JP2005327983A - Stencil mask, method for manufacturing same, and method for exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stencil mask having marks for distortion measurement which can prevent imprinting on the object to be exposed and can suppress the mask distortion due to stresses generated by the marks themselves, a method of manufacturing the stencil mask, and a method of exposure which accurately imprints the mask pattern on the object to be exposed in such a way as to cancel the mask distortion based on the measurement result of the mask distortion measurement marks. <P>SOLUTION: An electron beam is shielded at positions of the mask-distortion measurement masks 4, since the mask-distortion measurement marks 4 are provided by step differences instead of piercing holes. Therefore, the mask-distortion measurement marks 4 are not imprinted on the object to be exposed. Besides, the mask distortion can be suppressed due to stresses generated by forming the mask-distortion measurement marks 4 on the charged-particle-beam shielding film 3. In the method of exposure using the stencil mask stated above, the mask pattern is accurately imprinted on the object to be exposed in such a way as to cancel the mask distortion based on the measurement result of the mask-distortion measurement marks 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a stencil mask used for exposure using a charged particle beam such as an electron beam, a manufacturing method thereof, and an exposure method.

  2. Description of the Related Art In a low energy electron beam proximity projection lithography (LEEEP) technique using a 2 kV electron beam as a light source, a stencil mask having a mask pattern formed of through holes is used. As the stencil mask, a membrane (thin film) having a thickness of about 500 nm to 1000 nm is used so as to shield an electron beam while maintaining processing accuracy. A typical membrane material is Si.

  The LEEPL technology requires complementary division processing to prevent donut problems and damage during LS pattern cleaning in line-type layers, but for hole-type layers, optical resolution is high due to its high resolution and wide margin. May be replaced. In this case, it is indispensable to mix and match exposure with optical lithography, and a mask area of 2 to 3 cm square is required in accordance with optical lithography.

  In order to form a 2 to 3 cm square mask region with a single membrane, it is necessary to increase the internal stress of the membrane. When the internal stress of the membrane is increased, the mask strain increases due to the release of stress when forming a mask pattern including through holes in the membrane. Mask distortion is a positional deviation of a pattern in the plane of the mask.

  Therefore, a stencil mask provided with a grid-like reinforcing beam has been proposed (see Patent Document 1). In the above-mentioned Patent Document 1, a stencil mask is disclosed in which the size of one membrane is about 1 to 3 mm by partitioning with beams, and the arrangement of the beams in the four mask regions is shifted. By overlaying and exposing the four mask areas, a predetermined circuit pattern is transferred to the wafer.

  The advantage of the stencil mask described in Patent Document 1 is that the stress strain in each membrane region can be reduced. Further, there is disclosed a method of forming a mask distortion measurement mark for grasping mask distortion on a beam and correcting the mask distortion using the mask distortion measurement mark (see Patent Document 2).

  However, when the stencil mask described in Patent Document 1 is employed, when scanning four mask regions formed on the stencil mask at a time, the scanning range of the electron beam is at least twice that of the die in both the vertical and horizontal directions. Become. In the same-magnification proximity exposure technique disclosed in Patent Document 1, when the scanning range of an electron beam is increased, it becomes difficult to perform beam scanning with high accuracy while maintaining a parallel electron beam. It is also necessary to improve the overlay accuracy of the four mask areas.

Therefore, in recent years, a stencil mask having only one membrane without a beam (collective membrane type stencil mask) has attracted attention again. As described above, it is known that increasing one membrane size increases the mask distortion, so it is important how to grasp the mask distortion in a batch membrane stencil mask with the largest membrane size. Become.
JP 2003-59819 A JP 2004-55780 A

  However, since there is no beam in one membrane, the mask strain measurement mark cannot be placed on the beam, and therefore it is necessary to place the mask strain measurement mark in the membrane region. Therefore, when the mask distortion measurement mark is formed in the membrane area by a through hole in the same manner as the mask pattern, the mask distortion measurement mark is transferred to the wafer, and the execution area for placing the device pattern on the wafer is small. In addition, there is a problem that a new stress strain is generated in the through hole of the mask strain measurement mark itself.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to measure mask distortion that can prevent transfer to an object to be exposed and suppress stress distortion generated in the mark itself. An object of the present invention is to provide a stencil mask provided with a mark and a manufacturing method thereof.

