Writing apparatus and writing data conversion method

A writing apparatus includes a storage unit configured to store writing data, an acquiring unit configured to acquire information on a pattern defined based on the writing data, a selecting unit configured to select a format of a plurality of formats having different number of bits to be used, based on acquired information on the pattern, for each predetermined region, a converting unit configured to convert data in the predetermined region defined by the writing data, by using a selected format, and a writing unit configured to write a predetermined pattern on a target workpiece, based on converted data in the predetermined region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-319067 filed on Dec. 11, 2007 in Japan, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pattern writing apparatus and a writing data conversion method. For example, it relates to a pattern writing apparatus which writes a predetermined pattern on a target workpiece using an electron beam, and a method for converting writing data to be processed in the writing apparatus.

2. Description of Related Art

The lithography technique that advances microscaling of semiconductor devices is extremely important as being the only process to form patterns in semiconductor manufacturing processes. In recent years, with high integration of large-scale integrated circuits (LSI), critical dimensions required for semiconductor device circuits are shrinking year by year. In order to form a desired circuit pattern on semiconductor devices, a master pattern (called a mask or a reticle) of high precision is required. The electron beam intrinsically having excellent resolution is used for producing such highly precise master patterns.

FIG. 10is a schematic diagram illustrating operations of a variable-shaped electron beam (EB) type pattern writing apparatus. As shown in the figure, the variable-shaped electron beam writing apparatus, including two aperture plates, operates as follows: A first aperture plate410has a rectangular opening or “hole”411for shaping an electron beam330. This shape of the rectangular opening may also be a square, a rhombus, a rhomboid, etc. A second aperture plate420has a variable-shaped opening421for shaping the electron beam330that passed through the opening411into a desired rectangular shape. The electron beam330emitted from a charged particle source430and having passed through the opening411is deflected by a deflector to pass through a part of the variable-shaped opening421and thereby to irradiate a target workpiece or “sample”340mounted on a stage which is continuously moves in one predetermined direction (e.g. X direction) during the writing or “drawing.” In other words, a rectangular shape formed as a result of passing through both the opening411and the variable-shaped opening421is written in the writing region of the target workpiece340on the stage. This method of forming a given shape by letting beams pass through both the opening411and the variable-shaped opening421is referred to as a “variable shaped” method.

When performing the electron beam writing as mentioned above, first, layout of a semiconductor integrated circuit is designed, and layout data (design data), in which pattern layout is defined, is generated. Then, the layout data is converted into writing data which is adapted to the electron beam writing apparatus. The writing data is input into the writing apparatus, and, after plural data processing operations, generated as shot data to be used at the time of writing (refer to e.g., Japanese Patent Application Laid-open (JP-A) No. 2007-128933). Writing processing is performed based on the shot data. In the pattern writing apparatus, first, the writing data is developed into intermediate data before the shot data being generated. Conventionally, the pattern data format has been designed to respond to all possible sizes, coordinates, figure types, and the number of figures. Therefore, in the conventional pattern data format, the number of bits capable of responding to any of these is prepared.

However, depending on the layout of the writing data, there is a case of using only a part of the number of bits prepared in the conventional pattern data format. For example, in the case of the layout where patterns of the same figure or the same size are mainly repeatedly used, only a few numbers of bits prepared in the conventional pattern data format are used. When only several patterns in one layout have such a case of only a few numbers of bits being used, they won't have much influence. However, with the recent trend of pattern miniaturization and pattern number increase, patterns using only a few numbers of bits are increasing. Therefore, if the numbers of bits which are not used are accumulated, it will become a bit number corresponding to a data size not to be disregarded for the throughput of the apparatus.

As mentioned above, in the pattern data format conventionally used, the number of bits capable of responding to all possible sizes, coordinates, figure types, and the number of figures is prepared. Therefore, there are many unused bits, so that if the numbers of the unused bits are accumulated, it will be a bit number corresponding to a data size not to be disregarded for the throughput of the apparatus. As reducing the data size is requested with the recent trend of pattern miniaturization and pattern number increase, it is an issue how to reduce the number of bits which are not used.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a writing apparatus and a writing data conversion method in and by which the number of useless bits is decreased to reduce the data size.

