JPS61288521A - Electronic device - Google Patents

Abstract

PURPOSE:To improve the specific accuracy of many thin film resistors with good reproducibility and comparatively simple constitution by forming many thin film resistors on a circuit board while gathering them at one position. CONSTITUTION:Many thin film resistors formed on a board 110 are gathered at one position. Thus, the difference in the position of the resistors on the board 110 is small and the change DELTAr in the face resistance rate due to the difference in the position is decreased. That is, the effect of the change in the resistance rate due to the formed position of the thin film resistors is decreased. Further, a ladder resistor 10 is formed while being gathered to one position so as to form a folded part of the ladder resistor 10 at a small round, and the forming condition of the thin resistor R2 at the folded part is made close to that of the thin film resistor R1 at a non-folded part (straight line part) and the improvement of the specific accuracy of the resistance values is attained easily.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to an integrated circuit technology and a technology that is particularly effective when applied to devices in which a large number of thin film resistors are formed. The present invention relates to technology that is effective for use in /D converters or D/A converters.

[Background technology]

For example, in a parallel processing type A/D converter, an analog input voltage is commonly applied to one input of a large number of voltage comparators, while a stepwise different standard is applied to the other input of the large number of voltage comparators. Apply voltage to each. Then, a digital output corresponding to the input voltage is obtained from the comparison output side of each voltage comparator.

In this case, the accuracy of the conversion depends on the relative accuracy of the reference voltages respectively applied to each voltage comparator. This reference voltage is divided using a ladder resistor formed by connecting a large number of resistors in series. Therefore, particularly high specific accuracy is required for the resistors that constitute the ladder resistance.

FIG. 9 shows an example of the configuration of the parallel processing type A/D converter described above.

The A/D converter shown in the figure consists of a ladder resistor 10° comparison circuit array 2. and an encoder 3.

The ladder resistor 10 includes a large number of resistors R1, R1, . . . R1, R3, R1゜... having the same resistance value.
..., R1, R2, R1, ......R1
are connected in series, and both ends thereof are connected to a constant potential reference voltage source Vs and a reference potential (ground potential). From this K, a large number of stepwise different reference voltages are divided from the connection points of the respective resistors constituting the ladder resistor 10. A large number of divided reference voltages are applied to the comparison circuit array 2.

The comparison circuit array 2 is an array of a large number of voltage comparison circuits, and simultaneously compares the analog input voltage vin with the above-mentioned large number of reference voltages.

The encoder 3 converts the comparison output of the comparison circuit array into, for example, 2
Organize into digital data represented by a base code. Dou
t indicates its digital output.

As described above, high-speed A/D conversion operation is performed by parallel processing.

Here, for example, when the above-mentioned A/D converter is formed in a semiconductor integrated circuit device, the ladder resistor 10 is formed by a thin film resistor made of K such as vapor-deposited aluminum. The ladder resistor is formed by forming a large number of thin film resistors connected in series within a semiconductor integrated circuit device.

The ladder resistor 10 is arranged so as to straddle almost the entire surface of the semiconductor substrate, threading between the comparison circuit rows 20 and being folded back.

However, the inventors have discovered that the above-mentioned technique has the following problems.

First, FIG. 10 shows the ladder resistor 10 in a semiconductor substrate (chip) 110 on which the A/D converter is formed.
shows the area where is formed. W indicates the width of the area, and mark indicates the vertical width. As shown in the figure, the ladder resistor 1
0 are dispersed and formed over almost the entire surface of the semiconductor substrate 110.

On the other hand, FIG. 11 shows an example of variations in sheet resistivity of a resistor thin film of aluminum or the like in a semiconductor wafer on which a resistor thin film of aluminum or the like is formed to form the thin film resistor. In the figure, the horizontal axis represents the position in the surface direction of the wafer, and the vertical axis represents the tendency of variation in sheet resistivity.

In addition, Fig. 12 (al and bl respectively shows an example of the distribution state of the sheet resistivity of a resistor thin film in a semiconductor wafer on which a resistor thin film such as aluminum is formed to form the above-mentioned thin film resistor). Indicated by line 101.

As shown in FIGS. 11 and 12, the sheet resistivity of a resistor thin film, such as aluminum, formed on a semiconductor wafer to form the thin film resistor varies depending on the surface position on the wafer.

This variation in sheet resistivity is caused by the non-uniform thickness of the resistor thin film formed by sputtering, for example, but it is extremely difficult to completely eliminate this variation.

For this reason, if an arbitrary part of a semiconductor wafer is cut out by a width W as shown in FIG. It exhibits some kind of variation.

In FIG. 11, Δr indicates the maximum variation in sheet resistivity that occurs within the cut out semiconductor substrate. The state of variation in this case differs depending on the cutting position of the substrate.

