JPH07335830A - Method of fabricating capacitor comprising tantalum oxide in multilayer interconnection substrate - Google Patents

Abstract

PURPOSE:To reduce a leak current by etching a tantalum oxide layer using a metal mask as a mask to form an upper electrode including the metal mask. CONSTITUTION:A tantalum oxide layer 13 is formed in the thickness of 4000Angstrom on the surface of the substrate 11 exposed by the etching and the underlayer metal layer 12. Next, after the metal mask layer 14 is formed, the photoresist is applied to the surface of the metal mask layer 14 and it is then patterned in the constant shape. Using this metal mask layer as the mask, the metal mask layer 14 is patterned into the predetermined shape. Next, using the metal mask as the mask, Ar gas is used to produce a plasma through the high frequency discharge, the tantalum oxide layer 13 is etched by plasma sputtering. The tantalum oxide layer 13 between electrodes has a thickness of 4000Angstrom and the electrode has an area of 6.75mm<2>. In this case, a leak current can be reduced up to the small value of 5.08X10<-8>A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a tantalum oxide built-in capacitor in a multilayer wiring board, and more particularly to a method of manufacturing a tantalum oxide built-in capacitor in a multilayer wiring board used for communication equipment, computers and the like.

[0002]

2. Description of the Related Art In recent years, with the increasing frequency and speed of electronic devices such as computers, it has become a big problem how to reduce the noise generated in these devices and prevent malfunction of LSIs and the like. There is.

In the noise generated in these electronic devices,
Of particular concern are crosstalk noise caused by the interaction between wirings, ringing noise generated at the rise of signals, reflection noise generated by impedance mismatch in the wiring connection, and opening / closing circuits and devices. Simultaneous switching noise that sometimes occurs.

Among these, the above-mentioned noises can be greatly reduced by making the wiring structure a microstrip structure, for example. On the other hand, in order to reduce the above-mentioned simultaneous switching noise, conventionally, a chip capacitor has been mounted near the LSI. However, even when the chip capacitors are mounted in this way,
Since there is a lead inductance between the LSI and the chip capacitor, there is a limit in reducing the simultaneous switching noise. In consideration of such problems, in recent years, MCM (Multi Chip Mod) suitable for high-speed and high-density mounting
The research and development of incorporating a thin film capacitor in a multi-layer wiring board for ule) is being actively conducted.

As a method of incorporating a thin film capacitor in such a multilayer wiring board, the following method has been conventionally adopted.

FIG. 4 is a cross-sectional view schematically showing each step of a conventional method for producing a tantalum oxide built-in capacitor in a multilayer wiring board.

First, a lower electrode layer 12 is formed on a substrate 11 by a sputtering method, a photoresist 17 is applied to the surface of the lower electrode layer 12 (FIG. 4A), and an exposure process is performed through a mask having a predetermined pattern. After that, the photoresist 17 is patterned into a predetermined shape by a photolithography technique in which development processing is performed (FIG. 4B).

Next, etching is performed using the photoresist 17 as a mask to pattern the lower electrode layer 12 into a predetermined shape, and the photoresist 17 is peeled off (FIG. 4).
(C)).

Next, a tantalum oxide layer 13 is formed on the surfaces of the substrate 11 and the lower electrode layer 12 exposed by the etching by a reactive sputtering method using a Ta target and a gas containing oxygen (FIG. 4 (d)). ).

Next, a photoresist 17 is applied to the surface of the tantalum oxide layer 13 (FIG. 4 (e)), and the photoresist 17 is patterned into a predetermined shape using the photolithography technique described above (FIG. 4 ( f)).

Next, the tantalum oxide layer 13 is wet-etched with hydrofluoric acid using the photoresist 17 as a mask (FIG. 4G), and then the photoresist 17 is peeled off (FIG. 4H).

Next, the upper electrode layer 16 is formed by the sputtering method (FIG. 4 (i)), and the photoresist 17 is applied to the surface thereof (FIG. 4 (j)). Then, the photoresist 17 is formed by using the photolithography technique described above.
Is patterned into a predetermined shape (FIG. 4 (k)), the upper electrode layer 16 is etched to have a predetermined pattern by using the photoresist 17 as a mask, and the photoresist 17 is peeled off. The fabrication of the capacitor is completed (FIG. 4 (l)).

