TWI275129B - Method to improve the line-width uniformity and figure fidelity of OPC mask by adding an assistant gap on the mask - Google Patents

Abstract

The present invention provides a method to improve the fidelity of OPC (optical proximity correction) mask by adding an assistant gap on the mask pattern for manufacturing the OPC mask with electron beam, and especially, the fidelity of serif pattern and the line width for OPC is increased. The added assistant gaps will not be developed on the mask; therefore, the original design figure will not be changed.

Description

1275129 V. INSTRUCTION DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to a method for defining a body line pattern on a reticle by an electron beam plotter (E-Beam Writer), in particular, to avoid light, correction (〇ptlcal Pr 〇ximity c〇rrecti〇n,〇pc) The error that the line layout (Layout) is transferred to the mask. ^ Background of the invention:

With the continuous development of the tunneling semiconductor industry, the wafers produced are shrinking] and the various components contained on the wafer are increasing, so that the wafer must continuously increase the density of the package. At the same time, it is necessary to reduce the size and size of each type, and also complete the challenge of high integration of integrated circuits. And one: the second 'modern integrated circuit is often connected internally with millions of yuan to perform certain functions. Therefore, in order to satisfy the requirements of increasing the degree of integration and reducing the size of components, and effectively defining a semiconductor integrated circuit component, a small and complicated circuit pattern is required. Therefore, in the design of the photomask, the trend toward miniaturization has been progressed. As the size of semiconductor components shrinks, the line width of the mask is also reduced. Therefore, from the above, in the drawing of the reticle pattern, the electron beam drawing system has a high resolution, and is widely used in large-scale integrated circuits (LSI) or ultra-large integrated circuits (VLSI). In the process, the pattern of the high-concentration semiconductor element can be defined on the wafer or the mask. thousand

Page 5 1275129 V. Invention Description (2) In the past, it could be used in traditional processes to define such as Word Line, Bit Line, and Gate structure. Wait for part of the mask of the polysilicon pattern. The exposure process is sequentially performed on a plurality of quadrangular regions surrounding the area, and an area having a line segment pattern is defined on the reticle. In addition, when the wafer is lithographically processed using the manufactured photomask, end shortening is often caused at both ends of the line segment pattern. That is, in the lithography process of defining the line pattern, the retracted effect is caused by the transferred line segment due to the optical action. Therefore, the length of the line segment is reduced, causing a change in the conductive characteristics. In particular, in the extremely high-accuracy and extremely precise wafers, the change in the size of the pattern defined by the film is greatly reduced, and the resulting element is prone to failure and the like. In order to overcome the above retraction phenomenon, the optical proximity correction method (Optical Proximity Correction, 0PC) has been introduced in the conventional technology to perform a lithography process on a line segment pattern. Please refer to the first A picture. With this method, the two ends of the central portion of the line pattern are often made to have a pattern (labeled as an unexposed portion) as indicated by the mark 1 in Fig. A. Zooming into the first B picture, the resulting prominent pattern (J0g) 12 and the inner serif pattern (Inner Serif) 13 ' and the most common vector electron beam exposure system (Vect〇r-Scan-E- A simple schematic diagram of Beam Writer) is shown in Figure c, where each mark includes quartz (Quartz) 101, chrome (Cr) l〇2 and photoresist (Photoresist) 103, and the first square aperture 1〇4, Two square aperture

Page 6 1275129 V. Invention Description (3) — 1,: It is necessary to cut the circuit diagram into many rectangles, but it is most common to cut in the horizontal direction, so it will cause a fine pattern (F^^e) with a width less than 100. Millimeter (nan〇_meter), E-Beam projection is not easy to control. Each of the graphs has a positive photoresist as an example. The electron beam exposure procedure for defining the cover of the integrated circuit pattern is too large, so that the exposure-chrome is on the mask. Membrane residue and optical proximity

Proximity Correction, OPC) True 'causes the line width of the pattern to have uneven illumination and cannot be accurately defined on the reticle. It is necessary to adjust the size of each exposure projection to achieve the same unit to cut the fine pattern. The uniformity of the absolute dimensions of the electrons also causes serious problems of excessive photo-resistance. The results have a significant impact on the yield of the sputum, and the shape _ invention summary: ^ Under the above-mentioned first A-picture, the mask will cause the development of the photoresist that should be produced in the slit film to produce excessive exposure Or insufficient, so that the correction method (0 ptica 1 serif (Serif) pattern pattern loss of absolute dimensions, can not be effectively exposed, and because of the parameters in the logarithmic area, such as exposure time and electron beam area exposure dose. However, it is difficult to focus on the traditional method and it is difficult to maintain the exposure under the exposure or to expose the subsequent malfunction. The cost of the material and the waste of manpower. Yi Yi La Mi Yue is related to the electron beam plotter (E -Beam Writer) The method of setting the line pattern on the reticle, especially to avoid optics

