TW578033B - Design of attenuated phase mask - Google Patents

Abstract

The present invention is about the design of attenuated phase mask. First, to make sure the exposing part and use the phase shift layer design the pattern. Then, the chrome layer is used to protect the part that avoids the exposing light.

Description

V. Description of the invention (1) The technical field to which the invention belongs ... The process is particularly related to a ternary repair. The present invention is related to a type of decorative phase shift photomask. Prior technology: In the semiconductor industry, optical Resistive stepper or scanner, feel the case. The procedure is to first use the pattern on the developer on the part of the semiconductor that uses the exposure tool to expose the layer on the mask. Then use the etching or ion implantation process of this figure to use Mask (BIM) used in the traditional lithography process to form a pattern with cloth on the photomask. In the aforementioned positive region, the effect of the intended transfer phenomenon is limited at a certain wavelength and high resolution. When the size and the width of the wire are increasingly reduced, the technology of phase PSM is developed. Phase shift photomasks are produced using different phase schemes using lithographic exposure tools such as light exposure to define the required pattern. After coating a photoresist layer on the substrate, the pattern is projected onto the photoresist layer and the light is then applied. The photoresist layer is developed to make the photoresist layer appear as a mask. The photoresist layer is a mask, and the subsequent processes are performed. Most of the photomasks are binary photomasks (Binary light-transmitting areas and opaque areas of the binary light-resistance use of opaque photoresist patterns on the photomask. However, due to the optical diffraction conditions, binary The most required accumulation degree that can be achieved by photomasks is getting higher and higher. At the element scale, the “binary photomasks” gradually fail to meet the exposure fine shift mask (Phase-Shift Mask). 2. Description of the invention (2) The phenomenon “change the diffraction intensity distribution on the photoresist through appropriate design and configuration” to improve the accuracy of exposure. Because the phase shift configuration required by different patterns is not the same, a variety of different developments have been developed. Phase shift reticle, such as binary modified phase shift reticle (Attenuated Phase Mask) and alternating phase shift reticle (Alternating PSM), in which the alternating phase shift reticle is particularly suitable for the exposure and development of a series of photoresistors. A half-decay phase shift mask is a phase shift layer added to the glass plate on which the mask is made, so that the incident light can produce positive and negative interference, and the exposure machine is projected on the wafer. With a preferred pattern of image resolution. Which

The medium phase shift layer usually allows a certain proportion of incident light to pass through and project onto the wafer. The alternating phase shift photomask inverts the transmitted light of adjacent transparent areas.

The light intensity of the parent area is cancelled out to improve the exposure resolution of the photoresist line. The first figure shows a photomask configuration that transfers metal interconnect patterns with an alternating phase shift photomask. The oblique line portion 10 is an opaque area on the photomask, including a central linear interconnecting pattern area, and a surrounding square protective area. The blank portions 20 and 30 are light-transmitting areas, and the transparent light can be changed to make the transmitted light of the areas 20 and 30 have a phase difference of 180 degrees from each other. With this phase difference arrangement, the irradiance of the diffracted light at the edges of the photoresistive lines will cancel each other, which greatly increases the resolution between the two photoresistive lines. The first graph A to the first D graph show the exposure and development using the phase ^ light ^ shown in the first graph. Figure A is a cross-sectional view of a photomask. Generally, a transparent substrate 5 is used as the substrate of the photomask, and a chromium (Cr) film is plated thereon.

