JP5724766B2 - Exposure mask, pellicle and semiconductor device manufacturing method - Google Patents

Description

  The present invention relates to an exposure mask and a method for manufacturing a semiconductor device using the exposure mask.

  In the manufacture of a semiconductor device, an exposure mask carrying a predetermined device pattern is used, and the predetermined device pattern is covered by a reduced projection exposure apparatus using a short wavelength light source with high resolution such as ultraviolet light. A photosensitive resist that is projected onto a processing substrate and applied onto the substrate to be processed is exposed.

JP 2008-96741 A JP-A 61-185929 JP-A-6-215996

  In general, an exposure mask is composed of a reticle made of a substrate such as quartz glass having a transmittance with respect to light of an exposure wavelength, and a predetermined device pattern printed on the pattern forming surface, and the pattern of the reticle. A pellicle that protects a forming surface, and the pellicle is mounted on the pattern forming surface so as to surround a pattern forming region where the device pattern is formed; It is composed of a protective film (hereinafter referred to as “pellicle film”) that closes the opening formed by the frame member and is transparent to the light having the exposure wavelength.

  On the other hand, on the pattern forming surface of the reticle, in addition to the device pattern to be transferred to the substrate to be processed, there are various alignment marks for aligning the reticle and various visible patterns for the operator. Symbols are written. These alignment marks and symbols should not be transferred to the substrate to be processed.

  However, when such an exposure mask is attached to a reduction projection exposure apparatus and exposure is performed, alignment marks and symbols (not to be transferred) such as stray light (flare light) generated in the exposure apparatus ( (Hereinafter referred to as “non-exposure pattern”) may be transferred to the substrate to be processed and patterned into the original device pattern region. The influence of such improper transfer is particularly noticeable in a semiconductor device having a high integration density and a large number of regular repetitions, such as a memory, and as a result, the line width changes in these semiconductor devices. Electrical characteristics may be modulated.

  According to one feature, the exposure mask includes a reticle having a pattern formation surface, and a pellicle mounted on the pattern formation surface of the reticle, and the reticle includes the pattern formation surface. An exposure pattern is carried in the exposure area, and a non-exposure pattern is carried outside the exposure area. The pellicle is mounted on the pattern forming surface of the reticle and surrounds the exposure area. A frame member; and a protective film that covers the exposure region at an edge of the frame member far from the reticle, and that is transparent to ultraviolet light having an exposure wavelength. The pellicle further includes the reticle. Including a cover member that covers the non-exposure pattern while avoiding the exposure region, and the cover member is made of a material that transmits visible light and shields light having the exposure wavelength. The

  According to the present invention, the provision of the cover member causes a problem that non-exposure patterns formed outside the exposure area on the pattern formation surface of the reticle are transferred to the substrate to be processed by stray light. Solved.

It is a perspective view which shows the outline | summary of the exposure apparatus used in 1st Embodiment. It is a top view which shows the reticle used in 1st Embodiment. FIG. 2B is a sectional view taken along line A-A ′ in FIG. 2A. It is a top view which shows the exposure mask used in 1st Embodiment. FIG. 3B is a cross-sectional view taken along line B-B ′ in FIG. 3A. It is a figure which shows the outline | summary of the exposure performed using the exposure mask by 1st Embodiment in the exposure apparatus of FIG. It is a graph which shows the light transmittance of a polycarbonate. It is a figure which shows the outline | summary of the exposure performed using the exposure mask by a comparative example. FIG. 6 is a diagram (part 1) illustrating a manufacturing process of a pellicle according to the first embodiment; FIG. 6 is a diagram (No. 2) illustrating a pellicle manufacturing process according to the first embodiment; FIG. 8 is a diagram (No. 3) showing a pellicle manufacturing process according to the first embodiment; FIG. 8 is a diagram (No. 4) for explaining a pellicle manufacturing process according to the first embodiment; FIG. 10 is a diagram (No. 5) for illustrating a manufacturing process of the pellicle according to the first embodiment; FIG. 6 is a view (No. 6) showing a pellicle manufacturing process according to the first embodiment; FIG. 8 is a view (No. 7) showing a manufacturing process of the pellicle according to the first embodiment. It is sectional drawing which shows one modification of 1st Embodiment. It is a top view which shows the reticle used in 2nd Embodiment. It is a disassembled perspective view which shows the pellicle by 2nd Embodiment. It is an expanded sectional view which shows a part of exposure mask by 2nd Embodiment.

