JP2005191060A - Exposure apparatus and exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure apparatus and an exposure method capable of easily correcting subtle illuminance unevenness while minimizing a decrease in light source efficiency.
An exposure apparatus 1 includes a second illumination optical system 70 together with a first illumination optical system 10, and the first illumination optical system 10 has a first illumination optical system 10 according to an illuminance distribution of light emitted from the first illumination optical system 10. The liquid crystal shutter 71 of the second illumination optical system 70 is set to a gradation in which the transmittance corresponding to the darker position is higher. The light emitted from the first illumination optical system 10 and the light emitted from the second illumination optical system 70 are combined by the half mirror 20 and irradiated onto the reticle 30. Further, the light transmitted through the reticle 30 passes through the projection optical system 40 and is irradiated onto the semiconductor wafer W placed on the stage 50, and exposure according to the exposure pattern formed on the reticle 30 is performed.
[Selection] Figure 1

Description

  The present invention relates to an exposure apparatus and an exposure method for performing exposure by irradiating an exposure object with light emitted from an illumination optical system through a photomask.

  In recent years, in order to cope with high integration and miniaturization of semiconductor devices, in an exposure apparatus used in a lithography process in the manufacture of semiconductor wafers, the illuminance distribution of exposure light is made uniform and the line width uniformity is improved. Is required.

  Usually, in order to uniformize the illuminance distribution of the exposure light on the surface of the semiconductor wafer, a method of interposing a filter (light control filter) having a transmittance distribution according to the illuminance distribution of the exposure light in the optical path is used. ing.

  However, since the illuminance distribution of the exposure apparatus is also affected by variations in each optical element in the apparatus, it is necessary to manufacture a unique filter for each apparatus in order to further improve the uniformity of the illuminance distribution. . In addition, when an illuminance change with time occurs, such as cloudiness of each optical element due to the use environment, etc., it is necessary to frequently clean the optical element.

  On the other hand, a proposal has been made in which a transmittance distribution can be controlled using a liquid crystal shutter as a dimming filter (for example, Patent Document 1). According to this, it is possible to deal with variations among devices and changes in illuminance over time by electrical control.

Japanese Patent Laid-Open No. 7-92783

  As shown in Patent Document 1, in the case of using a method in which a liquid crystal shutter is directly provided in the optical path, a slight cloudiness of an optical element or the like provided in the optical path is obtained only by turning on (transmitting) and turning off (shielding) the liquid crystal shutter. It is difficult to correct subtle illuminance unevenness caused by the above, and correction by controlling the gradation of the liquid crystal, that is, the transmittance is required. However, even if it is possible to control the gradation between transmission and light shielding at substantially equal intervals, the light source efficiency is extremely reduced at lower gradations with low transmittance. Will be limited. For example, even when a liquid crystal shutter of about 8 gradations is used, if it is attempted to minimize the decrease in light source efficiency, correction can be made only with the upper 3 gradations having a high transmittance. Therefore, in order to correct more subtle illuminance unevenness, it is necessary to use a liquid crystal shutter capable of multi-level gradation control, or to control the transmission time for each dot according to the illuminance unevenness. However, for this purpose, there are problems that the cost required for the liquid crystal shutter is increased and the control becomes complicated.

  The present invention has been made in view of the above problems, and an object thereof is to provide an exposure apparatus and an exposure method capable of easily correcting subtle illuminance unevenness while minimizing a decrease in light source efficiency. There is.

  An exposure apparatus according to the present invention is an exposure apparatus that performs exposure by irradiating an object to be exposed with light emitted from an illumination optical system through a photomask, the first illumination optical system, and an illuminance distribution in the exposure region. In accordance with the second illumination optical system capable of adjusting the illuminance distribution of the emitted light, the light emitted from the first illumination optical system, and the light emitted from the second illumination optical system. A light synthesizing unit that synthesizes the light, and the light synthesized by the light synthesizing unit is irradiated onto an exposure object through a photomask.

  According to this, since the second illumination optical system capable of adjusting the illuminance distribution of the emitted light according to the illuminance distribution in the exposure region is provided separately from the first illumination optical system, In the optical path of the illumination optical system, it is not necessary to provide a light control filter or the like for correcting illuminance unevenness. Furthermore, since the second illumination optical system only needs a light amount that compensates for the difference in illuminance between the highest illuminance portion and the lowest illuminance portion in the exposure area, for example, the light source output is reduced to 0 according to the illuminance distribution in the exposure area. Even when an illumination optical system that can be selected from a plurality of levels set at equal intervals between% and 100% is used, many levels are obtained without reducing the light source efficiency as compared with the case where there is only one illumination optical system. Thus, it is possible to correct the uneven illuminance.

  In this exposure apparatus, the first and second illumination optical systems emit light having coherency, light emitted from the first illumination optical system, and light emitted from the second illumination optical system. The light may be in phase with the light combining unit.

