JPH04219970A - Adjusting method of resistance value of resistance element - Google Patents

Abstract

PURPOSE:To change the impurity concentration of a diffusion layer or a semiconductor layer which constitutes a resistance element and to adjust the resistance value of the resistance element by a method wherein the resistance element is doped with impurities by using a focused ion beam. CONSTITUTION:When one out of two diffusion resistance elements R1 (5a), R2 (5b), e.g. R1, is too large in order to set the ratio of R1 to R2 to a prescribed ratio, it is required to lower the resistance value of the diffusion resistance element R1 (5a). For this purpose, P-type impurities, e.g. boron B, are doped by using a focused ion beam(FIB). The length of the diffusion resistance elements 5a, 5b is, e.g. at 15mum, their width is, e.g. at 5mum, their depth is, e.g. at 0.3mum and the interval between both is, e.g. at 10mum. In this case, the focused ion beam whose beam diameter is smaller than 5mum e.g. about 1 to 3mum, is used and scanned on the surface part of the diffusion resistance element 5a. The impurities in proper quantities are doped down to a half (0.15mum) of a function depth (0.3mum in this case).

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a method for adjusting the resistance value of a resistive element, and more particularly to a resistive element constructed of a semiconductor of a semiconductor integrated circuit (hereinafter referred to as "IC"), for example, a diffusion resistance value formed on the surface of a semiconductor substrate. The present invention relates to a method for adjusting the resistance value of a resistance element, which adjusts the resistance value of a resistance element or a semiconductor layer resistance element made of polycrystalline silicon or the like formed on a semiconductor substrate via an insulating film.

0002

2. Description of the Related Art A diffused resistor formed on the surface of a semiconductor substrate is often used as a resistor in an IC. In particular, a plurality of diffused resistors are often used with their resistance values set at a predetermined ratio. Figures 3 (A) and 3 (B) show one conventional example of such a composite diffused resistor, where (A) is a plan view and (B) is a cross-sectional view taken along line BB in (A). It is.

In the drawings, 1 is a p-type semiconductor substrate, 2 is an n-type well, 3 is an n+-type buried layer, 4 is an n+-type plug-in region, and 5 (5a, 5b) is a p-type diffusion. The resistance elements (R1, R2), 6, 6 are p+ type contact regions formed at both ends of the diffused resistor 5, 7 is an insulating film on the surface of the semiconductor substrate 1, and 8, 8 is the contact region 6 made of aluminum, for example. , 6 are electrodes made of aluminum, for example.

FIG. 3B shows one diffused resistance element R1.
Although only (5a) appears, as shown in (A), two diffused resistance elements R1 and R2 (5b) are provided in one well 2 so as to have a predetermined ratio of resistance values.

[0005]

[Problems to be Solved by the Invention] By the way, the diffusion resistance element R1 (5
a) and R2 (5b), the ratio of resistance values often deviated from the desired value due to variations in impurity concentration and variations in dimensions such as the length, width, and depth of the diffusion layer. IC
A ratio of a few percent is undesirable in terms of circuit characteristics, but in the past, once a diffused resistance element has been manufactured, it is impossible to adjust the ratio, and this is a factor that prevents improvements in circuit characteristics. was. Further, as shown in FIG. 4, this problem also occurs when the IC resistance is formed by a semiconductor layer 9 formed on a semiconductor substrate 1 with an insulating film 7 interposed therebetween, such as a semiconductor layer resistance element made of a polysilicon layer. occured. That is, the problem of variations in the ratio of resistance values of resistive elements exists regardless of whether they are diffused resistive elements or semiconductor layer resistive elements.

The present invention has been made to solve these problems, and an object of the present invention is to provide a novel method for adjusting the resistance value of a resistor element made of a semiconductor in an IC. shall be.

[0007]

A method for adjusting the resistance value of a resistance element according to the present invention is characterized in that the resistance value of the resistance element is adjusted by doping the resistance element with an impurity using a focused ion beam.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for adjusting the resistance value of a resistance element according to the present invention will be explained in detail below according to the illustrated embodiments. Figure 1 (A), (B)
) are for explaining one embodiment of the resistance value adjustment method of the resistance element of the present invention, (A) is a plan view, (B) is a B-
It is a sectional view taken along the B line. This embodiment shows a case where one of the two diffused resistance elements R1 (5a) and R2 (5b), for example, R1 is too large to maintain the ratio of R1 and R2 to a predetermined ratio. In this case, naturally, it is necessary to lower the resistance value of the diffused resistance element R1 (5a), and this is done by doping it with a p-type impurity, such as boron B, using a focused ion beam (FIB).

