JP2002057460A - Method for manufacturing multilayer circuit consisting of conductive path and micro-via - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an improved interconnection circuit that has high integration density, and consists of a conductive electrical path, a pad, and a micro-via. SOLUTION: A first layer 103 that contains a synthetic object, having capability of inducing metal covering in the post treatment, and is made of an insulating, photosensitive resin is formed on a substrate 101 having metal covering 102 on a surface (a). The first layer is exposed and developed for exposing to the metal covering 102 on the substrate (b). While a second layer 105, that forms selective protection and is made of the photosensitive resin, is being used, the metallic conductive path and micro-via are formed in the first layer made of the insulating, photosensitive resin, and on the surface of a part exposed in the step (b) by the metal covering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an improved method for fabricating an interconnect circuit having a high integration density and consisting of conductive tracks, pads and microvias.

[0002] As used herein, the term "microvia" means a microconnection through the thickness of an insulator (or dielectric).

In the field of electronics, there is a trend towards optimal product miniaturization and improved performance with respect to speed. These trends are based on BGA, CGA, CS
This has been fueled by the increasing use of surface mount components such as P or other flip chip components.

It is desired that the integration density be increased in three dimensions. That is, in the axial direction, by successively laminating thinner insulating / copper layers in order to obtain a multilayer, and in a plane perpendicular to this direction, the finer conductive paths and pads are closely arranged. This is done by:

[0005] The method of the present invention relates to a method for controlling the width of a conductive path smaller than 100 µm and the width between mutual conductive paths (or a gap between conductive paths).
These requirements are met by manufacturing a "fine line" circuit characterized by a hole or via diameter of less than 100 .mu.m.

The method of the present invention also ensures good adhesion of the metal layer to the insulating substrate and limits the inaccuracies caused by successive stacking of the layers. The method of the invention also has the advantage of a reduced number of steps (of the process) and of economics.

According to the first feature of the present invention, the present invention provides the first
A method is provided for forming conductive paths and microvias in an insulator overlying a first circuit level or first metal layer without damaging the first circuit level or first metal layer.

[0008]

2. Description of the Prior Art U.S. Pat. No. 5,260,170 describes a method of making a circuit with conductive microvias. The method comprises the following steps: Electrochemical metal film catalyst (electrochemical metal film catalyst)
1. applying a first layer of photosensitive (or photosensitive) resin containing metallization catalyst); 2. irradiating and developing the first layer to expose certain portions of the substrate; 3. applying a second layer of photosensitive resin that does not contain a metal film catalyst; To expose the first layer and certain parts of the substrate,
4. exposing and developing the second layer; Electrochemical metal coating.

Steps 3, 4, and 5 are used to form conductive paths and microvias, while selectively forming a second layer of photosensitive resin. This layer is not removed. This process is repeated several times to form a multilayer circuit, and the finally obtained surface is used as a substrate.

[0010] The circuit obtained by the above process has a drawback in terms of planarity, which is a disadvantage for accuracy. This disadvantage is caused by the phenomenon of swelling or bumping of the photosensitive resin due to contact with a solution used for various treatments such as activation of a catalyst and a metal film. This is also due to the stacking of too many layers.

[0011]

SUMMARY OF THE INVENTION The present invention provides, inter alia, an improved method for fabricating circuits while allowing better planarity to be achieved. The method further:
It has advantages in terms of reliability by reducing the amount of circuits that are out of specification as a result of layer overlay and microvia positioning.

[0012]

SUMMARY OF THE INVENTION To this end, the present invention provides, for at least one level, a method for fabricating a multi-layer interconnect with conductive paths and microvias comprising the following fabrication steps. The method provides: a) an insulating, substrate-containing, metallizable and / or potentially metallizable part containing a compound capable of inducing a metallization in subsequent processing. B) exposing the first layer to selectively expose metallizable and / or potentially metallizable portions of the substrate. B) irradiating and developing; c) a first layer of insulating photosensitive resin by means of a metal coating, with the use of a second layer of photosensitive resin to form selective protection, and step b). Gold on the surface of the part exposed by Forming a conductive path and microvias. The method is further characterized in that the method comprises the step of removing the second layer of photosensitive resin to produce the level in question.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A circuit may have layers of different types of material and / or layers deposited on a defined portion.
(Film material). That is,
The metal tracks, metal microvias, and additionally metal pads, which are divided by location and are supported by a layer of insulator, are created.

The conductive paths, microvias, and pads form an interconnect circuit. The conductive path is that part of the circuit that is located on the surface of the insulating material. They are generally formed of thin lines (or lines).

