JPS632153B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying the resistance value of a resistor including a semiconductor layer, such as a resistor including a diffusion layer, and particularly relates to a method for modifying the resistance value of a resistor including a semiconductor layer, and in particular a resistor made of a metal provided directly or indirectly in a predetermined region of the diffusion layer. The present invention relates to a resistance value correction method for continuously and highly accurately correcting the resistance value of a resistor including at least one electrode.

Conventionally, anodization methods, laser trimming methods, and the like have been proposed as methods for modifying the resistance value of thin film resistors used in hybrid integrated circuits. Furthermore, in monolithic integrated circuits, a method has been proposed in which the resistance value is modified by using polycrystalline silicon as a resistor and passing a current through the resistor.

However, no method has yet been proposed for directly modifying the resistance value of a resistor including a diffusion layer, which is often used as a resistor in monolithic integrated circuits. The following method has been proposed as a method for indirectly modifying the resistance value of a resistor including a diffusion layer. That is, the first
As shown in Fig. 1, the method is as follows:
Then, a plurality of adjusting diffused layer resistors 3 having a small resistance value are connected in series to this via bonding pads 2 to form a resistor, and the bonding pads 2 at both ends of the adjusting diffused layer resistors 3 are connected with thin aluminum wire or the like. There is a method of modifying the resistance value by sequentially shorting the bonding wire 4 to obtain the desired resistance value.
As a second method, as shown in FIG. There is a method of modifying the resistance value by fusing the aluminum wiring 5 with a laser to obtain the desired resistance value. However, in either method, the resistance value can only be modified discretely, the modification accuracy is poor, and the area occupied by the resistor becomes large due to the need for a diffusion layer resistance for adjustment, making it difficult to apply to LSI. The drawback was that it was difficult to improve the degree of integration. Furthermore, when realizing an analog LSI using the conventional resistance value correction method, there were drawbacks such as an increase in cost due to the adjustment resistance.

An object of the present invention is to provide a resistance value correction method that allows the resistance value of a resistor to be adjusted continuously and with high precision.

Another object of the present invention is to provide a resistance value correction method that does not require an adjusting resistor and is suitable for high integration.

In order to achieve the above object, the resistance value correction method of the present invention includes: a semiconductor layer having a resistance value lower than the target resistance value; a first electrode made of metal provided on a predetermined region of the semiconductor layer; and a second electrode provided on another predetermined region of the semiconductor layer, the first electrode of the resistor is an anode, the second electrode is a cathode, and a DC current is passed through the resistor to generate a resistor. It is characterized by modifying the resistance value of the body.

Hereinafter, the present invention will be explained based on examples.

FIG. 3 is a plan view of a resistor used in the resistance value correction method of the present invention, and FIG. 4 is a sectional view taken at XX' in FIG. 10 is a substrate, for example, n-type single crystal silicon with a crystal orientation (100) and a resistivity of 10 to 20 Ωcm;
is a semiconductor layer formed on the substrate 10, for example, by diffusing phosphorus as an impurity into the substrate 10, the depth of the diffusion layer is about 2.9 μm, the surface concentration is about 1×10 ²¹ cm ^-8 , and its resistance value is the objective. is lower than the resistance value of
12 is a metal containing the constituent element of the semiconductor layer 11 (silicon in this case) and vacancy, such as aluminum (hereinafter abbreviated as "Al (Si)"), which is formed by a sputtering method and contains 2 to 3% silicon. The first electrode 12 has a thickness of 1.5 μm, and the first electrode 12 is an insulating film 1 deposited on the surface of the semiconductor layer 11 and the substrate 10.
3, and the other end of the semiconductor layer 11 is in direct contact with the second electrode 16 through another contact hole 15 formed in the insulating film 13. There is. The second electrode may be made of metal such as Al (Si), or may be made of polycrystalline silicon or amorphous silicon.

The first electrode 12 of the resistor configured as shown in FIG. 4 is an anode, the second electrode 16 is a cathode, and the current value is much larger than the current actually used in the resistor, for example, the average current density at the contact is 4×10 ⁴ A/ ^cm2
A direct current of . When a large direct current is passed through the resistor in this way, the current density becomes high at the end 17 where the first electrode 12 and the semiconductor layer 11 are in contact, and the electrons flowing from the semiconductor layer 11 to the first electrode 12 are Since the silicon (hereinafter abbreviated as "Si") in one electrode is moved, the Si concentration in the end portion 17 decreases, and the Si in the substrate 10 is eluted into the first electrode 12 to compensate for this. As a result, the end 17 of the substrate 1
A void is formed in 0. At the same time, end 1
Aluminum (hereinafter referred to as “Al”) in the first electrode 12 of No. 7
It is abbreviated as ) also flows into the first electrode 12 due to the inflowing electrons.
You can move inside. At this time, the movement of Al is the first
The process progresses as the vacancy and Al existing in the electrode 12 are replaced, and this vacancy moves to the end 17 and a large number of vacancies gather to form the end 17.
A void is formed in the first electrode 12 of.

