JP2010087333A - Photomask, method of manufacturing semiconductor device and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask that can improve characteristics of a semiconductor element, a method of manufacturing a semiconductor device and a semiconductor device. <P>SOLUTION: The method of manufacturing a semiconductor device includes: a step to form a semiconductor film 23 on a substrate 21; a step to form a resist precursor film on the semiconductor film 23; a step where a half-tone mask 11 provided with a light shielding film 14 for shielding an exposure light 15 and a semitransparent film 13 that is provided adjacent to the light shielding film 14 so as to control the intensity of the exposure light 15 and change the exposure light 15 into an exposure light with a different phase is arranged above the resist precursor film, and the exposure light 15 is emitted to the resist precursor film through the half-tone mask 11; a step to develop the resist precursor film so as to form a resist film 25; and a step to treat the semiconductor film 23 by means of the resist film 25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photomask having a gradation difference region, a method for manufacturing a semiconductor device manufactured using the photomask, and a semiconductor device manufactured using the method for manufacturing a semiconductor device.

  In the semiconductor device manufacturing method described above, for example, a semiconductor film is formed on a substrate, and a resist film is formed thereon. Next, as described in Patent Document 1, for example, a resist film is formed in a step shape using a photomask having a gradation difference.

  Specifically, the photomask has a light shielding portion that completely blocks exposure light and a light intensity difference portion that reduces the light intensity. The other region is a transmission region through which light passes. Then, by exposing the resist film using the photomask, for example, a portion corresponding to the channel region (light shielding portion) is formed thick, and a portion corresponding to the source region and drain region (light intensity difference portion) is thin. It is formed.

  Next, the semiconductor film is patterned using the stepped resist film as a mask. Further, using this difference in film thickness of the resist film, impurities are implanted into the source region and the drain region of the semiconductor film.

JP 2006-54424 A

  However, when a step-shaped resist film is formed using a photomask, light leaks from the transmissive region into the semi-transmissive region or is reflected from the periphery into the resist film at the boundary between the semi-transmissive region and the transmissive region. For this reason, the resist film near the boundary is exposed with a light intensity higher than the normal light intensity. Therefore, when the resist film is developed, the resist film at the boundary portion is removed excessively, and the resist film becomes thinner or disappears. That is, the uniformity of the line width and film thickness of the resist film is lowered. As a result, when the semiconductor film is etched using this resist film as a mask, the uniformity of the line width (width from the source region to the drain region) of the semiconductor film is reduced, the etching margin is reduced, and the characteristics of the semiconductor element are reduced. It varies. In addition, there is a problem that the roughness of the pattern edge increases and the breakdown voltage of the semiconductor element decreases due to poor coverage of the insulating film.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A photomask according to this application example is provided adjacent to the light shielding unit that blocks the first light, and controls the intensity of the first light and the first light. And a light intensity difference portion that changes to second light having a phase different from that of the light.

  According to this configuration, when the resist film is exposed through the photomask, the first light transmitted through the transmissive region is at the boundary between the light intensity difference portion of the photomask and the transmissive region that transmits light. Even when the light leaks in the direction of the light, it interferes with (cancels out) the first light and the second light having a different phase difference transmitted through the light intensity difference portion, thereby suppressing light transmission (light intensity Can be weakened). In other words, it is possible to provide a light shielding region having a light shielding function around the light intensity difference portion which is a boundary between the light intensity difference portion and the transmission region. Therefore, it is possible to prevent the resist film at the boundary portion from being excessively removed and become thin or lost, and the uniformity of the line width and film thickness of the resist film can be improved. As a result, when the semiconductor film formed thereunder is patterned using the resist film as a mask, the semiconductor film can be formed in a regular width including a margin, and the characteristics of the semiconductor element can be stabilized. it can. In addition, the roughness of the pattern edge can be reduced, the poor coverage of the insulating film can be suppressed, and the breakdown voltage of the semiconductor element can be ensured. Further, since the line width of the resist film can be formed uniformly, for example, it becomes possible to inject impurities into regular positions of the semiconductor film, and an LDD structure can be formed.