In accordance with one aspect of the present invention, a writing apparatus includes a storage unit configured to store writing data, an acquiring unit configured to acquire information on a pattern defined based on the writing data, a selecting unit configured to select a format of a plurality of formats having different number of bits to be used, based on acquired information on the pattern, for each predetermined region, a converting unit configured to convert data in the predetermined region defined by the writing data, by using a selected format, and a writing unit configured to write a predetermined pattern on a target workpiece, based on converted data in the predetermined region.

In accordance with another aspect of the present invention, a method for converting writing data includes inputting writing data, acquiring information on a pattern defined based on the writing data, selecting a format of a plurality of formats having different number of bits to be used, based on acquired information on the pattern, for each predetermined region, converting data in the predetermined region defined by the writing data, by using a selected format, and storing converted data in the predetermined region.

DETAILED DESCRIPTION OF THE INVENTION

In the following Embodiment, a structure utilizing an electron beam as an example of a charged particle beam will be described. The charged particle beam is not necessarily limited to the electron beam. Another charged particle beam, such as an ion beam, may also be used. Moreover, as an example of a charged particle beam apparatus, there will be described a charged particle beam writing apparatus, especially a variable shaped type electron beam writing apparatus.

FIG. 1is a schematic diagram illustrating the structure of a pattern writing apparatus according to Embodiment 1. InFIG. 1, a pattern writing apparatus100is an example of an electron beam pattern writing apparatus. The pattern writing apparatus100writes a pattern composed of a plurality of figures onto a target workpiece101. The target workpiece101includes a mask to be used in the lithography step of manufacturing semiconductor devices. The pattern writing apparatus100includes a writing unit150and a control unit160. The writing unit150includes a writing chamber103and an electron lens barrel102arranged above the writing chamber103. In the electron lens barrel102, there are arranged an electron gun assembly201, an illumination lens202, a first aperture plate203, a projection lens204, a deflector205, a second aperture plate206, an objective lens207, and a deflector208. In the writing chamber103, there is an XY stage105on which the target workpiece101serving as a writing target is placed. The control unit160includes magnetic disk drives110,116,122, and126, a data processing unit112, memories114,120, and128, a control computer118, a shot data generating unit124, and a writing control unit130. The magnetic disk drives110,116,122and126, the data processing unit112, the memories114,120and128, the control computer118, the shot data generating unit124, and the writing control unit130are mutually connected by buses (not shown). In the control computer118, there are arranged a block division unit40, a cell arranging unit42, a cluster division unit44, a pattern division unit46, a pattern data recording unit48, a format selecting unit50, and a format converting unit52. The magnetic disk drives110,116,122and126and the memories114,120and128are examples of a storage unit or a storage device. Moreover, writing data is stored in an external magnetic disk drive500.

The block division unit40, the cell arranging unit42, the cluster division unit44, the pattern division unit46, the pattern data recording unit48, the format selecting unit50, and the format converting unit52may be configured as processing functions executable by a computer, such as a CPU, that executes a program, or configured by hardware of an electric circuit. Alternatively, they may be executed by a combination of hardware of an electric circuit and software, or a combination of the hardware and firmware. When executed by software or combination with the software, each data to be input into the computer which performs processing, or each data being or having been processed is stored in the memory120each time. Similarly, the data processing unit112and the shot data generating unit124may be configured as processing functions executable by a computer, such as a CPU, that executes a program, or configured by hardware of an electric circuit. Alternatively, they may be executed by a combination of hardware of an electric circuit and software, or a combination of the hardware and firmware. When executed by software or combination with software, each data to be input into the computer which performs processing, or each data being or having been processed is stored in the memory114for the data processing unit112, and in the memory128for the shot data generating unit124each time.

Moreover, the data processing unit112, the control computer118, and the shot data generating unit124can be configured by one computer or plural computers, respectively. A parallel processing can be performed by being configured by plural computers, and thereby increasing the processing speed.

FIG. 1shows structure elements necessary for explaining Embodiment 1, it should be understood that other structure elements generally necessary for the pattern writing apparatus100may also be included.