[0013]

In the conventional method for manufacturing a capacitor containing tantalum oxide in a multilayer wiring board as described above, since the tantalum oxide layer 13 is etched into a predetermined pattern, wet etching using high-concentration hydrofluoric acid is performed. Since the law was adopted, there were the following problems.

That is, when wet etching is performed using the high concentration hydrofluoric acid, hydrofluoric acid not only attacks the skin as an acid, but also has a property of penetrating into the skin, which makes handling difficult and dangerous.

Further, during the etching, the photoresist 17 itself is eroded, hydrofluoric acid penetrates into the interface between the tantalum oxide layer 13 and the photoresist 17, and the photoresist 17 is separated from the surface of the tantalum oxide layer 13. This is often the case, and for this reason it is etched to the point where it should not be etched, which is unreliable in the process.

Further, the tantalum oxide layer 13 and the photoresist 1 are removed even if the photoresist 17 is not peeled off.
The tantalum oxide layer 13 is formed by the hydrofluoric acid that has penetrated between
Is eroded, and the leakage current value of the capacitor formed by using the tantalum oxide layer 13 as the capacitor layer tends to increase.

The present invention has been made in view of the above problems, and it is possible to manufacture a capacitor with a built-in tantalum oxide in a multilayer wiring board, which is capable of safely forming a capacitor having a small leak current and excellent reliability. It is intended to provide a way.

[0018]

In order to achieve the above object, a method for manufacturing a tantalum oxide-containing capacitor in a multilayer wiring board according to the present invention comprises a lower layer electrode forming step of forming a lower layer electrode of a predetermined pattern on a substrate, A tantalum oxide layer forming step of forming a tantalum oxide layer in a region including the lower electrode, a metal mask forming step of forming a metal mask having a predetermined pattern on the surface of the tantalum oxide layer, and a plasma gas using the metal mask as a mask. The method is characterized by including an etching step of etching the tantalum oxide layer and an upper layer electrode forming step of forming an upper layer electrode including the metal mask.

The method for producing the tantalum oxide-containing capacitor in the multilayer wiring board according to the present invention will be described in more detail below.

FIG. 1 is a cross-sectional view of a multilayer wiring board schematically showing each step of the method for producing a tantalum oxide built-in capacitor in the multilayer wiring board according to the present invention.

The multilayer wiring board used in the present invention is a board in which wiring layers including a power supply layer and a ground layer are formed in multiple layers in the multilayer wiring board. In the present invention, the multilayer wiring board includes the wiring layers and the like. After manufacturing the substrate, or in the process of manufacturing the multilayer wiring board, a tantalum oxide built-in capacitor is formed in a certain region of the multilayer wiring board.

The lower layer electrode forming step and the tantalum oxide layer forming step can be performed in the same manner as in the above-mentioned conventional method.

That is, the lower electrode layer 12 having a predetermined pattern is formed on the substrate 11 in the same manner as the conventional method (see FIG. 1).
(A) to FIG. 1 (c)), then, the tantalum oxide layer 13 is formed on the surfaces of the substrate 11 and the lower electrode layer 12 exposed by the etching of the lower electrode layer 12 by the reactive sputtering method (FIG. 1). (D)).

The material of the lower electrode layer 12 is, for example, A
1, Ni, etc. are preferable, and the thickness of the lower electrode layer 12 is 0.3.
It is preferably about 0.4 μm. Also, the tantalum oxide layer 1
The thickness of 3 is preferably about 0.2 to 0.8 μm.

Next, in the metal mask forming step, the metal mask layer 14 having a predetermined pattern is formed on the surface of the tantalum oxide layer 13. As a method of forming the metal mask layer, first, a metal such as Al or Ni is formed by a sputtering method. The metal mask layer 14 is formed to a thickness of 0.3 to 0.6 μm,
Photoresist 17 is applied thereon (FIG. 1).
(E)).

Next, the photoresist 17 is patterned into a predetermined shape by a photolithography technique (FIG. 1 (f)), and the photoresist is used as a mask to form a solution of phosphoric acid, nitric acid, acetic acid, and water. Etching is performed to form a metal mask layer 14 having a predetermined pattern (FIG. 1G).