  Another object of the present invention is to accurately transfer a mask pattern to an exposure object so as to cancel the mask distortion based on the measurement result of the mask distortion measurement mark, and the mask distortion measurement mark is transferred to the exposure object. It is an object of the present invention to provide an exposure method capable of preventing transfer to a film.

  In order to achieve the above object, the stencil mask of the present invention comprises a charged particle beam shielding film, a through-hole formed in the charged particle beam shielding film, a mask pattern transferred to an object to be exposed, and the charge And a mask strain measurement mark formed of a step formed by leaving a film thickness capable of shielding charged particle beams on the particle beam shielding film.

The stencil mask of the present invention includes a mask strain measurement mark having a step formed to leave a film thickness capable of shielding the charged particle beam, so that the charged particle beam is shielded at the mask strain measurement mark. Thus, the mask distortion measurement mark is not transferred to the object to be exposed.
Further, since the charged particle beam shielding film having a thickness capable of shielding the charged particle beam remains at the formation position of the mask strain measurement mark, the stress strain generated by the formation of the mask strain measurement mark is suppressed. .

  In order to achieve the above object, the method for manufacturing a stencil mask of the present invention is a mask comprising steps by etching a charged particle beam shielding film to a halfway depth so as to leave a film thickness capable of shielding the charged particle beam. A step of forming a strain measurement mark, and a step of etching until penetrating the charged particle beam shielding film to form a mask pattern including a through-hole to be transferred to the object to be exposed.

  In the stencil mask manufacturing method of the present invention described above, the stencil mask provided with the mask strain measurement mark is simply added to the mask strain measurement mark forming step before the mask pattern forming step. Is manufactured.

  In order to achieve the above object, the exposure method of the present invention comprises a mask pattern for mask distortion measurement comprising a mask pattern consisting of a through-hole to be transferred to an object to be exposed and a step leaving a film thickness capable of shielding charged particle beams. And a step of preparing a stencil mask formed on a charged particle beam shielding film, a step of measuring a position of the mask strain measurement mark of the stencil mask, and a position measurement result of the mask strain measurement mark And a step of correcting the transfer position of the mask pattern of the stencil mask and exposing the object to be exposed.

  In the above-described exposure method of the present invention, the exposure position of the stencil mask is corrected by correcting the transfer position of the mask pattern of the stencil mask based on the position measurement result of the mask distortion measurement mark, so that the exposure object is accurately exposed. The mask pattern is transferred. Since the film thickness that can shield the charged particle beam remains at the mask strain measurement mark, the mask strain measurement mark is not transferred to the object to be exposed.

According to the stencil mask and the manufacturing method thereof of the present invention, a stencil mask provided with a mask distortion measurement mark that can prevent transfer to an object to be exposed and can suppress stress distortion generated in the mark itself. Can be realized.
Further, according to the exposure method of the present invention, the mask pattern can be accurately transferred to the exposure object so as to cancel the mask distortion based on the measurement result of the mask distortion measurement mark, and the mask distortion measurement. The transfer mark can be prevented from being transferred to the object to be exposed.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, a stencil mask having only one membrane without a beam (hereinafter referred to as a collective membrane type stencil mask) will be described as an example.

  1A is a schematic plan view of a stencil mask according to the present embodiment, FIG. 1B is a schematic cross-sectional view of the stencil mask, and FIG. 1C is a plan view of a mark for mask distortion measurement. is there.

  As shown in FIG. 1A, the stencil mask 1 according to this embodiment is configured such that a membrane (charged particle beam shielding film) 3 is stretched in a central region surrounded by a support frame 2. In the present embodiment, no beam is present on the charged particle beam shielding film 3. The region of the charged particle beam shielding film 3 is, for example, a size of 2 to 3 nm square in consideration of mix and match exposure with photolithography.