FIG. 2shows an example of a hierarchical structure of writing data according to Embodiment 1. In the writing data, a writing region or “writing area” has a hierarchical structure composed of a series of plural internal configuration units, such as a layer of a chip10, a layer of a stripe20formed by virtually dividing the chip region into a plurality of strip-like portions in a certain direction, for example, the Y-axis direction, a layer of a block30formed by dividing the stripe20, a layer of a cell32composed of at least one or more figures, a layer of a cluster34formed by dividing the cell32, and a layer of a figure (pattern)36which is arranged in the cluster34and constitutes the cell32. Generally, a plurality of chips are laid out in the writing region of one target workpiece101. Therefore, in the data processing unit112mentioned later, chip merging is performed to configure a hierarchy as shown inFIG. 2. While the stripe20is herein formed by dividing the chip region into a plurality of strip-like portions arrayed in the Y-axis direction (predetermined direction) as an example, it may be divided into portions parallel to the drawing surface and arrayed in the direction of X-axis orthogonal to the Y-axis. Alternatively, it may be other direction parallel to the drawing surface.

FIG. 3is a flowchart showing a writing method according to Embodiment 1. As mentioned above, when writing with an electron beam, it starts with designing a layout of a semiconductor integrated circuit. Then, layout data (design data) in which pattern layout is defined is generated. The layout data is converted into writing data adapted to be input into the writing apparatus100. The writing data is read from the magnetic disk drive500, input into the writing apparatus100, and stored in the magnetic disk drive110. After a plurality of data processing as mentioned later, the writing data is generated as shot data used at the time of writing.

In the step S102, as a data processing step, the data processing unit112reads and inputs each wring data of a plurality of chips from the magnetic disk drive110. The data processing unit112rearranges the each writing data in the writing region of the pattern writing apparatus100, and performs chip merging. Moreover, in addition to this, the data processing unit112may perform data processing, such as mirroring and scaling. After being processed as mentioned above, the writing data is stored in the magnetic disk drive116.

In the step S104, as a step of dividing into blocks, the block division unit40develops the writing data, which has been data processed in the prior step, to virtually divide the chip10or each stripe20into a plurality of blocks30as shown inFIG. 2.

In the step S106, as a cell arrangement step, the cell arranging unit42further develops the writing data in order to arrange the laid out cell32in each block30.

In the step S108, as a step of dividing into clusters, the cluster division unit44further develops the writing data in order to virtually divide each cell32into a plurality of clusters34as shown inFIG. 2.

In the step S110, as a step of dividing into patterns, the pattern division unit46further develops the writing data in order to divide each cluster34into a plurality of figures36(patterns) laid out in each cluster34as shown inFIG. 2. The pattern division unit46can acquire pattern data (pattern information) such as the number, types, sizes (L, M) and arrangement coordinates (X, Y) of the figures36in each cluster34by performing pattern division. Thus, the pattern division unit46can acquire information on the pattern defined based on the writing data. The pattern division unit46serves as an example of an acquiring unit.

In the step S112, as a pattern data recording step, the pattern data recording unit48records (stores) the acquired pattern data such as the number, types, sizes (L, M) and arrangement coordinates (X, Y) of thefigure 36with respect to each cluster34, into the memory120. In addition, information on a plurality of formats, such as a conventional format, a format (1), a format (2), a format (3), and so on, which are used in a format conversion mentioned later, is stored in the memory120. Each of these formats is configured to have a different bit number to be used each other.

In the step S114, as a format selection step, the format selecting unit50selects one of a plurality of formats based on the acquired pattern data for each cluster34(predetermined region). The format selecting unit50selects a format based on pattern information of at least one of the number, type, and size of thefigure 36. For example, the format (1) is selected for the cluster34whose pattern number is larger than a predetermined threshold value. The format (2) is selected for the cluster34in which only rectangular patterns composed of only right angles, such as a square or a rectangle, are arranged. For example, the format (3) is selected for the cluster34in which a large number of small patterns, such as a contact hole pattern, are arranged. Then, the conventional format is selected for the cluster34in which patterns other than the above ones are arranged. Thus, the format selecting unit50selects one of a plurality of formats for each cluster34based on a predetermined reference.

In the step S116, as a format conversion step, the format converting unit52converts data in the cluster34defined by the writing data, based on the selected format. By converting the format of the writing data, intermediate data being a preliminary step to shot data can be generated.

