JP2000114464A - Manufacture of thin-film resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a reversely-tapered cross section of an electrode and a barrier-metal without increasing a manufacturing process. SOLUTION: A thickness of an Al film 5 is set to 300 nm or less and an area ratio of an upper face of the Al film 5 to an upper face of a CrSi resistor 3 is set to 0.02 or more. As an etchant for a TiW film 4, a solution having an ionization tendency Al>TiW>CrSi is used. Setting the film thickness of the Al film 5 to 300 nm or less enables decreasing unevenness of etching depth caused by a battery-effect between the Al film 5, and the TiW film 4 and suppress an overhang of the Al film 5. Setting the above area ratio to 0.02 or more and using the above etchant enable decreasing the etching degree of the TiW film 4 caused by the battery-effect between a CrSi resistor 3 and the TiW film 4 and suppress the undercut of the TiW film 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a thin film resistor provided in a semiconductor device.

[0002]

2. Description of the Related Art FIG. 9 shows a manufacturing flow of a CrSi resistance device using Al as an electrode and TiW as a barrier metal. A conventional method for manufacturing a CrSi resistance device will be described with reference to FIG. First, as shown in FIG. 9A, a CrSi 103 is formed on a silicon substrate 101 on which a semiconductor element is formed via a silicon oxide film 102, and then the CrSi 103 is patterned. Then, as shown in FIG. 9B, TiW 104 as a barrier metal and A as an electrode material cover CrSi 103.
1105 is formed.

After that, as shown in FIG. 9C, etching for patterning the Al 105 is performed using the photoresist 106 as a mask, and subsequently, FIG.
As shown in FIG.
The iW 104 is wet etched to remove unnecessary portions of TiW.

[0004]

FIG. 10 is an enlarged view of a CrSi resistance device manufactured by the above-mentioned conventional method. As shown in this figure, when a CrSi resistance device is manufactured by a conventional method, an Al overhang in which Al 105 is inversely tapered during wet etching of TiW 104 or a TiW undercut in which etching of TiW 104 proceeds to below Al 105 Occurs, and the cross-sectional shape of Al105 and TiW104 becomes an inversely tapered shape as a whole.

With such an inverted tapered cross section,
In particular, when performing integration with other devices such as transistors, a reverse tapered shape is inherited by an interlayer insulating film for insulation separation covering the CrSi resistance device after forming the device,
Further, the wiring formed on the interlayer insulating film and the protective film for protecting the wiring also take over the inverted tapered shape. As a result, problems such as disconnection of the wiring formed above the CrSi resistance device and cracking of the protective film are caused.

As a method of preventing the deterioration of the cross section of the CrSi electrode due to the Al overhang TiW undercut, as shown in FIG. 9C, the photoresist is peeled off as shown in FIG. 11
As shown in FIG. 11B, a new photoresist 107 is formed to cover the opening end of the Al 105, and then TiW is wet-etched as shown in FIG. 11C.

However, in this method, a new resist mask must be formed, and there is a demerit that the number of manufacturing steps increases and the cost increases. The present invention has been made in view of the above problems, and suppresses the cross-sectional shape of an electrode and a barrier metal from becoming an inversely tapered shape without increasing the number of manufacturing steps. The purpose is to prevent cracking.

[0008]

In view of the above problems, the present inventors have studied the factors that cause Al overhang and TiW undercut. It is considered that the Al overhang is caused by the battery effect generated between Al and TiW.

Regarding the TiW undercut,
It is considered that the wet etching contributes to the lateral etching of TiW and the battery effect generated between TiW and CrSi to contribute. When the undercut amount of TiW increases and the interface between Al and TiW is exposed, the Al overhang is accelerated, and the Al overhang increases.

Therefore, by suppressing the battery effect between Al and TiW, Al overhang can be suppressed,
It can be said that TiW undercut can be suppressed by suppressing the lateral etching of TiW by wet etching or the battery effect between TiW and CrSi. Therefore, the following technical means are employed to achieve the above object.