Next, as an etching step, the tantalum oxide layer 13 is etched with the plasma gas 15 using the metal mask layer 14 as a mask (FIG. 1 (h)).

In the present invention, the plasma gas 1 described above is used.
The etching by 5 means that plasma is generated by high frequency discharge or the like, or a magnetic field is simultaneously acted to generate plasma more efficiently or to confine the plasma in a certain region, and the plasma gas 15 generated by these is used. It refers to a method of etching. In addition, the method includes not only high frequency but also a method of generating plasma by discharging using microwave of 2.45 GHz, for example. As an apparatus used when etching is performed with these plasma gases 15, for example, a parallel plate type high frequency and microwave plasma processing apparatus, a magnetic field microwave plasma processing apparatus, and electron cyclotron resonance (ECR) excitation Examples include a device for generating plasma.

When a high frequency etching apparatus is used, it is preferable to use an inert gas such as Ar as an etching gas. When etching is performed by generating plasma by microwaves, oxygen and fluoride gas ( For example, a method using CF ₄ etc.) is preferable.

The conditions of the high frequency etching are, for example, O ₂ gas flow rate: 40 sccm and Ar gas flow rate: 10 sc.
cm, total pressure in the system: 2 mtorr, high frequency: 1
3.56 MHz, high frequency power: 2 kW, substrate temperature: 20 ° C., and the like.

The conditions for the microwave etching are as follows: O ₂ gas flow rate: 360 sccm, CF ₄ : 40 sc
cm, total pressure: 1 torr, microwave power: 1k
W, substrate temperature: 100 ° C., and the like.

Next, in the upper electrode forming step, first, the upper electrode layer 16 including the metal mask is formed to a thickness of 1.5 to 5 by the sputtering method using the same metal as that used for forming the metal mask layer 14. It is formed in the range of 2 μm (see FIG.
(I)), a photoresist 17 is formed on the surface of the upper electrode layer 16 (FIG. 1 (j)).

Next, the photoresist 17 is patterned into a predetermined shape by using a photolithography technique (FIG. 1 (k)), and etching is performed using the photoresist as a mask to form the upper electrode layer 16 of a predetermined pattern. The formation of the capacitor containing tantalum oxide is completed (FIG. 1 (l)).

[0034]

According to the method of manufacturing the tantalum oxide built-in capacitor in the multilayer wiring board having the above-described structure, the lower electrode forming step of forming the lower electrode of a predetermined pattern on the substrate and the tantalum oxide layer in the region including the lower electrode are performed. A tantalum oxide layer forming step to form, a metal mask forming step of forming a metal mask of a predetermined pattern on the surface of the tantalum oxide layer, an etching step of etching the tantalum oxide layer with plasma gas using the metal mask as a mask, Since the upper layer electrode forming step of forming the upper layer electrode including the metal mask is included, in the etching step, etching is performed safely and with higher reliability than the conventional wet method, and in the upper layer electrode forming step. The metal mask can be used as it is as part of the upper layer electrode. Capacitor fabrication process is simplified.

Therefore, according to the above-described method of manufacturing the tantalum oxide built-in capacitor, the product yield is improved as compared with the conventional one, and the manufactured capacitor has a small leak current and high reliability. .

[0036]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of a method of manufacturing a tantalum oxide built-in capacitor in a multilayer wiring board according to the present invention will be described below. Since each step of the present invention has been described in “Means for Solving the Problems” based on the drawings, the method for manufacturing the tantalum oxide-containing capacitor in the present embodiment will be described with the drawings omitted. To do.

Example 1 Using a normal thin film forming apparatus,
First, in the lower layer electrode forming step, a lower electrode layer made of Al was formed to a thickness of 0.4 μm on the substrate by sputtering using an Al metal plate as a target. After that, a photoresist is applied to the surface of the lower electrode layer and patterned into a certain shape by a photolithography technique, and then the photoresist is used as a mask for etching with a solution of a mixture of phosphoric acid, nitric acid, acetic acid, and water. Due to
The lower electrode layer was patterned into a predetermined shape.

