JPH0410968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for detecting a pattern on a wafer that automatically detects the appearance of a pattern on an LSI wafer or the like.

[Background of the Invention] Semiconductor devices are manufactured on a Si substrate by repeating film formation, exposure, and etching, and at this time, many devices are formed regularly on a matrix on a Si substrate at once. . By the way, during this manufacturing process, if the required pattern is not formed correctly due to dust or inadequate process conditions, the semiconductor element will not be able to function.
In the process of forming each pattern, pattern defects or the suitability of process conditions are usually inspected. Conventionally, these inspections were performed visually by humans using a microscope, which was inefficient and As the width becomes smaller, reliability is also decreasing. For this reason, there has recently been an active movement to automate these tests. Incidentally, this movement toward automation has focused on inspecting shape defects existing in patterns, and a typical inspection apparatus that has been proposed in the past is shown in FIG. LSI
The wafer 1 has completely identical circuit patterns 2a, 2.
Since a plurality of chips having b... are regularly arranged, the same patterns 2a, 2b... of two adjacent chips are illuminated with illumination lights 3a, 3b and magnified by two objective lenses 4a, 4b. death,
After forming images on the image pickup tubes 5a and 5b and converting them into electrical signals,
Binarization is performed by binarization circuits 6a and 6b. This 2
The digitized signals are compared by a comparison circuit 7, and if a difference is found, it is detected as a defect. However, with this device, as circuit patterns become finer, it is necessary to increase the magnification of the objective lens and create a larger magnified image using the image pickup tube in order to detect even smaller defects. Along with this, there are problems such as the area that can be viewed at one time becomes narrower and the inspection time increases significantly. In addition, although this device can inspect for shape defects, it cannot inspect for irregularities in the pattern film thickness that occur during the manufacturing process, or for the quality of cleaning performed after etching, so visual inspection by humans is required again. Therefore, there were problems that did not necessarily lead to significant cost reductions or yield improvements.

[Object of the Invention] The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to very efficiently inspect semiconductor wafers for defects such as film thickness unevenness caused by process conditions and contamination defects such as poor cleaning. An object of the present invention is to provide a method and apparatus for detecting patterns on a wafer, which are capable of detecting patterns on a wafer and which can also reliably inspect shape defects in patterns that require detailed inspection.

[Summary of the Invention] In order to achieve the above object, the present invention solves the problem of film thickness unevenness caused by instability in the wafer manufacturing process.
Focusing on the fact that defects due to dirt and the like change in surface color, the light images from each pattern on the wafer, which are originally the same, are analyzed at low magnification through a low-magnification objective lens. The light is divided into two parts by a spectroscopic means, and is received by a photoelectric conversion means to detect each low magnification hue image signal, and the detected low magnification hue image signals are compared with each other to find the difference between them. , a hue defect detection step of determining a hue defect (a hue defect due to uneven film thickness, dirt, etc.) when the difference is greater than a predetermined value; and after determining a hue defect in the hue defect detection step, the low magnification An objective lens switching process in which an objective lens is switched to a high-magnification objective lens, and a light image from each pattern of adjacent originally identical patterns on the wafer is transferred to a high magnification objective lens through the high-magnification objective lens switched in the objective lens switching process. A shape defect detection step of forming an enlarged image at a magnification and receiving the light with a photoelectric conversion means to detect each enlarged image signal, and comparing the detected enlarged image signals to detect a shape defect based on the difference. A second invention is a method for detecting patterns on a wafer, which is characterized in that it has the following features:
an objective lens switching means for switching an objective lens for forming a light image from each pattern from a low magnification objective lens to a high magnification objective lens; It has a hue image detection means for macroscopically forming a light image from each pattern at a low magnification, splitting the light by a spectroscopic means, receiving the light by a photoelectric conversion means, and detecting each low magnification hue image signal. A hue defect detection means compares each of the low-magnification hue image signals detected by the hue image detection means and determines a hue defect when the difference is greater than a predetermined value, and the objective lens switching means increases the objective lens. It has an enlarged image detection means for enlarging the light image from each of the patterns at a high magnification and receiving the light with a photoelectric conversion means to detect each enlarged image signal while the magnification objective lens is switched to the magnification objective lens. A pattern detecting device on a wafer is characterized in that it is equipped with a shape defect detection means for comparing each enlarged image signal detected by the enlarged image detection means and detecting a shape defect based on the difference between the enlarged image signals.

