JP3288301B2 - Thin film resistor, method of manufacturing the same, and wiring board incorporating the thin film resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of electronic technology, and relates to a thin-film resistor that operates as a passive element, a method of manufacturing the same, and a wiring board incorporating the thin-film resistor.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for downsizing of a mounting substrate, and reports of a substrate having a built-in resistor have been increasing. The structure of the built-in resistor substrate is classified into a substrate including a chip resistor component, a substrate including a thick film resistor (paste), and a substrate including a thin film resistor. There is a limit to miniaturization of a substrate with a built-in chip resistance component, and there is a problem that the accuracy of the resistance value cannot be increased with a substrate with a built-in thick film resistor. A substrate having a built-in thin film resistor is most excellent in miniaturization, and can have relatively high resistance value accuracy.

[0003] As for the resistors used for the substrate with a built-in thin film resistor, Nichrome alloy, tantalum nitride, ITO (Indium Tin Oxide), and metal silicide are reported in Japanese Patent Application Laid-Open No. 4-174590. However, when these thin films are used, in a patterning method, there is a problem that the substrate is deteriorated in wet etching because a strong acid is used, and there is a problem that the process becomes long in dry etching. Also, depending on the type of the resistor, there is a problem that it is difficult to selectively etch the resistor and the electrode or the wiring even in the wet etching method.

[0004] As reported in Japanese Patent Application Laid-Open No. 63-156341, a titanium nitride thin film has been conventionally used as a contact barrier for a semiconductor device. In addition, JP-A-3-27
Japanese Patent No. 6755 reports a method of manufacturing a semiconductor device using TiN as a barrier metal and a resistor in a semiconductor element. However, this resistor was related to a TiN polycrystalline thin film. The resistance of the TiN polycrystalline thin film is 20-25 [μΩ · cm] for a small one and 13
00 (μΩcm), respectively, J. Vac.Sci.
Technol. A5, p1778 (1987), Proceedings of the Semiconductor Integrated Circuit Technology Symposium, 28, p97 (1985). As described above, the TiN polycrystalline thin film has problems that it is difficult to manufacture a high-resistance thin film and that the temperature coefficient of resistance is large.

On the other hand, Japanese Patent Application Laid-Open No. 61-148732 discloses TiN produced by high-frequency magnetron sputtering,
There has been reported an example in which an amorphous metal compound which is a metal nitride such as TaN is used as a heating resistor for a temperature-sensitive element. However, since this resistor has a resistance value change due to temperature, it is not suitable as a normal circuit resistor such as a terminating resistor.

[0006] The composite comprising amorphous and crystalline titanium nitride is disclosed in JP-A-3-6362 as a surface treatment layer of stainless steel, and in JP-A-9-209120 as a coating layer on a hard substrate. JP-A-9-209121 discloses a coating layer on a hard substrate, JP-A-3-132006 discloses a non-magnetic thin film for a magnetic head, and JP-A-4-2021818 discloses a semiconductor contact barrier. . These manufacturing methods include, in the order of the above publications, a method in which Ti is ion-implanted into stainless steel in an atmosphere containing nitrogen, and a method in which titanium nitride formed on a hard substrate by an arc ion plating method using cathode arc discharge. Injecting monovalent boron ions into the coating layer, Injecting monovalent boron ions into the titanium nitride coating layer formed on the hard substrate by arc ion plating using cathode arc discharge 300 after ion beam sputtering
It is disclosed that heat treatment is performed at a temperature of [° C.] or more, and ion implantation is performed after forming a TiN crystal film. As described above, there is a problem that the process of forming a composite including amorphous and crystalline titanium nitride is complicated.

[0007]

As described above, the conventional thin-film resistor has a problem that the substrate on which the thin-film resistor is formed is deteriorated at the time of etching and a problem that it takes too much time in the thin-film resistor forming process. there were. Further, when a polycrystalline titanium nitride thin film is used as a resistor, there is a problem that it is difficult to form a high resistivity thin film and the temperature coefficient of resistance is large. Further, when forming a complex composed of amorphous and crystalline titanium nitride, there is a problem that the manufacturing process becomes complicated.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film resistor which can be easily formed by wet etching, has excellent resistance temperature characteristics and is easy to manufacture, a method of manufacturing the same, and a thin film resistor. An object of the present invention is to provide a wiring board having a built-in body.

[0009]

A thin film resistor according to the present invention comprises a titanium nitride crystal deposited at the time of film formation and a composite of titanium nitride and titanium nitride amorphous. Further, the method of manufacturing a thin film resistor according to the present invention uses the nitrogen gas as a process gas and manufactures the thin film resistor according to the present invention using a titanium target and DC magnetron sputtering. At this time, by controlling the partial pressure of nitrogen during sputtering, the resistance value can be controlled by changing the amount of nitrogen in the composite.

