JP3611202B2 - Non-rectangular LSI layout method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-rectangular layout method performed using a rectangular LSI automatic layout tool.
[0002]
[Prior art]
As an indispensable technology that has supported the development of large-scale integrated circuits (LSIs) in recent years, there is an automatic design technology. Layout design that places and routes semiconductor circuit cells on a wafer based on circuit design as one stage of LSI design is critical for determining the success or failure of LSI design because the resulting chip size directly affects LSI cost. It is an important step. Therefore, in the automatic layout design, ingenuity has been made to collect the layout area into as small a rectangle as possible so that LSI can be extracted from the wafer without waste.
[0003]
In digital LSI, a technique for designing an LSI using a group of standard cells as semiconductor circuit cells has been established. Further, in large-scale LSI development, a method of designing a designed LSI layout as one LSI block and combining such an LSI block or memory circuit block with a standard cell is common.
[0004]
In an analog LSI, unlike a digital circuit design that can be described in binary logic, a design method similar to a digital LSI design using standard cells is not necessarily advantageous from the viewpoint of total cost including development costs. Rather, in recent years, LSI applications in various fields are overwhelmingly demanded for hybrid LSIs that combine analog functions with digital LSIs, so one analog function is separately designed as one LSI block. A method of designing these analog LSI blocks in combination with standard cells together with other LSI blocks has become common.
[0005]
[Problems to be solved by the invention]
In the design of such a hybrid LSI, the layout shape of the LSI block is given in advance, and this and the automatic design block using standard cells must be combined into one chip. However, since analog LSI blocks are designed with priority given to the consideration of analog electrical characteristics, they do not necessarily have a convenient shape for combination with a digital automatic layout.
[0006]
Even in such a case, the conventional digital LSI automatic layout tool is a rectangular target tool. Therefore, when LSI blocks that do not perform automatic layout in LSI design occupy most of the chip, the layout is performed. There is a possibility that useless empty space may occur between LSI blocks.
[0007]
On the other hand, it is conceivable to perform digital automatic layout in a non-rectangular form. However, since the LSI automatic layout tool that has been used in the past only targets the rectangular layout shape, even if an attempt is made to implement a non-rectangular layout. The input data necessary for layout cannot be read.
[0008]
The present invention solves the above-described conventional problems, and it is possible to use a rectangular LSI automatic layout tool for the layout of a non-rectangular LSI block using standard cells, thereby generating unnecessary empty space in the LSI layout. An object of the present invention is to provide a non-rectangular LSI layout method that can eliminate the problem.
[0009]
[Means for Solving the Problems]
In the non-rectangular LSI layout method according to claim 1 of the present invention, a step of obtaining a minimum rectangular region including the non-rectangular region by adding an additional region circumscribing the block boundary of the non-rectangular region to be laid out (100) ), Changing the pin position of the non-rectangular area in contact with the additional area to the pin position of the rectangular area in contact with the additional area, and making the additional area a cell placement prohibited area (103) And (104) performing cell placement using the rectangular area as a layout area, and in the additional area, corresponding pins of the pin position before the non-rectangular area change and the pin position after the rectangular area change. A step (106) of providing a wiring prohibition region excluding a wiring region that enables only wiring to be connected, and a step of wiring using the rectangular region as a layout region ( 07), a step (108) of changing a block boundary of the layout area from the rectangular area to the non-rectangular area after layout of the rectangular area, and a pin position of the rectangular area after the layout of the rectangular area. And a step (110) of returning to the pin position of the non-rectangular LSI using the rectangular LSI automatic layout tool.
[0010]
According to the non-rectangular LSI layout method of claim 1, a rectangular area is obtained by adding an additional area to the non-rectangular area to be laid out, and the pin position is changed in accordance with the rectangular area, and a cell is added to the additional area. By designating the layout prohibition or wiring prohibition area, the rectangular LSI automatic layout tool can recognize the non-rectangular area as the rectangular area, and the layout of the non-rectangular LSI block is performed using the rectangular LSI automatic layout tool. It becomes possible.
[0011]
An LSI layout method according to a second aspect of the present invention is the non-rectangular LSI layout method according to the first aspect, wherein when the cell power supply and ground wiring are laid out in the additional area, the additional area is laid out after the rectangular area is laid out. This includes a step (109) of deleting the power supply and ground wiring of the cell in the area.
[0012]
According to a non-rectangular LSI layout method according to claim 2, in the non-rectangular LSI layout method according to claim 1, when cell power and ground wirings are laid out in an additional area, the addition is performed after the rectangular area is laid out. The power supply and ground wiring of the cells in the area can be deleted, and the redundant portion generated when the layout of the non-rectangular LSI block is performed using the rectangular LSI automatic layout tool can be deleted.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing a non-rectangular LSI layout method using a rectangular LSI automatic layout tool according to an embodiment of the present invention. 2 to 11 are views for explaining the LSI layout corresponding to each step of the flowchart shown in FIG.
