JPS5936829B2 - Resistor for DA converter integrated circuit and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resistor for a D-A converter integrated circuit having a plurality of resistor elements whose resistance values sequentially change at a constant rate, and a method for manufacturing the same.

Various D-A converter integrated circuits For example, in an in-line 8-bit D-A converter integrated circuit as shown in Figure 1, one precision resistance element is required for each bit, and the Nth resistance element is The resistance value is the lowest resistance value R.
It is necessary to increase the amount by 2N-1 times, that is, 128 times. Therefore, the resistance pattern is the same, and the resistance value is R.

, 2Ro, ......128Ro, etc., in order to form a resistor that varies by three orders of magnitude, it is necessary to vary the resistivity of each resistor element over a range of three orders of magnitude. However, it has conventionally been almost impossible to simultaneously form a plurality of resistive elements having different resistivities over such a large range. Alternatively, it is possible to simultaneously form resistors with three orders of magnitude different values by changing the resistance pattern, but in that case, the length must be changed by three orders of magnitude, or the width must be changed by three orders of magnitude. , it was still unrealistic. These problems are particularly important when integrating circuits, making it difficult to miniaturize. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a resistor that can be used in a D-A converter integrated circuit and can be miniaturized by eliminating the drawbacks of the conventional resistor, and a method for manufacturing the resistor.

In order to achieve this object, in the present invention, a plurality of resistive film elements made of fine particles oriented in the same direction are embedded in an insulating layer on the top of a semiconductor integrated circuit substrate, and wiring electrodes of this substrate are embedded. The plurality of resistive film elements are electrically connected to one part and installed in different directions, and the resistance values of the plurality of resistive film elements are set to values that sequentially change stepwise at a constant ratio. do.

In addition, fine metal particles are created using an evaporation method in a gas, and the fine particles are oriented in the same direction using a magnetic field or an electric field, and then attached to the entire surface of a semiconductor integrated circuit substrate that has completed the wiring process. After that, the resistive film is separated into a plurality of resistive film elements arranged in different directions using a photo-etching method, etc., and the resistance value of the resistive film elements is successively changed stepwise by a fixed ratio, for example, twice. The method is characterized in that an insulating material is formed on the entire surface.

Applied Physics, 1973, 1 states that when a conductive substance such as a metal is evaporated in an inert gas, fine particles with a much larger particle size can be obtained than in the case of normal vacuum evaporation.
As is known from pages 1067 to 1085 of the January issue, the present inventors created a fine particle resistive film with a sufficiently large sheet resistance by attaching the fine particles obtained in this way onto an insulating substrate. It was very successful.

The reason why such a particulate film has a high area resistance is still unresolved, but when the particulates are attached to an insulating substrate, resistance occurs due to the contact between the particulates at the interface.
It is thought that this and the resistance of the fine particles themselves are equivalently connected in series, resulting in a high area resistance as a whole.

It has also been found that the area resistance value of such a microparticle resistance film can be changed by changing the diameter of the microparticles attached. Therefore, the resistance element of the present invention has the advantage that the sheet resistance value can be arbitrarily determined by adjusting the diameter of the particles by some means. Means for changing the diameter of fine particles include changing the evaporation temperature, the type or composition of an inert gas as an atmospheric gas (the heavier the gas, the larger the particle size),
Furthermore, various methods such as changing the gas pressure can be considered, but a particularly effective means is changing the gas pressure of the inert gas.

As an example, the average particle diameter of Linitskel Ni made into fine particles by the in-gas evaporation method using argon gas was observed using a transmission electron microscope. Particle size DO and gas pressure PTOr? The particle size d of the Ni fine particles is 0.
It is recognized that there is a relationship in the range of 8≦P≦20,
It was confirmed that fine particles with a desired particle size could be obtained by appropriately adjusting the gas pressure. Next, a structure of a resistor according to an embodiment of the present invention and an embodiment of its manufacturing method will be described in detail.