[First Embodiment]
FIG. 1 shows an example of a reduction projection exposure apparatus 10 called a scanner used in this embodiment.

  Referring to FIG. 1, a reduction projection exposure apparatus 10 includes a light source 11 and a wafer scanning stage 12 that holds and moves a substrate to be processed W. A first implementation is provided between the light source 11 and the wafer scanning stage 12. There is provided a reticle scanning stage 13 that carries an exposure mask 14 according to the configuration.

  The light source 11 is a light source that generates an exposure beam having a far ultraviolet (DUV) wavelength, such as an excimer laser. The exposure beam emitted from the light source 11 is reflected by a mirror 15 and then is reflected by the collimator lens system 16 to the reticle. The exposure mask 14 on the scanning stage 13 is irradiated as a parallel light beam.

  The exposure beam irradiated onto the exposure mask 14 in this way is shaped according to a desired semiconductor circuit pattern held by the reticle of the exposure mask 14 when passing through the exposure mask 14, and the reticle scanning stage. 13 is focused on the surface of the substrate W to be processed by the projection lens system 17 provided between the wafer scanning stage 12 and the wafer scanning stage 12.

  2A is a plan view showing a reticle 14A constituting a part of the exposure mask 14, and FIG. 2B is a sectional view taken along line A-A 'in FIG. 2A.

  Referring to FIGS. 2A and 2B, the reticle 14A has a glass substrate 21 made of, for example, quartz glass that is transparent to the light having the wavelength of the exposure beam, and is formed on the pattern forming surface 21A of the glass substrate 21. A light shielding band 22 is formed by patterning a metal film such as Cr that is opaque to the exposure beam, and the light shielding band 22 defines an exposure region 23 on the pattern forming surface 21A. Yes. Further, an exposure pattern 23A corresponding to the pattern of the semiconductor circuit to be exposed is formed on the pattern forming surface 21A by patterning the metal film in the exposure region 23.

  By passing through the reticle 14A, the exposure beam is shaped according to a desired exposure pattern 23A, and the shaped exposure beam is focused on the substrate W to be processed by the projection lens system 17. Thus, a desired semiconductor pattern is imaged on the substrate W to be processed, and desired exposure is performed.

  In such a reticle 14A, the reticle 14A is positioned on the reticle scanning stage 13 of the exposure apparatus 10 on the pattern forming surface 21A of the glass substrate 21 and outside the light shielding band 22, that is, outside the exposure region 23. A non-exposure pattern such as an alignment mark 23B to be used and various symbols 23C for the operator or exposure apparatus control system to identify the reticle 14A are also written by patterning the metal film. Such symbols include barcodes in addition to alphanumeric characters.

  When the reticle 14A is mounted on the exposure apparatus 10, such symbols 23C are read and the exposure mask 14 is aligned using the alignment mark 23B. Such alignment is generally performed using visible light rather than ultraviolet light used for exposure.

  In the exposure mask 14 shown in FIG. 1, a pellicle 25 is further provided on the reticle 14A in order to protect the exposure pattern 23A on the pattern formation region 21A. That is, in the reduced projection exposure apparatus 10 of FIG. 1, the exposure mask 14 is composed of the reticle 14A and the pellicle 25.

  FIGS. 3A and 3B are a plan view and a cross-sectional view taken along line B-B ′ in FIG. 3A, respectively, showing the exposure mask 14 in a state where such a pellicle 25 is provided.

  3A and 3B, the pellicle 25 includes a frame member 25A and a pellicle film 25B attached to the frame member 25A. The frame member 25A is attached to the pattern forming surface 21A of the glass substrate 21. Further, it is attached to the exposure mask 14 by adhering via the adhesive layer 25a. The pellicle 25 has a function of covering the semiconductor pattern 23A formed on the pattern forming surface 21A with the frame member 25A and the pellicle film 25B and protecting it from dust and the like. The pellicle film 25B is made of, for example, a fluorine polymer film that is transparent to the exposure wavelength, but is not shown in the plan view of FIG. 3A.