  According to this, since the phases of the light emitted from the first illumination optical system and the light emitted from the second illumination optical system match, the exposure light is light having coherency. Even if it exists, it becomes possible to supplement light quantity with respect to the area | region where illumination intensity is insufficient, without mutually canceling out light, and it becomes possible to make illumination intensity distribution uniform.

  In this exposure apparatus, the first and second illumination optical systems emit light having coherency, light emitted from the first illumination optical system, and light emitted from the second illumination optical system. The light may be 180 degrees out of phase with the light combining unit.

  According to this, since the light emitted from the first illumination optical system and the light emitted from the second illumination optical system are 180 ° out of phase, the exposure light has coherency. Even so, it is possible to cancel out the amount of light in the region where the illuminance exceeds without enhancing each other's light, and the illuminance distribution can be made uniform.

  In this exposure apparatus, the first and second illumination optical systems emit light having coherency, light emitted from the first illumination optical system, and light emitted from the second illumination optical system. There may be provided a phase adjusting unit capable of adjusting a phase shift in the light combining unit with the light.

  According to this, the phase adjustment unit can adjust the phase shift between the light emitted from the first illumination optical system and the light emitted from the second illumination optical system. It is possible to easily shift the phase by 180 °. As a result, even when exposure light having coherency is used, it becomes easy to make the illuminance distribution uniform.

  An exposure apparatus according to the present invention is an exposure apparatus that performs exposure by irradiating an exposure object with light emitted from an illumination optical system through a photomask, and divides the optical path of the light emitted from the illumination optical system into two branches A light branching unit that is provided, and a dimming unit that is provided in one of the two branched light paths and that can adjust a light transmittance distribution according to an illuminance distribution in an exposure region, and the two branched light beams. A light synthesizing unit for synthesizing the optical paths, and irradiating the exposure object with the light synthesized by the light synthesizing unit through a photomask.

  According to this, since the light emitted from the illumination optical system is branched into two and the light adjustment part capable of adjusting the light transmittance distribution is provided in one of the optical paths, for example, the transmittance is reduced to 0%. When using a dimming unit that can be selected from a plurality of levels set at equal intervals between 100% and 100%, correction is made at many levels without reducing the light source efficiency compared to the case where the optical path is not branched. This makes it possible to correct subtle illuminance unevenness.

  The exposure apparatus of the present invention is an exposure apparatus that performs exposure by irradiating an exposure object with light emitted from an illumination optical system through a photomask, and is emitted from the illumination optical system and transmitted through the photomask. A light branching unit that splits the optical path of light into two, and a light control unit that is provided in one of the two branched optical paths and that can adjust the light transmittance distribution according to the illuminance distribution in the exposure region And a light combining unit that combines the two branched light paths, and irradiates the exposure object with the light combined by the light combining unit.

  According to this, since the light emitted from the illumination optical system and transmitted through the photomask is bifurcated, and one of the optical paths is provided with a light control unit capable of adjusting the light transmittance distribution, for example, transmission When using a dimming unit that can be selected from a plurality of levels set at equal intervals between 0% and 100%, the light source efficiency is reduced as compared with the case where the optical path is not branched. Corrections can be made at many levels, and subtle illumination unevenness can be corrected.

  In the exposure method of the present invention, the illuminance distribution of the light emitted from the first illumination optical system is measured by the illuminance sensor, and the second illumination optical system according to the illuminance distribution measured by the illuminance sensor. After the illuminance unevenness correcting step including adjusting the illuminance distribution of the light emitted from the light, the light emitted from the first illumination optical system is combined with the light emitted from the second illumination optical system And irradiating the object to be exposed.

  According to this, since the second illumination optical system capable of adjusting the illuminance distribution of the emitted light according to the illuminance distribution in the exposure region is provided separately from the first illumination optical system, In the optical path of the illumination optical system, it is not necessary to provide a light control filter or the like for correcting illuminance unevenness. Furthermore, since the second illumination optical system only needs a light amount that compensates for the difference in illuminance between the highest illuminance portion and the lowest illuminance portion in the exposure area, for example, the light source output is reduced to 0 according to the illuminance distribution in the exposure area. Even when an illumination optical system that can be selected from a plurality of levels set at equal intervals between% and 100% is used, many levels are obtained without reducing the light source efficiency as compared with the case where there is only one illumination optical system. Thus, it is possible to correct the uneven illuminance.

  The exposure method of the present invention includes a step of measuring an illuminance distribution of light emitted from the first illumination optical system and the second illumination optical system and synthesized, and an illuminance distribution measured by the illuminance sensor. And adjusting the illuminance unevenness correction step of adjusting the illuminance distribution of the light emitted from the second illumination optical system, and the light emitted from the first illumination optical system and the second illumination. The light emitted from the optical system is synthesized by a light synthesis unit and irradiated to an exposure object.