Next, in the tantalum oxide layer forming step, a tantalum oxide layer having a thickness of 4000 Å was formed on the surfaces of the substrate and the lower metal layer exposed by the etching by the reactive sputtering method. The tantalum oxide layer was formed by using a Ta plate as a target and using O ₂ for 40 s.
ccm, Ar 10 sccm, total pressure 2 mtorr, high frequency discharge frequency 13.65 MHz, power 2
It was carried out under the conditions of kW and a substrate temperature of 20 ° C.

Next, as a metal mask forming step, a metal mask layer made of Al metal was formed to a thickness of 0.6 μm by a sputtering method. After that, a photoresist is applied to the surface of the metal mask layer and patterned into a certain shape by a photolithography technique. Then, using this photoresist pattern as a mask, a solution of phosphoric acid, nitric acid, acetic acid, and water is mixed. The metal mask layer was patterned into a predetermined shape by etching.

Next, in the etching step, the tantalum oxide layer was etched using the metal mask as a mask, Ar gas as a plasma gas by high-frequency discharge, and sputtering by the plasma.

In this etching process, a parallel plate type plasma etching apparatus was used. FIG. 2 is a cross-sectional view schematically showing the plasma etching apparatus used in this embodiment, and 20 in the figure shows the plasma etching apparatus.

An upper electrode 22 is supported above the processing chamber 21 by a ceramic shield 30, and a seal plate 25 is disposed above the upper electrode 22. An etching gas introducing passage 26 is formed in the center of the seal plate 25, and the etching gas introducing passage 26 is connected to a gas supply source (not shown). A clamp plate 29 for fixing the semiconductor wafer 24 to the lower electrode 23 is attached to the ceramic shield 30, and the clamp plate 29 is made of alumite-treated aluminum to prevent metal contamination. Metal is used. Further, a baffle plate 31 is interposed between the seal plate 25 and the upper electrode 22, and an opening 31a formed in the baffle plate 31 and an opening 32a formed in the upper electrode 22 are provided. Processing room 21
The etching gas is diffused and supplied.

On the other hand, the processing chamber 21 is opposed to the upper electrode 22.
A lower electrode 23 is arranged under a predetermined distance from the lower electrode 23, and a coolant circulation path 28 for circulating cooling water is formed inside the lower electrode 23. A semiconductor wafer 24 is placed on the upper surface of the lower electrode 23. The periphery of the lower electrode 23 is covered with Teflon or ceramic so that the metal other than the lower electrode 23 is not exposed, and an exhaust passage 27 is formed below the outer periphery of the lower electrode 23. A high frequency power source 33 is connected to the upper electrode 22 and the lower electrode 23. When the upper electrode 22 is grounded and the high frequency power is applied to the lower electrode 23, the RIE mode is set, and the lower electrode 23 is grounded. When high frequency power is applied to the electrode 22, the plasma mode is set.

The plasma etching apparatus 20 having the above structure is used.
Was set to the plasma mode, and the substrate 24 having the metal mask of a predetermined shape formed on the tantalum oxide layer by the above step was placed on the lower electrode 23 with the surface to be etched up. Next, the ceramic shield 30 including the upper electrode 22 and the clamp plate 29 is lowered to remove the clamp plate 29.
This substrate 24 was pressed and fixed by. After that, the lower electrode 23 is grounded, and Ar is introduced from the etching gas introducing passage 26.
The gas was supplied into the processing chamber 21, and the degree of vacuum was set to 2 mTorr. Next, from the high frequency power source 33 to the upper electrode 22,
A high-frequency power having a frequency of 13.56 MHz is applied at a power of 2 kW for 60 minutes to turn the etching gas into plasma, and the plasma gas is used to form the substrate 2 on which a metal mask having a predetermined shape is formed on the tantalum oxide layer.
The surface of No. 4 was collided with and etched to form the tantalum oxide layer into a predetermined shape.

Next, the substrate 24 is returned to the thin film forming apparatus, and as the upper layer electrode forming step, sputtering and etching are performed under the same conditions as in the lower layer electrode forming step described above, without removing the metal mask. The upper electrode layer having a predetermined pattern of 1.8 μm was formed to complete the production of the tantalum oxide built-in capacitor.

