JP2001320172A - Thin film multilayer circuit board - Google Patents

Abstract

(57) Abstract: A thin-film multilayer circuit board has improved adhesion between a barrier layer provided between an adhesion improving layer and a conductive metal layer and a conductive metal layer. SOLUTION: An adhesion improving layer 4 and a conductor metal layer 6 are provided so as to be connected to a thick film base layer 2 and a thick film buried conductor 3 constituting a supporting substrate 1, and the adhesion improving layer 4 The gradient composition layer 5 whose composition changes continuously or stepwise from the refractory metal to the conductor metal constituting the conductor metal layer 6 is inserted between the conductor metal layer 6 and the high melting point metal from the adhesion improving layer 4 side. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film multilayer circuit board, and more particularly to a thin film multilayer circuit characterized by a barrier metal layer for improving the adhesion of a wiring layer provided on a thick film supporting substrate. It relates to a substrate.

[0002]

2. Description of the Related Art With the recent increase in the speed of computers and the increase in the capacity and integration of semiconductor devices, the mounting methods have also changed greatly. The multilayer wiring is formed by the spacer.

In order to meet such a demand, a thin film multilayer circuit board capable of providing high-density wiring, a so-called MCM
(Multi Chip Module) substrates have been commercialized and applied to electronic devices such as computers.
For high-speed signal propagation, it is necessary to use a resin having a low dielectric constant as an insulating material.

For example, in this MCM substrate, a photosensitive resin capable of forming a very thin dielectric layer on a thick film base layer by spin coating is usually used as a dielectric, and a signal pattern is also formed by sputtering. Since it is formed by a method and etching using a high-sensitivity resist, a high-density pattern that is incomparable with an ordinary printed wiring board can be realized.

In these thin film multilayer circuit boards, there are a case where I / O pins necessary for mounting electronic components are provided on the thin film side and a case where they are formed on the back surface side of the thick film. When the I / O pins are formed on the thin film side, I / O pins are often arranged around the substrate. However, there is an advantage that a via is not required on the thick film side. Due to the influence of wiring leading to I / O pins, it has been a disadvantageous method for performing high-density mounting.

Therefore, by forming an I / O pin on the back side of the thick film, it is possible to mount multiple terminals and to shorten the wiring length electrically, which is very advantageous in terms of performance. Thick film substrates with such vias include the most popular printed boards, multilayer ceramic circuit boards, array packaging PGA, BGA, and even more.
There are a wide variety of substrates, such as CSPs that are about the same size as LSI.

For example, MCM-C / D (Co-fir)
e: co-firing, Deposit: deposition process) is an MCM that deposits a thin film circuit on a ceramic substrate or a ceramic substrate in which a thick film circuit is formed.
a post (deposition process), ie, formation of a resin layer,
It is formed in multiple layers by a dry and wet process in which a series of steps consisting of via hole processing, conductor film formation and patterning by sputtering, vapor deposition, plating and the like are repeated.

In this case, the functional components such as the LSI
It will be connected to the component mounting pad formed on the surface layer of the substrate by soldering, and especially in the case of LSI,
Solder bumps are formed on the terminals and mounted on the MCM board face down.
(ollapsed Chip Connection)
Has been done.

Here, referring to FIG. 4, a conventional MCM-
C / D will be described. FIG. 4A is a schematic configuration diagram of a conventional MCM-C / D. The MCM-C / D includes a multilayer circuit board C portion 31 formed by simultaneous firing and a subsequent portion. It is composed of a thin film multilayer circuit board D section 32 formed by a vacuum process. An input / output pin 33 is provided on one surface of the multilayer circuit board C section 31 to exchange signals with the outside and supply power. .

On the other hand, on the thin film multilayer circuit board D section 32,
An LSI chip 34 is mounted in a flip manner by solder bumps 35 made of Pb-Sn or the like.
The heat generated in I is directly cooled.

