JPS62165340A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To cut fuses for a redundant circuit with a focusing ion beam without inflicting irradiation damage on semiconductor elements in the vicinities of the fuses and to contrive the improvement of element characteristics and the integration degree by a method wherein, with the focusing ion beam used for the cutting of the fuses, the installing places of the fuses are separated from the semiconductor elements as such as a prescribed distance. CONSTITUTION:In order to make a semiconductor memory provided with fuses for a redundant circuit, first a memory cell array 12 consisting of a plurality of semiconductor elements (such as MOS transistors) is formed on a semiconduc tor substrate 11. Moreover, an auxiliary circuit 13 consisting of a plurality of semiconductor elements and the redundant circuit consisting of a plurality of the fuses 14 are formed on the substrate 11 independent of the memory cell array 12. Here, the fuses 14 for the redundant circuit are formed at the positions separated about 15mum from the semiconductor elements of the auxiliary circuit 13. Then, a defective bit in the memory cell array 12 is detected and the fuse 14 for the redundant circuit, which corresponds to the defective bit, is cut with a focusing ion beam 15.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method of manufacturing a semiconductor device equipped with a fuse for a redundant circuit, and particularly relates to a method of manufacturing a semiconductor device having a fuse for a redundant circuit, and in particular a semiconductor device in which the fuse for the redundant circuit is cut by a focused ion beam. The present invention relates to a method for manufacturing a device.

[Technical background of the invention and its problems]

In semiconductor devices equipped with fuses for redundant circuits, such as semiconductor memories, when a defective bit occurs, the fuse for the redundant circuit is cut and the defective bit is replaced with a spare bit to relieve the defect caused by the defective bit. and increasing its manufacturing yield.

And, in order to cut the fuse for the redundant circuit, conventionally,
A laser beam or the like is used. In this case, since the laser beam has a relatively large diameter of several microns, it is necessary to space the fuses apart from each other on the diameter of the laser beam, which causes a reduction in the degree of integration.

Therefore, the inventors of the present invention solved the problem by cutting the fuse for the redundant circuit.
The idea was to use a focused ion beam. This focused ion beam can be focused to a submicron level, and even when it is focused to this level, the fuse for the redundant circuit can be sufficiently blown. Therefore, in this case, the distance between the fuses for the redundant circuit can be sufficiently shortened, and the degree of integration of the semiconductor device can be improved.1. I: Q However, this type of method has caused the following problems. That is, the focused ion beam irradiated to the fuse for the redundant circuit may damage the semiconductor element near the fuse and deteriorate the characteristics of the element. Irradiation damage to semiconductor devices by focused ion beams will not occur if the fuses and semiconductor devices are kept extremely far apart, but in that case, semiconductor devices equipped with fuses for redundant circuits will be correspondingly larger, making it difficult to use focused ion beams. The advantage of using it is lost.

(Object of the Invention) The present invention has been made by taking advantage of the above-mentioned circumstances, and its object is to use focused ion beams without damaging the semiconductor elements near the fuse for the redundant circuit. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can cut the fuse and improve device characteristics and integration.

The gist of the present invention is to use a focused ion beam to cut fuses for redundant circuits, and to place the fuses at a predetermined distance from the semiconductor elements.

That is, in the present invention, a semiconductor integrated circuit formed by integrating a plurality of semiconductor elements, a spare circuit consisting of a plurality of semiconductor elements, and a redundant circuit consisting of a plurality of fuses are formed in advance on a substrate, and the semiconductor integrated circuit is In the method for manufacturing a semiconductor device, the fuse of the redundant circuit corresponding to a semiconductor element that has failed in the circuit is cut off, and the redundant circuit is replaced with an element of the spare circuit to repair the defective element. In this method, the fuse is placed at a distance of 15 [μm] or more from the semiconductor element, and a focused ion beam is used as a means for cutting the fuse.

〔Effect of the invention〕

According to the present invention, since the redundant circuit fuse is installed at a distance of 15 μ711 or more from other semiconductor elements, even when the fuse is cut by a focused ion beam, the semiconductor elements near the fuse are No radiation damage occurs. Therefore, it is possible to prevent the characteristics of the semiconductor element from deteriorating, and it is possible to improve the characteristics of the element. moreover,
Since a focused ion beam is used, the distance between the fuses can be shortened, which is also effective in improving the degree of integration.

[Embodiments of the invention]

Before explaining embodiments, the basic principle of the present invention will be explained.

In order to examine radiation damage to a semiconductor element when a focused ion beam is irradiated near the semiconductor element, the present inventors conducted the following experiment. An N-MOS transistor is used as the semiconductor element, and an accelerating voltage of 30 is used as the focused ion beam.
A GEi focused ion beam with [KV] and a beam diameter of 0.8 [μm] was used.