[0014]
In FIG. 1, step 100 is a step of obtaining a minimum rectangular area including a non-rectangular area by adding an additional area outside the non-rectangular area to be laid out. Step 100 will be described with reference to FIGS. FIG. 2 shows a non-rectangular area to be laid out and has a block boundary 202 of the non-rectangular area. FIG. 3 shows a minimum rectangular area including the non-rectangular area of FIG. 2, and has a block boundary 301 of the rectangular area. FIG. 4 shows an additional area 400 added outside the block boundary 202 of the non-rectangular area in order to obtain a rectangular area having the block boundary 301 from the non-rectangular area having the block boundary 202.
[0015]
Step 101 is a step of changing the pin position of the non-rectangular area in contact with the additional area added in step 100 to the pin position of the rectangular area. Step 101 will be described with reference to FIGS. In FIG. 2, 200 indicates a pin position that does not need to be changed because it is not in contact with the additional area 400, and 201 indicates a pin position that is to be changed because it is in contact with the additional area 400. In FIG. 3, 300 indicates the pin position of the rectangular area after the pin position is changed. Since the rectangular LSI automatic layout tool can recognize only the data of the rectangular area, in step 102, the rectangular LSI pin layout data obtained by the change is read into the rectangular LSI automatic layout tool.
[0016]
Step 103 is a step in which the additional region added in Step 100 is set as a cell placement prohibited region. Step 103 will be described with reference to FIGS. 4 and 5. Since the additional area 400 in FIG. 4 is an area that does not exist in the actual non-rectangular area to be laid out, the additional area 400 is designated as the standard cell arrangement prohibited area 500.
[0017]
Step 104 is a step of arranging standard cells in a rectangular area. Step 104 will be described with reference to the standard cell layout shown in FIG. Since the additional area 400 is designated as the standard cell arrangement prohibition area 500 in step 103, when the standard cell is arranged in step 104, the standard cell 501 is arranged in accordance with the shape of the block boundary 202 of the non-rectangular area. The However, since the rectangular LSI automatic layout tool recognizes the layout shape at the block boundary 301 of the rectangular area, it does not recognize the block boundary 202 of the non-rectangular area.
[0018]
Step 105 is a step of performing power supply / ground wiring of the standard cell. The process 105 will be described with reference to the power / ground connection diagram of the standard cell shown in FIG. In FIG. 6, the power and ground lines of the standard cell are wired by the power / ground wiring 600 previously set as a fixed pattern for the standard cell. FIG. 6 shows a case where the power supply / ground wiring is also performed in the standard cell arrangement prohibited area 500 as a result of mechanical power supply / ground wiring.
[0019]
Step 106 is a step of designating a wiring prohibited area as the additional area. The step 106 will be described with reference to the designation diagram of the wiring prohibited area of the standard cell shown in FIG. Since the additional area 400 is an area that does not exist in the non-rectangular area to be actually laid out, it must be designated as a wiring prohibited area. However, since the pin position 201 is changed to the pin position 300 in step 101, the pin position 300 must be wired.
[0020]
In step 106, as shown in FIG. 7, for the N pins changed from the pin position 201 to the pin position 300, only N wirings connecting the corresponding pins at the pin position 201 and the pin position 300 are provided. In order to enable this, N + 1 standard cell wiring prohibition areas 700 are specified on the additional area 400 with a space between each other. In FIG. 7, N wiring areas 701 separating the standard cell wiring prohibition area 700 are areas whose widths are set so that only one wiring is possible.
[0021]
Step 107 is a step of wiring standard cells. Step 107 will be described with reference to FIG. When the standard cell wiring is performed in step 107, the rectangular LSI automatic layout tool performs the wiring by recognizing the layout shape at the block boundary 301 of the rectangular area, but in step 106, the standard cell wiring prohibition area 701 is placed on the additional area 400. As a result, the standard cell wiring 802 is wired in accordance with the shape of the block boundary 202 in the non-rectangular area. In addition, each pin at the pin position 300 changed from the pin position 201 in step 101 is routed through the respective wiring regions 701 via the respective pin positions 201 before the change.
[0022]
Step 108 is a step of changing the block boundary of the rectangular area to the block boundary of the non-rectangular area. Step 108 will be described with reference to FIG. Up to step 107, in order to perform standard cell placement and wiring automatic layout processing, it was necessary for the rectangular LSI automatic layout tool to recognize the layout shape at the block boundary 301 of the rectangular area, but the automatic layout processing was completed. Thus, in step 108, the layout shape is returned to the block boundary 202 of the original non-rectangular area. FIG. 9 is a diagram in which the block boundary 301 of the rectangular area is changed back to the block boundary 202 of the non-rectangular area.