[Embodiments of the Invention] In the following, an embodiment of the present invention will be explained with reference to FIG. 2, in which reference numeral 1 indicates an object to be inspected such as a wafer. Reference numerals 8 and 9 are objective lenses that can be selectively used by a switching mechanism (not shown) such as a revolver of a microscope. Regarding the relationship between the objective lenses 8 and 9, for example, the lens 8 has a low magnification of about 10 times, and the lens 9 has a high magnification of about 60 times. 10
1 is a light source that illuminates the surface of the wafer, and 11 and 12 are half mirrors that allow the straight light from the light source to pass therethrough, and each serves to bend the light from the objective lens toward the right in the figure. Reference numeral 13 is a half mirror, which has the role of splitting the light by allowing part of the light to pass through and reflecting the part of the light. half mirror 1
4 is also similar to the half mirror 13. Further, 15 serves as a mirror and serves to bend light. 1
Reference numerals 6, 17, and 18 are color filters that allow only certain wavelengths of light to pass through each filter and specify the wavelengths that enter the photoelectric converters 19, 20, and 21. 22 is an arithmetic unit, and photoelectric converters 19 and 2
Arithmetic processing is performed on the image signal converted by 0 and 21. For example, red as a color filter,
The blue and yellow wavelengths are selected, and calculations such as determining the hue are performed from the electrical signals from the photoelectric converter.
Reference numeral 23 denotes a memory circuit that stores hue data for one chip formed on the wafer. Reference numeral 24 denotes a comparison/judgment device which compares the data stored in the storage circuit 23 with the data currently obtained through inspection to determine whether there is a difference between the two. On the other hand, the photoelectric converter 25 converts the image of the light reflected by the half mirror 11 into an electrical signal. Reference numeral 26 is a storage circuit that stores image data for one chip. Reference numeral 27 is a comparison/judgment device that compares the data in the storage circuit 26 with the data currently obtained through inspection to see the difference between the two. The inspection method for the above configuration will be described below. After placing the wafer on a predetermined XY table (not shown), a low-magnification objective lens 8 is selected. The light of the image of the pattern on the wafer surface by the objective lens 8 is bent to the right by the half mirror 12.
3, 14, branched into 3 optical paths by mirror 15,
The light is further divided into spectra by color filters 16, 17, and 18. Each of the separated lights is converted into an electrical signal by photoelectric converters 19, 20, and 21, and is input to a computing unit. A computing unit calculates the hue from these three types of input signals and sequentially inputs the results into the storage circuit 23. The XY stage on which the wafer is placed is scanned, and once the data for one chip formed on the wafer has been input into the memory circuit 23, the XY stage is further scanned, and the data of the next chip is sequentially transferred to the arithmetic unit 23.
Expel it by 2. The data stored in the memory circuit 23 is synchronously outputted in accordance with the timing of this output. This is data stored in the memory circuit 23 at the same location one chip ago, so if the data from the memory circuit 23 and the data currently obtained from the arithmetic unit are compared by the comparator 24, it is possible to If the chips have the correct hue, there is no difference between these two pieces of data. However, if process conditions become unstable and defects such as uneven film thickness occur, or if cleaning after etching is poor and defects such as dirt occur, surface changes occur and these two types of data cannot be used. There will be a difference in position between them. Therefore, by displaying hue defects with a certain predetermined difference using the comparison/judgment device 24, it becomes possible to inspect wafer defects based on hue changes. Since the hue defect inspection is not related to the size of the pattern, it can be inspected macroscopically at low magnification, making it possible to significantly shorten the inspection time.

However, this macroscopic inspection method using low magnification cannot find small defects in the pattern. Therefore, in order to inspect the pattern for small shape defects, we first installed a switching mechanism (not shown).
is activated to select the objective lens 9 with high magnification. The light image of the pattern from the objective lens 9 is guided by the half mirror 11 to the photoelectric detector 25 and formed into an image. Here, it is converted into an image signal, and the brightness image data for one chip is first stored in the storage circuit 26. Therefore, the comparison judger 25
By comparing the image signal obtained by the next chip with the image data stored in the storage circuit 26 and determining a mismatch, it is possible to inspect the pattern for shape defects.

