JPH0226789B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to ion implantation resistors in semiconductor integrated circuits.

In recent years, semiconductor integrated circuits have become increasingly smaller in circuit current due to problems such as package thermal resistance that accompanies higher integration. One of the conditions required when designing to reduce circuit current is to increase the value of the resistor used in the circuit. Various structures have been proposed for resistors having relatively large resistance values, and recently, ion implanted resistors are often used as this type of resistor.

Conventionally, when it is necessary to accurately determine the relative ratio of resistance values between ion-implanted resistors, there are restrictions on the shapes of these resistors, and they are made in shapes as shown in FIG. 1 or 2. That is, as shown in FIG. 1, the number of corners and the length of the resistance regions 3 in resistors R _{1 and R 2 are} made the same, or as shown in FIG. The idea was to make the shapes exactly the same. In addition, in Figure 1, 3, 6
is a low concentration resistance region formed by ion implantation of acceptor impurities if the part where the resistance is to be formed is N type, 2 and 5 are contact windows for aluminum wiring, and 1 and 4 are ion implanted regions. This is a high concentration boron diffusion region for making contact between 3 and 6 and the aluminum wiring. Further, regions 1 and 4 are formed simultaneously with the base of the NPN transistor, for example.

The reason why the number of corners of the resistances (R ₁ , R ₂ ) is made to be the same in order to improve the relative ratio is that the number of corners of the resistances (R 1 , R 2 ) is made the same due to variations in the layer resistance (hereinafter, layer resistance is referred to as ρ _S ) of the ion implanted regions 3 and 6. This is because the resistance varies greatly. In other words, if the number of corners differs between resistors that take a relative ratio, this variation in resistance at the corner will cause a discrepancy in the relative ratio, so resistors that take a relative ratio must have the same number of corners. It won't happen.

In FIG. 2, 8 and 12 are low concentration resistance regions into which acceptor impurities are ion-implanted, and 9 and 13 are low concentration resistance regions.
In the contact window for Al wiring, 7 and 11 are P-type impurity regions for making contact between the ion implantation regions 8 and 12 and the Al wiring, and 10 and 14 are high concentration boron diffusion regions that connect multiple ion implantation regions. , these regions 10 and 14 together with regions 7 and 11
Formed at the same time as the base of the NPN transistor.
In particular, the resistors R ₁ and R ₂ shown in FIG. 2 have a resistor shape used when the Al wiring for circuit connection and the ion-implanted resistors (R ₁ , R ₂ ) must intersect in terms of layout. In other words, due to the structure, there is a large step in the oxide film above the ion-implanted resistor.
There is a risk of breaking the Al wiring. this is,
In order to eliminate changes in resistance, the ion implantation resistor process is performed last, so the surface
This is because the SiO ₂ film is considerably thicker. Therefore, the low concentration regions are connected by the high concentration regions 10 and 14, and Al wiring is provided thereon.
In this case, the resistors that take the relative ratio are of similar shapes, and the relative ratio is taken by canceling out the difference in resistance value due to the lateral spread of the base after diffusion.

As described above, the conventional ion-implanted resistor for improving the relative ratio cannot be formed into a free resistor shape, which causes problems in mask layout.

Hereinafter, such conventional problems will be explained in more detail using two resistors having different resistance shapes as an example.

First, the resistance value R of the normally shaped ion implanted resistor shown in FIG.
8 and the lateral spread of impurity diffusion in the high concentration region 17 for making contact with the Al wiring, the following equation (1) is obtained.

R=ρ _S・L(1−ΔL/L)/W(1+ΔW/
W)+α...(1) In equation (1), ρ _S is the layer resistance of the ion-implanted resistance region 18, and ΔL and ΔW are the length L of the design value of the resistance region 18 caused by the lateral spread and diffusion of impurities. and deviation from the width W, and α is the resistance at the contact portion with the Al wiring and the high concentration region 17. In this case, this α can be ignored with respect to the resistance value of the ion-implanted resistance region 18, so it is generally deleted. Further, in FIG. 3, 16 is an epitaxial layer in which a resistor is formed, for example in an integrated circuit, and 15 is a separation layer for electrically insulating it from other circuit elements.