The tantalum oxide built-in capacitor according to this example thus manufactured has a tantalum oxide layer thickness of 4000 Å between electrodes and an electrode area of 6.75 mm ^2.
And the leak current at this time was a small value of 5.08 × 10 ⁻⁸ A. The leak current was measured by using a pA meter (4140B) manufactured by Yokogawa-Hewlett-Packard Company, and applying a direct current of 25 V for 60 seconds.

[Example 2] Next, as Example 2, a tantalum oxide built-in capacitor was manufactured under the same conditions as in Example 1 except that the thickness of the tantalum oxide layer was 8000 Å, and leakage was performed. The current was measured. The leakage current of the capacitor according to this example was a small value of 9.11 × 10 ^-9 A.

Next, 50 tantalum oxide built-in capacitors were manufactured under the same conditions as in Examples 1 and 2, and a 1 V DC current was applied to the obtained tantalum oxide built-in capacitors.
The product yield was calculated to be 70% or more in both cases of Examples 1 and 2 when the product was passed for a second and the leak current was 1 mA or more was rejected.

[Examples 3 and 4] A tantalum oxide built-in capacitor was manufactured under exactly the same conditions as in Examples 1 and 2 except for the etching step. Therefore, only the etching process will be described here. In addition, here, a tantalum oxide layer having a thickness of 4000 Å is referred to as Example 3 and a tantalum oxide layer having a thickness of 8000 Å is referred to as Example 4.

In this example, as the etching process, an apparatus for generating plasma by ECR excitation was used, and etching was performed using O ₂ and CF ₄ as plasma gas.

FIG. 3 is a sectional view schematically showing an apparatus for generating plasma by ECR excitation used in this embodiment, and 51 in the drawing shows a plasma generating chamber.

The peripheral wall of the plasma generating chamber 51 is constructed in a double structure, a cooling water flow chamber 51a is formed inside the plasma generating chamber 51, and a micro glass sealed by a quartz glass plate 51b at the center of the upper wall. A wave introduction port 51c is formed, and a plasma extraction window 51d is formed at a position facing the microwave introduction port 51c in the center of the lower wall. The microwave inlet 51c is connected to one end of a waveguide 52 whose other end is connected to a microwave oscillator (not shown), and a sample chamber 53 is provided so as to face the plasma extraction window 51d. Further, an exciting coil 54 is arranged concentrically with the plasma generation chamber 51 and the waveguide 52 connected to the plasma generation chamber 51 so as to surround them.

On the other hand, in the sample chamber 53, a sample table 57 for mounting a sample such as a ceramic substrate 55 is arranged at a position facing the plasma drawing window 51d. An exhaust port 53a connected to an exhaust device (not shown) is formed on the lower wall of the sample chamber 53.

In the figure, 51g indicates a reaction gas supply system connected to the plasma generation chamber 51, and 53g indicates a sample chamber 53.
Shows a reaction gas supply system connected to
Indicates a cooling water supply system and a cooling water supply system.

The sample table 5 of the above-configured apparatus
7, a substrate 55 on which a metal mask having a predetermined shape is formed on the tantalum oxide layer is placed, and the reaction gas supply systems 51g and 53g are used to supply O in the plasma generation chamber 51 and the sample chamber 53.
₂ for 360 sccm, CF ₄ for 40 sccm, total pressure 1t
orr, and a magnetic field necessary for electron cyclotron resonance excitation is formed by the exciting coil 54, and a microwave with a frequency of 2.45 GHz with a power of 1 kW is introduced into the plasma generation chamber 51 through the microwave introduction port 51c to generate plasma. The chamber 51 was used as a cavity resonator to resonantly excite the gas to generate plasma. Then, the generated plasma was projected around the substrate 55 in the sample chamber 53, and the tantalum oxide layer was etched to be patterned into a predetermined shape.

The leakage current of the tantalum oxide built-in capacitor manufactured by the method according to this embodiment is 3.04 × 10 ⁻¹⁰ A in the case of the third embodiment, and is 1.40 in the case of the fourth embodiment.
The value was 03 × 10 ⁻¹⁰ A, which was even smaller than that in the cases of Examples 1 and 2.

When the product yields of Examples 3 and 4 were measured in the same manner as in Examples 1 and 2, the product yields were both 80% or more.

