JPH0587961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technology that is particularly effective when applied to thin film resistor technology and ladder resistors, such as A/D converters or D/D converters that are implemented as semiconductor integrated circuit devices. The present invention relates to technology that is effective for use in 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 make up the ladder resistor.

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 includes a ladder resistor 10,
It is composed of a comparison circuit array 2, an encoder 3, and the like.

The ladder resistor 10 includes a large number of resistors R1, R1,...R1, R3, R1,...R1, which have the same resistance value.
R2, R1,...R1 are connected in series,
Both ends thereof are connected to a constant potential reference voltage source, Vs, and a reference potential (ground potential). As a result, 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 arrangement 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 organizes the comparison output of the comparison circuit array into digital data represented by, for example, a binary code. Dout indicates its digital output.

As described above, high-speed A/
A D conversion operation is now being performed.

For example, when the above-described A/D converter is formed in a semiconductor integrated circuit device, the ladder resistor 10 is formed of a thin film resistor made of, for example, vapor-deposited aluminum. The ladder resistor 10 is formed by forming a large number of thin film resistors in series within a semiconductor integrated circuit device. In this case, it is desirable that each thin film resistor be formed in the same planar shape to ensure its relative accuracy.

However, in order to form a ladder resistor consisting of a large number of thin film resistors connected in series, for example, on a limited layout surface within a semiconductor integrated circuit device, as shown in the figure, the ladder resistor 10 must be placed in the middle. have to turn around. Therefore, the planar shape of the thin film resistors R3 and R2 in the folded portions must be different from that of the thin film resistor R1 in the other non-folded portions. Therefore, the resistors R3 and R2 of the folded portion must be formed so that their resistance values are the same as those of the other non-folded portions, even if they have different planar shapes.

However, for thin film resistors having different planar shapes, for example, the effects of errors in the manufacturing stage appear differently depending on the shape of the thin film resistor. For this reason, even if it is possible to make the resistance values of thin film resistors with different planar shapes match each other in calculations at the design stage, the actual result will differ depending on the planar shape. They end up having different resistance values. In particular, since the planar shape of the thin film resistor in the folded part of the large circuit has a large difference, it is almost impossible to match the resistance value with high accuracy from the beginning to that of the thin film resistor in the other non-folded part. It's impossible.
For this reason, in the past, at least the thin film resistor in the folded portion had to be trimmed and corrected using a laser or the like.

Regarding parallel processing type A/D converters that use ladder resistors, an overview is given, for example, in "Integrated Circuit Application Handbook" published by Asakura Shoten, June 30, 1981, pages 222 and 223. ing.

[Purpose of the invention]

An object of the present invention is to make it possible to improve the ratio accuracy between the thin film resistance in the folded part and the thin film resistance in the non-folded part of a folded ladder resistor with good reproducibility by only making a relatively simple change in the configuration. The aim is to provide the technology that

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.

In other words, in a folded ladder resistor, by forming the thin film resistance at the folded portion and the thin film resistance at the non-folded portion to be the same only in the planar shape of each folded portion, the thin film resistance is The objective is to improve the ratio accuracy between the thin film resistance in the folded part and the thin film resistance in the non-folded part of a folded ladder resistor with good reproducibility even with a simple configuration that only changes the pattern shape. The goal is to achieve the following.

〔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. 5 shows an embodiment 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, the analog input voltage Vin is commonly applied to one input (+) of each of the many voltage comparators CP1 to CPn, and
Stepwise different reference voltages Vs1 to Vsn are applied to the other inputs (-) of the large number of voltage comparators CP1 to CPn, respectively. This allows each voltage comparator CP1
A digital output corresponding to the input voltage Vin is obtained from the comparison output side of ~CPn. In this case, each comparator
The comparison outputs of CP1 to CPn are “1” and “0” respectively.
is output at the logic level of Each comparison output is a logic gate G1 to Gn provided for each comparator CP1 to CPn.
are converted into alternative selection signals X1 to Xn. The selection signals X1 to Xn are assembled into a binary code string of a predetermined number of digits (for example, 8 bits) by the encoder 3, and this assembled binary code string becomes the digital output Dout.

