• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A phase shifting mask can be used with exposure lights of two different wavelengths. The depth of the phase shifting layer is calculated and fabricated such that it shifts a first exposure light about 180° and a second exposure light about 180°.
    公开号:US20010001693A1
    申请号:US09/732,816
    申请日:2000-12-08
    公开日:2001-05-24
    发明作者:Christophe Pierrat；J. Rolfson
    申请人:Micron Technology Inc；
    IPC主号:G03F1-30
    专利说明:
    [0002] The present invention relates to processes for creating photomasks or reticles used in the fabrication of semiconductor devices. More particularly, the present invention relates to phase shifting photomasks and processes for designing them. [0002]
    [0003] Advances in capacity in semiconductor chips have generally been the result of decreases in the size of the features on the chip. The lateral dimensions of features are generally defined by photolithographic techniques in which a detailed pattern is transferred to a photoresist by shining light through a mask or reticle. [0003]
    [0004] In recent years, phase shifting masks have been developed to improve photolithographic processes. Phase shifting masks increase image contrast and resolution without reducing wave length or increasing numerical aperture. These masks also improve depth of focus and process latitude for a given feature size. [0004]
    [0005] With phase shift photolithography, the interference of light rays is used to overcome the problems of diffraction and improve the resolution and depth of optical images projected onto a target. With this technology, the phase of the exposure light at the target is controlled such that adjacent bright areas are preferably formed 180° out of phase with each other. Dark regions are thus produced between the bright areas by destructive interference even when diffraction would otherwise cause these areas to be lit. This technique improves total resolution at the target. [0005]
    [0006] In general, a phase shifting mask is constructed with a repetitive pattern formed of three distinct layers. An opaque layer provides areas that allow no light transmission. A first transparent layer provides areas which allow close to 100% of the light to pass through. A transparent phase shifting layer provides areas which allow close to 100% of the light to pass through but phase shifted 180 degrees from the light passing through the first transparent layer. The first transparent layer and the phase shifting layer are positioned such that light rays diffracted through each area are cancelled out in a darkened area between them. This creates a pattern of dark and bright areas which can be used to clearly delineate features of a pattern defined by the opaque layer on the semiconductor wafer. Another method of constructing a phase shifting mask utilizes a semitransparent layer to cause the phase shift. [0006]
    [0007] One process for fabricating phase shifting masks includes forming an opaque layer on a major surface of a transparent substrate, patterning the opaque layer to expose portions of the underlying transparent substrate, forming a phase shifting mask layer to expose the portions of the underlying transparent substrate, phase-etching the exposed portions of the transparent substrate until a 180° phase shift is accomplished. Other processes of fabricating phase shifting masks include those in which a transparent film is formed over a portion of a mask to create a phase shift as well as the etching of phase shifting channels into the mask substrate. [0007]
    [0008] Phase shifting masks are considerably more difficult to design and fabricate than conventional photomasks. Accordingly, it is desirable to fabricate phase shifting masks which will have as long a useful life as possible and which are capable of being used under varying exposure conditions. One of the problems associated with current phase shifting masks is that they must be designed for use with a specific type of stepper. [0008]
    [0009] Accordingly, it would be a significant advancement in the art to provide a photomask and method of fabrication wherein the photomask could be used with different types of steppers. It would be further advancement if such a photomask could be used with steppers having different wave lengths. [0009] BRIEF SUMMARY OF THE INVENTION
    [0010] The present invention provides a phase shifting photomask that can be used with steppers having different wave lengths of exposure light. The present invention also provides a method for designing such a phase shifting photomask. [0010]
    [0011] In a preferred embodiment of the present invention, a phase shifting mask layout is designed and etched using conventional techniques. The depth of the etch for the phase shifting portion is calculated and etched such that exposure light of two different wavelengths will each have a phase shift of about 180°. [0011] BRIEF DESCRIPTION OF THE DRAWINGS
    [0012] FIG. 1 is a schematic cross-sectional view of a portion of a phase shifting mask according to the present invention. [0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
    [0013] The present invention provides a phase shifting photomask which can be used with different wave lengths of light. The invention is best understood by reference to the attached drawing in connection with the following description. [0013]
    [0014] Referring first to FIG. 1, a portion of a phase shifting mask [0014] 10 is illustrated in cross-section. Mask 10 includes a quartz substrate 12 with a chrome layer 14 formed thereon. A plurality of apertures 16 and 18 are formed in chrome layer 14. Apertures 16 expose the surface of quartz substrate 12. Apertures 18 expose portions of quartz substrate 12 which have been etched to a depth d to create a phase shifting layer 22. Mask 10 is designed and fabricated using tools and techniques well known to those skilled in the art of mask design.
