JPH07258841A - Film forming method of thin-film resistor and film forming device therefor - Google Patents

Abstract

PURPOSE:To maintain a specified film compsn. and to form thin-film resistor which does not generate a surface resistance distribution by impressing positive potential of frequencies of a specific range in the form of pulses to a target of negative potential in film formation. CONSTITUTION:A Ta-SiO2 target 7 and an insulator substrate 8 are mounted in a vacuum treating chamber 1 respectively. After a prescribed pressure is maintained in this vacuum treating chamber 1, DC electric power is impressed from a DC power source 9 to the target 7 and the positive potential is impressed in the form of pulses from a pulse unit 10 to the target 7 of the negative potential while the frequency is changed to 5 to 400kHz to generate DC discharge. A substrate holder 6 is moved along the target 7 in this state and the insulator substrate 8 mounted at the substrate holder 6 is subjected to film formation by the target material 7 flying via the aperture of a mask 11, by which the thin-film resistors consisting of Ta-SiO2 are formed on the substrate 8. The charge is compensated and the generation of the abnormal discharge is prevented by periodically impressing the positive potential to the negative potential.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film resistor and an apparatus for forming the same. More specifically, the thin film resistor is formed by sputtering a target made of a mixture of metal and SiO ₂ in an argon gas atmosphere. The present invention relates to a method for forming a film on a body and an apparatus for forming the film.

[0002]

2. Description of the Related Art Resistors, which have been widely used as resistance films for heat-sensitive recording parts for printing such as facsimiles and word processors and surface-mounted electronic parts, have been widely used in the past. There is also a thin film type made by the vapor deposition method.

As output elements for the above-mentioned OA equipment and video printers, Ta-SiO ₂ and Cr-S are used.
A thin film type resistor such as iO ₂ (hereinafter referred to as a thin film resistor) is widely used. For example, in order to obtain clear characters for printing, it is required that the variation in the resistance value of each thin film resistor be several percent or less, and especially a line printer that prints one line of A4 size at once such as a facsimile or word processor. Further, in a video printer or the like which is required to display gradation, a thin film resistor having a better resistance value distribution is required as compared with other devices.

In addition, conventional Ta-SiO ₂ , Cr-Si
The thin film resistor of O ₂ , Nb-SiO ₂ or Zr-SiO ₂ is generally formed by a sputtering method using a target made of a mixture of metal and SiO ₂ . Even if the composition of the metal of Ta, Cr, Nb or Zr and SiO ₂ changes subtly, it has a great effect on the resistance value of the thin film resistor formed on the substrate, so the vapor deposition method is not used,
A stable sputtering method for film formation is exclusively used.

However, in the DC magnetron sputtering method with stable discharge, charge accumulation occurs during film formation in an insulator such as SiO ₂ contained in the target and abnormal discharge occurs, so that the RF sputtering method is exclusively used. ing.

Also, in the RF sputtering method,
In the RF magnetron sputtering method using a magnet, the resistance value of the thin film resistor formed on the substrate varies, and the resistance value distribution is large. Therefore, the RF sputtering method without a magnet having a smaller resistance value distribution is used. Used as a passive choice.

An example of a conventional thin film resistor film forming apparatus is shown in FIGS. 1 and 2 of the accompanying drawings. In the figure, a indicates a vacuum processing chamber.

The vacuum processing chamber a has a sputtering gas inlet b and a vacuum exhaust port c such as a vacuum pump. Further, in the vacuum processing chamber a, a sputtering cathode d and a substrate holder f which is supported on a carrying roller e extending parallel to the sputtering cathode d and can be carried along the carrying roller e are arranged to face each other. ing.

A target g and an insulator substrate h to be deposited are mounted on the facing surfaces of the sputtering cathode d and the substrate holder f, respectively. Further, the sputtering cathode d is connected to a high frequency power source i outside the vacuum processing chamber a and is configured to be applied with high frequency power.

Further, an opening mask j for controlling the film thickness distribution is arranged between the sputtering cathode d and the substrate holder f at a position close to the substrate holder f, and this opening mask j is formed by sputtering as shown in FIG. It has an opening k formed in accordance with the size and level of the target g mounted on the cathode d. Therefore, the insulating substrate h on the substrate holder f moves while looking through the target g through the opening j.

In the operation of the film forming apparatus having such a structure, a sputtering gas such as argon gas is introduced into the vacuum processing chamber a through the sputtering gas introduction port b, and is exhausted through the vacuum exhaust port c. The pressure in the vacuum processing chamber a is maintained at an arbitrary value in the range of 10 ⁻² Torr to 10 ⁻³ Torr. After the inside of the vacuum processing chamber a is maintained at a predetermined pressure in this way, RF power is supplied from the RF power supply i to the target g mounted on the sputtering cathode d, whereby R
F discharge is generated.

