JP2009151184A - Method for manufacturing photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a photomask capable of enhancing the positional accuracy of a device pattern in an actual product chip. <P>SOLUTION: A phase shift layer 32 and a light shielding film 33 are formed on a transparent substrate 31, and a first photoresist film is further formed thereon. A dummy pattern is drawn using a drawing machine. After developing processing is successively performed, the light shielding film 33 and the phase shift layer 32 are etched to form a dummy pattern 22 on the substrate 31. The positional slippage of the dummy pattern 22 is measured, and the result is fed back to the drawing machine to adjust the correction parameter of the drawing machine. Thereafter, a second photoresist film 35 is formed on the substrate 31, and a device pattern is drawn by the drawing machine adjusted in correction parameter. After developing processing is successively performed thereto, the light shielding film 33 and the phase shift layer 32 are etched to form a device pattern 21 on the substrate 31. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a photomask used in a photolithography process or the like when manufacturing a semiconductor device, and more particularly to a method of manufacturing a photomask having high pattern positional accuracy in an actual product.

  Photolithography is frequently used for manufacturing semiconductor devices such as LSI. In a general photolithography process, a pattern formed on a photomask is transferred to a photosensitive film using an exposure apparatus. The positional accuracy of the pattern transferred to the photosensitive film greatly depends on the positional accuracy of the photomask pattern. Therefore, the photomask is required to have high pattern positional accuracy. In general, since a semiconductor device is manufactured by overlaying a plurality of layers patterned by a photolithography method, the photomask is required to have high interlayer overlay accuracy.

  1A to 1E are cross-sectional views showing an example of a conventional photomask manufacturing method in the order of steps. Here, a method for manufacturing a halftone phase shift photomask is described.

  First, as shown in FIG. 1A, a halftone phase shift layer 12 and a light shielding layer 13 are sequentially formed to a predetermined thickness on a transparent substrate 11 made of quartz or the like. Thereafter, a positive photoresist film 14 is formed on the light shielding layer 13 to a predetermined thickness.

  Next, a predetermined region of the photoresist film 14 is exposed using an electron beam drawing machine or a laser drawing machine (hereinafter simply referred to as “drawing machine”), and then development processing is performed. Thereby, as shown in FIG. 1B, the exposed portion of the photoresist film 14 is removed, and a part of the light shielding film 13 is exposed.

  Next, the light shielding film 13 is etched using the photoresist film 14 as a mask. Thereby, as shown in FIG. 1C, the halftone phase shift layer 12 is exposed through the opening of the photoresist film 14. Thereafter, the photoresist film 14 is removed.

  Next, as shown in FIG. 1D, the halftone phase shift layer 12 is etched using the remaining light shielding film 13 as a mask. Next, as shown in FIG. 1E, the light shielding film 13 is removed by etching. In this way, a halftone phase shift photomask is completed.

  By the way, the position accuracy of the pattern of the photomask largely depends on the accuracy of the drawing machine (stage accuracy, shot formation / placement accuracy, etc.) Therefore, periodic inspection management is performed on the drawing machine in order to always maintain the pattern position accuracy with high accuracy. For example, during regular inspections, a test pattern is drawn on a test piece using a drawing machine, and the positional deviation of each drawn test pattern at each position is measured using a coordinate position measuring device, and then the test pattern is used using the measurement result. Adjust the correction parameters of the drawing machine so that is drawn correctly.

  FIG. 2 is a diagram illustrating a result of measuring a positional deviation by drawing a test pattern using a drawing machine in which correction parameters are adjusted by the above-described method. As can be seen from FIG. 2, by appropriately adjusting the correction parameters of the drawing machine, a random error that inevitably occurs remains, but the systematic error caused by the drawing machine can be sufficiently eliminated.

In addition, there exists what was described in patent document 1 as a prior art considered to be related to this invention. In the technique described in Patent Document 1, in the method of manufacturing a phase shift photomask (reticle), a first layer pattern is formed, and then a photoresist film is formed on the entire surface. Thereafter, exposure and development are performed to form openings with a desired pattern in the photoresist film. Next, the overlay accuracy of the pattern of the first layer and the pattern of the photoresist film is measured, and the etching process using the photoresist film as a mask is performed only when the overlay accuracy is good, and the pattern of the second layer Form.
Japanese Patent Laid-Open No. 2004-77808

  However, the present inventors consider that the conventional photomask manufacturing method has the following problems.

