In recent years, along with miniaturization of semiconductor elements, in order to overcome the resolution limit of optical systems, micromachining technology using electron beams, ion beams, and other charged particle beams to draw circuit patterns have been developed
In the conventional so-called direct drawing type electron beam exposure method, the finer the pattern, the larger the data scale, the longer the drawing time, and the lower the productivity as a result. For this reason, an electron beam/ion beam exposure apparatus for focusing an electron beam/ion beam on a transfer mask having predetermined patterns so as to form patterns on a wafer is known.
As these technology, for example electron beam projection lithography (EPL) (refer to for example H. C. Pfeiffer, Jpn. J. Appl. Phys. 34, 6658 (1995)), low energy electron beam proximity projection lithography (LEEPL) (refer to for example T. Utsumi, U.S. Pat. No. 5,831,272 (Nov. 3, 1998)), or ion projection lithography (IPL) (refer to for example H. Loeschner et al., Vac. SciTechnol. B19, 2520 (2001)), etc. are known.
An electron beam transmission mask used in the above-explained exposure apparatus is for example a stencil mask comprised of a thin film (also referred to as a “membrane”) having a thickness of about 100 nm to 10 μm having a pattern of openings formed in it.
However, since holes are made in the membrane, there are patterns which cannot be formed or are hard to be formed such as donut-shaped patterns (whose center portions drop off) and a leaf patterns (of cantilever structures, so unstable).
Further, where using a very thin membrane, it suffers from the disadvantage that forming holes in the membrane cause changes in the state of internal stress and changes in the pattern shapes.
For this reason, in order to prepare a stencil mask used in a charged particle beam exposure apparatus, a data processing apparatus and method having new functions different from conventional data processing for a mask using light have been demanded.
The present invention was made in consideration with such circumstances and has as an object thereof to provide a mask processing apparatus, a mask processing method, a program and a mask able to easily prepare a mask used in a charged particle beam exposure apparatus.
To achieve the above object, a mask processing apparatus of a first aspect of the present invention provides a mask processing apparatus generating complementary stencil mask data, having a complementary dividing means for complementarily dividing design data for each predetermined processing unit to generate complementarily divided patterns based on the design data and mask characteristic data indicating at least the characteristics of the complementary stencil masks and a mask data generating means for generating the complementary stencil mask data based on the complementarily divided patterns generated by the complementary dividing means and mask characteristic data.
According to the mask processing apparatus of the first aspect of the present invention, the complementary dividing means complementarily divides the design data for each predetermined processing unit to generate complementarily divided patterns based on the design data and mask characteristic data indicating at least the characteristics of the complementary stencil masks.
The mask data generating means generates the complementary stencil mask data based on the complementarily divided patterns generated by the complementary dividing means and the mask characteristic data.
Further, to achieve the above object, a mask processing method according to a second aspect of the present invention provides a mask processing method of a mask processing apparatus for generating complementary stencil mask data, including a first step of complementarily dividing design data for each predetermined processing unit to generate complementarily divided patterns based on the design data and mask characteristic data indicating at least the characteristics of complementary stencil masks and a second step of generating complementary stencil mask data based on the complementarily divided patterns generated in the first step and the mask characteristic data.
Further, to achieve the above object, a mask processing method according to a third aspect of the present invention provides a mask processing method of a mask processing apparatus for generating complementary stencil mask data, comprising a first step of complementarily dividing design data for each predetermined processing unit to generate complementarily divided patterns based on design data and mask characteristic data including at least beam position data of beams and device characteristic data concerning the characteristic of a stencil mask generation device for generating complementary stencil masks and indicating the characteristics of the complementary stencil masks, a second step of generating membrane data for drawing the shape of the membrane in the complementary stencil masks based on the design data and the mask characteristic data, a third step of arranging the complementarily divided patterns at predetermined positions of the stencil mask based on the complementarily divided patterns generated for each predetermined processing unit by the first step and the mask characteristic data, a fourth step of verifying whether or not defect patterns have been generated on the complementary stencil masks based on the complementarily divided patterns arranged at the third step, a fifth step of performing displacement correction processing on the complementarily divided patterns using internal stress of the membrane in the complementary stencil masks, a sixth step of performing the displacement correction processing for the complementarily divided patterns using the mechanical characteristics of a mask member of the complementary stencil masks, a seventh step of verifying whether or not the complementarily divided patterns coincide with patterns in the design data by a plurality of exposures, an eighth step of performing the displacement correction processing on the complementarily divided patterns using front/back inversion of the complementary stencil masks to generate complementary stencil mask data, a ninth step of verifying whether or not the complementarily divided patterns coincide with patterns in the design data based on the complementary stencil mask data generated by the eighth step and the design data, and a 10th step of generating drawing membrane data for making the stencil mask generation device draw the membrane and draw the complementarily divided patterns in the membrane based on the membrane data, the complementary stencil mask data, and the device characteristic data.
Further, to achieve the above object, a program according to a fourth aspect of the present invention provides a program to be executed by an information processing apparatus comprising a first routine of complementarily dividing design data for each predetermined processing unit to generate complementarily divided patterns based on the design data and mask characteristic data indicating at least the characteristics of complementary stencil masks and a second routine of generating complementary stencil mask data based on the complementarily divided patterns generated at the first routine and the mask characteristic data.
