JPS6256666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pinch resistor for a semiconductor integrated circuit.

Energy saving has been advocated due to the recent global energy crisis. The introduction of semiconductor integrated circuits is a promising solution to this major problem.

For the same reason, the circuit current of semiconductor integrated circuits is decreasing year by year. This includes problems such as package thermal resistance due to the recent trend toward higher integration, but the reduction of operating current using high-resistance elements has become an important issue. Therefore, in the future, in the field of semiconductor integrated circuits, especially linear integrated circuits, there will be a trend toward smaller currents in terms of active elements, such as the active introduction of I ² L, and lower currents by increasing the resistance of resistors, which are passive elements. It goes without saying that there is one thing.

The problem here is high resistance, which requires relative accuracy rather than absolute accuracy. The present invention relates to improving the relative ratio of pinch resistance, which is most used as a high resistance in semiconductor integrated circuits. Note that, hereinafter, the relative accuracy of the resistance will be referred to as a relative ratio.

Before entering into the description of the present application, a general pinch resistor will be briefly explained with reference to FIGS. 1 and 2 for reference. The pinch resistor is the emitter 2 of the transistor.
This utilizes the high resistance of the base area 1 directly below.
A diffusion layer 1 formed at the same time as the diffusion of the P type base region is provided in the N type epitaxial layer on the P type substrate 6, and a diffusion layer 2 formed at the same time as the diffusion of the N ⁺ emitter region is formed in this layer. At the same time, the thickness of the type diffusion layer 1 is reduced, and the N ⁺ type diffusion layer 2 is superimposed on the high concentration portion of the surface of the P type diffusion layer 1, so that this high concentration portion does not contribute to the resistance value. Electrode 3
are led out from both ends of the P-type diffusion layer 1 through the openings in the surface oxide film 4. Note that 1' and 2' are the respective diffusion layers 1 and 2.
This shows the lateral spread of .

Therefore, the layer resistance directly under the N ⁺ diffusion layer 2 is about one order of magnitude larger than the layer resistance of the P type diffusion layer 1 before the formation of the N ⁺ diffusion layer 2, and the layer resistance ρ _S = 1 kΩ/□ ~ 10 kΩ/□. . In addition, the accuracy of the pinch resistance is determined by the nPn formed at the same time.
It is equal to the base width of the transistor, and varies widely because it depends on the hFE of the nPn transistor. This variation width is larger than the base diffusion resistance of a normal nPn transistor.

However, if the load or bleeder resistor of a differential amplifier is configured in a circuit that is determined by the resistance ratio like a normal base diffused resistor, the characteristic fluctuations due to resistance variations will be within the practical range.

Next, we will discuss pinch resistance and base diffused resistance when taking a resistance ratio with high resistance as described above.

In high-resistance design, the base diffused resistor has a low resistance layer resistance ρ _S (ρ _S = 100 Ω/□ ~ 300 Ω/□), so the resistance length becomes very long, and if the resistance width and number of corners are made the same, the diffusion spreads laterally and the contact The influence on the resistance value due to variations and deviations in resistance etc. can be almost ignored, which is an advantage in calculating relative ratios. On the other hand, since the resistance length is long, it occupies a large area on the pellet, which cannot be ignored from the viewpoint of reducing pellet size.

On the other hand, when a pinch resistor is used, the layer resistance ρ _S of the resistor is high (ρ _PINCH = 1k
Ω/□~10kΩ/□), the resistance length becomes shorter and the area occupied on the pellet can be reduced, but because the resistance length is short, the above-mentioned lateral spread of diffusion affects the resistance value.
It was difficult to determine the relative ratio of pinch resistance.

Next, a conventional technique for increasing the resistance ratio accuracy of two pinch resistors will be described.

Figure 3 shows two pinch resistors R1 and R2 formed on one semiconductor substrate in the same diffusion process.
The P-type diffusion layers 12 and 17 are bent three times for the resistor R1 and four times for the resistor R2. The N ⁺ diffusion layers 14 and 19 are different from the P type diffusion layer 12, respectively.
It is formed so as to overlap with the P-type diffusion layer 17 four times. 12', 17', 14', and 19' indicate errors due to lateral expansion of the diffusion layers 12, 17, 14, and 19, respectively. Electrodes 16 and 21 are taken out from both ends of P-type diffusion layers 12 and 17, respectively.

The resistance ratio of the pinch resistors R1 and R2 will be considered next.The simplified formula for the resistance value of the pinch resistor R1 is given by (1)
As shown in Eq. Here, the layer resistance ρ _S of the P-type diffusion layer 12 varies from about 100% to -50% as described above, but is almost constant on the same wafer. Similarly, misalignment and overetching can be considered to be constant on the same wafer.

ρ _PINCH : Layer resistance of P-type diffusion layer ρ _S LL ₁ L ₂ L ₃ : Length of N ⁺ diffusion layer on mask ΔLΔL ₁ ΔL ₂ ΔL ₃ : Lateral spread of N ⁺ diffusion layer after diffusion W: Mask Width of the upper P-type diffusion layer ΔW: Lateral spread of the P-type diffusion layer after diffusion α: Contact resistance of the contact portion and resistance of the P-type diffusion layer that does not overlap with the N ⁺ type diffusion layer (1) Since the second term can generally be ignored compared to the first term,
Equation (1) becomes equation (1)'.

