JP2751742B2 - Cell for automatic layout - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask pattern design for a semiconductor integrated circuit, and more particularly to an automatic layout cell for a standard cell type semiconductor integrated circuit.

[0002]

2. Description of the Related Art Conventionally, a primitive cell for automatic layout of a standard type semiconductor integrated circuit has a constant cell outer shape and a constant width of a power supply and a ground wiring included in the cell.

FIG. 4 shows a result of a conventional automatic layout of a semiconductor integrated circuit block. In the wiring region 3, the wiring is generally densely formed at the center portion for performing the wiring between the cell regions 3, and the height of the wiring region 3 is determined by the dense portion. Further, the height of the cell region 3 is constant. Further, the power supply wiring 1 and the ground wiring 2 are provided at both ends of the cell region 3.
Is provided.

[0004]

As described above, the primitive cell for automatic layout has a constant outer shape of the cell and a constant width of the power supply wiring and the ground wiring included in the cell. Power and ground are provided from both ends of the cell area.

[0005] Now, at both ends of the cells arranged in the same cell row, it is necessary to supply power and ground to the inner cells, so that the power supply wiring and the ground wiring need to be thick. However, in the central cell, since it is not necessary to supply power and ground to other cells, the power supply wiring and the ground wiring may be thin, but have the same thickness at both ends.

Accordingly, as a result, the power supply wiring and the ground wiring become thicker than necessary in some places, particularly in the central part, and the height direction of the semiconductor integrated circuit block becomes large.

When the area is increased in this way, there is a problem that the cost of the semiconductor integrated circuit increases.

An object of the present invention is to provide an automatic layout cell with an improved degree of integration.

[0009]

In order to achieve the above object, an automatic layout cell according to the present invention is an automatic layout cell of a standard cell type semiconductor integrated circuit comprising a combination of a plurality of primitive cells. The cell has a power supply wiring and a ground wiring, and the thickness of the power supply and the ground wiring is set according to the minimum current capacity of the power supply wiring and the ground wiring determined by the position of the primitive cell.

[0010]

The thickness of the power and ground wiring in the primitive cell is changed according to the minimum current capacity of the power and ground wiring determined at the time of arranging the primitive cell.

[0011]

Next, the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a layout diagram showing Embodiment 1 of an automatic layout cell according to the present invention.

In FIG. 1, as primitive cells,
With the same function, the widths of the power supply wiring 1 and the ground wiring 2 are different, and three types of type S, type M, and type L are facilitated. Are set according to the minimum current capacities of the power supply wiring 1 and the ground wiring 2 determined by the arrangement positions of the primitive cells.

Therefore, an appropriate primitive cell is selected according to the position where the primitive cell is arranged.
Further, the size of the primitive cell differs depending on the width of the power supply wiring 1 and the ground wiring 2.

FIG. 2 shows the result of automatic layout of blocks using the primitive cells for automatic layout according to the present invention. Since power and ground are supplied from both ends, it is necessary for cells near both ends to supply power and ground to cells inside the cell.

Therefore, the power supply wiring and the ground wiring use the type L which is thicker than the inner cells. Conversely, the cell near the center does not need to supply power and ground to others, so the power and ground widths are narrow,
A type S having a smaller cell size is used.

In the example shown in FIG. 2, primitive cells of type L are arranged at both ends 1/6 of the cell area in the same column, and primitive cells of type S are arranged at the center 1/3. A primitive cell of type M is arranged in a region sandwiched between the type M and the type S.

It should be noted that, contrary to the primitive cell size, in the wiring region 4, the center is more dense than the vicinity of both ends. This is due to the fact that when trying to connect each primitive cell with the shortest distance, the wiring has a higher rate of passing through the central portion than near both ends. In general, the height of the wiring region 4 is determined by the number of horizontal wirings in the central part. Therefore, the area of the block is surely reduced by reducing the size of the primitive cell in the central part.

As described above, by arranging and wiring a primitive cell having a size determined by the coordinates from among a plurality of primitive cells according to the coordinates (distance from both ends) at which the primitive cells are always arranged, A layout with a high degree of integration can be realized.

(Embodiment 2) FIG. 3 is a layout diagram showing Embodiment 2 of the present invention.

In the present embodiment, a plurality of primitive cells having the same function but different widths of the power supply wiring 1 and the ground wiring 2 are prepared, and an appropriate primitive cell is selected depending on the position where the primitive wiring is arranged.

In this embodiment, unlike the first embodiment, the size of the primitive cell is the same, but the primitive cell has a region where horizontal wiring can be performed, and as a result, the wiring region can be supplemented. .

Also, unlike the first embodiment, the size of the primitive cell itself does not change. Therefore, there is an advantage that the automatic layout tool can be used even when cells having different heights cannot be arranged.

[0024]

As described above, in the automatic layout cell according to the present invention, the thickness of the power supply wiring and the ground wiring in the primitive cell is changed in accordance with the arrangement conditions, so that the characteristics are not deteriorated. In addition, unnecessary power supply wiring and ground wiring can be eliminated, the element density in the semiconductor integrated circuit can be improved, and cost increase can be prevented.

[Brief description of the drawings]

FIG. 1 is a layout diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a state where layout is performed using primitive cells according to the first embodiment of the present invention.

FIG. 3 is a layout diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a layout state of a conventional example.

[Description of Signs] 1 power supply wiring 2 ground wiring 3 cell area 4 wiring area

Claims (1)

(57) [Claims] 1. A cell for automatic layout of a standard cell type semiconductor integrated circuit comprising a combination of a plurality of primitive cells, wherein the primitive cell has a power line and a ground line, and the thickness of the power and ground lines is A cell for automatic layout, which is set in accordance with a minimum current capacity of the power supply wiring and the ground wiring determined by a position of the primitive cell.