  Application Example 2 A semiconductor device manufacturing method according to this application example is a semiconductor device manufacturing method using the above-described photomask, and includes a step of forming a semiconductor film on a substrate, and a resist on the semiconductor film. A step of forming a precursor film, a step of irradiating the resist precursor film with exposure light through the photomask, a step of developing the resist precursor film to form a resist film, and the resist film And a step of performing a process on the semiconductor film.

  According to this method, when a resist film is formed by irradiating a photomask with exposure light, the resist film has a boundary between the semi-transmissive region and the transmissive region due to the phase difference of the exposure light between the transmissive region and the semi-transmissive region. A resist film thicker than the thickness of the semi-transmissive region can be formed. Therefore, it is possible to prevent the film at the boundary between the transmissive region and the semi-transmissive region in the resist film from being thinned or lost. In the process of processing the semiconductor film, for example, the semiconductor film is etched through the resist film, so that the semiconductor film can be patterned to a regular width and the characteristics of the semiconductor element can be stabilized. Can do. In addition, the roughness of the pattern edge can be reduced, the poor coverage of the insulating film can be suppressed, and the breakdown voltage of the semiconductor element can be ensured.

  Application Example 3 In the method of manufacturing a semiconductor device according to the application example described above, the exposure light is one of the mercury lamp wavelengths 365 nm, 405 nm, and 436 nm, and the excimer laser wavelengths 193 nm and 248 nm. It is preferable that it is composed of two or more combinations.

  According to this method, by using the single wavelength described above, when the photomask is irradiated with the exposure light, the phase of the first light that has passed through the transmissive region and the second light that has passed through the semi-transmissive region. It becomes possible to make it interfere with a phase. Therefore, the intensity of the light irradiating the boundary between the semi-transmissive region and the transmissive region in the resist precursor film can be weakened. Thereby, when forming from a resist precursor film to a resist film, it can prevent that the film of the boundary of the permeation | transmission area | region and semi-transmission area | region in a resist film becomes thin or disappears. In addition, by selecting two or more types of light wavelengths, it is possible to select two types of light with different phase differences, and adjust the amount by which the intensity of light applied to the boundary between the semi-transmissive region and the transmissive region is weakened. be able to.

  Application Example 4 A semiconductor device according to this application example is a semiconductor device manufactured by using the semiconductor device manufacturing method described above, and in the semiconductor film formed on the substrate, the light of the photomask A source region and a drain region into which a high-concentration impurity corresponding to an intensity difference portion is implanted; a channel region corresponding to a light-shielding portion of the photomask in the semiconductor film; and the source region and the photomask in the semiconductor film. The semiconductor device includes a first region formed at a boundary with a transmissive region, and a second region formed at a boundary between the drain region and the transmissive region in the semiconductor film.

  According to this configuration, the first region is formed at the boundary between the source region and the transmission region in the semiconductor film by using the above-described phase difference, and the above-described phase difference is used at the boundary between the drain region and the transmission region. Since the second region is formed, the line width that is the width between the source region and the drain region including the margin can be reliably secured (managed). Therefore, the characteristics of the semiconductor element can be stabilized. In addition, the roughness of the pattern edge can be reduced, the poor coverage of the insulating film can be suppressed, and the breakdown voltage of the semiconductor element can be ensured.

  FIG. 1 is a schematic diagram showing a configuration of a photomask. (A) is a schematic top view, (b) is a schematic cross section along the AA 'line of the photomask shown to (a). Hereinafter, the configuration of the photomask will be described with reference to FIG.

  As shown in FIG. 1, the photomask 11 includes a mask base 12, a semi-transmissive film 13 as a light intensity difference portion that adjusts (controls) the transmittance of exposure light from an exposure apparatus (not shown), And a light-shielding film 14 as a light-shielding part that substantially completely blocks light. Specifically, a halftone mask is used as the photomask 11. Hereinafter, the photomask 11 is referred to as a “halftone mask 11”. The mask substrate 12 is made of a transparent member made of glass or the like.

  The semi-transmissive film 13 is formed on the mask base 12 and is made of, for example, chromium oxide (CrO) or molybdenum silicide (MoSi). The semipermeable membrane 13 can adjust the transmittance (light / darkness) by adjusting the film thickness of chromium oxide, for example. That is, the light intensity can be attenuated by passing light through the semi-transmissive film 13. The thickness of the semipermeable membrane 13 is, for example, 1 to 100 nm.

