Manufacturing method of a semiconductor device and method for creating a layout thereof

A method for manufacturing a semiconductor device of one embodiment of the present invention includes: forming an insulation layer to be processed over a substrate; forming a first sacrificial layer in a first area over the substrate, the first sacrificial layer being patterned to form in the first area a functioning wiring connected to an element; forming a second sacrificial layer in a second area over the substrate, the second sacrificial layer being patterned to form in the second area a dummy wiring; forming a third sacrificial layer at a side wall of the first sacrificial layer and forming a fourth sacrificial layer at a side wall of the second sacrificial layer, the third sacrificial layer and the fourth sacrificial layer being separated; forming a concavity by etching the insulation layer to be processed using the third sacrificial layer and the fourth sacrificial layer as a mask; and filling a conductive material in the concavity.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-320444, filed on Dec. 12, 2007; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is related to a method which employs side wall processing during the manufacture of a semiconductor device.

2. Description of the Related Art

Semiconductor devices are now widely used in a number of different fields. The demands for small scale semiconductor devices, reductions in the amount of energy consumption, improvements in reliability, and reductions in costs are increasing year by year. Particularly, in order to achieve small scale semiconductor devices an increased level of manufacturing technology is being demanded as the number of elements included in a semiconductor device per unit area is increasing.

A reduction in wiring width or a reduction in spaces between wirings is given as one method for achieving small scale semiconductor devices. However, in contemporary lithography technologies in which a pattern such as a wiring is formed using optical lithography, there are limits to the level of resolution due to the wavelength used. Thus, as a method which overcomes the limits of this resolution for forming a pattern, the side wall processing (also called side wall transfer processing) is proposed, for example, in Japan Patent Laid Open Heisei 8-55908.

The side wall processing comprises the following steps: 1) A sacrificial layer is formed on a layer to be processed; 2) The sacrificial layer is patterned by lithography, for example. The sacrificial layer may be processed by slimming; 3) at or beside the side wall of the sacrificial layer another sacrificial layer is formed as a mask; 4) using this sacrificial layer as a mask the layer to be processed is etched. By the side wall processing, it is possible to form a detailed pattern which exceeds the resolution limits of lithography when the side wall processing is used.

However, in the side wall processing there are constraints to the shape of a pattern which is formed by a sacrificial layer used as a mask. As a result, the pattern which can be obtained by etching a layer to be processed includes unnecessary wiring patterns and short circuits are sometimes generated via these unnecessary wirings. In addition, when a pattern density formed by a sacrificial layer which becomes a mask changes significantly depending on the positions, the microloading effect sometimes occurs. This is because the speed of etching the layer to be processed changes depending on the positions. Also, the dishing effect sometimes occurs during a CMP (Chemical Mechanical Polishing) process in a damascene process which is performed after the layer to be processed is etched. As a result, it becomes difficult to improve the yield.

BRIEF SUMMARY OF THE INVENTION

A method for manufacturing a semiconductor device according to one embodiment of the present invention comprises: forming an insulation layer to be processed over a substrate; forming a first sacrificial layer in a first area over the substrate, the first sacrificial layer being patterned to form in the first area a functioning wiring connected to an element; forming a second sacrificial layer in a second area over the substrate, the second sacrificial layer being patterned to form in the second area a dummy wiring; forming a third sacrificial layer at a side wall of the first sacrificial layer and forming a fourth sacrificial layer at a side wall of the second sacrificial layer, the third sacrificial layer and the fourth sacrificial layer being separated; forming a concavity by etching the insulation layer to be processed using the third sacrificial layer and the fourth sacrificial layer as a mask; and filling a conductive material in the concavity.

A method for manufacturing a semiconductor device according to one embodiment of the present invention comprises: forming a conducting layer to be processed over a substrate; forming a first sacrificial layer in a first area over the substrate, the first sacrificial layer being patterned to form in the first area a functioning wiring connected to an element arranged over the substrate; forming a second sacrificial layer in a second area over the substrate, the second sacrificial layer being patterned to form in the second area a dummy wiring; forming a third sacrificial layer at a side wall of the first sacrificial layer and forming a fourth sacrificial layer at a side wall of the second sacrificial layer, the fourth sacrificial layer being comprised of a plurality of connected components; forming a concavity by etching the conducting layer to be processed using the third sacrificial layer and the fourth sacrificial layer as a mask; and filling an insulating material in the concavity.

A method for creating a layout of a semiconductor device according to one embodiment of the present invention comprises: deciding wiring pathways connecting a plurality of elements arranged within an integrated circuit of the semiconductor device; synthesizing layout data for creating a mask pattern for processing a insulating layer over a substrate to realize the wirings based on the wiring pathways; calculating a change of density of the mask pattern based on the layout data; arranging a patter of a dummy wiring in the mask pattern to lessen the change of density.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, the preferred embodiments of the present invention are described. Furthermore, the present invention should not be interpreted as limited to the embodiments described below. It is possible to work the present invention by various embodiments.