  As shown in FIG. 1B, the charged particle beam shielding film 3 is thinner than the support frame 2. The stencil mask 1 is manufactured using, for example, an SOI substrate having a laminated structure of a silicon layer, a silicon oxide film, and a silicon substrate. In this case, the charged particle beam shielding film 3 is composed of a silicon layer, and the support frame is composed of a laminated structure of a silicon layer, a silicon oxide film, and a silicon substrate. The film thickness of the charged particle beam shielding film 3 is, for example, about 500 nm to 1000 nm, and the film thickness of the support frame is, for example, about 725 μm.

  On the charged particle beam shielding film 3, a mask pattern 5 to be transferred to an object to be exposed such as a wafer is formed by a through hole. The mask pattern 5 is, for example, a pattern in which a hole pattern transferred to a wafer is formed at an equal magnification without being complementary divided.

  On the charged particle beam shielding film 3, a mask strain measurement mark 4 for measuring mask strain is formed. Unlike the mask pattern 5, the mask strain measurement mark 4 is not a through hole but a step formed to leave a film thickness that can shield charged particle beams. When a 2 keV electron beam is used as the charged particle beam, for example, the mask strain measurement mark 4 is formed leaving a film thickness of 300 nm or more. Further, in the optical absolute position accuracy measuring device, the edge of the mask strain measurement mark 4 is detected by the step formed on the charged particle beam shielding film 3, so that, for example, a step of 50 nm or more, that is, 50 nm or more is engraved. Preferably it is.

  As shown in FIG. 1C, the mask distortion measuring mark 4 is constituted by, for example, a cross-shaped mark in which two strip patterns having a length L of 80 μm and a width W of 10 μm are combined in a cross shape. Since the mask pattern 5 is about 70 nm in size, for example, the mask distortion measurement mark 4 is larger than the mask pattern 5. In order to accurately detect the position of the mask distortion measurement mark 4, the mask pattern 5 may not be arranged in the area of the mask distortion measurement mark 4, for example, an L × L size area surrounded by a dotted line in the drawing. preferable. That is, the mask distortion measurement mark 4 is arranged in an empty area of the mask pattern 5 in the charged particle beam shielding film 3.

  Next, a method for manufacturing the stencil mask according to the present embodiment will be described with reference to FIG. FIG. 2 is a process cross-sectional view in manufacturing a stencil mask.

  First, as shown in FIG. 2A, a mask blank is prepared in which a support frame 2 is formed around and a charged particle beam shielding film 3 is formed in the center. Such a mask blank is manufactured using, for example, an 8-inch SOI substrate. The thickness of the silicon layer used as the charged particle beam shielding film 3 is 500 nm to 1000 nm, for example, 700 nm. After adjusting the stress of the silicon layer by performing ion implantation and annealing on the silicon layer of the SOI substrate, an etching mask having an opening at the center is formed on the silicon substrate side, and the center of the SOI substrate is formed using the etching mask. A mask blank is produced by removing the silicon substrate and the silicon oxide film.

  Next, as shown in FIG. 2 (b), an electron beam resist is applied to the charged particle beam shielding film 3 of the mask blank, and a pattern is formed on the mask strain measurement mark forming portion by direct drawing and development. A resist film 6 having an opening is formed. Although the number of marks to be formed depends on the time allowed for measurement, for example, 12 × 12 marks are formed in the region of the charged particle beam shielding film 3. At this time, it is necessary to arrange the marks so as to avoid interference between a mask pattern to be formed later and a mask distortion measurement mark.

