JP2009224552A - Proximity exposure method and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an undulation of a workpiece stage and an overweight at a central part of a short side of a photomask cannot be applied so that it cannot be attained sufficiently to arrange the photomask in parallel with the workpiece, in a method for correcting a flexing of the photomask caused by its own weight in a proximity exposure system by pressing opposite edge parts of a long side of the photomask from the upper part by a correcting bar. <P>SOLUTION: A flexing correcting bar 13 includes a division correcting bar 12 which is divided into a plurality of parts so as to press the photomask, and an adjusting screw 14 for movably fixing the division correcting bar, individually. Further, in the exposure apparatus, the correcting bar 13 includes a load cell 15 surrounding a leading edge part of the adjusting screw 14, and the adjusting screw is a differential screw. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for correcting deflection due to the weight of a photomask used in a proximity exposure type (proximity exposure type) exposure apparatus.

  As shown in FIG. 2A, an exposure apparatus using a proximity exposure method (proximity exposure method) includes an exposure chuck 7 that holds a substrate to be exposed (hereinafter referred to as a workpiece 8) on the upper surface, A mask stage 6 or a mask holder (not shown) for holding the photomask 1 is provided above. At the time of exposure, the work 8 and the photomask 1 are arranged with a predetermined minute gap (proximity gap or clearance, hereinafter referred to as clearance) of, for example, about 90 to 200 μm. The pattern of the photomask is baked on the photoresist formed on the work 8 by irradiation.

  However, if the photomask is held and fixed using a mask stage or a mask holder, the center portion of the photomask sinks due to its own weight when the photomask size increases. Then the mask will bend. As a result, since the clearance between the photomask and the workpiece varies depending on the location, the mask pattern cannot be accurately baked onto the photoresist, and the resist pattern accuracy obtained after development is lowered.

  As a method for correcting the deflection due to its own weight, it is possible to introduce air between the photomask 1 and the work 8 and correct the deflection with the air pressure. However, the structure is complicated and large, and is not practical. There was a problem.

On the other hand, a method for correcting the deflection of the mask with a deflection correction bar has been proposed (Patent Document 1). That is, as shown in FIG. 2A, the photomask is supported by the support member 4 from the lower side slightly inside the ends of the two opposite sides (for example, two long sides) of the photomask. In this method, a linear member 2 (hereinafter referred to as a deflection correction bar) is brought into contact with the edge 5 of the mask on the outer side of the member and pressed, and the center portion of the photomask is lifted by the lever principle to correct the deflection. The deflection correcting bar 2 for pressurization has a flat and long T-shaped shape in cross section as shown in FIG. 1A, and the T-shaped body portion 13 is made of SUS (stainless steel) material. However, a UPE resin (ultra high molecular weight polyethylene) having a hardness lower than that of SUS is attached as a cushioning material to the front end portion 3 that is in direct contact with the photomask, thereby increasing the pressurization to the photomask. In this method, pressure is applied to the upper portions of the correction bars 2 and 13 using the torque of the servo motor 10 and transmitted to the photomask edge 5 as a load.
JP 2001-109160 A

  However, the deflection correction bar in the form integrated with the above T-shape has the following problems.

  First, a UPE resin having a width of 1 mm and a length of about the substrate length or less is attached to a portion of the SUS material that contacts the workpiece 8 of the T-shaped correction bar. However, some parts do not come into contact with the workpiece due to distortion or bending of the correction bar, scratches or bending of the UPE. The problem of uniformity occurs.

  Further, the length of the UPE member 3 (T-shaped SUS member) is longer than the length of the photomask 1 as shown in FIG. Since it must be shortened, there is a problem that an appropriate load cannot be applied to the corner portion 9 of the photomask. As a result, it was difficult to correct the deflection because a force for lifting the central portion of the short side was not applied.

  Furthermore, on the workpiece side, there is a problem in the surface flatness of the stage 7 on which the workpiece is placed. When the stage is new, the stage surface generally has a swell of about 12 to 25 μm. However, as the stage is used, deterioration with time progresses and flatness decreases. The workpiece deforms following the undulation of the stage. Therefore, due to this influence, there is a problem that the clearance between the mask and the workpiece cannot be set to a desired value at the time of exposure, and cannot be ignored when forming a fine pattern on the workpiece.

