JPH05107726A - Verification device for design data on phase shift mask - Google Patents

Abstract

PURPOSE:To easily verify the design data on the phase shift mask for semiconductor integrated circuit transfer at low cost in a short time without actually manufacturing any mask. CONSTITUTION:A desired pattern is processed by a bit map expanding circuit 1 and stored in a memory circuit 2. The light shield pattern and shifter pattern of the phase shift mask are processed by bit map expanding circuits 3 and 4 respectively and stored in memory circuits 5 and 6. Both image signals are put together by a memory circuit 7 and processed by a mask optical image forming circuit 8 into an optical image, which is stored in a memory circuit 9. A comparative arithmetic circuit 10 verifies images of both the memory circuits 2 and 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask for transferring a pattern onto a semiconductor substrate, and more particularly to a device for verifying the pattern design data without actually manufacturing the mask.

[0002]

2. Description of the Related Art A semiconductor integrated circuit is manufactured by transferring a pattern of the integrated circuit to a semiconductor substrate in each step. For this transfer, a light-shielding material such as Cr or MoSi formed on quartz glass is used. A reticle mask having a pattern (hereinafter, simply referred to as a mask) is used. Then, it is necessary to verify whether this mask matches the desired design data.

FIG. 7 shows a CA for verifying this mask.
It is a block diagram which shows the outline of a D system. In the figure, 6
Reference numeral 2 is a central processing unit having arithmetic and main memory functions, and 61 is a graphic terminal device for displaying design data relating to the integrated circuit pattern stored in the auxiliary memory unit 63. In the conventional design verification work, the CAD system shown in FIG. 7 is used, and the operator operates the central processing unit 62 to read the design data stored in the auxiliary storage device 63 and display it on the graphic terminal device 61. It was to visually inspect whether the desired pattern was obtained.

[0004]

Since the conventional verification apparatus is constructed as described above, it is possible to verify a mask composed of only a light-shielding pattern, but recently it is necessary to further miniaturize the pattern. It cannot be applied as it is to the phase shift mask that has received attention. That is, the phase shift mask partially controls the phase of light passing through the mask by forming an optical member called a phase shifter on the mask, and improves the resolution of the transferred optical image. , Light propagation is expressed by a complex number of amplitude and phase, and the light intensity actually imaged on the semiconductor substrate is expressed by the square of the complex number expression. Therefore, the pattern image obtained by the phase shift mask cannot be visually inspected unless the phase shift mask is actually prototyped and transferred and imaged. As a result, there is a problem that a secondary work such as mask production and transfer is required, and the cost of the verification work is significantly increased.

The present invention has been made in order to solve the above problems, and it does not require the work of actually manufacturing a mask and transferring it onto a semiconductor substrate, and verification in a short time and at a low cost. An object of the present invention is to obtain a phase shift mask design data verification device that enables

[0006]

According to a first aspect of the present invention, there is provided a phase shift mask design data verifying device for bit map developing design data of a desired integrated circuit pattern.
Bit map expansion circuit, second and third bit map expansion circuits for expanding the design data of the light-shielding pattern and the shifter pattern of the phase shift mask, respectively, and the bits from the second and third bit map expansion circuits. A mask optical image forming means for forming an optical image formed by synthesizing map images on a semiconductor substrate,
And a comparison operation circuit for comparing information from the first bit map expansion circuit and the mask optical image forming means.

According to a second aspect of the present invention, the mask optical image forming means is provided with a storage medium capable of storing the light intensity and the optical phase for each unit pixel. An image storage circuit that synthesizes and stores the bitmap image from the expansion circuit, a Fourier transform circuit that converts the image information from this image storage circuit into a spatial frequency,
It is composed of a spatial filter circuit having an optical transfer characteristic of a transfer device to a semiconductor substrate, and an inverse Fourier transform circuit for inversely transforming the information from the Fourier transform circuit passing through the spatial filter circuit into real image information.

According to a third aspect of the present invention, the mask optical image forming means of the first aspect is used as a light source for emitting parallel light beams that are directly coupled and deflected, and a second bitmap expansion is arranged on the optical path from the light source. A light-shielding filter for inputting information from the circuit to shield the light-shielding pattern portion of the phase shift mask, and also a shifter pattern portion of the phase shift mask for inputting information from the third bitmap expansion circuit which is also arranged on the optical path from the light source. Of the deflection filter for deflecting the transmitted light of the above in the opposite phase, and the image input device for inputting the light transmitted through the both filters through the lens having the optical transfer characteristic of the transfer device to the semiconductor device and converting it into the electric information. It was done.

[0009]

In the present invention, the light-shielding pattern and the shifter pattern of the phase shift mask are expanded into a bitmap,
Further, the mask optical image forming means synthesizes the bit map images to obtain a final image formation, and verifies the optical image by comparing it with an image obtained by expanding desired design data into a bit map.