  The pellicle 25 has a height of about 2 to 7 millimeters, for example. Even if dust or the like is deposited on the pellicle film 25B, the shadow is covered if the size is about several tens of microns or less. Imaging on the surface of the processing substrate W can be avoided. Similarly, the glass substrate 21 has a thickness of about 2 to 7 millimeters, and even if dust accumulates on the lower surface of the glass substrate 21, the shadow is imaged on the surface of the substrate W to be processed. Absent.

  Further, the pellicle 25 is close to the pattern forming surface 21A and has a thickness made of, for example, polycarbonate or ultraviolet light cut glass, which transmits visible light but does not transmit exposure wavelength. A cover film 25C having a length of, for example, several tens of microns to 3 mm is provided in the vicinity of the pattern forming surface 21A. At this time, the cover film 25C is formed on the pattern forming surface 21A from the frame member 25A to the light shielding band 22, that is, on the pattern forming surface 21A, the non-exposed pattern 23B or the like. It is formed so as to cover 23C.

  In the illustrated example, the cover film 25C is bonded to the pattern forming surface 21A by the adhesive layer 25a, but the cover film 25C is also applied to the frame member 25A by a similar adhesive layer 25b (FIG. 8G). Are attached). The cover film 25C is preferably formed as close as possible to the pattern forming surface 21A of the substrate 21 so that diffracted light from the edge of the cover film 25C does not enter the projection lens system 17. Although it may be formed in contact with the pattern forming surface 21A, there is a risk of dust generation when the cover film 25C comes in contact with the pattern forming surface 21A. preferable.

  FIG. 4 is a cross-sectional view showing a state in which the substrate W to be processed is exposed by the exposure mask 14 mounted on the reduced projection exposure apparatus 10.

  Referring to FIG. 4, an exposure mask 14 having the configuration shown in FIG. 3B is mounted on a reticle scanning stage 13 (not shown) in an upside down state, and although not shown, it is visible as described above. It is aligned at a predetermined position on the reticle scanning stage 13 using light.

  In the state of FIG. 4, the exposure beam 11A from the light source 11 is irradiated to the reticle 14A constituting the exposure mask 14 in the form of parallel light by the collimating lens system 16 (not shown). When passing through the reticle 14A, it is shaped by the semiconductor pattern 23A formed on the pattern forming surface 21A of the glass substrate 21.

  The shaped exposure beam 11A is focused on the target substrate W by the projection lens system 17, and the resist film on the target substrate W is exposed according to a desired exposure pattern 23A.

  By the way, in such a reduced projection exposure apparatus 10, the exposure beam 11A from the light source 11 enters the exposure region 13 of the reticle 14A constituting the exposure mask 14 in the form of a parallel light beam as shown in FIG. However, stray light 11B indicated by a broken line in FIG. 4 may be generated in the middle of the optical path from the light source 11 to the exposure mask 14 due to diffraction or scattering. Such stray light 11B does not necessarily become a parallel light beam, but diffuses to irradiate a region of the reticle 14A where an alignment mark 23B outside the exposure region 23, a symbol 23C for an operator, and the like are written. There is a case.

  Therefore, the stray light 11B is shaped by the alignment mark 23B, the symbol 23C, and the like, and then forms an image on the surface of the substrate W to be processed when incident on the projection lens system 17, but in this embodiment, For example, a cover film 25C that transmits visible light but does not transmit the wavelength of the exposure beam 11A as shown in FIG. 5 is applied to the pellicle 25 from the frame 25B of the pattern forming surface 21A. The stray light 11 </ b> B is shielded by the cover film 25 </ b> C and is not projected onto the substrate W to be processed via the projection lens system 17 because it is formed so as to cover the area up to the light shielding band 22. However, FIG. 5 is a graph showing the relationship between the light transmittance of the polycarbonate and the wavelength. For example, it can be seen that an ultraviolet light wavelength of about 400 nm or less can be shielded by using polycarbonate as the material of the cover film 25C. .

  That is, according to the present embodiment, the non-exposure patterns such as the alignment mark 23B and various symbols 23C written outside the exposure area 23 of the reticle 14A are written on the substrate W to be processed by the stray light 11B. This will eliminate the problem.

  FIG. 6 is a cross-sectional view showing a comparative example of exposure of the substrate W to be processed by the exposure mask 140 similar to FIG. In the comparative example of FIG. 6, the exposure mask 140 uses the same reticle 1 as in the previous embodiment, but instead of the pellicle 25, a pellicle 250 from which the cover film 25C is omitted is used. In FIG. 6, the parts described above are denoted by the same reference numerals, and description thereof is omitted.