In this state, the substrate holder f is continuously transported along the target g by the transport roller e. As a result, the target material is deposited on the insulating substrate h mounted on the substrate holder f through the opening k of the opening mask j.

While transporting a 400 mm square glass substrate h at a constant speed of 30 mm / min using the apparatus shown in FIGS.
A sheet resistance value in the substrate transport direction of the thin film resistor formed by continuously forming a film was measured by applying a sputtering power of 5 KW to the sputtering cathode d, and the resistance value distribution is shown in FIG. As is clear from FIG. 3, it is recognized that the sheet resistance is reduced at the front and rear portions of the substrate, and a distribution of about 10% is generated.

[0014]

By the way, in order to improve the resistance value distribution of such a thin film resistor, in the prior art,
In order to control the film composition and the specific resistance of the film, the method of increasing the carrier speed of the substrate at the front and rear of the substrate where the surface resistance is expected to decrease or reducing the high frequency power supplied to the cathode is adopted. Without changing the film thickness,
The apparent top surface resistance was made uniform.

However, the film composition always changes depending on the gas pressure and the residual impurity gas composition. Therefore, it is difficult to obtain a uniform sheet resistance distribution with good reproducibility by controlling the film thickness. Further, in order to change the substrate transfer speed and the electric power supplied to the cathode, not only complicated programming is required, but also control is difficult.

RF sputtering using a high frequency power source can form a film without abnormal discharge for a long time, but has a problem that the film forming speed is slow.

Therefore, the present invention solves the problems associated with the film formation of a conventional thin film resistor, maintains a uniform film composition, and does not cause a sheet resistance distribution, and a method for forming the same. It is an object to provide a membrane device.

[0018]

According to the method of forming a thin film resistor of the present invention, a thin film resistor is sputtered on a substrate by sputtering a target made of a mixture of metal and SiO _{2 in} an argon gas atmosphere by a DC sputtering method. In the film forming method for forming a body, a positive potential is applied to the target of negative potential at a frequency of 5
It is characterized in that the sputtering is performed while applying a pulse shape at a frequency of 400 kHz.

The target made of a mixture of the metal and SiO ₂ is Ta-SiO ₂ , Nb-SiO ₂ , Cr.
-SiO _2, may be as either of Zr-SiO _2.

In the thin film resistor film forming apparatus of the present invention, a target made of a mixture of a substrate and a metal and SiO ₂ is provided to face each other in a vacuum processing chamber, and the target is sputtered by a DC sputtering method in an argon gas atmosphere. In the film forming apparatus for forming a thin film resistor on a substrate by performing the above, a power source for applying a positive potential to a negative potential in a pulse shape at a frequency of 5 to 400 kHz is connected to the target.

The target made of a mixture of the metal and SiO ₂ is Ta-SiO ₂ , Nb-SiO ₂ , Cr.
-SiO _2, may be as either of Zr-SiO _2.

[0022]

When a target made of a mixture of metal and SiO ₂ is applied with DC power from a DC power supply in an argon gas atmosphere and sputtering is performed, the target is sputtered and a thin film of a resistor is formed on the substrate.

When sputtering is continuously performed for a long time,
The plus (+) ions of argon gas are accumulated on the insulator contained in the target made of a mixture of metal and SiO ₂ , the insulator deposited on the target and the high resistance film. The electric charge of the positive (+) ions causes arc discharge between the target, the erosion part, the ground electrode, etc., which causes abnormal discharge.

In this abnormal discharge, the target material is an insulator,
The high-resistance film becomes particulate and scatters, adheres to the substrate, and becomes a defect in the thin film of the resistor formed.

When DC power is applied to the target to perform DC sputtering, if a positive potential is applied in a pulse shape to the target having a negative potential at a constant frequency, electrons in the plasma are attracted by the positive potential and contained in the target. Insulators, insulators accumulated on the target and positive (+) ions accumulated on the high resistance film are neutralized to prevent abnormal discharge due to arc discharge.

At that time, the positive potential applied to the target is effective even if the application time is extremely short compared with the time of the negative potential, so that the film formation rate is reduced by several percent from the film formation rate by only the direct current. And the deposition rate is high frequency 1
Higher than the film formation rate during 3.56 MHz sputtering.