578033 V. Description of the invention (3) Formula 'makes the transmitted light rays of the region 20 and the region 30 have a phase difference of ig0 degrees from each other. When the wafer 40 in the second d is exposed in the direction shown by the arrow in the second A, the distribution of the light receiving amplitude on the wafer will be as shown in the second B. Due to the optical diffraction phenomenon, Function, the diffraction amplitude of light at the edge of the corresponding area of the opaque area 10 of the chromium film is not 0. However, under the design configuration k of the phase shift mask, the light waves with opposite amplitudes can cancel each other, and form as The intensity distribution in the second C diagram is developed on the wafer 40 shown in the second D diagram to form a pattern of the photoresist 50 with better resolution. Refer to the second figure for the layout of a complex MOS transistor connected to peripheral components. There are two polycrystalline silicon layers 301 and 302 on the active area 300. As this complex transistor And the metal line 3 03 is used to connect the gates of the MOS transistors. The line width of the metal line 3 03b in the active area 300 is about 80 nm, and in the active area 3 The line width of the metal wire 303a outside of 〇 can be about 100 nm. When the metal line 3 03 of the above layout pattern is exposed, it is usually performed in two ways. The metal line 303b in the active area 300 is exposed using an alternating phase shift mask first, and then the conventional binary light is used. The mask (BIM) covers the active area 300 that has completed the exposure, and at the same time, exposes the metal line 300 & out of the active area 300. However, the above-mentioned way, the metal line 303a does not get a good _ Resolution. The other method is to use an alternating phase shift mask to expose the metal lines 303b in the active area 300, and the exposure of the metal lines 303a outside the active area 300 is using a ternary modified phase shift light. The hood carries it out. Although the above-mentioned method "metal wire 303a" can obtain better resolution,

Page 6 578033 V. Description of the invention (4) The phase shift layer of the phase shift mask can still allow a certain proportion of incident light to pass through during the exposure process. Therefore, although the attenuation phase mask will expose the active area during the exposure process It is covered by 300 and is not exposed, but a certain proportion of incident light passes through, which affects the critical dimension exposure resolution in the active area of 3000. Summary of the Invention: In the background of the invention of the invention, the traditional layout pattern for the electrical connection of the complex transistor and the peripheral components is to use an alternating phase shift mask to first expose the active area where the complex transistor is located, and then use it. Two: First modify the phase shift mask to expose the metal wire outside the active area for two ms! The methods all have their shortcomings. The traditional binary reticle is used. However, exposure with the F :: ^^ line cannot obtain a good resolution. Shifting photomask 'although a better metal wire solution can be obtained. Due to the phase-shifting layer of the half-decay phase shifting photomask, the incident light passes through, so it is exposed during the exposure process ^. The critical dimension (eritieal) in the motion analysis reveals that St. One needs to use two different photomasks to perform pattern transfer. The alternating phase shift photomask is still used for one of the active new captures; I ^, then In a second step, a new 4 modified phase shirt mask is used for exposure. & Mask design Page 7 V. Description of the invention (5) The design method is to first determine the desired pattern for the desired layer design, and then not :: 二 = 部 ”with a phase chromium (Cr) layer to Do not let light :: Two-part ternary modified phase shift mask 丄 The present invention is different from the traditional ^ ^ early acupoint difference is that the value silk evening-modified phase shift mask One of the 70 ’s outstanding pattern parts are made of a translucent phase shift layer, that is, in the process of 笫 -increasing g ^ ^ ^ ^-phase development: f: protective layer on the active area in the sequence Invented in the pattern design department ☆, there is still an opaque plating: layer, so there will be better protection ability for the parts that are not intended to be exposed, such as the above areas. Embodiments: Without limiting the spirit of the present invention Under the scope of application, the following is an example to introduce the implementation of the present invention. Those skilled in the art, after understanding the spirit of the present invention, can apply the method of the present invention to various different mask products. Avoid affecting critical dimension resolution in some areas.

With the method of the present invention, during the circuit layout process of traditionally performing pattern transfer with two different photomasks, it is possible to avoid 'if a phase shift photomask is used for the exposure during the second exposure process. The photomask uses a phase shift layer to design the required exposure pattern, because the phase shift layer can still allow a certain proportion of incident light to pass through during the exposure process, causing a certain proportion of the area to be protected during the exposure process. The incident light passes through and affects the critical dimension exposure resolution in this area. Therefore, the design method of the photomask of the present invention is to first determine the part to be exposed, and in this part, use the phase shift layer to design the required pattern, and then