  Next, as shown in FIG. 2C, the charged particle beam shielding film 3 is light-etched using the resist film 6 as an etching mask. In the light etching, the etching time is controlled so as not to etch until the charged particle beam shielding film 3 is penetrated. For the light etching, for example, dry etching is employed, and a chlorine-based gas is used. As a result, a mask strain measuring mark 4 is formed, which is composed of steps engraved to a depth in the middle of the charged particle beam shielding film 3. The level difference at this time may be an amount that can be detected by an optical mark measuring instrument (absolute position accuracy measuring instrument) and may be obtained experimentally. For example, a level difference of 200 nm is formed. After the etching, the resist film 6 is removed by ashing and cleaning.

  Next, as shown in FIG. 2 (d), a new electron beam resist is applied to the charged particle beam shielding film 3, and a resist film 7 having a pattern opening in a mask pattern formation region by direct electron beam writing and development. Form.

  Next, as shown in FIG. 2E, dry etching is performed using the resist film 7 as an etching mask until the charged particle beam shielding film 3 is penetrated. For the dry etching, for example, a chlorine-based gas is used. Thereby, the mask pattern 5 which consists of a through-hole is formed.

  As the above process, the stencil mask 1 shown in FIG. 1 is produced by removing the resist film 7 by ashing and washing.

  After the stencil mask 1 is manufactured, the mask distortion measurement mark 4 formed on the stencil mask 1 is measured with an optical absolute position accuracy measuring instrument. As an optical absolute position accuracy measuring instrument, for example, IPRO manufactured by LEICA is used.

  FIG. 3 is a diagram illustrating an example of a position measurement result of the mask distortion measurement mark 4 of the stencil mask 1. FIG. 3 shows the result of measuring the positions of 12 × 12 mask distortion measurement marks 4 arranged on the charged particle beam shielding film 3.

  As shown in FIG. 3, the position of the mask distortion measurement mark 4 is ideally an ideal lattice indicated by a dotted line, but in the actual stencil mask 1, the stress of the charged particle beam shielding film 3 due to the formation of the mask pattern 5. It can be seen that the position of the mask distortion measurement mark 4 is displaced from the ideal lattice due to the opening and is distorted. Based on the positional deviation of the mask distortion measurement mark 4, the positional deviation of the surrounding mask pattern 5 is obtained by linear interpolation or the like.

  The stencil mask 1 whose mask distortion has been measured is set in an exposure apparatus and used for exposure.

  FIG. 4 is a schematic block diagram of an exposure apparatus that performs the exposure method according to the present embodiment. The exposure apparatus shown in FIG. 4 is an exposure apparatus applied to the LEEPL technology.

  The exposure apparatus shown in FIG. 4 includes an electron gun 101 that emits an electron beam EB as a charged particle beam, a condenser lens 102 that collimates the electron beam EB, an aperture 103 that limits the electron beam EB, and an electron beam EB that is rastered. Alternatively, a pair of main deflectors 104a and 104b deflecting to enter the stencil mask 1 in either one of the vector scanning modes and the electron to correct the transfer position of the mask pattern onto the exposure object 10 such as a wafer. Sub-deflectors 105a and 105b for adjusting the incident angle of the line EB to the stencil mask 1 are provided.

  In the exposure apparatus shown in FIG. 4, low acceleration electrons of about 2 kV are used. In FIG. 4, a resist (not shown) of the object to be exposed 10 is exposed by the electron beam EB that has passed through the mask pattern 5 formed of the through hole of the stencil mask 1. The exposure apparatus shown in FIG. 4 employs the same magnification exposure, and the stencil mask 1 and the object to be exposed 10 are arranged close to each other.

  The data processing unit 107 creates correction data based on the input mask distortion data D, and outputs the correction data to the control unit 106. That is, the data processing means 107 obtains the deviation amount of the surrounding mask pattern by linear interpolation or the like based on the deviation amount from the design value of the mask distortion measurement mark 4. Then, for example, correction data including a correction map that defines the correction amount for each coordinate of the stencil mask 1 is created using the negative value of the positional deviation amount of the mask pattern as a correction amount.

