JPS5877098A - Programmable read-only memory element - Google Patents

Abstract

PURPOSE:To realize a fine and high-density PROM with improved designing tolerance, by providing a wiring layer of the 1st material which generates heat with electric conduction and the 2nd and 3rd wiring layers which are set opposite to the 1st wiring layer via an insulated film and made eutectic with the heat generated from the 1st wiring layer. CONSTITUTION:The 1st wiring layer 30 having conductivity is formed on an insulated film 20 on a semiconductor substrate 10. The 2nd wiring layer 50 of Al is provided on the layer 30 via an insulated layer 40, and a disconnecting part 70 which disconnects the layer 50 on a counter part 60 with a prescribed space. Then the 3rd wiring layer 80 of amorphous silicon is formed across the part 70 of the layer 50. When a program current is supplied to the layer 30 in a program function mode, the layer 30 functions as a heating element. Thus the layers 50 and 80 are made eutectic at the part 60 to form an eutectic region 100 with an extremely low level of resistance value. As a result, a fine and high- density PROM element is obtained.

Description

[Detailed Description of the Invention] Technical Field> The present invention is directed to Progera! Pull read only memory element (hereinafter referred to as FROMg element) K,! ! IIK
The present invention relates to a FROM element based on the ``Site→'' method.

<Prior Art> In recent years, with the progress of conductor LSIs including FROM elements, the demand for them has been increasing. In the case of a FROM element, it is not only used as a FROM-L8I, but also as a so-called redundancy (R@duuda) of a memory LSI or logic L81.
na7: redundancy) circuit, sunawa1 is being used for defect relief circuits.

Typical conventional FROM elements include:

■ PNfi14rK of the diode The current that performs writing by passing an excessive current through the PN junction. ■ The current that performs writing by flowing a current through the phase element and blowing it out. There are two types: a phase type, and a radar fuse type in which writing is performed by cutting the 73--Z element with a laser beam.

Of these, the combination sheet method PROM element fabrication 2 of
The current 7-unit FROM elements require very large currents to program together.

For example, the specific numerical value of the required pregtum current is approximately 100,100 for the junction site → method (2), and several tens (mA) for the 1-ugly phase method. This typically requires bipolar transistors with high amplification.

In addition, in order to apply a PIIOM element that requires Mo2 L8 IK, it is necessary to use M08 for current drive with a very large channel width.
Since a transistor is required and therefore a large area is occupied, it has been difficult to achieve high integration in the FROM elements of the above-mentioned 1 and 20 systems.

On the other hand, in the case of the radar fuse method FROM g-child of No. 3,
The program is programmed by cutting a predetermined program position using a laser beam.
An expensive programming device such as a dynamic position detection device is required.

Under such circumstances, the current phase type FROM element (2), which is the most typical FROM element, has the above-mentioned drawbacks, but it is the simplest for program processing, and its merits are that the Vc limit using the FROM element is That's worthy of praise. Therefore, we will consider the current phase method.

FIG. 1 is a diagram showing a 7-phase element part of the conventional 7-phase current system, where (a) is its equivalent circuit, and (a) is a structural diagram given in plan. (& ), when a current is passed between terminals 1 and 2, the phase element F melts, and this melting causes the 0(b
), the phase element 1 is formed of, for example, a polycrystalline silicon layer.

The end portion 5.6 of the 7-is element r has an arunium (hereinafter,
It is abbreviated as muj. ) The wiring 7.8 and the wire 7.8 are connected to each other, and are spread out relative to the fuse element IPK.The ends 5 and 6 are provided with a large bond contact 3.4,
It is connected to the A wiring 7.8 in this hole.

In addition to the above-mentioned drawback (difficulty in achieving high integration), such conventional FROM elements also have problems in the design, workability, and reliability of the fuse element r due to the fact that it is blown out by current flow. This problem is the first K7:
The fusing mechanism of the fuse element has not been sufficiently eliminated, and secondly, the fuse element must be heated above its melting point, so the phase height of the fuse element is low! It is caused by heat damage to the 1 more
The 7Aze element is used to attack Pudgebage (PaBlv) at the time of sm.
Therefore, the present invention solves the above-mentioned drawbacks, and also has the disadvantage that it is not reliable because it cannot be covered with an atlon film (protective film). A FROM element that has excellent performance, can reduce the current required for programming, has excellent reliability, and has a high design margin! To provide! <Summary of the structure of the invention> In order to achieve the above object, a FROM element according to the present invention comprises a conductive first wiring layer made of a first material and a second material. A state in which the second wiring layer and the second wiring layer are placed facing each other with an insulating film interposed therebetween (for example, overlapping each other), a disconnection part is provided in the second wiring layer in the opposing part, and the disconnection part is straddled between both ends of the second wiring layer. A third wiring layer made of a third substance is formed in contact with the second wiring layer.
The first wiring layer is selected to have a melting point sufficiently lower than the melting point of the substance, and by supplying electricity to the first wiring layer, the first wiring layer is made to act as a heating element, and the heat generation is manipulated, and the material is connected to the second substance in the opposing portion. Proceed with the eutecticization of the m-question of 3,
This lowers the electrical resistance between both ends of the broken wire in the w&3 anchor layer.