  From the above, when a deflection correction bar having a conventional structure is used, the clearance between the photomask 1 and the workpiece 8 on the stage over the entire surface can be set to a desired value of 90 to 200 μm even if some load is adjusted. It is difficult to set to a value. As a result, there is a problem that the resist pattern obtained by baking and development does not partially become a desired pattern, and the resolution and pattern accuracy of the resist pattern do not increase.

  Therefore, an object of the present invention is to satisfactorily achieve the clearance between the photomask and the substrate to be exposed for each location, and specifically, to give the photomask side deflection according to the waviness on the substrate to be exposed. It is an object of the present invention to provide an exposure method and an exposure apparatus that can perform pressurization that is sufficiently controlled even in the center portion of the short side. In other words, it is possible to give a load distribution having a desired non-uniformity to the entire edge of the photomask, and to expose the load distribution to the actual clearance between the photomask and the substrate to be exposed. A method and an exposure apparatus are provided.

  The present invention has been made in view of the above problems, and the invention according to claim 1 is an exposure method in which a substrate to be exposed is exposed through a photomask by a proximity exposure method, and the photomask is bent by its own weight. Is corrected by pressurizing the end of the photomask from above with the deflection correction bars provided on the edges of the two opposing sides of the photomask, and each of the deflection correction bars can contact the photomask. In this way, each of the divided parts is provided via an adjusting screw for individually moving in the photomask direction, so that the pressure applied to the photomask part contacting each divided part is individually provided. The proximity exposure method is characterized in that the exposure is changed.

  By introducing a split structure into the conventional deflection correction bar, different pressure can be applied to the edges of the opposing long sides of the photomask for each region. As a result, the amount of deflection of the entire photomask substrate can be controlled fairly freely for each location.

The invention of claim 2 is an exposure apparatus using the above method, comprising: an exposure chuck that holds a substrate to be exposed; and a mask stage or mask holder that holds a photomask so as to face the substrate to be exposed. In an exposure apparatus that exposes a substrate to be exposed through the photomask in a proximity exposure system,
In order to correct the deflection of the photomask due to its own weight, it comprises a deflection correction bar that corrects by pressing the edges of two opposite sides of the photomask from above,
The deflection correction bar is divided into a plurality of parts so that each can come into contact with the photomask, and each of the divided parts is provided via an adjustment screw that can be individually moved in the photomask direction. The exposure apparatus is characterized in that the pressure applied to the photomask portion in contact with the portion is individually changed.

  According to a third aspect of the present invention, there is provided an exposure apparatus characterized in that a load cell is provided between the adjustment screw and the divided portion.

  With this configuration, the amount of pressure applied to each part of the end portion of the photomask substrate can be easily quantified.

  Further, the invention of claim 4 is an exposure apparatus characterized in that the adjusting screw is a differential screw.

  By finely changing the position of the correction bar divided by using the differential screw (the amount by which the division correction bar is pushed), the pressurization amount can be finely adjusted.

  Further, the invention of claim 5 is an exposure apparatus comprising a sensor for measuring a clearance between the photomask and a substrate to be exposed.

  With this configuration, the clearance between the photomask and the substrate to be exposed can be easily measured.

  As described above, according to the present invention, since the deflection correction bar that contacts the photomask is divided and subdivided, the load applied to the photomask is changed by adjusting the screw push-in amount for each divided correction bar. be able to. As a result, it is possible to finely adjust the deflection on the photomask side corresponding to the undulation of the surface of the work stage. Also, with regard to the bending of the central part of the two short sides of the photomask, which was difficult to improve in the past, it was easy to apply a load independently to the corner, so it was placed on the photomask and stage. The clearance of the workpiece (substrate to be exposed) can be kept constant over the entire surface. Therefore, accurate pattern exposure is possible.

  Since the load applied to the dividing bar by the load cell is known as a value and the clearance can be measured at the same time, the best load distribution and clearance distribution after photomask setting can be grasped. By using these data, it becomes easy to adjust the clearance when the photomask is replaced and to cope with the stage change with time. This point will be described below.