As explained above, by operating the switching mechanism (not shown) and switching the objective lenses 8 and 9, defect inspection using hue change at low magnification and shape defect inspection at high magnification can be performed in an appropriate combination. For example, hue defects and pattern shape defects on wafers can be inspected very efficiently. For example, first inspect the entire wafer surface at low magnification in a short time to find hue defects, and then detect changes in hue as a result of low magnification inspection, as many pattern shape defects also occur in areas where the hue changes. The area marked by the arrow is set as a defect candidate point for the shape defect inspection, and a switching mechanism (not shown) is operated to switch the objective lenses 8 and 9 to high magnification to obtain detailed information about the defect candidate point. A method of performing shape defect inspection is also possible. In addition, when this inspection device is used directly connected to a production line in the manufacturing process, it is possible to inspect hue changes at high magnification, and shape inspection at high magnification can also be used for detailed inspections such as defect analysis. It is possible. In this embodiment, a method is described in which spectroscopy is performed using a half mirror and a color filter for hue detection, but it goes without saying that other devices capable of color separation, such as a dichroic mirror, may also be used.

[Effects of the Invention] As explained above, according to the present invention, the objective lens has a relatively low magnification, and the hue change can be observed macroscopically.
By comparing and inspecting adjacent patterns that are essentially the same, it is possible to very efficiently inspect semiconductor wafers for defects such as film thickness unevenness caused by process conditions and contamination defects such as poor cleaning. Moreover, based on the above hue change inspection data, the objective lens is switched to high magnification and the enlarged images are compared and inspected for adjacent patterns that are originally the same, so the shape of the pattern that needs to be inspected in detail Defects can also be reliably inspected, inspection work efficiency can be improved, and the production of defective semiconductors can be reduced, resulting in a significant improvement in yield.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional pattern detection device, and FIG. 2 is a block diagram showing an embodiment of the pattern detection device according to the present invention. 1: Wafer, 8: Objective lens, 9: Objective lens, 16, 17, 18: Color filter, 19, 2
0, 21: Photoelectric converter, 22: Arithmetic unit, 23: Memory circuit, 24: Comparison/judgment device, 25: Photoelectric converter,
26: Memory circuit, 27: Comparison/judgment device.

Claims (1)

[Claims] 1. For adjacent patterns on a wafer that are essentially the same, optical images from each pattern are macroscopically imaged at low magnification through a low-magnification objective lens, and separated by a spectroscopic means to generate photoelectrons. A hue defect detection step of receiving light with a converting means and detecting each low magnification hue image signal, comparing the detected low magnification hue image signals with each other, and determining a hue defect when the difference is greater than a predetermined value. and an objective lens switching step of switching the low magnification objective lens to a high magnification objective lens after determining a hue defect in the hue defect detection step, and regarding adjacent originally identical patterns on the wafer,
The light image from each pattern is magnified at high magnification through the high magnification objective lens switched in the objective lens switching step, and is received by the photoelectric conversion means to detect each magnified image signal. A method for detecting a pattern on a wafer, comprising a shape defect detection step of comparing each enlarged image signal and detecting a shape defect based on the difference. 2. objective lens switching means for switching an objective lens for forming light images from each pattern from a low magnification objective lens to a high magnification objective lens for adjacent patterns on the wafer that are essentially the same; and by the objective lens switching means. With the objective lens switched to a low-magnification objective lens, the light images from each of the patterns are macroscopically formed at low magnification, separated by a spectrometer, and received by a photoelectric conversion means to form each low-magnification hue image. Hue defect detection comprising a hue image detection means for detecting a signal, comparing each low magnification hue image signal detected by the hue image detection means and determining a hue defect when the difference is greater than a predetermined value. means, and with the objective lens switching means switching the objective lens to a high magnification objective lens, the light images from the respective patterns are magnified and formed at high magnification and received by the photoelectric conversion means to produce each enlarged image. The present invention is characterized by comprising an enlarged image detection means for detecting a signal, and a shape defect detection means for comparing the enlarged image signals detected by the enlarged image detection means and detecting a shape defect based on the difference. A device for detecting patterns on wafers.