According to the first aspect of the present invention, the thickness of the electrode material (5) is set so as to be 300 nm or less, and the area of the upper surface of the thin-film resistance material (3) is reduced with respect to the area of the electrode material (5). ) Is set so that the ratio of the area of the upper surface is 0.02 or more. Thus, by setting the film thickness of the electrode material (5) to 300 nm or less,
Variations in the etching amount of the electrode material (5) due to a battery effect generated between the electrode material (5) and the barrier metal material (4) can be reduced, and overhang of the electrode material (5) can be suppressed. The area of the barrier metal material (4) in contact with the etching solution can be considered as the area of the upper surface of the electrode material (5). By setting the ratio of the area of the upper surface to 0.02 or more, the etching amount of the barrier metal material (4) due to the battery effect between the thin film resistance material (3) and the barrier metal material (4) is reduced. The undercut of the barrier metal material (4) can be suppressed.

Thus, it is possible to prevent the cross-sectional shape of the electrode and the barrier metal from becoming reversely tapered, thereby preventing disconnection of wiring formed on the thin film resistor and clutching of the protective film. More specifically, the ionization tendency of the thin film resistance material (3), the barrier metal material (4) and the electrode material (5) to the etching as an etching solution is determined by the thin film resistance material (3). If a solution in which the barrier metal material (4) is larger than the barrier metal material (4) and the electrode material (5) is larger than the barrier metal material (4) is used, the metal having a high ionization tendency is etched in the etching by the battery effect. By increasing the area of the metal having a low ionization tendency in contact with the etchant more than the area in contact with the liquid, the amount of etching of the barrier metal material (4) can be reduced.

For example, as an etchant for the barrier metal material (4), NH ₄ OH and H
A solution in which ₂ O ₂ and H ₂ O are composed at a composition ratio of 5: 100: 400 can be used. According to a second aspect of the present invention, the ratio of the area of the upper surface of the electrode material (5) to the area of the upper surface of the thin film resistance material (3) does not exceed 2.0. I have.

Thus, overhang of the electrode material (5) caused by making the ratio of the area of the upper surface of the electrode material (5) to the area of the upper surface of the thin film resistance material too large can be suppressed. . In the invention according to claim 3, the step of etching the barrier metal material (4) includes
The resist (1) used for patterning the electrode material (5)
0) is performed.

As described above, by covering the upper surface of the electrode material (5) with the resist (10) used for patterning the electrode material (5), the upper surface of the electrode material (5) is not in contact with the etching solution. Electrode material (5)
Can be reduced in area in contact with the etching solution. In the invention according to claim 7, after the thin film resistor is patterned by the thin film resistor material (3), a barrier metal material (4) is arranged on the entire upper surface of the substrate (1).
Further, it is characterized in that an electrode material (5) is arranged on the barrier metal material (4).

Thus, by forming the electrode material (5) on the barrier metal material (4) formed on the entire upper surface of the substrate (1), the electrode material (5) comes into contact with the substrate (1). As a result, electrons in the electrode material (5) generated by the battery effect between the barrier metal material (4) and the electrode material (5) can be prevented from escaping to the substrate (1). Accordingly, it is possible to prevent the electrode material (5) from overhanging due to the contact between the substrate (1) and the electrode material (5). In addition to the case of contact with the substrate (1), for example, by preventing the circuit wiring and the like from being in contact with the electrode material (5), electrons in the electrode material (5) do not escape through the circuit wiring and the like. Can be.

[0017] As described in claim 7, CrSi can be used as the thin film resistance material (3), TiW can be used as the barrier metal material (4), and Al can be used as the electrode material.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows a semiconductor device provided with a thin film antibody according to an embodiment of the present invention. As shown in FIG. 1, a CrSi resistor 3 as a thin film resistor is formed on a silicon substrate 1 on which a semiconductor element (not shown) is formed via a silicon oxide film 2. , An Al film 5 as an electrode material is disposed via a TiW film 4 as a barrier metal.

The ends of the TiW film 4 and the Al film 5 are C
It is substantially perpendicular to the surface of the rSi resistor 3 and does not have an inversely tapered shape as a whole. An interlayer insulating film 6 is formed on the entire upper surface of the silicon substrate 1 so as to cover the CrSi film.
Are formed. The interlayer insulating film 6 has a via hole 6a
Is formed through the via hole 6a.
The wiring layer 7 is electrically connected to the Al film 5. Then, a protective film 8 for wiring protection is formed on the entire upper surface of the silicon substrate 1 so as to cover the Al wiring layer 7 and the like.

