JP2010044287A - Method of manufacturing photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a photomask, which can prevent the occurrence of positional deviation error of a drawing pattern due to electron beam in a mask manufacturing step and the deterioration in yield due to the occurrence of the positional deviation of the pattern when a circuit pattern is transferred to a semiconductor wafer by using a photomask deflected by distortion of a glass substrate of the photomask. <P>SOLUTION: In a manufacturing step of the photomask, a crack assembly area 17 comprising a crack 16 distribution is formed in the mask 6 by irradiation with a femto-second pulse laser, the flatness of the mask 6 is improved by a tensile stress operated thereto and, thereby, the precision of drawing position of the circuit pattern 5 and the yield of the semiconductor wafer on which the circuit pattern is formed can be improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a manufacturing technique of a photomask (hereinafter simply referred to as a mask), and more particularly to a technique that is effective when applied to a mask that requires correction of distortion.

  Current integrated circuits are manufactured by transferring an integrated circuit pattern of a mask onto a wafer by an exposure apparatus. The mask is made by depositing a metal thin film on the top of the glass substrate to form a mask blank, coating a photoresist film, and drawing a desired circuit pattern on the metal film on the glass substrate using an electron beam. Have been made. The size of the circuit pattern of the mask is enlarged from twice to four times or five times the size of the product circuit. The exposure of the photoresist film applied to the semiconductor device being manufactured is performed by reducing and transferring the circuit pattern of the mask with a lens.

  Japanese Patent Laid-Open No. 9-306812 (Patent Document 1) adjusts the internal stress of an X-ray absorber pattern by heating the X-ray absorber with a heat source such as a laser, an electron beam, an ion beam, a charged particle, or an electromagnetic wave. An X-ray mask manufacturing method is disclosed.

  In JP-A-9-232216 (Patent Document 2), the in-plane stress of an absorber of an X-ray mask is measured, and the absorber is locally heated by a heat source of a light beam to adjust the stress of the absorber. An X-ray mask manufacturing method is disclosed.

  Japanese Patent Laid-Open No. 5-234858 (Patent Document 3) discloses an X for adjusting internal stress by partially removing and thinning the back side of a region where an X-ray absorber of a membrane exists or does not exist. A method for manufacturing a line exposure mask is disclosed.

Japanese Patent Laid-Open No. 2002-15981 (Patent Document 4) includes an internal stress between the base substrate and the reflective multilayer film so as to correct the mask distortion caused by the internal stress of the reflective multilayer film and the absorber film. A method of manufacturing a mask for semiconductor process is disclosed in which internal stress is adjusted by forming a stress adjusting film.
Japanese Patent Laid-Open No. 9-306812 JP-A-9-232216 JP-A-5-234858 JP 2002-15981 A

  In the conventional mask manufacturing process, the mask may be bent due to internal stress of the thin film pattern or distortion of the substrate material. If the circuit pattern is transferred to the wafer while the mask is bent, there is a problem in overlay due to the misalignment of the pattern. As a result, the characteristics of the integrated circuit are seriously affected, leading to a decrease in yield. In addition, when the mask blanks are bent during the electron beam drawing at the stage of manufacturing the mask, a positional deviation error of the drawing pattern occurs.

  According to Patent Document 1 and Patent Document 2, there is a possibility that distortion during film formation can be reduced by annealing (annealing) of the absorber. However, since there is a difference in the coefficient of thermal expansion between the substrate material and the absorber, distortion due to the difference in the coefficient of thermal expansion always remains even if the substrate and the absorber are in a thermal equilibrium state. Annealing has the advantage that it can change from a high energy state of electrons to a low energy state by slowly cooling from a heated state. However, in the local annealing in Patent Document 2, there is a possibility of rapid cooling, so that an unstable high energy state remains.

  Patent Document 3 is a method of selectively removing the back surface of the substrate, but damage to the absorber is unavoidable due to complicated processing accompanying the removal of the substrate.

  In Patent Document 4, a film that cancels the distortion of the entire mask is laminated, but rough stress control is possible under film forming conditions, but fine control is impossible.