FIG. 4shows an example of a cluster according to Embodiment 1, in which a large number of patterns are arranged.FIG. 4shows the case where a large number of small-sized figures62are arranged. Since the figure size is small in such a layout, the number of bits indicating the size of the figure can also be reduced. For example, 17 bits for the size L and 17 bits for the size M, totally 34 bits, are needed in the conventional format, whereas 10 bits for the size L and 10 bits for the size M, totally 20 bits, are needed in the layout shown inFIG. 4. Since 14 bits can be reduced for the figure size (L, M) with respect to onefigure 62, when the reduced amounts are accumulated for all the figures62, it becomes possible to reduce an immense number of bits in the whole writing data. With regard to the figure coordinates (X, Y) for arranging thefigure 62, the coordinates from the origin (reference position) of the cluster34are conventionally used. However, since the distance between figures is short in the layout shown inFIG. 4, it is also preferable to use coordinates from the origin of the adjacentfigure 62, instead of using the cluster origin as the reference position. This makes it possible to reduce the bit number to 11 bits for X and 11 bits for Y, totally 22 bits for example, in the layout shown inFIG. 4when defining the coordinates (X, Y), while 17 bits for X and 17 bits for Y, totally 34 bits for example, are needed in the conventional format. Since 12 bits can be reduced for the coordinates (X, Y) with respect to onefigure 62, it becomes possible to reduce a large number of bits even by merely accumulating such reduced amounts of all the figures62in the cluster. Furthermore, if there are many layouts similar to this, an immense number of bits can be reduced in the whole writing data.

FIG. 5shows an example of intermediate data converted according to the format (1) in Embodiment 1. In intermediate data12ofFIG. 5, which has been converted based on the format (1), a stripe header and a stripe number, and further a block header and a block number relating to block data located in the stripe concerned are defined in order. Following the block number, a cell header and a cell number relating to cell data arranged in the block concerned, and a cluster header and a cluster number relating to cluster data arranged in the cell concerned are defined. Then, following the cluster number, an identifier (format ID) for identifying the format (1) used for the conversion is defined. By assigning 4 bits, for example, to a format ID, it becomes possible to define the format ID to be identifiable. Following the format ID, a figure code, a figure size (L, M), and figure coordinates (X, Y) are defined. Then, following the first figure coordinates (X, Y), a figure code, a figure size (L, M), and figure coordinates (X, Y) of the secondfigure 62arranged in the same cluster34are defined. In this way, when the entire figures in one cluster34have been defined, a cluster header and a cluster number of the next cluster34are followingly defined. After this, defining is performed similarly.

The format (1) is designed to secure, for example, 10 bits for L and 10 bits for M, totally 20 bits, for defining the figure size (L, M). In addition, it is designed to secure, for example, 11 bits for X and 11 bits for Y, totally 22 bits, for defining the coordinates (X, Y). Compared with the conventional format in which 17 bits for L and 17 bits for M, totally 34 bits for example, are needed for defining the figure size (L, M), and 17 bits for X and 17 bits for Y, totally 34 bits for example, are needed for defining the coordinates (X, Y), it becomes possible to reduce 26 bits for one figure by using the format (1).

It is preferable herein that a condition is set for the format selecting unit50as a reference for selecting the format (1), such as the condition that the number of figures (the number of patterns) arranged in the cluster34is more than a predetermined threshold value, for example, 3000. Owing to the intermediate data being generated in the format (1), the number of bits for the figure size (L, M) and the coordinates (X, Y) can be reduced.

FIG. 6shows an example of a cluster according to Embodiment 1, in which only rectangular patterns are arranged.FIG. 6shows the case where only rectangular figures64composed of only right angles, such as a square or a rectangle, are arranged. Since defining a figure code indicating a figure type is not needed in such a layout, it is possible to do without the number of bits of figure codes. For example, while 7 bits are needed for defining a figure code in the conventional format, the bit number can be reduced to zero in the layout shown inFIG. 6. Since 7 bits can be reduced for a figure code with respect to onefigure 64, when the reduced amounts are accumulated for all the figures64, it becomes possible to reduce an immense number of bits in the whole writing data.