Further, to achieve the above object, a program according to a fifth aspect of the present invention provides a program to be executed by an information processing apparatus comprising a first routine of complementarily dividing design data for each predetermined processing unit to generate complementarily divided patterns based on the design data and mask characteristic data including at least beam position data of beams and device characteristic data concerning the characteristics of a stencil mask generation device for generating the complementary stencil masks and indicating the characteristics of the complementary stencil masks, a second routine of generating membrane data for drawing the shape of the membrane in the complementary stencil masks based on the design data and the mask characteristic data, a third routine of arranging the complementarily divided patterns at predetermined positions of the stencil mask based on the complementarily divided patterns generated for each predetermined processing unit by the first routine and the mask characteristic data, a fourth routine of verifying whether or not a defect pattern is generated on the complementary stencil masks based on the complementarily divided patterns arranged in the third routine, a fifth routine of performing displacement correction processing on the complementarily divided patterns using internal stress of the membrane in the complementary stencil masks, a sixth routine of performing displacement correction processing on the complementarily divided patterns using mechanical characteristics of a mask member of the complementary stencil masks, a seventh routine of verifying whether or not the complementarily divided patterns coincide with patterns in the design data by a plurality of exposures, an eighth routine of generating the complementary stencil mask data by performing displacement correction processing on the complementarily divided patterns using front/back inversion of the complementary stencil masks, a ninth routine of verifying whether or not the complementarily divided patterns coincide with patterns in the design data based on the complementary stencil mask data generated by the eighth routine and the design data, and a 10th routine of generating drawing membrane data for making the stencil mask generation device draw the membrane and draw the complementarily divided patterns in the membrane based on the membrane data, the complementary stencil mask data, and the device characteristic data.
Further, to achieve the above object, the sixth aspect of the present invention is generated based on the complementary stencil mask data generated by the mask processing apparatus.
Further, to achieve the above object, the seventh aspect of the present invention is generated by the stencil mask generation device based on the drawing membrane data and the drawing pattern data generated by the mask processing apparatus.
A mask processing system 100 has, for example as shown in
The mask processing apparatus 1, design processing device 2, mask preparation processing device 3, mask preparation device 4, exposure processing device 5, and exposure apparatus 6 are connected by a communication network NET7. The mask processing apparatus 1 corresponds to the mask processing apparatus and the information processing device according to the present invention. The mask preparation processing device 3 and the mask preparation device 4 correspond to the stencil mask generation device according to the present invention.
The design processing device 2 generates for example desired design data of a semiconductor integrated circuit and outputs the same via the communication network NET7 to the mask processing apparatus 1.
The mask processing apparatus 1 generates complementary stencil mask data, in more detail, drawing membrane data, drawing pattern data, etc. explained later based on for example the design data output from the design processing device 2, the mask characteristic data indicating the characteristics of the stencil mask including device characteristic parameters concerning the mask preparation device 4, device characteristic parameters concerning the exposure apparatus 6, etc., and outputs the same via the network NET7 to the mask preparation processing device 3.
The mask preparation processing device 3 controls the mask preparation device 4 to make the mask preparation device 4 actually generate a desired mask based on the drawing membrane data and the drawing pattern data etc. output from the mask processing apparatus 1.
The exposure processing device 5 controls the exposure apparatus 6 in accordance with a predetermined exposure processing step.
The exposure apparatus 6 emits for example a low energy electron beam via the complementary stencil masks generated at the mask preparation device 4 under the control of the exposure processing device 5 to expose circuit patterns in accordance with the desired design data onto the wafer. The circuit patterns on the wafer are etched by a not illustrated etching device, whereby desired circuit patterns are generated. For example, in the exposure apparatus 6 of the present embodiment, when using a low energy electron beam, a gap of about 50 μm is provided between the wafer and the mask, and the mask is exposed at equal magnification.
At this time, the electron beam cannot pass through the object, therefore use is made of a for example silicon (Si), diamond, or SiC stencil mask having holes formed in the mask.
For example, in the case of design data n1 as shown in
Further, a leaf pattern n12 as shown in
On the other hand, in the mask processing system 100 according to the present embodiment, in the case of the design data n1 as shown in
Further, for example a donut pattern n11 shown in
Further, the leaf pattern n12 shown in
For example, the mask processing system 100 uses a complementary beam (strut) mask giving a beam (strut) structure to realize the required precision of this complementary division, the formation of the mask, and the exposure and prevent the distortion and breakage of the mask due to a thin membrane.
For example, the pattern n101 in the design data n100 shown in
The pattern n101 in the design data n100 as shown in
Complementary stencil masks come in a plurality of types according to the beam positions and the layout positions of the membrane so as to satisfy predetermined conditions. For example, the first complementary stencil mask c1 is a mask in which beams are formed at predetermined positions in lattices in each of four sections as shown in
Below, an explanation will be given of the first complementary stencil mask c1 (COSMOS-I) shown in
As shown in
The beams c4 are the parts remaining after forming a plurality of openings in the silicon wafer c2. Terminal ends of all beams c4 are connected to the frame or other beams c4. There is no portion where the beams c4 are disconnected.
Below, a square portion of the membrane c3 surrounded by the beams c4 will be defined as a “membrane divided region c5”. The beams c4 are provided with skirts of narrow widths parallel to the beams c4 at the membranes c3 at the two sides. In the membrane divided region c5, the part except the skirts will be defined as the “pattern region”. Further, a part combining the beams c4 and the skirts will be defined as a “beam zone”.
Next, an explanation will be given of the layout of the beams in the stencil mask shown in
Assuming that the center of the silicon wafer c2 shown in
The membrane c3 does not strictly have to be a square shape. So long as the sections I to IV have rectangular shapes having the x-axis and the y-axis as two sides or shapes near that, the lengths of all sides of sections I to IV do not have to completely coincide.
In each of sections I to IV, a plurality of beam zones c6 are arranged at equal intervals parallel to the x-axis. In the same way, a plurality of beam zones c6 are arranged in the sections I to IV at equal intervals parallel to the y-axis. The beams c4 of
In the x-axis direction, the positions of the beam zones c6 parallel to the x-axis do not coincide between the adjacent section I and section II or between section III and section IV. In the same way, in the y-axis direction, the positions of the beam zones c6 parallel to the y-axis do not coincide between the adjacent section I and section IV or between section II and section III.
Among the four sections I to IV, the beam zones c6 contact both of the x-axis and the y-axis in only one set of sections on a diagonal line of the membrane c3. As shown in
The beam zone c6 is arranged at a boundary portion between the section III and the section II (portion contacting the x-axis) existing on the diagonal line together with the section I, and the beam zone c6 is arranged at a boundary portion between, the section III and the section IV (portion contacting the y-axis).
