in which a wafer pattern obtained by transfer using a reduction projection exposure apparatus was inspected, but this embodiment can also be applied to the case where a reticle is directly inspected.

Although it has been stated that a reticle with only one degree, which cannot be compared with two chips, can be inspected with high precision only in this embodiment, it is of course possible to inspect a conventional reticle composed of a plurality of chips.

In this example, an example was shown in which a wafer pattern transferred using a reduction projection exposure device was inspected. It goes without saying that it can be done.

〔Effect of the invention〕

According to the present invention, it is possible to inspect a reticle having only one step. Also, foreign objects in the optical path of the reduction projection exposure device,
It also has the effect of being able to check for garbage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a pattern defect inspection apparatus which is an embodiment of the present invention, FIG. 2 is an explanatory diagram of a pattern to be inspected, and FIG.
The figure is an explanatory diagram of the area to be stored as a reference pattern.
FIG. 5 is a diagram illustrating a method of comparing repetitive pattern parts, FIG. 5 is a diagram showing a conventional example, and FIG. 6 is a diagram showing another conventional example. 1...Wafer, 2...Tep, 3...
...IJ near image sessa. 418. Objective lens, 5...A/D converter. 6... Non-repetitive pattern storage section, 7... Repeated pattern storage section, 8... Comparator, 9... Switching circuit,
10...XY table, 11 mountain scale. 12...Coordinate detection circuit. 16...Memory control circuit, 14...Computer, 15...Table drive circuit.

Claims (1)

[Claims] 1. In a method of comparing and inspecting a pattern to be inspected with a non-defective pattern stored in a memory or the like, for an area consisting of a non-repeating pattern, a non-defective pattern that has been inspected in advance and has no defects is stored. A pattern defect inspection characterized in that this is compared with the pattern to be inspected, and for areas consisting of repetitive patterns, one or more units of the repetitive pattern extracted from the pattern to be inspected are stored, and this is compared with the pattern to be inspected. Method. 2. In the pattern defect inspection method according to claim 1, for the repetitive pattern portion, one or more units of the repetitive pattern extracted from the pattern to be inspected are stored;
A pattern defect inspection method characterized in that when comparing this with a pattern to be inspected, a stored repetitive pattern is sequentially rewritten in accordance with the scanning of the pattern to be inspected, and adjacent patterns are always compared. 3. A pattern defect inspection method according to claim 1, wherein the pattern comparison is performed using a multi-valued signal of pattern brightness.