  There are various types of photomasks depending on the size, material, thickness, type of pattern formed on the photomask, and the like. Therefore, in the exposure apparatus according to the present invention, it is necessary to adjust the adjustment screw to make the clearance with the substrate to be exposed a predetermined clearance each time various photomasks are set. In industrial products, a small variety of products is in progress. For this reason, the photomask set in the exposure apparatus is not limited to one type, and depending on the setup of the exposure process, it is necessary to perform exposure by alternately replacing a plurality of photomasks. When the mask is replaced, adjustment with the adjustment screw and confirmation of the clearance are alternately performed, and if a good clearance is made by trial and error, the working time becomes long, and the working efficiency decreases.

On the other hand, if the clearance between the photomask and the substrate to be exposed becomes good, the electrical signal obtained in each load cell is stored in advance, and when the recorded photomask is set, recording is performed. If adjustment (push-in) is performed with an adjustment screw so that the same signal as the electric signal is obtained, a good clearance can be obtained in a short time, and work efficiency is improved.

  An example of the exposure method and exposure apparatus according to the present invention will be described below with reference to FIGS.

  FIG. 1A shows a schematic view of a T-shaped deflection correction bar 13 used in a conventional exposure apparatus as viewed from the long side direction. The deflection correction bar 13 is connected to pressurizing means such as a servo motor (not shown) via a drive connecting portion 11, and the pressure by the pressurizing means is transmitted to the deflection correcting bar 13 via the drive connecting portion 11. .

  On the other hand, FIG. 1B is a schematic view of the deflection correction bar according to the present invention as viewed from the long side direction, and the deflection correction bar according to the present invention is composed of three independent portions A, B, and C, respectively. Is done. A deflection correction bar for lifting the central portion of the photomask according to the principle of leverage, and a portion that directly contacts the workpiece is C, and C is composed of a plurality of parts (hereinafter referred to as divided bars). In this divided shape, the horizontal length of each divided bar need not be the same. A portion A is a drive connecting portion 11 which is connected to a pressurizing means such as a servo motor (not shown) and receives a load (pressure) applied from the pressurizing means. B is a part where the dividing bar is connected to one side via the adjusting screw 14 and connected to the drive connecting part A on the other side (hereinafter referred to as a connecting part 16). In addition, you may connect the connection part 16 to the pressurization means which is not shown in figure directly, without passing through the drive connection part 11. FIG.

  Each of the split bars 12 is provided with a preparation screw 14, preferably a differential screw 14 'that can be finely adjusted as shown in FIG. It is desirable that a fixing screw for preventing the adjustment screw from loosening is provided on both sides of the preparation screw 14 (not shown). It is desirable to attach a buffer material of UPE resin to the tip of the dividing bar as in the conventional structure.

  The pressurizing force from the pressurizing means such as a servo motor is applied to the photomask through the drive connecting portion 11, the connecting portion 16, and the dividing bar. At this time, each adjustment screw 14 is adjusted to change the height of each division bar as viewed from the connecting portion 14 (the so-called division correction bar push amount is changed. This is shown in FIG. As a result, the amount of pressure applied to the photomask can be changed for each divided bar.

  Note that the edge of the photomask with which the dividing bar comes into contact does not necessarily have to be on the long side, but since a larger load is required on the short side, it is desirable to make contact on the long side. Furthermore, depending on the shape of the substrate corresponding to the photomask, all four sides can be pressurized using the correction bar according to the present invention.

  Further, in order to measure the load (pressure) applied to the dividing bar between the adjusting screw and the dividing bar, a load cell that converts the pressure into an electric signal such as a voltage value or a current value. 15 is disposed. The load cell 15 may be embedded in the dividing bar. An electric signal corresponding to the load (pressure) is taken out from the load cell 15, and the electric signal is input to the load monitoring monitor and observed.

  Since the number of the division bars 12 depends on the size of the photomask, it is desirable to determine in advance using simulation or the like. In the present specification, Table 1 shows the results of pressurizing by forming a correction bar for one side with nine divided bars for preventing deflection of a photomask having a size of 680 × 920 mm. The glass substrate as a photomask is blue plate glass and has a thickness of 8 mm. A load was applied so that the clearance from the exposed substrate at the center of the photomask was minimized. At that time, adjust the screws on each of the 18 bars (total number of bars used on 2 sides). The overload was adjusted. The load applied to the dividing bar was calculated by comparing the output value of the electric signal from the load cell with the reference load, and the clearance between the mask and the workpiece was evaluated using a laser displacement measuring device.