FIG. 4 (b) is a schematic cross-sectional view in which the inside of the dotted line circle in FIG. 4 (a) is enlarged. In the multilayer circuit board C section 31, the inside of the ceramic substrate 37 is shown. Has a structure in which a W via 38 made of tungsten (W) penetrating through the front and back is formed at the same time as ceramic firing and is buried in a ceramic substrate 37. One side of the buried W via 38 has W-
A connection pad 39 made of Ni plating or Cr-Cu-Ni-Au or the like is provided, and an input / output pin 33 made of, for example, Kovar is connected by a solder 40.

On the other hand, a connection conductor 41 connected to the W via 38 is formed on the other surface, and a polyimide layer 4
4 and a thin film multilayer circuit board D portion 32 in which a Cu wiring layer 42 is sequentially laminated by a deposition process is provided. The Cu wiring layers 42 having different layers are connected by Cu vias 43. In the drawing, the connection structure of the central Cu via 43 actually shows connection states at different positions projected. FIG. 2 shows a state where it is concentrated at the center.

A component mounting pad 45 is formed by a plating process or the like so as to be connected to the uppermost Cu via 43. The solder bump 35 provided on the LSI chip 34 is melted and connected to this pad 45. Then, the LSI chip 34 is mounted.

In such a thin film multilayer circuit board, when a thick film substrate having vias is used to form a thin film multilayer wiring layer, the flatness and smoothness of the surface and the interface between the thick film and the thin film are reduced. Therefore, it is very important to have high reliability, and in many cases, this is a problem in many cases.

For example, when a conductive paste is applied to form a connection conductor on the surface of a thick film substrate by simultaneous firing (Co-fire), the film thickness is several tens to ten.
Since a thick film conductor having a thickness of about 0 μm is formed, if a thin film wiring layer is laminated thereon, the step becomes too large and unevenness occurs in the thin film multilayer wiring, so that it is difficult to form a fine pattern.

In order to improve the problem of the method of forming the connection conductor by firing, a method of directly plating the W via 38 with Ni plating and Cu plating is also known, as shown in FIG.
It will be described with reference to FIG. FIG. 5A is an enlarged view in the vicinity of the W via 38. The Ni plating layer 46 and the Cu plating layer 47 are provided directly on the exposed surface of the W via 38 by using an electrolytic plating method. Accordingly, the thickness of the connection conductor 41 can be formed thinner than the firing method.

However, as in the multilayer circuit board C section 31,
In a co-fired substrate, shrinkage during baking is anisotropic, and the position of the W via is shifted from a design value due to a slight difference in shrinkage. There is a problem that the subsequent thin film multilayer wiring cannot be formed in a photo etching process based on the design value.

Therefore, it is necessary for the thick film substrate to make contact with the thick film conductor by a position correction pattern using the thin film connection conductor. In this case, the adhesion between the thick film side and the thin film must be ensured, but the low-resistance metal necessary for the thin film multilayer wiring such as Cu does not always adhere to the thick film base layer or the thick film conductor. An adhesion improving layer for improving the adhesion between the thick film side and the thin film wiring is required.

For this reason, it is necessary to form a metal multilayer film having both a thin-film conductive layer for providing adhesion to the thick film side and a thin-film conductive layer necessary for thin-film multilayer wiring. It is necessary to have a layer structure in which mutual reaction and diffusion are suppressed while ensuring the property.

However, in any case, when a thick-film conductor is used as the connection conductor 41, unevenness caused by the thick-film conductor becomes a problem, so that the connection conductor itself is formed by a thin film. Depending on the configuration of the circuit, low-resistance Cu is used as the connection conductor 41 directly formed on the ceramic substrate 37.

As the ceramic substrate 37, usually,
An AlN ceramic substrate is used which matches the coefficient of thermal expansion of the silicon constituting the LSI chip 34 and has good heat dissipation. However, since Cu has poor adhesion to the AlN ceramic substrate, nitride is used as an adhesion improving layer. It is necessary to provide a Ti layer having good adhesion to the substrate.
i and Cu generate a diffusion layer and a compound layer, and further, depending on the heat treatment atmosphere, even a Ti oxide is formed in the diffusion layer, which is thermally unreliable.