The length of the diffused resistance elements 5a and 5b in this example is, for example, 15 μm, the width is 5 μm, the depth is 0.3 μm,
The distance between the diffused resistance elements 5a and 5b is 10 μm,
The surface of the diffused resistance element 5a is scanned by a focused ion beam with a beam diameter smaller than 5 μm, for example, about 1 to 3 μm, until it reaches half the junction depth (0.3 μm in this case) (0.15 μm in this case). Dope an appropriate amount of impurities. In the drawing, 10 is a focused ion beam, 1
1 is an area that has been scanned, and 11a indicated by a two-dot chain line is an area that has not been scanned yet.

[0010] Such impurity doping increases the impurity concentration of the diffused resistance element 5a, which in turn lowers its resistance value R1, making the ratio R1:R2 of the resistance values of the diffused resistance elements 5a and 5b a predetermined ratio. be able to.

It should be noted that after doping the impurities with a focused ion beam, the diffused resistance element R is formed with a laser beam.
It is preferable to anneal 1(5a) because crystal defects caused by impurity doping with a focused ion beam can be eliminated and crystallinity can be restored. Crystal defects often cause flicker noise and burst noise, but such noise can be reduced by restoring crystallinity through laser beam annealing. In this case, the beam diameter of the laser beam is, for example, 30μ.
M is big and good. This is because it is necessary to prevent impurity doping from protruding into the diffused resistance element whose resistance value is to be lowered, but the laser beam irradiation area for restoring crystallinity is This is because there is no problem even if it protrudes from the impurity-doped diffused resistance element 5a, and furthermore, there is no problem even if it extends to the diffused resistance element R1 (5b) whose resistance value is not adjusted by impurity doping.

The present invention provides diffused resistance elements R1 (9a) and R2 (9b) made of polycrystalline silicon formed on a semiconductor substrate 1 with an insulating film 7 in between, as shown in FIGS. 2(A) and 2(B).
It can also be applied to In this example, each of the semiconductor layer resistance elements R1 (9a) and R2 (9b) is, for example, 15 μm, has a width of 5 μm, has a depth of 0.3 μm, and the interval between the diffused resistive elements 5a and 5b is 10 μm, which is smaller than 5 μm. The thin surface layer of the semiconductor layer resistive element R1 is scanned with a focused ion beam having a beam diameter of, for example, about 1 to 3 μm to dope it with impurities. The reason why the impurity doping depth is made shallow is to prevent the doped impurity from passing through the thin insulating film (for example, several hundred angstroms) 7 and reaching the surface portion of the semiconductor substrate 1. Note that 10 is a laser beam, 11 is a scanned area, and 11a is an unscanned area.

It should be noted that noise reduction can be achieved by annealing the diffused resistive element 5a with a laser beam to improve the crystallinity of the semiconductor layer resistive element after doping with a focused ion beam of impurities. The same is true for .

The present invention is applicable not only to adjusting the ratio of resistance values between resistive elements of a composite resistor consisting of a plurality of resistive elements forming a pair or group, but also to adjusting the resistance value of a single resistive element. can also be applied.

[0015]

The method for adjusting the resistance value of a resistor element according to the present invention is characterized in that a resistor element made of a semiconductor is doped with an impurity using a focused ion beam. Therefore, according to the method for adjusting the resistance value of a resistance element of the present invention,
The impurity concentration of the diffusion layer or semiconductor layer constituting the resistance element can be changed by doping with impurities using a focused ion beam. Therefore, the resistance value of the resistance element can be adjusted.

[Brief explanation of the drawing]

[Fig. 1] (A) and (B) show one embodiment of the method for adjusting the resistance value of a resistance element of the present invention; (A) is a plan view;
B) is a sectional view taken along line B-B of (A).

[Fig. 2] (A) and (B) show other embodiments of the method for adjusting the resistance value of the resistance element of the present invention, (A) is a plan view, and (B)
) is a sectional view taken along line BB of (A).

[Fig. 3] (A) and (B) show conventional examples; (A)
is a plan view, and (B) is a sectional view taken along the line BB of (A).

FIG. 4 is a sectional view showing another conventional example.

[Explanation of symbols]

5a Diffused resistance element (R1) 5b Diffused resistance element (R2) 9a Semiconductor layer resistance element (R1) 9b Semiconductor layer resistance element (R2) 10 Focused ion beam

Claims (1)

[Claims] 1. A method for adjusting the resistance value of a resistor element, which comprises adjusting the resistance value of the resistor element by doping impurities into the resistor element made of a semiconductor of a semiconductor integrated circuit using a focused ion beam.