Similarly, equation (2) holds true for pinch resistance R2. To simplify the explanation here, assuming that the resistance width W = W' and the resistance length L ₁ +L ₂ +L ₃ =L ₄ +L ₅ +L ₆ +L ₇ =L, the relative ratio of resistance R ₂ /R ₁ is calculated by formula (3). becomes.

Since the lateral spread of the N ⁺ diffusion layer after diffusion is the same on the same wafer, ΔL = ΔL ₁ = ΔL ₂ = Δ
L ₃ = ΔL ₄ = ΔL ₅ = ΔL ₆ = ΔL ₇ , and equation (3) becomes (4)
The formula becomes

R ₂ /R ₁ =4ΔL+L/3ΔL+L (4) In equation (4), 4ΔL and 3·ΔL are the causes of the error in the relative ratio. That is, even if the resistance lengths L of the pinch resistors R ₂ and R ₁ on the mask are made the same, an error as shown in equation (4) occurs.

Applying equation (4) to the general equation yields equation (5). At this time, the resistance widths are assumed to be equal.

Here, n: Number of overlapping parts between the N ⁺ diffusion layer of resistor R1 and the P-type diffusion layer n': Number of overlapping parts between the N ⁺ diffusion layer and P-type diffusion layer of resistor R2 β: P of resistor R1 The proportionality constant of the length of the type diffusion layer and the length of the P type diffusion layer of the resistance ^R2 , Equation (5), takes a relative ratio. This indicates that the ratio is off.

In order to eliminate such a difference in the relative ratio of the resistance values of the resistors R1 and R2, it is sufficient to make the numbers n and n' in equation (5) equal, and in the example of FIG.
It is sufficient to make the number of bends of the two parts equal. However, if we make the numbers n and n′ equal, then
Only when the resistance values of the resistors R1 and R2 are equal, there is no difference in the relative ratio of resistance values, and it is not possible to eliminate any difference in the resistance ratio.

The present invention eliminates these drawbacks, and aims to allow the base shape of the pinch resistor for which the relative ratio is to be determined on the mask layout to be freely set, and to enable the relative ratio of the resistors to be determined with high accuracy.

That is, according to the present invention, there is provided a plurality of pinch resistors each having a region of another conductivity type superimposed on a region of one conductivity type, and the resistance ratio of the plurality of pinch resistors and the respective pinch resistors are used to form a region of one conductivity type. A semiconductor integrated circuit device is obtained in which the ratio of the number of overlapping regions of other conductivity types is approximately equal.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 4 is a plan view showing an embodiment of the present invention, for example, two pinch resistors R are provided in an N-type epitaxial layer.
3 and R4 are formed. The pinch resistor R3 has a P-type diffusion layer 50 formed in the same diffusion process as the P-type base region, and an N ⁺ diffusion layer 51 overlapping with this in the surface portion. The P-type diffusion layer 50 is bent into a U-shape and has electrode extraction portions 52 at both ends. The N ⁺ diffusion layer 51 is formed in the same diffusion process as the N ⁺ type emitter region, and is formed in a U-shape so as to overlap the P type diffusion layer 50 three times. The pinch resistor R4 also has a P type diffusion layer 53 formed in the same diffusion process as the P type base region, and an N ⁺ diffusion layer 54 formed in the same diffusion process as the N ^{+ type} emitter region ^. The layer 54 is arranged to overlap the surface portion of the P-type diffusion layer 53. P-type diffusion layer 5
3 is bent twice and ends up overlapping with the N ⁺ diffusion layer 54 three times. The P-type diffusion layer 53 has electrode lead-out portions 55 at both ends.

That is, in the embodiment of FIG. 4 in which the resistance ratio of the pinch resistances R3 and R4 is "1", the P-type diffusion layer 5
Regardless of the shape of 0, 53, the P-type diffusion layer 50 and
The number of overlapping portions with the N ⁺ diffusion layer 51 and the number of overlapping portions between the P type diffusion layer 53 and the N ⁺ diffusion layer 54 are made equal.

Next, the resistance ratio between the pinch resistors R3 and R4 will be explained. To simplify the explanation, coordinates are set for the N ⁺ diffusion layers 51 and 54 that form the pinch resistance,
P-type diffusion layers 50, 5 directly below N ⁺ diffusion layers 51, 54
3, the direction of the current flowing through the resistors is "direction", and the N ⁺ diffusion layers 51 and 54 of each pinch resistor are the P type diffusion layers 50 and 53.
Assume a vector whose "magnitude" is the voltage drop of the P-type diffusion layers 50 and 53 at the overlapped portion with .

