Voltage divider circuit and semiconductor device using the same

Abstract

To provide a voltage divider circuit that achieves both a reduction in change in divided output voltage caused by a change over time in the resistance value of a resistive element and suppression of an increase in the area of the voltage divider circuit.SOLUTION: A voltage divider circuit 100 includes a first terminal 1, a second terminal 2, a voltage-dividing output terminal Q, a first resistor group S1 in which a plurality of resistor elements R1n are connected between the first terminal 1 and the voltage-dividing output terminal Q, a second resistor group S2 in which a plurality of resistor elements R2m are connected between the second terminal 2 and the voltage-dividing output terminal Q, a first metal film 106 connected to the first terminal 1 and covering an area including at least a portion of the first resistor group S1 in a planar view, and a second metal film 107 connected to the second terminal 2 and covering an area including at least a portion of the second resistor group S2 in a planar view, and the second metal film 107 further covers a portion of the first resistor group S1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a voltage dividing circuit and a semiconductor device using the same.

Background Art

[0002] A secondary battery used in a mobile device or the like deteriorates when overcharged or over-discharged. Therefore, a semiconductor device that monitors the battery voltage to protect the battery is often connected between both positive and negative terminals. In such a semiconductor device, a detection accuracy of about 10 mV or less is required, and variations in detection accuracy for each individual semiconductor device may not be negligible.

[0003] As a technique for detecting a predetermined voltage, there is one in which a reference voltage or a voltage to be measured is divided by a voltage dividing circuit and compared, and various voltage dividing circuits have been proposed to improve the detection accuracy.

[0004] In a semiconductor device, a voltage dividing circuit in which a plurality of resistor elements formed of polycrystalline silicon are connected in series may be used. It is known that the resistance value of this polycrystalline silicon resistor element changes according to the hydrogen content.

[0005] In the manufacturing process of a semiconductor device, it is common to use a process containing hydrogen such as a silicon nitride film forming process or an alloying process used for passivation. Therefore, during the manufacturing process of the polycrystalline silicon resistor element, hydrogen may penetrate into the polycrystalline silicon resistor element, and variations may occur in the resistance values of the respective resistor elements.

[0006] In order to suppress the intrusion of this hydrogen, for example, in the invention described in Patent Document 1, by forming a metal film covering the entire plurality of resistor elements, the intrusion of hydrogen into the resistor elements is suppressed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] One aspect of the present invention aims to provide a voltage dividing circuit that achieves both reduction in the change of the voltage dividing output voltage due to the change in the resistance value of the resistance element over time and suppression of the increase in the area of the voltage dividing circuit region.

MEANS FOR SOLVING THE PROBLEMS

[0009] The voltage dividing circuit according to an embodiment of the present invention includes: a first terminal; a second terminal; a voltage dividing output terminal; a first resistor group having a plurality of resistance elements connected between the first terminal and the voltage dividing output terminal; a second resistor group having a plurality of resistance elements connected between the second terminal and the voltage dividing output terminal; a first metal film connected to the first terminal and covering a region including at least a part of the first resistor group in a plan view; a second metal film connected to the second terminal and covering a region including at least a part of the second resistor group in a plan view; and is a voltage dividing circuit comprising: the second metal film further covers a part of the first resistor group.

EFFECTS OF THE INVENTION

[0010] According to one aspect of the present invention, it is possible to provide a voltage dividing circuit that achieves both reduction in the change of the voltage dividing output voltage due to the change in the resistance value of the resistance element over time and suppression of the increase in the area of the voltage dividing circuit region.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0012] The voltage dividing circuit according to an embodiment of the present invention is based on the following findings. The resistance element described in Patent Document 1 can suppress the intrusion of hydrogen to some extent. However, due to the potential difference between the resistance element and the upper metal film, the resistance value may change over time.

[0013] On the other hand, the metal film disposed on the upper layer of the resistance element is divided for each resistance element, and each divided metal film is connected to the respective resistance element covered thereby to reduce the potential difference between the metal film and the resistance element. However, in this configuration, it is necessary to ensure the distance between adjacent metal films, and as the number of divisions of the metal film increases, the area of the non-formed region of the metal film also increases. Therefore, the area of the voltage dividing circuit region where the resistance element and the metal film are formed also increases.

[0014] FIG. 5 is a graph showing the relationship between the change rate of the sheet resistance of the polycrystalline silicon resistance element and the voltage application time.