First Embodiment

FIG. 1exemplarily shows a plane view of a part of a substrate of a semiconductor device related to one embodiment of the present invention. As is shown inFIG. 1(A), the semiconductor device related to one embodiment of the present invention includes, on the substrate, a functioning area101and a region called a dummy area102. A functioning area is a region on a substrate in which a plurality of elements required for exercising the functions of a semiconductor device (such elements are hereinafter referred to as functioning elements) and wirings which connect the functioning elements (such wirings are hereinafter referred to as functioning wirings) are arranged. A functioning wiring and a functioning area can be inductively defined as follows. First, an input/output terminal which inputs and/or outputs signals from and/or to exterior devices is a functioning element. And a wiring which is connected to a functioning element is a functioning wiring. An element which is connected to a functioning wiring is a functioning element. Furthermore, when a functioning element is a switching element such as a transistor and this element is always in an OFF state, a wiring which is connected via this functioning element may be further defined to be not a functioning wiring.

Further, a functioning area and a dummy area are not limited to be located on the surface of the substrate but also located in the interior of the substrate, above the surface of a layer which is arranged in a position of a certain distance from the surface of the substrate. That is, a functioning area and a dummy area are formed in a single layer or a plurality of layers above, on, or beneath the substrate.

A dummy area is defined to be a region excluding functioning areas. That is, the region in which wirings which do not contribute to the operations of circuits formed using the above stated functioning elements and functioning wirings, are arranged. In other words, a dummy area is a region in which wirings not connected to functioning elements and functioning wirings which is unrelated to the operations of the semiconductor device, are arranged (such wirings are hereinafter referred to as dummy wirings) or a region in which insulation material is arranged between the functioning wirings and the dummy area.

FIG. 1(B) and (C) exemplify a functioning area and a dummy area from another viewpoint. As is shown inFIG. 1(B), the functioning area103which is surrounded by the dummy area104does not have to be a convex shaped region but may also include a concave section. Also, there may also be a dummy area105within the functioning area103. In addition, as is shown inFIG. 1(C), there may be a plurality of functioning areas106and107which is surrounded by a dummy area108.

FIG. 2is a diagram which explains the functioning wirings and functioning area from a number of viewpoints. InFIG. 2(A), assuming that the wiring of the reference number201connects together elements which are necessary for the functions of the semiconductor device, the functioning wiring203which is connected to the functioning wiring201via a contact202is then shown as a functioning wiring. In addition,FIG. 2(B) is a diagram which explains a functioning wiring from the viewpoint of a variation in a voltage which is applied. That is, following the point where operations of the semiconductor device begin, for example, after a certain period of time has elapsed since a power supply, a wiring in which a variation in a voltage which is applied exceeds a certain value, is a functioning wiring. The variation in voltage is defined as the difference between the maximum voltage H and the minimum voltage L after the point in time when operations begin. For example, the variation in voltage is required as the arithmetic difference between H and L or as a ratio of the size of H to the size of L (furthermore, when a ratio is calculated, a standard/base voltage is appropriately changed in the case where L becomes 0). In addition, inFIG. 2(C), when the symbols204and205are referring to functioning wirings, an insulation region206(space between the functioning wirings204and205) which is located between these functioning wirings forms a functioning area. Of course, the functioning wirings204and205which form a functioning area is also shown.

In the description above, a functioning area is defined first and then a region which is not a functioning area is defined as a dummy area. However, the definitions of the functioning area and dummy are not limited to the definitions stated above. Reversely, a dummy area can also be defined first. That is, a wiring which is not connected to a contact hole or even if a wiring is connected to a contact hole, a dummy wiring is defined as a wiring with a fixed voltage which is applied at operation time of a semiconductor device or a wiring with a voltage variation within a predetermined level. Then, a dummy area can be defined as a region which includes a dummy wiring and insulation material which is in contact with a dummy wiring, and a functioning area can be defined as a region excluding a dummy area.

In semiconductor devices, particularly in semiconductor memory devices which include memory circuits, the same pattern of a detailed structure for achieving small size repeatedly appears in a functioning area. However, because a dummy area is not related to a functioning of the semiconductor device, in a dummy area either there are no wirings at all or there are few wirings compared to a functioning area. Therefore, when the number of wirings which are crossed by a line segment of a certain length (such number is generally defined as an inverse of a pitch) or the ratio of area occupied by elements and wirings in a certain area (such ration is generally defined as a patter density) is calculated, generally the inverse of a pitch or the pattern density in a dummy area becomes smaller than the inverse of a pitch or the pattern density in a functioning area.

Therefore, a graph of a change in a pattern density to a position on a substrate is drawn as inFIG. 3, for example. That is, the pattern density is different between the dummy area and the functioning area. The pattern density of the functioning area is larger than the pattern density in the dummy area. Also, as in a memory cell array of a nonvolatile semiconductor memory device, when the same pattern is regularly and repeatedly arranged, a periodically changing graph of a change in a pattern density in the interior of a functioning area is obtained. In addition, when a functioning area and a dummy area are regularly and repeatedly arranged, a periodically changing graph of the position in which this type of functioning area and dummy area are arranged is obtained.

