JPH0414863A - Forming method for resistance element of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a resistance element having high resistance without increasing the length of the element by forming a second conductivity type region partly at the element, and reducing the sectional area of the resistance part to be conducted. CONSTITUTION:Part of a high resistor 3A except a region S2 is masked with photoresist, and P-type impurity ions such as second conductivity type boron, etc., are so implanted in polycrystalline silicon 3 of the region S2 in a predetermined depth. Thus, the region S2 becomes a reverse conductivity type region 4 of second conductivity type to form a junction to a region S1 in which an N-type impurities are implanted. Thereafter, with photoresist as a mask an unnecessary part is etched to form a resistance element R of the resistor 3A and the region 4, and a wiring W is formed of a low resistor 3B. Thus, even if a current is fed in an arbitrary direction in the region 4, a current is scarcely fed, and the resistor 3A formed previously is reduced in sectional area in thickness corresponding to the region 4, thereby enhancing its resistance value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for forming a resistor element of a semiconductor device having a resistor element, which includes a resistor element having a region that is a reverse junction in a part of the resistor element. Concerning the method of forming.

[Conventional technology]

Conventionally, as a method for forming a resistance element in a semiconductor device by introducing impurity ions, there is a method described in, for example, Japanese Patent Laid-Open No. 60-74465.

That is, depending on this method, first, polycrystalline silicon is formed on a substrate whose upper surface is insulated, and a low-resistance material serving as a wiring is formed by introducing N-type or P-type impurities into the polycrystalline silicon. Then, a predetermined region is masked with photoresist, and other than this region, impurity ions of the opposite type to the impurity ions introduced into the polycrystalline silicon are superimposed, and the low-resistance element in this region becomes a high-resistance element. A resistive element is formed in a semiconductor device by changing it into a resistor.

Thus, depending on the method of forming this resistance element, the concentration gradient of ions between the high resistance element and the low resistance element becomes low.
When introducing impurity ions into polycrystalline silicon, the effect of preventing the impurity ions from diffusing outside the masked region can be obtained.

[Problem to be solved by the invention]

However, in recent years, semiconductor devices have become highly integrated, and the resistance elements formed in these semiconductor devices have a width of 1
Although the size has been reduced to ~2μ and length of 2 to 4μ, high resistance values of 10' to 1012Ω are required.

Depending on the method of forming the conventional resistance element, the thickness of the high resistance element that becomes the resistance element and the low resistance element that becomes the wiring becomes the same, but as the cross-sectional area of the wiring becomes smaller, the wiring resistance increases. In order to increase the resistance value of a resistor element, it is not possible to reduce the thickness of the polycrystalline silicon itself.Therefore, in order to increase the resistance value of a resistor element, it is necessary to make the resistor element longer. First, it has been difficult to form a small resistance element with high resistance as described above.

It is also possible to reduce the thickness of the resistor element by processing the resistor element formed in the conventional example and etching only the high-resistance part, but this may result in insufficient strength of the resistor element and may cause problems such as cranking. This was not a desirable method because it made the process easier and the durability decreased.

On the other hand, during the growth process of polycrystalline silicon, oxygen is leaked to form a silicon oxide film several times thicker, and polycrystalline silicon is grown on top of it by repeating the process to reduce the brain size of polycrystalline silicon. However, although a method of increasing the resistance value has been proposed, this method has problems in that the growth process of polycrystalline silicon is complicated, resulting in a poor yield, and the etched shape also deteriorates.

Therefore, the present invention has been made in consideration of such problems, and an object of the present invention is to form a high-resistance and small-sized resistance element, while not reducing the strength of the resistance element. The object of the present invention is to propose a method for easily forming a resistance element that has excellent durability and a high yield when forming the resistance element.

[Means for Solving the Problems] The present invention includes a step of forming a resistor portion to become a resistor element using polycrystalline silicon into which impurity ions of a first conductivity type are introduced onto a substrate, and a step of forming a resistor portion to be a resistor element using polycrystalline silicon into which impurity ions of a second conductivity type are introduced. A method for forming a resistor element of a semiconductor device is proposed, comprising the step of: introducing a second conductivity type region from the surface of at least a portion of the resistor portion to a predetermined depth, and Solving problems.

[Operation] A resistive portion serving as a resistive element is formed on a substrate using polycrystalline silicon into which impurity ions of either N type or P type are introduced as a first conductivity type. Then, by introducing impurity ions of the second conductivity type, which are of the opposite type to the previously introduced impurity ions, into at least a part of this resistance part to a predetermined depth, a second conductivity type region is formed in this part. Then, a PN junction is formed in the same region.

In this state, even if current is passed through the resistor in any direction, it is difficult to conduct current through one junction of the ninth conductivity type region, so the cross-sectional area of the resistor that can conduct current is reduced accordingly. However, the resistance value of the resistance element increases. Therefore, a high-resistance resistor element can be formed without increasing the length of the resistor element, thereby achieving high integration.

In addition, since the thickness of the resistor element itself remains the same as the thickness of the polycrystalline silicon that was initially formed, there is no decrease in strength, resulting in a resistor element with excellent yield and durability. It is possible.