Since the shapes of the TiW film 4 and the Al film 5 are inherited by the Al wiring layer 7 and the protection film 8, the Al wiring layer 7 and the protection film 8 do not have a reverse tapered shape. With such a configuration, a CrSi resistance device is formed. Next, a manufacturing process of the semiconductor device having the above configuration is shown in FIG. Hereinafter, a method of manufacturing the semiconductor device shown in FIG. 1 will be described with reference to FIG.

[Step shown in FIG. 2A] First, after a semiconductor element is formed on a silicon substrate 1, a silicon oxide film 2 is formed on the silicon substrate 1. And a thickness of 10
After forming CrSi as a thin-film resistance material at a thickness of about 20 nm, a CrSi resistor 3 is formed by patterning. [Step shown in FIG. 2B] Next, a TiW film 4 as a barrier metal material is formed so as to cover the CrSi resistor 3. Further, an Al film 5 as an electrode material is formed on the TiW film 4. At this time, the thickness of the Al film 5 is set to 300 nm.
It is as follows. The reason for this film thickness will be described later.

[Step shown in FIG. 2 (c)] A photoresist 10 is deposited on the Al film 5 and the photoresist 10 is left only in a desired region of the Al film 5. Then, etching is performed using the photoresist 10 as a mask, and the Al film 5 is patterned. At this time, the area of the upper surface of the previously patterned CrSi resistor 3 and the Al film 5
Of the upper surface area (Al film 5 / CrSi resistance 3) is 0.
02 or more and not more than 2.0.

[Step shown in FIG. 2D] The TiW film 4 is patterned by wet etching using the photoresist 10 as a mask. At this time, NH ₄ OH: H is used as an etchant for wet etching.
_A solution having a composition ratio of ₂ O ₂ : H ₂ O = 5: 100: 400 is used.

The ionization tendency of each metal changes depending on the type of the solution. In the solution having the above composition, the ionization tendency becomes Al>TiW> CrSi. For this reason, by using the above-mentioned etching solution, Al is compared with TiW.
The etching of the TiW film 4 can be performed in a state in which the ionization tendency is higher. Further, as described above, the area ratio between the CrSi resistor 3 and the Al film 5 is set to be in a range of 0.02 or more, for the following reason.

FIG. 3 is a schematic diagram for explaining the area ratio between the CrSi resistor 3 and the Al film 5. FIG. 3 (a)
Is a diagram showing the upper surfaces of the CrSi resistor 3 and the Al film 5,
FIG. 3B is a diagram showing a cross-sectional configuration of the CrSi resistor 3 and the Al film 5 corresponding to FIG. In general, in the etching (corrosion) by the battery effect, the area in contact with the etching solution of a metal having a high ionization tendency (hereinafter, referred to as a liquid contact area) is larger than the liquid contact area of a metal having a low ionization tendency. It is known that the etching amount due to the battery effect decreases.

For this reason, the liquid contact area of the TiW film 4 with respect to the liquid contact area of the CrSi resistor 3, that is, the ratio of these liquid contact areas is made large, so that the battery effect generated between the TiW film 4 and the CrSi resistor 3 is caused. The undercut of the TiW film 4 can be reduced. Then, CrSi resistance 3
And the liquid contact area in the TiW film 4 will be examined. First,
Regarding the liquid contact area of the CrSi resistor 3,
Can be considered to be almost only the area of the upper surface of the CrSi resistor 3.

On the other hand, regarding the liquid contact area of the TiW film 4,
Since the upper surface of the TiW film 4 is covered with the Al film 5,
The area around the TiW film 4 corresponds to the area around the TiW film 4. The area around the TiW film 4 is represented by the product of the peripheral length of the TiW film 4 and the thickness of the TiW film 4. The peripheral length of the TiW film 4 and Ti
Since the product of the thickness of the W film 4 and the area of the upper surface of the TiW film 4 are correlated, the area around the TiW film 4 is
Can be considered as the area of the upper surface of

The area of the upper surface of the TiW film 4 is Ti
Since the area of the upper surface of the Al film 5 serving as a mask when patterning the W film 4 is substantially equal to the area of the TiW film 4 ≒ the area of the upper surface of the TiW film 4 面積 the area of the upper surface of the AL film 5. can get. Therefore, the amount of undercut due to the battery effect is determined according to the ratio of the area of the upper surface of the Al film 5 to the area of the upper surface of the CrSi resistor 3.