Further, as compared with the RF sputtering method,
Since the plasma state is stable in the DC sputtering method, the change in the plasma potential due to the transfer of the substrate is small, and the resistance value distribution of the thin film resistor formed on the substrate caused by the change in the potential should be small enough to be ignored. Is possible.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 4 and 5 show an example of a film forming apparatus for carrying out the method of forming a thin film resistor according to the present invention.
In the figure, 1 indicates a vacuum processing chamber.

The vacuum processing chamber 1 is provided with a sputtering gas introduction port 2 and a vacuum exhaust port 3. Further, in the vacuum processing chamber 1, a sputtering cathode 4 and a substrate holder 6 supported on a transport roller 5 extending parallel to the sputtering cathode 4 and capable of being transported along the transport roller 5 are arranged to face each other. ing. Sputtering cathode 4
A target 7 made of a mixture of metal and SiO ₂ and an insulating substrate 8 to be deposited are mounted on the opposing surface side of the substrate holder 6, respectively.

A DC power supply 9 is connected to the sputtering cathode 4 via a pulse unit 10, and the pulse unit 10 is adjusted to apply a negative potential and a positive potential to the target 7 in a pulsed manner at a predetermined frequency. I did it.

An opening mask 11 for controlling the film thickness distribution is arranged at a position near the substrate holder 6 between the sputtering cathode 4 and the substrate holder 6, and this opening mask 11 is formed on the sputtering cathode 4 as shown in FIG. It has an opening 12 dimensioned to the size and level of the mounted target 7. Therefore, the insulating substrate 8 on the substrate holder 6 moves while looking into the target 7 through the opening 12.

Further, a magnet 13 for a magnetron grasshopper is arranged on the back side of the sputtering cathode 4 so that a magnetic field necessary for magnetron sputtering is applied to the surface of the target 7 attached to the sputtering cathode 4.

Next, a specific embodiment of the film forming method of the present invention will be described with reference to FIGS. 4 and 5.

Example 1 Ta-Si was used as a target 7 on the sputtering cathode 4 in the vacuum processing chamber 1 of the film forming apparatus shown in FIGS. 4 and 5.
An O ₂ target was mounted on the substrate holder 6, and an alumina insulating substrate was mounted on the substrate holder 6 as the substrate 8.

Subsequently, argon (Ar) gas is introduced as a sputtering gas into the vacuum processing chamber 1 through the sputtering gas inlet 2 and exhausted through the vacuum exhaust port 3, so that the pressure in the vacuum processing chamber 1 becomes about 10. It is maintained at an arbitrary pressure from ^-2 torr to 10 ^-3 torr. After the inside of the vacuum processing chamber 1 is maintained at a predetermined pressure in this way, DC power of 1.5 kW is applied to the target 7 from the DC power source 9 by the DC magnetron sputtering method, and the target 7 of negative potential is applied.
Then, a positive potential was applied in pulse form (see FIG. 9) while changing the frequency from 2 kHz to 400 kHz by the pulse unit 10 to generate DC discharge.

The application time of the positive potential applied in a pulsed manner to the target of the negative potential is 10 μsec when the frequency is up to 10 kHz, and 100 times when the frequency exceeds 10 kHz.
5 kHz for frequencies up to 100 kHz
When z was exceeded, it was set to 1 μsec. The magnetic field strength at the time of DC McNetron sputtering was set to 250 Oe.

In this state, the substrate holder 6 is continuously transported by the transport roller 5 along the target 7. As a result, the insulating substrate 8 mounted on the substrate holder 6 is formed into a film by the target 7 material coming in through the opening 12 of the opening mask 11, and the thickness of Ta-SiO ₂ is formed on the insulating substrate 8. A thin film resistor having a thickness of 300Å was formed.

Then, the number of abnormal discharges and the film formation rate were measured for each frequency of the positive potential applied to the target 7 of the negative potential. The obtained measurement result is shown in FIG.

The resistance value distribution of the thin film resistor formed on the substrate in the substrate transport direction was measured for each frequency, and the results are shown in FIG.

As is apparent from FIG. 6, the number of abnormal discharges decreases with an increase in the frequency of the positive potential applied to the negative potential. The number of abnormal discharges becomes almost zero at a frequency of 5 kHz or higher, and becomes positive at frequencies higher than this. It can be seen that if the potential is applied to a negative potential, abnormal discharge does not occur.

When the frequency of the positive potential applied to the negative potential is 400 kHz (time 1 μsec), the deposition rate is about 10 times that of the conventional RF sputtering method without using a magnet, and the RF magnetron using the magnet is used. The film formation rate is the same as the sputtering method.