Now, two resistors need to have a good relative ratio.
Assuming that R ₁ and R ₂ are formed as shown in Figure 4, the relative ratio of resistance R ₂ /R ₁ between these resistors R ₁ and R ₂ is (1)
Calculate each resistance value using the formula as shown in formula (2).

R ₂ /R ₁ =L-3・△L/L-2・△L……
(2) Here, the resistors R ₁ and R ₂ shown in FIG. 4 are formed similarly to the resistors shown in FIG. 2. That is, the resistor R ₂ is formed by connecting resistance regions 21 having design lengths L ₁ , L ₂ and L ₃ in series with a high concentration layer 19, and forming a high concentration layer 20 as a contact portion at both ends to form a wiring portion. That is. The resistor R ₂ has resistance regions 23 having lengths L ₄ and L ₅ connected in series with a high concentration layer 22, and a high concentration layer 24 of a contact portion at both ends.
This is used as a wiring section. For convenience, the relative ratio is set to 1. That is, the length of the total resistance area 21 of the resistor R ₂ (L ₁ +L ₂ +L ₃ ) and the length of the total resistance area 23 of the resistor R ₁ (L ₄ +L ₅ ) are defined as L, and further the length of the total resistance area 21 of the resistance area 21 and 23 is The widths W and W' are designed to be the same. In addition, changes due to lateral spread and diffusion △
It is assumed that L ₁ , △L ₂ , △L ₃ , △L ₄ and △L ₅ are the same.

As can be seen from equation (2), even if the resistance lengths are designed to be the same in order to accurately obtain the relative ratio, the relative ratio will not be 1 and errors will be 3・△L and 2・△L. .
This means that the total resistance region 21 is divided into two high concentration regions 19
However, since the resistance region 23 is connected by one high concentration region 22, the lateral spread and diffusion of these high concentration regions 19 and 22 gives an error to the resistance length L. be. In other words, with such a shape, an accurate relative ratio cannot be obtained.

From equation (2), a general equation for the relative ratio R _A /R _B between two resistances A and B is derived as shown in equation (3).

R _A /R _B =βL−n′△L/L n△L……(3
) Here, n and n' are the number of ion implanted parts whose ends are the intersection of the ion implanted part and the high concentration region,
Hereinafter, this will be referred to as the number of ion implanted resistors. Also, β is the resistance A
It is a proportionality constant between the resistance length L of the resistor B and the resistance length L of the resistor B. Hereinafter, this will be referred to as the resistance proportionality constant. Equation (3) shows that the relative ratio differs as the number of ion implanted resistors forming the resistance of the ion implanted resistors differs.

From the above, the best relative ratio of ion-implanted resistances is the resistance shape in which the numbers of ion-implanted resistors 26 and 29 are equal and the resistance proportionality constant β is 1, as shown in FIG. This is a high concentration area 25,
From equation (3), the relative ratio shift due to the lateral spread of 28 is
This is because equation (4) holds true. It is assumed that the widths of the ion implantation resistors 26 and 29 are equal.

R ₃ /R ₄ =L-3・△L/L-3・△L=1…
(4) In this way, accurately determining the relative ratio between ion-implanted resistors has been possible only when the two resistors have similar shapes as shown in FIG. This has made it difficult to reduce the size of pellets on the mask layout, posing a major obstacle.

The present invention has been developed to overcome these drawbacks, and its purpose is to provide an ion-implanted resistor that can freely set the shape of the ion-implanted resistor that takes the relative ratio on the mask layout, and that can also take the relative ratio of the resistors with high accuracy. The purpose of the present invention is to provide semiconductor devices.

To explain the basic principle of the present invention in comparison with the conventional technology using drawings, as shown in Fig. 6, the direction of the current flowing through the ion implantation resistor is the "direction", and the voltage drop due to the ion implantation resistor is the "magnitude". Assuming a vector, in the conventional technology, the resistance that takes the relative ratio matches the "size", "number", and "order of direction" of the vector, whereas in the present application, the resistance that takes the relative ratio matches the resistance that takes the relative ratio as shown in Fig. 7. Similarly, the relative ratio is calculated by roughly matching the number of ion-implanted resistors to the resistance ratio, regardless of the "order of direction" of the vectors.