The circuit according to the invention consists of several circuit levels. Each circuit level corresponds to a combination of conductive paths on the surface of the insulating material. The circuit levels are therefore separated by layers of insulating material, with metal connection areas between the levels. These metal connections between two or more levels are called microvias. Such structures and such terms are known to those skilled in the art.

The method of fabricating the circuit for at least one level comprises removing the second layer for that level and steps a), b) and c).

According to the present invention, the layer of insulating material separating the circuit levels comprises an insulating photosensitive resin containing a compound capable of inducing a metal film in subsequent processing. This layer is called the first layer. Microvias that penetrate this layer and provide metal connections between levels are located in portions of the first layer that have been removed by exposure and development. They are called "photosensitive vias".

In step a), a first layer of a photosensitive resin is formed on the surface of the substrate having metallizable and / or potentially metallizable portions.

The expression "potentially metallizable" means a surface part which cannot be metallized directly electrolytically and / or electrochemically, but which can be metallized after appropriate treatment. For example, it may be a surface portion of an insulating photosensitive (or non-photosensitive) resin containing a composition that can be metallized in a later process. In particular, it may be part of a layer that was used as a first layer of insulating photosensitive resin during lower level manufacturing.

The expression "metallizable surface part" means a surface that can be metallized directly electrolytically and / or electrochemically. For example, it may be a conductive path, pad, or microvia on the surface of the substrate.

The conductive paths and the microvias are formed by metallizing the surface of the first layer of the photosensitive resin and the portion exposed in step b). The metal part formed on the surface of the part exposed in step b) corresponds to the microvia.

Selective protection is provided by the use of a second layer of photosensitive resin to form conductive paths and microvias. Methods for forming metal interconnects with selective protection by a layer of photosensitive resin will be known to those skilled in the art. In particular, the pattern type (pattern-
type) and panel-type processing. In the treatment of the present invention, the metal film of a part of the first layer of the photosensitive resin is included in the resin, and is induced to be metallized in a later treatment (or to be metallized after an appropriate treatment). It is made possible by a compound that can.

In accordance with the present invention, the layer of photosensitive resin used to provide selective protection (the second layer of photosensitive resin) is removed during processing.

By removing the second layer of photosensitive resin, the planarity for intermediate circuit levels is improved. The expression “intermediate level” means not the final level, but the level used as the lower level when forming the upper layer. It also makes available, in certain parts, an insulating photosensitive resin containing a compound capable of inducing a metal film in a later treatment. Unlike when the second layer of photosensitive resin is not removed, when there is no inaccuracy when creating higher circuit levels or placing microvias, a metal film with very good adhesion And the formation of contacts.

The substrate may be a lower circuit level generated according to the present invention or another method. If the substrate is a lower circuit level generated according to the method of the present invention, the metallizable portion is a lower level circuit portion, especially a portion of a conductive path and / or a microvia. Further potentially metallizable portions are the non-metallized portions (or non-metallized portions) of the first layer of insulating photosensitive resin used during the lower level production.

The substrate may also be a printed circuit having one or more levels on a rigid (or flexible) support (with selectively conductive vias). Regarding support, it may be, for example, an injection molded insulating or composite material common in the field of printed circuits. For example, an epoxy / glass fiber support may be used. It may be an insulator made of non-woven fiber web impregnated with an insulating resin or paper. The presence of paper or web ensures better homogeneity of the coefficient of thermal expansion (TEC).

Most preferably, non-woven aramid (commercial aromatic polyamide) whose support is pre-impregnated with an epoxy resin, a polyimide resin, or a mixture of these resins
polyamide)). Even better, these aramid fibers (preferably meta-aramid fibers, para-aramid fibers, or mixtures of these fibers) are functionalized (functionalized with a thermally crosslinkable chemical moiety). Pre-impregnated with polyamide-imide). Functionalizing (func
nationization) may be achieved by a double bond or a maleimide group, as described in European Patent 0,336,856 or US Patent 4,927,900. Preferred is 35 to 60% by weight, more preferred 44 to 55% by weight,
More preferred is 40-50%, for example, 47% of insulating resin.

By way of example, the thickness of the web is between 10 and 7
0 μm, preferably 15 to 50 μm
And more preferably 20 to 40 μm
It is. Generally, it has a grammage of 10 to 5
0 g / m ² , and 15 to 40 g / m
a m ^2.

It should be understood that circuits obtained according to the present invention can be made on one or both sides.

In step a), a first layer of an insulating photosensitive resin is formed on a substrate. First insulative photosensitive resin
The layer contains a compound capable of inducing a metal film in a later treatment. Preferably, the composite is a metal oxide particle. Metal oxides are Cu, Co, Cr, Ni, P
It is selected from oxides of b, Sb, and Sn, and mixtures (or compounds) thereof. Generally, cuprous oxide Cu
₂ O is preferred. The resin may also include an inert, non-conductive filler.