According to a second aspect of the present invention, the bitmap images of the light-shielding pattern and the shifter pattern of the phase shift mask are combined and stored as two elements of light intensity and optical phase, and this information is stored in space. An actual optical image is obtained by converting the frequency to a frequency and then applying it to a spatial filter circuit having the optical transfer characteristic of the actual transfer device and inversely converting it. Then, the image obtained here is compared with the image related to the desired design data to be verified.

According to the third aspect of the present invention, the parallel rays from the light source pass through the light blocking filter and the deflection filter, and the transmitted light passes through the lens to be converted into an actual optical image by the image input device. Then, the image obtained here is compared with the image related to the desired design data to be verified.

[0012]

【Example】

First Embodiment FIG. 1 is a block diagram showing a phase shift mask design data verification device (hereinafter simply referred to as a verification device) according to a first embodiment of the present invention. In the figure, 1 is a first bit map developing circuit for bit map developing design data of a desired integrated circuit pattern serving as a reference, 2 is a memory circuit for storing the pattern image from the bit map developing circuit 1, and 3 is a phase shift. A second bit map expansion circuit for expanding the light-shielding pattern data of the mask (the structure of which will be described later) into a bitmap, a third bit map expansion circuit for expanding the shifter pattern data of the phase shift mask into a bit map, 5
Is a memory circuit for storing the pattern image from the bit map expansion circuit 3, 6 is a memory circuit for storing the pattern image from the bit map expansion circuit 4, and 7 is a combination of the two pattern images from both memory circuits 5 and 6. A memory optical circuit 8 for storing a mask optical image forming circuit 8 for forming an optical image formed on an actual semiconductor substrate from a mask pattern image of the memory circuit 7. Details will be described later. 9 is a memory circuit for storing the formed optical image,
Reference numeral 10 is a comparison operation circuit for comparing electric signals of the memory circuit 2 storing a desired integrated circuit pattern and the memory circuit 9 storing a mask optical image.

2 and 3 are a sectional view and a design drawing showing a phase shift mask of interest here. In FIG. 2, 11 is a transparent glass substrate such as synthetic quartz, 1
Reference numeral 2 is a light-shielding pattern formed of a material such as Cr or MoSi, which blocks light incident on this portion. Reference numeral 13 denotes a shifter pattern formed of a material such as glass or resin, which shifts the phase of light incident on this portion by 180 °.

In FIG. 3A, reference numeral 21 is a plan view of a desired pattern on a semiconductor substrate, and 14 is a design data representing the desired pattern. FIG. 3B shows a plan view 22 of the phase shift mask data.
Is a light-shielding pattern, and 13 is a shifter pattern represented by design data. 3C is a plan view showing only the shifter pattern portion in FIG. 3B, and 24 in FIG. 3D is a plan view showing only the light shielding pattern portion in FIG. 3B. It is a figure.

Next, the operation will be described. The data representing the desired pattern 21 is converted into an image signal by the bit map expansion circuit 1 and stored in the memory circuit 2.
Further, the data representing the light-shielding pattern 24 is converted into an image signal by the shifter pattern and stored in the memory circuit 5, and the data representing the shifter pattern 23 is converted into an image signal by the bitmap expansion circuit 4 and stored in the memory circuit 6. The image signals of the memory circuits 5 and 6 are combined and stored in the memory circuit 7.

FIG. 4A shows a pattern image 41 of the phase shift mask stored in the memory circuit 7. In this circuit, not only the density of the image, that is, the intensity of the transferred light, but also the phase of the light is expressed. ing. In the figure, 12 indicates a portion where light is blocked (intensity 0), and 13 indicates a portion where light phase is shifted (intensity 1, phase 180 °). 12, 13
Except for the area where light is transmitted as it is (intensity 1, phase 0 °)
Indicates. The memory circuit having such information is similar to the image memory circuit having color information, but the color display is expressed by the combination of the intensities of the three primary colors, while this memory circuit is shown in FIG. As shown, each pixel has two pieces of information. That is, in the figure, 42 represents the intensity of light, and 43
Represents the phase of light.

Next, the details of the operation of forming the optical image actually formed on the semiconductor substrate from the image signal of the memory circuit 7 by the mask optical image forming circuit 8 will be described with reference to FIG. Once stored, the phase shift mask image 51 is converted into a spatial frequency by the Fourier transform circuit 52 and stored in the memory circuit 53 in this form. Here, the spatial frequency is a concept applied for the purpose of expressing an arbitrary light-dark distribution with a combination of sinusoidal components of various periods, and is not a repetition number per unit time, but a spatial unit length. It is expressed by the frequency.

Reference numeral 54 is a spatial filter circuit which expresses the optical transfer characteristic (lens characteristic) of the mask image transfer device onto the semiconductor substrate as a spatial frequency characteristic. The signal that has passed through the spatial filter circuit 54 is temporarily stored in the memory circuit 55, and then the inverse Fourier transform circuit 56 again restores the real image 57.
Converted to and stored.

