JP2009080381A - Photomask and method for manufacturing electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress misalignment in patterns to be formed in the exposure steps using photomasks in the manufacturing process of a semiconductor element or the like. <P>SOLUTION: A photomask 60 can be commonly used for patterning both of a trench and a contact hole disposed inside the trench in a dual damascene wiring structure. The photomask 60 includes layers of a first light-shielding layer 64 and a second light-shielding layer 66. The first light-shielding layer 64 has light-shielding property against first irradiation light and has an aperture 68 corresponding to the trench. The second light-shielding layer 66 has light-shielding property against second irradiation light, transmitting property for the first irradiation light and an aperture 70 corresponding to the contact hole. When the photomask 60 is irradiated with the first irradiation light, a trench pattern can be formed by the exposure; and when the photomask is irradiated with the second irradiation light, a contact hole pattern can be formed by the exposure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photomask used in photolithography technology and a manufacturing method for manufacturing an electronic device such as a semiconductor element or a wiring board device using the photomask.

  In recent years, copper and tungsten having a low specific resistance are often used as wiring materials for semiconductor elements. Since these metals are difficult to process by reactive ion etching, when they are used as a wiring material, wiring is formed using a damascene method. As the damascene method, a single damascene method in which contacts and wirings are formed in stages, and a dual damascene method in which contacts and wirings are formed simultaneously are known.

  5 and 6 are element cross-sectional views showing a manufacturing process of a wiring structure by a dual damascene method in a semiconductor element, and show a vertical cross section of the element in main steps of the manufacturing process. For example, a contact hole for forming a contact (via) and a groove (trench) of a wiring portion disposed so as to overlap the contact hole are sequentially formed, and a wiring material is embedded in the formed contact hole and trench.

  In FIG. 5A, the first wiring 4 is formed in the trench formed in the first insulating film 2 on the substrate (not shown), and the diffusion preventing film 6 and the second insulating film 8 are formed in this order on the first wiring 4. Shows the stage. After the first insulating film 2 is formed on the substrate, a wiring trench is formed by dry etching, and a barrier metal film (not shown) and a copper film are formed in this order so as to fill the inside. Then, by removing the unnecessary barrier metal film and copper film formed outside the wiring trench by CMP (Chemical Mechanical Polishing), the first wiring 4 is formed. Next, a diffusion prevention film 6 is formed on the first wiring 4. The diffusion preventing film 6 is formed to prevent diffusion of copper into the insulating film and to be used as an etching stopper film when forming contact holes. Then, a second insulating film 8 is formed on the diffusion preventing film 6. For example, a low dielectric constant interlayer insulating film is used for the second insulating film 8.

  Subsequently, an antireflection film and a photoresist film 10 (not shown) are formed in this order on the second insulating film 8, and the photoresist film 10 is patterned by a photolithography technique using a photomask 12 set in an exposure apparatus. (FIG. 5B). 7A and 7B are schematic views of a conventional photomask 12 used for patterning when the photoresist film 10 is formed of a positive resist. FIG. 7A is a plan view, and FIG. The XX 'cross section in (a) is represented. The photomask 12 is for performing exposure using, for example, a KrF excimer laser (wavelength 248 nm) as the irradiation light 14, and chromium (Cr) is formed on a substrate 40 such as glass that suitably transmits the KrF excimer laser. The film 42 is formed as a light shielding film. The Cr film 42 has an opening 44 corresponding to a region where the contact hole 16 is formed.

  The irradiation light 14 passes through the opening of the photomask 12 and exposes the photoresist film 10. By performing the development process, the exposed portion of the photoresist film 10 is selectively removed, and an opening 18 is formed at a predetermined position of the contact hole 16 (FIG. 5C).

  Using this photoresist film 10 as an etching mask, dry etching is performed to form contact holes 16 (FIG. 5D). At this time, the etching is stopped on the diffusion prevention film 6 due to the difference in etching rate between the second insulating film 8 and the diffusion prevention film 6. This is to prevent copper contamination due to exposure of the first wiring 4, ashing after etching, and damage to copper in the cleaning process. After the etching, the photoresist film 10 and the antireflection film are removed by ashing.

