SEMICONDUCTOR INTEGRATED CIRCUIT

A semiconductor integrated circuit includes a first resistor formed on a semiconductor substrate, wherein the first resistor includes a first resistor element and a second resistor element, which are connected in series and have a same resistance value, and wherein a well in which the first resistor element is formed and a well in which the second resistor element is formed are connected to a connection node between the first resistor element and the second resistor element.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority under 35 U.S.C. § 119 to Japanese Application No. 2023-052370, filed on Mar. 28, 2023, the entire contents of which being incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a resistor formed in a semiconductor integrated circuit.

BACKGROUND

One of important components of a semiconductor integrated circuit is a resistor. There are various types of resistors. A poly resistor, a diffused resistor, a metal resistor, or the like is used according to applications thereof.

A resistance value of a resistor formed on a semiconductor substrate changes slightly according to a voltage applied thereto. This is called voltage modulation. The voltage modulation is not a problem in many applications because it is on the order of 0.1% or less at most even when applying a large voltage in excess of 10 V.

DETAILED DESCRIPTION

Summary of Embodiments

A summary of some exemplary embodiments of the present disclosure will be described. This summary is intended to provide a simplified description of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the following detailed description and is not intended to limit the scope of the invention or the disclosure. This summary is not an exhaustive overview of all conceivable embodiments and is not intended to identify key elements of all embodiments or to delineate the scope of any or all embodiments. For the sake of convenience, “one embodiment” may be used to refer to one embodiment (example or modification) or multiple embodiments (examples or modifications) disclosed in this specification.

A semiconductor integrated circuit according to one embodiment includes a resistor formed on a semiconductor substrate. The resistor includes a first resistor element and a second resistor element connected in series and having an equal resistance value. A well in which the first resistor element is formed and a well in which the second resistor element is formed are connected to a connection node between the first resistor element and the second resistor element.

According to this configuration, since one resistor is divided into two resistor elements and a voltage corresponding to a midpoint voltage is applied to the well of each resistor element, it is possible to reduce the influence of voltage modulation.

In one embodiment, the well in which the first resistor element is formed and the well in which the second resistor element is formed may be the same well.

In one embodiment, the well in which the first resistor element is formed and the well in which the second resistor element is formed may be independent wells.

In one embodiment, the first resistor element and the second resistor element may be poly resistors.

In one embodiment, the first resistor element and the second resistor element may be diffused resistors.

In one embodiment, the semiconductor integrated circuit may further include a subtraction amplifier circuit including an operational amplifier. A resistor of the subtraction amplifier circuit may be configured using the resistor of the above configuration.

In one embodiment, the semiconductor integrated circuit may further include a non-inverting amplifier including an operational amplifier. A resistor of the non-inverting amplifier may be configured using the resistor of the above configuration.

In one embodiment, the semiconductor integrated circuit may further include an inverting amplifier including an operational amplifier. A resistor of the inverting amplifier may be configured using the resistor of the above configuration.

Embodiment

Hereinafter, preferred embodiments will be described with reference to the drawings. Identical or equivalent components, members, and processes shown in each drawing are designated by like reference numerals, and redundant explanations thereof will be omitted as appropriate. Further, the embodiments are exemplary rather than limiting the disclosure and the invention. All features and combinations thereof described in the embodiments are not necessarily essential to the disclosure and the invention.

In the present disclosure, “a state where a member A is connected to a member B” includes a case where the member A and the member B are physically and directly connected or even a case where the member A and the member B are indirectly connected via any other member that does not affect an electrical connection state between the members A and B or does not impair functions and effects achieved by combinations of the members A and B.

Similarly, “a state where a member C is installed between a member A and a member B” includes a case where the member A and the member C or the member B and the member C are indirectly connected via any other member that does not affect an electrical connection state between the members A and C or the members B and C or does not impair functions and effects achieved by combinations of the members A and C or the members B and C, in addition to a case where the member A and the member C or the member B and the member C are directly connected.

FIG.1is a cross-sectional view of a semiconductor integrated circuit100including a resistor200according to one embodiment. The resistor200is formed on a semiconductor substrate110. The resistor200has a first end202and a second end204.

A well112is formed in the semiconductor substrate110. The resistor200is formed over the well112. The resistor200is divided into a first resistor element r1and a second resistor element r2connected in series between the first end202and the second end204. Assuming that a design value of a resistance value of the resistor200is r, the first resistor element r1and the second resistor element r2are designed so that respective resistance values thereof are equal to r/2. The first resistor element r1and the second resistor element r2are poly resistors or diffused resistors.