  For example, in the wavelength of 365 nm, the transmittance of the semi-transmissive film 13 can be set to 50% by setting the film thickness of the tantalum oxide to a predetermined value, and by making the film thickness of the tantalum oxide smaller than the predetermined value. The transmittance of the semipermeable membrane 13 can be made larger than 50%.

  The light shielding film 14 is, for example, a chromium (Cr) film, and is formed on the semi-transmissive film 13. The thickness of the light shielding film 14 is, for example, 200 to 300 nm.

  The light shielding region of the halftone mask 11 is a portion where the semi-transmissive film 13 and the light shielding film 14 overlap. The semi-transmissive region is a portion where the light-shielding film 14 is not present and the semi-transmissive film 13 is exposed. When the halftone mask 11 is irradiated with the exposure light 15a (see FIG. 2) as the first light, the exposure light 15a irradiated to the light shielding film 14 does not pass through the halftone mask 11. The exposure light 15a irradiated to the semi-transmissive film 13 passes through the halftone mask 11 as exposure light 15b as second light whose light intensity is weakened.

  FIG. 2 is a diagram showing the relationship between the photomask portion (position) and light intensity. (A) is a schematic cross section which shows the structure of a photomask. (B) is a graph which shows the relationship between the part of a photomask, and light intensity. Hereinafter, the relationship between the photomask portion and the light intensity will be described with reference to FIG.

  The horizontal direction of the graph shown in FIG. 2B indicates a position corresponding to the portion of the photomask shown in FIG. The vertical direction of the graph is the light intensity of the exposure light 15a, 15b, 15c that has passed through the halftone mask 11, and indicates that the light intensity decreases as it goes downward in the figure.

  The exposure light 15a irradiated to the transmission region of the halftone mask 11 passes through the mask base material 12 which is a transparent member while maintaining the irradiated light intensity. The exposure light 15a irradiated to the semi-transmissive region is adjusted in transmittance by the semi-transmissive film 13, and becomes exposure light 15b having a light intensity lower than that of the exposure light 15a. The exposure light 15 a irradiated to the light shielding region cannot pass through the light shielding film 14. That is, the light intensity is the weakest.

  The light intensity of the exposure light 15c at the boundary 16 between the semi-transmissive region and the transmissive region of the halftone mask 11 is weaker than the light intensity of the exposure light 15b that has passed through the semi-transmissive region (C portion). More specifically, a phenomenon occurs in which the exposure light 15a and 15b leak between the transmissive region and the semi-transmissive region. At this time, in the leaked region, the phase of the exposure light 15a that has passed through the transmissive region and the phase of the exposure light 15b that has passed through the semi-transmissive region are shifted (phase different from the phase of air in the semi-transmissive film 13). By using this film, the phases interfere with each other, and the intensity of the leaked exposure light 15a, 15b is canceled (the intensity of the exposure light 15c is weakened).

  That is, at the boundary 16, the effect of lowering the transmittance can be obtained by the effect of the phase difference. In other words, the same function as the provision of the light shielding film can be produced at the boundary 16. Therefore, a film thicker than the semi-transmissive film can be formed if the light intensity is slightly weaker than the light intensity of the semi-transmissive region at the boundary 16.

  As described above, even when light leakage occurs in the mutual region at the boundary 16 between the transmissive region and the semi-transmissive region, it is possible to weaken the light intensity by utilizing the phase difference. Accordingly, when the resist film is exposed and developed using the halftone mask 11, it is possible to prevent the resist film at the boundary 16 portion from being excessively removed and becoming thinner or lost. As a result, when the semiconductor film is etched using the resist film as a mask, the line width of the semiconductor film can be formed to a regular width, and the characteristics of the semiconductor element can be stabilized. In addition, the roughness of the pattern edge can be reduced, the poor coverage of the insulating film can be suppressed, and the breakdown voltage of the semiconductor element can be ensured.