FIG. 4 shows the area of the upper surface of the CrSi resistor 3 and A
Ti when the ratio of the area of the upper surface of the l film 5 is changed
5 shows a change in the amount of undercut of the W film 4. In this figure, the case where the undercut amount is equal to or more than zero indicates that the Al film 5
This indicates that the TiW film 4 penetrated the inside and was undercut, and when the amount of undercut was less than zero, the TiW film 4 protruded outside the Al film 5 and was not undercut. It shows that.

As shown in FIG.
Ratio of the area of the upper surface of the Al film 5 to the area of the upper surface of the
When the film 5 / CrSi resistance 3) becomes 0.02 or more,
The undercut amount of the TiW film 4 becomes zero or less. Therefore, by setting the ratio of the area of the upper surface of the Al film 5 to the area of the upper surface of the CrSi resistor 3 to be in a range of 0.02 or more,
The undercut of the TiW film 4 between the CrSi resistor 3 and the TiW film 4 due to the battery effect can be suppressed.

When the amount of undercut of the TiW film 4 increases, the amount of exposure at the interface between the TiW film 4 and the Al film 5 increases, and the overhang of the Al film increases. By suppressing the cut, exposure of the interface between the TiW film 4 and the Al film 5 is reduced, and the overhang of the Al film 5 between the TiW film 4 and the Al film 5 due to the battery effect can be suppressed.

Note that, as shown in FIG.
When the area of the upper surface of each of the Al films 5 disposed at both ends of the Al film 5 is different, the area of the upper surface of each
The area of the upper surface of the Si resistor 3 should be within the above range. Subsequently, the thickness of the Al film 5 is set to 300 nm.
The reason for setting is described below. As mentioned above,
The overhang of the Al film 5 is caused by the melting of Al due to the battery effect between the Al film 5 and the TiW film 4. Looking at the change in the etching amount of Al105 due to the battery effect in the CrSi resistance device shown in FIG. 10 formed by the conventional method, the etching amount is large near the interface between Al105 and TiW104, and the etching amount is small on the surface of Al105. ing. This Al105
It is considered that the overhang of Al has increased from the difference in the etching amount of Al. This difference in the etching amount differs depending on the distance from the interface between Al105 and TiW104. It is considered that the overhang increases as the distance from the interface to the upper surface of Al105, that is, as the film thickness of Al105 increases.

Therefore, an experiment on overhang was attempted by changing the thickness of the Al film 5, and FIG.
Are obtained, and the etching amount of the Al film 5 is related to the thickness of the Al film 5, and the thickness of the Al film 5 is 300 nm.
With the point of inflection as the inflection point, it was found that the slope of the change in the etching amount of the Al film 5 changed. Therefore, by making the thickness of the Al film 5 as thin as 300 nm or less, the difference in the etching amount of the Al film 5 due to the battery effect can be reduced, and the overhang of the Al film 5 can be reduced.

Further, by changing the ratio of the area of the upper surface of the Al film 5 to the area of the upper surface of the CrSi resistor 3 described above,
When the change in the amount of overhang of the Al film 5 with respect to each was examined, A
It was found that when the ratio of the area of the upper surface of the 1 film 5 exceeded 2.0, the overhang increased. For this reason,
In the present embodiment, the ratio of the area of the upper surface of the Al film 5 to the area of the upper surface of the CrSi resistor 3 does not exceed 2.0.

By doing so, when patterning the TiW film 4, the undercut of the TiW film 4 due to the battery effect between the CrSi resistor 3 and the TiW film 4 is reduced, and the Al film 5 and the TiW film 4, the overhang of the Al film 5 due to the battery effect can be further reduced. In the present embodiment, the photoresist 10 is left as it is during the patterning of the TiW film 4, in order to reduce the liquid contact area of the Al film 5. That is, the etching by the battery effect of Al and TiW acts in a direction in which the etching of the TiW film 4 to be undercut becomes larger than that of the TiW film 4, and has an effect of preventing the TiW film 4 from being undercut.