  Next, an antireflection film and a photoresist film 20 (not shown) are formed in this order on the second insulating film 8, and the photoresist film 20 is patterned by a photolithography technique using a photomask 22 set in an exposure apparatus. (FIG. 5E). 8A and 8B are schematic views of a conventional photomask 22 used for patterning when the photoresist film 20 is formed of a positive resist. FIG. 8A is a plan view, and FIG. The XX 'cross section in (a) is represented. The photomask 22 is for performing exposure using, for example, a KrF excimer laser as the irradiation light 24, and a Cr film 48 is formed as a light shielding film on a substrate 46 such as glass that suitably transmits the KrF excimer laser. Is done. The Cr film 48 has an opening 50 corresponding to a region where the trench 26 is formed.

  The irradiation light 24 passes through the opening of the photomask 22 and exposes the photoresist film 20 (FIG. 5E). By performing the development process, the exposed portion of the photoresist film 20 is selectively removed, and an opening 28 is formed at a predetermined position of the trench 26 (FIG. 6A).

  Using this photoresist film 20 as an etching mask, dry etching is performed to form a trench 26 (FIG. 6B). At this time, since the antireflection film or the photoresist film 20 is embedded in the contact hole 16, the etching does not proceed in the contact hole 16. After the etching, the photoresist film 20 and the antireflection film are removed by ashing.

Further, the diffusion prevention film 6 at the bottom of the contact hole 16 is removed by dry etching to expose the first wiring 4 (FIG. 6C). In this way, the contact hole 16 and the trench 26 are formed, and a barrier metal film 30 and a copper film (not shown) as an electroplating seed layer are formed in this order on the entire second insulating film 8 including them by sputtering. To do. Then, the copper film 32 is embedded in the contact hole 16 and the trench 26 by electroplating (FIG. 6D). Unnecessary portions of the copper film 32 and the barrier metal film 30 are removed by CMP, and the copper film 32 in the trench 26, that is, the second wiring 34, and the contact 36 connecting the first wiring 4 and the second wiring 34 are formed. (FIG. 6 (e)).
JP 2004-179588 A

  Since the etching masks for forming the contact holes 16 and the trenches 26 in the formation of the dual damascene wiring structure described above have different patterns, they are formed using different photoresist films. In such a case, conventionally, a separate photomask as shown in FIGS. 7 and 8 is used for exposure of each photoresist film.

  When a wafer is exposed with a photomask set in an exposure apparatus, an error occurs in a pattern formed on the wafer due to various factors. For example, an error may occur in the position of the light shielding film with respect to the substrate of the photomask due to manufacturing variations of the photomask. An error may also occur in alignment when the photomask is set in the exposure apparatus. When a plurality of photomasks are used, these errors occur for each photomask. As a result, there is a problem that variations due to errors between patterns formed using the plurality of photomasks increase.

  The present invention has been made to solve the above problems, and manufactures a photomask capable of reducing errors between patterns formed in a plurality of exposure processes, and an electronic device in which the deviation between patterns is suppressed. An object is to provide a manufacturing method.

  The photomask according to the present invention includes a substrate that transmits first irradiation light and second irradiation light having different wavelength bands, and is laminated on one main surface of the substrate, and has a light shielding property with respect to the first irradiation light. And a first light-shielding layer in which an opening corresponding to a target exposure pattern by the first irradiation light is formed, and is laminated on one main surface of the substrate, and has a light-shielding property against the second irradiation light. And a second light-shielding layer having transparency to the first irradiation light and having an opening corresponding to a target exposure pattern by the second irradiation light. The method for manufacturing an electronic device according to the present invention is performed using the mask.