[0023]
Step 109 is a step of deleting the power / ground wiring of the standard cell remaining in the additional region. Step 109 will be described with reference to FIG. FIG. 10 is a diagram showing a case where the power / ground wiring of the standard cell is also applied to the additional region in step 105, and the redundant power / ground wiring 1001 must be deleted. When the redundant power supply / ground wiring 1001 is deleted in step 109, the area where the power / ground wiring 600 of the standard cell remains coincides with the non-rectangular area indicated by the block boundary 202.
[0024]
Step 110 is a step of returning the pin position changed from the pin position 201 to the pin position 300 in step 101 to the original pin position in accordance with the block boundary of the non-rectangular region. Step 110 will be described with reference to FIG. In FIG. 11, the pin position 1101 is a part of the pin position 300 that has been changed from the pin position 201 in step 101. In Step 109, the wiring portion wired to the pin position 1101 through the wiring area 701 in Step 107 is deleted, so that the wiring from the non-rectangular area to the pin position 201 remains, and the pin position 1101 becomes the block boundary of the non-rectangular area. The original pin position 201 can be moved.
[0025]
As described above, according to the present embodiment, a procedure for obtaining a rectangular area by adding an additional area to a non-rectangular area, a procedure for changing the pin position according to the rectangular area, A non-rectangular layout can be performed using the rectangular LSI automatic layout tool by adding a procedure for designating the placement prohibited area and the wiring prohibited area and a procedure for deleting unnecessary portions after the automatic layout processing of the standard cell.
[0026]
【The invention's effect】
As described above, according to the present invention, by adding an additional area to the non-rectangular area to obtain a rectangular area, the rectangular LSI automatic layout tool is made to recognize the non-rectangular area data as rectangular area data, and the additional area By designating the standard cell placement prohibition area and the wiring prohibition area, it is possible to avoid unnecessary placement and routing of the standard cell in the additional area, and the non-rectangular layout using the rectangular LSI automatic layout tool. Can be realized.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a non-rectangular LSI layout method using a rectangular LSI automatic layout tool according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining a non-rectangular region and its pin position.
FIG. 3 is a diagram illustrating a rectangular area and its pin position.
FIG. 4 is a diagram for explaining an additional region and its pin position.
FIG. 5 is a diagram for explaining an arrangement prohibition area of standard cells and an arrangement of standard cells;
FIG. 6 is a power cell / ground pin connection diagram of a standard cell.
FIG. 7 is a view for explaining designation of a wiring prohibited area of a standard cell.
FIG. 8 is a wiring diagram of a standard cell.
FIG. 9 is a diagram for explaining a block boundary change from a rectangular area to a non-rectangular area.
FIG. 10 is a diagram for explaining deletion of a power supply / ground wiring of a standard cell.
FIG. 11 is a diagram illustrating a change in pin position from a rectangular area to a non-rectangular area.
[Explanation of symbols]
200 Pin position 201 of non-rectangular area that does not need to be changed Pin position 202 of non-rectangular area that needs to be changed Block boundary 300 of non-rectangular area Pin position 301 of rectangular area after change Block area 400 of rectangular area Additional area 500 Standard cell Standard cell 600 Standard cell power supply / ground wiring 700 Standard cell wiring prohibition area 701 Single wiring possible wiring area 802 Standard cell wiring 1001 Standard cell power supply / ground wiring 1101 Step 101 Pin position of the rectangular area changed by

Claims (2)

In a non-rectangular LSI layout method performed using a rectangular LSI automatic layout tool,
Obtaining a minimum rectangular area containing the non-rectangular area by adding an additional area circumscribing the block boundary of the non-rectangular area to be laid out;
Changing the pin position of the non-rectangular area in contact with the additional area to the pin position of the rectangular area in contact with the additional area;
Making the additional region a cell placement prohibited region;
Performing cell placement using the rectangular area as a layout area;
A step of providing a wiring prohibition area in the additional area, except for a wiring area that enables only a wiring connecting pins corresponding to the pin position before the change of the non-rectangular area and the pin position after the change of the rectangular area; ,
Wiring the rectangular region as a layout region;
Changing the block boundary of the layout area from the rectangular area to the non-rectangular area after the layout of the rectangular area;
Returning the pin position of the rectangular area to the pin position of the non-rectangular area after the layout of the rectangular area;
A non-rectangular LSI layout method comprising: In the layout of the rectangular area, when cell power and ground wiring are laid out in the additional area, a step of deleting the power and ground wiring of the cell in the additional area after layout of the rectangular area is included. The non-rectangular LSI layout method according to claim 1.

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