Next, one embodiment of the present invention is shown in FIG. 8 and will be described in detail. The resistor shown in FIG. 8 is obtained by applying the present invention to the resistor shown in FIG. 4, and in this case, the relative ratio is 1. To that end, resistance
A high concentration region 49 is formed at one place in the ion implanted resistance region 23' of _R1 , spanning the resistance region 23',
And the total length of the resistor part of resistor R ₂ (L ₁ ′ + L ₂ ′ + L ₃ ′)
and the total length of resistor R ₁ (L ₄ ′ + L ₅ ′ + L ₆ ′). As shown in Figure 8, high concentration area 4
By overlapping 9 with the resistance area 23', the resistance
The number of substantial ion-implanted resistance parts between R ₁ and R ₂ is the same, so from equation (3), the relative ratio in this case becomes equation (5). It is assumed that the resistance width is the same.

R ₂ /R ₁ =L-3△L/L-3△L=1...
(5) Equation (5) shows that the relative ratio can be obtained with good accuracy regardless of the lateral spread of diffusion.

FIG. 9 shows a second embodiment of the invention. This is because, due to the mask layout, the resistor R8 must have a vertically elongated shape with one resistor region 53 as shown in the figure, and the resistor _R7 is formed by connecting three resistor regions 55 with a high concentration layer 56. and the relative ratio of these
This model aims for R7 = R8/2, and the ratio of the resistance length of resistor R7 on the mask to the resistance length of resistor R8 is set as R8/R7 = 2. For this purpose, high concentration layers 52 are formed at five locations in the resistor _R8 to overlap with the resistor R8. In this case, the relative ratios are β = 2, n' = 6, n = 3 from equation (3).
Therefore, R8/R7=2L−6△L/L−3△L=2……(6
) becomes. From equation (6), it can be seen that the relative ratio of resistors R7 and R8 can be determined with good accuracy.

Furthermore, the present invention is applicable even when the relative ratio of resistances is not an integral multiple. For example, resistor R _A of 10KΩ and 36KΩ
Consider the case of taking the relative ratio of the ion implantation resistance of the resistance R _B of . At this time, if the ion implantation resistance number of resistor R _A is 2, the ion implantation resistance number of resistor R _B is
n' = 3.6 x 2 = 7.2, which is approximately 7 lines. Therefore, from equation (3), R ₂ /R ₁ =3.6-7ΔL/L-2ΔL=3.6(L-1.95ΔL)/L-2ΔL≈3.6. In this way, accuracy will be best if the number of ion-implanted resistors is roughly matched to the resistance value ratio.

The case where this relative ratio of resistances is not an integral multiple will be explained in detail with reference to another example. An example is shown in FIG. 10, where a relative ratio of R10:R9=1:1.75 is required. In this case, in order to facilitate design by setting the ion implantation resistance number as an integer, the least common multiple thereof is taken to be R ₁₀ :R ₉ =4:7. For example, as shown in FIG. 10, the resistor R ₁₀ has two resistance regions 60 and a high concentration region 6.
1 to divide them into two. resistance
_R9 has three resistance regions 63, two of which are divided into three by two high concentration regions 62. Therefore, from equation (3), the relative ratio of these is β=7/
4. Since n'=7 and n=4, R9/R10=7/4L-7・△L/L-4△L=1
.75...(7), and it can be seen from equation (7) that even when the relative ratio of resistance is not an integral multiple, the relative ratio can be obtained with good accuracy.

The embodiment of the present invention shown in FIG. 11 is a case where the relative ratio of the resistances is an integer multiple, and the ion-implanted resistors of the main resistors are connected in parallel, and the relative ratio is determined using the present invention. In other words, a relative ratio of R11:R12=1:2 is required, and R11 is replaced by two ion-implanted resistors 69.
are connected in parallel with high concentration layers 67 and 68. R ₁₂ is formed by one resistive region 66. These resistance regions 66 and 69 have the same shape. Therefore, from equation (1), R ₁₁ = R ₁₂ /2 = ρ _S /2L(1-ΔL/L)/W(
1+ΔW/W), and the relative ratio R12/R11=2, so the relative ratio can be obtained with good accuracy.