[0015] The graph shown by the solid line in FIG. 5 represents the characteristics when the potential of the polycrystalline silicon resistor element is higher than that of the upper metal film, and the sheet resistance of the polycrystalline silicon resistor element changes over time in the direction of increasing. The graph shown by the dashed line in FIG. 5 represents the characteristics when the potential of the polycrystalline silicon resistor element is lower than that of the upper metal film, and the sheet resistance of the polycrystalline silicon resistor element changes over time in the direction of decreasing. In either case, the greater the potential difference between the upper metal film and the polycrystalline silicon resistor element, the greater the change in the sheet resistance of the polycrystalline silicon resistor element over time. The inventor has found that such a change becomes remarkable when the potential difference between the metal film and the resistor element is 40 V or more. It is considered that this is due to the polarization of unstable molecules or the like between the resistor element and the insulating film due to the long-term application of the potential.

[0016] Therefore, in a voltage dividing circuit according to an embodiment of the present invention, a first metal film covering a part of a first resistor group is connected to a first terminal, and a part of the first resistor group and a second metal film covering a second resistor group are connected to a second terminal.

[0017] Thereby, this voltage dividing circuit can provide a voltage dividing circuit that achieves both reduction of the change in the voltage dividing output voltage due to the change in the resistance value generated in the resistor element over time and suppression of the increase in the area of the voltage dividing circuit region.

[0018] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[0019] In the drawings, the same reference numerals are given to the same components, and redundant descriptions may be omitted.

[0020] Also, the X-axis, Y-axis, and Z-axis shown in the drawings are assumed to be orthogonal to each other. The Z-axis direction may be referred to as the "height direction" or the "thickness direction". The surface on the +Z direction side of each member may be referred to as the "front surface" or the "upper surface", and the surface on the -Z direction side may be referred to as the "back surface" or the "lower surface". "Plan view" means looking at each member from the +Z direction side toward the -Z direction side.

[0021] Furthermore, the drawings are schematic and do not show the ratios of width, depth, and thickness as indicated. The quantity, position, shape, structure, size, etc. of each member are not limited to those shown in the following embodiments, and can be the preferred quantity, position, shape, structure, size, etc. for implementing the present invention.

[0022] (An example of an embodiment) FIG. 1 is a circuit diagram of a voltage dividing circuit according to an embodiment of the present invention.

[0023] As shown in FIG. 1, the voltage dividing circuit 100 includes a first terminal 1, a second terminal 2, a voltage dividing output terminal Q, a first resistor group S1, a second resistor group S2, a first metal film 106, and a second metal film 107.

[0024] The first resistor group S1 has a plurality of resistor elements R1n (n is a natural number) connected in series. One end of the first resistor group S1 is connected to the first terminal, and the other end is connected to the second resistor group S2. The second resistor group S2 has a plurality of resistor elements R2m (m is a natural number) connected in series. One end of the second resistor group S2 is connected to the other end of the first resistor group S1, and the other end of the second resistor group S2 is connected to the second terminal 2. The connection part of the first resistor group S1 and the second resistor group S2 is connected to the voltage dividing output terminal Q.

[0025] The voltage dividing circuit 100 outputs an output voltage Vout obtained by dividing the potential difference between the first terminal 1 and the second terminal 2 from the voltage dividing output terminal Q according to the ratio of the total resistance value of the first resistor group S1 and the total resistance value of the second resistor group S2. In this embodiment, the first terminal is connected to the VDD terminal of the semiconductor device having the voltage dividing circuit 100. The second terminal is connected to the GND terminal in this embodiment.

[0026] The first metal film 106 is formed on the upper layer of the resistor elements R11 to R1n - 1 of the first resistor group S1. The first metal film 106 is electrically connected to the first terminal 1 by the metal film 108.

[0027] On the upper layer of the resistance elements R1n of the first resistance group S1 and the resistance elements R2m of the second resistance group S2, a second metal film 107 is formed. The second metal film 107 is electrically connected to the second terminal 2 by a metal film 108.

[0028] FIG. 2 is a schematic top view (perspective view) of the voltage dividing circuit shown in FIG. 1.