  According to this, the same effect as the effect by the exposure method can be obtained. Furthermore, according to this, the illuminance distribution of the light obtained by combining the light emitted from the first illumination optical system and the light emitted from the second illumination optical system is measured, and the illuminance unevenness is detected. Therefore, it is possible to correct in advance the illuminance unevenness caused by the second illumination optical system, and it is possible to easily correct the illuminance unevenness.

  In this exposure method, the first and second illumination optical systems emit light having coherency, the light emitted from the first illumination optical system, and the second illumination optical system. The light may be in phase with the light combining unit.

  According to this, since the phases of the light emitted from the first illumination optical system and the light emitted from the second illumination optical system match, the exposure light is light having coherency. Even if it exists, it becomes possible to supplement light quantity with respect to the area | region where illumination intensity is insufficient, without mutually canceling out light, and it becomes possible to make illumination intensity distribution uniform.

  In this exposure method, the first and second illumination optical systems emit light having coherency, the light emitted from the first illumination optical system, and the second illumination optical system. The light may be 180 degrees out of phase with the light combining unit.

  According to this, since the light emitted from the first illumination optical system and the light emitted from the second illumination optical system are 180 ° out of phase, the exposure light has coherency. Even so, it is possible to cancel out the amount of light in the region where the illuminance exceeds without enhancing each other's light, and the illuminance distribution can be made uniform.

  In this exposure method, the first and second illumination optical systems emit light having coherency, and the illuminance unevenness correction step further includes the light emitted from the first illumination optical system, You may have the step which adjusts the shift | offset | difference of the phase in the said light synthetic | combination part with the light radiate | emitted from the 2nd illumination optical system.

  According to this, the phase shift between the light emitted from the first illumination optical system and the light emitted from the second illumination optical system can be adjusted. It is possible to easily shift it. As a result, even when exposure light having coherency is used, it becomes easy to make the illuminance distribution uniform.

  The exposure method of the present invention can adjust the light transmittance distribution according to the step of measuring the illuminance distribution of the light emitted from the illumination optical system with an illuminance sensor and the illuminance distribution measured by the illuminance sensor. And a step of branching the optical path of the light emitted from the illumination optical system after the illuminance unevenness correcting step including the step of controlling the light control unit, and one of the two branched optical paths. A light combining unit that combines light transmitted through the light control unit and light transmitted through the other optical path, and irradiates the exposure target with the light combined by the light combining unit through a photomask. It is characterized by doing.

  According to this, since the light emitted from the illumination optical system is branched into two and the light adjusting portion capable of adjusting the light transmittance distribution is provided in one of the optical paths, for example, the transmittance is set to 0%. When using a dimming unit that can be selected from a plurality of levels set at equal intervals between 100% and 100%, correction is made at many levels without reducing the light source efficiency compared to the case where the optical path is not branched. This makes it possible to correct subtle illuminance unevenness.

  The exposure method of the present invention can adjust the light transmittance distribution according to the step of measuring the illuminance distribution of the light emitted from the illumination optical system with an illuminance sensor and the illuminance distribution measured by the illuminance sensor. And a step of branching an optical path of light emitted from the illumination optical system and transmitted through a photomask after one of the illuminance unevenness correcting steps including the step of controlling the light control unit, and one of the two branched optical paths And combining the light transmitted through the dimming unit provided in the optical path and the light passing through the other optical path in a light combining unit, and the light combined in the light combining unit is passed through a photomask. The exposure object is irradiated.

  According to this, since the light emitted from the illumination optical system and transmitted through the photomask is bifurcated, and one of the optical paths is provided with a light control unit capable of adjusting the light transmittance distribution, for example, transmission When using a dimming unit that can be selected from a plurality of levels set at equal intervals between 0% and 100%, the light source efficiency is reduced as compared with the case where the optical path is not branched. Corrections can be made at many levels, and subtle illumination unevenness can be corrected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the embodiment shown below does not limit the content of the invention described in the claim at all. Further, all of the configurations shown below are not necessarily essential as means for solving the invention described in the claims.

(First embodiment)
An exposure apparatus according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing a schematic configuration of an exposure apparatus in the present embodiment. FIG. 2 (a) is a front view of a liquid crystal shutter, and FIG. 2 (b) is an enlarged view of a main part thereof.

  As shown in FIG. 1, the exposure apparatus 1 includes a first illumination optical system 10 including a light source that emits exposure light having coherency, such as a KrF excimer laser or an ArF excimer laser. The exposure light emitted from the illumination optical system 10 passes through the half mirror 20 and is irradiated onto a reticle 30 as a photomask on which an exposure pattern is formed. Further, the light transmitted through the reticle 30 passes through the projection optical system 40 and is irradiated onto the semiconductor wafer W as an exposure target provided on the stage 50, and is formed on the reticle 30 in a predetermined exposure region. Exposure according to the exposure pattern is performed. An illuminance sensor 60 is provided on the stage 50 so that the illuminance distribution in the exposure area can be detected. Here, the light receiving surface of the illuminance sensor 60 is set to the same height as the surface of the semiconductor wafer W.