The film forming rate in the frequency range of 5 to 400 kHz is higher than that of the RF magnetron sputtering method using a magnet.

When sputtering a Ta-SiO ₂ target by a DC sputtering method in an argon gas atmosphere, if a negative potential is continuously discharged to the target by a conventional DC power source, an insulator such as SiO ₂ contained in the target is included. Alternatively, positive (+) charges are accumulated on the high-resistance deposit, arc discharge is generated between the target and the ground electrode, and the charges are discharged. As a result, abnormal discharge occurs, but in the present invention, as shown in FIG. 9, by applying a positive potential to a negative potential periodically, that is, at a constant frequency, the above-mentioned charges are compensated for and the abnormal discharge occurs. To prevent the occurrence of.

As is clear from FIG. 7, the resistance value distribution in the carrying direction is about 1% or less up to a frequency of 100 kHz, but the distribution width gradually increases at a frequency of 100 kHz or more. In addition, the film forming speed is R using a magnet.
The same frequency as the F magnetron sputtering method 400k
The distribution is 1% or less even at Hz.

Using the film forming apparatus of the present invention, while transporting a 400 mm square glass substrate at a constant speed of 600 mm / min.
FIG. 8 shows a resistance value distribution of the thin film resistor when the film is formed at a sputtering power of 1.5 kW and a frequency of 10 kHz.

As is clear from FIG. 8, the resistance value distribution of the thin film resistor formed by the DC magnetron sputtering method of the present invention is the resistance value distribution of the thin film resistor formed by the conventional RF sputtering method ( It can be seen that the shape of the resistance value distribution is very flat and good as compared with (see FIG. 3).

Therefore, it was confirmed that the frequency range of the positive potential applied to the negative potential target is 5 to 400 kHz.

Example 2 C was used as a target 7 made of a mixture of metal and SiO _2.
A thin film resistor made of Cr-SiO ₂ and having a thickness of 300 Å was formed on the insulating substrate 8 by the DC magnetron sputtering method in the same manner as in Example 1 except that r-SiO ₂ was used.

As a result, no abnormal discharge was observed during sputtering when the positive potential applied to the negative potential had a frequency of 5 kHz or higher. Further, the resistance value distribution of the thin film resistor was flat as in Example 1 and showed a good distribution state.

Example 3 N was used as the target 7 made of a mixture of metal and SiO _2.
A thin film resistor made of Nb-SiO ₂ and having a thickness of 300 Å was formed on the insulating substrate 8 by the DC magnetron sputtering method in the same manner as in Example 1 except that b-SiO ₂ was used.

As a result, no abnormal discharge was observed during the sputtering when the positive potential applied to the negative potential had a frequency of 5 kHz or higher. Further, the resistance value distribution of the thin film resistor was flat as in Example 1 and showed a good distribution state.

Example 4 Z was used as a target 7 composed of a mixture of metal and SiO _2.
A thin film resistor made of Zr-SiO ₂ and having a thickness of 300 Å was formed on the insulating substrate 8 by the DC magnetron sputtering method in the same manner as in Example 1 except that r-SiO ₂ was used.

As a result, when the positive potential applied to the negative potential had a frequency of 5 kHz or higher, no abnormal discharge was observed during sputtering. Further, the resistance value distribution of the thin film resistor was flat as in Example 1 and showed a good distribution state.

Although the apparatus shown in FIGS. 4 and 5 is a combination of a DC power source and a pulse unit as a power source apparatus for applying a positive potential in a pulse shape to a negative potential at a constant frequency, the apparatus is not limited to this. An integrated power supply device in which a positive potential is periodically (pulse-likely) applied to a negative potential as shown in FIG. 9 may be used.

Although the apparatus provided with one target is used in the above embodiment, a vertical double-sided sputtering apparatus having one or more sets of facing targets may be used.

Further, in the above-mentioned embodiment, the pass-by type sputtering apparatus is used, in which the substrate is moved on the target and the film is formed at one time. The sputtering may be performed using a sputtering apparatus or a single-wafer type sputtering apparatus that fixes a substrate and forms a film.

Further, although the film formation was carried out in an argon gas atmosphere in the above-mentioned embodiment, the film formation was carried out not only with the argon (Ar) gas but also with the oxygen (O ₂ ) gas and the nitrogen (N ₂ ) gas in the argon (Ar) gas. ₂ ) Gas, carbon monoxide (CO) gas, carbon dioxide (CO ₂ ) gas or other reactive gas may be mixed with argon gas (Ar) in an amount of 5 to 75% mixed gas atmosphere.

