JPH0320878A - Pattern inspecting device - Google Patents

Abstract

PURPOSE:To inspect the defect of a repeat pattern in a single chip by attaching a signal delay circuit, and comparing a signal from a photodiode array with a signal in which the signal is delayed by the cycle of the repeat pattern with the signal delay circuit. CONSTITUTION:The pattern inspecting device is comprised of the signal delay circuit 6 to delay the signal from a photodiode array 4 for a fixed time, and a comparison discriminator 8 to compare the signal from the photodiode array 4 with the signal from the signal delay circuit 6. When the signal from the repeat pattern in the single chip is detected by using a single lens 3 in such constitution, the signal repeated with a constant cycle can be obtained. And the repeat pattern can be inspected by comparing the signal with the one delayed by a repeating cycle. In such a way, it is possible to inspect the defect of the repeat pattern in the single chip at high speed and with high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pattern inspection apparatus and inspection method for inspecting defects in patterns formed on photomasks and wafers used in the manufacture of semiconductor integrated circuits.

2. Description of the Related Art Conventionally, mask/reticle defect inspection devices and wafer inspection devices have been used as pattern inspection devices to inspect pattern defects on photomasks and wafers. A conventional pattern inspection apparatus and inspection method will be explained below.

Figure 3 shows KLA's automatic mask/reticle defect inspection system "Model KL" as a typical pattern inspection system.
The basic structure of A-200 Series J is shown. Third
In the figure, 11 is a photomask to be tested (hereinafter abbreviated as mask), 12 is illumination light that irradiates the mask, 13 is a pair of objective lenses, and 14 is an image of the test pattern imaged by the objective lens. 16 is a photodiode array that converts the image into an electrical signal; 16 is a design data expansion unit that sends the design data of the mask to be inspected, which has been converted to inspection data before the start of the inspection, in synchronization with the pattern image of the mask; 16 is a photodiode; A signal switcher 17 switches between the signal from the array and the signal from the design data expansion unit, and 17 is a comparison/determiner that compares the signal from the left photodiode array and the signal from the signal switcher.

The operation of the automatic mask/V-ticle defect inspection apparatus constructed as described above will be explained below.

First, when the signal from the right photodiode play is selected by the signal switcher, the images of the test pattern formed by the left and right objective lenses are compared. This method can be used when inspecting patterns of a plurality of identical chips arranged on a mask (multi-chip), and is called a chip comparison mode. In this mode, the left and right objective lenses are first set at the same position on the two chips to be compared. While moving the stage, signals from the left and right photodiode arrays are compared, and if there is a difference between the two signals, this is treated as a defect and information such as the stage position is captured.

Next, when the signal from the design data development unit is selected by the signal switch b, the design data is compared with the image of the test pattern imaged by the left objective lens.

In this method, even the pattern of only one chip (single chip) placed on a mask can be inspected by directly comparing it with design data, and is called a data comparison mode. In this mode, the image of the test pattern and the signal of the design data are compared while moving the stage, and if there is a difference between the two signals, this is treated as a defect and information such as the stage position is imported. We will meet.

Problems to be Solved by the Invention However, in the conventional structure described above, in the case of a single p-chip, most of the patterns within the chip are repetitive patterns, even if the chip is a memory element or an image sensor. Even if it is, it is often not possible to test it in chip comparison mode. This is because the distance between the two objective lenses cannot be reduced below a certain value. In this case, the entire chip must be tested in data comparison mode. In the data comparison mode, the design data of the mask to be inspected must be converted into inspection data. This data conversion generally requires a considerable amount of time. Furthermore, the data comparison mode has the drawbacks of slower inspection speed and slightly lower detection sensitivity than the chip comparison mode.

The present invention solves the above-mentioned conventional problems, and provides a pattern inspection device that can inspect the comb pattern in a single chip using a single lens at high speed and high sensitivity similar to the chip comparison mode. It is something to do.

Means for Solving the Problems To achieve this object, the pattern inspection device of the present invention includes a pattern detector (a photodiode array in the conventional example) as well as a device for delaying the signal from the pattern detector for a certain period of time. It consists of a signal delay circuit and a comparison/judgment device that compares the signal from the pattern detector and the signal from the signal delay circuit.

