JPH0521718A - R-2r ladder resistor device - Google Patents

Abstract

PURPOSE:To provide an R-2R ladder resistor device with which a highly accurate resistance ratio can be easily obtained. CONSTITUTION:On at least one side exterior to an R-2R ladder resistor part 5, at least one other resistor having the same size, the same shape and the same direction as those of resistors 3a, 3b of the R-2R resistor part is provided, as well as another oxide film 4a having the same width of an oxide film 4 is provided between said other resistor and the R-2R ladder resistor part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an R-2 in which a highly accurate R-2R ladder resistor section is formed on a semiconductor integrated circuit device.
It relates to an R ladder resistance device.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are a top view and a sectional view, respectively, showing a conventional R-2R ladder resistance device. In the figure, 1 is a first semiconductor region, 2 is a second semiconductor region formed adjacent to the first semiconductor region 1, and 3a and 3b are a plurality of, for example, five, formed on the first semiconductor region 1. A resistor, such as a second semiconductor diffused resistor, constitutes an R-2R ladder resistor portion 5 together with the oxide film 4 formed between these resistors. The resistors 3a and 3b have the same size, shape and direction, and the oxide film 4 has the same width. 6 is a substrate of a semiconductor integrated circuit device formed under the first semiconductor region 1 and the second semiconductor region 2, and 7 is R
-2R is an oxide film formed outside the ladder resistance portion 5 and on the first semiconductor region 1 and the second semiconductor region 2.

The conventional R-2R ladder resistance device is constructed as described above, and the first semiconductor region 1 formed on the substrate 6 is formed.
The shapes of the upper resistors 3a and 3b are determined by the oxide films 4 and 7. That is, the width of the resistor 3a is determined by the oxide films 4 and 7, and the resistance 3b is determined by the oxide film 4.

[0004]

Since the conventional R-2R ladder resistance device is constructed as described above, the R-2R ladder resistance device is
Depending on where the resistance of the ladder resistor is located, the state of the oxide film that forms the resistor, for example, the width and cross-sectional area are different, so even if the length of the resistor is constant, its width may vary depending on the position. There is a possibility that they may differ, and there is a problem that it is difficult to obtain an accurate resistance ratio.

The present invention has been made in order to solve such a problem, and an object thereof is to obtain an R-2R ladder resistance device which can easily obtain an accurate resistance ratio.

[0006]

R-2R according to the present invention
The ladder resistance device has at least one of the same size, the same shape and the same direction as the resistance of the R-2R resistance part, on the outside of at least one of the R-2R ladder resistance parts.
The other resistance of the book is provided, and the other resistance and the R-
Another oxide film having the same width as that of the oxide film is provided between the 2R ladder resistance portion.

In the R-2R ladder resistance device according to the present invention, of the plurality of resistances of the R-2R ladder resistance section, the resistance closest to the other resistance is made to correspond to the most significant bit of the R-2R ladder resistance section. Of.

[0008]

According to the present invention, each of the plurality of resistors of the R-2R ladder resistor has the same width of the oxide film on both sides thereof, and therefore has the same width, so that the resistance ratio is stable. Turn into. Further, the resistance at the end of the R-2R ladder resistance portion is likely to cause an error, but the resistance at the end described above is not the resistance at the end due to the addition of another resistance, so the error due to the most significant bit is Will be reduced.

[0009]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are a top view and a sectional view, respectively, of an embodiment of the present invention. In the figure 1, 2, 3
a, 3b, 4 to 6 are exactly the same as those in the conventional example. Reference numeral 3c is another resistance provided outside one side of the R-2R ladder resistance portion 5, for example, a second semiconductor diffusion resistance, and has the same size, the same shape and the same direction as the resistances 3a and 3b. ing. 4a is another resistor 3c and R-2R
Another oxide film provided between the ladder resistor 5 and
It has the same width as the oxide film 4. 7a is another resistor 3c
Is formed on the side opposite to the R-2R ladder resistance portion 5 and is an oxide film having a state different from that of the oxide film 4 and the other oxide film 4a, for example.