The number of nitrogen atoms occupying the complex is preferably 1/3 to 2/3 of the whole. The reason is that, when it is less than 1/3, the amount of Ti crystal precipitated increases, causing a problem of increasing the temperature coefficient of resistance.
If the value is 3 or more, the amorphous phase becomes unstable, and there is a problem that the resistance value changes with time. Further, the specific resistance of the thin film resistor is required to have a wide range of values. For example, in order to obtain a resistance value of 50Ω, a specific resistance of 0.1 [mΩ
[Cm] using a material having a thickness of 20 nm and the same width and length. Conversely, a resistor patterned with the same dimensions as the resistor, for example,
If a material of 100 [mΩ · cm] is used, a 50 kΩ resistor can be obtained. It is possible to adjust the resistance value by changing the dimensions, but in general, if the thickness of the thin film is too small, there is a problem that defects occur in the film or physical properties change due to the strong influence of the surface structure. To increase the thickness, there is a problem that the process time becomes longer, and there is a problem that separation from the substrate occurs due to an increase in stress in the film. Changing the ratio of the width to the length is not suitable from the viewpoint of miniaturization of the resistor. Usually, different materials are used to cover the range of resistance, but the thin film resistor of the present invention can obtain a wide range of resistance using one target.

A titanium nitride crystal or a composite of at least one of titanium crystals and amorphous titanium nitride can form a wet etching pattern with high dimensional accuracy. Therefore, it is possible to reduce the cost by shortening the process and improve the accuracy of the resistance value. In addition, by using such a composite, the ratio between titanium and nitrogen in the resistor thin film can be given a range, so that the resistance temperature characteristics can be improved and the resistance value range can be expanded. .

[0012]

FIG. 12 is a schematic sectional view showing a conventional titanium nitride thin film. Titanium nitride thin film 5
0 is formed on the substrate 52. Titanium nitride thin film 5
0 indicates that the pattern can be easily formed by wet etching. However, when the titanium nitride thin film 50 is used as a resistor, there is a problem that the temperature coefficient of resistance is large and the width of the obtained specific resistance is narrow. This is shown in FIG.
Since the titanium nitride thin film 50 is a stoichiometric polycrystalline thin film of TiN composed of many columnar crystals 54 as shown in FIG. It was because it was.

The inventor of the present invention has prepared a resistor thin film made of a titanium nitride crystal deposited at the time of film formation and a composite of titanium nitride and at least one of the titanium crystals, and the amount of crystal in the resistor thin film. It has been found that the temperature coefficient of resistance and the resistance value vary greatly depending on the ratio between the amount of manganese and the amount of amorphous material or the ratio between titanium and nitrogen.

FIG. 1 is a schematic sectional view showing a resistor thin film according to the present invention. It is considered that the resistor thin film 10 has a structure in which the crystal particles 14 are precipitated in the matrix of the amorphous titanium nitride 12. The resistor thin film 10 is formed on a substrate 16. The crystal particles 14 are composed of at least one of a titanium nitride crystal and a titanium crystal. In addition,
Although the crystal grains 14 are clearly shown in FIG. 1 for easy understanding, it is considered that the actual crystal grains 14 are minute and the interface with the amorphous is not clear. The resistor thin film 10 tends to have a longer etching time as the thin film has a higher ratio of nitrogen, but also has a good wet etching property.

When a thermal history is applied to a titanium nitride thin film made of only an amorphous material, crystals are deposited in the thin film and the resistance value is greatly changed. On the other hand, the resistor thin film 10
Is deposited as a composite during film formation,
The change in the resistance value due to the heat history of [° C.] or less was reduced.
This is presumably because the amorphous and the crystal of the composite are in an equilibrium state. Suitable titanium nitride crystals that can be included in the composite include, but are not limited to, TiN and Ti ₂ N.

The resistor thin film 10 is suitable as a substitute for a chip resistor used for a mounting board, and can form a resistor on the surface or inside of the board 16. As the substrate 16, a Si substrate with an insulating layer, a printed substrate, a build-up substrate, a ceramic substrate, or the like is suitable, and the thin-film resistor 10 may be formed on either the inner layer wiring or the surface. In addition, suitable Si substrates and ceramic substrates include:
It also includes a multilayer wiring board having an organic insulating layer on the surface. In that case, the resistor forming portion may be either inside the inner layer wiring of the organic multilayer portion or on the surface. In particular, when a resistor is formed in the inner layer of the substrate, the mounting area on the substrate surface can be greatly reduced without changing the thickness of the substrate, which greatly contributes to downsizing of the substrate. The substrate 10 may be, for example, an organic film, a glass plate, a metal foil, or the like.