  FIG. 3 is a chart in which the phase difference and the transmittance are obtained when the thickness and wavelength of the semi-transmissive film are changed. Hereinafter, the phase difference and the transmittance will be described with reference to FIG.

  The chart shown in FIG. 3A shows the phase difference when the wavelength of the exposure light 15a irradiated on the semi-transmissive film 13 and the film thickness of the semi-transmissive film 13 are varied. The semipermeable membrane 13 used here is chromium oxide. The phase difference obtained here is the difference (°) between the phase of the exposure light 15 a that has passed through the portion without the semi-transmissive film 13 (in the air) and the phase of the exposure light 15 b that has passed through the semi-transmissive film 13.

  There are three types of wavelengths λ: 248 nm, 365 nm, and 436 nm. The refractive index n is dependent on the wavelength of light, and is 2.09, 2.40, 2.70 in the order of the wavelength λ. These refractive indexes n are different from the refractive index n of air existing in the transmission region (air refractive index: 1.00). That is, by using a film (for example, chromium oxide) having a refractive index different from the refractive index of air, the phases of the exposure lights 15a and 15b can be shifted in the transmissive region and the semi-transmissive region. There are four types of film thickness d: 25 nm, 50 nm, 75 nm, and 100 nm.

  For example, the phase difference is 40 ° when the wavelength λ is 248 nm and the film thickness d of the semi-transmissive film 13 is 25 nm. The phase difference when the wavelength λ is 436 nm and the film thickness d is 100 nm is 140 °. For example, when the mutual phase is shifted by a half wavelength (180 °), the exposure lights 15a and 15b cancel each other out due to light interference.

  Next, the chart shown in FIG. 3B shows the transmittance T when the wavelength of the exposure light 15a applied to the semi-transmissive film 13 and the film thickness of the semi-transmissive film 13 are varied. The transmittance T obtained here is the ratio (%) of the light intensity of the exposure light 15b after passing through the semi-transmissive film 13 when the light intensity of the exposure light 15a irradiated to the semi-transmissive film 13 is 1.00. It is. The material of the semi-transmissive film 13, the type of wavelength λ (refractive index n) to be used, and the type of film thickness d are the same as in the case of obtaining the above phase difference.

  For example, the transmittance T when the wavelength λ is 248 nm and the film thickness d is 25 nm is 14%. Further, the transmittance T when the wavelength λ is 436 nm and the film thickness d is 100 nm is 7%.

  As described above, by selecting and combining the wavelength λ and the film thickness d, the phase can be shifted and the transmittance T can be secured as shown in the chart. In addition, even if exposure light 15a and 15b leak to each other at the boundary 16 between the transmission region and the semi-transmission region due to the phase difference shown in the chart, the exposure light 15c is utilized by utilizing the difference in phase. It becomes possible to weaken the light intensity. As a result, when the resist film is exposed and developed using the halftone mask 11, it is possible to prevent the resist film at the boundary 16 portion from being excessively removed and becoming thin or lost.

  Further, the wavelength λ of the exposure light 15a includes 365 nm, 405 nm, and 436 nm that are wavelengths of a mercury lamp, and 193 nm and 248 nm that are wavelengths of an excimer laser. Further, two or more wavelengths λ may be used in combination. According to this, the ratio that the wavelength λ (half wavelength) at which the interference exposure light 15c is weakened most can be created increases. In addition, by selecting two or more types of light wavelengths, it is possible to select two types of light with different phase differences, and adjust the amount by which the intensity of light applied to the boundary between the semi-transmissive region and the transmissive region is weakened. be able to.

  4 to 10 are schematic views showing a method of manufacturing a semiconductor device using the photomask in the order of steps. Each of FIGS. 4A to 10A is a schematic plan view, and each of FIGS. 4B to 10B is a schematic cross-sectional view taken along the line BB ′ in each of FIGS. Hereinafter, a method for manufacturing a semiconductor device will be described with reference to FIGS. Note that the semiconductor device of this embodiment is, for example, an n-channel TFT having an LDD structure.