It is configured to be more programmable.

With such a structure, the fuse element is formed by the second and third wiring layers, and the programming operation (i.e., energization) K
The fuse element, whose conductivity changes instead of melting, and the heating element (first wiring layer) to which the programming current is applied are insulated and separated by an insulating film.
The heat generated by the first wiring layer, which serves as a heating element, is sufficient to locally eutectic the gap between the second and third wiring layers (phase elements) (therefore, the current required for programming can be controlled). It can be made smaller and generates less heat, which reduces thermal damage to the surrounding area.
In addition, since the current is small, the transistor that drives the program current can also be made smaller, which contributes to the promotion of higher density.0 In addition, the eutectic process is a relatively static physical phenomenon. In order to proceed, the PI will not be allowed to use the badge page.
It is possible to set up a programmer while covering the IOM element, so that it is possible to provide a FROM element with high design margin and excellent reliability. The present invention will be explained based on illustrated embodiments.

[Structure] FIG. 2 is a plan view showing the main parts of an embodiment of the FROM element according to the present invention, FIG. 3 is a sectional view taken along
The figure is a VI-Vl sectional view.

An insulating film made of, for example, a saponified silicone film or a silicon nitride film is grown on the semiconductor substrate 10 (
Figures 3 and 4).

On the insulating film I, a first wiring layer (material) having a thickness of about 5000 Aln and having conductivity is patterned into a band shape. The material used for the first wiring layer 30 is low-resistance n+ type or p+ type polycrystalline silicon, and other materials include high melting point metals (MO, Pt, etc.).

W, Ta, etc.) or high melting point metal silicide (silicide),
or? or P1 type single crystal silicon, etc. can be used.

An insulating film made of, for example, a silidine oxide film or a silicon nitride film with a thickness of several hundred amps is grown on the first wiring layer (FIGS. 3 and 4).

A thickness of about 8 cm is applied on the first wiring layer (material) through this insulating film.
A second wiring layer (material) of 000 μm is provided by vapor deposition in a state where it intersects with the first wiring layer I. Therefore, the first wiring layer and the second wiring layer I are arranged facing each other with an insulating film ω interposed therebetween. are in a relationship where On this opposing portion ω, the second wiring layer is disconnected with a predetermined gap (approximately 1 μm) (disconnection portion 70). As the material used for the second wiring layer 50, aluminum metal (hereinafter abbreviated as AI) is used.

Straddling between both ends of the rigid wire portion 70 of the second wiring layer (material),
A third wiring layer (material) is arranged on the second wiring layer 50VCI (FIG. 4). This third wiring layer (material) enters into the plane of the disconnection, and is therefore also stacked facing the first wiring layer 30 with the insulating film interposed therebetween. 3rd wiring layer (capital) K
The material used is amorphous silicon with a thickness of approximately 8,000 mm. When stacking layers, one thing to be careful of is the temperature of the semiconductor substrate 10! A eutectic temperature body of the second wiring layer group and the third wiring layer lead! and 81, the temperature must be maintained below 580°C).

The 1st eg2. Third wiring layer 3
0.50.80 A protective film for pudgebage training is grown on the entire surface, and the protective film is formed of, for example, phosphor glass with a thickness of 1 meter. Next, FRO consisting of the above configuration
The program operation of the M element will be described. Programming is performed by passing a current of about several milliamperes through the first wiring layer. That is, the first wiring layer acts as a heating element (heater).

The generated heat is transferred to the second part through the insulating film in the opposing part 60.
The wiring layer 50 and the third wiring layer (to) are heated. Please note that the melting point of the first wiring layer I itself (for example, 14
The current must be controlled so that it does not reach 20"C)K.

Due to the heating by the first wiring layer 30, the insulating film 4
0 intervening between the second wiring layer and the third wiring layer (material) in the four opposing parts 60 at a eutectic temperature (580°C
) or more can be increased by Vct 0 As shown in FIG. ,
Due to the formation of the opening toward the eutectic region where the eutectic region side is formed, the electrical resistance of the second wiring layer, which was almost disconnected before the program, decreased from 10"Ω to about (material) Ω or less, In other words, the resistance ratio before programming and after programming is approximately 10 to 1, and the second wiring layer group as a fuse element is effectively programmed from a non-conductive open state to a conductive short-circuit state. This is the reason.