As regards the metal oxide, it must be in the form of small-sized particles. The size of the particles is usually between 0.1 and 5 μm.

The resin is selected from negative or positive photosensitive resins. Preferably, it is in the form of a solvent, a solution, or an uncrosslinked stage-liquid for the substrate or lower circuit level.
A fluid). An example of resin is Van
PROBIMER type sold by tico. Compounds capable of inducing a metal film in a later treatment are in principle introduced into these resins before the layer is formed.

The thickness of the resin is such that sufficient insulation occurs between the two conductive metal layers. Preferably, it is less than 100 μm, for example between 10 and 20 μm, preferably 2 μm.
It is between 0 and 40 μm. The dielectric constant of the insulator layer is preferably 5 or less.

Compounds capable of inducing a metal film in a subsequent process are used to produce a metal film after the process, for example, a process for forming a sublayer. The processing that can be used will be described later.

In step b), the first layer of resin is exposed and developed. The parts that are removed during development (depending on the properties of the resin) are the positive or negative parts, the exposed or unexposed parts.

The operation of exposing and developing the layer of photosensitive resin to expose a portion of the underlying layer is known to those skilled in the art. Two known techniques in this field can be applied as they are.

The first technique is to expose a resin layer using a predetermined mask. The second technology is LDI (Laser Direct) for directly exposing the photosensitive resin.
Imaging) technology. This technique has economic advantages because it does not use a mask.

According to a second technique, the photosensitive resin is selectively exposed on a pixel-by-pixel basis by scanning the surface of an insulator coated with the photosensitive resin with a laser beam.

The soluble portion of the resin is then removed in the same manner as in the prior art using positive and negative photosensitive resins (ie, the first technique).

For implementing this second technique, for example, two types of lasers are suitable: lasers operating in the infrared (thermal LDI) and UV lasers operating in the wavelength range from 330 to 370 nm. (UV
-LDI).

Step c) consists of a number of steps.
There are several ways to carry out step c), corresponding to a sequence of different steps (or a series of steps). Three sequences corresponding to different implementations will be described later.

In step c), a second layer of a photosensitive resin is used. Preferably, the second layer does not contain a compound capable of inducing a metal film in subsequent processing.

The resin for the second layer may be selected from positive or negative photosensitive resins. The layer may be in the form of a solvent, a solution, or an uncrosslinked stage-liquid.
A fluid) could be formed by application. Examples of resins are PROBIMER types sold by Vantico and the like.

In particular, the photosensitive resin layer of the first layer is, depending on the state, a finely divided inorganic filler (pulverulent mineral fibrous).
ller) and other non-conductive and inert compounds. These may be, for example, particles of calcium carbonate. The presence of such a filler, especially in the first layer, improves the adhesion and adhesion of the metal layer formed.
The size of the filler particles is such that they are compatible with the processing of the resin application.

In step c), before the formation of the second layer, the second layer is exposed in order to expose certain parts of the first layer and / or the substrate and / or the metal layer formed. Is exposed and developed. The characteristics of the exposed parts often depend on the particular implementation used. The method of implementation is described below. For example, in the first embodiment, a specific portion of the first layer and the portion of the substrate exposed in step b) are exposed, and in another embodiment, the entire surface of the first layer is formed. Certain portions of the metal layer are exposed. The parts that are removed during development (depending on the properties of the resin) are the positive or negative parts, the exposed or unexposed parts.

Exposure and development of the second layer of photosensitive resin may be performed using the methods described for the first layer of photosensitive resin.

The conductive paths and microvias may be formed over the entire surface, before the second layer of photosensitive resin has been applied, or after certain portions of the second layer have been removed, or over the second layer of photosensitive resin. It is formed by metallizing the parts not protected by the layer. The metal coating may be performed electrochemically (electroless) and / or electrochemically (by current). The latter is preferred because it is faster. Further, the treatment may be performed in an acidic medium. This prevents the photosensitive resin from swelling (or bumping), improves positioning accuracy for various exposures and developments, and improves circuit reliability and life. For electrolytic metal coatings, it is preferred to carry out with increased current (or with increasing current). The metal is preferably copper.

[0048] Electrochemical (electroless) metallization is a known technique which is described in the encyclopedia of Polymer Science.
and Technology, 1968, Vol. 8, page 658
-61. Similarly, electrolytic metallization (by current) is a known technique, and is described in the Encyclopedia of
Polymer Science and Technology, 1968, Vo
l. 8, pages 661-63.