In Figure 2, 1 is a P type silicon wafer substrate, 2 is an n
3 and 4 are a transistor part for a D-A converter and a resistor part for a general circuit, respectively formed by well-known semiconductor integrated circuit technology;
5 is an insulator made of a SiO2 film, and 6 is a wiring electrode made of an Al vapor deposited film. After creating the integrated circuit substrate 7 in this way, fine metal particles prepared by the above-mentioned in-gas evaporation method are oriented in a certain direction and attached to the entire upper surface of the substrate to form a resistive film. form. Next, an insulator such as an SiO2 film is formed by CVD or the like, and a plurality of resistive film elements 8a to 8h in a radial pattern as shown in FIG. An insulator 9 such as a SlO2 film is formed by a CVD method or the like. As a result, the fine particle resistive film element 8a is embedded in the layers of the insulators 5 and 9 as shown in the figure.
8b can be formed on the substrate 7. As shown in FIGS. 3 and 4, electrodes 6 are formed on the insulator layer (SiO2 film) 5 while the fine particles created by the gas evaporation method are oriented in a certain direction using a magnetic field or an electric field.
When the resistive film elements 8a to 8h are formed by being deposited in different directions so as to span a portion, the angles of the plurality of resistive film elements 8a to 8h with respect to the applied magnetic field H are different, and as a result, the particle resistance Membrane element 8a~
The relationship between the Ar gas pressure and the electrical resistance value between the electrodes 6 when forming 8h is as shown in FIG. Here, the solid line is the resistance value of the resistive film element 8a, and the broken line is the resistance value of the resistive film element 8h. That is, if an applied magnetic field H is applied for orientation, the electrical resistance value can be adjusted to any value between Ra and Rh depending on the change in angle with respect to the direction. Therefore, if the direction of the resistive film elements 8a to 8h is determined so that the resistance value is changed step by step at a constant ratio, D-A
You can create resistors for converters. For example, for a circuit like that shown in FIG. 1, it is sufficient to set the resistance value to change by a factor of two. It was found that the sheet resistance value of this particulate resistive film was within the range of 10-3 to 107 MΩ/hole. Resistive film element 8a manufactured by such evaporation method in gas
In the ~8h manufacturing process, Ar gas was used as the inert gas, Ni was used as the evaporation material, a tungsten boat with a resistance of about 10 mΩ was used as the heating boat, and a maximum voltage of 2V was used as the heating power source. FIG. 5 shows an example of the actual measurement of the resistance value of a resistive element prepared by opening the shutter and setting the time for forming a fine particle resistive film to adhere fine particles to approximately 150 seconds. Here, the horizontal axis represents the gas pressure of Ar gas sealed in the bell jar when forming the particulate resistance film, and the vertical axis represents the resistance value. As is clear from this characteristic diagram, by adjusting the gas pressure of the inert gas sealed when the evaporation material is evaporated into fine particles, the areal resistance value of each resistor element can be adjusted over a wide range. can be selected.
Also, the area resistance value of this resistance element is approximately 10-3 to 107 MΩ/, depending on the gas pressure.

This makes it possible to obtain a much larger area resistance value than conventional ones, making it possible to greatly contribute to the miniaturization of resistive elements for thin film circuits and other applications. In addition, it is possible to produce products with a small area resistance value, which has the effect of greatly widening the range of application.
In addition to Ni, various conductive substances can be used as evaporation materials to create a fine particle resistance film, and Ar
It goes without saying that any inert gas other than i-s can be used as the atmospheric gas.

In addition, in FIG. 5, A? When the gas pressure is 8T0rr, the resistance value of the resistive film element 8a formed with fine particles oriented perpendicular to the direction of the magnetic field H is the same as that of the resistive film element 8h formed with fine particles oriented parallel to the direction of the magnetic field H. It was confirmed that the resistance value was more than two orders of magnitude larger than that of the previous one.

The magnetic field H at this time was about 2500e. When magnetic fine particles are formed by evaporation in a gas, the fine particles are oriented according to the direction of the magnetic field, and the electrical resistances of the resistive film elements 8a to 8h of the fine particles are aligned with the orientation. It can be adjusted freely depending on the angle. As explained above, according to the present invention, a plurality of resistive film elements whose resistance ratios are successively increased by a constant ratio, for example, twice, can be formed compactly and with high precision on an integrated circuit substrate for a D-A converter. This is extremely useful in practice, as it allows for the uniform manufacture of one-chip D-A converter integrated circuit elements.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a general D-A converter, Fig. 2 is a sectional front view of a resistor for a D-A converter integrated circuit according to an embodiment of the present invention, and Fig. 3 A and B are the same resistor. FIG. 4 is a plan view of the resistor, and FIG. 5 is a characteristic diagram showing the characteristics of the resistor. 5... Insulator, 6... Electrode, 7...
...Semiconductor integrated circuit substrate, 8a to 8h...Resistive film element, 9...Insulator.

Claims (1)

[Scope of Claims] 1. The semiconductor integrated circuit substrate is embedded in an insulating material layer on the upper part of the semiconductor integrated circuit substrate, and is electrically connected to a portion of the wiring electrode of the semiconductor integrated circuit substrate, and is installed in different directions. In addition, it has a plurality of resistive film elements made of fine particles oriented in the same direction, and the resistance value of the plurality of resistive film elements is set to a value that changes step by step at a constant ratio. A resistor for a D-A converter integrated circuit, characterized by: 2. The resistor for a D-A converter integrated circuit according to claim 1, wherein the resistance values of the plurality of resistive film elements change by a factor of two. 3. A resistor for a D-A converter integrated circuit element according to claim 1 or 2, characterized in that a plurality of resistive film elements are arranged radially. 4 Metal fine particles created by evaporation in gas are attached to the entire surface of the substrate after the electrode wiring process of the semiconductor integrated circuit of the D-A converter is oriented in a certain direction by a magnetic field or an electric field to create resistance. A film is created, an insulator is formed on its surface, and then the resistive film is separated into a plurality of resistive film elements arranged in different directions, and the resistance value of the plurality of resistive film elements is determined by 1. A method of manufacturing a resistor for a D-A converter integrated circuit, characterized in that the resistance is set to be changed stepwise at a constant rate, and then an insulator is formed on the entire surface.