After that, an interlayer insulating film 6 is formed on the entire upper surface of the silicon substrate 1 so as to cover the Al film 5 and the CrSi resistor 3, and then a via hole 6a is formed in the interlayer insulating film 6, and further an interlayer insulating film is formed. By forming an Al wiring layer 7 and a protective film 8 which are connected to each other through the via hole 6a in this order, the CrSi resistance device shown in FIG. 1 is completed.

As described above, by setting the ratio of the area of the upper surface of the Al film 5 to the area of the upper surface of the CrSi resistor 3 to be 0.02 or more, the TiW film 4 due to the battery effect between the CrSi resistor 3 and the TiW film 4 is formed. Can be suppressed, and by setting the thickness of the Al film 5 to 300 nm or less, A due to the battery effect between the TiW film 4 and the Al film 5 can be reduced.
Overhang of the 1 film 5 can be suppressed.

Furthermore, the overhang of the Al film 5 can be further reduced by preventing the ratio of the area of the upper surface of the Al film 5 to the area of the upper surface of the CrSi resistor 3 from exceeding 2.0. And C according to the present embodiment is
According to the method for manufacturing an rSi resistance device, overhang of the Al film 5 and undercut of the TiW film 4 can be prevented without increasing the number of manufacturing steps as compared with the conventional manufacturing method.

(Other Embodiments) In the above embodiment, Cr
After patterning the Si resistor 3, a TiW film 4 as a barrier metal and an Al film 5 as an electrode material are
Although the film is formed so as to cover the resistor 3, as shown in FIG. 8, another manufacturing procedure may be adopted. Specifically, as shown in FIG. 8A, a CrSi resistor 13, a TiW
After forming the film 14, the CrSi resistor 13 and the TiW film 14 are patterned using the same mask as shown in FIG. 8B.

Next, as shown in FIG.
After forming an Al film 15 so as to cover the resistor 13 and the TiW film 14, as shown in FIG. 8D, the Al film 15 is patterned using the photoresist 20 as a mask. Thereafter, the TiW film 14 is patterned as shown in FIG. Thus, the CrSi resistor 13 and the TiW film 1
There is also a method of forming an Al film 15 after patterning of the Al.4. Even when such a manufacturing procedure is adopted, by adopting the same manufacturing method as in the above embodiment, the same effect as in the above embodiment can be obtained. Obtainable.

According to the manufacturing procedure shown in FIG.
Since the film 15 is formed directly on the silicon oxide film 12, an effect is obtained that the Al film 15 can be used as a component of another device or as a wiring for connecting the CrSi resistor 13 to another device. However, it was found that when the CrSi resistance device was manufactured by such a procedure, the overhang of the Al film 15 was larger than when the CrSi resistance device was manufactured by the manufacturing procedure shown in FIG.

When an examination was conducted based on this result,
Since the Al film 15 formed on the silicon oxide film 12 comes into contact with the underlying silicon substrate 11 through a contact hole or the like formed in the silicon oxide film 12,
When etching by the battery effect between the Al film 15 and the TiW film 14 is performed, electrons remaining in the Al film 15 flow toward the silicon substrate 1 and the etching of the Al film 15 is accelerated. It is thought that the result was great.

For this reason, when patterning the TiW film 14, it is effective to prevent the Al film 15 from coming into contact with the silicon substrate 11 and other wirings so that electrons remaining in the Al film 15 do not flow. You can say that.

[Brief description of the drawings]

FIG. 1 shows CrS manufactured by applying one embodiment of the present invention.
It is a figure showing the section composition of an i-resistance device.

FIG. 2 is a diagram showing a manufacturing process of the CrSi resistance device shown in FIG.

FIG. 3 is a diagram for explaining the relationship between the area of a CrSi resistor 3 and the area of an Al film 5;

FIG. 4 is a diagram showing the amount of undercut of the TiW film 4 with respect to the ratio of the area of the upper surface of the CrSi resistor 3 to the area of the upper surface of the Al film 5;

FIG. 5 is a diagram for explaining a case where the areas of the upper surfaces of Al films 5 arranged on both sides of a CrSi resistor 3 are different.