Alternatively, in
In the example shown in
The interval between the beam zones c6, that is, the length of one side of a pattern region c7, is preferably a whole multiple of 3 or more when for example the width of the beam zone is 1.
The membrane c3 of the stencil mask c1 is for example formed with holes c8 corresponding to the patterns as shown in
The stencil mask c1 is arranged so that the surface on the membrane c3 side becomes close to the wafer surface to which the patterns are transferred. When the stencil mask c1 is scanned by the electron beam from the frame c9 side, the electron beam passes through only the parts of the holes c8 so the patterns are transferred onto the resist on the wafer.
The stencil mask c1 according to the present embodiment cannot form holes 8 in the beam 4 parts. Accordingly, as explained above, the pattern is complementarily divided, and complementary patterns are formed in the sections I to IV shown in
As explained above, when using the stencil mask c1 for exposure, first the stencil mask c1 and the wafer are fixed in place and the patterns of sections I to IV shown in
After moving the wafer, the stencil mask c1 is again scanned by the electron beam. By repeating the above steps, multiple exposure is carried out four times so that the patterns of the four sections I to IV of the stencil mask c1 overlap. By this, patterns existing at the portions of the beams c4 are also complementary transferred to the resist.
The membrane c3 is divided to membrane divided regions c5 by the beams c4 as shown in
In the membrane divided region c5, the outside portion of the pattern region c7 corresponds to the skirts c11. The portions formed by combining the beams c3 and the skirts c11 on both sides thereof correspond to the beam zones c6 shown in
As shown in
Below, an explanation will be given of the margin c12 and the blank c13. When patterns do not completely fit in the pattern region c7, in principle holes 8 corresponding to patterns of the projecting portions are formed in other sections among the four sections I to IV of the stencil mask. The patterns are stitched together by multiple exposure.
However, when patterns project out from the pattern region c7 just a little, it is more advantageous if the patterns can be transferred without division by stitching the complementary patterns to one of the other sections I to IV. Especially, when a fine pattern having a particularly narrow line width, for example, a gate of a transistor, slightly projects out from the pattern region c7, if divided to complementary patterns, there is a high possibility of lowering the characteristics of the produced semiconductor device.
Therefore, the margin c12 enabling formation of holes c8 is provided on the periphery of the pattern region c7. The width W12 of the margin c12 can be freely set, but when the width W12 is made large, the original region for the patterns, that is, the pattern region c7, becomes smaller. Accordingly, the width W12 is set to for example about a few μm to tens of μm.
For example, according to the LEEPL, it is possible to finely change an incident angle α of the electron beam with respect to the stencil mask. The range of the incident angle α of the electron beam is usually about 0 to 10 mrad. When using an 8 inch wafer to form the stencil mask, the height H4 of the beams c4 becomes the 725 μm thickness of the 8-inch silicon wafer.
As shown in
W13=10×10−3 (rad)×H(μm)=7.25 (μm)≈7(μm)
As described above, a hole c8 is not formed in a portion A formed by combining the beam c4 and the blank c13 on both sides.
The mask processing apparatus 1 according to the present embodiment provides routines of mask data processing able to handle for example the above-mentioned beam stencil mask 1c. In more detail, the mask processing apparatus 1 prepares the device characteristic data of the used exposure apparatus 6 based on the design data prepared at the design processing device 2 and the complementary stencil mask data, in more detail the data for drawing the mask based on parameters describing information such as the mask characteristic data of the mask etc.
The mask processing apparatus 1 has, for example as shown in
The input portion 11, output portion 12, I/F 13, RAM 14, memory unit 15, and the CPU 16 are connected by a bus BS.
The input portion 11 outputs desired input data to the CPU 16. For example, the input portion 11 is a data input device such as a keyboard or mouse, CDROM (R, RW) drive, and floppy (registered trademark) disk drive (FD). For example, the input portion 11 may input design data, mask data etc. as the input data.
The output portion 12 performs the output in accordance with the predetermined output data output from the CPU 16. For example, the output portion 12 is a display device such as display and performs a display in accordance with the output data output from the CPU 16.
Through the interface (I/F) 13 desired data is transferred to the other information processing devices, for example, the design processing device 2, mask preparation processing device 3, and the exposure processing device 5 under the control of the CPU 16. As explained above, the I/F 13 may receive the design data output from the design processing device 2 as well.
The RAM 14 is used as a work space when performing for example predetermined processing by the CPU 16. The memory unit 15 is written with or read for the desired data by the CPU 16.
The memory unit 15 has for example a program 150, design data 151, parameters 152, etc.
The program 150 includes for example processing routines concerning the mask processing according to the present embodiment and executed by the CPU 16 by using the RAM 14 as the work space.
The design data 151 is the design data of for example the circuits formed on the wafer.
The parameters 152 include for example the device characteristic data of the mask preparation device 4, the device characteristic data of the exposure apparatus 6, and the mask characteristic data of the complementary stencil masks. For example, the parameters 152 include parameters indicating the type of processing of the exposure apparatus 6, mask information, for example, data indicating the material of the mask and mask process, and the map data (layout data) of the mask.
The CPU 16 performs for example processing based on the processing routines concerning the mask processing in accordance with the programs 150.
The CPU 16 has, for example as shown in
The alignment mark generation unit 1601 generates alignment marks d1601 based on the design data 151 and the parameter 152. For example, in detail, the alignment mark generation unit 1601 generates mask alignment marks d16011 and wafer alignment marks d16012 based on the data design data 151 and the parameters 152.
The mask alignment marks d16011 are mask alignment marks d16011 for the mask, while the wafer alignment marks d16012 are wafer alignment marks patterned on the wafer for use in alignment of the step explained later.