  On the other hand, the exposure apparatus 1 includes a second illumination optical system 70. The second illumination optical system 70 includes a light source that emits the same type of light as the first illumination optical system 10, and includes a liquid crystal shutter 71 on the output side thereof. In the liquid crystal shutter 71, as shown in FIGS. 2A and 2B, a plurality of dots 71a are arranged in a matrix, and gradation display is possible in units of dots. In other words, the liquid crystal shutter 71 can transmit light with a transmittance distribution corresponding to the gradation of each dot.

  Returning to FIG. 1, the light emitted from the second illumination optical system 70 is combined with the light emitted from the first illumination optical system 10 by the half mirror 20 as a light combining unit, and the reticle 30 and the projection optics are combined. The semiconductor wafer W is irradiated via the system 40.

  In addition, the exposure apparatus 1 includes an illumination optical system drive unit 81 as a phase adjustment unit so that the position of the second illumination optical system 70 can be finely adjusted in a direction toward or away from the half mirror 20. It has become.

  Further, the exposure apparatus 1 is provided with a control unit 80, for example, according to the control of the light source intensity and exposure time of each illumination optical system 10, 70 or the illuminance distribution obtained by the illuminance sensor 60. It controls the operation of the entire apparatus and sets the state, such as controlling the gradation of the liquid crystal shutter 71 for each dot.

Next, the operation of the exposure apparatus 1 will be described.
First, before the exposure is started, illuminance unevenness correction of the exposure light is performed in a state where the reticle 30 and the semiconductor wafer W are not arranged. After setting the light source output of the first illumination optical system 10 to a predetermined value, the control unit 80 drives the stage 50 and moves the stage 50 to a position where the illuminance sensor 60 is irradiated with the exposure light. Then, the illuminance sensor 60 measures the illuminance distribution in the exposure area. Next, the control unit 80 sets the maximum light source output of the second illumination optical system 70 according to the measured illuminance distribution. The maximum light source output at this time is such that the darkest part in the exposure area can be compensated for with desired illuminance. Furthermore, the control unit 80 controls the gradation of the liquid crystal shutter 71 according to the measured illuminance distribution. Here, the setting is made for each dot so that the darker region in the exposure region has a gradation with higher transmittance. Thereby, the illuminance distribution by the light emitted from the second illumination optical system 70 is adjusted according to the illuminance distribution in the exposure region. Thereafter, light is emitted from the second illumination optical system 70 toward the half mirror 20. The emitted light is reflected by the half mirror 20 and combined with the light emitted from the first illumination optical system 10.

  Here, since the light source used in the present embodiment is coherent light, the light emitted from the first illumination optical system and the light emitted from the second illumination optical system are phase-shifted. If they match, the combined light increases the illuminance, and if the phase is shifted by 180 °, the combined light cancels and the illuminance decreases. Therefore, the control unit 80 controls the illumination optical system driving unit 81 while measuring the illuminance with the illuminance sensor 60, and moves the position of the second illumination optical system 70 closer to or away from the half mirror 20. The driving is stopped at the position where the illuminance is highest, that is, the position where the phases match, and the position of the second illumination optical system 70 is determined.

  By the above operation, it is possible to reduce the illuminance unevenness of the exposure apparatus 1 and obtain a uniform illuminance distribution. However, actually, the illuminance distribution is caused by the illuminance unevenness caused by the second illumination optical system 70 and the like. It may not be uniform enough. In that case, by controlling the gradation of the liquid crystal shutter 71 while measuring the illuminance with the illuminance sensor 60, it becomes possible to approximate a more uniform illuminance distribution.

  After the above illuminance unevenness correction is completed, the reticle 30 and the semiconductor wafer W are arranged and actual exposure is performed. Note that once the illuminance unevenness correction is performed, it is possible to perform exposure without correcting for a long period of time. However, when the exposure apparatus 1 is in an atmosphere containing, for example, ammonia, the optical element or the like is subjected to ammonium sulfate. May adhere and the illuminance distribution (illuminance unevenness) may change. In this case, by performing the above-described illuminance unevenness correction again, it is possible to continue the exposure without disassembling the exposure apparatus 1 and cleaning the optical elements and the like.

  Next, a specific example of the above-described illuminance unevenness correction operation will be described with reference to FIG. 3A and 3B are diagrams showing the state of illuminance unevenness correction. FIG. 3A is an illuminance distribution before illuminance unevenness correction, FIG. 3B is a gradation distribution of the liquid crystal shutter 71, and FIG. These are figures which show the illumination distribution after illumination unevenness correction | amendment. It is assumed that the liquid crystal shutter 71 can set a transmittance of 8 gradations at substantially equal intervals.

