JPH08236705A - Dielectric materil of thin film capacitor for multichip module - Google Patents

Abstract

PURPOSE: To provide a ceramic dielectric material having high dielectric constant in operating temperature range, which is suited to a thin film capacitor for MCM. CONSTITUTION: A dielectric material of a thin film capacitor for MCM is composed by using Ba(Ti1-x Zrx )O3 by cosputtering BaTiO3 and BaZrO3 in the range of high frequency power ratio 9:1 to 7:3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric material for a thin film capacitor used in a multi-chip module (hereinafter abbreviated as MCM).

Information processing apparatuses have been increased in capacity because of the need to process a large amount of information quickly, and LSIs and VLSIs have been developed.
MCM in which integrated circuits such as
Is being put to practical use.

Here, the ceramic multi-layer circuit board constituting the MCM processes high speed signals on the upper side of the board, and
Since integrated circuits such as LSI and VLSI that generate a great amount of heat are arranged and mounted in a matrix, a ceramic substrate having excellent heat resistance and thermal conductivity such as aluminum nitride (AlN) is used as a substrate material.

As a method for producing a multilayer circuit board, a small amount of a sintering aid, a binder and a dispersant are added to a ceramic powder such as AlN and well kneaded to form a slurry, and this slurry is prepared by a doctor blade method. After forming a green sheet and punching a via hole, a tungsten (W) paste is printed on this green sheet to form a pattern of a power supply line, an earth line, etc., and after laminating and integrating, a nitrogen (N) ₂ ) Degreasing in an inert gas atmosphere such as gas, heating to a high temperature and sintering to make a multilayer circuit board connected by vias.

Next, after patterning a large number of fine signal lines on such a substrate by using a thin film forming technique such as vacuum deposition or sputtering and a photo-etching technique (photolithography), a polyimide or polyimide Silicon dioxide (SiO ₂ )
An MCM is formed by forming an interlayer insulating layer using a heat-resistant material such as, mounting an integrated circuit such as LSI or VLSI on the insulating layer, and connecting the circuit to the signal line through a via.

The present invention relates to thin film capacitors used in such MCMs.

[0007]

2. Description of the Related Art As mentioned above, an MCM is formed by arranging semiconductor integrated circuits (hereinafter abbreviated as LSI) such as LSI and VLSI in a matrix on a multi-layer circuit board made of AlN or the like. When a large number of transistors forming an LSI simultaneously perform a switching operation, the power supply voltage fluctuates due to the influence of the inductance of the wiring, and the high-speed noise generated at this time causes the LSI
Has a problem that it malfunctions.

Therefore, as a countermeasure against this, a chip capacitor made of ceramic is arranged near the LSI. However, this chip capacitor does not function sufficiently as a so-called decoupling capacitor due to the inductance of the wiring that connects the chip capacitor and the LSI, and the chip capacitor to be mounted requires a considerable area. Therefore, the presence of this chip capacitor hinders the miniaturization of the MCM.

[0009]

At present, a ceramic chip capacitor is used as a decoupling capacitor used in MCM. However, due to the inductance of the wiring connecting this chip capacitor and LSI,
Switching noise cannot be sufficiently removed, and on the other hand, the chip capacitor is mounted on the same substrate surface as the LSI is mounted, which causes a problem that miniaturization of the MCM is hindered.

Therefore, as a solution to this problem, the mounting of the chip capacitor is eliminated, and instead, a thin film capacitor is formed on the signal layer in which the signal line is patterned, and the LSI is arranged on the signal layer through an interlayer insulating layer, thus increasing the area. It is effective without taking.

Now, until now, a thin film has been formed as a high dielectric constant material.
The material used for strontium titanate
Mu (Sr Ti O₃), Barium strontium titanate
Mu [Ba (Ti_1-xSr_x) O₃], Zirconate titanate
Lead [Pb (Ti_1-xZr_x) O ₃Abbreviation PZT] etc.
It However, Sr Ti O₃And Ba (Ti_1-xSr_x) O₃To
As a result, it has a low dielectric constant and is formed by sputtering.
In this case, there is a problem that the film forming speed is slow.

The signal line formed on the interlayer insulating layer is made of copper (Cu). Since the wiring pattern is formed in a reducing atmosphere, PZT containing Pb having a high vapor pressure is used. Is not suitable for use. For these reasons, the use of conventional ceramic materials for capacitors is not appropriate, and it is an issue to put into practical use ceramic materials to replace them.

[0013]

SUMMARY OF THE INVENTION The above problem is material barium titanate forming the dielectric thin film capacitor MCM (Ba Ti O ₃₎ and barium zirconate (Ba Zr O
₃ ) Barium zirconate titanate [Ba (Ti _1-x Zr _x ) O ₃ ] obtained by dual sputtering of ₃ ), and the high frequency power ratio in that case is 9: 1 to 7: 3 The problem can be solved by forming a thin film capacitor for MCM using.

[0014]

[Function] A thin film capacitor for MCM needs to be able to realize a large capacitance in a small area, and the necessary conditions for this are a large dielectric constant (ε), a small dielectric loss (tan δ), and heat resistance. Is excellent, and from this viewpoint, Ba Ti O ₃
Ferroelectric ceramic materials such as are suitable and are also used as dielectrics for thin film capacitors.

That is, Ba Ti O₃Target the sintered body
And about 1 Pascal oxygen to prevent decomposition of the ingredients
(O₂) By performing the sputtering process in the atmosphere, Ba
Ti O ₃A thin film can be formed.