For example, when multiply exposing a mask complementarily divided like in the LEEPL, it is necessary to position the mask c1 and the wafer wf3 with a high precision. For this reason, for example, the die alignment system is used for positioning by measuring the scattered light of irradiated white light.
In more detail, for example as shown in
White light lt4 is irradiated from an oblique direction, for example, obliquely at 40 degrees with respect to the plane of the mask c1 and the wafer wf3, relative positions of the mask c1 and the wafer wf3 are measured from peak positions of signals of the scattered light and reflected light 1t5 at the mask alignment marks d16011 provided in the mask c1 and the wafer alignment marks d16012 provided in the wafer wf3, deviations from desired positions are measured, and position correction processing is carried out for each exposure (shot) based on the measured deviation information.
At this time, based on the scattered light and the reflected light 1t5 at the mask alignment marks d16011 and the wafer alignment marks d16012, offset, rotation, magnification, etc. are measured for each shot, the gap between the mask c1 and the wafer wf3 is measured, and position correction processing is carried out based on the measurement results.
As explained above, the mask alignment marks d16011 and the wafer alignment marks d16012 are referred to when multiply exposing the wafer wf3 by using the mask c1 by the exposure apparatus 6, therefore the alignment mark generation unit 1601 designs the layout of the mask alignment marks d16011 and the wafer alignment marks d16012 based on the parameters 152 including the device characteristic data of the exposure apparatus 6 etc.
As schematically shown in
The membrane shape design unit 1602 generates a predetermined membrane shape based on the design data 151, parameters 152, and the alignment marks d1601 output from the alignment mark generation unit 1601.
The membrane shape design unit 1602 designs the data concerning the membranes (COSMOS-I and II) based on the type of the complementary mask (for example COSMOS-I and II) included in the parameters 152 and information such as the chip size included in the design data 151 and outputs the data for generating the membrane to the data conversion unit 1613.
In more detail, the membrane shape design unit 1602 generates data for designing the membrane c3 in accordance with the COSMOS mask when arranging a square (1 cm □ having a chip size of 1 cm in the mask as shown in for example
Further, the membrane shape design unit 1602 generates data for designing the membrane in accordance with the second complementary stencil mask as shown in
The widths of the beam c4 and the membrane c3 differ according to the material used for the stencil masks c1 and c22, mask process, etc. For this reason, the membrane shape design unit 1602 determines the widths etc. of the beams c4 and the membrane c3 based on the data concerning the material used for the stencil mask c1 included in the parameters 152, the mask process, etc.
In the present embodiment, the width of the beams of the COSMOS-I shown in
The PUF and boundary processing unit 1603 performs the PUF division processing and boundary processing based on the design data 151, the parameters 152, and the alignment marks d1601.
The complementary masks c1 and cc2 are constituted by arranging the COSMOS unit fields (CUF) in an array.
In the first complementary mask (COSMOS-I) c1, for example as shown in
For example, in more detail, as shown in
However, in the first and second complementary masks, the mask shapes differ as shown in
The PUF and boundary processing unit 1603 performs the layout of the mask after the complementary division processing based on a map in accordance with the mask shape after the-end of the complementary division in the present embodiment, therefore divides the processing unit at this time to processing unit fields (hereinafter referred to as PUFs) having a size matching with any of the plurality of mask shapes and performs the complementary division processing for each PUF. Due to this, the processing of complex complementary masks can be accomplished with a simple complementary division function.
For example, in the present embodiment, the PUF is a region obtained by dividing the CUF of COSMOS-II shown in
The PUF and boundary processing unit 1603 divides the input design data (chip data) 151 to PUF sizes in order to perform the processing by a PUF. Further, the PUF and boundary processing unit 1603 performs the boundary processing for performing this PUF division.
The boundary processing simply performs the complementary division processing for each PUF for the predetermined pattern. When combining the results of the complementary division processing, sometimes a disadvantageous pattern may occur in the stencil mask at adjoining PUF boundaries, therefore the processing is performed so as not to generate such the disadvantageous pattern.
The disadvantageous pattern will be explained.
For example, the PUF and boundary processing unit 1603 divides the pattern 101 as shown in
For example, the complementary mask A is allocated the divided pattern 102 of the PUF I and the divided pattern 105 of PUF II as shown in
To complementary mask B is allocated the divided pattern 103 of PUF I and the patterns 104a and 104b of PUF II as shown in
In order to prevent the above disadvantageous pattern, the PUF and boundary processing unit 1603 extracts the side in a predetermined direction, for example, a direction along the vertical direction with respect to a PUF boundary BL, before complementarily dividing for example the pattern on the PUF boundary for each PUF, generates a vector in accordance with the extracted side, divides the pattern on the PUF boundary BL when the length of a pair of facing vectors having the same length is a predetermined length or more, and performs the complementary division for each PUF based on the divided pattern.
The PUF and boundary processing unit 1603 performs the pattern division processing for a pattern P30 when the pattern P30 exists on the boundary line BL of the PUF1 and PUF2 as shown in for example
The PUF and boundary processing unit 1603 performs the vectorization processing in accordance with the side of the pattern P30 along the direction vertical to the boundary line BL based on the pattern P30 on the PUF1 as shown in for example
At this time, the PUF and boundary processing unit 1603 performs processing such as decomposition of a vector so as to form a pair of vectors having the same length.
As shown in
The PUF and boundary processing unit 1603 divides the pattern P30 to patterns P31 to P37 as schematically shown in for example
The PUF and boundary processing unit 1603 performs the pattern division processing with respect to a pattern on the PUF before the complementary division unit 1604 performs the complementary division processing as explained above, then the complementary division unit 1604 performs the complementary division processing for the pattern division processed pattern for each PUF unit, so it is possible to prevent the generation of a problem pattern.