FIG. 7shows an example of intermediate data converted according to the format (2) in Embodiment 1. Intermediate data14ofFIG. 7, which has been converted based on the format (2), is defined similarly to the intermediate data12from the stripe header to the format ID. Then, following the format ID, a figure size (L, M), and figure coordinates (X, Y) are defined. Following the first figure coordinates (X, Y), a figure size (L, M), and figure coordinates (X, Y) of the secondfigure 62arranged in the same cluster34are defined. In this way, when the entire figures in one cluster34have been defined, a cluster header and a cluster number of the next cluster34are followingly defined. After this, defining is performed similarly.

The format (2) is designed to do without bits for defining figure codes. Compared with the conventional format in which, for example, 7 bits are needed for defining a figure code, it is possible to reduce 7 bits for each figure by using the format (2).

It is preferable herein that a condition is set for the format selecting unit50as a reference for selecting the format (2), such as the condition that the figure type arranged in the cluster34is a rectangle only. Owing to the intermediate data being generated in the format (2), the number of bits for the figure code can be reduced.

FIG. 8shows an example of a cluster according to Embodiment 1, in which contact patterns are arranged.FIG. 8shows the case where there are arranged a large number of figures66being small-sized contact hole patterns. The same figures are often repeated in such a layout compared with afigure 68being a wiring pattern, etc. Therefore, the figure size can be limited to some types, thereby defining the figure size by using figure size codes instead of using the sizes of L and M. For example, figure size codes are a bit value “0” for L1and M1, a bit value “1” for L2and M2, and a bit value “2” for L3and M3. Thus, the number of bits indicating the figure size can also be reduced. For example, 17 bits for L and 17 bits for M, totally 34 bits, are needed for defining figure sizes L and M in the conventional format, whereas it can be reduced to 3 bits, for example, in the layout shown inFIG. 8as mentioned above. Since 31 bits can be reduced for the figure size (L, M) of one figure of thefigure 66or thefigure 68, when the reduced amounts are accumulated for all the figures, it becomes possible to reduce an immense number of bits in the whole writing data.

Similarly, the figure type can also be limited to some types in the layout shown inFIG. 8. Therefore, the number of bits for the figure code can be reduced. While 7 bits, for example, are needed for defining a figure code in the conventional format, it is possible to reduce the bit number to 3 bits when defining the figure type to be three types corresponding to the three figure sizes mentioned above in the layout shown inFIG. 8. Since 4 bits can be reduced for the figure code of one figure of thefigure 66or thefigure 68, when the reduced amounts are accumulated for all the figures, it becomes possible to reduce an immense number of bits in the whole writing data.

FIG. 9shows an example of intermediate data converted according to the format (3) in Embodiment 1. Intermediate data16ofFIG. 9, which has been converted based on the format (3), is defined similarly to the intermediate data12from the stripe header to the format ID. Then, following the format ID, a figure code, a figure size code, and figure coordinates (X, Y) are defined. Following the first figure coordinates (X, Y), a figure code, a figure size code, and figure coordinates (X, Y) of the secondfigure 62arranged in the same cluster34are defined. In this way, when the entire figures in one cluster34have been defined, a cluster header and a cluster number of the next cluster34are followingly defined. After this, defining is performed similarly.

The format (3) is defined to secure 3 bits for defining a figure size code, for example. In addition, it is designed to secure 3 bits for defining a figure code, for example. Compared with the conventional format in which 17 bits for L and 17 bits for M, totally 34 bits for example, are needed for defining the figure size (L, M), and 7 bits, for example, are needed for defining a figure code, it becomes possible to reduce 35 bits for one figure by using the format (3). It is further preferable to store a corresponding table which indicates the bit value “0” corresponds to (L1, M1), the bit value “1” does to (L2, M2), and the bit value “2” does to (L3, M3) in the memory120, etc.

It is preferable herein that a condition is set for the format selecting unit50as a reference for selecting the format (3), such as the condition that the size of the figure arranged in the cluster34is 1/A, for example 1/100, of the cluster size, and the number of the figures arranged in the cluster34is B, for example 100 or more. Owing to the intermediate data being generated in the format (3), the number of bits for the figure size (L, M) and the figure code can be reduced.