Page 7 1275129

The Correction (Optical Proximity Correction, OPC) line layout (Layout) error transferred to the reticle. Another object of the present invention is to reduce the occurrence of poor linearity uniformity and distortion of the optical proximity correction serif pattern (Inner Serif) during reticle fabrication. ~ Other objects of the present invention are to eliminate many of the line unevenness or burrs during the fabrication of the reticle pattern, and to avoid the above-mentioned errors caused by optical proximity-correction reticle fabrication. The present invention increases the accuracy of the electron beam exposure by adding an auxiliary slit to the reticle pattern to increase the accuracy of the optical proximity correction reticle.

First, on the circuit layout of the optical proximity correction mask, an auxiliary slit is added to the small protrusion (Jog) or serif (Serif) of the optical proximity correction of the fine pattern (Smal 1 Figure). To avoid the small figure (Small FigUre) caused by the traditional horizontal split. In the continuous diagrams of the third A^ to the third D, the serif portion (Serif) portion of the mark 6〇 is formed, and the protrusion (J〇g) portion of the third C mark 61 is also formed (this) For example, positive ~ photoresist is taken as an example, and white area is exposed area). The third D picture is a larger part of the third c picture. In addition, some straight segments have many vertical segments.

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I 1275129 V. INSTRUCTIONS (5) The accumulation of micro-patterns (Smal 1 Figure) also causes burrs here (marker 1 4 of Figure A). Therefore, an auxiliary slit can be added in the vicinity of the present invention. Avoid it (mark 30 of the second figure). Finally, the exposure process is performed in sequence to define the integrated circuit layout on the optical proximity correction mask. DETAILED DESCRIPTION OF THE INVENTION: "The present invention is an electron beam plotter (E-Beam Writer) system _ 4 予 予 近 近 近 近 〇 〇 〇 〇 〇 ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' A method of adding an auxiliary slit (A ssistant G ap) pattern to improve the accuracy of the optical proximity correction integrated circuit layout of the desired semiconductor light. ' The mark 2〇 and the mark 3〇 shown in the second figure, the concept of the present invention, the shape of the auxiliary slit pattern to avoid the exposure of the area in the horizontal direction * ^ fk produces fine patterns in the exposed area . Thus, after the graphics are cut, all the rectangular patterns of the ^^^ field are larger than a predetermined width, and the predetermined width is to be 疋', and the sub-beam plotter maintains the required precision and the minimum resolution of the resolution is allowed. 'When the reticle is subsequently produced by the electron beam plotter, the line width of the reticle and the line portion of the reticle are corrected to produce an accurate absolute dimension. Therefore, the specific method of the present invention is as follows.

1275129 V. INSTRUCTION DESCRIPTION (β) '------- The preferred embodiment of the fizU Benming includes the following steps: such as the third D icon = 4 g 糸 - magnified by the third c picture) As shown in the embodiment of the present invention, the optical opening proximity correction pattern of the slot Sr auxiliary slit in the integrated circuit layout diagram is generally less than 2 〇 nm, so as not to develop the second purpose. In addition, the minimum length of the auxiliary slit is limited by the edge pattern capability of the electron beam plotter and the mask manufacturing technique, and usually needs to be greater than 1 〇〇 nm. And, as in the third B diagram and the third C diagram mark 6〇, on the optically closely corrected serif (Serif), the first auxiliary slit is drawn (Assistant

- The part of the serif is formed by a single pattern. As a result, the sides of all the patterns are larger than 1 〇〇 nm, and the E-Bean Writer can stably expose these patterns without the problem of insufficient exposure or excessive exposure. The conventional electron beam machine graphics cuts the shortcomings of the small figure (Small FigUre), and greatly improves the line width uniformity of the optical proximity reticle (Uniforjjjify) and the accuracy of its optical proximity correction pattern (Fidelity). In a preferred embodiment of the invention, an auxiliary slit is first added to the line segment pattern in the body circuit layout, and is described herein only in the context of defining an optical proximity-correction line pattern. The integrated circuit layout diagram mentioned can be used to define and fabricate a reticle for use in subsequent semiconductor processes to perform related lithography to transfer the layout on the reticle to the desired On the wafer or workpiece. (ie, the line pattern is defined in the subsequent semiconductor process, a wafer pattern is defined on the semiconductor)