Therefore, it is necessary to provide a diffusion preventing layer at the interface between the Ti layer and the Cu layer in order to prevent mutual diffusion between Ti and Cu.
A metal having excellent adhesion between Cu and Cu and not forming a compound with Ti and Cu is ideal.

As such a diffusion preventing layer, a high melting point metal such as W or Mo can be used. Therefore, a thin film connecting conductor using such a high melting point metal as a barrier layer will be described with reference to FIG. explain. FIG. 5B is an enlarged view in the vicinity of the W via 38. The Ti layer 48, the W barrier layer 49, and the Cu layer 50 are sequentially formed by a sputtering method, and then patterned. In this way, the connection conductor 41 is formed. This layer configuration allows the connection conductor 41 to be made thinner, and at the same time, improves thermal stability. It becomes possible to form the thin film multilayer circuit board D portion 32 having the same.

[0024]

However, since W and Mo serving as barrier layers do not react with Cu, it is difficult to achieve close contact between the Cu layer 50 and the W barrier layer 49, and there is a problem in reliability. .

Accordingly, an object of the present invention is to improve the adhesion between the barrier metal layer provided between the adhesion improving layer and the conductive metal layer and the conductive metal layer.

[0026]

Here, means for solving the problems in the present invention will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing the vicinity of a thick-film buried conductor showing a basic configuration of the present invention. See FIG. 1. (1) The present invention relates to a thin-film multilayer circuit board, in which an adhesion improving layer 4 and a conductive metal layer are connected so as to be connected to a thick base layer 2 and a thick embedded conductor 3 constituting a supporting substrate 1. And between the adhesion improving layer 4 and the conductor metal layer 6, the composition is continuously or stepwise changed from the high melting point metal to the conductor metal constituting the conductor metal layer 6 from the adhesion improving layer 4 side. Wherein the graded composition layer 5 that changes in any one of the above is inserted.

As described above, by inserting the gradient composition layer 5 whose composition changes from the high melting point metal to the conductor metal constituting the conductor metal layer 6 from the adhesion improving layer 4 side, the adhesion to the conductor metal is improved. It is possible to greatly improve, and it is possible to prevent mutual diffusion between the adhesion improving layer 4 and the conductive metal layer 6, thereby forming a thin-film connection conductor having excellent thermal stability. it can. In this case, the gradient composition layer 5 may have a composition that changes continuously or may change stepwise, and can be formed using a multi-source sputtering apparatus.

(2) The present invention is characterized in that, in the above (1), the gradient composition layer 5 has a composition ratio constituting a matrix of both a high melting point metal and a conductor metal.

As described above, the composition ratio of the gradient composition layer 5 needs to be a composition ratio constituting both the matrix of the high melting point metal and the conductor metal, that is, a composition ratio not constituting the interface.

(3) Further, according to the present invention, in the above (1) or (2), the conductive metal is either Cu or a Cu-based conductor containing Cu as a main component, and the refractory metal is W, Mo, Cr, Ta, Co, Nb, Rh, R
u, Re, Ir, and Os.