A voltage corresponding to a midpoint voltage between a voltage at the first end202and a voltage at the second end204is applied to the well112. Specifically, the well112is connected to a connection node206between the first resistor element r1and the second resistor element r2.

The above is a configuration of the resistor200. Advantages of the resistor200will become apparent when compared with a comparative technique. Therefore, the comparative technique will be described first.

FIG.2is a cross-sectional view of a semiconductor integrated circuit100R including a resistor200R according to a comparative technique. The resistor200R includes a single resistor element r0, which is formed on a well112and has a resistance value of r. The well112is connected to one of the first end202and the second end204(here, the second end204). The above is a configuration of the resistor200R.

FIG.3is a view showing a result of a simulation on resistance values of the resistor200according to the embodiment and the resistor200R according to the comparative technique.FIGS.4A to4Care circuit diagrams used in the simulation ofFIG.3. The design values of the resistors200and200R are 1 kilo-ohms. In circuit (i), the second end204of the resistor200was grounded, and the first end202was connected to a variable voltage source600(seeFIG.4A). In circuit (ii), the second end204of the resistor200R was grounded, and the first end202was connected to the variable voltage source600(seeFIG.4B). In circuit (iii), the first end202of the resistor200R was grounded, and the second end204was connected to the variable voltage source600(seeFIG.4C). A voltage VDDof the variable voltage source600was swept from 0 V to 10 V, a current flowing through the resistor was measured, and a resistance value was calculated from the voltage and the current.

As shown inFIG.3, in the circuits (ii) and (iii) using the resistor200R according to the comparative technique, the resistance value r changed according to the power supply voltage VDD, and an effect of voltage modulation appeared. On the other hand, in the circuit (i) using the resistor200according to the embodiment, the resistance value r showed a constant value regardless of the power supply voltage VDD, indicating that the effect of voltage modulation can be suppressed.

FIG.5is a cross-sectional view of a semiconductor integrated circuit100aincluding a resistor200aaccording to a modification. In this modification, the first resistor element r1and the second resistor element r2are formed separately on independent wells112_1and112_2, respectively. The wells112_1and112_2are connected to the connection node206between the first resistor element r1and the second resistor element r2. With this configuration also, the effect of voltage modulation can be suppressed as in the resistor200shown inFIG.1. However, since the wells112_1and112_2are independent in this modification, a circuit area is larger than that of the resistor200shown inFIG.1.

Next, an application of the resistor200will be described. The resistor200can be appropriately used in a circuit that requires high accuracy on the order of 0.1%. For example, an appropriate application of the resistor200is an amplifier circuit which is a combination of an operational amplifier and a resistor.

FIG.6is a circuit diagram of an amplifier circuit400according to one embodiment. The amplifier circuit400is a subtraction amplifier including an operational amplifier402and resistors R11to R14. Since R11=R13and R12-R14, a gain of the amplifier circuit400is g=R13/R11. The resistors R11to R14are the resistor200shown inFIG.1.

The amplifier circuit is not limited to the subtraction amplifier but may be a non-inverting amplifier or an inverting amplifier.

Other applications of the resistor200include an A/D converter and a D/A converter. Alternatively, the resistor200may be used in a resistor voltage divider circuit used for voltage detection means such as an under voltage lock out (UVLO) circuit, an over voltage protection (OVP) circuit, or the like.

The following technique is disclosed in this specification.

A semiconductor integrated circuit, comprising a first resistor formed on a semiconductor substrate,wherein the first resistor includes a first resistor element and a second resistor element, which are connected in series and have a same resistance value, andwherein a well in which the first resistor element is formed and a well in which the second resistor element is formed are connected to a connection node between the first resistor element and the second resistor element.

The semiconductor integrated circuit of Item 1, wherein the well in which the first resistor element is formed and the well in which the second resistor element is formed are a same well.

The semiconductor integrated circuit of Item 1, wherein the well in which the first resistor element is formed and the well in which the second resistor element is formed are independent wells.

The semiconductor integrated circuit of any one of Items 1 to 3, wherein the first resistor element and the second resistor element are poly resistors.

The semiconductor integrated circuit of any one of Items 1 to 3, wherein the first resistor element and the second resistor element are diffused resistors.

The semiconductor integrated circuit of any one of Items 1 to 5, further comprising an amplifier circuit including an operational amplifier and a resistor,wherein the resistor of the amplifier circuit is configured using the first resistor.