JPH0828422B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a redundant circuit, and more particularly to a structure of a guard ring of a fuse portion for activating the redundant circuit.

2. Description of the Related Art In recent years, with the progress of miniaturization and increase in the degree of integration of semiconductor devices, it has become difficult to avoid structural defects, and it has become extremely difficult to maintain the yield at a high level. Therefore, in a semiconductor memory device represented by a dynamic RAM, a redundant circuit is mounted and the defective bit due to the defect is replaced with a spare bit to prevent a decrease in yield. Activation of the redundant circuit is performed by cutting and programming the fuse forming the spare decoder according to a selection signal for accessing the defective bit, and replacing the spare bit connected to the spare decoder with the defective bit.

As a method of cutting the fuse which constitutes the preliminary decoder, there are an electric fusing and a cutting by a laser beam, but at present, a cutting by a laser beam is the mainstream. In the case of laser light cutting, the final protective film on the fuse is often opened in advance and removed to improve the cutting success rate. Thus, since the final protective film on the fuse is excluded, there is a high possibility that the external operation will adversely affect the circuit operation. For this reason, conventionally, FIG. 2 (a), (b)
A guard ring structure as shown in Fig. 3 was provided to surround the fuse.

The conventional guard ring structure of the semiconductor device will be described below with reference to FIGS. 2 (a) and 2 (b). FIG. 2 (a)
FIG. 2B is a plan view of a fuse portion including a guard ring of a conventional semiconductor device, and FIG. 2B is a sectional view taken along the line AA ′ of FIG.

In FIGS. 2A and 2B, reference numeral 1 is a first diffusion layer arranged on the semiconductor substrate 3 so as to surround the cut portion 2A of the fuse 2 provided to activate the redundant circuit. 2 is provided across the first diffusion layer 1. Further, the first diffusion layer 1 is covered with a first aluminum wiring 4, and the first diffusion layer 1 and the first aluminum wiring 4 are in contact with each other through a plurality of contact windows 5. Reference numeral 6 denotes a second diffusion layer surrounding the first diffusion layer 1 and disposed on the semiconductor substrate 3, and the fuse 2 has the second diffusion layer 6
Is also provided across. Further, the second diffusion layer 6 is covered with a second aluminum wiring 7, and the second diffusion layer 6 and the second aluminum wiring 7 are in contact with each other through a plurality of contact windows 8. The first diffusion layer 1 and the first aluminum wiring 4 constitute an inner card ring 9, and the second diffusion layer 6 and the second aluminum wiring 7 constitute an outer guard ring 10. The guard ring 9 is connected to a power source that generates a negative voltage via the first aluminum wiring 4, and the outer guard ring
Reference numeral 10 is connected to a power supply that generates a positive voltage via the second aluminum wiring 7. In this way, the thermal oxide film 111 below the fuse cutting portion 2a is cut off from the thermal oxide film 12 outside the guard rings 9 and 10, and a double guard ring is formed.
By generating an electric field between 9 and 10, mobile ions such as Na ⁺ from the fuse cutting part 2A are captured in the electric field so that the circuit operation is not adversely affected. In FIG. 2, 13 is an interlayer film, 14 is a final protective film, and the final protective film 14 on the fuse cutting portion 2A is removed.

However, according to the conventional structure, in the environment in which the voltage cannot be applied to the guard rings 9 and 10 (for example, high temperature storage state, long-term storage state in a wafer state before assembly, etc.), the guard ring 9 , 10 and diffusion layers 1, 6 and aluminum wiring 4, 7
Partly comes into contact only with the contact windows 5 and 8, the inter-layer film 13 is scattered on the guard rings 9 and 10, and the fuse 2 also linearly crosses the double anti-spatter layers 1 and 6. The distance between the fuse cutting part 2A and the interlayer film 13 of the internal circuit is shortened, and mobile ions may reach the internal circuit through the interlayer film 13, which may adversely affect the circuit operation.

The present invention is to solve the above problems, and an object of the present invention is to provide a semiconductor device having a guard ring structure having an enhanced guard effect against movable ions even in an environment in which a voltage cannot be applied to the guard ring. is there.

Means for Solving the Problems In order to solve the above problems, the present invention is a semiconductor device having a redundant circuit, which is arranged so as to surround a cut portion of a fuse provided for activating the redundant circuit. A first impurity layer, a first wiring that covers the first impurity layer and is in contact with the first impurity layer except a portion where the fuse crosses the first impurity layer; A second impurity layer disposed so as to surround the first impurity layer and the second impurity layer, and contacts the second impurity layer except at a portion where the fuse crosses the second impurity layer. And a second wiring for the second impurity layer of the fuse, and the first and second impurity layers of the fuse are arranged so as not to be aligned in a straight line.