Further, the beam irradiation amount was set to irradiation I (3×10 18 C#1'2) necessary for cutting the fuse for the redundant circuit.

First, as shown in FIG. 3, a plurality of MOS transistors 30 each consisting of a gate 31 and sources/drains 32 and 33 were formed on a semiconductor substrate by a well-known process. Then, in each transistor 30, the focused ion beam 35 was irradiated to positions separated by different distances from the gate 31. FIG. 4 shows changes in gate threshold voltage VT in drain current-gate voltage characteristics of each transistor 30 after irradiation. In addition, in FIG. 4, the horizontal axis is the distance from the gate 31 of the position irradiated with the focused ion beam 35 x
[μm], and the vertical axis indicates the change in threshold voltage ΔVT [V]. From this result, it can be seen that if the focused ion beam 35 is irradiated at a distance of 15 L μm or more from the gate 31 of the transistor 30, the characteristics of the transistor 30 will not change.

Therefore, in a semiconductor device equipped with a fuse for a redundant circuit, the fuse for the redundant circuit is separated from the semiconductor element by 15 [μ
If the fuses are installed at a distance of more than m], even if the fuse is cut by a focused ion beam, there will be no damage to semiconductor elements near the fuse.

Hereinafter, a method according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In order to create a semiconductor memory equipped with a fuse for a redundant circuit, a structure as shown in FIG. 1 was first formed. Here, in FIG. 1, 11 is a semiconductor substrate, and this substrate 1
A memory cell array 12 consisting of a plurality of semiconductor elements (for example, MOS I-transistors) was formed on the semiconductor device 1 . Furthermore, apart from the memory cell array 12, a preliminary circuit 13 consisting of a plurality of semiconductor elements and a plurality of fuses 1 are provided on the substrate 11.
A redundant circuit consisting of 4 was formed. Here, the fuse 14 for the redundant circuit is approximately 15 mm from the semiconductor element of the spare circuit 13.
They were formed at positions separated by [μm].

Next, a defective bit is detected in the memory cell array 12, and a redundant circuit fuse 1 corresponding to the defective bit is connected.
4 was cut by a focused ion beam 15 as shown in FIG. The conditions such as the acceleration voltage, beam diameter, and irradiation amount of the focused ion beam 15 at this time were the same as described above. As a result, the semiconductor element of the spare circuit 13 near the fuse for the redundant circuit was not damaged by radiation, and the defect caused by the defective bit could be repaired.

In this way, according to this embodiment, the fuse 1 for the redundant circuit
4 at a position 15 [μm] away from the semiconductor element of the preliminary circuit 13, the fuse 14 can be cut by the focused ion beam without causing radiation damage to the semiconductor element. Therefore, not only can defective bits in the memory cell array 12 be repaired, but also device characteristics and integration can be improved.

Note that the present invention is not limited to the method of the embodiment described above. For example, the distance between the fuse for the redundant circuit and the semiconductor element is not limited to 15 [μm],
It is sufficient if it is more than that. However, considering the degree of integration, a value close to 15 [μm] is desirable. Further, the semiconductor integrated circuit is not limited to a memory cell array, but may be any circuit that uses a plurality of semiconductor elements in parallel. Furthermore, conditions such as the acceleration voltage, beam diameter, and irradiation amount of the focused ion beam can be changed as appropriate. others,
Various modifications can be made without departing from the spirit of the invention.

[Brief explanation of drawings]

1 and 2 are for explaining a method for manufacturing a semiconductor memory according to an embodiment of the present invention.
The figure is a schematic diagram showing a state in which a fuse is blown by a focused ion beam. Figures 3 and 4 are for explaining the basic principle of the present invention. Figure 3 is a plan view showing the schematic configuration of a MOS transistor. The figure is a characteristic diagram showing the change in threshold voltage with respect to the irradiation position of the focused ion beam. 11... Semiconductor substrate, 12... Memory cell array (
semiconductor integrated circuit), 13... reserve circuit, redundant circuit fuse, 15... focused ion beam, 30... MO
S transistor, 31...gate, 32...source, 33...drain, 35...focused ion beam. Applicant's agent Patent attorney Takehiko Suzue=9- Figure 1

Claims (2)

[Claims] (1) A semiconductor integrated circuit formed by integrating a plurality of semiconductor elements, a spare circuit formed from a plurality of semiconductor elements, and a redundant circuit formed from a plurality of fuses are formed in advance on a substrate, and in the semiconductor integrated circuit In the method of manufacturing a semiconductor device, the fuse of the redundant circuit corresponding to a semiconductor element that has become defective is cut off, and the redundant circuit is replaced with an element of the spare circuit to repair the defective element. A method for manufacturing a semiconductor device, characterized in that the fuse is placed at a distance of 15 [μm] or more from the fuse, and a focused ion beam is used as means for cutting the fuse. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor integrated circuit is a memory cell array.