In many cases, the sheet resistivity of the resistor thin film simply increases or decreases gradually from one end of the substrate to the other end.

For the reasons described above, even if the thin film resistors formed on each semiconductor substrate have the same planar shape, their resistance values differ slightly depending on their position on the semiconductor substrate. The state of the difference differs depending on the individual semiconductor substrate.

Therefore, if a large number of thin film resistors are formed distributed over a wide area as described above, no matter how accurately the planar shape of each thin film resistor is formed, the change in sheet resistivity depending on the formation position will cause mutual interference. It becomes difficult to increase the ratio accuracy. The present inventors have revealed that this has been one of the major obstacles to improving the conversion accuracy of the above-mentioned parallel processing mA/D converter, for example.

Regarding parallel processing type A/D converters that use ladder resistors, see, for example, "Integrated Circuit Application Handbook 4, Published June 30, 1981, published by Shokusho Shoten, 222, 22.
An overview is provided on page 3.

[Purpose of the invention]

An object of the present invention is to provide a technique that can improve the relative accuracy of a large number of thin film resistors formed on a circuit board with good reproducibility using a relatively simple configuration.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief description of typical inventions disclosed in this application is as follows.

That is, by forming a large number of thin film resistors formed on a circuit board in one place, the influence of changes in resistivity due to the formation position is reduced, and as a result, with a relatively simple configuration, The purpose of this invention is to improve the specific accuracy of a large number of thin film resistors with good reproducibility.

〔Example〕

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

In the drawings, the same reference numerals indicate the same or corresponding parts.

First, FIG. 3 shows an example of the configuration of a parallel processing type A/D converter to which the technology according to the present invention is applied.

The parallel processing type A/D converter shown in the figure is formed within a semiconductor integrated circuit device, and is basically the same as that described above. That is, a large number of voltage comparators CPI~
An analog input voltage V i is applied to each one input (G) of CPn.
n in common, and its many voltage comparators C
Stepwise different reference voltages Vsl to Vsn are applied to the other inputs 1-1 of PI to CPn, respectively. Thereby, a digital output corresponding to the input voltage Vin is obtained from the comparison output side of each voltage comparator CP1 to CPn. In this case, the comparison output of each comparator CPI to CPn is “1”.
” and “On” logic level. Each comparison output is
Logic gate G1~ provided for each comparator CP1~CPn
Gn converts them into alternative selection signals X1 to Xn. The selection signals X1 to Xn are assembled by the encoder 3 into a binary code string of a predetermined number of digits (for example, 8 bits).

Then, this assembled binary code string is the digital output Do
It becomes ut.

FIG. 1 shows a circuit in the main part of the A/D converter shown in FIG. 3 according to its planar arrangement.

As shown in the figure, thin film resistors R1, R1,...
.

The ladder resistor 10 consisting of R2, R1,...
Comparison circuit array 2, 2゜2 divided into multiple blocks
．． In addition to 2, it is formed by shakkake, which are gathered together in one place in the center. And concentratedly formed ladder resistance 10
Comparison circuit rows 2, 2゜2.2 are distributed and arranged on both the left and right sides of the circuit, and each comparison circuit row 2 has a large number of pairs of voltage comparators and logic gates shown in FIG. Many are arranged.

Each thin film resistor R1, R1,... in the ladder resistor 10
The connection points . and each voltage comparison circuit in the comparison circuit array 2 are individually connected by two-layer wiring or the like, as indicated by dotted lines in the figure.

FIG. 2 shows a semiconductor substrate (
In the chip) 110, the area where the ladder resistor 10 is formed is shown, w is the width of the area, and l is the vertical width of the area. As shown in the figure, the ladder resistor 10 is
They are formed in a relatively small group at the center of the semiconductor substrate 110. Especially regarding the width W,
It is much smaller than the one shown in FIG.

In this way, when a large number of thin film resistors formed on the substrate 110 are formed in one place, the difference in the position of the thin film resistors on the substrate 110 becomes smaller, and accordingly,
The amount of change Δr in sheet resistivity due to the difference in position also becomes smaller. In other words, the influence of changes in resistivity due to the formation position of the thin film resistor can be reduced. This makes it possible to improve the relative precision of a large number of thin film resistors with good reproducibility with a relatively simple configuration.

In this case, in the embodiment, the horizontal width W of the region where the ladder resistor 10 is formed is significantly shortened, but the vertical width l thereof is not so shortened. However, as shown in FIG. 1, the direction of the longitudinal width l is the direction in which the rudder resistor 10 travels while turning back. As a result, changes in sheet resistivity in the direction of the longitudinal width l are canceled out by the forward and return paths of the folded ladder resistor 10. In this case, the influence of the change in sheet resistivity due to position appears largely in the direction of the width W, where the effect of canceling it cannot be expected.