Page 10 1275129 V. Inventive Note (7) Wei # ί ί, according to the division of the plurality of rectangular areas in sequence, the reticle pattern layout of the line segment is optically close. "it, the slave mask defines the mask of the pattern program, including the substrate formed by the material: quartz, which is not made of the first chrome film. Μ上站ΪΪ, form a photoresist layer on the film, and use the electron beam mapping system - for example cut! Area, the exposure process is performed in sequence. In the general implementation, the electronic light is blocked by the electronic light, and after the development process, the beam and the exposed portion of the image are removed. The lithography process is then used to remove the chrome film covered by the V-resist layer, thus defining the desired line pattern on the light.季ΐ: ΐίί: In the case of the divided rectangles, the electron beam drawing system is used to delineate the pattern on the mask, so it can be performed using a larger than loo nm electron 2 size, and the edges of all the lines are fairly uniform. Dimensions. This can effectively improve the subsequent lithography process of the entire layout. If the above method is applied to a logic component product, the invention can be utilized.

The uniformity of the width dimension of the hood is better, and the variation of the line width dimension (CD)

Variation Range) is reduced to 20 nm or less, and the optical proximity correction (Optical Proximity Correction, 0PC) mask yield is improved / for the optical proximity effect correction method: according to the optical proximity effect

Page 11 1275129 V. Description of invention (8) Due to the phenomenon of occurrence, the method of optical Proximity Correction (OPC) in the current research and development is mainly based on the design change of the mask pattern, mainly with characteristic deviation ( Feature

Biasing) and Feature Assisting. New corrections commonly found in the literature, including transmission control masks (Transmission) 亦 There are also many companies that offer 0PC software, and the common 〇pc software has

OPRX (Trans Vector), Masktools (MicroUnity), Proxinia (Precism), 〇ptissimo, Maskrigger, etc. 0 After the various test patterns on the mask are obtained by the machine and lithography process to be corrected, the amount of the resist is obtained. Deviation of the resistivity profile, feedback this deviation to the [deformation of the mask pattern correction. Single layer patterns are easier to fix. The more difficult is the correction of the multi-layer and the topographic bottom pattern with a mask. According to experience, the internal and external auxiliary line method has different degrees of improvement in the latitude and depth of focus of any mask, and is the most widely used method in the characteristic deviation method, but the mask preparation is not easy.

After 0PC, the required capacity of computer data processing and the time required for electronic east-illumination to create a mask are increased by more than 0 times. " On the other hand, the electron beam proximity effect correction used in the present invention

1275129 5. Invention (9) (Electron Beam Proximity Effect Correction, EPC). In the process of electronic lithography, the scattering behavior caused by the collision of incident electrons and a resist with the substrate leads to a wider range of electron illumination, and the electrons outside the design criteria (De si gn Ru 1 e ) occur. The illuminating agent and the Fan 圜 result in deformation distortion of the resist profile. It is called the electron beam proximity effect (Electr〇n Beam proximi ty Ef f ect) because it is greatly affected by the density and size of the proximity resist. The main cause of the effect is caused by backscattered electrons and secondary electrons (Secondary Electron).

This effect is small when the electron beam voltage is higher (greater than 30kV) or lower (less than 2〇kV). Take the selection line as an example. Although the administration agent is the same, the central part has a higher dose and the outer side is lower. The date of the correction of the proximity effect is such that the central and outer portions have the same obtaining agent i. The above-mentioned electron beam proximity effect is very extensive, and the mathematical models used are very complicated. Generally, they can be summarized into the following three types: '1 · Monte Carlo Method: Monte Carlo is located in France Lee, the capital of Monaco, a small Mediterranean country, is a world-famous casino. This method assumes that after the electron irradiation enters the resist, the individual electron scattering is determined by the random number (Random Number), such as gambling, so it is named after Monte Carlo. The distance between the secondary scattering is assumed to be the Mean Free Path of electrons. This method mainly uses the Rutherford formula to calculate the cross section formed by the scattering angle: the Bethe formula calculates the energy loss.