    [0015] Mask [0015] 10 is designed such that light having a wave length of either λ1 or λ2 can be used. As the light passes through apertures 16 it has a phase of φ1. As the light passes through apertures 18, both wave lengths λ1 and λ2 have a phase of φ2. The depth d of the etch in the quartz is such that
    [0016] wherein λ equals the wave length of the light and φ equals phase of the light and k is an integer. Mask [0016] 10 will behave like an alternating aperture phase shifting mask for both λ1 and λ2 wave lengths.
    [0017] In order to design a phase shifting mask whereby a 180° phase shift is obtained at a first wave length and a 180° phase shift is obtained at a second wave length, it is necessary to find a common depth for the phase shifting layer [0017] 22 which will produce the desired phase shifts. This can be accomplished by using the formula
    [0018] [0018]   d=iλ/2(n−1)  (5)
    [0019] [0019]
    [0020] wherein d equals depth of the etch, i equals an odd number for a 180° phase shift and an even number for a 0° phase shift, λ equals the wave length of exposure light and n equals the refractive index of the material the light travels through. Setting d to be approximately equal for two different wave lengths results in the following equation [0020] i 1  λ 12  ( n 1 - 1 )≈i 2  λ 22  ( n 2 - 1 )( 6 )
    [0021] since λ[0021] 1, λ2, n1 and n2 are known quantities, i2 can be expressed as a function of i1 i 2 ≈ i 1  λ 1( n 1 - 1 ) · ( n 2 - 1 ) λ 2( 7 )
    [0022] This equation can be solved for various wave lengths and substrate materials. For example, for an i-line process with a quartz substrate, an etch depth of 3850 Å produces a shift of 180° such that n[0022] 365 equals 1.474. For a deep UV process at 248 nm, a 2440 Å quartz etch shifts the light 180° resulting in n248 equals 1. 508. Substituting these values into equation 5, results in
    [0023] [0023]   i 2 ≈i 1(1.5773)  (8)
    [0024] [0024]
    [0025] A table can be created to help determine an appropriate value for i[0025] 1 and i2. Using the values from equation 8 results in the following table: i1 i2  1  1.5773  3  4.7319  5  7.8865  7 11.0411  9 14.1957 11 17.3503
    [0026] From this table it is apparent that at i[0026] 1 equals 7, i2 is approximately equal to an odd integer, in this case 11.
    [0027] Using a value of 7 for i[0027] 1, it is possible to calculate a depth for the phase shifting layer which will produce a 180° phase shift for λ1 and an approximately 180° phase shift for λ2. Using a value of i2 equals 11 it is possible to obtain a depth which will produce a 180° phase shift for λ2 and an approximately 180° phase shift for λ1. In order to obtain a mask which works equally well at both wave lengths, the difference in the depths could be averaged. For it equals 7, d equals 26950 Å. For i2 equals 11, d equals 26840 Å. Since a phase change at 248 nm requires 0.634 as much depth as an equal phase change at 365 nm the compromise depth can be calculated as follows:
    [0028] 26950+(0.634) (26850−26950)=26887 Å  (7)[0028]  
    [0029] [0029]
    [0030] Thus, a quartz mask having a phase shifting layer about 26890 Å deep can be used with an i-line exposure at 365 nm and a deep UV exposure at 248 nm. It will be appreciated by those skilled in the art that similar calculations can be performed to design a mask fabricated from other substrate materials or a mask to be used with different exposure lights. Additional substrate materials that have been used for photomasks include borosilicate glass and soda-lime glass. Other exposure lights include g-line at 436 nm and h-line at 405 nm. [0030]
    [0031] While the invention has been described with respect to the presently preferred embodiments, it will be appreciated by those skilled in the art that modifications and changes can be made to the present invention without departing from its spirit or essential characteristics. For example, this process can be used with additive phase shifting masks as well as subtractive phase shifting masks. Accordingly, all modifications or changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. [0031]
    权利要求:
    Claims (24)
    [1" id="US-20010001693-A1-CLM-00001] 1. A phase shifting mask including a phase shifting layer shifting a first exposure light having a first wavelength about 180° and shifting a second exposure light having a second wavelength about 180°.