In this application, the resistors R3 and R4 that take the relative ratio are the fourth
As the vectors are indicated by arrows in the figure, the number of N ⁺ diffusions is proportional to the ratio β of the lengths of the P-type diffusion layers 50 and 53 of the resistor, which takes the relative ratio of the number of vectors regardless of the order of the direction of the vectors. providing a slit in the layer 51;
Errors in the relative ratio due to the lateral spread of the N ⁺ diffusion layers 51 and 54 are removed. This situation will be explained with reference to FIG.

The pinch resistances R3' and R4' in FIG. 5 are different from the pinch resistances R3 and R4 in FIG.
Although the number of overlapping parts between 0 and 53 and the N ⁺ diffusion layers 51 and 54 is increased by one, this does not affect the following explanation.

Further, 50', 51', 53', and 54' indicate the lateral spread due to manufacturing errors of the diffusion layers 50, 51, 53, and 54, respectively.

Here, if we take the relative ratio of the pinch resistance R3' and the pinch resistance R4', we can see that the N ⁺ diffusion layers 51, 5 on the mask
The length of the portion where 4 overlaps with the P-type diffusion layers 50 and 53 is L=L ₁ ′+L ₂ ′+L ₃ ′+L ₈ =L ₄ ′+L ₅ ′+L ₆ ′+
L ₇ ', N ⁺ diffusion layers 51, 54 and P type diffusion layer 5
Since the number of overlapping parts with 0 and 53 is n=n'=4, the relative ratio is R ₆ /R ₅ = 4ΔL+L from equation (5).
/4ΔL+L=1, and a constant and accurate relative ratio can be obtained regardless of the lateral spread of diffusion. It is assumed that the widths of the P-type diffusion layers 51 and 54 are equal (W=W').

Another embodiment of the invention is shown in FIG.

In this embodiment, the resistance value of the pinch resistor R5 is set to twice the resistance value of the pinch resistor R6, and the pinch resistors R5 and R6 are each formed in an N-type epitaxial layer. The pinch resistor R5 has a linear P-type diffusion layer 38 and a comb-shaped N ⁺ diffusion layer 39 that overlaps six times on the surface of the P-type diffusion layer 38.
Electrode extraction portions 40 are provided at both ends of the P-type diffusion layer 38. On the other hand, the pinch resistor R6 is a P that is bent twice.
It has a type diffusion layer 41 and overlaps with this at the surface part.
The N ⁺ diffusion layer 42 is overlapped at three locations. The P-type diffusion layer 41 has electrode lead-out portions 43 at both ends.

That is, in this embodiment, the pinch resistor R5 must have a vertically elongated shape and the pinch resistor R6 must have a square shape due to the mask layout, and in particular, the ratio of these resistances is set to 1: 2, P-type diffusion layers 38, 4 are formed on the mask.
It is assumed that the length ratio of 1 is set to 1:2.

In this case, if the resistance values of resistors R5 and R6 are R5 and R6, respectively, their relative ratio is R ₅ /R ₆ =n'ΔL+βL/nΔL+L=6ΔL+2 from equation (5).
L/3ΔL+L=2 It can be seen that the relative ratio can be obtained with good accuracy in this example as well.

In this way, according to the present application, the relative ratio of the pinch resistance is determined by equation (5), n′=nβ, without making the shapes similar.
By providing slits in the N ⁺ diffusion layers 51 and 39 so that β is a proportionality constant of the lengths of the P-type diffusion layers of the two resistors, it is possible to set them to any shape and to obtain a relative ratio with high accuracy. Therefore, it will be of great help in the future miniaturization of circuit current in semiconductor integrated circuits.

The spacing between the slits in the N ⁺ diffusion layers 51 and 39 can be freely set as long as the slits do not fit together due to the lateral expansion of the diffusion region.

The above has explained the pinch resistance in which an N ⁺ type diffusion layer is formed in the P type resistance, but this application also describes the
It is also applied to a pinch resistor formed by forming a P ⁺ type diffusion layer on a type resistor.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a general pinch resistor, and FIG. 2 is a plan view thereof. FIG. 3 is a plan view showing a conventional technique in which two pinch resistors are formed. FIG. 4 is a plan view showing an embodiment of the present invention. FIG. 5 is a plan view for explaining the effects of one embodiment of the present invention. FIG. 6 is a plan view showing another embodiment of the present invention. 1, 12, 17, 38, 41, 50, 53...
P-type diffusion layer, 2, 14, 19, 39, 42, 5
1,54...N ⁺ type diffusion layer, 3...electrode, 4...
Surface oxide film, 5... N-type epitaxial layer, 6...
...P type substrate, 16, 21, 40, 43, 52, 5
5... Electrode extraction part.

Claims (1)

[Claims] 1. In a semiconductor integrated circuit device having first and second resistance elements having a predetermined resistance ratio, the first resistance element selectively overlaps a first region of one conductivity type and the first region. and a second region of an opposite conductivity type, and the second resistive element has a second region of an opposite conductivity type.
the third region of one conductivity type formed to have a shape different from that of the region; and the fourth region of the opposite conductivity type selectively overlapping with the third region, and the resistance ratio is equal to the ratio of the number of times the second region overlaps with the first region and the number of times the fourth region overlaps with the third region.