  Referring to FIG. 6, since the cover film 25C is omitted in this comparative example, the stray light 11B is not shielded after passing through the reticle 14A, and enters the projection lens system 17 as it is, and is processed. The light is condensed on the surface of the substrate W.

  In the present embodiment, by using the pellicle 25 having the cover film 25C, it is possible to suppress such multiple exposure due to the stray light 11B. It is sufficient that the cover film 25C covers the non-exposure pattern such as the alignment mark 25B and symbols 25C in the pattern forming surface 21A of the glass substrate 21, and the cover film 25C is formed from the frame member 25A. It is sufficient to cover the area up to the light shielding band 22, but as long as the exposure area 23 is not covered, there is no problem even if a part or the whole of the light shielding band 22 is covered. Since the cover film 25C is transmissive to visible light, there is no problem with the alignment of the reticle 14A performed using visible light.

  In particular, by forming the cover film 25C in the vicinity of the glass substrate 21 with the reticle in the pellicle 25, multiple exposure due to stray light 11B can be more effectively avoided.

  Hereinafter, a method for manufacturing the pellicle 25 will be described.

  Referring to FIG. 7A, an aluminum material or the like is first processed to produce the frame member 25A, which is cleaned and then anodized to stabilize the surface.

  7B, a resin material 32 to be the pellicle film 25B is dropped in a liquid state on the glass plate 31, and the glass plate 31 is rotated at a high speed as shown in FIG. The pellicle film 25B is formed.

  Further, the glass plate 31 is heated to peel off the pellicle film 25B as shown in FIG. 7D.

  On the other hand, as shown in FIG. 7E, a plate such as polycarbonate or ultraviolet cut glass is processed by means such as cutting or injection molding to form a member corresponding to the cover film 25C, and this is formed into an adhesive layer 25b. It adheres to one side of the frame member 25A via For the adhesive layer 25b, see FIG. 7G described later. When the exposure mask 14 is mounted on the projection reduction exposure apparatus 10 shown in FIG. 1, the polycarbonate or ultraviolet cut glass plate can recognize the alignment marks 23B and symbols 23C through the cover film 25C. For example, the thickness is preferably less than half the height of the frame member 25A. For example, as described above, it preferably has a thickness of several tens of microns to 3 mm.

  Further, as shown in FIG. 7F, an adhesive is applied to the other side of the frame member 25A having the cover film 25C thus formed on one side, and the pellicle film 25B is adhered. Thereby, the pellicle 25 is completed.

  In the completed pellicle 25, as shown in FIG. 7G, an adhesive layer 25a is formed on a part of the cover film 25C, and the adhesive layer is formed on the pattern forming surface 21A of the glass substrate 21 constituting the reticle 14A. It adheres via 25a. According to such a configuration, the cover film 25C can be formed as close as possible to the glass substrate 21 of the reticle 14A, so that the stray light 11B can be efficiently shielded as can be seen from FIG.

  At this time, as shown in FIG. 7G, the cover film 25C is slightly separated from the pattern forming surface 21A of the glass substrate 21, so that the cover film 25C is directly applied to the glass substrate 21. This is advantageous because it can avoid the problem of dusting that may occur when it touches.

  In the present embodiment, since the cover film 25C is provided integrally with the pellicle 25 in the process of FIG. 7G, it is not necessary to handle the pellicle 25 and the cover film 25C separately, and the handling becomes easy.

  FIG. 8 shows a modification of the present embodiment, and shows a configuration in which the protective cover 25C is held in a recess 25c formed on one side of the frame member 25A. In this case, the end of the protective cover 25C is held by the adhesive layer 25b in the recess 25c, and the frame member 25A has the side holding the protective cover 25C attached to the reticle 14A via the adhesive layer 25a. Glued.

[Second Embodiment]
FIG. 9 is a plan view showing a configuration of a reticle 14B used in the second embodiment. In FIG. 9, the same reference numerals are given to the portions described above with reference to FIG.

  Referring to FIG. 9, in the present embodiment, another symbol 23D is written as a non-exposure pattern along the outer periphery of the glass substrate 21 in the reticle 14B, and the pellicle 45 shown in FIG. As shown by a broken line in FIG. 9, the frame member 25A is bonded between the non-exposure pattern 23C and the non-exposure pattern 23D.