    [2" id="US-20010001693-A1-CLM-00002] 2. A phase shifting mask as defined in
    claim 1 wherein said first exposure light has a wavelength of about 365 nm.
    [3" id="US-20010001693-A1-CLM-00003] 3. A phase shifting mask as defined in
    claim 1 wherein said second exposure light has a wavelength of about 248 nm.
    [4" id="US-20010001693-A1-CLM-00004] 4. A phase shifting mask as defined in
    claim 1 wherein said first exposure light has a wavelength of about 365 nm and second exposure light has a wavelength of about 248 nm.
    [5" id="US-20010001693-A1-CLM-00005] 5. A phase shifting mask as defined in
    claim 1 wherein said mask comprises a quartz substrate.
    [6" id="US-20010001693-A1-CLM-00006] 6. A phase shifting mask as defined in
    claim 1 wherein said phase shifting layer is etched into the mask surface.
    [7" id="US-20010001693-A1-CLM-00007] 7. A phase shifting mask as defined in
    claim 6 wherein said phase shifting layer has a depth of about 26890 Å.
    [8" id="US-20010001693-A1-CLM-00008] 8. A phase shifting mask as defined in
    claim 1 wherein said phase shifting layer is added to said mask surface.
    [9" id="US-20010001693-A1-CLM-00009] 9. A phase shifting mask as defined in
    claim 8 wherein said phase shifting layer has a thickness of about 26890 Å.
    [10" id="US-20010001693-A1-CLM-00010] 10. A phase shifting mask as defined in
    claim 1 wherein said phase shifting mask comprises a quartz substrate, said first exposure light has a wavelength of about 365 nm, said second exposure light has a wavelength of about 248 mn and said phase shifting layer has a depth of about 26890 Å.
    [11" id="US-20010001693-A1-CLM-00011] 11. A phase shifting mask formed from a quartz substrate having a surface including a phase shifting layer shifting a first exposure light having a wave length of about 365 nm about 180° and shifting a second exposure light having a wavelength of about 248mm about 180°.
    [12" id="US-20010001693-A1-CLM-00012] 12. A phase shifting mask as defined in
    claim 11 wherein said phase shifting layer is etched into said surface.
    [13" id="US-20010001693-A1-CLM-00013] 13. A phase shifting mask as defined in
    claim 11 wherein said phase shifting layer is added to said surface.
    [14" id="US-20010001693-A1-CLM-00014] 14. A phase shifting mask used in the manufacture of semiconductors, said mask including a phase shifting layer having a depth shifting a first exposure light having a first wavelength and a second exposure light having a second wavelength approximately the same amount.
    [15" id="US-20010001693-A1-CLM-00015] 15. A method of creating a photomask that can be used with exposure lights having different wavelengths comprising:
    patterning an opaque layer on a surface of a transparent substrate to create transmitting and nontransmitting portions; and
    creating a phase shifting layer shifting the phase of a first exposure light having a first wavelength about 180° and shifting a second exposure light having a second wavelength about 180°.
    [16" id="US-20010001693-A1-CLM-00016] 16. A method of creating a phase shifting mask as defined in
    claim 15 wherein said phase shifting layer is etched into said substrate.
    [17" id="US-20010001693-A1-CLM-00017] 17. A method of creating a phase shifting mask as defined in
    claim 16 wherein said phase shifting layer has a depth of about 26890 Å.
    [18" id="US-20010001693-A1-CLM-00018] 18. A method of creating a phase shifting mask as defined in
    claim 15 wherein said phase shifting layer is added to the surface of said substrate.
    [19" id="US-20010001693-A1-CLM-00019] 19. A method of creating a phase shifting mask as defined in
    claim 18 wherein said phase shifting layer has a thickness of about 26890 Å.
