JPS5913343A - Redundancy circuit device - Google Patents

Abstract

PURPOSE:To enable a writing to a conductive state from a non-conductive state at a high rate of success by forming a p-n junction under a reverse bias state diffused and formed from the surface of a semiconductor substrate and a protective film of specific film thickness formed to the surface of the substrate on the junction section. CONSTITUTION:An n type impurity is diffused to the substrate 11 from the opening section of a field silicon oxide film 12, and an n type diffusion region 15 of approximately 0.5mum diffusion depth is formed. The substrate 11 and the diffusion region 15 are each wired properly so that the p-n junction section formed by the diffusion region 15 and the semiconductor substrate 11 is brought to a reverse bias state. The protective film 14 of a silicon oxide film is formed to the whole surface on the substrate 11 in film thickness of 0.5mum or more. When YAG pulse laser beams are irradiated selectively to said p-n junction section, they do not scatter when the thickness of the protective film 14 is made 0.5mum or more, a crystal is damaged, and stable junction leakage currents Il are obtained positively. when the diffusion depth of said n type diffusion region 15 reaches 1.0mum or more, the p-n junction is made difficult to be damaged through laser irradiation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a redundant circuit device, and is particularly used for bipolar LSIs, MOS-LSIs, and the like.

[Technical background of the invention and its problems]

Today, the integration of semiconductor devices is remarkable, and in the case of memories, an extremely large number of memory bits are now housed in a single product. With this increase in integration, if a small amount of defective pits occur in the memory of the main circuit, a redundant circuit is formed as a backup circuit in advance, and the defective bits are electrically replaced with redundant bits in the redundant circuit. Redundancy technology is employed.

The following redundancy techniques are used. The one shown in FIG. 1 (at (bl) is an example of a blowout type, in which a polysilicon wiring 13 that will serve as a fuse for a redundant circuit is formed on a field silicon oxide film (5i02 film) 12 formed on a silicon substrate J1. For example, a silicon oxide film (CVD5I02 film) is deposited on the upper surface of the substrate 1 as a protective film 4 by the CVD method.

When writing defect information of the memory bit of the circuit to such a fuse, the radar light is connected to this polysilicon 1.
2 (a) (b)
Fuse as shown. However, if this is done, the protection 1114 will also be scattered at the same time when the fuse blows out, and the reliability of this semiconductor device will not be adversely affected.

In addition, to eliminate such drawbacks, it may be possible to make a hole in the laser beam irradiation area of the protective film 14 in advance by photo-etching or etching, but in this case, Na There is a risk that contaminant ions of grade 10 may enter through the openings.

In addition, impurities are intensively implanted into a part of the undoped I silicon wiring to form an impurity non-diffused part, and when writing redundant bits corresponding to defective bits, the non-diffused part is filled with impurities. There is also a conductive type that irradiates a laser beam with a certain energy to diffuse impurities and change the silicon wiring from a non-conductive state to a conductive state. However, in this case, it is highly dependent on subtle changes such as misalignment of the laser beam irradiation position and power fluctuation, and the probability of successful impurity diffusion is as low as about 50, which is inconvenient for mass production. There were drawbacks.

[Purpose of the invention]

This invention was made in view of the above points, and it is possible to change a non-conductive state to a conductive state with a high success rate without creating an opening or damaging the protective film formed on the top surface of a semiconductor substrate. It is an object of the present invention to provide a configurable conduction type redundant circuit device.

[Summary of the invention]

That is, the redundant circuit device according to the present invention includes a pH junction in a reverse bias state formed by diffusion from the surface of a semiconductor substrate;
The thickness of the film formed on the substrate surface above this pH junction is 0.5 μm.
The protective film described above is provided, and when the crystal at the pH junction is damaged by laser beam irradiation, the non-conductive state is set to the conductive state.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, a field silicon oxide film 12 having an opening is formed on a p-type semiconductor substrate 11, and an n-type impurity is diffused into the substrate 1 through the opening to a depth of approximately 0.5 μm.
An n1li diffusion region 15 is formed with a diffusion depth of . The pH value formed by this diffusion region 15 and the semiconductor substrate 11 is
The substrate 11 and the diffusion region 15 are appropriately wired so that the junction portion is in a reverse bias state. Furthermore, this board 11
A protective film 14 of a silicon oxide film is formed on the entire upper surface by a CVD method to a thickness of 0.5 μm or more.