  An object of the present invention is to provide a technique capable of improving distortion of mask blanks or masks, making circuit pattern drawing position accuracy more accurate, and improving yield.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

A method of manufacturing a photomask according to an embodiment of the present invention includes:
(A) preparing a mask blank in which a metal film is deposited on one side of a glass substrate, and forming a photoresist film on the metal film;
(B) irradiating the photoresist film with an electron beam, exposing and developing the photoresist film, thereby forming a photoresist pattern;
(C) processing the metal film using the photoresist pattern as a mask to form a circuit pattern to form a mask;
A photomask manufacturing method including:
Before the step (a) or after the step (c), a computer-controlled femtosecond pulse laser is incident on the imaging optical system by an illumination optical system and a reflection mirror, and the femtosecond pulse laser is made into the glass. By condensing light inside the substrate to generate cracks and irradiating with laser until a change in the deflection of the mask blanks or the mask reaches a predetermined state, a region composed of the set of cracks is formed inside the mask blanks or the mask. The distortion of the mask blanks or the mask is controlled by being distributed inside.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  In the photomask manufacturing process, cracks are formed and distributed in the mask blanks or in the mask using a femtosecond pulse laser to improve the flatness of the mask blanks or masks, thereby improving the drawing position accuracy and yield of circuit patterns. Can be improved.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say. In addition, when referring to the constituent elements in the embodiments, etc., “consisting of A” and “consisting of A” do not exclude other elements unless specifically stated that only the elements are included. Needless to say.

  Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  In addition, when referring to materials, etc., unless specified otherwise, or in principle or not in principle, the specified material is the main material, and includes secondary elements, additives It does not exclude additional elements. For example, unless otherwise specified, the silicon member includes not only pure silicon but also an additive impurity, a binary or ternary alloy (for example, SiGe) having silicon as a main element.

  Also, components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof is omitted.

  In the drawings used in the following embodiments, even a plan view may be partially hatched to make the drawings easy to see.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present embodiment is applied to a mask manufacturing method and will be described with reference to FIGS. As an example of the mask substrate size, a generally popular 6 inch (152.4 mm square) size is assumed.

  First, as shown in FIG. 1, a metal thin film 2 containing chromium or molybdenum silicide was deposited by sputtering on one side of a glass substrate 1 containing silicon oxide having a thickness of 6.25 to 6.35 mm to be a mask substrate. Mask blanks 3 are prepared. Then, a positive type photoresist film 4 is applied on the metal thin film 2.

  Next, as shown in FIG. 2, a desired circuit pattern is drawn on the photoresist film 4 using an electron beam. A circuit pattern 5 made of the metal thin film 2 is formed by dry etching the metal thin film 2 using the photoresist film 4 which remains undissolved by development as a mask.

  Next, as shown in FIG. 3, the photoresist film 4 is removed to form a mask 6. At this time, the mask 6 may be bent due to internal stress of the metal thin film 2 or distortion of the glass substrate 1. If the glass substrate 1 is distorted, when the circuit pattern 5 is drawn on the photoresist film 4 on the mask blanks 3 by an electron beam, an error in the drawing pattern misalignment occurs. Further, when the circuit pattern 5 is transferred to the semiconductor wafer, the pattern is misaligned, leading to a decrease in yield.

  In this embodiment, the positive type photoresist film 4 is used when forming the circuit pattern 5 in order to reduce the area where the electron beam is irradiated to the photoresist film 4. However, in some cases, the working efficiency is taken into consideration. A negative photoresist film may be used.

  Next, the configuration of the mask planarization system 15 is shown in FIG. This system includes a femtosecond pulse laser light source 7, an illumination optical system 8, a reflection mirror 9, a reduction projection optical system 10, a CCD camera (observation optical system) 11, a mask stage (XZY stage) 12, a mask 6, It comprises a stage controller 13 and a computer 14 that performs overall control thereof.

  In the present embodiment, it is assumed that the femtosecond pulse laser has a wavelength of 775 nm, a pulse width of 160 fs, energy of 0.005 mJ to 0.03 mJ, an optical system having a lens focal length of 150 mm and a condensing lens diameter of 20 mm. The irradiation energy is adjusted based on the basic energy according to the required bending moment.

  Next, the operation of the mask planarization system of this embodiment will be described. First, a femtosecond pulse laser controlled by the computer 14 passes through the illumination optical system 8 and enters the reduction projection optical system 10 by the reflection mirror 9. Next, the laser light from the reduction projection optical system 10 is condensed at a required position inside the mask 6. The focal position of the laser beam inside the mask 5 is adjusted by fine movement of the mask stage 12 controlled by the computer 14. A stress change occurs in the region where the laser beam is focused. This change in stress causes a change in the deflection of the mask 6. Laser irradiation is performed by moving the mask stage 12 in-plane until the change in the deflection of the mask 6 reaches a required state.