  FIG. 3 is a diagram illustrating a result of measuring a positional deviation by actually drawing a device pattern of a product chip using a drawing machine in which correction parameters are adjusted by the above-described method. From FIG. 3, an error other than a random error (systematic error) occurs when a device pattern of an actual product chip is drawn even though a test pattern is drawn and adjustment parameters of the drawing machine are adjusted. Recognize. That is, in the example shown in FIG. 3, the upper portion has a right position shift and the lower portion has a left position shift.

  The difference between the misalignment when drawing the test pattern and the misalignment when drawing the device pattern of the actual product chip is thought to be due to different drawing areas, drawing times, and complicated stage movements for each product. . In addition, the direction and size of the positional deviation when the device pattern of the actual product chip is drawn differs from drawing machine to drawing machine even with the same model, and there is a flaw unique to each drawing machine. Therefore, by simply drawing a test pattern and adjusting the correction parameters of the drawing machine using the result, it is possible to suppress misalignment of the pattern of the photomask used for manufacturing semiconductor devices that will be further integrated in the future. Is not enough.

  An object of the present invention is to provide a photomask manufacturing method in which the position accuracy of a device pattern in an actual product chip is good.

  According to one aspect of the present invention, a first step of forming a light shielding film on a substrate, a second step of forming a first pattern on the light shielding film using a drawing machine, and the first pattern A third step of measuring the position accuracy of the first pattern, a fourth step of adjusting the drawing machine according to the measurement result of the position accuracy of the first pattern, and the drawing machine adjusted in the fourth step And a fifth step of forming a second pattern on the light-shielding film on which the first pattern is formed.

  In the present invention, after the first pattern is formed on the light shielding film on the substrate, the positional accuracy of the first pattern is measured. As the first pattern, a pattern that does not affect the electronic circuit, for example, a dummy pattern during CMP (Chemical Mechanical Polishing) is preferably used. And after adjusting a drawing machine according to the measurement result of the positional accuracy of a 1st pattern, an electronic circuit is comprised as a 2nd pattern in the light shielding film in which the 1st pattern was formed using the drawing machine Patterns such as wiring and contact holes are formed.

  In the present invention, since the second pattern is formed using a drawing machine that is adjusted using the measurement result of the positional deviation of the first pattern formed in advance on the light shielding film, the positional deviation of the second pattern is suppressed. Is done.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 4 is a plan view showing an example of a photomask, and FIGS. 5 and 6 are cross-sectional views showing a photomask manufacturing method according to the first embodiment of the present invention. 5 and 6 show cross sections taken along the line II in FIG. In the present embodiment, an example in which the present invention is applied to a halftone phase shift photomask is described.

  As shown in FIG. 4, the photomask 20 is provided with a device pattern 21 and a dummy pattern 22. The device pattern 21 is a pattern for forming a part constituting a desired electronic circuit such as a wiring or a contact hole. In FIG. 4, the device pattern 21 is schematically indicated by “F”. However, the device pattern in an actual photomask is a pattern corresponding to a wiring or a contact hole to be formed.

  On the other hand, the dummy pattern 22 is a pattern formed for the convenience of manufacture, and does not constitute an electronic circuit. As a typical dummy pattern, there is a dummy pattern formed for surface flattening by CMP (Chemical Mechanical Polishing).

  A photomask manufacturing method according to the first embodiment of the present invention will be described below with reference to FIGS.

  First, as shown in FIG. 5A, a MoSiN film, for example, having a thickness of 0.065 μm is formed as a halftone phase shift layer 32 on a transparent substrate 31 made of quartz or the like. Next, for example, a Cr (chrome) film is formed on the halftone phase shift layer 32 as a light shielding layer 33 to a thickness of 0.05 μm. Next, a positive photoresist film 34 is formed on the light shielding layer 33 to a thickness of 0.3 μm, for example.

  Next, the dummy pattern formation region of the photoresist film 34 is selectively exposed using an electron beam drawing machine or a laser drawing machine. Here, it is important not to expose the device pattern formation region. Thereafter, post-exposure baking (PEB) and development processing are performed to remove the exposed portion of the photoresist film 34 (the portion corresponding to the dummy pattern 22), as shown in FIG. 5B. Then, an opening 34a through which the light shielding film 33 is exposed is formed.

  Next, as shown in FIG. 5C, the light shielding film 33 is etched using the photoresist film 34 as a mask. Thereafter, the photoresist film 34 is removed.

  Next, as shown in FIG. 5D, the halftone phase shift layer 32 is etched using the remaining light shielding layer 34 as a mask to form a dummy pattern 22 (an opening of the halftone phase shift layer 32).

