JPS6045050A - Structure of resistor element - Google Patents

Abstract

PURPOSE:To enable to set a high accuracy resistance value in a super miniature resistor element by a method wherein a polycrystalline Si film of an extremely high specific resistance is formed, and its partial region is added with impurities. CONSTITUTION:An Si oxide film 2 is produced by thermal oxidation of an Si substrate 1, and the polycrystalline Si film 13 is produced and adhered over the entire surface of the substrate by vapor phase reaction. The part of lateral stretching of an Si oxide film 6 is covered with a photo resist, and a photo resist pattern 12 is formed so as to obtain a desired resistor width W2. Thereafter, boron atoms are ion-implanted over the entire surface of the substrate shallowly by a desired amount at a low accelerating voltage, and then the impurity atoms are activated by heat treatment in nitrogen, resulting in the formation of a resistor region 17 of a nearly constant impurity concentration. Here, the depth t2 of the resistor region can be controlled by the accelerating voltage for ion implantation and the thicknesses of an Si oxide film 4 and an Si nitride film 5. On the other hand, the width W2 of the resistor region can be controlled entirely independently of the lateral stretching width W of the Si oxide film 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-small resistor element, and preferably to an ultra-small resistor element used in a semiconductor integrated circuit device.

Currently, as this type of resistor element, polycrystalline silicon regions separated by silicon oxide films are being used instead of single crystal silicon regions separated by PN junctions. The reasons for this are that the isolation area is small, the device can be miniaturized, the voltage-current characteristics are linear, the parasitic capacitance is reduced, and a multilayer structure can be easily formed, so there is a high degree of freedom in design.

etc. are mentioned.

Figures 1 (a) to (d) and (e) to (h) show a conventional resistor element (hereinafter referred to as an ultra-small linear resistor element) using polycrystalline silicon regions separated by a silicon oxide film. FIG. 2 is a cross-sectional view and a vertical cross-sectional view illustrating the manufacturing process. First, as shown in Figures 1(a) and (e),
A silicon oxide film 2 is generated by thermally oxidizing a silicon substrate 1, a polycrystalline silicon film 3 having a thickness of tl is deposited on the entire surface of the substrate by a gas phase reaction, and high temperature heat treatment is performed in a nitrogen atmosphere. Additionally, the quality of the polycrystalline silicon film is stabilized.

Next, a thin silicon oxide film 4 is formed on the polycrystalline silicon film 3 by thermal oxidation, and then a thin silicon nitride film 5 is formed and deposited over the entire surface of the silicon oxide film 4 by a vapor phase reaction. . Next, use photoresist to remove all the silicon nitride film except on the part that will become the future resistance element, and then perform high-temperature oxidation treatment as shown in Figures (b) and (f). In particular, the polycrystalline silicon film 3 that is not replaced by the silicon nitride film 5 is converted into a thick silicon oxide film 6.

Next, boron atoms are ion-implanted to a desired depth over the entire surface of the substrate at a high acceleration voltage, and then heat treatment is performed in nitrogen to activate the implanted impurity atoms. As shown in c) and (g), a resistor region 7 in which the impurity level is constant (that is, the resistivity ρ1 is constant) is formed over the entire region of the polycrystalline silicon film. Next, as shown in Figures (d) and (h), the remaining silicon nitride film 5 is removed, and holes for resistive electrodes are made in the silicon oxide film 4 using photoresist, covering the entire surface of the substrate. A platinum thin film is deposited and subjected to low-temperature heat treatment in a nitrogen atmosphere, and a platinum silicide layer 8 is formed on the resistive electrode part in a self-aligned manner.
After forming (forming an ohmic contact), the remaining platinum on the silicon oxide P is removed. Next, a silicon oxide film 9 is formed and deposited over the entire surface of the substrate by a gas phase reaction, and after opening through holes with photoresist, aluminum 10 is deposited over the entire surface of the substrate. Form a wiring pattern or a bonding pad for the device.

In this structure, the resistance value R4 is expressed by equation (1).

Here, ρ is the specific resistance 1 of the resistor region, t is the length of the resistor region, t is the depth of the resistor region, that is, the thickness of the polycrystalline silicon film) W,' is the effective width of the resistor region W is the pattern design IJ of the resistor region; W is the width of the silicon oxide film 6;

The accuracy of the resistance value R, is ρI + jl + W1'+7
The improvement can be achieved by reducing manufacturing variations in each value of 'l. However, among these, the thickness t of the polycrystalline silicon film 3 and the lateral spread [IJ] of the silicon oxide film 6 are usually the most difficult to control, and there are large manufacturing variations, and the resistance value R, This caused a decrease in accuracy.

As described above, in the conventional ultra-small linear resistor element structure, it is difficult to control the resistance value R1, and the resistance value R1 is determined by parameters with large manufacturing variations, so that the resistance value accuracy is low.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide an ultra-small linear resistor element structure having a highly accurate resistance value.

The resistor element structure of the present invention is obtained by forming a polycrystalline silicon film with extremely high specific resistance and adding impurities to a partial region of the polycrystalline silicon film to form a resistor region.