1275129

The more the better, the better. The shortcoming is the data, the national FINLE company electronic Dongmo this method needs to calculate a large number of individual electrons (usually the pseudo-electron scattering is performed, the results are more accurate and the amount is very large, and the computer calculation time is very much. The pseudo-software PR0BEAM/3D adopts this method. 2 . Analytical Models: There are many types of analytical models. The stencil type used by SELID of Germany is described as an example. After electron irradiation enters the resist, the amount of electrons deposited in the unit volume of the resist is Energy Deposition Function (Energy Deposition ^

The analytical method (B〇itzm'a = Transport Equation) is obtained by the Analytical method. Therefore, after analyzing the model A, the Φ 丄丄 resisting agent enters the substrate, and the energy loss is very large. Is the value name. The electron is solved by the (^Nurnen cal) method. Other analytical models calculate the distribution of electron energy in the resist, usually by resist forward scattering, resist backscattering, / ΐ f. In general, the analysis model is less refined, but the calculation time is shorter. 3 · Approximate analysis function (Appr〇ximate Anal tic ^ Use the sum of several Gaussian functions and the overall distribution of your beam irradiation. In the present invention, two kinds of photoresist, the so-called positive Removal, while others generally, the main photoresist of the photoresist is that the photoresist that is illuminated by the light will not be divided into positive photoresist and the negative portion can be removed by the developer. The negative photoresist is removed.

Page 14 1275129 V. INSTRUCTIONS (11) The part that is illuminated by light will not be colored by the developer, and the area to be irradiated will be removed by the developer' while the rest is not light. The photoresist must be Carefully designed ν different lithography process requirements, ί to meet different light sources and properties: Syria S, it must be prepared for the following special 1 sensitivity (sensitivity) to stay a work i full, show light resistance The amount of the agent is two::: the energy received, - the shorter the time required for exposure, the more the output is J. The more two 'constraints': the measurement of the exposure of the photoresist (or 曰 solubility change ^ rate), after exposure and development, the positive rate of the residual thickness of the exposure Logarithmic plot, you can get the sensitivity of the curve 1 = the slope of the residual can get the slope of the positive or negative photoresist rp or rn), from _;, straight; line region, the molecular weight is +, the narrower the molecular weight distribution, the contrast Then, 'there are 3 different resolutions ^, which means that the smallest ruler f can be reached. Because it is affected by the external phase, it is not easy to quantify it. Generally, it is determined by the thickness and the large area of the photoresist. , the best is the minimum - in 4. Optical intensity (0pticai density): indicates that the light is received at every #m, generally, if the absorption value is less than 0.4/zm-l, then 彳3 _ 吸Image. Uniformity 5. Resistance to etching: Indicates that the photoresist is resistant to etchant or etched plasma. During the pattern transfer process, the photoresist cannot be changed by more than 10%. In order to improve the sensitivity, it is required to improve. The effect of photoresist on light, but this will be the same as the 15th page 1275129. 5. Description of invention (12) Causes its resistance to plasma I has a reduced ability to insect, so a balance must be achieved in design. 6 · Purity: Since the characteristics of semiconductor components are easily affected by trace impurities, the components that affect the characteristics of the components must be controlled above ppb. · Since the processability is closely related to the production cost, the design of the photoresist must be considered at the beginning of its workability. 8 Solvent solubility: 倶 Appropriate solvent solubility makes it easy to obtain a uniform and defect-free photoresist film. 9 · Thermal stability: 倶 Proper thermal stability, can tolerate the temperature of production, heat-stability. It is related to the transfer temperature of polymer glass. The polymer with low glass transition temperature is not conducive to baking, at least 2 0 〇 °C or more. 10. High adhesion: This property is related to etching, especially in wet etching. If the adhesion is not good, it may cause the solvent to infiltrate into the image, causing the pattern to fall off or affect the resolution. In the presence of small particle impurities or oil stains, it is necessary to improve the adhesion. In addition to the excellent adhesion of the polymer itself, it is also possible to add an adhesion promoter, such as Hexamethyldisilazane. Considering the design of photoresists, the design of photoresists must take into account the basic optical properties. The smaller the UV residual absorption after exposure, the better, ie, light. / The whitening effect (ph〇t〇b 1 each i ng) is as complete as possible. The g-1 i ne photoresist is dominated by a Bisazide Photoactive Compound (PAC) or a back bond. The benzophenone-containing thiophenone-containing compound is an intermediate matrix (baiiast group), and this type has a total of 16th page, 1275129. 5. The invention (13) The chemical structure of the backbone is good in light transmission of g-丨ine, but There will be significant residual absorption after the 1 ine exposure number. In addition, the isomerization reaction of the photoresist is blocked: 1. The insoluble and soluble resin (n〇nv〇lac resin), the azide compound, the nitrogen-rich compound, and the isomerization of the phenolic resin Insoluble, this can be applied to negative photoresists. 2. Due to the addition of a dissolution inhibitor such as DNQ, the phenolic resin soluble in the lye is insolubilized, but after the irradiation, the MQ is isomerized, and the carbene, ', Woff recombines to form a dilute ketone ( Ketene), hydrolyzed to form a rebel, and solubilized phenolic resin, which can be applied as a positive photoresist. 3. The phenolic ester of the main chain or side chain of the resist of the molecular photoresist, ph〇t〇-Fries translocation due to light, ortho or para-nonylphenol (acryl phenol), resulting in poor solubility. 4. A photo-resist which is insoluble in the ortho-nitro ester (nitr〇 benzyl ester), which forms a soluble nitrozinone (nitr〇 benzyketone) and an acid. , the decomposition reaction of the main chain of the resist, such as polypropyl enoate, or poly (e-lefin sulf〇n) copolymerized with olefin and sulphur oxide, which is decomposed by light and can be used as a positive photoresist. The exposure methods in lithography can be divided into three main categories, the following three exposure methods: / 1. Contact exposure · The pattern exposed by this method is closest to the mask