  After the dummy pattern 22 is formed on the substrate 31 in this way, the positional deviation using the coordinate position measuring device, that is, the position of the designed dummy pattern 22 and the position of the dummy pattern 22 actually formed on the substrate 31 is performed. Measure the deviation. In this case, it is not necessary to measure the positional deviation of all the dummy patterns 22. It is preferable to select a dummy pattern 22 for measuring the positional deviation that is close to the device pattern formation region. In addition, it is preferable to measure misalignment at 100 or more locations for one photomask.

  After measuring the positional deviation of the dummy pattern 22 using the coordinate position measuring device, a system error is calculated and a correction parameter is obtained. Actually, a design position is input to the coordinate position measuring device, and a systematic error is calculated by a predetermined calculation formula (for example, an approximate calculation formula by a cubic formula) in the coordinate position measurement device.

  The system error thus obtained is fed back to the drawing machine on which the dummy pattern 22 is drawn, and the correction parameters of the drawing machine are adjusted.

  After adjusting the correction parameters of the drawing machine, a positive photoresist film 35 is formed to a thickness of, for example, 0.3 μm on the transparent substrate 31 formed up to the dummy pattern 22 as shown in FIG. Thereafter, a device pattern is drawn on the photoresist film 35 using the same drawing machine as that used to draw the dummy pattern 22.

  Next, post-exposure baking and development are performed to remove the exposed photoresist film 35 and form an opening 35a through which the light-shielding film 33 is exposed, as shown in FIG. To do. Thereafter, as shown in FIG. 6B, the light-shielding film 33 is dry-etched using the photoresist film 35 as a mask to form an opening through which the halftone phase shift layer 32 is exposed.

  Next, as shown in FIG. 6C, the halftone phase shift layer 32 is dry-etched using the photoresist film 35 and the light shielding film 33 as a mask, and the device pattern 21 (opening of the halftone phase shift layer 32) is formed. Form. Thereafter, the photoresist film 35 is removed.

  Next, an alignment mark and a blind cover are formed. That is, a photoresist film is formed on the entire upper surface of the substrate 31, and exposure and development processes are performed to leave a photoresist film (not shown) only on a predetermined region of the light shielding film 33. Thereafter, the light shielding film 33 is etched using the photoresist film as a mask to form an alignment mark made of the light shielding film 33, a blind cover, and the like (both not shown).

  Thereafter, the position accuracy of the device pattern 21 is confirmed using a coordinate position measuring apparatus. In this way, the photomask 20 having the device pattern 21 and the dummy pattern 22 shown in FIG. 6D is completed.

  In this embodiment, as described above, after the dummy pattern 22 is formed on the substrate 31 to be the photomask 20, the positional deviation of the dummy pattern 22 is measured, and the result is fed back to the drawing machine. Adjust the correction parameter. And the device pattern 21 is drawn on the board | substrate 31 using the drawing machine. Thereby, the systematic error resulting from a drawing machine can be made sufficiently small.

  Further, in the present embodiment, since the systematic error can be sufficiently reduced, the overlay accuracy between the layers can be improved, and the manufacture of an LSI having a high-density multilayer wiring structure can also be supported.

  FIG. 7 is a diagram showing a result of actually drawing a product chip pattern on a photomask and measuring a device pattern positional deviation by the method of the present embodiment. From the comparison between FIG. 7 and FIG. 3, it can be seen that in the device pattern formed according to the present embodiment, inevitable random errors remain, but systematic errors are extremely small.

  FIG. 8 is a diagram illustrating a result of measuring a positional deviation of a device pattern by creating a photomask by a conventional method (comparative example) and a method according to the present embodiment (example). The comparative example is a photomask produced by the method shown in FIG. 1, and the example is a photomask produced by the method shown in FIGS. Here, twelve photomasks A to L are prepared for each of the example and the comparative example, and the arrangement accuracy (positional deviation) in the X and Y directions is measured. In FIG. 8, three times the standard deviation (3σ) is shown as the position accuracy. FIG. 8 shows that the positional accuracy is improved in the embodiment according to the present invention as compared with the comparative example.

  FIG. 9 is a diagram showing the result of simulating the interlayer overlay accuracy of the photomask created by the example according to the present invention and the conventional example. Here, the positional accuracy (3σ) when two photomasks A to L are selected and overlapped in order is shown. From FIG. 9, it can be seen that in the embodiment according to the present invention, the interlayer overlay accuracy is improved as compared with the conventional example.

(Second Embodiment)
10 and 11 are sectional views showing a photomask manufacturing method according to the second embodiment of the present invention. In the present embodiment, an example in which the present invention is applied to a binary photomask is described.