Next, an equivalent circuit of the above FROM element is shown in FIG. 6(a).葎) is PR in the open state before programming.
An ON element is shown, and 弽) shows a FROM element in a short-circuited state after programming. H indicates a heating element disposed in the first wiring layer 30, and F indicates a phase element disposed between the second and third wiring layers 80. In the above explanation, a single FROM element was explained. A memory cell array can be constructed by using a plurality of these FROM elements. Figure 7K.

To make a 0p quadrogram showing an example of a memory cell array in which FROM elements are arranged in rows and columns] R+eR*..., R1 and C
I e c, e..., Cj') Select the combination,
By applying a voltage between R and C, any 7A element Flj is shortened. The terminals (tjl) and (1j2) of each phase element P1j are respectively connected to other LS1 circuit sections and used as memory elements. <Effects of the Invention> As described above, according to the present invention, the phase element ( 2nd, 3rd
The wiring layer) and the heating element (first wiring layer) through which the progelatin current flows are placed facing each other while being insulated and separated via the insulating film.Therefore, the fuse element utilizes this L 8 ' Programming can be performed while connected to the I circuit without energizing the fuse element itself. In this respect, unlike the conventional current fuse method, programming can be performed by directly energizing the phase element. What is a thing?
0, which increases the degree of freedom of the PRO/M element.
5 In addition, it is sufficient that the progelatin current is applied to the heating element in an amount sufficient to generate the heat necessary to cause a eutectic state between the second and third wiring layers constituting the phase element.
This value may generally be several mA or less. This value is approximately 1/10 of the value in the case of the conventional current phase method.

Furthermore, the temperature required for the heating element itself is low, and the thermal damage to the surroundings due to the generated heat is lower than that of the conventional current 7.
! This can be significantly reduced compared to the L-Z type, and is therefore suitable for miniaturization and high density of KFROM elements and current drive elements that drive FROM elements.

In addition, the eutectic process between the second wiring layer and the wiring layer of the iris 3 progresses statically due to the physical mechanism compared to the fusing process of the current phase method, so it is highly designable.

Furthermore, the FROM element of the present invention can be programmed while covered with a protective film for padding, that is, an insulating film, and in this respect, the conventional current 7.
High reliability can be obtained compared to the AIDS element.

[Brief explanation of the drawing]

11a shows a conventional current-fused type 7:L-Z element, so (→ is its equivalent circuit diagram, 彽) is its plan view, and FIG. 2 is a plan view showing the main structure of the PROM element according to the present invention. , Fig. 3 is the I-cut diagram in Fig. 2, Fig. 4 is the If-IV sectional view in Fig. 2, and Fig. 5 is the I-IV cross-sectional diagram in Fig. 2.
Figure 6 is an equivalent circuit diagram of the PROM element according to the present invention, and (1) is a circuit diagram showing the state before programming, and (3) is the state after programming. FIG. 7 is an equivalent circuit diagram showing an example of a matrix memory array using PROM elements according to the present invention. (Capital)...First wiring layer, 40...Insulating film, (Capital) 1
2nd wiring layer, (A)... Opposing part, Chicken... Disconnected part, (
Figure 3, Figure 4, Figure 5, Figure 6, Figure 7

Claims (1)

[Scope of Claims] 1. A first wiring layer made of a conductive first substance and generating heat when energized; disposed opposite to the first wiring layer with an insulating film interposed therebetween;
A second wiring layer made of the substance of Strain 2, which is disconnected at the opposing part or near the part 7, and a third wiring layer, which is in contact with the second wiring layer and is disposed astride between both ends of the disconnected part. a third wiring layer made of a substance, the second and third substances are substances that become eutectic due to the heat generated by the first wiring layer, and the eutectic temperature is equal to the first
A programmable read-only memory element 02, characterized in that the melting point of the substance is sufficiently lower than the melting point of the substance described in claim 1. 3.41 The device according to claim 1, wherein the first material is polycrystalline silicon having a beam image resistance. A programmable lead-only fist-shaped element characterized by being made of a high-melting point metal or a silinide of a high-melting point metal. 4. A programmable read-only memory device according to claim 1, wherein the first material is N-type or P-type single crystal silicon. The device according to claim 1, 2, or 3, characterized in that the second material is a combination of aluminum metal and the material of the irises 3 is high-resistance cricon. Programmable read-only memory element. 649 Claims 1, 2, 3 or JI
g4. A read-only memory element according to item g4, characterized in that the second material is a combination of aluminum metal and the third material is N-type silicon. 7.41 Claims 1, 2, 3, J4,
In the device according to item 5 or 6, the first wiring layer and the second wiring layer are arranged to face each other in a state where they intersect with each other. Memory/Element.