In such a device, the diffusion region 15 and the semiconductor substrate 11 are normally set in a reverse bias state and are in a non-conductive state. Here, when the pH junction between the diffusion region 15 and the substrate 11 is selectively irradiated with YAG/Ruslede light, the crystal near the pH junction is damaged without scattering the protective film 14, causing leakage and leakage current Il.
! flows. In this way, in the above embodiment, several nA~
It was possible to pass a severe reverse leakage current. FIG. 4 shows the relationship between the laser energy, the spot diameter (diaphragm) of the laser beam, and the leakage current 11 flowing through the pH junction when the central part of the diffusion region 15 is irradiated with Radical light.

Furthermore, when irradiating the diffusion region 15 with laser light, it is better to irradiate the laser light toward the periphery of the diffusion region 15 as shown in FIG. In some cases, in order to cause leakage with a small amount of energy and to obtain a reliable and stable leakage current 14 without scattering the protective film 14, the protective film 14 must be
．． It has been found that a film thickness of 5 μm or more is required.

Furthermore, although the diffusion depth of the n-type diffusion region 15, that is, the depth of the pH junction part, was set to 0.5 μm, the diffusion depth was 1.0 μm.
In this case, it becomes difficult to damage the pn junction by radar irradiation.

As described above, a pH junction is formed, and for example, as shown in FIG. 5, the substrate I in FIG. By doing so, the potential at the connection point 18 between the resistor 16 and the pn junction (diode 17) can be changed from VDDl in the non-laser beam irradiation state to approximately OV after the laser beam irradiation.

Therefore, it is sufficient to prepare several elements as shown in FIG. 5 as redundant bits of the memory of the main circuit, and to write the defective part of the memory into the redundant bits to prevent malfunction of the main circuit.

In the above embodiment, the protective film 14 formed on the n-type diffusion region 15 was a silicon oxide film. A laminated film with an oxide film may be deposited as a protective film, and the substrate 1 and the diffusion region may be constructed of a conductivity type opposite to that of the above embodiment. Furthermore, it is clear that the pn junction may be formed by diffusing an impurity of the opposite conductivity type into a -conductivity type diffusion region formed in the substrate, for example. The wiring of the pn junction is not limited to that shown in FIG. 5, and the wiring of the pn junction may be made of aluminum metal, polysilicon, or the like.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to change a semiconductor device from a non-conductive state to a conductive state with a high success rate without causing any damage or damage to the upper film or protective film of the semiconductor device. It is possible to provide a writable redundant circuit device, and if the laser beam irradiation state is appropriately set, the writing efficiency can be stably increased to 10.
0 chips, which greatly contributes to the productivity of semiconductor products such as memories.

[Brief explanation of drawings]

Figure 1 (at (bl) is a cross-sectional view and plan view showing a conventional redundant circuit device before blowout, Figure 2 (fa) (bl)
3 is a sectional view and a plan view respectively showing a conventional redundant circuit device after fusing, FIG. 3 is a sectional view illustrating a redundant circuit device according to an embodiment of the present invention, and FIG. 4 is a switch of laser energy and laser beam. FIG. 5 is a diagram showing the relationship between diameter and leakage current I, 7, and is a circuit diagram illustrating a redundant circuit device according to an embodiment of the present invention. 1)... Semiconductor substrate, 12... Field silicon oxide film, 14... Protective film, 15... N-type diffusion region,
15...Resistor, 17...Diode. Applicant's representative Patent attorney Takehiko Suzue Figure 1 (a) 3 (a) Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A semiconductor substrate of one conductivity type, a diffusion layer of an opposite conductivity type, and a protective film having a thickness of 0.5 μm or more formed on the diffusion layer, wherein the semiconductor substrate and the diffusion layer are reverse biased. A redundant circuit device characterized in that the pn junction of is changed from a non-conductive state to a conductive state by irradiation with Raded light.