  The control means 106 controls the operation of the entire apparatus. For example, the main deflectors 104 a and 104 b are controlled to scan the electron beam EB on the stencil mask 1, and the pattern of the stencil mask 1 is transferred to the object to be exposed 10. At the time of this exposure, correction data in which a correction value is defined for each coordinate on the stencil mask 1 is read from the data processing means 107, and the sub-deflectors 105a and 105b are controlled to slightly deflect the electron beam EB. The mask pattern 5 of the stencil mask 1 displaced from the correct position is corrected and transferred to the correct position on the object 10 to be exposed. As shown in FIG. 4, the irradiation position of the electron beam EB to the object to be exposed 10 can be moved by Δ by controlling the irradiation angle.

  As described above, by irradiating the electron beam EB while controlling the irradiation angle, the position error of the mask pattern 5 formed on the stencil mask 1 is canceled, and the position is faithful to the design position. Transfer the mask pattern.

  The electron beam EB is scanned over the entire surface of the charged particle beam shielding film 3 in the stencil mask 1, but the charged particle beam shielding film 3 having a thickness of 300 nm or more remains at the mask strain measurement mark 4. Therefore, the mask distortion measuring mark 4 is not transferred to the object 10 to be exposed.

  The stencil mask 1 and the exposure method according to the present embodiment are suitably used in an exposure process in manufacturing a semiconductor device. FIG. 5 is a process cross-sectional view in the manufacture of a semiconductor device.

  In the manufacture of a semiconductor device, as shown in FIG. 5A, for example, a layer 12 to be processed such as polysilicon or silicon oxide is formed on a substrate 11 made of silicon, and an electron beam resist is formed on the layer 12 to be processed. An object to be exposed 10 on which a resist film 13 made of is formed is used.

  As shown in FIG. 5A, the exposure object 10 is exposed using the stencil mask 1. In the scanning of the electron beam EB on the charged particle beam shielding film 3, the incident angle of the electron beam EB is adjusted for each position of the charged particle beam shielding film 3. For example, if the mask patterns 5a and 5b are formed at the designed positions, the electron beams EB1 and EB2 are irradiated perpendicularly to the object to be exposed 10 at the positions of the mask patterns 5a and 5b. Further, when the mask pattern 5c is deviated from the design value, the electron beam EB3 having an incident angle adjusted so as to be transferred after being corrected by the amount of deviation is irradiated. Although the electron beam EB4 is also irradiated on the mask distortion measurement mark 4, the passage of the electron beam EB4 in the mask distortion measurement mark 4 is blocked. Thus, the resist film 13 of the object to be exposed 10 is exposed by the electron beam EB that has passed through the mask pattern 5 formed on the charged particle beam shielding film 3.

  Next, as shown in FIG. 5B, by developing the resist film 13, for example, if the resist film 13 is a positive type, the electron beam irradiation portion is removed and a pattern is formed on the resist film 13. .

  Next, as shown in FIG. 5C, the processed layer 12 is etched by using the resist film 13 as a mask to pattern the processed layer 12 to form a circuit pattern. An example of the circuit pattern is a contact hole pattern.

  Thereafter, as shown in FIG. 5D, the resist film 13 is removed to complete the pattern processing of the layer 12 to be processed.

  In the manufacture of a semiconductor device, an upper layer is further deposited, and an integrated circuit is formed by repeating the same steps as in FIGS. 5A to 5D. In this case, even if electron beam exposure is used for processing of all layers, only critical layers such as holes are processed using the electron beam exposure method according to this embodiment, and other layers are used by light exposure. Mix and match exposure such as processing may be used.

  As described above, the stencil mask according to the present embodiment includes the mask distortion measurement mark 4 which is not a through hole but a step, so that the electron beam can be shielded at the location of the mask distortion measurement mark 4. The mask distortion measuring mark 4 is not transferred to the object 10 to be exposed.

  Further, since the mask strain measurement mark 4 is formed while leaving a film thickness that can shield the electron beam instead of the through hole, the mask strain measurement mark 4 is formed on the charged particle beam shield film 3. Stress strain can be suppressed.