As described above, the images stored in the two memory circuits 2 and 9 are verified by comparing with the comparison operation circuit 10, and if there is a difference, measures such as design review are considered.

Embodiment 2 FIG. 6 is a main part of a verification device according to Embodiment 2 of the present invention (see FIG.
3 is a configuration diagram showing a portion corresponding to the memory circuit 7 and the mask optical image forming circuit 8) of FIG. In the figure, reference numeral 31 is a light-shielding filter such as a liquid crystal panel which expresses a light-shielding pattern of a phase shift mask, which partially modulates only the intensity of light by an electric signal applied to this liquid crystal. Three
Reference numeral 2 is a deflection filter such as a liquid crystal panel which expresses a shifter pattern of a phase shift mask, and partially modulates only the phase of light by an electric signal applied to this liquid crystal, that is, shifts the linear deflection of light partially to the opposite phase. To do.

Reference numeral 33 denotes a linearly polarized parallel light beam, which passes through a light blocking filter 31 disposed on the optical path thereof to become a light beam 34 in which a portion of a light blocking pattern is blocked.
Further, by passing through the deflection filter 32, the shifter pattern portion becomes a light beam 35 that is shifted in antiphase. Then, this light ray 35 passes through a lens 36 having an optical transfer characteristic of an actual transfer device, and the image pickup element (image pickup tube) 3
The image is formed on the image signal No. 7, converted into an electric signal by the image pickup element 37, stored in the memory circuit 9 (FIG. 1), and compared and verified with the desired image signal as in the above-described embodiment.

As a method of synthesizing the images obtained by developing the light-shielding pattern and the shifter pattern of the phase shift mask in the respective bitmaps and forming the optical image actually formed on the semiconductor substrate, the above-described embodiment is used. It is not limited to those shown.

[0023]

Since the present invention is configured as described above, when a phase shift mask is newly designed, it is different from a desired mask pattern which is a reference without actually manufacturing the phase shift mask. Can be verified
Verification work is simple and can be done in a short time, and its cost is also reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a phase shift mask design data verification device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a phase shift mask.

FIG. 3 is a diagram showing a design pattern layout of a phase shift mask.

FIG. 4 is a diagram for explaining a memory circuit 7, which is a main part of the phase shift mask design data verification device according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining a mask optical image forming circuit 8 which is a main part of the phase shift mask design data verification device according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining a memory circuit 7 and a mask optical image forming circuit 8 which are essential parts of a phase shift mask design data verification device according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a conventional CAD system for performing mask verification.

[Explanation of symbols]

 1,3,4 Bitmap development circuit 2,5,6,7,9,53,55 Memory circuit 8 Mask optical image forming circuit 12 Light-shielding pattern 13 Shifter pattern 31 Light-shielding filter 32 Deflection filter 33 Linearly polarized light beam 36 Lens 37 image Imaging device as input device 52 Fourier transform circuit 54 Spatial filter circuit 56 Inverse Fourier transform circuit

Claims (3)

[Claims] 1. A first bit map expansion circuit for expanding a design data of a desired integrated circuit pattern into a bit map, and a second bit map expansion circuit for expanding design data of a light-shielding pattern and a shifter pattern of a phase shift mask, respectively. Bit map developing circuit, a mask optical image forming means for synthesizing the bit map images from the second and third bit map developing circuits to form an optical image formed on a semiconductor substrate, and the first bit map. A phase shift mask design data verification device comprising a comparison operation circuit for comparing information from a development circuit and mask optical image forming means. 2. The mask optical image forming means is provided with a storage medium capable of storing the light intensity and the optical phase for each unit pixel so that the bit map images from the second and third bit map developing circuits are combined. An image storage circuit to be stored as an image, a Fourier transform circuit for converting image information from the image storage circuit into a spatial frequency, a spatial filter circuit having an optical transfer characteristic of a transfer device to a semiconductor substrate, and the above-mentioned spatial filter circuit 2. The phase shift mask design data verification device according to claim 1, comprising an inverse Fourier transform circuit for inversely transforming information from the Fourier transform circuit into real image information. 3. The mask optical image forming means is a light source for emitting parallel light beams which are directly coupled and deflected, and information from a second bit map expansion circuit which is arranged on the optical path from this light source is inputted to shield the phase shift mask. A light blocking filter for blocking the pattern portion, a deflection filter which is also arranged on the optical path from the light source and receives the information from the third bitmap expansion circuit and deflects the transmitted light of the shifter pattern portion of the phase shift mask to the opposite phase, 2. The phase shifter according to claim 1, further comprising an image input device for inputting the light transmitted through the both filters through a lens having an optical transfer characteristic of a transfer device to a semiconductor device and converting the light into electrical information. Mask design data verification device.