JP3615430B2 - Recognition mark - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recognition mark, and more particularly to a recognition mark for pattern superposition used when performing superposition through image recognition during an exposure process of a semiconductor device.
[0002]
[Prior art]
In an exposure process for forming a circuit pattern for manufacturing a semiconductor integrated circuit device, a circuit pattern formed of a chromium film that blocks light used for exposure on a glass substrate (hereinafter referred to as a reticle) is reduced on a semiconductor substrate coated with a resist. An apparatus (hereinafter referred to as a stepper) that projects and forms a circuit pattern for each shot (exposure) region is used.
[0003]
In a semiconductor integrated circuit device, a pattern is formed by repeating a process of exposing a semiconductor substrate a plurality of times and an etching process. Here, in order to form the second and subsequent layers on the semiconductor substrate after forming the first layer pattern, it is necessary to accurately superimpose the circuit pattern image of each shot region and the reticle. In order to perform overlay accurately, a recognition mark is formed on the first layer pattern simultaneously with the circuit pattern, the position of the recognition mark is recognized, the overlay position of the second layer pattern is determined, and exposure is performed. It is common to do this.
[0004]
As a method for recognizing the position of the recognition mark, there are a method of irradiating the corresponding recognition mark with a laser beam and detecting it by its diffracted light, and a method of detecting it by image recognition of the mark. In most cases, the recognition mark detected by the image recognition has a line pattern formed by convex portions or concave portions arranged at regular intervals.
[0005]
Hereinafter, a configuration of a recognition mark used for conventional image recognition will be described with reference to the drawings. FIG. 5 is a configuration diagram of a conventional recognition mark, FIG. 5 (a) is a plan view of a recognition mark used for concave image recognition, and FIG. 5 (b) is along the line XX ′ in FIG. 5 (a). It is sectional drawing.
[0006]
As shown in FIG. 5, main patterns 2A, 2B, 2C, and 2D made of concave grooves are formed on the surface of the semiconductor substrate 1, and a plurality of main patterns 2A to 2D are arranged in parallel at regular intervals. Thus, a concave recognition mark 2X used for image recognition is configured. The thus configured recognition mark 2X is detected and recognized by the stepper as a conversion of the contrast between the center of the recognition mark, that is, the recess and the periphery of the recognition mark into an electrical signal.
[0007]
[Problems to be solved by the invention]
However, in such a configuration, since the image contrast of the recognition mark at the time of image recognition is weak with respect to the overlay accuracy of each pattern in the exposure process required along with the miniaturization of the pattern of the semiconductor integrated circuit device, it is detected by the stepper. There is a problem that the shape of the image signal waveform to be performed is poor and therefore the overlay accuracy is low.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a recognition mark that can improve the overlay accuracy of circuit patterns in an exposure process of a semiconductor device.
[0009]
[Means for Solving the Problems]
The recognition mark of the present invention is a recognition mark for pattern superposition formed on a substrate, the main pattern having a rectangular frame (wax) formed by a concave portion or a convex portion of the substrate, Each of the main patterns is formed by a concave portion or a convex portion of the substrate and has a wavelength of light that irradiates the recognition mark or a length close to the wavelength, and a wavelength of the light or a constant interval close to the wavelength. It has a large number of sub-patterns arranged regularly.
[0010]
According to the present invention, the light irradiated to the recognition mark for recognition is reflected, interfered, and scattered by the sub-pattern to improve the contrast of the recognition mark image, so that the circuit pattern overlay accuracy can be improved. Become.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol shall be used about the same part as the said conventional thing.
[0012]
(Embodiment 1)
Figure 1 is a block diagram of the first embodiment of the recognition mark of the present invention, FIG. 1 (a) is a plan view of a concave recognition mark, A of FIG. 1 (b) FIGS. 1 (a) - A 'line FIG.
[0013]
As shown in FIG. 1, main patterns 3A, 3B, 3C, and 3D formed on a semiconductor substrate 1 are formed as large rectangles, and sub-patterns 31A configured as small rectangles among the rectangles of the main patterns 3A to 3D. , 31B, 31C, 31D are provided, and a recognition mark 3X is configured. Here, the length of each side of the main patterns 3A to 3D is about 50 μm to 100 μm in the vertical direction and 5 μm to 10 μm in the horizontal direction, and the pattern interval is also about the same as the horizontal width. The sub patterns 31A to 31D are formed in an island shape, and a plurality of sub patterns 31A to 31D are arranged in parallel in the main patterns 3A to 3D. A recess is formed between the rectangles of the main patterns 3A to 3D and the islands of the sub patterns 31A to 31D, and can be obtained by etching an insulating film or a conductive film formed on the semiconductor substrate 1, for example. Therefore, the depth of the concave portion is determined depending on these film thicknesses.