In the embodiment shown in FIG. 12, the relative ratio of the resistances is not an integral multiple, but the ion-implanted resistors of the main resistors are connected in parallel and the relative ratio is determined using the present invention. That is, as in the embodiment shown in Fig. 10, the relative ratio is calculated by setting the resistance to the least common multiple, but in the example, R ₁₃ :R ₁₄ =
1:1.75 to R13:R14=4:7, and ion implantation resistors corresponding to the inverse proportion of the resistance ratio are connected in parallel. That is, if R13 connects seven ion-implanted resistors 75 in parallel, and R14 connects four regions 72 in parallel with high concentration layers 70 and 73, _R14 / _R13 = ρ _S (L-ΔL/L /4(W+ΔW/
W)/ρ _S (L-ΔL/L/7(W+ΔW/W)=7/4.

In the embodiment of FIG. 13, the relative ratio of the resistances is an integral multiple, and one of the resistances R ₁₅ is substantially connected in series with three ion-implanted resistances 81 by two high concentration layers 80.
On the other hand, R ₁₆ is an example in which the relative ratio is taken as a series and parallel connection of the resistance region 78 by the high concentration layer 77. From formula (1), R ₁₅ and R ₁₆ are R ₁₅ = 3L-3△L/W+△W R ₁₆ = L-△L/W+△W+L-△L/2 (W+△W)
= 3(L-ΔL)/2(W+ΔW), and an accurate relative ratio can be obtained with these relative ratios R ₁₅ /R ₁₆ =2.

In the embodiment shown in FIG. 14, the relative ratio of the resistances is not an integral multiple, and R17:R18=1.5:1.25. This example also takes the relative ratio by connecting resistors in series and parallel to take the relative ratio.

In this way, by using the present application, the relative ratio of ion implantation resistors can be determined with high precision regardless of the shape by setting the ion implantation resistor according to the resistance ratio, without making the shapes similar. This will be of great help in the future miniaturization of semiconductor integrated circuits.

In the above, an N-type epitaxial layer is formed on a P-type substrate, the ion implantation resistance region is formed by low concentration implantation of P type, for example, boron, and the high concentration region is formed by boron diffusion, which is also the base of an NPN transistor. Although region diffusion is formed at the same time, a P-type epitaxial layer may be formed on an N-type substrate and N-type impurities may be used.

[Brief explanation of drawings]

Figures 1 and 2 are plan views showing two resistors made using conventional technology that require accurate relative ratios, Figure 3 is a plan view of a typical resistor, and Figure 4 is based on conventional technology. Top view showing two resistors, 5th
The figure is a plan view of two resistors with an accurate relative ratio according to the prior art, Figure 6 is a plan view of two resistors showing the basic idea for obtaining an accurate relative ratio according to the prior art, and Figure 7 is a plan view of the book. FIGS. 8 to 14 are plan views of two resistors showing the basic idea of the invention, respectively, showing embodiments of the invention. 1, 4, 7, 10, 11, 14, 17, 19,
20, 22, 24, 25, 27, 28, 30, 1
9, 20, 22, 24, 49, 52, 56, 6
1,62,67,68,70,73,77,80
... P-type high concentration layer, 2, 5, 9, 13 ... Contact window, 3, 6, 8, 12, 18, 21, 23,
26, 29, 53, 55, 60, 63, 66, 7
2, 75, 78, 81...P-type low concentration ion implantation resistance region.

Claims (1)

[Claims] 1 have first and second resistors respectively configured of first and second semiconductor resistor regions having mutually different planar shapes, and the first semiconductor resistor region determines the resistance value of the first resistor. the second semiconductor resistor region interconnects at least two ion implant regions for determining the resistance value of the second resistor; in a semiconductor device including a high impurity concentration region that does not substantially contribute to the resistance value of at least one of the ion implantation region of the first semiconductor resistance region and the ion implantation region of the second semiconductor resistance region. The first and second regions are divided into a plurality of regions by high impurity concentration regions that do not substantially contribute to the resistance value of the
A semiconductor device characterized in that the ratio of the number of ion implanted regions that substantially determines the resistance value of each of the resistors is equal to the resistance ratio of the first and second resistors.