  FIG. 10 is an exploded perspective view showing a configuration according to the second embodiment of such a pellicle 45.

  Referring to FIG. 10, the pellicle 45 has the same frame member 25A, pellicle film 25B, and cover film 25C as in the previous embodiment. In this embodiment, the cover film 25C is located outside the frame member 25A. The outer cover film 25D is formed. The outer cover film 25D extends on the outer periphery of the glass substrate 21 constituting the reticle 14B to the vicinity of the suction holding position of the scanner or stepper, and covers the non-exposure pattern 23D formed along the outer periphery of the pellicle 45.

  FIG. 11 is an enlarged cross-sectional view showing a part of the exposure mask 44 formed in this way.

  Referring to FIG. 11, in the exposure mask 44, a cover film 25C covering the non-exposure pattern 23C extends to the outside of the frame member 25A to form an outer cover film 25D covering the non-exposure pattern 23D. You can see that However, in the present embodiment, the outer cover film 25D does not necessarily extend to the outer periphery of the glass substrate 21, and only needs to cover the non-exposure pattern 23D outside the frame member 25A.

  Also in this embodiment, it is preferable from the viewpoint of dust generation that the cover films 25C and 25D are separated from the pattern forming surface 21A of the glass substrate 21 by several tens of microns or more.

  Although the above description has been given mainly for an example using a so-called negative exposure mask, the same description is valid for a positive exposure mask.

  Further, the above description holds true not only when the reticle is a so-called binary type reticle but also when the reticle is a halftone type or Levenson type reticle using phase shift.

  In the above description, the case where the scanner type apparatus 10 of FIG. 1 is used as the projection reduction exposure apparatus has been described, but this embodiment is also effective in the case of exposure using a stepper.

  As mentioned above, although this invention was described about preferable embodiment, this invention is not limited to this specific embodiment, A various deformation | transformation and change are possible within the summary described in the claim.

DESCRIPTION OF SYMBOLS 10 Reduction projection exposure apparatus 11 Light source 11A Exposure beam 11B Stray light 12 Wafer scanning stage 13 Reticle scanning stage 14, 44, 140 Exposure mask 14A, 14B Reticle 15 Mirror 16 Collimating lens system 17 Projection lens system 21 Glass substrate 22 Shading zone 23 Exposure area 23A Exposure pattern 23B Alignment mark 23C, 23D Symbols 25, 45 Pellicle 25A Frame member 25a, 25b Adhesive layer 25B Pellicle film 25C, 25D Cover film 31 Glass plate 32 Resin material

Claims (6)

A reticle having a pattern forming surface;
A pellicle mounted on the pattern forming surface of the reticle,
The reticle carries an exposure pattern in an exposure area of the pattern forming surface and a non-exposure pattern outside the exposure area,
The pellicle is mounted on the pattern forming surface of the reticle and surrounds the exposure region, and the pellicle is provided on the edge of the frame member on the side far from the reticle so as to cover the exposure region. A protective film that transmits ultraviolet light of
The pellicle further includes a cover member that covers the non-exposed pattern on the pattern forming surface of the reticle,
An exposure mask, wherein the cover member is made of a material that transmits visible light and shields light having the exposure wavelength. 2. The exposure mask according to claim 1, wherein the cover member covers at least a range of the pattern forming surface of the reticle from the frame member to a light shielding band. 3. The exposure mask according to claim 2, wherein the cover member further covers a region outside a region where the frame member is mounted on the pattern forming surface of the reticle. 4. The frame member according to claim 1, wherein an edge of the frame member facing the edge is bonded to the pattern forming surface via the cover member and an adhesive layer. The exposure mask according to item. A frame member;
A film that is attached to an edge of one side of the frame member and transmits ultraviolet light that covers a space surrounded by the frame member;
A pellicle including a cover film made of a material that transmits visible light and shields ultraviolet light, which is attached to an edge of the other side of the frame;
The cover film in the inside of the frame member, of the patterned surface of the reticle in which the pellicle is mounted, is formed to avoid the area where the exposure pattern is formed to cover the regions where non-exposure pattern is formed A pellicle characterized by that.   A method for manufacturing a semiconductor device, comprising: exposing a substrate to be processed using the exposure mask according to claim 1.

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