FIG. 6 shows the circuit of the A/D converter shown in FIG. 5 in correspondence with its planar arrangement.

The A/D converter shown in the same figure is similar in circuit to that shown in FIG. is formed. In each comparison circuit array 2, a large number of pairs of voltage comparators and logic gates shown in FIG. 5 are arranged. The ladder resistor 10 is connected to each comparison circuit row 2, 2, 2.
It is folded back to sew between the two. One end thereof is connected to a reference voltage source Vs, and the other end is connected to ground potential. The logic outputs from the comparison circuit arrays 2, 2, 2 are input to the encoder 3 after being subjected to preliminary encoding processing using wired logic for each block. The encoder 3 outputs a digital output Dout in the form of a binary code string.

FIG. 7 shows in detail a portion of the circuit of the A/D converter shown in FIG.

As shown in the figure, the comparison circuit array 2 shown in FIG.
It is composed of +1,... Comparison circuit unit
2x has a voltage comparator Cpx, a latch circuit 21, a phase divider 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, the input voltage Vin
is higher than the reference voltage Vsx, the voltage comparator
A logic state of “1” is output from Cpx. This logic output "1" is held at one end by the latch circuit 21, and then divided into a positive logic "1" and a negative logic "0" by the phase division circuit 22. Then, the positive logic output “1” of the phase dividing circuit 22 is applied to the upper stage side (x+
After being subjected to a wired logic (OR) with the inhibit signal EL from the first unit 2x+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 the prohibition signal.
Lower side (x-1st) unit 2x- as EL
given to 1. 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, if the input voltage Vin is x
Reference voltage Vsx and x+ of the th comparator circuit unit 2x
Reference voltage Vsx of the first comparator circuit unit 2x+1
When it is between +1, that is, Vsx−1<Vin<
When Vsx+1, only the output Xx of the x-th comparison circuit unit 2x is activated, and the outputs of the other comparison circuit units...Cpx-1, Cpx+1,...
1, Xx+1, becomes inactive. Such a comparison circuit unit...Cpx-1, Cpx, Cpx+1,
..., the parallel processing type A/
A D converter is configured.

Here, as shown in FIG. 6, the ladder resistor 10 straddles a linear portion along the side of the comparison circuit row 2, a small folded portion folded back to back, and an end portion of the comparison circuit row 2. There is a large turning part. A large number of thin film resistors R1 having a planar pattern shape as shown in FIG. 2 are connected in series in the linear portion, that is, the non-folded portion.
A thin film resistor R2 having a planar pattern shape as shown in FIG. 4 is arranged in the folded portion of the small turn. A thin film resistor R3 having a planar pattern shape as shown in FIG. 1 is arranged in the large turning portion. Thin film resistance R1, R2, R3 of each part
Both are formed by photoetching a metal resistor 1 made of aluminum or the like into a semiconductor integrated circuit device.

FIGS. 2 and 3 show the planar pattern shape of the thin film resistor R1 formed in the non-folded portion.

As shown in the figure, the thin film resistor in the non-folded part
The plane pattern of R1 is formed in a zigzag shape in which bent portions a and straight portions b are alternately connected in order to obtain a large resistance value. At the same time, each corner 1A, 1B of the pattern is formed at an obtuse angle (approximately 125 degrees).

By forming each of the corners 1A and 1B at an obtuse angle in this way, as shown in the partially enlarged view of Fig.
It is becoming harder to appear in the width direction of R1. In other words,
Dimensional variations ΔWA and ΔWB in the width direction at the inner corner portion 1A and the outer corner portion 1B can be kept small. As a result, the variation in resistance value in the relevant portion is reduced, and as a result, the relative accuracy of each thin film resistor R1 can be reproduced without being affected by etching accuracy limits or mask pattern outline blurring. I'm starting to be able to improve my sexuality.

FIG. 4 shows the planar pattern shape of the thin film resistor R2 formed in the folded portion of the small turn.