Effect: With this structure, when a signal from a repeating pattern in a single chip is detected using a single lens,
A signal that is repeated at regular intervals is obtained. By comparing this signal with a signal delayed by the repeat period, the repeat pattern can be inspected.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the structure of a pattern inspection device according to an embodiment of the present invention, and shows an example of a conventional pattern inspection device (3rd example).
A signal delay circuit 6 is added to the circuit shown in FIG. 1, the signal switcher 7 includes a signal delay circuit 6 and a design data development unit 6.
and one of the three signals from the right detector 4 is selected. Since this embodiment has a configuration in which the main parts of the present invention are added to the conventional example, only the operation of the present invention will be explained.

Figure 2 shows a schematic diagram of the inspection principle. In FIG. 2, patterns corresponding to pixels of the photodiode play are arranged in a length l range in the vertical direction.

9 and 1o represent patterns corresponding to one pixel.

When patterns of a size equivalent to one pixel are arranged in the horizontal direction, the period at which the same pattern is repeated is defined as m. Pattern inspection is performed as follows using a single lens and a signal delay circuit.

1. Starting from the pattern 9 in FIG. 2, the signals of the pattern are sequentially taken into the photodiode array for each pixel, and
All signals within a range of 1 are captured. During this time, the stage moves by the width of the pixel, and the signals of b5 and the column on the right are sequentially captured from the bottom. While repeating this operation, signals of the pattern are sequentially input from left to right within the range of length e in the vertical direction. Since the same pattern is repeated at a period m in the horizontal direction, the same signal is repeatedly obtained every time a pattern with an area of /Xm is inspected. Let this period be T. In the signal delay circuit, the first
The signal from the photodiode array on the left side of the figure is delayed by time T. The signal from the photodiode array is expressed as f(
t), the signal from the signal delay circuit is f(t-τ)
becomes. Comparing f(t) and f(t-T) with a comparison judge, if there is no defect, f(t)=f(t0-T)
However, if there is a defect, 0 f(t)→f(t1-'r). In this case, the pattern 1 defect is determined by its size, that is, f(t)”rf (
The number of pixels, the coordinates of the stage, etc. that correspond to t −T ”) are stored.

In FIG. 2, the period m in which the same pattern is repeated in the horizontal direction may not match an integral multiple of the pixel width (horizontal size). In this case, electrical magnification adjustment is performed to change the pixel width to match.

As described above, according to this embodiment, a signal delay circuit is added to the conventional pattern inspection device, and the signal from the photodiode array and that signal are delayed by the period of the repeated pattern by the signal delay circuit. By comparing the signals,
It is possible to inspect repeating pattern defects within a single chip.

In this embodiment, the pattern detector is a photodiode, but the pattern detector may also be an image pickup tube or the like.

Naturally, the present invention can also be implemented using a two-dimensional detector.

Effects of the Invention The present invention provides a pattern detector that converts an image of a test pattern formed using an objective lens into an electrical signal, and a signal delay circuit that delays the signal from this pattern detector for a certain period of time. By comparing the signal from the detector with the signal delayed by the period of the repeated pattern using a comparison/judgment device, even in the case of a single chip, if there is a repeated part, that part can be inspected. This makes it possible to realize a possible pattern inspection device. Furthermore, the present invention can be easily realized by partially modifying the conventional pattern inspection apparatus (regardless of whether it is a chip comparison type or a data comparison type) by adding a signal delay circuit to the conventional pattern inspection apparatus.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a pattern inspection device according to a third embodiment of the present invention, FIG. 2 is a schematic diagram of the inspection principle of the present invention, and FIG. 3 is a diagram showing the configuration of a conventional pattern inspection device. It is a diagram. 1.11...Test photomask, 2.12...
...Illumination light, 3,13...Objective lens, 4
, 14... Photodiode array, 6, 15
・・・・・・Design data development Unisoto, 6・・・・・・
Signal delay circuit, 7, 1e...signal switcher,
8, 17... Comparison judge, 9, 10...
・Pattern for one pixel. 3rd Figure II -11 Loincloth test mask l2--Ikkuro Moekou t3 --- jj phantom lens 1 t4--Photography size-F array/5--''a total te'-)JN Unit l6--One-dango review so head nose f7--K

Claims (1)

[Claims] a pattern detector that converts an image of a test pattern formed using an objective lens placed on a sample into an electrical signal; a signal delay circuit that delays a signal from the pattern detector for a certain period of time; A pattern inspection device comprising a comparison/judgment device that compares a signal from a detector and a signal from a signal delay circuit.