FIG. 5 shows the cross section of the resistor after a large DC current is applied and voids are formed, and 18 is the void formed by the current flow.
18a is a void in the substrate 10, and 18b is a void in the first electrode 12. The length of this void increases as the DC current value increases and as the current conduction time increases. In the resistor with the structure shown in Fig. 5, since no current flows in the void, the first electrode 1
Since the length of the current path between the void 18 and the second electrode 16 is longer than that of the structure shown in FIG. 4 by approximately the length l of the void 18, the resistance value of the resistor increases. Therefore, by appropriately setting the energization time and energizing the DC current, the resistance value of the resistor can be modified by a predetermined value to obtain the desired resistance value. Furthermore, since the resistance value is corrected depending on the length of the void 18 formed, the resistance value can be corrected continuously and accurately.

In the above embodiment, when direct current is applied to the resistor, the resistor may be placed in a constant temperature bath and the current may be applied while the ambient temperature of the resistor is maintained at a certain high predetermined temperature, for example, 300°C. In this way, when the ambient temperature of the resistor is high and the current is applied, due to the synergistic effect of self-heating due to the application of DC current and the ambient temperature,
Since the movement of Si or Al (hereinafter referred to as "electromigration") can be easily caused and voids can be formed in a shorter time, the resistance value can be corrected in a shorter time. However, this temperature is the material that makes up the first electrode 12.
It is necessary that the temperature is such that Al (Si) does not react with the substrate 10, for example, about 450° C. or lower.

Although the resistor used in the above embodiment had the structure shown in FIG. 4, a resistor having the structure shown in FIG. 6 may also be used. That is, the semiconductor layer 11 is connected through the contact hole 14 formed in the insulating film 13.
Ohmic contact layer 19 and diffusion barrier layer 2
A first electrode is provided through 0. For example, titanium with a thickness of 500 Å is used as the ohmic contact layer 19, and a material such as titanium nitride, which has a resistivity sufficiently larger than that of the first electrode 12 and is less likely to cause electromigration, is used as the diffusion barrier layer 20. The thickness shall be 500Å. Other parts having the same configuration as those in FIG. 4 are given the same numbers and their explanations will be omitted.

FIG. 7 is a cross-sectional view of a resistor having such a structure after a large DC current is passed through the resistor. Although the Si in the first electrode 12 is moved by the inflowing electrons, the presence of the diffusion barrier layer 20 prevents the Si in the substrate 10 from moving to the first electrode 12, and no voids are formed in the substrate 10. On the other hand, Al in the first electrode 12 is moved by the inflowing electrons, and voids 18 are formed in the first electrode 12. In this way, voids are formed only in the first electrode 12 and no voids are formed in the substrate 10, so it is possible to prevent disconnection of the semiconductor layer 11 due to voids and to eliminate the adverse effect on the resistance value of the semiconductor layer. Therefore, variations in correction of the resistance value of the resistor can be reduced and the resistance value can be corrected with higher accuracy.

Also, since the sum of the resistance values of the ohmic contact layer 19 and the diffusion barrier layer 20 and the resistance value of the semiconductor layer 11 is the resistance value of the resistor, the resistance value of this example is higher than that of the previous example. The rate of change is small. Therefore, even if there is a slight variation in the energization time, the variation in the resistance value can be extremely reduced, so that the resistance value can be corrected with higher precision. Furthermore, according to this embodiment, since the first electrode 12 is not in direct contact with the substrate 10, the ambient temperature of the resistor can be made higher than in the first embodiment, and as a result, the It is possible to modify the resistance value over time. In addition, in the above two embodiments, the first electrode is
It may be Al that contains vacancy and does not contain Si,
It may also be a material that is prone to electromigration. Platinum silicide may also be used as the ohmic contact layer.