[Comparative Examples 1 and 2] A tantalum oxide built-in capacitor was manufactured under exactly the same conditions as in Examples 1 and 2 except for the etching step. Therefore, in this comparative example, only the etching process will be described. A tantalum oxide layer having a thickness of 4000Å is referred to as Comparative Example 1, and a tantalum oxide layer having a thickness of 8000Å is referred to as Comparative Example 2.

In the etching step, a substrate having a tantalum oxide layer on the surface of which a metal mask having a predetermined pattern was formed was immersed in a hydrofluoric acid solution having a concentration of 20% by weight for 15 seconds for etching.

The leakage current of the obtained capacitor containing tantalum oxide was 9.21 × 10 ⁻⁸ A in the case of Comparative Example 1 and 3.12 × 10 ⁻⁸ A in the case of Comparative Example 2. In comparison with the case where the tantalum oxide layer had the same thickness in No. 4, the leakage current value was about twice as large in any case.

When the product yields of Comparative Examples 1 and 2 were measured in the same manner as in Examples 1 and 2, the product yield was 50% or less, which is a low value as compared with Examples 1 to 4. It was

As described above, in the method of manufacturing the tantalum oxide built-in capacitor in the multilayer wiring substrate according to the embodiment, the lower layer electrode forming step of forming the lower layer electrode made of Al in a predetermined pattern on the substrate is performed. And a step of forming a tantalum oxide layer in a region including the lower electrode, a step of forming a metal mask of Al having a predetermined pattern on the surface of the tantalum oxide layer, and a step of masking the metal mask. And an etching step of etching the tantalum oxide layer with a plasma gas generated using Ar or a plasma gas generated using O ₂ and CF _4, and an upper layer electrode made of Al including the metal mask is formed. Since it includes an upper layer electrode forming step, the etching step is safer than the conventional wet method. In addition, it is possible to perform etching with high reliability, and in the upper electrode forming step,
Since the metal mask can be used as it is as a part of the upper electrode, the manufacturing process of the capacitor can be simplified.

Therefore, in the method of manufacturing the tantalum oxide built-in capacitor according to the embodiment, the product yield can be improved to 70% or more as compared with the conventional product yield (50% or less), and the leakage It is possible to provide a highly reliable capacitor having a small current.

[0064]

As described above in detail, in the method of manufacturing a tantalum oxide built-in capacitor in a multilayer wiring board according to the present invention, a lower layer electrode forming step of forming a lower layer electrode of a predetermined pattern on the substrate, and a lower layer electrode A tantalum oxide layer forming step of forming a tantalum oxide layer in a region including a metal mask forming step of forming a metal mask having a predetermined pattern on the surface of the tantalum oxide layer; Since the method includes an etching step of etching a layer and an upper electrode forming step of forming an upper electrode including the metal mask, the etching step is safer and more reliable than the conventional wet method. In addition, in the upper electrode forming step, the metal mask is used as it is for the upper electrode. Since can be used as part, it is possible to simplify the manufacturing process of the capacitor.

Therefore, in the method of manufacturing a tantalum oxide-containing capacitor according to the present invention, the product yield can be improved as compared with the conventional product, and a capacitor having a small leak current and high reliability can be provided. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing each step of a manufacturing method of a tantalum oxide built-in capacitor in a multilayer wiring board according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a plasma etching apparatus used in an example.

FIG. 3 is a cross-sectional view schematically showing an apparatus for generating plasma by ECR excitation used in an example.

FIG. 4 is a cross-sectional view schematically showing each step of a method for manufacturing a tantalum oxide built-in capacitor in a conventional multilayer wiring board.

[Explanation of symbols]

 11 Substrate 12 Lower Electrode Layer 13 Tantalum Oxide Layer 14 Metal Mask Layer 15 Plasma Gas 16 Upper Electrode Layer

Claims (1)

[Claims] 1. A lower electrode forming step of forming a lower electrode of a predetermined pattern on a substrate, a tantalum oxide layer forming step of forming a tantalum oxide layer in a region including the lower electrode, and a predetermined surface of the tantalum oxide layer. A metal mask forming step of forming a patterned metal mask, an etching step of etching the tantalum oxide layer with a plasma gas using the metal mask as a mask, and an upper layer electrode forming step of forming an upper layer electrode including the metal mask A method of manufacturing a tantalum oxide-containing capacitor in a multilayer wiring board, comprising: