JP2658679B2 - Phase shift mask design data verification device - Google Patents

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 to a semiconductor substrate, and more particularly to an apparatus for verifying pattern design data without actually manufacturing a mask.

[0002]

2. Description of the Related Art A semiconductor integrated circuit is manufactured by transferring a pattern of an integrated circuit onto a semiconductor substrate for each process. For this transfer, a light shielding material such as Cr or MoSi is formed on quartz glass or the like. 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 desired design data.

FIG. 7 shows a CA for verifying this mask.
It is a lineblock diagram showing the outline of D system. In the figure, 6
Reference numeral 2 denotes a central processing unit having an arithmetic and main storage function, and 61 is a graphic terminal device for displaying design data on an integrated circuit pattern stored in the auxiliary storage device 63. In the conventional design verification work, the operator operates the central processing unit 62 to read out the design data stored in the auxiliary storage device 63 and displays the design data on the graphic terminal device 61 using the CAD system shown in FIG. This is to visually verify whether or not a desired pattern has been obtained.

[0004]

Since the conventional verification apparatus is configured as described above, it is possible to verify a mask composed of only a light-shielding pattern. The phase shift mask that is receiving attention cannot be applied as it is. In other words, a phase shift mask partially controls the phase of light transmitted through the mask by forming an optical member called a phase shifter on the mask to improve the resolution of an optical image to be transferred. The propagation of light is represented by a complex number of amplitude and phase, and the light intensity actually imaged on the semiconductor substrate is represented by the square of the complex number representation. For this reason, the pattern image obtained by the phase shift mask cannot be visually inspected unless a phase shift mask is actually manufactured and transferred and imaged. As a result, there is a problem that a secondary operation such as manufacturing and transferring a mask is required, and the cost of the verification operation is greatly increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and does not require an operation of actually manufacturing a mask and transferring it onto a semiconductor substrate. It is an object of the present invention to obtain a phase shift mask design data verification device which enables the following.

[0006]

According to a first aspect of the present invention, there is provided a phase shift mask design data verification apparatus for developing a design data of a desired integrated circuit pattern into a bit map.
, And second and third bitmap development circuits for performing bitmap development of 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 bitmap development circuits. Mask optical image forming means for forming an optical image to be formed on a semiconductor substrate by synthesizing a map image,
And a comparison operation circuit for comparing information from the first bitmap development 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 light intensity and optical phase for each unit pixel, so that the second and third bitmaps are formed. An image storage circuit that synthesizes and stores a bitmap image from a development circuit, a Fourier transform circuit that converts image information from the image storage circuit into a spatial frequency,
It comprises 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 information from the Fourier transform circuit passed through the spatial filter circuit into real image information.

According to a third aspect of the present invention, there is provided a mask optical image forming means according to the first aspect, comprising a light source which emits a parallel light beam which is directly coupled and deflected, and a second bit map development which is arranged on an optical path from the light source. A light-shielding filter for inputting information from the circuit and shielding the light-shielding pattern portion of the phase shift mask; a shifter pattern portion of the phase shift mask which is also arranged on the optical path from the light source and receives information from the third bitmap developing circuit; A deflection filter for deflecting the transmitted light into opposite phases, and an image input device for inputting the light transmitted through both filters through a lens having an optical transmission characteristic of a transfer device to a semiconductor device and converting the light into electrical information. It was done.

[0009]

According to the present invention, a light-shielding pattern and a shifter pattern of a phase shift mask are developed in a bit map.
Further, the above-mentioned bitmap image is synthesized by the mask optical image forming means to obtain a final image, and this optical image is verified by comparing the optical image with an image obtained by developing desired design data into a bitmap.

According to a second aspect of the present invention, a bitmap image relating to a light-shielding pattern and a shifter pattern of a phase shift mask is synthesized and stored as two elements of light intensity and optical phase, and this information is spatially stored. The frequency is converted to a frequency and further applied to a spatial filter circuit having an optical transfer characteristic of an actual transfer device, and the actual optical image is obtained by performing an inverse conversion. Then, the image obtained here is compared with an image relating to desired design data and verified.

According to the third aspect, the parallel light from the light source passes through the light shielding filter and the deflection filter, and the transmitted light passes through the lens, and is converted into an actual optical image by the image input device. Then, the image obtained here is compared with an image relating to desired design data and verified.

[0012]

【Example】

Embodiment 1 FIG. 1 is a configuration 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, reference numeral 1 denotes a first bitmap development circuit for developing a reference integrated circuit pattern design data into a bitmap, 2 denotes a memory circuit for storing a pattern image from the bitmap development circuit 1, and 3 denotes a phase shift circuit. A second bitmap developing circuit for developing the light-shielding pattern data of the mask (the configuration of which will be described later) in a bitmap, a third bitmap developing circuit for developing the shifter pattern data of the phase shift mask in a bitmap, 5
Is a memory circuit for storing the pattern image from the bitmap development circuit 3, 6 is a memory circuit for storing the pattern image from the bitmap development circuit 4, and 7 is a combination of the two pattern images from both memory circuits 5 and 6. A memory circuit 8 for forming an optical image formed on an actual semiconductor substrate from a mask pattern image of the memory circuit 7; and a memory circuit 8 for the memory circuit 7 and the mask optical image forming circuit 8. Details will be described later. 9 is a memory circuit for storing the formed optical image,
Reference numeral 10 denotes 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.