  First, as shown in FIG. 10A, a Cr film, for example, having a thickness of 0.07 μm is formed as a light shielding film 42 on a transparent substrate 41 made of quartz or the like. Thereafter, a positive photoresist film 43 is formed on the light shielding film 42 to a thickness of 0.4 μm, for example.

  Next, the dummy pattern formation region of the photoresist film 43 is selectively exposed using an electron beam drawing machine or a laser drawing machine. Thereafter, post-exposure baking (PEB) and development processing are performed, and as shown in FIG. 10B, the exposed portion (the portion corresponding to the dummy pattern) of the photoresist film 43 is removed. An opening 43a through which the light shielding film 42 is exposed is formed.

  Next, the light shielding film 42 is etched using the photoresist film 43 as a mask to form a dummy pattern 52 (an opening of the light shielding film 42) as shown in FIG. Thereafter, as shown in FIG. 10D, the photoresist film 43 is removed.

  After the dummy pattern 52 is formed on the substrate 41 in this way, the position shift using the coordinate position measuring device, that is, the position of the designed dummy pattern 52 and the position of the dummy pattern 52 actually formed on the substrate 41. Measure the deviation. In this case, it is preferable to measure the positional deviation of 100 or more places close to the device pattern formation region with respect to one photomask.

  After measuring the positional deviation of the dummy pattern 52 using the coordinate position measuring device, a system error is calculated, and the result is fed back to the drawing machine to adjust the correction parameters of the drawing machine.

  Next, as shown in FIG. 11A, a positive photoresist film 44 is formed to a thickness of 0.4 μm, for example, on the transparent substrate 41 formed up to the dummy pattern 52. Thereafter, a device pattern is drawn on the photoresist film 44 using the same drawing machine as that used to draw the dummy pattern 52.

  Next, post-exposure baking and development are performed to remove the photoresist film 44 from the exposed portion and form an opening 44a through which the light shielding film 42 is exposed, as shown in FIG. 11B. To do. Thereafter, as shown in FIG. 11C, the light shielding film 42 is dry-etched using the photoresist film 44 as a mask to form a device pattern 51 (an opening of the light shielding film 42). Next, as shown in FIG. 11D, the photoresist film 44 is removed. Thereafter, the position accuracy of the device pattern 51 is confirmed using a coordinate position measuring apparatus. In this way, a binary photomask is completed.

  Also in the present embodiment, the positional deviation of the dummy pattern 52 is measured, the result is fed back to the drawing machine, the correction parameters of the drawing machine are adjusted, and then the device pattern 51 is drawn. In addition, the systematic error caused by the drawing machine can be sufficiently reduced, and the interlayer overlay accuracy is also improved.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Additional remark 1) The 1st process of forming a light shielding film on a substrate,
A second step of forming a first pattern on the light shielding film using a drawing machine;
A third step of measuring positional accuracy of the first pattern;
A fourth step of adjusting the drawing machine according to the measurement result of the positional accuracy of the first pattern;
And a fifth step of forming a second pattern on the light-shielding film on which the first pattern is formed using the drawing machine adjusted in the fourth step.

  (Supplementary note 2) The photomask according to supplementary note 1, wherein the first pattern is a dummy pattern that does not constitute an electronic circuit, and the second pattern is a device pattern that constitutes an electronic circuit. Production method.

  (Supplementary Note 3) The second step includes a step of forming a first photoresist film on the light shielding film, and a region corresponding to the first pattern of the first photoresist film by the drawing machine. The method according to claim 1 or 2, further comprising: a step of exposing the first photoresist film; a step of developing the first photoresist film; and a step of etching the light-shielding film using the first photoresist film as a mask. The manufacturing method of the photomask as described.

  (Additional remark 4) The said 1st photoresist film is a positive photoresist film, The manufacturing method of the photomask of Additional remark 3 characterized by the above-mentioned.

  (Supplementary Note 5) The fifth step includes a step of forming a second photoresist film on the light shielding film, and a region corresponding to the second pattern of the second photoresist film by the drawing machine. And the step of developing the second photoresist film, and the step of etching the light-shielding film using the second photoresist film as a mask. The manufacturing method of the photomask of any one of Claims 1.

  (Additional remark 6) The said 2nd photoresist film is a positive photoresist film, The manufacturing method of the photomask of Additional remark 5 characterized by the above-mentioned.