  First, as shown in FIG. 4, a base protective film 22 made of a silicon oxide film or the like is formed on a substrate 21 made of glass or the like by, for example, a plasma CVD (Chemical Vapor Deposition) method. Next, a semiconductor film 23 such as polycrystalline silicon is formed on the entire surface of the base protective film 22. Thereafter, a resist precursor film 24 to be a resist film is formed on the semiconductor film 23. The resist precursor film 24 is, for example, a positive type. This is because the portion of the resist precursor film 24 irradiated in accordance with the exposure light irradiation amount is removed by the development process.

  Next, as shown in FIG. 5, the resist precursor film 24 is patterned into a predetermined shape by a photolithography technique. The photolithography technique performed here uses the above-described halftone mask 11 as a mask for transferring and exposing the resist precursor film 24.

  Specifically, first, the resist precursor film 24 is irradiated with the exposure light 15 a through the halftone mask 11. The wavelength of the exposure light 15a is, for example, 365 nm. The semi-transmissive film 13 of the halftone mask 11 has a thickness of 25 nm, for example. The exposure light 15a applied to the light shielding film 14 of the halftone mask 11 cannot be transmitted and is blocked. Further, the exposure light 15a irradiated to the semi-transmissive film 13 is attenuated (in light of the transmittance), and passes through the exposure light 15b with a light intensity lower than that before transmission (for example, The transmittance is 39%), and the resist precursor film 24 is exposed. The exposure light 15a irradiated to the boundary 16 in the semi-transmissive film 13 becomes exposure light 15c having a light intensity lower than that of the exposure light 15b due to a difference in phase difference (for example, 35 °). Further, the exposure light 15a irradiated to the region other than the light shielding film 14 and the semi-transmissive film 13 passes with the light intensity as it is.

  Then, by developing the exposed resist precursor film 24, a portion 25a corresponding to the light-shielding region where the thickness of the resist precursor film 24 substantially before exposure remains, and the semi-transparent where the resist precursor film 24 remains thin A resist film 25 having a portion 25b corresponding to the region and a portion 25c corresponding to the boundary 16 between the transmissive region and the semi-transmissive region in which more resist precursor film 24 remains than the semi-transmissive region is completed. That is, the step-like resist film 25 is completed. All of the resist precursor film 24 in the transmission region is removed.

  The thickness of the light shielding region in the resist film 25 is, for example, 1 μm. The thickness of the semi-transmissive region in the resist film 25 is, for example, 0.4 μm. The width of the portion 25c of the resist film 25 formed at the boundary between the transmission region and the semi-transmission region is determined by the resolution of the exposure machine, and is, for example, 2 to 3 μm.

  As described above, since the light intensity of the exposure light 15c formed by the mutual interference of the phases is weakened at the boundary 16 between the semi-transmissive film 13 and the transmissive region of the half-tone mask 11, the half-tone mask 11 When the resist film 25 is formed through the step, a portion 25c of the resist film 25 thicker than the portion 25b of the resist film 25 in the semi-transmissive region can be formed. By providing this portion 25c, it is possible to suppress film loss of the resist film 25 due to light leaking from the transmissive region to the semi-transmissive region, and the resist film 25 in the semi-transmissive region can be formed in a regular shape. A uniform film thickness can be formed. As a result, variations in the line width of the semi-transmissive region in the resist film 25 can be suppressed.

  Next, as shown in FIG. 6, the semiconductor film 23 formed under the resist film 25 is etched into a predetermined shape by using the resist film 25 patterned in a step shape as a mask. The semiconductor film 23 is formed in a pattern including a channel region 33, a source region 31, and a drain region 32 that are formed in a later process. As an etching method, various methods such as dry etching or wet etching can be applied.

  Thus, the line width of the resist film 25 is formed to be uniform and a predetermined width, and the semiconductor film 23 is patterned through the resist film 25, so that it is possible to ensure a margin during etching, and the semiconductor The characteristics of the element can be stabilized. Moreover, the roughness of the pattern edge can be reduced, the coverage defect of the insulating film can be suppressed, and the breakdown voltage of the formed semiconductor element 45 (see FIG. 10) can be ensured.

  Specifically, the first region and the portion 34 (see FIG. 7) corresponding to the portion 25c (boundary 16) of the resist film 25 are formed around the source region 31 and the drain region 32. It is possible to provide a margin for the etching process. Furthermore, since the line width of the resist film 25 is formed in a regular shape, a margin can be given to the shape of the semiconductor film 23.