Changes in sheet resistivity that appear in the direction of the width W are accumulated by the width W, and this greatly affects the specific accuracy of the ladder resistor 10. Therefore, in the case of this embodiment, the dimension of the width W is The specific accuracy of the ladder resistor 10 can be improved by simply reducing the value of the resistor 10.

Furthermore, as shown in FIG. 1, by forming the ladder resistors 10 in one place, the ladder resistors 10
Both folded parts can be formed with a small turning radius. In other words, it is possible to eliminate the need for large folds. From this K, the shape condition of the thin film resistor R2 in the folded part is defined as the non-folded part (straight part).
It becomes possible to approach that of the thin film resistor R1 in . This also makes it easier to increase the relative accuracy of the resistance value. Figure 4 shows a portion of the A/D converter circuit shown in Figure 1. is shown in detail.

As shown in the figure, the comparison circuit array 2 shown in FIG. 1 includes a large number of comparison circuit units) 2x-1, 2x.

2X+1. It is composed of... Comparison circuit unit) 2x is a high input impedance voltage comparator Cpx,
Latch circuit 211 phase division circuit 22. and a gate buffer 23. The voltage comparator Cpx compares the reference voltage Vsx divided by the ladder resistor 10 and the commonly applied analog input voltage Vin. For example, in the X-th comparison circuit unit 2x, when the input voltage V in becomes higher than the reference voltage Vsx, a logic state of "1" is output from the voltage comparator Cpx. This logic output "1" is held at one end by the latch circuit 21, and then
The phase dividing circuit 22 divides the signal into positive logic "1" and negative logic "0". Then, the positive logic output “1” of the phase division circuit 22 is the upper stage side (x+1st) unit) 2x+
After being subjected to a wired logic (OR) with the inhibit signal EL from 1, it is outputted to the outside via the buffer 23. On the other hand, the negative logic output "0" of the phase division circuit 22 is output to the lower stage (x-1st) unit 2x-1 as the inhibition signal EL.
given to. As a result, one of the comparison circuit units is selected depending on the magnitude of the input voltage Vin, and only the output of the selected comparison circuit unit is activated. For example, the input voltage Via is the reference voltage Vsx of the X-th comparison circuit unit 2x and the X+1st comparison circuit unit)
When it is between the reference voltage Vsx+1 of 2x+1, that is, only the output Xx of Vsx-1 (V i n (when V s x + 1, the Circuit unit...Cp
x-L Cpx+L...output...Xx-1
e Xx+1. ... becomes inactive. Such a comparison circuit unit...Cpx-1゜Cp
x, CI)X+ls'' is used to construct the parallel processing type A/D converter shown in FIG.

5 and 6 show planar pattern shapes of the thin film resistor R1 formed in the non-folded portion of the ladder resistor shown in FIG. 1. FIG.

As shown in FIG. 1, the thin film resistor R1 in the non-folded portion has a large resistance value due to its planar pattern shape.
, is formed in a zigzag shape in which bent portions a and straight portions are alternately connected. At the same time, each corner IA and IB of the pattern is formed at an obtuse angle (approximately 125 degrees).

By forming the corners IA and IB at obtuse angles in this way, as shown in the partially enlarged view of FIG. It becomes difficult to appear in the width direction of R1. That is, the inner corner IA and the outer corner IB
The dimensional variations ΔWA and ΔWB in the width direction can be kept small. As a result, the variation in resistance value in the relevant portion is reduced, and as a result, the specific accuracy of each thin film resistor R1 is
The reproducibility can be further improved without being affected by etching accuracy limits or mask pattern outline blurring.

FIG. 7 shows a planar pattern shape of the thin film resistor R2 formed in the folded portion in the ladder resistor shown in FIG.

As shown in the figure, the thin film resistor R2 formed with a folded partial pressure has a bent planar pattern shape, similar to the resistor R1 of the non-folded part, and the corner of the folded part is formed at an obtuse angle. The thin film resistor R2 in the folded part of this small turn and the thin film resistor R1 in the non-folded part are designed to connect the resistors R1 and R1 lined up on the same side of the two non-folded parts to each other. The bending directions are different from each other. However, their widths and lengths are made the same, so that they have the same resistance value.

Furthermore, the bending direction of the thin film resistor R2 in the folded portion and the thin film resistor R1 in the non-folded portion is partially different, but the folded portion 31 to
The numbers and angles of a8 are the same. In other words, only the shapes of the bent portions themselves are the same. As a result, even if a slight error occurs in the photoetching process, such as in mask positioning, the change in resistance due to the error will be reflected in both the thin film resistor R1 in the non-folded part and the resistor R2 in the folded part. They appear together in the same way. Therefore, the thin film resistor R2 in the folded portion can have a very high relative accuracy or ratio accuracy with respect to the thin film resistor R1 in the non-folded portion without any trimming correction.