  Here, the correction process by the mask flattening system 15 for flattening the mask 6 when it is convex in the pattern side will be described with reference to the cross-sectional views of the mask 6 in FIGS. .

  First, as shown in FIG. 5, the mask 6 is placed on the mask stage 12 with the pattern surface of the mask 6 convex in the pattern side surface facing downward.

Next, as shown in FIG. 6, when the focal position of laser irradiation is determined inside the glass substrate 1 near the pattern side surface of the glass substrate 1, the laser is irradiated at a constant pitch in the thickness direction of the glass substrate 1. . When a laser having a power density of about 10 ⁷ W / mm ² or more is irradiated into the glass substrate 1, cracks 16 are generated near the laser irradiation point due to multiphoton absorption. The CCD camera 11 allows in-situ observation of cracks and confirmation of formation status.

  The crack 16 generated at this time is a crack that enters the thickness direction of the glass substrate 1, and its vertical length is about 0.05 mm. When the crack collecting region 17 composed of the distribution of the cracks 16 is formed in a required shape, a tensile stress distribution is formed. Thereby, the shape of the mask 6 that is convex on the pattern side becomes flat, and the mask 6 of the present embodiment is completed.

  In this step, the tensile stress distribution is formed by adjusting the size and distribution of the aggregate region 17 of the cracks 16 with laser light in the mask 6, so that the mask failed due to distortion of the glass substrate 1 or stress control of the thin film. 6 distortion can be corrected. As a result, the overlay accuracy and yield of the integrated circuit pattern can be improved.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  In the embodiment, the mask distorted convexly on the pattern surface side is corrected to be flat. On the other hand, when the mask is distorted convexly on the glass surface side, a crack distribution region is formed on the glass surface side in the glass substrate to correct the distortion.

  Further, the present invention can be used for a transmission type mask as in the above embodiment, but may be used for a reflection type mask blank or a mask such as an EUV (Extreme Ultra Violet) mask. Furthermore, although the distortion of the mask may be corrected as in the above embodiment, the distortion may be corrected in the state of the mask blank or the glass substrate before being processed into the mask. Furthermore, as an implementation method, the flatness correcting device of the present invention can be incorporated into an exposure apparatus.

  The photomask manufacturing method of the present invention is widely used in the manufacturing process of a photomask having distortion.

It is principal part sectional drawing explaining the manufacturing method of the photomask which is one embodiment of this invention. FIG. 2 is a fragmentary cross-sectional view of the photomask during the manufacturing step following that of FIG. 1; FIG. 3 is a fragmentary cross-sectional view of the photomask during the manufacturing step following that of FIG. 2; It is a block diagram of the mask planarization system of the photomask which is one embodiment of this invention. It is principal part sectional drawing in the manufacturing process of the photomask which is one embodiment of this invention. FIG. 6 is a fragmentary cross-sectional view of the photomask during the manufacturing step following that of FIG. 5;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Metal thin film 3 Mask blank 4 Photoresist film 5 Circuit pattern 6 Mask 7 Femtosecond pulse laser light source 8 Illumination optical system 9 Reflection mirror 10 Reduction projection optical system 11 CCD camera (observation optical system)
12 Mask stage (XZY stage)
13 Stage Controller 14 Computer 15 Mask Planarization System 16 Crack 17 Crack Aggregation Area (Structural Alteration Area)

Claims (1)

(A) preparing a mask blank in which a metal film is deposited on one side of a glass substrate, and forming a photoresist film on the metal film;
(B) irradiating the photoresist film with an electron beam, exposing and developing the photoresist film, thereby forming a photoresist pattern;
(C) processing the metal film using the photoresist pattern as a mask to form a circuit pattern to form a mask;
A photomask manufacturing method including:
Before the step (a) or after the step (c), a computer-controlled femtosecond pulse laser is incident on the imaging optical system by an illumination optical system and a reflection mirror, and the femtosecond pulse laser is made into the glass. By condensing light inside the substrate to generate cracks and irradiating with laser until a change in the deflection of the mask blanks or the mask reaches a predetermined state, a region composed of the set of cracks is formed inside the mask blanks or the mask. A photomask manufacturing method characterized by controlling distortion of the mask blanks or the mask by being distributed inside.

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