The smallest patterns to be multiply exposed in the first complementary mask c1 are formed in each of sections I(A), II(B), III(C), and IV(D) as shown in for example
The patterns formed in each of the 5×5 PUFs (blocks) of each section can be formed in each of the corresponding sections I(A) to IV(D) as shown in
The COSMOS layout unit 1606 performs the layout by considering the positions of the beams bm adjacent to the PUFs as shown in
For example, in more detail, as shown in
In the PUF1, the region A1 does not overlap the beams bm at the four sides. The PUF is located at the position of the beams in the regions B and C, so patterns cannot be laid there. In the PUF, the region D overlaps the beams bm at the right side and the bottom side of the drawing. In the PUF2, the region A2 does not overlap the beams bm.
A region 1 corresponds to a region A1 and a region D1. The right side and the bottom side of the region D1 overlap beams bm. A region 2 corresponds to a region A2 and a region B2. The left side of the region B2 overlaps the beam bm. A region 3 corresponds to a region A3, a region B3, and a region D3. The right side of the region A3, the top side of the region B3, and the left side and the bottom side of the region D3 overlap the beams bm. A region 4 corresponds to a region B3 and a region D4. The top side of the region B4 and the bottom side of the region D4 overlap the beams bm. A region 5 corresponds to a region A5, a region B5, and a region D5. The left side of the region A5, the top side and right side of the region B5, and the bottom side of the region D5 overlap the beams bm.
A region 6 corresponds to a region A6 and a region C6. The top side and the left side of the region C6 overlap the beams bm. A region 7 corresponds to a region A7, a region B7, and a region C7. The left side of the region B7 and the top side of the region C7 overlap the beams bm. A region 8 corresponds to a region A8, a region B8, and a region C8. The right side of the region A8 and the top side of the region C8 overlap the beams bm. A region 9 corresponds to a region B9 and a region C9. The beams bm overlap the top side and right side of the region C9. A region 10 corresponds to a region A10 and a region B10. The beams bm overlap the left side of the region A10 and the right side of the region B10.
A region 11 corresponds to a region A11, a region C11, and a region D11. The beams bm overlap the bottom side of the region 11, the left side of the region C11, and the top side and right side of the region D11. A region 12 corresponds to a region A12, a region B12, and a region C12. The beams bm overlap the bottom side of the region A12 and the left side of the region B12. A region 13 corresponds to a region A13, a region B13, a region C13, and a region D13. The beams bm overlap the bottom side and right side of the region A13 and the top side and left side of the region D13. A region 14 corresponds to a region B14, a region C14, and a region D14. The beams bm overlap the right side of the region C14 and the top side of the region D14. A region 15 corresponds to a region A15, a region B15, and a region D15. The beams bm overlap the left side and the bottom side of the region A15, the right side of the region B15, and the top side of the region D15.
A region 16 corresponds to a region C16 and a region D16. The beams bm overlap the left side of the region C16 and the right side of the region D16. A region 17 corresponds to a region B17 and a region C17. The beams bm overlap the left side and bottom side of the region B17. A region 18 corresponds to a region B18, a region C18, and a region D18. The beams bm overlap the bottom side of the region B18 and the left side of the region D18. The region 19 corresponds to a region B19, a region C19, and a region D19. The beams bm overlap the bottom side of the region B19 and the right side of the region C19. A region 20 corresponds to a region B20 and a region D20. The beams bm overlap the right side and bottom side of the region B20.
A region 21 corresponds to a region A21, a region C21, and a region D21. The beams bm overlap the top side of the region A21, the left side and bottom side of the region C21, and the right side of the region D21. A region 22 corresponds to a region A22 and a region B22. The beams bm overlap the top side of the region A22 and the bottom side of the region B22. A region 23 corresponds to a region A23, a region C23, and a region D23. The beams bm overlap the top side and right side of the region A23, the bottom side of the region C23, and the right side of the region D23. A region 24 corresponds to a region C24 and a region D24. The beam bm overlaps the right side of the region C24. A region 25 corresponds to a region A25 and a region D25. The beam bm overlaps the top side of the region A25.
As the complementary patterns complementarily divided by the PUF and boundary processing unit 1603, the COSMOS layout unit 1606 arranges the above-explained patterns P31 to P37 in the regions I to IV based on the predetermined layout data.
At this time, the COSMOS layout unit 1606 selects regions not overlapping the beams bm (at least A, B, C, or D) based on the layout data shown in FIGS. 21 to
For example, when there are patterns crossing the PUF boundaries on the top side and the left side after the complementary division in a PUF of the region 25, if the patterns are arranged in the region A25, they will overlap the beams bm, but if the patterns are arranged in the region D25, they will not overlap the beams bm.
In this way, the COSMOS layout unit 1606 can perform the layout without forcibly dividing patterns by the beams bm when processing PUF1 to PUF25 to arrange the complementarily divided patterns.
In the present embodiment, even when patterns after the complementary division contact each other (except point contact) at the time of PUF division, the patterns are divided at positions where complementary contradictions do not occur.
Further, for example, this boundary processing may be included in the complementary division processing as well. In this case, since the complementary division is carried out in the PUF and processing is carried out at a boundary portion by considering the other fields, the algorithm becomes very complex, so inevitably become a cause of lower reliability.
The PUF and boundary processing unit 1603 according to the present embodiment performs the boundary processing when performing the PUF division, so can easily acquire also graphic information of the neighboring fields. This boundary processing overcomes also the fine graphic disadvantage which may occur on the PUF boundary.
The complementary division unit 1604 performs the complementary division processing based on the patterns as explained above. For details of the complementary division, some known techniques such as Japanese Patent No. 3105580, Japanese Examined Patent Publication (Kokoku) No. 7-66182, Japanese Unexamined Patent Publication (Kokai) No. 11-354422, Japanese Unexamined Patent Publication (Kokai) No. 2000-91191, Japanese Unexamined Patent Publication (Kokai) No. 2001-244192, Japanese Unexamined Patent Publication (Kokai) No. 2001-274072, Japanese Unexamined Patent Publication (Kokai) No. 2002-99075, Yamashita et al. 48th Applied Physics Joint Conference Preprints 30a-ZE-5, Yamashita et al. 61st Applied Physics Joint Conference Preprints 7a-X-8, etc. can be selected.