  According to the present invention, it is possible to form a plurality of patterns, each conventionally formed with a plurality of photomasks, with a single photomask. A plurality of patterns are superimposed on the photomask. When forming a plurality of patterns with separate photomasks, the amount of deviation between the patterns can vary and fluctuate, so it is difficult to control, but the present invention forms a plurality of patterns on the same photomask. It is relatively easy to suppress the mutual shift amount when manufacturing the photomask, and the suppressed state is maintained. Further, since the exposure of a plurality of patterns is performed with the same photomask, the number of times the photomask is set in the exposure apparatus can be reduced, and the influence of the positional deviation when the photomask is set in the exposure apparatus is reduced. be able to. That is, according to the present invention, it is possible to improve the alignment accuracy between a plurality of patterns.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. The photomask of this embodiment is used for a photolithography process of contact holes and trenches of a dual damascene wiring structure. The manufacturing process of the dual damascene wiring structure in this embodiment is basically the same as the process described above with reference to FIGS. 5 and 6 except for the photolithography process. Therefore, the description of the common part uses the above description, and the same components as those shown in FIGS. 5 and 6 are denoted by the same reference numerals in the following description.

  The photomask 60 according to the present invention can switch the exposure pattern for the resist by changing the wavelength of irradiation light used for exposure. By using the photomask 60, for example, exposure is performed with a KrF excimer laser, thereby patterning the photoresist film 10 related to formation of the contact hole 16, and exposure with the i-line (wavelength 365 nm) is performed. Patterning of the photoresist film 20 is performed.

  FIG. 1 shows a case where a photoresist film 10 is formed of a positive resist having photosensitivity to KrF excimer laser and a photoresist film 20 is formed of a positive resist having photosensitivity to i-line. FIG. 1A is a schematic view of a photomask 60 used for patterning, and FIG. 1B shows a cross section taken along line XX ′ in FIG.

  The photomask 60 includes, for example, a substrate 62 made of glass and transmitting a KrF excimer laser and i-line, and a first light shielding layer 64 and a second light shielding layer 66 stacked on one main surface of the substrate 62. Composed. The first light shielding layer 64 is formed of a film having a light shielding property with respect to the i-line. For example, the first light shielding layer 64 is formed of a Cr film. Incidentally, this Cr film has a light shielding property against a KrF excimer laser. The second light shielding layer 66 is formed of a film that has a light shielding property with respect to a KrF excimer laser and is transmissive with respect to i-line. For example, the second light shielding layer 66 can be formed of SOG (Spin on Glass) used selectively as a shifter for the phase shift mask and having transparency selectively to the i-line. In addition, it is preferable that the transmittance | permeability with respect to i line | wire is large, for example, SOG adjustment is performed so that more than half may be permeate | transmitted. The second light shielding layer 66 can also be configured using a dichroic filter.

  In the present embodiment, an opening 68 having a shape corresponding to the pattern of the trench 26 is provided in the first light shielding layer 64. An opening 70 of the second light shielding layer 66 is formed in the opening 68 in a shape corresponding to the pattern of the contact hole 16. In the opening 68, there is a region covered with the second light shielding layer 66, but the second light shielding layer 66 transmits i-line. Therefore, the photoresist is exposed to the i-line using the photomask 60. The film 20 is exposed in the area corresponding to the opening 68. On the other hand, since the KrF excimer laser is blocked by the first light-shielding layer 64 and the second light-shielding layer 66, the photoresist film 10 exposes the region corresponding to the opening 70 by using the photomask 60 and exposing with the KrF excimer laser. Exposed. That is, two types of patterns can be exposed by the photomask 60.

  FIG. 2 is a cross-sectional view showing a manufacturing process of the photomask 60, and shows a vertical cross section of the photomask 60 in the main steps of the manufacturing process. The photomask 60 is manufactured using mask blanks in which the second light shielding layer 66i, the first light shielding layer 64i, and the photoresist film 72 are laminated on the entire surface of the substrate 62 (FIG. 2A).

  The photoresist film 72 is exposed by an electron beam (EB) drawing apparatus and then developed to form an etching mask 72m corresponding to the pattern of the second light shielding layer 66 (FIG. 2B). Using the etching mask 72m, the first light shielding layer 64i and the second light shielding layer 66i are etched (FIG. 2C). Thereby, an opening is formed in the first light shielding layer 64 i and the second light shielding layer 66 i in a portion corresponding to the formation region of the contact hole 16, and the second light shielding layer 66 having the opening 70 is formed.