[0014]
The length in the short side direction or the interval between the islands of the sub-patterns 31A to 31D has a size close to the wavelength of monochromatic light such as a halogen lamp that emits light in the visible light range provided in the stepper used for this recognition. Yes. Since the stepper used in the manufacturing process of the semiconductor device has a capability of forming a pattern of 0.5 μm or less, the sub-patterns 31A to 31D can be sufficiently processed even if they are small.
[0015]
As described above, according to the present embodiment, when the recognition mark is irradiated with the mark image recognition light when the circuit pattern is superimposed in the exposure process, the individual islands arranged in the main pattern are overlapped. The reflected light is interfered or scattered to improve the contrast between the recognition mark region and its peripheral region, clarify the shape of the signal waveform during image recognition, and improve the accuracy of overlay measurement.
[0016]
In addition, in the recognition mark 3X shown in FIG. 1, a concave recognition mark obtained by etching a film formed on the substrate is used. However, one or a plurality of layers deposited and grown on the substrate are etched to form a sub-pattern. Only the islands of 3 1A to 3 1D arranged as in FIG. 1A can be used as recognition marks. In other words, there is no “wax” corresponding to the main patterns 3A to 3D, and a large number of sub-patterns form one group, and these groups are arranged at regular intervals. In this case as well, the reflected light from the islands of the sub-patterns 31A to 31D is interfered or scattered similarly to the recognition mark 3X in FIG. 1, and the contrast between the recognition mark area and the surrounding area is improved. However, the recognition mark in which the main patterns 3A to 3D exist is more preferable because it recognizes the “wak” and the signal corresponding to the mark image becomes clear.
[0017]
In addition, a recognition mark in which a region which is a concave groove in FIG. 1A is a convex portion on the opposite side and the other portion is a concave portion is also possible. In this case, a convex portion is formed between the islands of the sub-pattern in FIG. 1, and the light for image recognition is reflected and scattered, so that the contrast between the recognition mark area and the surrounding area is improved.
[0018]
(Embodiment 2)
FIG. 2 is a configuration diagram of the recognition mark according to the second embodiment of the present invention. FIG. 3 is a plan view of the recognition mark in which the sub-pattern in the main pattern including the recesses is formed as a convex pattern. FIG. It is another block diagram in Embodiment 2 of a mark, It is a top view of the recognition mark in which the sub pattern in the main pattern which consists of a recessed part is formed in the uneven | corrugated | grooved part.
[0019]
Recognition mark 4X main pattern 4A consisting of the recess shown in FIG. 2, 4B, 4C, the sub-patterns 41A in 4D, 41B, 41C, 41D is an approximately square island 2 dimensional convex pattern which is regularly arranged in rows and columns In addition, the recognition mark 5X shown in FIG. 3 is formed by sub-patterns 51A, 51B, 51C, and 51D in the main patterns 5A, 5B, 5C, and 5D that are formed of recesses. The recognition mark 5X is formed by parallel concavo-convex portions, and the width and interval of the inclined concave portions are close to the wavelength of light for image recognition.
[0020]
As described above, according to the present embodiment, when the recognition mark 4X or 5X is irradiated with the mark image recognition light when the circuit patterns are overlapped in the exposure process, there are sub patterns arranged in the main pattern. Since they are regularly arranged according to a certain rule and the length of one of them is close to the wavelength of light used for mark recognition, the intensity of the recognized image contrast signal can be improved by reflected interference light and scattered light from the subpattern.
[0021]
The shape of the sub-pattern as shown in FIGS. 2 and 3, for example, in which a large number of small circular islands are regularly arranged in the main pattern, exhibits the same effect.
[0022]
(Embodiment 3)
The concave recognition mark shown in the first embodiment of FIG. 1 is usually obtained simultaneously with the step of etching a film formed for processing a circuit pattern on a semiconductor substrate, and the next step of this etching. Is a photolithographic process, superposition is performed by a stepper using the concave recognition mark shown in the first embodiment. However, when the next process of such an etching process is not an exposure process but a film forming process, the configuration shown in this embodiment mode is adopted.