Next, as shown in FIG. 7, with the resist film 25 as a mask, impurity ions (phosphorus ions) 26 having a high concentration with respect to the semiconductor film 23 are, for example, 0.1 × 10 ¹⁵ to 10 × 10 ¹⁵ / Implant with a dose of cm ² . Thereby, in the semi-transmissive region in the resist film 25, the high concentration impurity ions 26 pass through the resist film 25 in a high concentration state and are implanted into the semiconductor film 23.

  As a result, the source region 31 and the drain region 32 are formed in the semiconductor film 23. Further, a region between the source region 31 and the drain region 32 becomes a channel region 33. The semi-transmissive region may be set in advance in consideration of the region of the portion 34 so that the implanted region is not narrowed by the portion 34 of the semiconductor film 23 formed at the boundary 16 between the semi-transmissive region and the transmissive region. desirable.

  As described above, using the resist film 25 as a mask, the source side high concentration region 31 (later source side high concentration region 31a) and the drain side high concentration region 32 (later A drain side high concentration region 32a) can be formed. On the other hand, in the region where the film thickness of the resist film 25 is thick (light-shielding region), since the high-concentration impurity ions 26 are blocked in the region of the resist film 25, the impurity ions 26 reach the region of the semiconductor film 23. do not do. Thus, the region where the impurity ions 26 of a predetermined concentration are not implanted becomes a channel region 33 constituted by the semiconductor film 23 to which no impurity is added. A method in which the etching of the semiconductor film 23 is performed after the implantation of the impurity ions 26 is also preferable.

  Next, as shown in FIG. 8, the resist film 25 formed on the semiconductor film 23 is peeled off, and the entire surface of the substrate 21 including the semiconductor film 23 is formed on the entire surface by a plasma CVD method, a sputtering method, or the like. A gate insulating film 35 made of a silicon oxide film or the like is formed. Thereafter, a conductive film 36a made of, for example, polycrystalline silicon or the like, which becomes the gate electrode 36, is formed on the entire surface of the gate insulating film 35.

  In the process formed so far, the semi-transmissive region of the resist film 25 is thinned. Therefore, when the resist film 25 is removed, the thin semi-transmissive region is lost, and the lower side thereof is removed. There is a possibility that the source region 31 and the drain region 32 of the semiconductor film 23 are thinned to reduce the film thickness. However, when the film thickness of this portion is reduced, an inclination is formed between the periphery. Due to this inclination, when the gate insulating film 35 is formed on the semiconductor film 23, it is possible to maintain the film thickness without breaking the gate insulating film 35. As a result, the breakdown voltage of the semiconductor element 45 is ensured. Can do.

  Next, as shown in FIG. 9, a resist film is formed on the entire surface of the conductive film 36a, and the resist film is exposed and developed by a photolithography technique and patterned into a predetermined shape. The patterned resist film 37 is narrower than the region width of the channel region 33 formed in the lower layer, and the source side low concentration region 31b and the drain side low concentration region 32b (see FIG. 10) at both ends of the channel region 33. Reference) is formed so as to be formed.

Next, as shown in FIG. 10, the conductive film 36 a is etched using the resist film 37 patterned into the predetermined shape as a mask to form the gate electrode 36. Subsequently, low-concentration impurity ions (phosphorus ions) 38 are implanted into the semiconductor film 23 at a dose of, for example, 0.1 × 10 ¹³ to 10 × 10 ¹³ / cm ^{2 using} the gate electrode 36 as a mask. In this way, the source-side low concentration region 31b and the drain-side low concentration region 32b are formed at both ends of the channel region 33 of the semiconductor film 23. In this way, the semiconductor device 41 having a so-called LDD structure is completed.

  FIG. 11 is a schematic plan view specifically showing the configuration of the semiconductor film shown in FIG. Hereinafter, the structure of the semiconductor film will be described with reference to FIG. Note that the schematic plan view shown in FIG. 11 shows the concentration distribution of the impurity implanted into the semiconductor film 23 and shows only the semiconductor film 23.