In addition, a spatial frequency of a pattern can be calculated for each position on a substrate. For example, (1) an image of a pattern, which is formed by wirings and insulation spaces formed in/on a substrate, is decomposed into square pixels having a side length of a half of a minimum process dimension according to Shannon's Theorem for example, (2) the adjacent pixels are grouped into square blocks of pixels, (3) the discrete Fourier transformation or discrete cosine transformation is applied to each groups.

As to the spatial frequency as calculated above, when the same pattern of a functioning area and a dummy area is regularly and repeatedly arranged, the spatial frequency regularly changes. In addition, when the same pattern is repeated in the interior of a functioning area the spatial frequency periodically changes spatially.

The value of the inverse of a pitch is sometimes different depending on the direction of a line segment of certain length for calculating a number of wirings crossing a line of a length of a predetermined length, and there is a problem in calculating mechanically and accurately the pitch. While by calculating a patter density, a problem such as in calculating a pitch does not occur because a pattern density is calculated as a value of one dimension for a region of a certain area, there is a problem in which it is difficult to know the direction of wirings for example. This problem is overcome by calculating a spatial frequency because a spatial frequency can be calculated mechanically as a two dimensional value to a block which expands in two dimensions.

When a pattern density or a spatial frequency in a functioning area and dummy area are significantly changes, the possibility of dishing effects during a planarization process such as CMP or the possibility of microloading effects due to a difference in etching speed within a substrate becomes greater.

FIG. 18explains the occurrence of microloading effects. InFIG. 18, a mask is arranged in the white sections and the state after an anisotropic etching in a perpendicular direction of the diagram to the black parts. Even if an anisotropic etching is performed in a perpendicular direction, it is inevitable that an etching in horizontal direction is slightly performed. As a result, even if a mask of the same width is arranged on the white sections, when a pattern density of a mask pattern or a spatial frequency is different depending on positions on the substrate, the speed of etching in a horizontal direction is different.FIG. 18shows a result where the speed of etching in a horizontal direction is different. Specifically, when a pattern density or a spatial frequency is in a high position, the speed of etching in a horizontal direction becomes greater compared to a low position. As a result, the higher the position of a pattern density or a spatial frequency is, the larger the amount of erosion of the part beneath a mask and the width of the white part becomes smaller. InFIG. 18, because the pattern density or the spatial frequency in an end part from the central part is high, the width of the white part of the end part becomes smaller.

Of course, depending on the etching conditions, mask material, or material to be etched, it is sometimes the case that the lower the pattern density or spatial frequency is, the larger the speed of etching.

When microloading effects or dishing effects occur, the manufacturing yield of semiconductor devices decreases. Thus a semiconductor device related to one embodiment of the present invention is manufactured so that changes in a pattern density and/or a spatial frequency under side wall processing, which accompany the restrictions in pattern formation, become smaller or equal. While in addition, the occurrence of short circuits becomes greater under side wall processing because unnecessary wirings are generated, in the manufacturing method of a semiconductor device related to one embodiment of the present invention, this problem is solved.

Below, an outline of a side wall processing is explained while referring toFIG. 4toFIG. 6. Next, the phenomenon whereby short circuits occur easily when the changes in pattern density or spatial frequency in a side wall processing are made smaller is explained while referring toFIG. 7andFIG. 8.

FIG. 4(A) shows a cross section of a substrate and a structure which is formed on the substrate. A layer402to be processed is deposited on a substrate401, a first sacrificial layer403is further deposited on the layer402to be processed and the first sacrificial layer403is formed into a certain pattern by lithography.FIG. 4(B) shows a planar view of the substrate401.

Furthermore, there are cases where the layer to be processed is a conductive layer having conductive properties and where an insulation layer having insulation properties. Polysilicon, for example, may be used as a material for a conductive layer and silicon oxide may be used as a material for an insulation layer.

FIG. 4(C) and (D) show a structure after a slimming process has been performed on the first sacrificial layer403to make a finer pattern of the first sacrificial layer403. Furthermore, slimming is not an essential process and can be performed according to necessity.

Next, the material of the second sacrificial layer404has been deposited on the layer402to be processed on which the pattern by the first sacrificial layer403is formed.FIG. 4(E) and (F) show a structure after anisotropic etching has been performed so that a second sacrificial layer404is left at or beside the side wall of the first sacrificial layer403. Because the second sacrificial layer404is formed at or beside the side wall of the first sacrificial layer403, the shape of the second sacrificial layer404becomes a loop shape as is shown inFIG. 4(F). The second sacrificial layer surrounds the pattern formed by the first sacrificial layer403.