  As shown in FIG. 3A, the illuminance distribution on the straight line in the exposure area by the first illumination optical system 10 has a desired illuminance at the center, but both ends are dark, When the distribution is such that the desired illuminance is not obtained, the maximum light source output of the second illumination optical system 70 is set to the illuminance difference between the maximum illuminance and the minimum illuminance in the exposure area, and the second illumination optical system As shown in FIG. 3B, the liquid crystal shutter 71 of 70 is set to a gradation having higher transmittance for dots corresponding to dark positions. As a result, the illuminance distribution by the light synthesized from the light emitted from the first illumination optical system 10 and the light emitted from the second illumination optical system 70 is all as shown in FIG. The desired illuminance is reached in the exposure area, and a substantially uniform illuminance distribution is obtained.

  Here, when the second illumination optical system 70 is not provided and the liquid crystal shutter 71 is provided in the optical path of the light emitted from the first illumination optical system 10 as in the prior art, the illuminance is changed from 0 to a desired illuminance. However, in this embodiment, the difference between the maximum illuminance of the illuminance distribution by the first illumination optical system 10 and the illuminance difference between the minimum illuminances is corrected by eight equally. Will be able to.

  As described above, according to the exposure apparatus 1 and the exposure method of the present embodiment, the following effects can be obtained.

  (1) According to the present embodiment, apart from the first illumination optical system 10, the second illumination optical system 70 capable of adjusting the illuminance distribution of emitted light according to the illuminance distribution in the exposure region is provided. Therefore, it is not necessary to provide a dimming filter or the like for correcting illuminance unevenness in the optical path of the first illumination optical system 10. Furthermore, since the second illumination optical system 70 only needs a light amount that compensates for the illuminance difference between the highest illuminance portion and the lowest illuminance portion in the exposure area, for example, the light source output is output according to the illuminance distribution in the exposure area. Even when an illumination optical system that can be selected from a plurality of levels set at equal intervals between 0% and 100% is used, the light source efficiency is reduced as compared with the case where there is only one illumination optical system. It is possible to correct by level, and it is possible to correct subtle illuminance unevenness.

  (2) According to the present embodiment, the light emitted from the first illumination optical system 10 and the light emitted from the second illumination optical system 70 are in phase, so that the exposure light Even if the light has coherency, the light intensity can be compensated for an area where the illuminance is insufficient without canceling each other's light, and the illuminance distribution can be made uniform.

  (3) According to the present embodiment, the light emitted from the first illumination optical system 10 and the light emitted from the second illumination optical system 70 by the illumination optical system drive unit 81 as the phase adjustment unit. Therefore, it becomes easy to match the phases of the two lights. As a result, even when exposure light having coherency is used, it becomes easy to make the illuminance distribution uniform.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted. FIG. 4 is a schematic diagram showing a schematic configuration of an exposure apparatus according to the second embodiment.

  As shown in FIG. 4, the light emitted from the illumination optical system 11 is bifurcated into an optical path A and an optical path B by a half mirror 21 as an optical branching unit. The light in the optical path A is reflected by the reflection mirror 22, and further reflected by the half mirror 24 toward the reticle 30.

  On the other hand, the light in the optical path B is reflected by the reflection mirror 23, then dimmed by the liquid crystal shutter 72 as a dimming unit, and synthesized with the light in the optical path A by the half mirror 24 as a light synthesizing unit. The synthesized light is irradiated onto a reticle 30 as a photomask, and the light transmitted through the reticle 30 is irradiated onto a semiconductor wafer W as an exposure object provided on a stage 50 through a projection optical system 40. Is done.

  In addition, the exposure apparatus 1 includes a control unit 80, for example, a liquid crystal shutter according to the control of the light source intensity and exposure time of the illumination optical system 11 or the illuminance distribution obtained by the illuminance sensor 60. It controls the overall operation of the apparatus and sets the state, such as controlling the gradation of 72 for each dot.

Next, the operation of the exposure apparatus 1 will be described.
First, before the exposure is started, illuminance unevenness correction of exposure light is performed in a state where the reticle 30, the semiconductor wafer W, and the liquid crystal shutter 72 are not arranged in the optical path. After setting the light source output of the illumination optical system 11 to a desired value, the control unit 80 drives the stage 50 and moves the stage 50 to a position where the illuminance sensor 60 is irradiated with the exposure light. Then, the illuminance sensor 60 measures the illuminance distribution in the exposure area. Next, the liquid crystal shutter 72 is disposed in the optical path B, and the control unit 80 controls the gradation of the liquid crystal shutter 72 for each dot according to the measured illuminance distribution. Here, the setting is made for each dot so that the darker region in the exposure region has a gradation with higher transmittance. That is, the exposure apparatus 1 of the present embodiment divides the light emitted from the illumination optical system 11 into two parts, corrects uneven illuminance in one optical path B, and combines it with the light in the other optical path A that is not corrected. By doing so, the illuminance becomes uniform.