  As shown in FIG. 11, the semiconductor film 23 includes the channel region 33, the source region 31 (31a, 31b), and the drain region 32 (32a, 32b) as described above.

  The source region 31 and the drain region 32 each have the highest impurity concentration at the substantial center, and the impurity concentration gradually decreases toward the periphery thereof. Specifically, in the halftone mask 11, a portion of the resist film 25 corresponding to a portion where the phase difference between the boundary 16 between the semi-transmissive region and the transmissive region occurs is thickened. When impurities are implanted into the semiconductor film 23 through such a resist film 25, the semiconductor film 23 has a region 42 having the highest impurity concentration, a region 43 having a lower impurity concentration, and a lower impurity concentration. An unimplanted region 44 can be formed.

  That is, as shown in FIG. 11, the impurity concentration region changes from approximately the center of the source region 31 and the drain region 32. Since the impurity concentration is low as it goes around the source region 31 and the drain region 32, after forming the gate electrode 36, the source side low concentration region 31b and the drain side low concentration region are formed at both ends of the channel region 33 of the LDD structure. 32b can be formed. That is, it is possible to prevent the channel region 33 and the high concentration regions 31a and 32a from coming into contact with each other, and the function as the LDD structure can be achieved without performing low concentration impurity ion implantation separately.

  As described above in detail, according to the present embodiment, the following effects can be obtained.

  (1) According to the present embodiment, since a phase difference occurs at the boundary 16 between the semi-transmissive film 13 and the transmissive region in the halftone mask 11, when the resist precursor film 24 is exposed through the half-tone mask 11, Even if light leaks in the direction from the transmissive region to the semi-transmissive region, the light intensity of the exposure light 15c can be weakened (cancelled) at the boundary 16 portion between the semi-transmissive film 13 and the transmissive region. In other words, extra light can be prevented from entering the impurity-implanted region of the semi-transmissive region in the resist film 25. Therefore, the portion 25b of the resist film 25 corresponding to the semi-transmissive region can be exposed without changing the light intensity, and can be patterned to a line width of a regular width. Also, the line width can be managed. As a result, when the semiconductor film 23 formed thereunder is patterned using the resist film 25 as a mask, the semiconductor film 23 can be formed in a regular width including a margin, and the characteristics of the semiconductor element 45 can be stabilized. It can be made. In addition, the roughness of the pattern edge can be reduced, the poor coverage of the insulating film can be suppressed, and the breakdown voltage of the semiconductor element 45 can be ensured.

  (2) According to the present embodiment, since the boundary 16 between the transmission region and the semi-transmission region in the halftone mask 11 becomes a phase difference generation region, the resist precursor film 24 is exposed through the halftone mask 11. In this case, it is possible to prevent the film thickness around the resist film 25 in the semi-transmissive region from becoming thin. Therefore, for example, a predetermined amount of impurities can be implanted into a regular position of the semiconductor film 23, and an LDD structure can be formed.

  (3) According to the present embodiment, the portion 34 corresponding to the light-shielding region is formed around the semi-transmissive region in the resist film 25. Therefore, when the semiconductor film 23 is etched using the resist film 25 as a mask, a margin is provided. Can be patterned. Therefore, the withstand voltage and line width uniformity of the semiconductor element 45 can be ensured.

  (4) According to this embodiment, the halftone mask 11 generally used in semiconductor manufacturing is used. Therefore, since a special mask configuration is not used, the halftone mask 11 can be completed by using a general photomask defect inspection and repair technique.

  In addition, embodiment is not limited above, It can also implement with the following forms.

(Modification 1)
As described above, the half-tone mask 11 is not limited to the configuration in which the semi-transmissive film 13 is disposed on both sides with the light-shielding film 14 interposed therebetween. The semi-permeable membrane 13 may be disposed at the boundary between 14 and the transmissive region. According to this, even if the exposure light 15a enters a certain area of the light shielding film 14 from the transmission region, the intensity of the exposure light 15a can be weakened because the semi-transmissive film 13 exists at the boundary portion. Therefore, when the resist film is formed, it is possible to prevent the side wall of the resist film corresponding to the light shielding film 14 from being excessively shaved. Therefore, the semiconductor film 23 having a regular width can be obtained.