Effect With the above configuration, the impurity layer forming the guard ring contacts the wiring over the entire area except for the portion where the fuse crosses the impurity layer of the guard ring, so that diffusion occurs through the interlayer film scattered in the guard ring as in the conventional case. The movable ions are blocked, and the fuse is bent between the inner impurity layer and the outer impurity layer, and the position of the crossing portion is displaced, so the linearity of the interlayer film formed along the fuse is The probability of stopping at the outer guard ring becomes higher for mobile ions that have passed through the interlayer film of the inner guard ring at the crossing portion of the fuse.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a fuse portion including a guard ring of a semiconductor device showing an embodiment of the present invention. The same components as those shown in FIGS. 2A and 2B of the conventional example are designated by the same reference numerals and the description thereof will be omitted. First and second impurity layers
The structure of the diffusion layers 1 and 6 is the same as that of the conventional example, except that the diffusion layers 1 and 6 constituting the guard rings 22 and 23 are the same as those of the diffusion rings 1 and 6 except where the fuse 21 crosses. The aluminum wirings 4 and 7 are in contact with each other over the entire area. In FIG. 1, 24 indicates a contact portion between the first diffusion layer 1 and the first aluminum wiring 4, and 25 indicates a contact portion between the second diffusion layer 2 and the second aluminum wiring 7. Further, the fuse 21 is bent between the inner guard ring 22 and the outer guard ring 23 so that the transverse portion of the first diffusion layer 1 and the transverse portion of the second diffusion layer 6 of the fuse 21 are aligned. The inner guard ring 22 along the fuse 21 should be staggered so that it does not
The interlayer film and the interlayer film of the outer guard ring 23 are not arranged in a straight line.

In this way, the contact area between the diffusion layers 1 and 6 of the guard rings 22 and 23 and the aluminum wirings 4 and 7 is increased, so that the area of the interlayer film of the guard rings 22 and 23 is decreased and the movable area passing through the interlayer films is reduced. The amount of ions is kept extremely low, and the linearity of the interlayer film at the fuse crossing formed along the fuse 21 is broken, so that the guard ring inside the fuse crosses even in an environment where voltage cannot be applied. twenty two
The probability of stopping at the outer guard ring 23 for mobile ions that have passed through the interlayer film can be increased. Therefore, it is possible to reduce the influence of mobile ions on the circuit operation,
A highly reliable semiconductor device can be provided.

Incidentally, in an environment in which a voltage can be applied from the outside, as in the conventional example, it is possible to apply a voltage having different polarities to the guard ring 22 and the guard ring 23 to supplement mobile ions.

As described above, according to the present invention, against contamination from the outside by mobile ions such as Na ⁺ from the cut portion of the fuse,
In addition to the environment in which a voltage can be applied to the guard ring, the area of the interlayer film of each impurity layer and wiring that composes the guard ring should be adjusted in areas other than the fuse crossing the impurity layer, even in environments where voltage cannot be applied. The contact ring reduces the linearity of the interlayer film formed along the fuse by arranging them so that the impurity layers of the fuse are displaced so that they are not aligned in a straight line. The probability of blocking mobile ions that diffuse through the film can be increased, the guard effect can be demonstrated more than before, and high reliability is ensured even if the integration degree is improved, while the yield is not reduced and the cost is low. The semiconductor device can be provided.

[Brief description of drawings]

FIG. 1 is a plan view of a fuse portion including a guard ring of a semiconductor device according to an embodiment of the present invention, and FIGS. 2A and 2B are plan views of a fuse portion including a guard ring of a conventional semiconductor device. And FIG. 1 ... first diffusion (impurity) layer, 4 ... first aluminum wiring, 6 ... second diffusion (impurity) layer, 7 ... second
Aluminum wiring, 21 ... Fuse, 22 ... Inner guard ring, 23 ... Outer guard ring, 24 ... Contact portion between first diffusion layer and first aluminum wiring, 25 ... Second
Of the diffusion layer and the second aluminum wiring.

Claims (1)

[Claims] 1. A semiconductor device having a redundant circuit, comprising:
A first impurity layer disposed to surround a cut portion of a fuse provided for activating the redundant circuit and the first impurity layer, and the fuse covers the first impurity layer. A first wiring contacting the first impurity layer at a portion other than the crossing portion, a second impurity layer arranged so as to surround the first impurity layer, and covering the second impurity layer, and A second wiring in contact with the second impurity layer at a portion other than a portion where the fuse crosses the second impurity layer,
A semiconductor device in which the cross section of the first impurity layer and the cross section of the second impurity layer of the fuse are arranged so as not to be aligned in a straight line.