  With the above operation, it is possible to reduce the illuminance unevenness of the exposure apparatus 1 and obtain a uniform illuminance distribution. However, in actuality, the illuminance distribution is not sufficiently uniform due to the illuminance unevenness caused by each optical path. There is. In that case, by controlling the gradation of the liquid crystal shutter 72 while measuring the illuminance with the illuminance sensor 60, it becomes possible to approximate a more uniform illuminance distribution.

  After the above illuminance unevenness correction is completed, the reticle 30 and the semiconductor wafer W are arranged and actual exposure is performed. As shown in FIG. 4, the position where the reticle 30 is arranged is not limited to the position after the half mirror 24 as the light combining section, and the reticle 30 is positioned at the position indicated by the two-dot chain line in front of the half mirror 21 as the light branching section. 30 may be arranged.

  Next, a specific example of the illuminance unevenness correction operation of the present embodiment will be described with reference to FIG. 5A and 5B are diagrams showing the state of illuminance unevenness correction. FIG. 5A is an illuminance distribution before illuminance unevenness correction, FIG. 5B is an illuminance distribution after light splitting, and FIG. The gradation distribution of the liquid crystal shutter 72, FIG. 5D shows the illuminance distribution after passing through the liquid crystal shutter 72, and FIG. 5E shows the illuminance distribution after illuminance unevenness correction.

  In a state where there is no liquid crystal shutter 72 in the optical path B, the illuminance distribution on a certain straight line in the exposure area is an illuminance distribution that descends to the left as shown in FIG. 5A, and the illuminance at the highest illuminance portion (position Y). Suppose that the illuminance of the lowest illuminance part (position X) is 70, where is 100. On the other hand, the illuminance distribution of the optical path A and the optical path B is bifurcated into the optical path A and the optical path B by the half mirror 21, and the illuminance at the position Y is 50 as shown in FIG. Assume that the illuminance at position X is 35.

  Next, the liquid crystal shutter 72 is disposed, and correction according to the illuminance distribution is performed. The light in the optical path A reaches the half mirror 24 with this distribution, but the distribution of the light in the optical path B is adjusted by the liquid crystal shutter 72. Here, for the sake of simplicity, the liquid crystal shutter 72 can adjust the transmittance of 8 gradations at substantially equal intervals between 0% and 100% of the transmittance, including 0% and 100%. Then, as shown in FIG. 5C, the transmittance of the dot corresponding to the lowest illuminance portion (position X) is set to 100%, and the transmittance of the dot corresponding to the highest illuminance portion (position Y) is about Set to 40%. Then, as shown in FIG. 5D, the illuminance distribution by only the light transmitted through the liquid crystal shutter 72 has an illuminance at the position X of 35 and an illuminance at the position Y of 20, which is the light from the optical path A. When combined by the half mirror 24, as shown in FIG. 5E, the illuminance is about 70 and an almost uniform illuminance distribution is obtained.

  If the liquid crystal shutter 72 is provided in one optical path without branching the optical path into two, if correction is made to obtain a uniform illuminance distribution with an illuminance of about 70, the transmittance of the liquid crystal shutter 72 is reduced to about It must be adjusted between 70% and 100%, and this is corrected by only the upper three gradations having high transmittance among the eight gradations. However, when the light is split into two and correction is performed on only one of them as in the present embodiment, the transmittance is adjusted between about 40% and 100% as described above. Therefore, correction with the upper five gradations having high transmittance is possible, and subtle correction is possible as compared with the case where the two branches are not used. In addition, if the ratio of transmission and reflection of the half mirror 21 as the light branching portion is changed according to an expected illuminance deviation (illuminance difference between the maximum illuminance and the minimum illuminance), finer correction is possible.

  As described above, according to the exposure apparatus 1 and the exposure method of the present embodiment, the following effects can be obtained.

  According to the present embodiment, the light emitted from the illumination optical system 11 is branched into two, and the liquid crystal shutter 72 serving as a light adjusting unit capable of adjusting the light transmittance distribution is provided in one of the optical paths (optical path B). Therefore, for example, when the liquid crystal shutter 72 that can be selected from a plurality of levels set at equal intervals between 0% and 100% is used, the light source is lighter than when the optical path is not branched. Corrections can be made at many levels without reducing the efficiency, and subtle illuminance unevenness can be corrected.

(Modification)
In addition, you may change embodiment of this invention as follows.