FIG. 5(A) and (B) show a structure after the first sacrificial layer403has been selectively removed. Then,FIG. 5(C) and (D) show a structure when the layer402to be processed is etched using the second sacrificial layer404as a mask. A concavity is formed in the layer402except under the second sacrificial layer404. After this the second sacrificial layer404is selectively removed and the structure shown inFIG. 5(E) and (F) are obtained.

As stated above, because the second sacrificial layer404has a loop shape the concavity pattern formed by the etching layer404using the second sacrificial layer404as a mask also has a loop structure. Therefore, a part of the loop structure generally is removed in order to form one or more wirings. In addition, there are cases when there is a need for a process to restrict the range in which a different material is filled between the second sacrificial layer404, which is left by etching. Then, as is shown inFIG. 6(A) and (B), for example, in order to restrict the range in which a different material is filled after obtaining the structure in which a part of the layer402to be processed is removed, another material405is filled as in shown inFIG. 6(C) and (D), for example. Furthermore, another material405can be the same material as the layer402to be processed. That is, another material405may be a different material to the material which is filled in the concavity formed between the layer402to be processed.

Then, another material406is filled between the layers402to be processed as shown inFIG. 6(E) and (F). That is, a structure in which the material406is sectioned by the layer402to be processed can be obtained. A width which is sectioned by the material404, that is, the width of a line of a pattern formed on the layer402to be processed can be made smaller than the resolution limits of lithography by side wall processing. In addition, when slimming is performed on the first sacrificial layer403, the width of the material406, that is, the distance between the layers402to be processed402, can be made smaller than the resolution limits of lithography.

Furthermore, the process for removing a part of a loop, the process for further depositing another material405and the process for depositing yet another material406can be appropriately interchanged. For example, the material406may be deposited in the structure inFIG. 5(E) and (F) and then a region in which another material406is deposited inFIG. 6(C) and (D) is etched and a part of the loop is removed.

FIG. 7(A) shows a functioning area1and a functioning area2on the substrate with a dummy area1which exists between these functioning areas. Furthermore, the functioning area1and the functioning area2may be a part of the same functioning area.

InFIG. 7(A), because there are no wirings in the dummy area1the pattern density and/or the spatial frequency in the functioning area1and functioning area2and the pattern density and/or the spatial frequency in the dummy area1are significantly different. As a result, microloading effects and/or dishing effects occur as stated above.

Thus, the conducting material which becomes a wiring701is deposited on the substrate in the shape of a layer, the second sacrificial layer702is added to the functioning area1and functioning area2and also formed on the dummy area1and etched as is shown inFIG. 7(B) making the differences of spatial frequency etc. smaller.

Because of the constraints due to side wall processing, as is shown inFIG. 7(B) the number of dummy wirings that are formed on the dummy area1becomes an even number. In addition, when the second sacrificial layer is extended only in one direction, the force received in the vertical direction makes it easy for the shape of the second sacrificial layer to break up. As a result, a decrease in yield occurs due to the formation of unnecessary wirings in the dummy area1. Thus, utilizing the fact that the number of dummy wirings is an even number, adjacent second sacrificial layers which are formed in the dummy area1are connected in a ladder shape and the structure shown as a planar view inFIG. 7(C) is obtained.

However, in the structure shown inFIG. 7(C), when dust703and dust704which have conductive properties are attached as shown inFIG. 7(D), a wiring in the functioning area1and another wiring in the functioning area2short out.

A method for detecting whether this type of short circuit occurs is considered. For this consideration, a region which becomes equipotential by a wiring is described as a node. In addition, in order to distinguish between a wiring within a functioning area and a wiring within a dummy area, a node which describes a wiring in a functioning area is for example colored black and a node which describes a wiring in a dummy area is colored white. In addition, an insulation space between two wirings can be described as an edge which connects a node which describes these two wirings. Then, a graph structure can be obtained which corresponds to a wiring pattern. The graph shown in this graph structure is hereinafter called a pattern graph.

A pattern graph corresponding to the pattern shown inFIG. 7(C) is shown inFIG. 8(A). The subgraph on the left of the node801is a pattern graph corresponding to the functioning area1, the subgraph on the right of the node803is a pattern graph corresponding to the functioning area2and the subgraph constructed by the node802and the edges connected to the node802is a pattern graph corresponding to the dummy area1.

First, assuming that the dust703is attached, the rightmost wiring in the functioning area1and the wiring in the dummy area1get connected electrically. This situation is equivalent to a fusing together of the node804and the node803in the pattern graph and a new node804is produced as is shown inFIG. 8(B).

Next, assuming that the dust704is attached, the wiring in the dummy area1and the leftmost wiring in the functioning area2get connected electrically. In this situation, the node804and the node803fuse together in the pattern graph and a new node805is produced as shown inFIG. 8(C). Then, the dummy area1disappears from the pattern graph.

Even if the dust704is attached before the dust703, similarly the pattern graph shown inFIG. 8(C) is obtained.

Therefore, in the case where different black nodes F1and F2are connected via two edges to a white node D, D and F1fuse together, and when the fused node and F2fuse together the dummy area equivalent to D disappears and a short circuit occurs in the functioning area corresponding to F1and F2.