As described above, as the conductor metal, low-resistance Cu is used.
Alternatively, any of Cu-based conductors containing Cu as a main component is preferable, and W, Mo, Cr, Ta, Co, Nb, Rh, and R which do not constitute an alloy with Cu are preferable as the high melting point metal.
Any of u, Re, Ir, and Os is preferable. In addition,
As the adhesion improving layer 4, since the thick film base layer 2 is generally made of nitride ceramics, it is desirable to use Ti having good adhesion to nitride.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, a thin-film multilayer circuit board according to a first embodiment of the present invention will be described with reference to FIG. 2. FIG. 2 shows a multilayer circuit board C constituting the thin-film multilayer circuit board. FIG. 4 is a schematic cross-sectional view of the vicinity of a W via of a portion, in which the scale in the film thickness direction is exaggerated for easy understanding. Referring to FIG. 2, first, the surface of the multilayer thin film circuit board C section 11 is subjected to Ar etching using a multi-source simultaneous sputtering apparatus in which a Ti target, a W target, and a Cu target are set. The thickness is set, for example, to be connected to the constituent AlN ceramic substrate 12 and the W via 13 embedded in the AlN ceramic substrate 12.
A Ti adhesion improving layer 14 having a thickness of 100 nm and a W layer 15 having a thickness of, for example, 100 nm are sequentially deposited.

Subsequently, the gradient composition layer 16 is formed by simultaneously discharging the W target and the Cu target. In this case, the input power to the W target is 4 k
W, 2 kW, 1 kW
By sequentially changing the input power to the u target to 1 kW, 2 kW, and 4 kW, the thickness becomes, for example, 100 kW.
W-rich W− with atomic ratio W: Cu ≒ 70: 30 nm
The Cu composite layer 17 has a thickness of, for example, W: Cu 比 50:50 at an atomic ratio of 100 nm, and the W—Cu composite layer 18 has a thickness of, for example, 100 nm.
A graded composition layer 16 having an approximately three-layer structure of the Cu-rich W-Cu composite layer 19 of # 30: 70 is formed.

Subsequently, by discharging the Cu target independently, a C target having a thickness of, for example, 500 nm is discharged.
After the u-layer 20 is deposited, it is patterned into a predetermined shape to form a thin-film connection conductor.

In this case, annealing at 500 ° C. in vacuum and annealing at 500 ° C. in an N ₂ gas atmosphere are performed in order to confirm the thermal stability to the heat treatment step in forming the thin film multilayer wiring later. After performing two kinds of annealing treatments, the cross section of the substrate was observed. In each case, the crystal grains of the Cu thin film showed crystal growth due to recrystallization. Showed no significant change, confirming the thermal stability.

Thereafter, in the same manner as in the prior art, a thin film multilayer circuit board D is formed by alternately laminating an insulating film made of polyimide, a layer for improving adhesion to Cr, and a wiring layer consisting of a Cu layer. Is completed.

As described above, in the first embodiment of the present invention, a barrier layer using W for improving thermal stability is formed between the Ti adhesion improving layer 14 and the Cu layer 20. In this case, since the gradient composition layer 16 in which the composition changes stepwise from W to Cu is provided, the adhesion between the barrier layer and the Cu layer 20 can be improved, thereby improving the reliability. be able to. Note that the W layer 15 may be considered as a gradient composition layer.

That is, in the W-rich W-Cu composite layer 17, W forms a matrix, ie, a network,
In the W-Cu composite layer 18, both W and Cu individually constitute a matrix, and in the Cu-rich W-Cu composite layer 19, Cu constitutes a matrix.
No clear interface between the layers is formed, and the adhesion is increased.

Next, a thin-film multilayer circuit board according to a second embodiment of the present invention will be described with reference to FIG. 3. FIG. FIG. 3 is a schematic cross-sectional view of the vicinity of a via, and also in this case, the scale in the film thickness direction is emphasized in the figure for easy understanding. Referring to FIG. 3, first, the surface of the multilayer thin film circuit board C section 11 is subjected to Ar etching using a DC sputtering apparatus in which a Ti target, a Mo target, and a Cu target are set, and then the multilayer thin film circuit board C section 11 is formed. In order to connect to the AlN ceramic substrate 12 and the W via 13 embedded in the AlN ceramic substrate 12,
A 00 nm Ti adhesion improving layer 14 and a Mo layer 21 having a thickness of, for example, 100 nm are sequentially deposited.