For example, the complementary division processing now known art is complementary division into two in many cases. For example, two-complementary division can be processed without a problem by the second complementary mask. (COSMOS-II) cc2.
However, for the first complementary mask (COSMOS-I) c1, there is a portion which can be complementarily divided into two or four according to PUF like the layout data of
The complementary division unit 1604 basically performs the processing so as to assign the patterns to 3 complementarily divided patterns or more when assigning the 2 complementarily divided patterns.
Sometimes the stitching precision of the complementarily divided patterns suffers from the disadvantage when performing multiple exposure using the complementarily divided patterns to form the desired patterns. For this reason, the stitching portion 1605 adds predetermined patterns or extends patterns to the divided portions when the complementary division unit 1604 performs the complementary division processing.
In more detail, when multiply exposing a wafer by using for example a complementary mask e1 including complementary patterns e11 and e12 shown in
As a method for preventing this disconnection, as disclosed in for example Japanese Patent No. 270699 and Japanese Patent No. 2730687, the method of adding predetermined patterns or extending patterns to divided parts when complementary dividing patterns is known.
In more detail, the stitching portion 1605 adds predetermined patterns e111 and e121 so as to repair a divided part of the division line BL when the complementary division unit 1604 performs complementary division on the pattern e10 as shown in for example
When using a high energy exposure apparatus in a later step, if simply adding predetermined patterns, the patterns may become enlarged. Therefore, the stitching portion 1605 adds patterns smaller than the predetermined patterns in order to suppress pattern enlargement. At this time, the technology disclosed in for example Japanese Unexamined Patent Publication (Kokai) No. 64-269532 is used. Further, when using a low energy exposure apparatus for exposure in a later step, there is almost no enlargement of the patterns, so the stitching portion 1605 adds fine patterns for correction.
The stitching portion 1605 performs the above pattern addition for the disconnected portions at the time of PUF division and the disconnected portions at the time of complementary division as explained above.
The stitching portion 1605 adds patterns e111, e121, and e221 so as to prevent disconnection when the complementary division results in division to the complementary mask e1 having the complementary patterns e11 and e12 shown in
The COSMOS layout unit 1606 performs the layout of pattern data complementarily divided by the PUF and complementary division unit 1604 and the stitching portion 1605 in each section of the stencil mask based on the map data (layout data) in accordance with the mask shape included in the parameters 152.
The COSMOS layout unit 1606 arranges the complementarily divided patterns in predetermined sections of the stencil mask having the predetermined shapes based on the layout data indicating how the data of PUFs arranged in the memory portion 15 shown in for example
Further, the COSMOS layout unit 1606 of the present embodiment performs the layout based on a map corresponding to the mask shape even in the case of another mask shape, therefore another mask shape can be easily handled without changing the main flow of layout processing in comparison with the case where processing is carried out according to a flow of layout processing dedicated to for example a predetermined mask shape.
The PUFs are arranged in the membranes and combined by the COSMOS layout unit 1606. As a result, there is a possibility that adjacent PUFs may be formed with donut shape or leaf pattern patterns or defect patterns which cannot be formed on the stencil mask due to trouble with the complementary division function.
The pattern shape verification unit 1607 verifies whether or not the complementary patterns for each membrane arranged by the COSMOS layout unit 205 can be formed on the membrane.
The pattern shape verification unit 1607 detects a defect pattern, for example, a donut pattern, as shown in
The pattern shape verification unit 1607 defines a pattern having two or more vertexes traced two or more times when for example drawing a pattern with one stroke as a “defect pattern”.
In more detail, as shown in
As described above, when finishing drawing one pattern, if there are two or more vertexes counted as vertexes traced two or more times when drawing the pattern by one stroke, the pattern shape verification unit 1607 detects this pattern as a defect pattern.
That is, when a pattern of the above donut shape, if drawing this with one stroke, a side drawn by connecting an island portion a at the center of the donut shape and a portion surrounding its periphery (vertex E-vertex I) is generated. The vertexes formed at the two ends of this side will be traced two times each.
The pattern shape verification unit 1607 detects for example leaf patterns as shown in FIGS. 29 to 31 as follows.
The pattern shape verification unit 1607 judges a pattern having a vertex with a value of (inner angle—180°) of a predetermined value or more and a pattern with vertexes having inner angles exceeding 180° continuously provided and with a sum of (inner angle-180°) at these continuous vertexes of a predetermined value or more as defect patterns.
In more detail, for example for a pattern 52 as shown in
By this, for example in the exposure pattern 52 shown in
In the same way, in for example the pattern as shown in
Further, the unit simultaneously extracts defect patterns as follows based on the inner angles of the patterns.
First, when sequentially detecting the inner angles θ along the pattern and a detected inner angle θ exceeds 180°, the unit calculates the value of (inner angle θ-180°) at that vertex. Then, when the inner angle of the continuously arranged next vertex exceeds 180°, it calculates the value of (inner angle θ-180°) at this vertex and adds it to the value of (inner angle θ-180°) at the previous vertex. On the other hand, when the inner angle θ of the next vertex does not exceeds 180°, it cancels this cumulative value and returns it to 0. Then, it extracts patterns with a cumulative value of a predetermined value θss or more as defect patterns. Here, the predetermined value θss is set at for example 90°.
For example, in the pattern 53 shown in
In the same way, in the pattern 54 shown in
Note that even when the predetermined value θss is set at for example θss=100°, (inner angle θ-180°)=45° at the next vertex E is added and 45°+45°=135°≧predetermined value θss (100°) results, therefore the unit detects this pattern as a defect pattern.
Further, by adjusting the settings of θs and θss, the degree of projection of the leaf state region b detected by the pattern shape verification unit 1607 can be adjusted.