[0023]
Figure 4 is a block diagram of Embodiment 3 of the recognition mark of the present invention, FIG. 4 (a) is a plan view of a concave identification mark, B in FIG. 4 (b) FIGS. 4 (a) - B 'line FIG.
[0024]
In the recognition mark 7X shown in FIG. 4, the concave portions of the main patterns 7A, 7B, 7C, and 7D and the sub patterns 71A, 71B, 71C, and 71D are embedded by growing or depositing an embedded material 6 such as an insulator or metal. Is. As described above, the effect obtained when the overlay measurement by the image recognition is performed using the recognition mark 7X in which the concave portions of the main patterns 7A to 7D and the sub patterns 71A to 71D are embedded with the embedding material 6 is the first embodiment. As a result, the contrast of the recognition mark can be improved as compared with the conventional case.
[0025]
There are a plurality of steps in a specific semiconductor device in which the recognition mark 7X is formed. First, in the step of forming the element isolation / isolation groove on the semiconductor substrate, the element isolation / isolation groove is formed in the semiconductor substrate by etching, and at the same time, the concave portion of the recognition mark 7X is formed. The concave portion of the recognition mark 7X is filled with the same insulating film to complete the configuration shown in FIG. Further, in the step of forming the gate electrode of the MOS type semiconductor device on the semiconductor substrate, the gate electrode is formed by etching and the concave portion of the recognition mark 7X is formed, and the concave portion is embedded in the side wall insulating film forming step of the gate electrode. This is because the width of the recess is very narrow. In addition, a concave portion of the recognition mark 7X is formed in the contact hole forming step, and the concave portion is buried by filling the contact hole with tungsten or the like. Further, the concave portion of the recognition mark 7X is formed by metal wiring etching, and the concave portion is filled by forming an interlayer insulating film on the wiring.
[0026]
As described above, according to the present embodiment, when the circuit pattern is overlapped in the exposure process and the recognition mark is irradiated with light for mark image recognition, the sub-pattern in the main pattern is the same as in the above-described embodiments. The reflected image contrast light and scattered light from the light source improve the recognized image contrast signal intensity, clarify the shape of the signal waveform during image recognition, and improve the accuracy of overlay measurement.
[0027]
Note that the recognition mark described in each of the above embodiments applies not only to a stepper type exposure apparatus but also to a scanning type exposure apparatus that performs exposure by relatively scanning a reticle and a wafer. Can do. Further, each of the above embodiments is not limited to the above aspect.
[0028]
【The invention's effect】
As described above, according to the present invention, a large number of sub-patterns having a length close to the wavelength of the light source for recognition are formed on the substrate, and these are arranged regularly at regular intervals close to the wavelength of the light source. The shape of the contrast signal waveform at the time of image recognition of the recognition mark can be clarified, thereby obtaining an advantageous effect that the overlay accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram of a recognition mark according to a first embodiment of the present invention. FIG. 2 is a block diagram of a recognition mark according to a second embodiment of the present invention. FIG. 4 is another configuration diagram of the recognition mark according to the third embodiment of the present invention. FIG. 5 is a configuration diagram of a conventional recognition mark.
1 Substrate 2A-2D, 3A-3D, 4A-4D, 5A-5D, 7A-7D Main pattern of recognition mark
2X, 3X, 4X, 5X, 7X Recognition mark 6 Embedding materials 31A to 31D, 41A to 41D, 51A to 51D, 71A to 71D Subpattern of recognition mark

Claims (3)

A recognition mark for pattern superposition formed on the substrate, the main pattern having a rectangular frame formed by a concave portion or a convex portion of the substrate, and the substrate in each internal region of the main pattern A plurality of sub-patterns that are formed by concave or convex portions of the light source and have a wavelength of light that irradiates the recognition mark or a length close to the wavelength, and are regularly arranged at a certain interval close to the wavelength of the light or the wavelength. A recognition mark characterized by having it. 2. The recognition mark according to claim 1, wherein a plurality of sub-patterns are arranged in a plurality at a predetermined interval. 2. The recognition mark according to claim 1, wherein a plurality of main patterns are arranged at regular intervals.

Images