Therefore, in the pattern graph, when a plurality of edges are connected to a white node, if a pattern is formed so that the number of edges among the plurality of edges which are connected to a black node is at most one, a short circuit occurring via a wiring of a dummy area corresponding to this white node can be suppressed.

That is, the shape of the second sacrificial layer which is formed in a dummy area does not become one geometrically connected component and may be comprised of a plurality of connected components. This is because if the shape of the second sacrificial layer which is formed in a dummy area becomes one connected component, because the shape of a conducting material in the dummy area is expressed as one connected component, that is, one white node, two black nodes are connected to this node and when the fusing together of nodes stated above occurs twice, the subgraph of the dummy area disappears.

FIG. 9, unlikeFIG. 7, is a diagram which explains the dangers of a short occurring due to dust being attached during a process to obtain a wiring pattern by making an insulation layer into a layer to be processed, forming the second sacrificial layer on the insulation layer and performing damascene processing. As is shown inFIG. 9(A), it is assumed that the dummy area2exists between the functioning area3and the functioning area4. In order to arrange wirings in the functioning area3and the functioning area4, a plurality of second sacrificial layers902is formed above the insulation layer901within the functioning area3and the functioning area4and it is sufficient to form a second sacrificial layer902in the periphery of the dummy area2.

Then, the insulation layer901is etched using the second sacrificial layer902as a mask and as is shown inFIG. 9(B), the second sacrificial layer902is selectively etched and as is shown inFIG. 9(C), and a conducting material903is filled into the insulation film901by a damascene process.

However, in this state, a large difference of the spatial frequency of pattern and/or the density of pattern is produced between the functioning areas3and4and the dummy area2. Therefore, as is shown in the upper surface diagram inFIG. 9(D), a space904is arranged within the dummy area2and the difference in the spatial frequency becomes smaller or disappears. Even in this case, a pattern is arranged so that a pair of the spaces904is created. However, when a pattern graph is created for the pattern shown inFIG. 9(D), the pattern graph becomes the same as the pattern graph shown inFIG. 8and the fact that it becomes easier for short circuits to occur is detected.

FIG. 10(A) and (B) exemplify a resolution method for also arranging within the dummy area2a space which extends parallel up and down to the space arranged in the functioning areas3and4. Even in this case, due to the constraints due to the side wall processing, the second sacrificial layer1002for arranging an even number of spaces is arranged above the insulation layer1001within the dummy area2. Then, etching is performed using the second sacrificial layer1002as a mask, the second sacrificial layer1001is selectively removed and a conducting material1003is filled using a damascene process and a wiring is formed. The graph pattern shown inFIG. 10(E) is a graph pattern created for the pattern shown inFIG. 10(D). All of the white nodes are edges connected to a node and the number of edges connected to a black node is at most one.

Generalizing the case ofFIG. 10(E), when a second sacrificial layer formed at or beside a side wall of a first sacrificial layer formed in a functioning area, and a second sacrificial layer formed at or beside a side wall of a first sacrificial layer formed in a dummy area, are formed, it is sufficient that they are formed so that they become separated from each other. When the maximum width of a second sacrificial layer is d, it is sufficient if the distance between the first sacrificial layer formed in a functioning area and a first sacrificial layer formed in a dummy area is twice larger than d.

FIG. 11andFIG. 12are diagrams which explain a different pattern formation in a dummy area when an insulation layer is the layer to be processed. As is shown inFIG. 11(A) and (B), a first sacrificial layer1102is formed above an insulation layer1101. While in the cross sectional diagram inFIG. 11(A) one first sacrificial layer1102appears to be arranged in the dummy area, according to the upper surface diagram shown inFIG. 11(B), a first sacrificial layer is arranged in a zig zag shape in the dummy area. That is, the shape of a first sacrificial layer in the dummy area is a shape which consists of a plurality of connected elements. Then, as is shown inFIG. 11(C) and (D), slimming is performed on the first sacrificial layer1102. Then, as is shown inFIG. 11(E) and (F), a second sacrificial layer1103is formed on the side wall of the first sacrificial layer1102. Furthermore, as is shown inFIG. 11(F), arrangement and slimming of the first sacrificial layer is performed so that the second sacrificial layer which are formed on the side walls of the upper and lower first sacrificial layers are connected in the dummy area.

Then, the first sacrificial layer is selectively removed and etching is performed by etching the insulation layer1101to a certain depth using the second sacrificial layer as a mask and the structure shown inFIG. 12(A) and (B) is obtained. That is, a torus shape having a plurality of holes appears in the dummy area. The second sacrificial layer is selectively removed, a conductive material is filled by a damascene processing and the structure shown inFIG. 12(C) and (D) is obtained. The graph shown inFIG. 12(E) is a graph created for this structure. All of the white nodes are edges connected to a node and the number of edges connected to a black node is at most one.