In this embodiment thus constructed, the other oxide film 4a becomes R due to the presence of the other resistor 3c added to the outside of the R-2R ladder resistor portion 5 on both sides thereof.
The state becomes similar to that of the oxide film 4 in the −2R ladder resistance portion 5. As described above, since the states of the oxide film 4 and the other oxide film 4a come close to the same state, the shapes of the resistors 3a and 3b of the R-2R ladder resistance section 5 are almost the same because they have the same conditions. As a result, the R-2R ladder resistance portion 5 does not come into contact with the oxide film 7a in a different state.
The accuracy of the resistance ratio of the -2R ladder resistance device is improved.

Embodiment 2. In the above embodiment, R-2
In order to improve the accuracy of the resistance ratio of the entire R-2R ladder resistance part of the R ladder resistance device, another resistance is added to both sides of the R-2R ladder resistance part. Other resistors may be added to only one of the two sides depending on the usage content of. For example, in a DA converter using an R-2R ladder resistance device, when converting digital data to analog data, it is known that the upper bit data has a larger error than the lower bit data. Usually, the R-2R ladder resistance section is often arranged in order from the most significant bit to the least significant bit, and therefore, there is often a resistance corresponding to the most significant bit at the end of the R-2R ladder resistance section. As described above, since the resistance at the end of the R-2R resistance portion easily causes an error, the conversion of the upper bit data to the analog data further increases the error. In such a case, if the above-mentioned other resistor is newly added to the outside of the resistor corresponding to the most significant bit, the state of the resistor of the most significant bit, for example, the width is changed to another bit in the R-2R ladder resistor portion. The error is reduced because it approaches the state of the corresponding resistor. In the above embodiment,
Although the present invention has been described as applied to the R-2R ladder resistance device, it goes without saying that it can be applied to other devices that require high resistance ratio accuracy.

[0012]

As described above in detail, according to the present invention, the outside of at least one of the R-2R ladder resistance portions is
At least one other resistor having the same size, the same shape and the same direction as the resistance of the R-2R resistor portion is provided, and between the other resistor and the R-2R ladder resistor portion. Since another oxide film having the same width as that of the oxide film is provided, it is possible to easily obtain an accurate resistance ratio. Further, according to the present invention, among the plurality of resistors of the R-2R ladder resistor portion, the resistor closest to another resistor is the R resistor.
-Since it corresponds to the most significant bit of the 2R ladder resistance part,
This has the effect of reducing the error due to the most significant bit.

[Brief description of drawings]

FIG. 1 is a top view showing an embodiment of the present invention.

2 is a cross-sectional view of the embodiment of FIG.

FIG. 3 is a top view showing a conventional R-2R ladder resistance device.

4 is a cross-sectional view of the conventional device of FIG.

[Explanation of symbols]

1 First semiconductor region 3a, 3b resistance 3c Other resistance 4 oxide film 4a Other oxide film 5 R-2R ladder resistor

Claims (2)

[Claims] 1. A R-2R ladder resistor portion including a first semiconductor region and a plurality of resistors formed on the first semiconductor region and an oxide film between these resistors, the magnitude of the resistor, In an R-2R ladder resistance device having the same shape and direction and the same width of the oxide film, the R
At least one other resistor having the same size, the same shape and the same direction as the resistor is provided outside at least one of the -2R ladder resistor portions, and the other resistor and the R-2R ladder resistor R is characterized in that another oxide film having the same width as that of the oxide film is provided between the R and
-2R ladder resistance device. 2. The R-2R ladder resistor according to claim 1, wherein among the plurality of resistors of the R-2R ladder resistor unit, the resistor closest to the other resistor corresponds to the most significant bit of the R-2R ladder resistor unit. apparatus.