Furthermore, by adjusting the length, depth, and width of the opposite conductivity type region, the resistance value of the resistance element can be easily controlled.

〔Example〕

Next, one embodiment of the present invention will be described below. FIGS. 1A to 1C are explanatory diagrams of a process for forming a resistance element according to an embodiment of the present invention.

First, the process shown in FIG. 1(a) will be explained. In order to electrically isolate the semiconductor substrate 1 from wiring to be formed in a later process, an insulating film 2 such as a silicon oxide film is formed on the upper surface of the substrate 1, and then this insulating film is further removed. 400 to 6000 layers of non-doped polycrystalline silicon 3 are stacked on top of the layer 2.

Then, on this polycrystalline silicon 3, lXl0''~2X
10 By implanting N-type impurity ions such as phosphorus, which is the first conductivity type, at a low dose of about "C11-",
This polycrystalline silicon 3 is used as a high resistance body 3A which is a resistance portion.

Next, the process moves to the step shown in FIG. 1(b), using a photoresist (not shown) patterned by lithography technology to match the region Sl in which the resistive element is to be formed.
Mask Jet S+. And open area S
, 2x l Q 1 in the polycrystalline silicon 3 in the area other than ,
Further, N-type impurity ions such as phosphorus are implanted at a high dose of about 5 to 5 X I Q "am-" to lower the sheet resistance of this region and form a low-resistance element 3B. On the other hand, impurity ions are not implanted into the region S masked as described above, and the region SI remains as the high resistance element 3A.

Further, proceeding to the step shown in FIG. 1(C), areas other than a part S2 of the high-resistance element 3A are masked with photoresist (not shown), so that the polycrystalline silicon 3 in this area S2 has a second conductivity type. , P-type impurity ions such as boron are implanted to a predetermined depth.

Then, heat treatment is performed at 950 to 1000°C to activate impurity ions.

By implanting this P-type impurity ion, the region S2 becomes
This becomes an opposite conductivity type region 4 which is a second conductivity type region, and forms a junction with the region Sl into which N type impurity ions are implanted. After this, the polycrystalline silicon 3 is further masked with photoresist and unnecessary parts are etched to form a resistance element R by the high resistance element 3A and the conductive area 4, and the wiring W by the low resistance element 3B. form. Note that the formation of the wiring pattern etc. may be performed before the implantation of the second conductivity type ions.

Here, the thickness of the opposite conductivity type region 4 is 1000 to 3000 when the thickness of the polycrystalline silicon 3 is 4000. This depth is determined by controlling the implantation speed and implantation time of impurity ions. It can be adjusted by

Further, the length and width of this opposite conductivity type region 4 can be easily adjusted by changing the size of the photoresist.

In this way, it becomes difficult for current to flow through the opposite conductivity type region 4 even if the current is passed in any direction, and the cross-sectional area of the previously formed high resistance body 3A is reduced by the thickness of this opposite conductivity type region 4. Therefore, the resistance value can be made higher, while the thickness of the resistance element R itself remains the same as the thickness of the polycrystalline silicon 3 and does not become thinner, so the strength does not decrease.
As a result, semiconductor devices with excellent durability and yield can be produced.

Further, the resistance value of the resistance element can be easily controlled by changing the depth, length, and width of the opposite conductivity type region 4, and a desired resistance value can be easily set.

In this embodiment, the opposite conductivity type region 4 is formed at one location, but the method of the present invention is not limited to this, and may be formed at a plurality of locations at intervals.

Furthermore, in this example, the first conductivity type impurity ions implanted first were N type, and the second conductivity type impurity ions implanted later were P type, but the types of these impurity ions were reversed. Of course, it is also possible to implant P-type material first and then implant N-type material later.

[Effects of the Invention] As explained above, depending on the method for forming a resistor element of the present invention, a second conductivity type region is formed in a part of the resistor element to reduce the cross-sectional area of the resistor part that conducts current. A resistive element with high resistance can be obtained without increasing the length of the element, and high integration can be achieved. Further, since it is not necessary to make the thickness of the resistive element itself equal to 1, the strength of the resistive element does not decrease, thereby making it possible to form a resistive element with excellent durability.

Further, according to the present invention, a high-resistance resistor element can be easily formed simply by introducing impurity ions of the opposite type, so the process for forming the resistor element is simple, and the resistor element can be formed with high yield. can.

Furthermore, by changing the depth, length, and width of the second conductivity type region, the resistance value of the resistance element can be easily controlled.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a process for forming a resistance element in an embodiment of the present invention. In the figure, 1 is a substrate, 2 is an insulating film, 3 is polycrystalline silicon, 3
A is a high resistance element (resistance part), 3B is a low resistance element, and 4 is an opposite conductivity type region (second conductivity type region).

Claims (1)

[Claims] (1) In a method of forming a resistance element in a semiconductor device,
A step of forming a resistor section to become a resistor element using polycrystalline silicon into which impurity ions of a first conductivity type are introduced on a substrate, and a step of injecting impurity ions of a second conductivity type from at least a part of the surface of the resistor section in a predetermined direction. 1. A method for forming a resistor element in a semiconductor device, comprising the step of: forming a second conductivity type region by introducing the region to a depth of .