Further, the pattern shape verification unit 1607 detects a pattern having for example a shape longer than a predetermined length as a defect pattern. This is because a pattern having a long shape is apt to cause distortion in the center region in the longitudinal direction when forming the pattern in a stencil mask as a real pattern.
The defect patterns detected by the pattern shape verification unit 1607 explained above are subjected to for example complementary division again by the complementary division unit 1604.
For example, as schematically shown in
The in-membrane correction unit 1608 calculates a displacement amount occurring when forming the hole h1 in accordance with the complementary patterns verified by the pattern shape verification unit 1607 in the membrane c3 in accordance with the design data 151 and the parameters 152 and performs correction processing for the complementary stencil mask data so as to obtain the desired pattern as a result of the displacement in accordance with the calculation result.
In more detail, since the membrane c3 is fixed by the beams c4 and there is only a slight influence of the patterns in the membrane c3 upon the beams c4, the in-membrane correction unit 1608 regards the beams c4 as rigid bodies and conducts the analysis in units of the membrane c3. The membrane c3 is formed with the hole h1 in accordance with the complementary pattern s, therefore the in-membrane correction unit 1608 analyzes the displacement for each membrane.
The in-membrane correction unit 1608 performs the displacement analysis in the membrane by for example the finite element method or the differential method. At this time, since there are very many holes (patterns) h1 in the membrane, a long analysis time is taken. The in-membrane correction unit 1608 of the present embodiment analyzes the displacement in the membrane by displacement high speed analysis. The displacement high speed analysis processing calculates for example the displacement amount of only the holes formed in the membrane having a size more than a predetermined size and corrects the positions and shapes of the holes to the desired ones based on the results of the calculation.
The in-membrane correction unit 1608 divides an object for analysis into simple elements as shown in for example
For example, the hole h1 shown in
In the stress analysis according to the finite element method, one element is divided to finer elements in a portion where a large change in stress (easy concentration of stress) is expected or a portion where precise analysis is desirably carried out, for example, in
At this time, the peripheral portion of the hole h2 having a smaller size than the predetermined size is divided to usual elements. This is because the desired pattern is exposed even when holes h2 of less than the predetermined size are not corrected much since it is deemed that the amount of change of shape is within a permissible range. By doing this, the finite element method can be executed at a high speed.
Further, the predetermined size is determined by the relationship between the dimensional precision permitted to the stencil mask used for the semiconductor device and the degree of change of the pattern with respect to the stress found according to the material and thickness of the stencil mask.
The in-membrane correction unit 1608 calculates the above displacement amount and generates a correction amount based on the calculation result. This correction amount is a value indicating to what degree each node is to be corrected independently. When the correction is carried out by using this value as it is, the hole h1 becomes a curve having a contour of for example the curved shape as shown in
For this reason, the in-membrane correction unit 1608 finds the precision permitted in the correction processing from the permitted precision on the mask preparation, finds a correction use permissible pitch using that value as the standard, corrects the hole h1 to the step shapes as shown in for example
By performing this, the excess load due to curves is reduced both for the data processing and for the mask preparation.
Further, the in-membrane correction unit 1608 calculates an opening pattern area density (opening area density) based on the area of the hole patterns in the membrane and sets the thickness of a virtual membrane in accordance with the pattern area density.
For example, in more detail, as shown in
Then, the unit approximates the elastic matrix of each element including a hole (pattern) and having a predetermined thickness by a pseudo elastic matrix of each element not including a hole and having a virtual thickness, analyzes it by the finite element method, and corrects the shape and position of the hole (pattern) in accordance with the results. Here, an elastic matrix is an amount indicating the relationship between the stress and the distortion, while a pseudo elastic matrix is an elastic matrix when giving a virtual thickness in accordance with the pattern area density not including a hole (pattern).
The mask configuration unit 1609 performs one chip's worth of correction in the membrane based on the data corrected by the in-membrane correction unit 1608 and the parameters 152 and lays out the corrected chip in accordance with the mask constitution. For the displacement in the membrane, the same result is obtained at all positions on the mask so far as the patterns in the membrane are the same. At this time, in order to form the COSMOS mask as a whole, alignment patterns and other peripheral patterns are also provided.
The exposure verification unit 1610 performs processing for verification of layout mistakes or if the intended design data is obtained when the constituted COSMOS mask is exposed four times based on the mask constitution generated by the mask configuration unit 1609.
In more detail, the exposure verification unit 1610 performs a graphic processing AND on the obtained four-complementary data as the verification method and verifies if the layout of the original design data 151 and the data of the arrangement of the beam data coincide. By performing this verification, the exposure precision can be guaranteed.
At the time of the preparation of the mask, in more detail, at the time of the drawing the mask, when etching patterns on the membrane, as shown in
For this reason, due to gravity, the center portion of the mask is bent downward so that the surface facing the beam side surface of the membrane c3 sinks down at the time of fabrication of the mask as shown in
In more detail, the distortion due to this mask inversion does not depend upon the patterns in the membrane, therefore the displacement amount is applied to the patterns in each membrane from the distortion profile prepared as a result of analyzing the distortion amount due to the mask structure or the result by experiments. When there is no front/back inversion at the time of fabrication of the mask and the time of usage of the mask, it is not necessary to perform this processing.
The correction result verification unit 1612 verifies if the processing result becomes the correct patterns as the result of the mask inversion correction by the mask inversion correction unit 1611 based on the design data 151 and the parameters 152. The correction amount is analyzed by simulation, therefore it is clear that the results become the same even if the same simulation is used.
The correction result verification unit 1612 according to the present embodiment simulates the distortion correction by using an algorithm different from the algorithm used in the mask inversion correction processing for verification. By this, verification having a high reliability becomes possible.
In more detail, the correction result verification unit 1612 compares the corrected design data with the original design data 151 based on the results of simulation under conditions of mask distortion and the membrane distortion and judges whether or not the difference is within the range of the precision. When it is within the range of precision, the correction result verification unit 1612 outputs the corrected stencil mask data generated by the above series of processing to the data conversion unit 1613.