By arranging a torus shape in a dummy area, even if a force is applied from the side of the torus shape, it is difficult to break up the shape and it becomes possible to prevent the generation of defects due to a break up of a pattern in the dummy area.

FIG. 13(A) and (B) show other examples of a pattern created in a dummy area.FIG. 13(A) and (B) show, other than a torus, shape pattern which are difficult to break up.FIG. 13(A) shows a pattern arranged in a polygonal shape such as a parallelogram or a rhombus shape. In addition, inFIG. 13(B) a pattern based on a circular shape is created in the dummy area. When a graph is made for any of the patterns, all of the white nodes are edges connected to a node and the number of edges connected to a black node is at most one, and the fact that this is a pattern in which short circuits are not generated easily is detected.

Furthermore, in the creation of a layout of a semiconductor device, first its hardware is described with a level of abstraction called an RTL (Register Transfer Level) using a hardware description language for example, based on the specification data of a semiconductor integrated circuit. Next, this description is logically synthesized using a logical synthesis tool and as a result, is developed to a level of abstraction called a gate level. That is, as a logical synthesis result it is possible to obtain data of a logic circuit diagram. Then, it is also possible to produce a net list from the data of this logic circuit diagram.

Next, a plurality of elements are arranged on an integrated circuit based on the data of this logic circuit diagram and by deciding the wiring pathways between this plurality of elements layout data is created for creating a mask. That is, the arrangement of wirings and a functioning area is decided. Then, a distribution of a spatial frequency of a pattern from this layout data is demanded.

That is, in a device for creating a layout of a semiconductor device, the distribution of the spatial frequency of a patter is investigated and a detection is performed to check whether there are places in which changes in the spatial frequency exceed a predetermined change amount. If, it is detected that a change in the spatial frequency exceeds a predetermined change amount, a warning is produced for the occurrence of microloading effects and an error message is displayed etc. In addition, if a place exists in which a spatial frequency is low, a warning is produced for the occurrence of dishing effects, the places in which design of a dummy wiring should be performed is indicated to a designer and design of the dummy wiring is automatically performed etc.

After this, a pattern graph is created, and a check is performed as to whether the conditions have been met for the number of edges connected with a node (black node) corresponding to a functioning area wiring is at most one or not, these edges being connected to a node (white node) corresponding to a dummy area wiring. If is detected that these conditions have not been met, redesign is encouraged or a design of dummy wirings is automatically performed.

In addition, because the pattern of the second sacrificial layer extends in one direction, by calculating a distribution of a pattern spatial frequency, it is possible to detect whether a pattern breaks up easily when a force is applied from the side. When a pattern extends in one direction, the direction in which the pattern extends becomes a spatial frequency value close to 0 and a perpendicular direction to this direction becomes a value larger than 0. Thus, a pattern of a semiconductor process is separated into a pattern of a functioning area and a pattern of a dummy area, a spatial frequency of a dummy area pattern is calculated, and by checking whether a value of a spatial frequency in one direction which is close to 0 is serially connected or not, it becomes possible to detect whether a pattern of the second sacrifice film connected to a dummy area breaks up easily or whether the yield of a semiconductor device is reduced.

Furthermore, as a characteristic of side wall processing a dummy wiring may easily occur in a region in which pattern periodicity of a wiring or insulation space in an integrated circuit changes. Thus, a layout pattern is analyzed and instead of distinguishing between a functioning area and dummy area, a distribution of a pattern spatial frequency is calculated and the detection is performed in a region in which a spatial frequency value exceeds a predetermined change amount. Then, based on this detection, it becomes possible to separate the dummy area and the functioning area. Based on the separation result, the dummy area pattern and the functioning area pattern are separated into different layouts for example. Then, the functioning area pattern which has been separated by this type of procedure may be verified by a design rule check. That is, the functioning area pattern is checked as to whether it conforms to geometric design rules which are designed while paying attention to each type of obtained restriction once the manufacturing process has been verified.

Generally, when a wiring pattern is separated between a functioning area and a dummy area based on the connection relationship of a wiring, a large amount of calculation is required which makes the wiring becomes very complex. However, calculation of the amount of change in spatial frequency may require a calculation amount unrelated to the complexity of the wiring. As a result, it is possible to perform separation of a functioning area and a dummy area in a short period of time and because a design rule check is not performed on the dummy area it is possible to remove the occurrence of simulated errors caused by dummy area wirings which has been indicated as a conventional problem. As a result, it is also possible to complete the design of a semiconductor device in a short period of time.

Second Embodiment

As an embodiment of the present invention, a nonvolatile semiconductor memory device which uses a NAND flash memory as a semiconductor device of one embodiment of the present invention is described below.

FIG. 14shows a block diagram of a nonvolatile semiconductor memory device related to an embodiment of the present invention. The nonvolatile semiconductor memory device1shown inFIG. 14is arranged with an I/O control circuit12, a logic control circuit13, a status register14, an address register15, a command register16, a control circuit17, a voltage generation circuit18, a row decoder19, a row address buffer20, a memory cell array21, a sense amplifier22, a data register22, a column decoder24and a column buffer25.