Page 17 1275129 V. Invention Description (14) When the pattern and size are lighter than the light, the mask and the lingering are no longer commercial. 2. The proximity of the mask is not the same as the resolution of the shift. The need for a more advanced process 3. The projection exposure has contact with the wafer or the pattern. The method of this method is 1 ··1, and the resolution is very good. The wafer is in contact with the wafer, and the surface of the mask will follow the exposure. The exposure, the upper particles, and the increase in the number of people who influence the subsequent transfer of the map. The quality of Bamu, therefore: basically the same principle as the contact exposure method, the contact of the oral sputum wafer, eliminating the lack of contact exposure method, which will cause the resolution is not good, thus making the image of the former poor. So it is not suitable for the current high density ^ the most basic difference between the two is that the reticle is not or close, but the hood pattern is transferred in such a way that the film is on the wall to the film. Adopted by the modern semiconductor industry. The present invention is described in detail with reference to the preferred embodiments of the invention, and is not intended to be

1275129_ BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a schematic diagram of a prior art; FIG. 1B is an enlarged schematic view of a conventional technique; FIG. 1C is a schematic diagram of a vector electron beam exposure system; The second A is a continuous schematic view of the present invention, the third B is a continuous schematic view of the present invention, and the third C is a continuous schematic view of the present invention; and the third D is a continuous schematic view of the present invention. Description of the figure: 1 0 pattern 11 non-exposed part 12 protruding pattern (Jog) 13 serif pattern (Serif) 1 4 raw edge 2 0 division pattern 3 0 division pattern 6 0 serif (S erif ) 61 protrusion (Jog) 6 4 auxiliary slit 101 quartz (Quartz) 10 2 chrome (. 1 〇 103 photoresist (Photoresist) 10 4 first square aperture 10 5 second square aperture

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Claims (1)

1275129 6. Patent application scope 1. A method for adding an auxiliary slit pattern to a reticle comprises at least: providing a plurality of line segment patterns of an integrated circuit layout diagram to form a plurality of rectangular regions; forming a first An auxiliary slit (Asistant Gap) is formed between the plurality of rectangular regions; a second auxiliary slit Us is tant Gap is formed between the plurality of rectangular regions; and an exposure program is sequentially performed to define the integrated circuit layout On the optical proximity correction mask. 2. The method of claim 1, wherein the line segment pattern is an optical proximity correction pattern. 3. The method of claim 1, wherein the line segment pattern is in a subsequent semiconductor process defining a wafer pattern on the semiconductor. The method of claim 1, wherein the width of the auxiliary slit is less than 20 nra 〇 5. The method of claim 1, wherein the length of the auxiliary slit is greater than 100 nm. To form a shaped area with a width greater than 1 〇 On m to facilitate electron beam projection. Page 20