(Appendix 7) The first step includes a step of forming a halftone phase shift layer on the substrate, and a step of forming the light shielding film on the halftone phase shift layer,
The second step includes a step of forming a first photoresist film on the light shielding film, a step of exposing a region corresponding to the first pattern of the first photoresist film by the drawing machine, Developing the first photoresist film, etching the light-shielding film using the first photoresist film as a mask, and etching the halftone phase shift layer using the light-shielding film as a mask Including
The fifth step includes a step of forming a second photoresist film on the light shielding film, a step of exposing a region corresponding to the second pattern of the second photoresist film by the drawing machine, The photomask according to claim 1 or 2, further comprising a step of developing the second photoresist film, and a step of etching the light shielding film using the second photoresist film as a mask. Production method.

  (Supplementary note 8) The method for manufacturing a photomask according to supplementary note 7, wherein the first and second photoresist films are both positive photoresist films.

  (Supplementary note 9) In the fourth step, a positional deviation of the first pattern is measured using a coordinate position measuring device, and a correction parameter of the drawing machine is adjusted based on the result. A method for producing the photomask according to 1 or 2.

1A to 1E are cross-sectional views showing an example of a conventional photomask manufacturing method in the order of steps. FIG. 2 is a diagram showing a result of measuring a positional deviation by drawing a test pattern using a drawing machine in which correction parameters are adjusted by a conventional method. FIG. 3 is a diagram illustrating a result of measuring a positional deviation by actually drawing a device pattern of a product chip using a drawing machine in which correction parameters are adjusted by a conventional method. FIG. 4 is a plan view showing an example of a photomask. FIG. 5 is a cross-sectional view (No. 1) showing the photomask manufacturing method according to the first embodiment of the present invention. FIG. 6 is a sectional view (No. 2) showing the photomask manufacturing method according to the first embodiment of the present invention. FIG. 7 is a diagram showing a result of actually drawing a product chip pattern on a photomask by using the method of the first embodiment and measuring a positional deviation of the device pattern. FIG. 8 is a diagram illustrating a result of measuring a positional deviation of a device pattern by creating a photomask by a conventional method (comparative example) and a method according to the present embodiment (example). FIG. 9 is a diagram showing a result of simulating the interlayer overlay accuracy of the photomasks created according to the example and the conventional example. FIG. 10 is a cross-sectional view (No. 1) showing the photomask manufacturing method according to the second embodiment of the present invention. FIG. 11 is a cross-sectional view (No. 2) showing the photomask manufacturing method according to the second embodiment of the present invention.

Explanation of symbols

11, 31, 41 ... transparent substrate,
12, 32 ... halftone phase shift layer,
13, 33, 42 ... light shielding layer,
14, 34, 35, 43, 44 ... photoresist film,
20 ... Photomask,
21, 51 ... device pattern,
22, 52 ... Dummy pattern.

Claims (5)

A first step of forming a light shielding film on the substrate;
A second step of forming a first pattern on the light shielding film using a drawing machine;
A third step of measuring positional accuracy of the first pattern;
A fourth step of adjusting the drawing machine according to the measurement result of the positional accuracy of the first pattern;
And a fifth step of forming a second pattern on the light-shielding film on which the first pattern is formed using the drawing machine adjusted in the fourth step.   2. The method of manufacturing a photomask according to claim 1, wherein the first pattern is a dummy pattern that does not constitute an electronic circuit, and the second pattern is a device pattern for constituting an electronic circuit.   The second step includes a step of forming a first photoresist film on the light shielding film, and a step of exposing a region corresponding to the first pattern of the first photoresist film by the drawing machine. 3. The photo of claim 1, further comprising: developing the first photoresist film; and etching the light shielding film using the first photoresist film as a mask. Mask manufacturing method.   The fifth step includes a step of forming a second photoresist film on the light shielding film, and a step of exposing a region corresponding to the second pattern of the second photoresist film by the drawing machine. And a step of developing the second photoresist film, and a step of etching the light-shielding film using the second photoresist film as a mask. The manufacturing method of the photomask of claim | item. The first step includes a step of forming a halftone phase shift layer on the substrate, and a step of forming the light shielding film on the halftone phase shift layer,
The second step includes a step of forming a first photoresist film on the light shielding film, a step of exposing a region corresponding to the first pattern of the first photoresist film by the drawing machine, Developing the first photoresist film, etching the light-shielding film using the first photoresist film as a mask, and etching the halftone phase shift layer using the light-shielding film as a mask Including
The fifth step includes a step of forming a second photoresist film on the light shielding film, a step of exposing a region corresponding to the second pattern of the second photoresist film by the drawing machine, 3. The photomask according to claim 1, further comprising: developing the second photoresist film; and etching the light-shielding film using the second photoresist film as a mask. Manufacturing method.

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