With respect to the method of forming the thin film resistor of the present invention in the circuit of the wiring board, the following two suitable methods are given. In the first forming method, as shown in FIG. 2, a thin film resistor 10 is formed on a substrate 16, a pattern is formed by photolithography, and then a wiring 18 is formed. In the second forming method, as shown in FIG.
The thin film resistor 10 is formed on the substrate 16 on which the substrate 8 is formed,
The pattern is formed by photolithography. Of course, it is not limited to these forming methods.

The thin film resistor 10 is preferably formed by DC magnetron sputtering using a titanium target and a nitrogen gas. At this time, the ratio between titanium and nitrogen in the thin film resistor 10 can be controlled by the gas pressure during sputtering. Further, by controlling the gas pressure during sputtering, the substrate temperature, and the sputtering power, the type and amount of crystals in the thin film can be controlled. In particular, when a certain temperature is applied to the substrate 16 during sputtering, a change in resistance value when heat history is applied to the thin film is reduced. The substrate temperature at the time of sputtering is preferably 500 [° C.] or less, and particularly when a film is formed at a substrate temperature of 200 [° C.] or less, good resistance characteristics can be obtained.

[0019]

Next, an embodiment of the present invention will be described.

A silicon wafer having an oxide film formed on its surface,
Then, a thin film resistor made of a titanium nitride composite was formed on a printed circuit board FR-4 having a surface coated with an epoxy resin. At this time, a thin film resistor was formed by reactive sputtering using a titanium target and nitrogen gas using a sputter-up type in-line DC sputtering apparatus. The pressure inside the chamber of the sputtering equipment is 9.9 × 10 ^-7
After evacuation to [Torr] or less, the orifice aperture was controlled to 0.5 to 10 [mTorr] while introducing nitrogen into the chamber at 50 [sccm] during film formation. Substrate temperature is 25 ~ 200
(° C), the substrate moving speed on the target is 100 to 500 (mm
/ min], and the sputter current was 2.5 to 8 [A]. These thin film resistors (hereinafter referred to as “samples”) are provided by Van der Pauw
The sheet resistance was measured by a method, the film thickness was measured by a stylus-type film thickness meter, and the thin film structure was analyzed by X-ray diffraction.

FIG. 4 shows the film forming conditions, film thickness, and specific resistance of the manufactured sample. For each film forming condition, 50 samples cut into a square of 10 mm were measured at room temperature, and their average value was defined as a specific resistance value. The film thickness on the printed board could not be measured because the surface roughness of the board was too large. Therefore,
Assuming that the specific resistance of the sample formed on the printed board has the same film thickness as the sample on the Si substrate manufactured at the same time,
It was calculated from the measured sheet resistance.

The specific resistance of the sample under the film forming conditions shown in FIG.
0.209 to 13.315 (mΩcm) for Si substrate, 0.3 for FR-4 substrate.
280 to 21.147 [mΩ · cm]. With any of the substrates, a wide range of resistance values could be obtained by changing the film forming conditions. In particular, the sample prepared at a nitrogen gas pressure of 10 [mTorr] showed a very large resistance value exceeding 10 [mΩ · cm]. The large change in the resistance value of the sample depending on the film formation conditions is considered to be due to the difference between the ratio of titanium and nitrogen in the thin film and the type or amount of crystal in the thin film. In addition, the specific resistance values of all the samples were accurate to within ± 5 [%]. In particular, the samples of Nos. 13, 14, 27, and 28, which have a substrate temperature condition of 150
High accuracy within [%]. It is considered that heating the substrate improves the uniformity of the titanium nitride thin film.

With respect to the samples of Nos. 10, 13, 24 and 27, the temperature characteristics of the resistors were measured by measuring the resistance values at 20 ° C. and 150 ° C. As a result, the respective temperature coefficients of resistance were -87.4 [ppm / ° C], 186.2 [ppm / ° C], -24.3
[Ppm / ° C] and 137.8 [ppm / ° C], showing good temperature characteristics. Thus, it was clarified that the positive and negative signs of the temperature coefficient of resistance were reversed by the change in the nitrogen gas pressure under the film forming conditions. Therefore, the temperature coefficient of resistance can be made closer to zero by optimizing the film forming conditions.

Next, the result of evaluating the structure of the manufactured sample by X-ray diffraction will be described.

The X-ray diffraction results of the samples Nos. 1, 15, 13, 27, 11, and 25 in FIG.
9 and 10. The sample No. 1 in FIG.
FIG. 11 shows the results of X-ray diffraction of the sample heat-treated at [° C.] for 5 minutes. For these X-ray diffractions, CuKα rays were used.

In each of the diffraction patterns shown in FIGS. 5 to 11, broad and low-intensity diffraction lines are observed around 2θ = 36 °. In the figure, the surface distance d at the vertex of the diffraction line near 2θ = 36 [°] is shown. These diffraction lines are considered to be diffraction lines of a titanium nitride crystal, and the reason why the intensity is broad and small is considered to be that the degree of crystallinity is low and an amorphous state is included.