  After peeling off the photoresist film 72, a photoresist is again applied to the entire surface of the substrate 62 to form a photoresist film 74 (FIG. 2D). The photoresist film 74 is exposed and developed to form an etching mask 74m corresponding to the pattern of the first light shielding layer 64 (FIG. 2E). Using this etching mask 74m, the first light shielding layer 64 is etched (FIG. 2F). This etching is basically performed by a method and conditions in which the second light shielding layer 66 is not etched. As a result, the portion of the first light shielding layer 64 i corresponding to the formation region of the trench 26 is removed, and the first light shielding layer 64 having the opening 68 is formed. Thereafter, the photoresist film 74 is peeled off to complete the photomask 60 shown in FIG.

  Next, a photolithographic process of contact holes and trenches having a dual damascene wiring structure performed using the photomask 60 will be described. FIGS. 3 and 4 are schematic views showing an exposure process in the photolithography process. FIG. 3 shows an exposure process when the contact hole 16 is formed, and FIG. 4 shows an exposure process when the trench 26 is formed. Is shown. 3 and 4 show a cross section of the element, a photomask 60, and exposure light, respectively. In this embodiment, the process shown in FIG. 3 is performed instead of the process shown in FIG. 5B, and the process shown in FIG. 4 is performed instead of the process shown in FIG.

  First, the exposure process at the time of forming the contact hole 16 will be described with reference to FIG. The photomask 60 is set in the exposure apparatus, and the photomask 60 is aligned with the exposure apparatus. As the exposure apparatus, an apparatus capable of irradiating by switching between i-line and KrF excimer laser is used.

  A wafer to be exposed is set in the exposure apparatus. In this wafer, an antireflection film and a photoresist film 10 (not shown) are further formed in this order on the second insulating film 8 shown in FIG. In the present embodiment, as already described, the photoresist film 10 is formed of a positive resist having photosensitivity to a KrF excimer laser.

  This wafer is exposed with a KrF excimer laser 80 using a photomask 60. The KrF excimer laser 80 irradiated to the photomask 60 is blocked by the first light shielding layer 64 and the second light shielding layer 66 and passes only through the opening 70 of the second light shielding layer 66. Thereby, the photoresist film 10 is selectively exposed in a region corresponding to the opening 70. By developing the photoresist film 10, an etching mask for forming the contact hole 16 shown in FIG. 5C is formed.

  A trench 26 is formed after the contact hole 16 is formed. The exposure process when forming the trench 26 will be described with reference to FIG. This exposure process is also performed using the photomask 60. Here, since the same photomask is used, after the exposure process in the contact hole 16, the exposure process of the trench 26 can be performed using the exposure apparatus as it is without removing the photomask 60 from the exposure apparatus. In this way, it is possible to save the trouble of aligning the photomask 60 when the trench 26 is exposed. Further, by performing the exposure process of the contact hole 16 and the exposure process of the trench 26 in a common alignment state, the positional deviation between the contact hole 16 and the trench 26 is suppressed.

  The wafer to be exposed is set in an exposure apparatus in which the photomask 60 has already been set in the exposure process of the contact hole 16. In this wafer, an antireflection film (not shown) and a photoresist film 20 are formed in this order on the second insulating film 8 in which the contact holes 16 are formed. In the present embodiment, as already described, the photoresist film 20 is formed of a positive resist having photosensitivity to i-line.

  The wafer is exposed with i-line 82 using photomask 60. The i-line 82 irradiated to the photomask 60 is blocked by the first light shielding layer 64, but is transmitted through the second light shielding layer 66. That is, the i-line 82 passes through the opening 68 of the first light shielding layer 64 and reaches the wafer. Thereby, the photoresist film 20 is selectively exposed in a region corresponding to the opening 68. By developing the photoresist film 20, an etching mask for forming the trench 26 shown in FIG. 6A is formed.

  Note that the vertical relationship between the first light shielding layer 64 and the second light shielding layer 66 stacked on the substrate 62 of the photomask 60 may be reversed. That is, in the photomask 60, the above-described second light shielding layer 66 having a pattern corresponding to the trench 26 is stacked on the substrate 62, and the above-described first light shielding layer 64 having a pattern corresponding to the contact hole 16 thereon. It can be set as the structure which laminated | stacked.