As mentioned above, the format selecting unit50selects a format based on pattern information of at least one of the number, type, and size of the figure. However, when selecting one of formats, it is not limited to the references mentioned above. It is preferable that the format selecting unit50selects a format so that the number of bits to be used by the data after conversion in the cluster may be fewer.

As mentioned above, the intermediate data in each cluster, whose number of bits has been greatly reduced as a result of the conversion, is memorized (stored) in the magnetic disk drive122.

In the step S118, as a shot data generating step, the shot data generating unit124reads the intermediate data from the magnetic disk drive122to generate shot data. Concretely, the shot data generating unit124refers to a format ID defined in the read intermediate data, develops the intermediate data based on the format, and divides each figure into shot figures. The shot data generated as mentioned above is stored in the magnetic disk drive126.

Then, the writing unit150writes a predetermined pattern on the target workpiece101as follows by using an electron beam200controlled by the shot data based on data in the cluster converted on the basis of a plurality of formats described above. The writing unit150is controlled by the writing control unit130.

The electron beam200emitted from the electron gun assembly201irradiates the entire first aperture plate203having an opening or “hole” in the shape of a rectangle by using the illumination lens202. At this point, the electron beam200is shaped to be a rectangle. Such a rectangular shape may be a square, rhombus, rhomboid, etc. Then, after having passed through the first shaping aperture plate203, the electron beam200of a first aperture image is projected onto the second aperture plate206by the projection lens204. The position of the first aperture image on the second aperture plate206is controlled by the deflector205, and the shape and size of the beam can be changed. After having passed through the second aperture plate206, the electron beam200of a second aperture image is focused by the objective lens207and deflected by the deflector208to reach a desired position on the target workpiece101placed on the XY stage105which is movably arranged.

Here, the effect of reducing the number of bits is verified using one of the formats mentioned above. According to the ITRS (International Technology Roadmap for Semiconductor) report, the current layout design uses a half pitch (HP) of 65 nm. Based on this, the verification will be performed using a cluster in which figures of 80 nm being the minimum pattern size are simply arrayed at a pitch of 160 nm. The cluster size is supposed to be 12.8 μm, and the format (1) mentioned above is used in this case. While 17 bits for L and 17 bits for M, totally 34 bits, are needed for defining the figure size (L, M) in the conventional format, it is possible to reduce the bit number to 10 bits for L and 10 bits for M, totally 20 bits by using the format (1). In addition, while 17 bits for X and 17 bits for Y, totally 34 bits, are needed for defining coordinates (X, Y) in the conventional format, it is possible to reduce the bit number to 11 bits for X and 11 bits for Y, totally 22 bits, by using the format (1). Thus, while 68 bits are needed in the conventional format, it is possible to reduce the bit number to 42 bits in the format (1). Therefore, the amount of date in this cluster can be reduced by 1− 42/68=0.38, namely 38%.

As mentioned above, by preparing several formats having different number of bits to be used, it becomes feasible to select the format in which the number of bits required in accordance with the layout of writing data is secured. Therefore, the number of bits not being used can be reduced in the data in a predetermined region having been converted. Owing to selecting a format for each predetermined region, the effects of reducing the number of bits are accumulated, thereby greatly reducing the number of bits not being used with respect to the entire regions.

According to the present Embodiment as mentioned above, since the format to be used for converting into intermediate data can be selected from a plurality of formats, it is feasible to greatly reduce the number of bits of the intermediate data. As a result, the data size of the intermediate data can be reduced and the writing time can be greatly shortened. Thus, the throughput of the apparatus can be increased extremely.

While the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific ones. For example, although the format is selected for each cluster, it is not limited thereto. For example, the format may be selected for each cell.

While description of the apparatus structure, control method, etc. not directly required for explaining the present invention is omitted, some or all of them may be suitably selected and used when needed. For example, although the structure of the control unit for controlling the writing apparatus100is not described, it should be understood that a necessary control unit structure is to be selected and used appropriately.

In addition, any other apparatus and method for generating writing data, apparatus and method for converting writing data, and apparatus and method for writing with a charged particle beam that include elements of the present invention and that can be appropriately modified by those skilled in the art are included within the scope of the present invention.