  In the first embodiment, the illumination optical system driving unit 81 causes the second light so that the light emitted from the first illumination optical system 10 and the light emitted from the second illumination optical system are in phase with each other. The position of the illumination optical system is determined, but this may be set to a position where the phase of the light emitted from each illumination optical system is shifted by 180 °. In this case, for example, the illuminance distribution on a certain straight line in the exposure area has a desired illuminance over the entire range as shown in FIG. 6A, but the center is bright and both ends are dark. In this case, as shown in FIG. 6B, the liquid crystal shutter 71 is set to a gradation having a higher transmittance as the dot corresponding to the brighter position. As a result, the light is canceled in the brighter region, and as shown in FIG. 6C, it is possible to obtain a substantially uniform illuminance distribution.

  In the first embodiment, the second illumination optical system 70 includes the liquid crystal shutter 71 and emits a light amount corresponding to the position. However, the adjustment of the light amount is not limited to the liquid crystal shutter 71, The illumination optical system 70 may be provided by other means such as a plurality of light sources whose outputs can be individually adjusted.

  In the first embodiment, the light source output of the second illumination optical system 70 is determined based on the illuminance difference between the highest illuminance part and the lowest illuminance part in the illuminance distribution by the first illumination optical system 10. As long as it is possible to emit a light amount sufficient to compensate for the illuminance difference, it may be fixed. Furthermore, when the illuminance unevenness correction is performed, the first illumination optical system 10 and the second illumination optical system 70 may be simultaneously emitted in a state where all the dots of the liquid crystal shutter 71 are set to the maximum transmittance. . In this case, the illumination optical system driving unit 81 is driven while measuring the illuminance with the illuminance sensor 60, the position of the second illumination optical system 70 is determined at the position where the maximum illuminance is obtained, and then the liquid crystal shutter according to the illuminance distribution. The transmittance of 71 will be controlled.

  According to this, since the illuminance distribution of the light synthesized from the light emitted from the first illumination optical system and the light emitted from the second illumination optical system is measured to detect illuminance unevenness, Illuminance unevenness due to the second illumination optical system can be corrected in advance, and it is possible to easily perform illumination unevenness correction.

  In the second embodiment, the illuminance unevenness correction is performed without the liquid crystal shutter 72 in the optical path B. However, all the dots of the liquid crystal shutter 72 are provided with the maximum transmittance while the liquid crystal shutter 72 is provided. In this state, illuminance unevenness correction may be performed.

  According to this, since the illuminance distribution of the light obtained by combining the light passing through the optical path A and the light passing through the optical path B and transmitted through the liquid crystal shutter 72 is measured to detect the illuminance unevenness, It is possible to correct the illuminance unevenness to be performed in advance, and the illuminance unevenness correction can be easily performed.

  In this embodiment, the gradation of the liquid crystal shutters 71 and 72 is set so that uniform illuminance can be obtained in the entire exposure area. However, the ideal illuminance distribution is not limited to this, and It is possible to obtain a desired illuminance distribution such as a distribution in which the illuminance is higher in the central portion than in the portion.

1 is a schematic diagram showing a schematic configuration of an exposure apparatus according to a first embodiment. (A) is a front view of a liquid-crystal shutter, (b) is an enlarged view of the principal part of a liquid-crystal shutter. It is a figure which shows the mode of illumination unevenness correction | amendment, (a) is a figure which shows the illumination distribution before illumination unevenness correction, (b) is a figure which shows the gradation distribution of a liquid-crystal shutter, (c) is illumination unevenness correction. The figure which shows illuminance distribution after. FIG. 10 is a schematic diagram showing a schematic configuration of an exposure apparatus according to a second embodiment. It is a figure which shows the mode of illumination unevenness correction | amendment, (a) is a figure which shows the illumination distribution before illumination unevenness correction, (b) is a figure which shows the illumination distribution after light branching, (c) is a liquid crystal shutter. The figure which shows gradation distribution, (d) is a figure which shows the illuminance distribution after permeate | transmitting a liquid-crystal shutter, (e) is a figure which shows the illuminance distribution after illumination unevenness correction | amendment. It is a figure which shows the mode of the illumination intensity nonuniformity correction which concerns on a modification, (a) is a figure which shows the illumination intensity distribution before illumination intensity nonuniformity correction, (b) is a figure which shows the gradation distribution of a liquid-crystal shutter, (c) is a figure. The figure which shows the illumination intensity distribution after illumination intensity nonuniformity correction | amendment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exposure apparatus, 10 ... 1st illumination optical system, 11 ... Illumination optical system, 20 ... Half mirror as light combining part, 21 ... Half mirror as light branching part, 22, 23 ... Reflection mirror, 24 ... Light combining part 30... Reticle as photomask, 40... Projection optical system, 50... Stage, 60. Illuminance sensor, 70... Second illumination optical system, 71. Shutter, 80 ... control unit, 81 ... illumination optical system drive unit as phase adjustment unit, A, B ... optical path, W ... semiconductor wafer as exposure object.