  In the above embodiment, the first light shielding layer 64 is a Cr film having light shielding properties not only for i-line (first irradiation light) but also for KrF excimer laser (second irradiation light). The layer 64 may transmit the second irradiation light as long as it has a light shielding property with respect to the first irradiation light. This is because transmission of the second irradiation light can be blocked by the second light shielding layer 66.

  In the above embodiment, since the first light shielding layer 64 has light shielding properties not only for the first irradiation light but also for the second irradiation light, the pattern formation position defined by the second light shielding layer 66 is the first position. The light shielding layer 64 was limited to the opening 68. However, if the first light shielding layer 64 is configured to be transmissive to the second irradiation light, the limitation is eliminated, and the exposure pattern by the first light shielding layer 64 and the exposure pattern by the second light shielding layer 66 are the same. It is possible to make the patterns independent of each other. That is, it is possible to perform photolithography with patterns independent of each other with one photomask 60. Also in this case, the alignment accuracy between the two types of patterns can be improved.

  Furthermore, the present invention can be extended to a configuration in which n types of photolithography processes are performed with one photomask. In the photomask, first to nth light shielding layers (n ≧ 3) are stacked on a common substrate 62, and kth light shielding layers (1 ≦ k ≦ n) have first to nth irradiations having different wavelengths. Of the light (n ≧ 3), the light is selectively formed with respect to the k-th irradiation light.

It is the typical top view and sectional view of the photomask concerning the embodiment of the present invention. It is typical sectional drawing of the photomask in the main processes of the manufacturing process of the photomask which concerns on embodiment of this invention. It is a schematic diagram which shows the exposure process in the photolithography process of formation of a contact hole using the photomask which concerns on embodiment of this invention. It is a schematic diagram which shows the exposure process in the photolithography process of formation of a trench using the photomask which concerns on embodiment of this invention. It is a vertical section of an element in the main process of the manufacturing process of a dual damascene wiring structure. It is a vertical section of an element in the main process of the manufacturing process of a dual damascene wiring structure. It is the typical top view and sectional drawing of the conventional photomask. It is the typical top view and sectional drawing of the conventional photomask.

Explanation of symbols

  2 First insulating film, 4 First wiring, 6 Diffusion prevention film, 8 Second insulating film, 10, 20 Photoresist film, 16 contact hole, 18 opening, 26 trench, 30 barrier metal film, 32 copper film, 34 Second wiring, 36 contacts, 60 photomask, 62 substrate, 64, 64i first light shielding layer, 66, 66i second light shielding layer, 68, 70 opening, 72, 74 photoresist film, 72m, 74m etching mask, 80 KrF excimer laser, 82 i-line.

Claims (4)

A substrate that transmits first irradiation light and second irradiation light having different wavelength bands from each other;
A first light-shielding layer that is laminated on one main surface of the substrate, has a light-shielding property with respect to the first irradiation light, and has an opening corresponding to a target exposure pattern by the first irradiation light;
It is laminated on one main surface of the substrate, has a light-shielding property with respect to the second irradiation light, is transmissive with respect to the first irradiation light, and has a target exposure pattern by the second irradiation light. A second light-shielding layer in which a corresponding opening is formed;
A photomask characterized by comprising: The photomask according to claim 1, wherein
The photomask, wherein the first light shielding layer is transmissive to the second irradiation light. A manufacturing method for manufacturing an electronic device using the photomask according to claim 1,
A first photoresist film having photosensitivity to the first irradiation light is formed on a surface of an object forming the electronic device, and the first photoresist film is formed by the first irradiation light using the photomask. A photolithography process to be exposed;
A photolithography step of forming a second photoresist film having photosensitivity to the second irradiation light on the object and exposing the second photoresist film with the second irradiation light using the photomask. When,
The manufacturing method characterized by having. In the manufacturing method of the electronic device according to claim 3,
The photomask is set and aligned in an exposure apparatus that can switch and irradiate the first irradiation light and the second irradiation light,
Performing exposure with each of the first irradiation light and the second irradiation light in each of the photolithography steps using the exposure apparatus that maintains the alignment state of the photomask in the same state;
The manufacturing method characterized by this.

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