  The method for manufacturing a stencil mask according to the present embodiment is practical in terms of cost and throughput because the stencil mask can be manufactured only by adding a lithography process for forming the mask distortion measurement mark 4 separately. It will be something like that.

  In the exposure method using the stencil mask, the mask pattern can be accurately transferred to the exposure object so as to cancel out the mask distortion based on the measurement result of the mask distortion measurement mark formed on the stencil mask. it can. Further, the mask distortion measurement mark is not transferred to the object to be exposed.

The present invention is not limited to the description of the above embodiment.
For example, in the present embodiment, a stencil mask having only one membrane without a beam has been described as an example. Is also applicable.

In this embodiment, an example in which an electron beam is used as a charged particle beam has been described. However, an ion beam can also be employed. In the present embodiment, the electron beam equal-magnification exposure apparatus has been described as an example of an exposure apparatus that uses a stencil mask, but it can also be used in an electron beam reduced projection exposure apparatus. Furthermore, the materials and numerical values described in the present embodiment are examples, and the present invention is not limited to these.
In addition, various modifications can be made without departing from the scope of the present invention.

(A) is a schematic plan view of the stencil mask which concerns on this embodiment, (b) is a schematic cross section of a stencil mask, (c) is a top view of the mask distortion measurement mark. It is process sectional drawing in manufacture of the stencil mask which concerns on this embodiment. It is a figure which shows an example of the position measurement result of the mask distortion measurement mark of a stencil mask. It is a schematic block diagram of the exposure apparatus which enforces the exposure method which concerns on this embodiment. It is process sectional drawing in manufacture of the semiconductor device to which the exposure method concerning this embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Stencil mask, 2 ... Support frame, 3 ... Charged particle beam shielding film, 4 ... Mask distortion measurement mark, 5 ... Mask pattern, 6 ... Resist film, 7 ... Resist film, 10 ... Exposed body, 11 ... Substrate , 12 ... layer to be processed, 13 ... resist film, 101 ... electron gun, 102 ... condenser lens, 103 ... aperture, 104a, 104b ... main deflector, 105a, 105b ... sub deflector, 106 ... control means, 107 ... data Processing means, D ... mask distortion data, EB ... electron beam

Claims (8)

A charged particle beam shielding film;
A mask pattern consisting of a through-hole formed in the charged particle beam shielding film and transferred to an object to be exposed;
A stencil mask having a mask distortion measuring mark made of a step formed by leaving a film thickness capable of shielding a charged particle beam on the charged particle beam shielding film. The stencil mask according to claim 1, wherein the mask distortion measurement mark is formed with a step having a size that can be detected optically. The stencil mask according to claim 1, further comprising a support frame that supports the charged particle beam shielding film, wherein one of the charged particle beam shielding films is stretched in the support frame. Etching the charged particle beam shielding film to an intermediate depth so as to leave a film thickness capable of shielding the charged particle beam, and forming a mask strain measurement mark consisting of a step; and
Etching until penetrating the charged particle beam shielding film to form a mask pattern comprising through-holes to be transferred to the object to be exposed. A method for producing a stencil mask. The stencil mask manufacturing method according to claim 4, wherein in the step of forming the mask strain measurement mark, the mask strain measurement mark having a level difference that can be detected optically is formed. A stencil mask with a mask pattern consisting of through-holes to be transferred to an object to be exposed and a mask strain measurement mark consisting of a step leaving a film thickness that can shield charged particle beams is prepared on the charged particle beam shielding film. And a process of
Measuring the position of the mask distortion measurement mark of the stencil mask;
And exposing the object to be exposed by correcting a transfer position of the mask pattern of the stencil mask based on a position measurement result of the mask distortion measurement mark. The exposure method according to claim 6, further comprising a support frame that supports the charged particle beam shielding film, wherein the stencil mask configured with one charged particle beam shielding film stretched in the support frame is used. The exposure method according to claim 6, wherein in the step of exposing the object to be exposed, a transfer position of the mask pattern of the stencil mask is corrected by adjusting an incident angle of the charged particle beam to the stencil mask.

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