Page 8 578033 V. Description of the invention (6) The part that is not to be exposed, that is, the part that needs to be protected during the exposure process, is still protected by a chromium (Cr) layer to prevent light from passing through. The application of the present invention is not limited to the preferred embodiments described below. Referring again to the third figure, it shows a layout pattern of a plurality of M0S transistors when they are interconnected with peripheral components. There are two polycrystalline silicon layers 301 in an active region 300 formed on a substrate. And 302, the two polycrystalline silicon layers 301 and 302 are used as the gate layers of the complex transistor, and the metal line 303 is used for the electrical connection of the MOS transistor gates, among which the metal lines in the active area 300 The line width of 303b is about 80 nm, and the line width of the metal line 303a outside the active area 300 may be about 100 nm. During the exposure process of the above layout pattern, two exposure procedures are generally used. In the first exposure procedure, the metal wire 3 3b within the active area 300 is exposed first. There is a higher critical dimension resolution, so this is usually done using an alternating phase shift mask. Then in the second exposure process, the mask used must be able to completely protect the active area from being affected by the second exposure process, destroying the critical size resolution in the active area, and for the active area outside 300 The metal wire 303a still needs to maintain a high degree of exposure resolution. Therefore, the present invention adopts a new design of a ternary modified phase shift mask pattern with opaque areas. The photomask is generally based on a transparent flat plate, and a circuit is formed on the flat plate to define a desired pattern. The transparent flat plate is generally composed of quartz. In the phase shift mask, the difference in thickness forms a phase shift layer to change the phase of the incident light, so that the bit of the incident light is shifted due to the delay. Phase shift is usually achieved by using light-transmitting layers of different thicknesses or refractive indices. Ternary modified phase shift mask

Page 9 578033 V. Description of the invention (7) Combine adjacent phase-shifted light and non-phase-shifted light to form a destructive interference in the adjacent area of the light-transmitting layer and the phase-shifting layer to form a wire pattern and improve the analysis. Degrees and Depth of Focus ·. When it is desired to form the above-mentioned ternary modified phase-shifting photomask with opaque areas, the method of the present invention can be used to form the original photomask obtained from a photomask supplier. First, referring to the fourth figure, there is shown a cross-sectional view of the structure of the original ternary modified phase shift mask 56 provided from the mask supplier's premises. Its main groups are a transparent plate 58, a phase shift layer 60, an opaque layer 62, and a photoresist layer 64. The material of the transparent plate 58 is mainly a highly transparent material such as glass or quartz, and its thickness is about 250 m i 1. The phase shift layer 60 is mainly used to change the phase angle of the light projected by the exposure machine during the lithography process, so that the pattern transferred to the wafer by the phase shift mask 56 can be more than the traditional mask accurate. In general, the material of the phase shift layer 60 may be a compound of molybdenum (M0) such as

MoSiON has a thickness of about 1350A. The opaque layer 62 is used to form an opaque area to protect the exposed area from light during the exposure process. The material is generally made of chromium (Cr). The photoresist layer 64 is an unexposed photoresist material for a wafer manufacturer to define a desired pattern. Please refer to the fifth figure and merge the third figure to refer to the top view shape of the photomask of the present invention formed by using the original ternary modification phase shift photomask 56 of the fourth image, in which the photomask pattern is formed on Board 58 above. The base transparent plate 58 has a plurality of phase shift layers 60, which are used to transmit incident light, and retard the phase of the incident light transmitted through the phase shift layer 60, generally by 180 degrees, so that the transmitted light and the The phase of the incident light is reversed to form

ι ^ η Page 10 578033 V. Description of the invention (8) The pattern of the metal wire 303a outside the active area 300. In addition, a transparent layer 58 is provided on the base transparent plate 58 to protect the active area 300 of the third image during exposure. Since the transparent layer of this layer is made of chromium, It does not allow light to pass through, and can effectively protect the active area 300 during the exposure process from being affected by the exposure light source. This way of protecting with chromium 'is different from the traditional method of shielding the active area 300 with only a phase shift layer 60, which is obviously different from the traditional method. A certain proportion of incident light will still pass through this phase shift layer 60. The critical dimension exposure resolution in the active area is affected.