[0029] Each of the resistance elements R1n and R2m is a polycrystalline silicon resistance element 103 formed of a polycrystalline silicon film. The polycrystalline silicon resistance element 103 is formed with a length L1 and a width W1. Each polycrystalline silicon resistance element 103 has a high resistance portion 103a and a low resistance portion 103b. The low resistance portion 103b of the polycrystalline silicon resistance element 103 is connected to the metal wiring 108 by a contact hole 105 and is connected to the low resistance portion 103b of an adjacent polycrystalline silicon resistance element 103. The low resistance portion 103b is formed at both ends in the length direction of the polycrystalline silicon resistance element 103 with a length L12, and the high resistance portion 103a is formed between the low resistance portions 103b with a length L11. The high resistance portion 103a has its P-type or N-type impurity concentration adjusted to obtain a desired resistance value.

[0030] On the upper layer of the resistance elements R11 to R1n-1 of the first resistance group S1, a first metal film 106 is formed so as to cover the entire high resistance portion 103a of the resistance elements R11 to R1n-1. The first metal film 106 is electrically connected to the first terminal 1 by a metal wiring 108. As a result, the resistance values of the resistance elements R11 to R1n-1 of the first resistance group S1 change over time in a decreasing direction.

[0031] On the upper layer of the resistance element R1n of the first resistance group S1 and the resistance elements R21 to R2m of the second resistance group S2, a second metal film 107 is formed so as to cover the entire high resistance portion 103a. The second metal film 107 is electrically connected to the second terminal 2 by a metal wiring 108. As a result, the resistance values of the resistance elements R21 to R2m of the second resistance group S2 and the resistance element R1n of the first resistance group S1 change over time in an increasing direction.

[0032] At this time, in the resistor element covered by the second metal film 107, the potential difference between the resistor element R1n and the second metal film 107 becomes the largest, and the change over time in the resistance value of the resistor element R1n becomes the largest. Therefore, the resistance value of the entire first resistor group S1 changes over time in the direction of increasing. Thus, since the resistance values of both the entire first resistor group S1 and the entire second resistor group S2 change over time in the direction of increasing, the change in the ratio of the resistance values can be reduced.

[0033] As a result, the voltage dividing circuit 100 can reduce the change in the voltage dividing output voltage due to the change over time in the resistance values generated in the resistor elements R1n and R2m. Also, the metal films covering the upper layers of the resistor elements R1n and R2m can suppress an increase in the area of the voltage dividing circuit region by making the voids of the metal films into one location as the two first metal film 106 and second metal film 107.

[0034] FIG. 3 is a schematic cross-sectional view taken along line III-III shown in FIG. 2. FIG. 4 is a schematic cross-sectional view taken along line IV-IV shown in FIG. 2.

[0035] As shown in FIGS. 3 and 4, this voltage dividing circuit 100 is formed on the upper layer of the field insulating film 102 formed on the surface of the semiconductor substrate 101. Each of the resistor elements R1n and R2m is a polycrystalline silicon resistor element 103 formed of a polycrystalline silicon film.

[0036] An insulating film 104 is formed on the upper layer of the polycrystalline silicon resistor element 103, and a first metal film 106, a second metal film 107, and a metal wiring 108 are formed on the upper layer of the insulating film 104. The low-resistance portion 103b of the polycrystalline silicon resistor element 103 is connected to the metal wiring 108 through a contact hole 105. The first metal film 106, the second metal film 107, and the metal wiring 108 are formed of, for example, a stacked film of Al—Si—Cu, a stacked film of Al—Cu, or the like.

[0037] A second insulating film 109 is formed on the upper layers of the first metal film 106 and the second metal film 107, and a silicon nitride film 110 is formed on the upper layer of the second insulating film 109.

[0038] Here, the first metal film 106 covering the upper layer of the high-resistance portions 103a of the resistance elements R11 to R1n-1 of the first resistance group S1, the second metal film 107 covering the upper layer of the high-resistance portions 103a of the resistance element R1n of the first resistance group S1 and the resistance element R2m of the second resistance group S2, and the metal wiring 108 are formed in the same layer. In this way, by using two metal films, namely the first metal film 106 and the second metal film 107, to make the void of the metal film into one place, an increase in the area of the voltage dividing circuit region can be suppressed.

[0039] (Modification of the Embodiment) FIG. 6 is a schematic top view (perspective view) of a voltage dividing circuit in a modification of the embodiment of the present invention.

[0040] The voltage dividing circuit 200 in the modification of the embodiment of the present invention includes a first resistance group S3 and a second resistance group S4. The first resistance group S3 has a plurality of resistance elements R3n (n is a natural number) connected in series, and the second resistance group S2 has a plurality of resistance elements R4m (m is a natural number) connected in series.