Subsequently, the gradient composition layer 22 is discharged by alternately discharging the Mo target and the Cu target.
To form In this case, for example, the power supply time to the Mo target and the power supply time to the Cu target are changed stepwise so as to be opposite to each other.
Cu layer 24 of Mo layer 23 _1/10 nm of 0 nm _1, 30
Cu layer 24 ₂ nm of Mo layer 23 _2/10 nm, 20n
m of Mo layer 23 _3/10 nm of Cu layer 24 _3, 20 nm
The Mo layer 23 _4/10 nm of Cu layer 24 _4, 10 nm of Mo layer 23 _5/10 nm of Cu layer 24 _5, 10 nm of M
o layer 23 ₆ / 10nm of the Cu layer 24 _6, 10nm of Mo
Layers 23 _7/10 nm of Cu layer 24 _7, 10 nm of Mo layer 23 _8/10 nm of Cu layer 24 _8, 10 nm of Mo layer 2
3 _9/10 nm of Cu layer 24 _9, 10 nm of Mo layer 23
_10/20 nm Cu layer 24 _10, 10 nm of Mo layer 23 ₁₁
/ 20 nm Cu layer 24 ₁₁ , 10 nm Mo layer 23 ₁₂ /
30 nm Cu layer 24 ₁₂ and 10 nm Mo layer 23
To form a 26 layer of the Cu layer 24 _{12 12/90} nm.

As described above, the M layer composed of 26 layers during the film formation process was used.
The gradient composition layer 22 composed of a composite layer of o and Cu has a Mo-rich composition on the Mo layer 21 side, while Cu
On the layer 20 side, a step-shaped gradient composition layer 22 having a Cu-rich composition is formed.

Subsequently, by discharging the Cu target alone, a C target having a thickness of, for example, 500 nm is discharged.
After the u-layer 20 is deposited, it is patterned into a predetermined shape to form a thin-film connection conductor.

Also in this case, in order to confirm the thermal stability to the heat treatment step when forming the thin film multilayer wiring later,
After performing two kinds of annealing treatments: annealing at 500 ° C. in vacuum and annealing at 500 ° C. in an N ₂ gas atmosphere, the cross section of the substrate was observed. Although crystal grains were grown by crystallization, no remarkable change was observed in the Mo structure, which is a high melting point metal, and thermal stability was confirmed.

Thereafter, in the same manner as in the first embodiment, an insulating film made of polyimide, a Cr adhesion improving layer, and a wiring layer made of a Cu layer are alternately laminated to form a thin-film multilayer circuit board D portion. By doing so, the basic configuration of the thin film multilayer circuit board is completed.

As described above, in the second embodiment of the present invention, a barrier layer using Mo for improving thermal stability is formed between the Ti adhesion improving layer 14 and the Cu layer 20. In this case, since the gradient composition layer 21 whose composition changes stepwise from Mo to Cu is provided, the barrier layer and the Cu layer 2 are formed.
The adhesiveness with 0 can be improved, and thereby the reliability can be improved. Note that the gradient composition layer including the Mo layer 21 may be considered.

That is, on the Mo-rich Mo-Cu composite layer side, Mo forms a matrix, and on the Mo-Cu uniform composite layer, both Mo and Cu individually constitute a matrix. Since Cu forms a matrix on the composite layer side, a clear interface between the layers is not formed, and the adhesion is enhanced.

The embodiments of the present invention have been described above. However, the present invention is not limited to the configurations and conditions described in the embodiments, and various modifications are possible. For example, in each of the embodiments of the present invention, W or Mo is used as the refractory metal forming the barrier layer including the gradient composition layer, but is not limited to W or Mo.
Like W and Mo, it has good adhesion to Ti, and
Cr, T, which are refractory metals that do not react with Ti and Cu
Any of a, Co, Nb, Rh, Ru, Re, Ir, and Os may be used.

In each of the above embodiments, Cu is used as the conductor metal layer constituting the main part of the wiring layer. However, the present invention is not limited to pure Cu. A conductor may be used.