The I/O controller circuit12sends and receives data between external input/output terminals I/O1to I/O16and the data register23when reading data or when programming data. In addition, the I/O controller circuit12outputs address data which is input from the external input/output terminals I/O1to I/O16to the address register15when reading data or when programming data. Also, the I/O controller circuit12outputs commands supplied from the external input/output terminals I/O1to I/O16to the command register16. In addition, the I/O controller circuit12outputs status data (data for informing an external device on the various states within the chip) which is input from the status register14to an external device via the external input/output terminals I/O1to I/O16. While inFIG. 14the external input/output terminals are expressed as I/O1to I/O16so that the number of external input/output terminals is 16, an arbitrary number of external input/output terminals may be used.

The logic control circuit13outputs external control signals such as a chip enable signal CE, a write enable signal WE, a read enable signal RE, an address latch enable signal ALE, a command latch enable signal CLE and a write protect signal WP which are externally input to the control circuit17.

The status register14is a register for informing an external device on the various statuses of the chip and includes a ready/busy register which holds data which shows whether the chip is in a ready or busy status, a programming status register which holds data which shows a programming pass or fail, a programming error register which holds data which shows the existence of a program error status (program verify pass/fail) and an overwrite status register which holds data which shows the existence of an overwrite status (overwrite verify pass or fail).

The address register15decodes address data input from the I/O control circuit12, outputs a row address to the row address buffer20and outputs a column address to the column address buffer25.

The command register16outputs a command which is input from the I/O control circuit12to the control circuit17.

The control circuit17outputs a command which is input from the command register16to the voltage generation circuit18. In addition, the control circuit17performs a data program, data read and data erase control sequence of controls based on an external control signal input from the logic control circuit13and a command input from the command register16according to an operation mode.

The voltage generation circuit18is a circuit for generating various Vpp voltages (program voltage Vpgm, verify voltage Vr, program pass voltage Vpass, read voltage Vread, etc.). This voltage generation circuit18is controlled by the control circuit17.

The row decoder19includes a word line drive circuit which selects a word line of the memory cell array21and drives a word line based on a row address (page address) stored in the row address buffer20.

The row address buffer20stores a row address input from the address register15.

The memory cell array21comprises a plurality of NAND cell units. Each NAND cell unit is comprised by a memory string in which a plurality of electrically reprogrammable nonvolatile memory cells are serially connected, and a memory block which includes a plurality of NAND cell units, each NAND cell unit being connected to a selection transistor at each end. The memory cell array21is generally comprised by a plurality of memory blocks. A word line connects the control gates of nonvolatile memory cells of every NAND cell unit in a memory block. The selection gates of selection transistors are connected to a section gate line which is arranged parallel to word lines. A group of NAND cell units which share a word line comprise a memory block which is a unit of data erasure. A plurality of these memory cell blocks is included within the memory cell array21.

When reading data the sense amplifier22reads data which is stored in a nonvolatile memory cell selected by the row decoder19and the column decoder24and outputs to the data register23.

The data register23is connected with the I/O control circuit12via the I/O bus26. When reading data the data register23outputs data read via the sense amplifier circuit22to the input/output terminals I/O1to I/O16via the I/O control circuit12. In addition, when programming data the data register23outputs via the input/output terminals I/O1to I/O16and the I/O control circuit12data to be programmed, which is loaded from an external controller2, to the sense amplifier circuit22. Furthermore, the data register23may include a trimming data register (not shown in the diagram) for storing trimming data (voltage level setting data for operation voltage adjustment or clock data for clock adjustment within a memory chip) which is used when demanding/requesting a parameter which controls an operation of the memory cell array21, and a defective block address register (not shown in the diagram) which stores address data of a defective block detected as result of the above stated test operation.

The column decoder24selects a bit line of the memory cell array21based on a column address stored in the column buffer25. The column buffer25stores a column address which is input from the address register15. The I/O bus26is a bus which connects the I/O control circuit12with the data register23.

FIG. 15is a diagram which exemplarily explains a layered structure of a memory block in the memory cell array21. An insulation layer such as an oxide layer is formed on the surface of a substrate and wirings which form the select lines1501,1503and word lines1502-1,1502-2, . . . ,1502-m, formed above the substrate, are arranged above this as shown inFIG. 15(A). These select gate lines and word lines are connected to the row decoder19. Furthermore, an active region which extends in a direction perpendicular to the select gate lines and word lines is formed on the substrate using, for example, an STI (Shallow Trench Isolation) structure. The select gate lines are also functioning as gate electrodes of the selection transistors which are formed in this active region. In addition, if a nonvolatile memory cell is a memory transistor, a charge storage layer is formed between the active region and a word line.