[0041] FIG. 7 is a schematic cross-sectional view taken along line VII-VII shown in FIG. 6. FIG. 8 is a schematic cross-sectional view taken along line VIII-VIII shown in FIG. 6.

[0042] Each resistor element R3n and R4m is a diffusion resistor element 203 formed by an impurity diffusion layer formed on the surface of the semiconductor substrate. The diffusion resistor element 203 is formed by ion-implanting an impurity of a conductivity type different from that of the semiconductor substrate 101. Each diffusion resistor element 203 is separated by an element isolation film 202. The diffusion resistor element 203 is formed with a length L2 and a width W2. Each diffusion resistor element 203 has a high-resistance portion 203a and a low-resistance portion 203b. The low-resistance portion 203b is formed at both ends in the length direction of the diffusion resistor element 203 with a length L22, and the high-resistance portion 203a is formed between the low-resistance portions 203b with a length L21. The impurity concentration of the high-resistance portion 203a is adjusted to have a desired resistance value. The rest is the same as the voltage dividing circuit 100.

[0043] Thereby, the voltage dividing circuit 200 can reduce the change in the voltage dividing output voltage due to the change over time of the resistance values generated in the resistor elements R3n and R4m. Also, the metal film covering the upper layer of the resistor elements R3n and R4m is made into two, the first metal film 106 and the second metal film 107, and by making the voids of the metal film into one place, an increase in the area of the voltage dividing circuit region can be suppressed.

[0044] As described above, the embodiments of the present invention have been explained, but the present invention is not limited to these embodiments, and designs and the like within the scope not departing from the gist of this invention are also included.

[0045] For example, in this embodiment, it is assumed that a plurality of resistor elements R1n (n is a natural number), R2m (m is a natural number), R3n (n is a natural number), and R4m (m is a natural number) of the voltage dividing circuit are connected in series, but all or a part of them may be in parallel. A circuit for adjusting the resistance value, such as a fuse element or a MOS transistor, may be connected to the resistor element. Also, the region covered by the first metal film is set as resistor elements R11 to R1n-1 and R31 to R31n-1, and the region covered by the second metal film is set as resistor elements R1n to R2m and R3n to R4m, but it may be changed to the position of any resistor element in the region of the first resistor group S1.

[0046] In addition, in this embodiment, the semiconductor substrate 101 is used as the lower layer of the resistance elements R1n, R2m, R3n, and R4m, but a well layer may be formed on the surface of the semiconductor substrate 101. The well layer may be formed as one layer under the entire resistance element, or may be formed by dividing it into a plurality of layers.

Explanation of Signs

[0047] 100, 200 Voltage Dividing Circuit 101 Semiconductor Substrate 102 Field Insulating Film 202 Element Isolation Film 103 Polycrystalline Silicon Resistance Element (Resistance Element) 203 Diffusion Resistance Element (Resistance Element) 103a, 203a High Resistance Portion 103b, 203b Low Resistance Portion 104 Insulating Film 105 Contact Hole 106 First Metal Film 107 Second Metal Film 108 Metal Wiring 109 Second Insulating Film 110 Silicon Nitride Film S1, S3 First Resistance Group S2, S4 Second Resistance Group R1n, R2m, R3n, R4m Resistance Elements L1, L2 Length of Resistance Element L11, L21 Length of High Resistance Portion L12, L22 Length of Low Resistance Portion W1, W2 Width of Resistance Element 1 First Terminal 2 Second Terminal Q Voltage Dividing Output Terminal

Claims

1. A first terminal; A second terminal; A voltage divider output terminal, a first resistor group including a plurality of resistor elements connected between the first terminal and the voltage division output terminal; a second resistor group including a plurality of resistor elements connected between the second terminal and the voltage division output terminal; a first metal film connected to the first terminal and covering an area including at least a part of the first resistor group in a plan view; a second metal film connected to the second terminal and covering an area including at least a part of the second resistor group in a plan view; A voltage divider circuit comprising: The voltage divider circuit according to claim 1, wherein the second metal film further covers a portion of the first resistor group.

2. 2. The voltage divider circuit according to claim 1, wherein the first metal film and the second metal film are formed in the same layer.

3. 3. A semiconductor device comprising the voltage divider circuit according to claim 1.

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