As shown in the figure, the thin film resistor R2 formed in the folded part of the small turn has a bent planar pattern shape, similar to the resistance in the non-bent part, and the corners of the folded part are obtuse angles. is formed. The thin film resistor R2 in the folded part of this small turn and the thin film resistor R1 in the non-folded part have their bending directions different from each other in order to connect the resistors R1 and R1 lined up on the same side of the two non-folded parts to each other. It's on. However, their width and length are the same as each other,
This allows them to have the same resistance value. Furthermore, the bending directions of the thin film resistor R2 in the folded part of the small turn and the thin film resistor R1 in the non-folded part are partially different, but the number and angle of the folded parts a1 to a8 are the same. It is being In other words, only the shape of the bent portion itself is the same. As a result, process errors in photoetching,
For example, even if a slight error occurs in mask alignment, the change in resistance value due to the error will appear in the same way in both the thin film resistor R1 in the non-folded portion and the resistor R2 in the folded portion. Therefore,
The thin film resistor R2 in the folded part can have very high relative accuracy or ratio accuracy with respect to the thin film resistor R1 in the non-folded part without any trimming correction.

FIG. 1 shows the planar pattern shape of the thin film resistor R3 formed in the folded portion of the large turn.

As shown in the figure, the thin film resistor R3 formed in the large folded portion has a bent portion a having the same shape as the bent portion a in the non-folded portion of the thin film resistor R1, and Partial resistance value and its bent part a
The planar shape is formed such that the sum of the partial resistance values at other locations becomes a predetermined value.

In this case, the thin film resistor R3 of the folded part is formed by connecting resistor parts R31, R31, which have the same bent shape as the thin film resistor R1 of the folded part, and resistors R1, R1 lined up at the same side ends of the two non-folded parts to each other. Rectangular resistor section formed for connection
It is formed by R32.

The resistance portion R31 has a bent portion a and a straight portion b2, similar to the thin film resistor R1 in the non-folded portion. The planar shape at the bent portion a is the same as that at the bent portion a of the thin film resistor R1 in the non-folded portion. At the same time, the total number of bent portions a formed by the two resistance portions R31 and R31 in the resistance R3 is:
As is clear from FIG. 1, the number of folded portions a is equal to the number of bent portions a in the thin film resistor R1 in the non-folded portion. This creates two resistor sections.
The total resistance error caused by the dimensional error during processing at the plurality of bent portions a of R31 and R31 is the same as in the case of the above-mentioned Figures 2, 3, and 4. This corresponds with high accuracy to the sum total of similar resistance errors at the plurality of bent portions a of the thin film resistor R1.

On the other hand, the length L of the resistor portion R32 is determined to be a size necessary to straddle the end of the comparison circuit array (FIG. 6). At the same time, a large width is ensured so that the resistance value Δr is sufficiently small.

Here, the length L2 of the straight part b2 of the resistance part R31 is
Straight line part b1 of thin film resistor R1 in non-folded part
The length is set slightly shorter than the length L1. The difference ΔL is set to a value equivalent to producing the same resistance value (Δr) as the resistance value Δr of the resistance portion R32.