A common source line1504is arranged on a layer above the layer in which a select gate line and a word line are arranged via an interlayer insulation material. Then, again via an interlayer insulation material, the bit lines1505-1,1505-2, and1505-nare arranged. Lines1506-1,1506-2, and1506-kwhich connect the sense amplifier22with a selector circuit27are arranged on the same layer as the layer in which the bit lines is arranged. The selector circuit27is a circuit for selecting a bit lit which is connected to a sense amplifier when the number of sense amplifiers of the sense amplifier circuit and the number of bit lines are different (generally the number of sense amplifiers is not larger than the number of bit lines).

FIG. 15(B) shows a cross sectional view of a cross section along the line A-A inFIG. 15(A). The wiring1506is connected with the selector circuit27via a contact, and the bit line1505is also connected with the selector circuit27via a different contact.

FIG. 15(C) shows a cross sectional view of a cross section along the line AA-AA inFIG. 15(B). InFIG. 15(C) the lines1506-1,1506-2, and1506-3which connect the sense amplifier circuit22and the selector circuit27are lined on the left side and the bit lines1505-1,1505-2, and1505-3are lines on the right side.

FIG. 16is a diagram which shows the structure shown inFIG. 15(C) in more detail. That is,FIG. 16shows wirings in a functioning area of a layer in which the cross section AA-AA inFIG. 15(B) is drawn. A large number of bit lines of the memory cell array21are lined in the column labeled1601and a large number of wirings which connect the sense amplifier circuit22with the selector circuit27are lined in the column labeled1602. The part labeled1603is a region between the column labeled1601and the column labeled1602and the selector circuit27is arranged on a layer above this region.

A part in which bit lines are lined consecutively similar to the part labeled1604and a part in which bit lines are not lined similar to the part1605, are lined alternately in the column labeled1601. The part labeled1605is a region in which nonvolatile memory cells are not arranged and is called a shunt region of the memory cell array21.

In addition, a part exists in which bit lines are lined consecutively similar to the part labeled1606and another part exists in which bit lines are not lined similar to the part1607and1608, in the column labeled1602. The part labeled1608corresponds to the shunt region of the memory cell array21. Because there are no bit lines in the shunt region of the memory cell array21, it is not necessary to arranged sense amplifiers in lines and there are no wirings. In addition, the part labeled1606corresponds to one group of sense amplifiers which are arranged in the sense amplifier circuit22. Also, in the case where one sense amplifier is responsible for amplification of voltages of a plurality of bit lines, a bit line and a sense amplifier no longer correspond as one pair. As a result, a region where there are no wirings as in the part labeled1607, periodically appears. As is shown inFIG. 16, generally, the width of the region labeled1607becomes smaller than the width of the region labeled1608which is a region which corresponds to the shunt region of the memory cell array21. This is because a region exists which corresponds to the region labeled1607, on both ends of the region labeled1608.

In addition, when the pitch of bit lines arranged in the column labeled1601is pbl, that is, when the width of a bit line and the width of a space between bit lines is pbl as shown inFIG. 16, and when the pitch of bit lines arranged in the column labeled1602is pb1i, generally, the relationship 2×pbl>=pbli>=pbl holds. This is because it is difficult to significantly change the width of the second sacrificial layer by side wall processing.

It is possible to create a graph of a position in a substrate and a pattern density as is shown inFIG. 3for the wiring shown inFIG. 16. A part with a high pattern density1604corresponding to pbl and a part with a low pattern density1605which corresponds to the shunt region in the memory cell array21, appears alternately in the column labeled1601. Therefore, if a dummy wiring is not created in the shunt region of the memory cell array21, a difference occurs in the pattern density.

In addition, a part with a high pattern density1606corresponding to pbli and a part with a low pattern density1605which corresponds to the regions labeled1606and1607, appear alternately in the column labeled1602. Therefore, if a dummy wiring is not created in the regions labeled1607and1608, a difference occurs in pattern density, spatial frequency, etc.

Therefore, as is shown inFIG. 17, in order to reduce this difference in pattern density, in spatial frequency, etc., the regions labeled1605,1606,1607and1608are treated as dummy areas and a dummy wiring is arranged. As stated above, because a region1701which corresponds to the region labeled1607exists on both ends of the region labeled1608, a dummy wiring of the region labeled1607is formed. In addition, if a pattern does not exist in the region labeled1703, because pattern differs significantly, a dummy pattern is formed.

By creating a dummy pattern in this way it is possible to reduce changes in pattern density and prevent an occurrence of the effects of microloading and dishing. In addition, by using side wall processing it is possible to form a pattern which exceeds resolution limits and realize a small scale semiconductor device. When side wall processing is used, unnecessary wiring were conventionally created and short circuits easily occurred via these unnecessary wirings, however, by applying an embodiment of the present invention it is possible to prevent the occurrence of these short circuits.

According to an embodiment of the present invention it is possible to prevent the occurrence of shorts circuits due to unnecessary wirings formed by side wall processing and also prevent the occurrence of microloading and dishing effects. It is also possible to realize an improvement in yield while achieving a small scale semiconductor device.