表中、下段の図は９分割された分割バーの位置と長さを示し、太線部分が荷重が加えられた分割バーである。分割バーの離間距離を大きくすると撓みは減少する傾向が見られた。また、分割しない従来型の撓み補正バーに較べて、少ない荷重で撓みの補正ができた。さらに、マスクコーナー部分に向けて荷重を段階的に増すようにすると、クリアランスが均一になる、すなわちフォトマスクとワークとの平行性が向上する傾向も見られた。

In the table, the lower figure shows the positions and lengths of the divided bars divided into nine, and the thick line portions are the divided bars to which a load is applied. When the separation distance between the dividing bars is increased, the bending tends to decrease. Further, the deflection can be corrected with a small load compared to the conventional deflection correction bar which is not divided. Furthermore, when the load was increased stepwise toward the mask corner, there was a tendency that the clearance became uniform, that is, the parallelism between the photomask and the workpiece was improved.

  The differential screw is formed by screwing an external screw and an internal screw with different pitches, and a small displacement (in this example, the height of each divided bar viewed from the connecting portion 16) according to the amount of rotation of the screw. Can be adjusted. That is, the height of the dividing bar viewed from the connecting portion 14 can be adjusted in units of μm by a combination of two different screw pitches, thereby making it possible to finely adjust the pressure applied to the photomask.

  If the pressure applied to the correction bar is small, fine adjustment means such as a micrometer can be used. However, the size of the photomask is increasing, and the pressure applied to the correction bar has exceeded 100 kg. Therefore, the micrometer has a problem in strength. On the other hand, if the fine adjustment means is a differential screw, the differential screw is structurally strong, so no problem occurs even if the pressure is increased. Therefore, it is preferable to use a differential screw as the fine adjustment means.

(A) It is a front view of a conventional T-shaped deflection correction bar. (B) It is a front view of the division | segmentation deflection | deviation correction bar | burr which becomes this invention. (C) It is sectional drawing explaining a mode that a division | segmentation bar is fastened with the differential screw as a preparation screw. The figure on the left shows the case where it is tightened and pushed, and the figure on the right shows that it has been loosened. (A) It is a figure explaining a mode that a photomask edge is contact-contacted with a T-shaped bending correction bar | burr from a cross section. (B) It is a figure which illustrates typically the arrangement | positioning which looked at the photomask and the deflection | deviation correction bar from the upper part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photomask 2 ... Deflection correction bar 3 ... Tip part 4 of a deflection correction bar ... Support member 5 ... Photomask edge part 6 ... Mask stage 7 ... With exposure chuck Stage 8 ... Workpiece (substrate to be exposed)
9 ... Photomask corner 10 ... Servo motor 11 ... Drive coupling 12 ... Dividing bar 13 ... Deflection correction bar 14 ... Preparation screw 14 '... Differential screw 15 ..Load cell 16 ... connecting part

Claims (5)

  In an exposure method in which a substrate to be exposed is exposed through a photomask by a proximity exposure method, the photomask is deflected by its own weight with a deflection correction bar provided at the edges of two opposite sides of the photomask. The edge of the mask is corrected by applying pressure from above, and the deflection correction bar is divided into a plurality of parts so that each can come into contact with the photomask, and the divided parts are individually provided in the photomask direction. A proximity exposure method characterized in that the pressure applied to the photomask part contacting each divided part is individually changed by providing it via an adjustment screw for moving. An exposure chuck for holding the substrate to be exposed and a mask stage or a mask holder for holding a photomask so as to face the substrate to be exposed, and exposing the substrate to be exposed through the photomask by a proximity exposure method. In the exposure apparatus to perform
In order to correct the deflection of the photomask due to its own weight, it comprises a deflection correction bar that corrects by pressing the edges of two opposite sides of the photomask from above,
The deflection correction bar is divided into a plurality of parts so that each can come into contact with the photomask, and each of the divided parts is provided via an adjustment screw that can be individually moved in the photomask direction. An exposure apparatus characterized by individually changing the pressure applied to a photomask part in contact with the part.   The exposure apparatus according to claim 2, wherein a load cell is provided between the adjustment screw and the divided portion.   The exposure apparatus according to claim 2, wherein the adjustment screw is a differential screw.   The exposure apparatus according to claim 2, further comprising a sensor for measuring a clearance between the photomask and the substrate to be exposed.

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