The data conversion unit 1613 generates the drawing membrane data d16131 for making the mask preparation device 4 shown in for example
In more detail, the data conversion unit 1613 generates the drawing membrane data d16131 for making the mask preparation device 4 draw on (dig in) the membrane from the silicon wafer under the control of for example the mask preparation processing device 3 and generates the drawing pattern data d16132 for drawing the complementarily divided patterns in the membrane c3. The CPU 16 outputs the generated drawing membrane data d16131 and drawing pattern data d16132 via for example the I/F 13 and communication network NET 7 to the mask preparation processing device 3.
At step ST1, for example, the design processing device 2 generates the design data 151 of a desired semiconductor integrated circuit and outputs the same via the communication network NET 7 to the mask processing apparatus 1.
At step ST2, the mask processing apparatus 1 generates the complementary stencil mask data, in more detail, the drawing membrane data d16131 and the drawing pattern data d16132 based on the mask characteristic data indicating the characteristics of the stencil mask including the design data 151 output from the design processing device 2, the device characteristic pattern for the mask preparation device 4, the device characteristic parameters for the exposure apparatus 6, etc. and outputs the same via the network NET 7 to the mask preparation processing device 3.
At step ST3, the mask preparation processing device 3 controls the mask preparation device 4 based on the drawing membrane data d16131 and the drawing pattern data d16132 and makes it actually generate for example the complementary stencil mask c1 as shown in
At step ST4, the exposure processing device 5 controls the exposure apparatus 6, performs alignment based on the mask alignment marks and the wafer alignment marks using the generated complementary stencil mask c1, and exposes the circuit patterns in accordance with the desired design data onto the silicon wafer by multiple exposure by an electron beam. Thereafter, the etching etc. are carried out, circuit patterns are formed in accordance with the desired design patterns on the silicon wafer, the wafer is cut, and the device is packaged etc., whereby the desired semiconductor device is generated.
At step ST21, in the mask processing apparatus 1, for example the alignment mark generation unit 1601 generates the alignment marks etc. based on the design data 151 and the parameters 152.
At step ST22, the mask processing apparatus 1 performs the above-explained internal data processing based on the generated alignment data, design data 151, and parameters 152 and generates the complementary mask pattern data, in more detail the drawing membrane data d16131 and the drawing pattern data d16132.
At step ST201, the membrane shape design unit 1602 generates data for generating the membrane based on the alignment marks d1601 generated by the alignment mark generation unit 1601 at step ST21 as explained above, the design data 151, and the parameters 152 and outputs the same to the data conversion unit 1613.
At step ST202, the PUF and boundary processing unit 1603 performs the PUF division processing and the boundary processing based on the design data 151, parameters 152, and alignment marks d1601. At this time, as explained above, the design data 151 is subjected to the boundary processing of PUF and decomposed to PUFs.
The complementary division unit 1604 performs the complementary division processing based on the design data 151 PUF decomposed by the PUF and boundary processing unit 1603, and the parameters 152 (ST203), the stitching portion 1605 performs the predetermined processing for addition of patterns to the cut portion at the PUF division processing and the cut portion at the complementary division processing (ST204), and the COSMOS layout unit 1606 arranges the complementarily divided pattern data in sections of the stencil mask c1 based on the map data (layout data) in accordance with the mask shape included in the parameters 152 (ST205).
At step ST206, the pattern shape verification unit 1607 verifies whether or not the complementary pattern for each membrane arranged by the COSMOS layout 205 can be formed on the membrane c1. The in-membrane correction unit 1608 calculates the displacement amount occurring when forming holes in accordance with the complementary pattern verified by the pattern shape verification unit 1607 in the membrane c3 in accordance with the design data 151 and the parameters 152 and corrects the complementary stencil mask data so as to obtain the desired patterns as a result of the displacement in accordance with the calculation result (ST207).
At step ST208, the mask configuration unit 1609 performs the correction inside the membrane for one chip based on the data corrected by the in-membrane correction unit 1608 and the parameters 152 and arranges the corrected chip in accordance with the mask constitution. The exposure verification unit 1610 verifies for layout mistakes and whether or not the intended design data is obtained when the constituted COSMOS mask is exposed four times based on the mask constitution generated by the above mask configuration unit 1609 (ST209).
At step ST210, the mask inversion correction unit 1611 performs processing for correction of distortion due to the change of the bending based on the data indicating the mechanical characteristics of the mask included in the data parameters 152 and the complementary pattern data verified by the exposure verification unit 1610. The correction result verification unit 1612 verifies whether or not the processing result gives the correct patterns based on the design data 151 and the parameters 152 as a result of the mask inversion correction processing by the mask inversion correction unit 1611 (ST211).
At step ST212, the data conversion unit 1613 generates for example the drawing membrane data d16131 for making the mask preparation device 4 shown in
As explained above, by executing the mask data processing routine, the desired complementary stencil mask can be generated easily and with a high reliability based on the design data 151 and the mask characteristic data 152 indicating the characteristics of the mask.
Further, the method of use is easy, and human error can be prevented by automatically performing all of the processing.
Further, by performing the PUF division and layout processing by fixed routines, a large scale chip can be processed.
Further, the four-exposure type complementary mask can be easily generated based on the layout data.
Note that the present invention is not limited to the present embodiment. Various preferred modifications are possible.
For example, the processing routines according to the present embodiment are not limited to the above-explained sequence. For example, the predetermined verification processing and correction processing may be executed in the sequence giving the desired results.
According to the present invention, a mask processing apparatus, mask processing method, program and mask enabling easy preparation of the mask used in a charged particle beam exposure apparatus can be provided.
The mask processing apparatus, mask processing method, program and mask of the present invention can be used for processing a mask used in for example a lithography process of a semiconductor production apparatus.
Number | Date | Country | Kind |
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2003-068875 | Feb 2003 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP04/01118 | 2/4/2004 | WO | 7/26/2005 |