Claims (13)

In an exposure apparatus that performs exposure by irradiating an exposure object with light emitted from an illumination optical system through a photomask,
A first illumination optical system;
A second illumination optical system capable of adjusting the illuminance distribution of the emitted light in accordance with the illuminance distribution in the exposure region;
A light combining unit that combines the light emitted from the first illumination optical system and the light emitted from the second illumination optical system;
An exposure apparatus for irradiating an exposure object with light synthesized by the photosynthesis unit through a photomask.   2. The exposure apparatus according to claim 1, wherein the first and second illumination optical systems emit light having coherency, the light emitted from the first illumination optical system, and the second illumination optical system. An exposure apparatus characterized in that the phase of the light emitted from the illumination optical system is matched in the light combining unit.   2. The exposure apparatus according to claim 1, wherein the first and second illumination optical systems emit light having coherency, the light emitted from the first illumination optical system, and the second illumination optical system. An exposure apparatus characterized in that the phase of light emitted from the illumination optical system is shifted by 180 ° in the light combining unit.   4. The exposure apparatus according to claim 1, wherein the first and second illumination optical systems emit light having coherency, and are emitted from the first illumination optical system. 5. An exposure apparatus comprising: a phase adjusting unit capable of adjusting a phase shift between the light and the light emitted from the second illumination optical system in the light combining unit. In an exposure apparatus that performs exposure by irradiating an exposure object with light emitted from an illumination optical system through a photomask,
A light branching unit that splits the optical path of the light emitted from the illumination optical system into two branches;
A dimming unit that is provided in one of the two branched optical paths and can adjust the light transmittance distribution in accordance with the illuminance distribution in the exposure region;
A light combining unit that combines the two branched light paths;
An exposure apparatus for irradiating an exposure object with light synthesized by the photosynthesis unit through a photomask. In an exposure apparatus that performs exposure by irradiating an exposure object with light emitted from an illumination optical system through a photomask,
A light branching portion for branching the optical path of light emitted from the illumination optical system and transmitted through the photomask;
A dimming unit that is provided in one of the two branched optical paths and can adjust the light transmittance distribution in accordance with the illuminance distribution in the exposure region;
A light combining unit that combines the two branched light paths;
An exposure apparatus that irradiates an exposure object with light synthesized by the photosynthesis unit. Measuring an illuminance distribution of light emitted from the first illumination optical system with an illuminance sensor;
Adjusting the illuminance distribution of the light emitted from the second illumination optical system according to the illuminance distribution measured by the illuminance sensor;
After the illuminance unevenness correction step having
An exposure method comprising combining light emitted from the first illumination optical system and light emitted from the second illumination optical system by a light combining unit and irradiating an exposure object. Measuring an illuminance distribution of light emitted from the first illumination optical system and the second illumination optical system and synthesized by an illuminance sensor;
Adjusting the illuminance distribution of the light emitted from the second illumination optical system according to the illuminance distribution measured by the illuminance sensor;
After the illuminance unevenness correction step having
An exposure method comprising combining light emitted from the first illumination optical system and light emitted from the second illumination optical system by a light combining unit and irradiating an exposure object.   9. The exposure method according to claim 7, wherein the first and second illumination optical systems emit light having coherency, the light emitted from the first illumination optical system, and An exposure method, wherein the light emitted from the second illumination optical system is in phase with the light combining unit.   9. The exposure method according to claim 7, wherein the first and second illumination optical systems emit light having coherency, the light emitted from the first illumination optical system, and An exposure method, wherein the light emitted from the second illumination optical system is 180 ° out of phase in the light combining unit.   11. The exposure method according to claim 7, wherein the first and second illumination optical systems emit light having coherency, and the illuminance unevenness correction step further includes: Exposure comprising adjusting the phase shift between the light emitted from the first illumination optical system and the light emitted from the second illumination optical system in the light combining unit Method. Measuring the illuminance distribution of light emitted from the illumination optical system with an illuminance sensor;
Controlling the light control unit capable of adjusting the light transmittance distribution according to the illuminance distribution measured by the illuminance sensor;
After the illuminance unevenness correction step having
Bifurcating the optical path of light emitted from the illumination optical system;
Combining light transmitted through the dimming unit provided in one of the two branched optical paths and light transmitted through the other optical path in a light combining unit;
An exposure method comprising irradiating an exposure object with light synthesized by the photosynthesis unit through a photomask. Measuring the illuminance distribution of light emitted from the illumination optical system with an illuminance sensor;
Controlling the light control unit capable of adjusting the light transmittance distribution according to the illuminance distribution measured by the illuminance sensor;
After the illuminance unevenness correction step having
Bifurcating an optical path of light emitted from the illumination optical system and transmitted through a photomask;
Combining light transmitted through the dimming unit provided in one of the two branched optical paths and light transmitted through the other optical path in a light combining unit;
An exposure method comprising irradiating an exposure object with light synthesized by the photosynthesis unit through a photomask.

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