It is a schematic diagram which shows the structure of the photomask which concerns on this embodiment, (a) is a schematic plan view, (b) is a schematic cross section along the AA 'line of (a). It is a figure which shows the relationship between the part of a photomask, and light intensity, (a) is a schematic cross section which shows the structure of a photomask, (b) is a graph which shows the relationship between the part of a photomask, and light intensity. The figure which calculated | required the phase difference and the transmittance | permeability at the time of changing the film thickness and wavelength of a semi-permeable film. It is a schematic diagram which shows the manufacturing method of a semiconductor device in order of a process, (a) is a schematic top view, (b) is a schematic cross section along the BB 'line | wire of (a). It is a schematic diagram which shows the manufacturing method of a semiconductor device in order of a process, (a) is a schematic top view, (b) is a schematic cross section along the BB 'line | wire of (a). It is a schematic diagram which shows the manufacturing method of a semiconductor device in order of a process, (a) is a schematic top view, (b) is a schematic cross section along the BB 'line | wire of (a). It is a schematic diagram which shows the manufacturing method of a semiconductor device in order of a process, (a) is a schematic top view, (b) is a schematic cross section along the BB 'line | wire of (a). It is a schematic diagram which shows the manufacturing method of a semiconductor device in order of a process, (a) is a schematic top view, (b) is a schematic cross section along the BB 'line | wire of (a). It is a schematic diagram which shows the manufacturing method of a semiconductor device in order of a process, (a) is a schematic top view, (b) is a schematic cross section along the BB 'line | wire of (a). It is a schematic diagram which shows the manufacturing method of a semiconductor device in order of a process, (a) is a schematic top view, (b) is a schematic cross section along the BB 'line | wire of (a). The schematic plan view which shows the structure of a semiconductor film concretely. It is a schematic diagram which shows the modification of a photomask, (a) is a schematic plan view, (b) is a schematic cross section along the AA 'line of (a).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Halftone mask (photomask), 12 ... Mask base material, 13 ... Semi-transmissive film as light intensity difference part, 14 ... Light shielding film as light shielding part, 15 ... Exposure light as 1st light, 16 ... Boundary, 21 ... substrate, 22 ... underlying protective film, 23 ... semiconductor film, 24 ... resist precursor film, 25 ... resist film, 25a, 25b, 25c ... part, 26,38 ... impurity ions, 31 ... source region, 31a ... high concentration region on the source side, 31b ... low concentration region on the source side, 32 ... drain region, 32a ... high concentration region on the drain side, 32b ... low concentration region on the drain side, 33 ... channel region, 34 ... part, 35 ... gate insulating film , 36 ... gate electrode, 36a ... conductive film, 37 ... resist film, 41 ... semiconductor device, 42, 43, 44 ... region, 45 ... semiconductor element.

Claims (4)

A light blocking portion for blocking the first light;
A light intensity difference portion that is provided adjacent to the light shielding portion, controls the intensity of the first light, and changes it to second light having a phase different from that of the first light;
A photomask comprising: A method of manufacturing a semiconductor device using the photomask according to claim 1,
Forming a semiconductor film on the substrate;
Forming a resist precursor film on the semiconductor film;
Irradiating the resist precursor film with exposure light through the photomask;
Developing the resist precursor film to form a resist film;
Processing the semiconductor film through the resist film;
A method for manufacturing a semiconductor device, comprising: A method of manufacturing a semiconductor device according to claim 2,
The exposure light is composed of one or a combination of two or more of 365 nm, 405 nm and 436 nm which are wavelengths of a mercury lamp, and 193 nm and 248 nm which are wavelengths of an excimer laser. Production method. A semiconductor device manufactured using the method for manufacturing a semiconductor device according to claim 2 or 3,
In a semiconductor film formed on a substrate, a source region and a drain region into which a high concentration impurity corresponding to a light intensity difference portion of the photomask is implanted,
A channel region corresponding to a light shielding portion of the photomask in the semiconductor film;
A first region formed at a boundary between the source region in the semiconductor film and a transmission region in the photomask;
A second region formed at a boundary between the drain region and the transmission region in the semiconductor film;
A semiconductor device comprising:

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