FIG. 8 shows an example in which the ladder resistor 10 is applied to a D/A converter.

The D/A converter shown in the figure includes a decoder 4 that converts digital human power Din into alternative selection signals X1 to Xn, and analog switches 81 to Sn that are individually controlled to open and close by the selection signals X1 to Xn. and a ladder resistor 10 which equally divides the reference voltage source Vs and applies it to each end of the analog switch.
and has. The other ends of the analog switches 81 to Sn are commonly connected, and an analog voltage Vout corresponding to the digital human power Din is output from this common connection point. By configuring the ladder resistor 10 as described above, it is possible to obtain a D/A converter with extremely high linear accuracy of conversion characteristics.

As described above, by forming a large number of thin film resistors on a substrate in one place, it is possible to reduce the influence of changes in resistivity due to the formation position. This makes it possible to improve the relative accuracy of a large number of thin film resistors with good reproducibility with a relatively simple configuration. and,
This makes it possible to construct, for example, a highly accurate parallel processing type A/D converter or D/A converter at low cost.

〔effect〕

(1) Compared to forming a large number of thin film resistors on a circuit board in one place, it is possible to reduce the influence of changes in resistivity due to the formation position, and this makes it relatively easy to form. With this configuration, it is possible to obtain the effect that the specific accuracy of a large number of thin film resistors can be improved with good reproducibility.

Although the invention made by the present inventor has been specifically explained based on Examples above, this invention is not limited to the above Examples (although it is possible to make various changes without departing from the gist of the invention). For example, the material of the thin film resistor may be a metal other than aluminum or a semiconductor.Also, the ladder resistor 1o is formed not only in the width W direction but also in one vertical width direction. You may.

[Application field]

As described above, the invention made by the present inventor is applied to parallel processing type A/D converters or D/D converters, which are the field of application behind the invention.
Although the case where the present invention is applied to an A converter has been described, the present invention is not limited thereto, and can also be applied to, for example, a high-precision resistance attenuator. Further, the present invention can be applied not only to semiconductor integrated circuits but also to integrated circuit devices used in hybrid shops, for example.

[Brief explanation of drawings]

FIG. 1 is a diagram showing circuits in the main parts of an A/D converter to which the present invention is applied according to their planar layout, and FIG. 2 is a diagram showing a ladder resistor on a semiconductor substrate on which the A/D converter is formed. 3 is a circuit diagram showing a configuration example of a parallel processing type A/D converter to which the technology according to the present invention is applied; FIG. 4 is a diagram showing the A/D converter shown in FIG. 1. FIG. 5 is a plan view showing the shape of the thin film resistor in the non-folded part; FIG. 6 is a plan view showing an enlarged part of FIG. 5; FIG. is a plan view showing the shape of the thin film resistor in the folded part, Figure 8 is a circuit diagram showing an example of the configuration of a D/A converter using ladder resistors, and Figure 9 is a diagram of a conventional parallel processing type A/D converter. A circuit diagram showing a configuration example. Figure 10 is a diagram showing a region where a ladder resistor is formed on a semiconductor substrate on which a conventional A/D converter is formed. Figure 11 is a resistor for forming a thin film resistor. FIG. 12 (at, (
In a semiconductor wafer on which a resistor thin film for forming a thin film resistor is formed, bl is a section showing an example of the distribution state of the sheet resistivity of the resistor thin film by the contour height ll11IC. DESCRIPTION OF SYMBOLS 1...Resistor, IO...Ladder resistance, R1...Thin film resistor of non-folded part, R2...Thin film resistor of folded part, 2...Comparison circuit array, 110...Semiconductor substrate. Figure 1 Figure 2 Figure Rod 4 Figure 5 Figure 7 Figure 8 Figure 11 Figure 12

Claims (1)

[Claims] 1. An electronic device in which a large number of thin film resistors are formed along with an active circuit on a circuit board, characterized in that the large number of thin film resistors are formed in one place. electronic equipment. 2. The electronic device according to claim 1, wherein the plurality of thin film resistors are connected in series to form a ladder resistor. 3. The electronic device according to claim 1 or 2, wherein the circuit board is a semiconductor substrate. 4. Claim 1, characterized in that the plurality of thin film resistors are connected in series to form a voltage dividing circuit.
The electronic device according to any one of paragraphs to paragraphs 3 to 3. 5. The thin film resistor is formed by etching an aluminum film formed on a circuit board into a predetermined planar shape, according to any one of claims 1 to 4. electronic devices.