Next, a manufacturing process for an embodiment of the present invention will be explained. FIGS. 2(a)-(d) and (e)-(h) are a cross-sectional view and a vertical cross-sectional view for explaining the manufacturing process of a resistor element structure according to an embodiment of the present invention. First, Figure 1(a),
As shown in (e), a silicon substrate 1 is thermally oxidized to form a silicon oxide film 2, and a polycrystalline silicon film 13 having a thickness of 11 is deposited over the entire surface of the substrate by vapor phase reaction. At this time, in order to make the specific resistance of the polycrystalline silicon film 13 sufficiently high, for example, the acid content of the polycrystalline silicon film increases.
In step 4, gas phase reaction conditions are set. Figure 2 below (+)),
The steps up to (f) are formed by the same process 4ji as in FIG. 1(b) and (f)-. Next, as shown in FIGS. 2C and 2G, a photoresist is used to cover the laterally expanding portion of the silicon oxide film 6, and a photoresist pattern 12! is formed so as to obtain the desired resistance W2! After forming C, boron atoms are ion-implanted in a desired amount over the entire surface of the group at a low acceleration voltage, and then heat treatment is performed in nitrogen to activate the implanted impurity atoms and increase the depth. t
2, the resistor region 17 in which the impurity gt= is almost constant (t, that is, the specific resistance ρ2 is constant) is formed into a shape 1j2. Next, as shown in FIG.
d) and (h), after removing the photoresist 12, they are formed in exactly the same steps up to FIG. 1(d) and (IJ).

In this structure, since the resistivity e of the polycrystalline silicon region without the impurity horns 11 is sufficiently high, the resistance value is determined by the low resistivity region to which the impurity is added. The resistance value R, is expressed by equation (2), where ρ2 is the specific resistance of the resistor region! , is the length t2 of the resistor region, is the depth W of the resistor region, is l, and is rlj of the resistor region.

Here, the depth t2 of the resistor region is determined by the acceleration voltage of ion implantation and the thickness K of the silicon oxide film 4 and the silicon nitride film 5. For example, depending on the variation in the thickness of these films, the acceleration voltage By adjusting the depth, the variation Δ12/1. is the variation Δt + / t with respect to the set value of the polycrystalline silicon film thickness mentioned above
It is also possible to control so that r and p become smaller. In addition, rllW of the resistor region is completely unrelated to the transverse wave width W of the silicon oxide film 6, and the variation ΔW/W with respect to its set value is different from the set value of the above-mentioned effective resistance rfJVq. It can be controlled so that the variation ΔW,'/WI' is smaller than that.

Therefore, the variation ΔR,/R, /B, of the resistance value n, with respect to the designed value in the resistor element structure of the present invention is the variation ΔR, /R,
, yoυ also becomes smaller. In other words, the accuracy of the resistance value can be improved.

FIG. 2 shows measures against variations in the thickness of the polycrystalline silicon film 13 (
1) and measures against variations in the structural width of the silicon oxide film 6 (2)
) are taken at the same time, but even if only one of these measures is taken, the accuracy of the resistance value can be improved compared to the current level. FIG. 3 shows countermeasure (1) in which the resistance region 27 is provided by limiting impurity addition to the polycrystalline silicon film 13 only in the depth direction, and FIG. 4 shows countermeasure (1) in which impurity addition is limited to the lateral direction. This figure shows an example of countermeasure (2) in which a resistance region 37 is provided.

Second. Third. In the example shown in FIG. 4, the impurity is added by ion implantation, but it is also possible to add the impurity by thermal diffusion instead. Furthermore, the ohmic contact may be formed by diffusing high concentration boron into the resistive electrode portion instead of generating platinum silicide.

As explained above, according to the structure of the present invention, a highly accurate ultra-small linear resistor element structure can be obtained.

[Brief explanation of the drawing]

Figures 1 (a) to (d) and (e) to (h) are a cross-sectional view and a vertical cross-sectional view respectively illustrating the manufacturing process of a conventional resistor element structure, and Figure 2 (→~(d+, ( 'e)～(h)
3(a) and 3(b) are a cross-sectional view and a vertical cross-sectional view of another embodiment of the present invention, and FIG. (a) and (b) are a cross-sectional view and a longitudinal cross-sectional view of still another embodiment of the present invention. 1...Silicon substrate, 2...Silicon oxide film, 3.13...Polycrystalline silicon film, 4...
- Thin silicon oxide film, 5... Silicon nitride film, 6... Thick silicon oxide film, 7.1
7,27.37...Polycrystalline silicon film doped with impurities, 8...Platinum silicide layer, 9...
...Vapour-grown silicon oxide film, 10...Aluminum, 12...Photoresist film. (u) (8) (b) (f) (C) ('j) (d) < k ) (tl) ,. (C) (tj,) ((f),7ii((Z) form fan・ <b> 3 closed (b) pu 15

Claims (1)

[Claims] By selectively oxidizing a polycrystalline silicon film with high specific resistance provided on an insulating film of a semiconductor substrate,
A resistor element structure characterized in that an impurity is added only to a partial region of the polycrystalline silicon film separated from other elements by silicon oxide.