In the first embodiment, the gradient composition layer containing W as a constituent element is formed as a layer whose composition changes stepwise by using the simultaneous sputtering method. A graded composition layer in which the composition continuously changes by continuously changing the input power may be used. Further, similarly to the second embodiment, the superlattice layer may be formed using a DC sputtering method. The gradient composition layer may be formed according to a typical structure.

In the second embodiment, the gradient composition layer containing Mo as a constituent element is formed as a layer whose composition changes stepwise by a superlattice structure using DC sputtering. However, similarly to the above-described second embodiment, it may be formed as a layer whose composition changes stepwise by using a simultaneous sputtering method, and furthermore, the input power to each target is continuously changed. Thus, a graded composition layer whose composition continuously changes may be used.

[0051]

According to the present invention, the W of the multilayer circuit board C is reduced.
When forming a thin film connection conductor connected to a via, a barrier layer for preventing interdiffusion is provided as a gradient composition layer, so that the adhesion between the conductor metal layer and the barrier layer can be significantly improved, thereby Since a thin film connection conductor having excellent thermal stability and excellent adhesion can be formed, a thin film multilayer circuit board having a highly reliable thin film multilayer circuit board D which does not deteriorate due to repeated heat treatment and high temperature holding can be used. It can be realized, and it greatly contributes to high-density mounting of electronic components.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory diagram of a thin-film connection conductor according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a thin-film connection conductor according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional MCM-C / D.

FIG. 5 is an explanatory view of a connection conductor in a conventional thin film multilayer circuit board.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Support substrate 2 Thick film base layer 3 Thick film buried conductor 4 Adhesion improving layer 5 Gradient composition layer 6 Conductive metal layer 11 Multilayer circuit board C part 12 AlN ceramic substrate 13 W via 14 Ti adhesion improving layer 15 W layer 16 Gradient composition layer 17 W-rich W-Cu composite layer 18 W-Cu composite layer 19 Cu-rich W-Cu composite layer 20 Cu layer 21 Mo layer 22 Gradient composition layer 23 ₁ -23 ₁₃ : Mo layer 24 ₁ -24 ₁₃ : Cu Layer 31 Multilayer circuit board C part 32 Thin film multilayer circuit board D part 33 I / O pin 34 LSI chip 35 Solder bump 36 Cooling fin 37 Ceramic substrate 38 W via 39 Connection pad 40 Solder 41 Connection conductor 42 Cu wiring layer 43 Cu via 44 Polyimide layer 45 Pad 46 Ni plating layer 47 Cu plating layer 48 Ti layer 49 W barrier layer 50 Cu layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E351 AA07 BB01 BB23 BB24 BB32 BB38 CC03 DD04 DD14 DD17 DD18 DD19 DD20 GG01 GG11 5E343 AA11 AA39 BB15 BB22 BB24 BB38 BB39 BB40 BB45 BB71 DD25 A05 A05 A05 A41 A01A01 BB16 CC10 CC31 CC32 CC35 CC36 DD03 DD15 EE33 GG01 GG28 HH11

Claims (3)

[Claims] An adhesion improving layer and a conductor metal layer are provided so as to be connected to a thick film base layer and a thick film buried conductor constituting a supporting substrate, and the adhesion improving layer and the conductor metal layer are provided. Between the high-melting-point metal from the adhesion improving layer side to the conductive metal constituting the conductive metal layer, wherein the composition is continuously or stepwise changed gradient composition layer is inserted, characterized in that Thin film multilayer circuit board. 2. The thin-film multilayer circuit board according to claim 1, wherein the graded composition layer has a composition ratio constituting a matrix of both the refractory metal and the conductor metal. 3. The conductor metal is made of Cu or a Cu-based conductor containing Cu as a main component, and the refractory metal is made of W, Mo, Cr, Ta, Co, Nb, R
3. The thin-film multilayer circuit board according to claim 1, wherein the thin-film multilayer circuit board is made of any one of h, Ru, Re, Ir, and Os.