FIG. 2 and FIG. 3 are a cross-sectional view and a design diagram showing a phase shift mask of interest here. In FIG. 2, reference numeral 11 denotes a transparent glass substrate made of synthetic quartz or the like;
Reference numeral 2 denotes 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, 21 is a plan view of a desired pattern on a semiconductor substrate, and 14 is a representation of the desired pattern by design data. FIG. 3B shows a plan view 22 of the phase shift mask data.
Denotes a light-shielding pattern, and 13 denotes a shifter pattern by design data. 3 (c) is a plan view showing only the shifter pattern portion of FIG. 3 (b), and 24 of FIG. 3 (d) is a plan view showing only the light shielding pattern portion of FIG. 3 (b). FIG.

Next, the operation will be described. Data representing the desired pattern 21 is converted into an image signal by the bitmap development circuit 1 and stored in the memory circuit 2.
The data representing the light-shielding pattern 24 is converted into an image signal by a 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 developing 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. This circuit expresses not only the shading of the image, that is, the intensity of the transfer light but also the phase of the light. ing. In the drawing, reference numeral 12 denotes a portion where light is blocked (intensity 0), and reference numeral 13 denotes a portion where the phase of light is shifted (intensity 1, phase 180 °). 12,13
Except for the part where light was transmitted as it was (intensity 1, phase 0 °)
Is shown. A memory circuit having such information is similar to an image storage circuit having color information, but a color display is represented by a combination of the intensities of the three primary colors, whereas 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
Represents the phase of light.

Next, the operation of forming an actual optical image 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 in detail with reference to FIG. The once stored 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 and dark distribution by a combination of sine wave components of various periods, and is not a repetition number per unit time but a spatial unit length. Expressed by the number of frequencies.

Numeral 54 denotes a spatial filter circuit for expressing the optical transfer characteristics (lens characteristics) of the transfer device of the mask image onto the semiconductor substrate as spatial frequency characteristics. The signal that has passed through the spatial filter circuit 54 is temporarily stored in a memory circuit 55, and is again stored in a real image 57 by an inverse Fourier transform circuit 56.
Is converted and stored.

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

Embodiment 2 FIG. 6 shows a main part (FIG. 1) of a verification apparatus according to Embodiment 2 of the present invention.
2 is a configuration diagram illustrating a memory circuit 7 and a portion corresponding to a mask optical image forming circuit 8). In the drawing, reference numeral 31 denotes a light-shielding filter such as a liquid crystal panel that expresses a light-shielding pattern of a phase shift mask, which partially modulates only light intensity by an electric signal applied to the liquid crystal. 3
Reference numeral 2 denotes a deflection filter such as a liquid crystal panel for expressing a shifter pattern of a phase shift mask, which partially modulates only the phase of light by an electric signal applied to the liquid crystal, that is, partially shifts the linear deflection of light to an opposite phase. Is what you do.

Numeral 33 denotes a parallelly deflected parallel light beam, which passes through a light-shielding filter 31 arranged on the optical path to become a light beam 34 whose light-shielding pattern portion is shielded.
Further, by passing through the deflection filter 32, the shifter pattern portion becomes a light beam 35 shifted in the opposite phase. The light beam 35 passes through a lens 36 having an optical transfer characteristic of an actual transfer device, and passes through an imaging device (imaging tube) 3.
7 is converted into an electric signal by the image pickup device 37, stored in the memory circuit 9 (FIG. 1), and compared with the desired image signal as in the above-described embodiment.

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

[0023]

Since the present invention is configured as described above, when a new phase shift mask is designed, the difference between the phase shift mask and a desired mask pattern which is a reference can be obtained without actually manufacturing the phase shift mask. Can be verified,
Verification can be performed easily and in a short time, and the cost can be reduced.

[Brief description of the 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 arrangement 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 main 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 expansion 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-deflected light beam 36 Lens 37 Image Image sensor 52 as input device 52 Fourier transform circuit 54 Spatial filter circuit 56 Inverse Fourier transform circuit

Claims (3)

(57) [Claims] 1. A first bitmap developing circuit for developing a design data of a desired integrated circuit pattern in a bitmap, and a second and third bitmap developing circuit for developing design data of a light-shielding pattern and a shifter pattern of a phase shift mask, respectively. , A mask optical image forming means for forming an optical image to be formed on a semiconductor substrate by combining the bitmap images from the second and third bitmap developing circuits, and the first bitmap A phase shift mask design data verification device including a comparison operation circuit for comparing information from a development circuit and mask optical image forming means. 2. A mask optical image forming means comprising a storage medium capable of storing light intensity and optical phase for each unit pixel, thereby synthesizing bitmap images from the second and third bitmap developing circuits. An image storage circuit for storing and storing image information, 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-described spatial filter circuit. 2. The phase shift mask design data verification device according to claim 1, further comprising an inverse Fourier transform circuit for inversely transforming information from the Fourier transform circuit into real image information. 3. A mask optical image forming means, comprising: a light source which emits a parallel light beam which is directly coupled and deflected; and a light source which is arranged on an optical path from the light source and which receives information from a second bitmap developing circuit to block a phase shift mask. A light-shielding filter that shields a pattern portion, a deflection filter that is also arranged on the optical path from the light source, receives information from a third bitmap development circuit, and deflects the transmitted light of the shifter pattern portion of the phase shift mask to an opposite phase; 2. A phase shifter according to claim 1, further comprising an image input device for inputting the light transmitted through both filters through a lens having an optical transmission characteristic of a transfer device to a semiconductor device and converting the light into electrical information. Mask design data verification device.