That is, as mentioned above, the two resistive parts
Since the bent part a in R31 and R31 is made to correspond to the bent part a of the thin film resistor R1 in the non-folded part, the resistor R3 has a shape similar to that shown in FIG. In correspondence to the four straight line portions b1, only five portions in total can be set, including the four straight line portions b2 in the two resistance portions R31 and R31, and the resistance portion R32. From this, it becomes necessary for the resistor R3 to form a resistance component equal to the resistance component in the four straight parts b1 with the four straight parts b2 and the resistance part R32. Therefore, as described above, the difference between 4.L1 and 4.L2, that is, the difference .DELTA.L, is set according to the resistance value .DELTA.r of the resistance portion R32. As a result, the thin film resistance R3 at the turning part of the large turn is
The resistance value of the thin film resistor R1 in the non-folded part is
can be made equal to the resistance value of Although the two resistors R1 and R3 have partially different planar shapes and dimensions, their shapes at the bent portion a are the same, so errors in the photo etching process, such as mask alignment, etc. Even if a slight error occurs in , the change in resistance value due to the error will appear in the same way in both the thin film resistor R1 in the non-folded portion and the resistor R3 in the large folded portion. Note that the resistance portion R32 is made longer and wider according to the large turning portion, so the relative dimensional variation due to the dimensional variation of the corner portion is sufficiently small, and therefore, as shown in Fig. 1,
Its corners are left square. Therefore, the thin film resistor R3 in the large folded portion can have 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 has a digital input Din
a decoder 4 that converts the voltage into alternative selection signals X1 to Xn, analog switches S1 to Sn that are individually controlled to open and close by the selection signals X1 to Xn, and analog switches S1 to Sn that equally divide the reference voltage Vs. and a ladder resistor 10 applied to each end. The other ends of analog switches S1 to Sn are commonly connected,
An analog voltage Vout corresponding to the digital input 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, even with a simple configuration that only changes the pattern shape of the thin film resistor, it is possible to reproduce the relative accuracy of each resistance value of the thin film resistor in the folded part and the thin film resistor in the non-folded part of the folded ladder resistor. You will be able to improve it well. 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) In a folded ladder resistor, by forming the thin film resistor in the folded part and the thin film resistance in the non-folded part to be the same only in the planar shape of each folded part, the thin film resistor can be Even with a simple configuration that only requires changing the pattern shape, it is possible to improve the ratio accuracy between the thin film resistance in the folded part and the thin film resistance in the non-folded part of the folded ladder resistor with good reproducibility. This effect can be obtained.

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, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say. For example, the material of the thin film resistor may be a metal other than aluminum or a semiconductor.

[Application field]

Although the invention made by the present inventor is applied to the parallel processing type A/D converter or D/A converter, which is the background field of application, the present invention is not limited to this. It can also be applied to, for example, a high-precision resistor attenuator.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the large folded portion of the ladder resistor according to the present invention, FIG. 2 is a plan view showing the shape of the thin film resistor in the non-folded portion, and FIG.
The figure is a plan view showing an enlarged part of Fig. 2, Fig. 4 is a plan view showing the turning part of the small turn, and Fig. 5 is an A/
A circuit diagram showing an example of the configuration of a D converter, FIG. 6 is a circuit diagram showing the A/D converter in FIG. 5 according to its layout, and FIG. 7 is a circuit diagram showing an example of the A/D converter in FIG. 8 is a circuit diagram showing an example of the configuration of a D/A converter using ladder resistors, and FIG. 9 is a circuit diagram showing an example of the configuration of a parallel processing type A/D converter. It is a diagram. 1...Resistor, 10...Ladder resistance, R1...
Thin film resistance of the non-folding part, R2...Thin film resistance of the small turning part, R3...Resistance of the large turning part, a...Bending part, b, b1,
b2……straight line part.

Claims (1)

[Scope of Claims] 1. An electronic device comprising a ladder resistor formed by serially connecting a plurality of thin film resistors having the same resistance value, wherein the ladder resistor is bent into a zig-sag first planar shape. It consists of a non-folded part consisting of a series connection of a plurality of formed thin film resistors, and a folded part made of a second planar thin film resistor provided in the middle of the non-folded part, and each of the non-folded parts The thin film resistor has a zigzag planar shape in which bent portions and first straight portions are alternately connected, and the thin film resistor in the folded portion has the same shape as the bent portion in the thin film resistor in the non-folded portion. a bent portion, a second straight portion having the same width as the first straight portion and a relatively short length and alternately connected to the bent portion, and a second straight portion having a relatively long length and wide width. and a third linear part for folding, and the number of folded parts thereof is the same as the number of folded parts in the thin film resistor of the non-folded part, and the partial resistance of the second and third linear parts An electronic device characterized in that the length of the second linear section and the length and width of the third linear section are set such that the sum of the partial resistances of the first linear section is equal to the sum of the partial resistances of the first linear section.