FIG. 8 shows the relationship between the rate of change in resistance value and the current application time when current is applied at a current density of 4×10 ⁴ A/cm ² with the ambient temperature of the resistor being 300°C. a
is the case when Al (Si) is used as the first electrode,
b is a characteristic diagram when the first electrode is made of Al (Si) and an ohmic contact layer 19 and a diffusion barrier layer 20 are provided between the first electrode 12 and the semiconductor layer 11.
As shown by curve a, the longer the current application time, the greater the rate of change in resistance value. Therefore, a resistor having a desired resistance value can be obtained by applying a direct current for an appropriate period of time to correct the resistance value to be greater than the resistance value at the time of forming the resistor element. Since curve b shows a gradual change in the rate of change in resistance value over time compared to curve a, this shows that highly accurate resistance value control is possible even if the energization time varies somewhat.

FIG. 9 shows the relationship between void length and resistance value change in a semiconductor device having a structure exhibiting the characteristic of curve a in FIG. 8. The vertical axis is the first electrode 12
The value obtained by dividing the length l of the void 18 by the distance L from the end of the second electrode 16 to the end of the second electrode 16 is shown, and the horizontal axis shows the rate of change in resistance value. From the figure, it can be seen that as the length of the void 18 formed by energization increases, the change in resistance value increases.

It is necessary that the resistance value of the resistor whose resistance value has been corrected as described above hardly fluctuates due to the current applied during subsequent use. By the way, it is well known that the conditions under which the electromigration used in the present invention occurs is according to the following equation.

t=A/J ² exp (Ea/kT) A is a constant, J is a current density, Ea is an activation energy, k is Bornoman's constant, and T is an absolute temperature.
From this equation, it is possible to estimate the stability of the resistance value under actual usage conditions. In other words, when the actual current density is 4×10 ³ A/cm ² and the actual operating temperature is 50°C,
When the activation energy is 1.4 eV, the time required to show the same resistance change as characteristic a in Figure 8 is approximately 10 ^{to 11} times the energization time for the resistance change, and in actual use there is almost no resistance change. There will be no.

FIG. 10 shows an example of a circuit including a resistor when the resistance value modification method of the present invention is applied to a semiconductor device or LSI, and is an example of a circuit when modifying the base resistance of a transistor. 21 is a transistor, 22 is a resistor connected to the base, 23
are pads connected to the first and second electrodes of the resistor, respectively.

As explained above, according to the present invention, the first
Since the electrode is used as an anode and direct current is passed through the resistor to generate voids and the resistance value of the resistor is adjusted based on the length of the void, the resistance value can be adjusted continuously and with high precision. There are advantages.

Furthermore, since an extra resistor for adjustment unlike the conventional resistor is not required, the area occupied by the element can be reduced and the degree of integration can be improved. In particular, in analog LSIs, there is no need to use expensive adjustment resistors that were conventionally required, so the present invention has various advantages such as the ability to realize small, high-density analog LSIs at low cost.

[Brief explanation of the drawing]

1 and 2 are plan views of a resistor used in a conventional resistance value correction method, FIG. 3 is a plan view of a resistor used in an embodiment of the resistance value correction method of the present invention, and FIG. Figure 3 is a cross-sectional view of the resistor, Figure 5 is a cross-sectional view of the resistor in Figure 4 after the resistance value has been corrected, and Figure 6 is a cross-sectional view of the resistor in Figure 4.
The figure is a sectional view of a resistor used in another embodiment of the resistance value correction method of the present invention, FIG. 7 is a sectional view of the resistor after the resistance value of the resistor in FIG. A diagram showing the relationship between the rate of change in the resistance value of a resistor and the energization time,
FIG. 9 is a diagram showing the relationship between void length and rate of change in resistance value. FIG. 10 is an example of a circuit when the present invention is applied to an LSI. DESCRIPTION OF SYMBOLS 10... Substrate, 11... Semiconductor layer, 12... First electrode, 13... Insulating film, 14, 15... Contact hole, 16... Second electrode, 18, 18a, 18b... Void, 19... Ohmic contact layer, 20... Diffusion barrier layer.

Claims (1)

[Claims] 1. A semiconductor layer having a resistance value lower than a target resistance value, a first electrode made of metal provided on a predetermined region of this semiconductor layer, and a first electrode provided on another predetermined region of the semiconductor layer. Resistance value correction that corrects the resistance value of a resistor by generating a void by passing a direct current through the resistor, with the first electrode of the resistor having a second electrode as an anode and the second electrode as a cathode. Law. 2. A resistance value correction method according to claim 1, characterized in that a resistor is used in which the first electrode is provided in direct contact with a predetermined region of the semiconductor layer. 3. The resistance value correction method according to claim 1, characterized in that the first electrode uses a resistor provided in a predetermined region of the semiconductor layer via an ohmic contact layer and a diffusion barrier layer. Resistance value correction method.