However, the Curie point of Ba 2 Ti ₃ O ₃ crystal is 120 ° C., and in the vicinity of this Curie temperature, the dielectric constant (ε) shows a high value as high as 12000. It has the property of decreasing to. That is, Ba Ti O ₃ is a perovskite (Perovs
kite) structure, and the cubic system (Cubi
c), but at temperatures below that, tetragonal (Tetragonal)
Therefore, the dielectric constant (ε) changes with the change of the crystal system because it changes to the orthorhombic system at around 0 ° C and changes to the rhombohedral system at -80 ° C or less.

Therefore, in a chip capacitor mainly composed of Ba 2 Ti ₃ O ₃ , oxides of various elements are added in order to realize a large dielectric constant (ε) at room temperature,
Curie points are being lowered to around room temperature.

That is, when a raw material powder such as titanium oxide (TiO ₂ ) or barium carbonate (Ba CO ₃ ) is mixed, oxides of various elements are added, and the mixture is kneaded to form a compact at a high temperature. By firing, ceramics with different Curie points and temperature coefficients are realized.

On the other hand, as a method of lowering the Curie point, the inventors of the present invention simultaneously sputter (binary sputter) Ba Zr O ₃ having a perovskite structure similar to Ba Ti O ₃ to form Ba (Ti _1-x Zr). By forming a thin film having a structure of _x ) O ₃ and thereby realizing a dielectric material for a capacitor having a larger dielectric constant (ε) than Ba Ti O _{3 at} room temperature.

That is, compounds having different composition ratios can be produced by performing sputtering while changing the power ratio to the target. In this case, Ba (Ti _1-x Zr
_x ) O ₃ , where x can be represented by the substitution amount of Zr,
Ti of B site having a perovskite structure is replaced by Zr, and the Curie point is lowered accordingly.

[0021] The present invention is Ba Ti O ₃ target and Ba Z
r O ₃ RF power ratio to the target 9: 1 to 7:
By performing a dual sputtering as No. ₃ , a ceramic showing a dielectric constant larger than that of BaTiO _{3 at} room temperature is obtained.

The dielectric constant of the dielectric thin film obtained by sputtering is orders of magnitude smaller than that of the bulk, but it is difficult to keep the substrate temperature sufficiently high during sputtering. , Therefore the crystal grains are small,
This is because a sufficient domain structure cannot be taken.

From the result of X-ray diffraction, it was found that the preferential plane orientation of the Ba (Ti _1-x Zr _x ) O ₃ film obtained by binary sputtering was <100>.

[0024]

[Example] S on a silicon (Si) substrate by a thermal oxidation method
An iO ₂ film is formed to a thickness of 500 nm, and platinum (Pt
) A film was formed to a thickness of 100 nm to serve as the lower electrode.

Next, the sintered body of Ba Ti O ₃ and Ba Zr O
The sintered body of ₃ was used as a target together with the above substrate in a high frequency magnetron sputtering apparatus, and binary sputtering was performed under the following conditions.

Film forming temperature: 500 ° C. Gas pressure: 1 Pa gas composition (Ar: O ₂ ) ・ ・ ・ ・ ・ ・ 9: 1 High frequency power to Ba Ti O ₃・ ・ ・ ・ ・ ・ 1.6 to 3.2 W / cm ² Ba to Zr O ₃ High-frequency power ・ ・ ・ ・ ・ ・ 0 to 1.6 W / cm ² Sputtering time ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 5 hours And the power ratio of both is 10: 0 to 5: Sputtering was performed in the range of 5, and the crystal orientation of the thin film was determined by X-ray diffraction (XR
In D), the chemical composition was measured by an inductively coupled plasma emission spectroscopy (ICP), and a Pt film of 100 n was formed on this by a sputtering method.
The capacitor is made by forming it to a thickness of m, and the capacitance is measured by an impedance analyzer (Impedance / Gain Phase Analytical
zer).

As a result, when the Ba (Ti _1-x Zr _x ) O ₃ film is formed, the Ba 2 Ti ₃ O ₃ target and the Ba 2 Zr 2 O ₃ target are formed.
High frequency power ratio to ₃ targets and Ba (Ti _1-x Z
The relation between the r _x ) O ₃ film and the value of x is as follows.

When the high frequency power ratio is 10: 0 ... 0 When the high frequency power ratio is 9: 1 .... 0.015 When the high frequency power ratio is 8: 2・ ・ ・ ・ ・ ・ 0.082 When the high frequency power ratio is 7: 3 ・ ・ ・ ・ ・ ・ 0.209 Next, Fig. 1 shows the power supply ratio to the target.
It shows the effect on the dielectric constant when
When the power ratio is 9: 1, that is, Ba (Ti _0.985Zr
_0.015) O₃Shows a dielectric constant of about 150, which is
Ba Ti O₃Is superior to about 105 shown by.

[0029]

According to the present invention, the decoupling capacitor is formed on the signal layer below the uppermost layer, the insulating layer is formed on the signal layer, and a large number of LSIs are mounted on the insulating layer. In the MCM which is configured to be circuit-connected to the LSI by the provided via, a Ba (Ti _1-x Zr _x ) O ₃ film obtained by binary sputtering of Ba Ti O ₃ and Ba Zr O ₃ is used as a dielectric of the decoupling capacitor. It shows that it is excellent, and the use of this material enables downsizing of the MCM.

[Brief description of drawings]

FIG. 1 is a diagram showing an influence of a sputtering ratio on a dielectric constant.

Claims (2)

[Claims] 1. A dielectric material for a thin film capacitor for a multi-chip module, comprising barium zirconate titanate obtained by binary sputtering of barium titanate and barium zirconate. 2. The high frequency power ratio in sputtering of barium titanate and barium zirconate is 9: 1 to 7: 3.
The dielectric material of the thin film capacitor for a multi-chip module according to claim 1, wherein the dielectric material is formed in the range.