    [20" id="US-20010001693-A1-CLM-00020] 20. A method of creating a phase shifting mask as defined in
    claim 15 wherein said transparent substrate comprises quartz.
    [21" id="US-20010001693-A1-CLM-00021] 21. A method of creating a phase shifting mask as defined in
    claim 15 wherein said first exposure light has a wavelength of about 365 nm.
    [22" id="US-20010001693-A1-CLM-00022] 22. A method of creating a phase shifting mask as defined in
    claim 15 wherein said second exposure light has a wavelength of about 248 nm.
    [23" id="US-20010001693-A1-CLM-00023] 23. A method of creating a phase shifting mask as defined in
    claim 15 wherein said first exposure light has a wavelength of about 365 nm and said second exposure light has a wavelength of about 248 nm.
    [24" id="US-20010001693-A1-CLM-00024] 24. A method of creating a phase shifting mask as defined in
    claim 15 wherein said first exposure light has a wavelength of about 365 nm, said second exposure light has a wavelength of about 248 nm and said phase shifting layer has a depth of about 26890 Å.
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    同族专利:
    公开号 | 公开日
    US5876878A|1999-03-02|
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    US6558854B2|2003-05-06|
    US6068951A|2000-05-30|
    引用文献:
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    US20130122428A1|2011-11-16|2013-05-16|Samsung Display Co., Ltd.|Exposure system, method of forming pattern using the same and method of manufacturing display substrate using the same|
    KR20180104589A|2018-09-06|2018-09-21|삼성디스플레이 주식회사|Exposure system, method of forming pattern and method of manufacturing display substrate using the same|CA1313792C|1986-02-28|1993-02-23|Junji Hirokane|Method of manufacturing photo-mask and photo-mask manufactured thereby|
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    DE59010548D1|1990-04-09|1996-11-28|Siemens Ag|Phase mask for projection photolithography and process for its manufacture|
    JP2723405B2|1991-11-12|1998-03-09|松下電器産業株式会社|Method of forming fine electrodes|
    US5308722A|1992-09-24|1994-05-03|Advanced Micro Devices|Voting technique for the manufacture of defect-free printing phase shift lithography|
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    US7157191B2|2004-01-12|2007-01-02|Taiwan Semiconductor Manufacturing Co., Ltd.|Single trench repair method with etched quartz for attenuated phase shifting mask|
    US8318536B2|2007-12-31|2012-11-27|Intel Corporation|Utilizing aperture with phase shift feature in forming microvias|
    法律状态:
    2006-10-13| FPAY| Fee payment|Year of fee payment: 4 |
    2007-01-30| AS| Assignment|Owner name: MICRON TECHNOLOGY, INC., IDAHO Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:PIERRAT, CHRISTOPHE;ROLFSON, J. BRETT;REEL/FRAME:018826/0061;SIGNING DATES FROM 19960628 TO 19960701 |
    2010-10-06| FPAY| Fee payment|Year of fee payment: 8 |
    2014-12-12| REMI| Maintenance fee reminder mailed|
    2015-05-06| LAPS| Lapse for failure to pay maintenance fees|
    2015-06-01| STCH| Information on status: patent discontinuation|Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
    2015-06-23| FP| Lapsed due to failure to pay maintenance fee|Effective date: 20150506 |
    优先权:
    申请号 | 申请日 | 专利标题
    US08/679,835|US5876878A|1996-07-15|1996-07-15|Phase shifting mask and process for forming comprising a phase shift layer for shifting two wavelengths of light|
    US09/229,616|US6068951A|1996-07-15|1999-01-13|Phase shifting mask and process for forming|
    US09/550,765|US6162568A|1996-07-15|2000-04-17|Process for forming features on a semiconductor wafer using a phase shifting mask that can be used with two different wavelengths of light|
    US09/732,816|US6558854B2|1996-07-15|2000-12-08|Process for forming features on a semiconductor wafer using a phase shifting mask that can be used with two different wavelengths of light|US09/732,816| US6558854B2|1996-07-15|2000-12-08|Process for forming features on a semiconductor wafer using a phase shifting mask that can be used with two different wavelengths of light|
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