Refer to the sixth figure, which is a cross-sectional view viewed from the line AA 'in the fifth figure. Obviously in this area, it is used to protect the active area 300 from being exposed to the light source during the exposure process. Therefore, the transparent substrate 58 The phase shift layer 60 has a opaque layer 62 made of chrome, which blocks light from passing through when it is exposed. Refer to the seventh figure for a cross-sectional view seen from the fifth figure BB, line, The obvious mask pattern outside 300 in the active area is completely composed of the phase shift layer 60, that is, in the mask pattern in this area, the phase of the incident light transmitted through the phase shift layer 60 (phase The retardation is generally 180 °, which makes the phase of the transmitted light and the incident light reverse, so that the image pattern projected on the wafer by the exposure machine has a better resolution. According to the above, the design method of the photomask of the present invention is to first determine the portion to be exposed. In this part, the phase shift layer is used to design the required pattern, and the portion that is expected to be exposed remains the key chromium. The (Cr) layer prevents light from passing through. In other words, the phase shift mask provided by the present invention is made.

578033 V. Description of the invention (9) In the second and third steps, in the photo-mask process, the protective layer used to cover the active area is opaque. ^ 9 4 To be continued. The exposed part, like the active area mentioned above, will have better protection capabilities. The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of patent application of the present invention. Any other equivalent changes or modifications made without departing from the spirit disclosed by the present invention shall be included in the following Within the scope of patent application.

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Brief description of the drawing: Alternating phase shift mask configuration of line graphics. The first figure is a metal interconnected TψΊ. Figure ^ is a cross-sectional view of the phase shift mask shown in the first circle; Figure A: ^ When exposure is performed with the phase shift mask shown in Figure 7A, the parent light amplitude distribution on the wafer; Figure C is the received light intensity on the phase shift mask shown in Figure 2A. Distribution diagram Γ The second diagram D is the photoresist pattern of the wafer after exposure with the phase shift mask shown in the second diagram A; The third diagram is a layout diagram of interconnections between a plurality of M0S transistors and peripheral components The fourth figure is a structural cross-sectional view of the original ternary modified phase-shifting photomask used in the present invention, and the fifth figure is a top view of the photomask of the present invention formed by using the original ternary modified phase-shifting photomask; FIG. 7 is a cross-sectional view of a photomask formed according to an embodiment of the present invention viewed from line AA; and FIG. 7 is a cross-sectional view of a photomask formed according to an embodiment of the present invention viewed from line AA.

Page 13 578033 Brief description of the drawing Drawing reference comparison: 5 transparent substrate 10 opaque area 20, 30 area 40 wafer 50 photoresist 56 original ternary modified phase shift mask 58 transparent plate 60 phase shift layer 62 Opaque layer 64 Photoresistive layer 30 0 Active area 301 and 302 Polycrystalline silicon layer 303 Metal line 303b Metal line 3 0 3 a Metal line

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Claims (1)

578033 6. Scope of patent application L • A method for making a phase shift mask, wherein the mask is composed of a transparent plate, a phase shift layer and an opaque layer, and the method at least includes: manufacturing a portion to be transmitted through the phase shift layer ; And keep the opaque layer on the part that does not want to transmit light. 22 The method according to item 丨 of the scope of patent application, wherein the above-mentioned phase shift mask is a binary modified phase shift mask (Attenuated Phase-Shift Mask): 3. The method according to item 丨 of the scope of patent application, wherein The material of the opaque layer is a network. 4. A method for manufacturing a phase shift mask, wherein the mask is composed of a transparent plate, a phase shift layer, and an opaque layer, the method includes at least: determining a predetermined exposure area after exposure; determining a light blocking area of the mask; A phase shift layer is used to form the predetermined exposed area; and an opaque layer is retained on the light blocking area. 52. The method according to item 4 of the scope of patent application, wherein the aforementioned phase shift mask is an Attenuated Phase-Shift Mask. ] The method according to item 4 of the scope of patent application, wherein the material of the opaque layer mentioned above is chromium. Page 15