[0059]

According to the method of forming a thin film resistor of the present invention, a negative potential metal and SiO ₂ are added in an argon gas atmosphere.
Since sputtering was performed while applying a positive potential in a pulse shape at a constant frequency to the target composed of a mixture of the above, the charge of positive ions accumulated on the insulator and high resistance film deposited on the target during sputtering. Therefore, there is an effect that a uniform thin film resistor having no defects can be formed on the substrate at a high film forming rate for a long time while preventing abnormal discharge due to arc discharge.

Further, in DC sputtering, the density of states of plasma is stable, so that the change in plasma potential due to the substrate transfer is small, and the resistance value distribution in the substrate caused by the change in potential hardly occurs. As a result, it is possible to provide a thin film resistor with less variation in resistance value,
Therefore, the film forming method of the present invention can form a high-quality thin film resistor for an output device such as an OA device or a video printer with a high yield and at a high film forming rate.

Further, since the plasma state is a stable DC discharge, the plasma state can be kept constant with respect to the continuously moving substrate. It is possible to form a thin film resistor on a substrate that continuously moves without adjusting the input power to the sputtering cathode or the sputtering cathode without variation in the resistance value.

In the thin film resistor film forming apparatus of the present invention, a power source for applying a positive potential in a pulsed manner at a constant frequency is connected to a target made of a mixture of a negative potential metal and SiO _2. Therefore, a thin film resistor film forming apparatus capable of forming a uniform thin film resistor free of defects on a substrate at a high film forming rate for a long time while preventing the occurrence of abnormal discharge due to arc discharge. Has the effect of providing.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional side view of an example of a conventional thin film resistor film forming apparatus,

2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a distribution diagram of a sheet resistance value of a thin film resistor in a substrate transport direction during film formation using a conventional apparatus,

FIG. 4 is a schematic cross-sectional side view of an example of a thin film resistor film forming apparatus of the present invention;

5 is a sectional view taken along line VV of FIG.

FIG. 6 is a characteristic showing the relationship between the frequency of a positive potential applied to a negative potential target during film formation and the number of abnormal discharges, and the relationship between the frequency and the film formation rate in one example of the film forming method of the present invention. Diagram,

FIG. 7 shows a frequency distribution of a positive potential applied to a target having a negative potential during film formation and a sheet resistance distribution of a thin film resistor formed on the substrate in a substrate transport direction in one example of the film forming method of the present invention. Characteristic diagram showing the relationship with

FIG. 8 is a distribution diagram of a sheet resistance value of a thin film resistor in a substrate transport direction during film formation in an example of a film forming method of the present invention,

9 is a model diagram of a potential applied to a target by the apparatus of FIGS. 4 and 5. FIG.

[Explanation of Codes] 1 vacuum processing chamber, 2 sputtering gas inlet, 3 vacuum outlet, 4 sputtering cathode, 5 transfer rollers, 6 substrate holder,
7 target, 8 substrate, 9 DC power supply, 10 pulse unit, 11 aperture mask, 12 aperture, 13 magnet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kafumi Ota 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Supermaterials (72) Inventor Hisami Nakamura 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Prefecture Japan Vacuum Technology Co., Ltd. Chiba Institute for Super Materials

Claims (4)

[Claims] 1. In a film forming method for forming a thin film resistor on a substrate by sputtering a target made of a mixture of metal and SiO ₂ by a direct current sputtering method in an argon gas atmosphere, a positive potential is applied to the target having a negative potential. A method of forming a thin film resistor, which comprises applying a pulse while applying an electric potential in a pulse shape at a frequency of 5 to 400 kHz. _2. A target made of a mixture of the metal and SiO ₂ is Ta-SiO ₂ , Nb-SiO ₂ , Cr-S.
The thin film resistor film forming method according to claim 1, wherein the film forming method is any one of iO ₂ and Zr-SiO ₂ . 3. A vacuum treatment chamber is provided with a substrate and a target made of a mixture of metal and SiO ₂ facing each other, and the target is sputtered by a direct current sputtering method in an argon gas atmosphere to form a thin film resistor on the substrate. In the film forming apparatus for forming, a positive potential is applied to a negative potential at a frequency of 5 to 400 k.
A film forming apparatus for a thin film resistor, characterized in that a power source for applying a pulse at Hz is connected to the target. 4. The target made of a mixture of the metal and SiO ₂ is Ta-SiO ₂ , Nb-SiO ₂ , Cr-S.
4. The thin film resistor film forming apparatus according to claim 3, wherein the film forming device is one of iO ₂ and Zr—SiO ₂ .