On the other hand, the peak at 2θ = 36.7 ° in the sample subjected to the heat treatment at 1000 ° C. in FIG. 11 is sharp and has a high intensity, and is identified as a diffraction line of the (111) plane of the TiN crystal. This indicates that the amorphous titanium nitride was crystallized by the heat treatment.

Also, TiN (111), Ti ₂ N (200), T
The surface spacing of i (100) is JCPDS card 38-1420, respectively.
, 17-0386, 44-1294, 0.245 [nm], 0.247 [n
m] and 0.256 [nm]. Therefore, FIGS.
The broad peak around 2θ = 36 [°] of 0 is Ti
This shows that all the crystals of N, Ti ₂ N, and Ti are present. The plane spacing d at the diffraction line apex changes depending on the manufacturing conditions of the sample because the ratio of these crystals contained in the thin film is different, the amorphous structure is different,
It is conceivable that the ratio between titanium and nitrogen is different.

[0029]

According thin-film resistor according to the present invention, during deposition
By a composite of at least one titanium nitride amorphous precipitated were titanium nitride crystals and titanium crystal, it is possible to manufacture a simple process, and the resistance of a wide range of small variations near zero resistance A temperature coefficient can be realized.

According to the method of manufacturing a thin film resistor according to the present invention, a thin film resistor according to the present invention is manufactured in a simple process by using a nitrogen gas as a process gas and using a titanium target and DC magnetron sputtering. can do. Further, by controlling the partial pressure of nitrogen gas, a thin film resistor having a wide range of resistance values can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a resistor thin film of the present invention.

FIG. 2 is a schematic sectional view showing a first example of a method for forming a thin film resistor on a wiring board according to the present invention.

FIG. 3 is a schematic sectional view showing a second example of the method of forming a thin film resistor on a wiring board according to the present invention.

FIG. 4 is a table showing film forming conditions and specific resistance in an example of the thin film resistor of the present invention.

FIG. 5 is an X-ray diffraction pattern of Sample No. 1 manufactured at 25 ° C. and 3 mTorr on a SiO ₂ / Si substrate in an example of the present invention.

FIG. 6 shows an epoxy resin / FR-4 in an example of the present invention.
Sample No. 15 manufactured on a substrate at 25 ° C. and 3 mTorr
3 is an X-ray diffraction pattern of the sample.

FIG. 7 is an X-ray diffraction pattern of Sample No. 13 manufactured at 150 ° C. and 3 mTorr on a SiO ₂ / Si substrate in an example of the present invention.

FIG. 8 shows an epoxy resin / FR-4 in an example of the present invention.
Sample No. 2 manufactured at 150 [℃] and 3 [mTorr] on the substrate
7 is an X-ray diffraction pattern of FIG.

FIG. 9 is an X-ray diffraction pattern of Sample No. 11 manufactured at 25 ° C. and 0.5 mTorr on a SiO ₂ / Si substrate in an example of the present invention.

FIG. 10 shows an epoxy resin / FR in an example of the present invention.
-4 Sample N manufactured on substrate at 25 ° C and 0.5 mTorr
It is an X-ray diffraction pattern of o.25.

FIG. 11 shows a sample No. 1 manufactured at 25 ° C. and 3 mTorr on a SiO ₂ / Si substrate in an example of the present invention.
It is an X-ray diffraction pattern of the thing heat-processed at 1000 [degrees C] for 5 minutes in a nitrogen stream.

FIG. 12 is a schematic sectional view showing a conventional polycrystalline titanium nitride thin film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thin film resistor 12 Titanium nitride amorphous 14 Crystal particle (titanium nitride crystal and titanium crystal) 16 Substrate

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-148732 (JP, A) JP-A-6-306605 (JP, A) JP-A-51-150095 (JP, A) 33759 (JP, A) JP-A-52-3197 (JP, A)

Claims (3)

(57) [Claims] 1. A thin-film resistor made of a composite of at least one titanium nitride amorphous film forming precipitated was titanium nitride crystals and crystalline titanium at by sputtering, nitrogen gas used as a process gas during deposition Control the partial pressure of
By controlling the amount of nitrogen in the composite,
A thin film resistor in which the resistance value of the thin film resistor is changed. 2. Using nitrogen gas as a process gas, using a titanium target and DC magnetron sputtering ,
At least one of a titanium nitride crystal and a titanium crystal;
A method of manufacturing a thin film resistor comprising a composite with titanium nitride amorphous, by controlling the partial pressure of the nitrogen gas at the time of the sputtering, changing the amount of nitrogen in the composite, A method for manufacturing a thin film resistor, comprising changing a resistance value of the thin film resistor. 3. A wiring board in which the thin film resistor according to claim 1 is built in a layer or on a surface.