FIG. 6 is a diagram showing a correlation between the thickness of the Al film 5 and the etching amount of the Al film 5;

FIG. 7 is a diagram showing the amount of overhang of the Al film 5 with respect to the ratio of the area of the upper surface of the CrSi resistor 3 to the area of the upper surface of the Al film 5;

FIG. 8 is a diagram showing a manufacturing process of a CrSi resistance device according to another embodiment.

FIG. 9 is a view for explaining a conventional method for manufacturing a CrSi resistance device.

FIG. 10 shows Al105 generated by a conventional manufacturing method.
FIG. 3 is a diagram for explaining an overhang and an undercut of TiW104.

FIG. 11 is a diagram showing a method of manufacturing a CrSi resistance device capable of preventing overhang of Al105 and undercut of TiW104 as studied by the present inventors.

[Explanation of symbols]

1. Silicon substrate, 2. Silicon oxide film, 3. CrSi
Resistance: 4 ... TiW film, 5 ... Al film, 6 ... Interlayer insulating film, 6
a ... via hole, 7 ... Al wiring layer, 8 ... protective film, 10 ...
Photoresist.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M104 AA01 BB02 BB19 DD09 DD64 FF04 FF09 FF18 GG19 5F038 AR07 AR16 EZ14 EZ15 EZ20 5F043 AA24 AA26 AA27 BB18 DD30 GG04 GG10

Claims (7)

[Claims] A step of disposing a thin-film resistance material on an upper surface side of a substrate; a step of disposing a barrier metal material on an upper surface of the thin-film resistance material; Disposing an electrode material (5) on the upper surface of the material; patterning the electrode material (5); and etching the barrier metal material (4) based on the patterned electrode material (5). And determining a thin-film resistor made of the thin-film resistor material (3) and arranging a barrier metal at an electrode extraction position of the thin-film resistor. In the step of disposing the electrode material (5), the thickness of the electrode material (5) is set to be 300 nm or less, and in the step of patterning the electrode material (5), A method for manufacturing a thin film resistor, wherein the ratio of the area of the upper surface of the electrode material (5) to the area of the surface is set to be 0.02 or more. 2. In the step of patterning the electrode material (5), the area of the upper surface of the thin film resistance material (3) is
2. The method according to claim 1, wherein the ratio of the area of the upper surface of the electrode material (5) does not exceed 2.0. 3. The patterning step of the electrode material (5) includes a step of arranging a resist (10) having an opening on an unnecessary portion of the electrode material (5), and an etching step using the resist (10) as a mask. And removing the unnecessary portion. The step of etching the barrier metal material (4) is performed with the resist (10) left. The manufacturing method of the thin film resistor according to the above. 4. In the step of etching the barrier metal material (4), the ionization tendency of the thin film resistance material (3), the barrier metal material (4) and the electrode material (5) with respect to the etching is used as the etchant. However, the barrier metal material (4) is more preferable than the thin film resistance material (3).
4. A thin film resistor according to claim 1, wherein a solution is used in which the electrode material (5) is larger than the barrier metal material (4). How to make the body. 5. An etching solution for the barrier metal material (4), wherein NH ₄ OH, H ₂ O ₂ and H ₂ O are 5:
5. The method according to claim 1, wherein a solution having a composition ratio of 100: 400 is used. 6. The step of arranging the thin film resistance material (3) includes a step of patterning the thin film resistor with the thin film resistance material (3). In the step of arranging the barrier metal material (4), In the step of disposing the barrier metal material (4) on the entire upper surface of the substrate (1) including the thin film resistor and disposing the electrode material (5), the barrier metal material (4) was formed on the entire upper surface of the substrate (1). The method for manufacturing a thin film resistor according to claim 1, wherein the electrode material is disposed on the barrier metal material. 7. CrSi as the thin film resistance material (3)
7. The method of manufacturing a thin film resistor according to claim 1, wherein TiW is used as the barrier metal material, and Al is used as the electrode material. 8.