According to a particularly preferred method for practicing the invention, (whether electrochemical or electrolytic)
The metal coating is at least 8 μm, preferably 10
To a metal layer having a thickness of 20 μm.

Step c) preferably comprises forming a metallizable sublayer before the metallization. This sublayer may be a surface of the first layer of photosensitive resin or a first layer having a second layer of protection on other portions.
Formed on the exposed surface of the layer. Depending on the case at that time, the formed sublayer may be continuous or discontinuous, and may or may not be suitable for a direct electrolytic metallization. On the other hand, they are always suitable for electrochemical metal coatings. In this case, the electrochemical attachment of the metal is catalyzed by the sublayer, and the metal film is equivalent to the case where palladium or platinum is used.

There are two preferred methods for creating a sublayer that can be metallized.

According to a first method for producing a sublayer, a compound capable of inducing a metal film in a later treatment is selected from the above-mentioned metal oxides, and the first layer or the first layer The sublayer is formed by contacting the exposed portions with a solution of a salt of a noble metal that can be reduced by the oxide particles.

In this step, the other layers also come into contact with the solution
there is a possibility. This is a useful thing for these layers.
is not. Therefore, a continuous sublayer of precious metal
Formed on the exposed surface of the first layer. Sublayer table
The surface resistivity is 10⁶From 10 ³Ω / □. Liked
10 things³Ω / □ or less. This is preferred
As a matter of fact, the increased electric current
Allows the membrane to run. Increased oxide particle density
It is understood that larger will improve the adhesion of the sublayer
Must be done.

[0054] The solution of the noble metal salt of choice is Cl ^-, NO ^- _3,
And CH ₃ COO ^- containing a counter ion selected from, Au, Ag, R
h, Pd, Cs, Ir, and Pt salts. The contacting treatment may be performed by dipping, spraying, or passing through a roller. The solution of the noble metal salt has a pH of 0.5 to 3.5, preferably 1.5 to 2.
5 is acidic. The pH may be controlled by adding an acid. Treatment in an acidic medium furthermore makes it possible to limit the expansion (or bulging) of the resin layer occurring in the basic medium. By using this first method of generating circuits, excellent accuracy and planarity are obtained. If the first layer of the photosensitive resin contains calcium carbonate particles, it is to be understood that prior to treatment with the acidic solution of the salt of the noble metal, washing with an acidic solution such as acetic acid may be performed. No. This washing increases the roughness of the surface, makes it possible to dissolve the calcium carbonate particles present on the surface and improves the tackiness of the metal film.

For the first method of sublayer formation, metal oxide particles are preferred, such as MnO, NiO, Cu ₂ O,
And SnO, preferably in the first layer in an amount of 2.5 to 90% by weight, more preferably in an amount of 10 to 30% by weight. The preferred metal oxide is cuprous oxide Cu ₂ O. As a preference,
The solution contains at least 10 ⁻⁵ mol / l, preferably 0.0005 to 0.005 mol / l of the salt of the noble metal. A continuous sublayer of noble metal with a thickness of less than 1 μm is obtained. The resulting sublayer has excellent homogeneity, thereby improving the quality of the connection obtained after the metallization. Usable salts are AuBr ₃ (HAuSr ₄ ), AuCl ₃
(HAuCl4), or Au ₂ Cl ₆ , silver acetate, silver benzoate (si
_{lver benzoate), AgBrO 3, AgClO} 4, AgOCN, AgN0 3, Ag 2
SO ₄ , RuC1 ₄ -5H ₂ O, RhCl ₃ -H ₂ O, Rh (N0 ₂ ) ₂ -2H ₂ O, Rh ₂ (S
O ₄ ) ₃ -4H ₂ O, Pd (CH ₃ COO) ₂ , Rh ₂ (SO ₄ ) ₃ -12H ₂ O, Rh ₂ (SO4) ₃
-15H ₂ O, PdCl ₂ , PdCl ₂ -2H ₂ O, PdSO4, PdSO ₄ -2H ₂ O, Pd (C
_{H 3 COO) 2, OsCl4,} OsCl 3, OsCl 3 -3H 2 O, Osl 4, IrBr 3 -4H 2
0, IrCl ₂ , IrCl ₄ , IrO ₂ , PtBr ₄ , H ₂ PtCl ₆ -6H ₂ O, PtC
_{l 4, PtC1 3, Pt (} SO 4) 2 -4H 2 O, and Pt (COCl ₂₎ Cl _{2, and, NaAuCl 4, (NH 4)} 2 PdCl 4 (NH 4) 2 PdCl 6, K 2 PdCl 6 And KA
uCl the corresponding composite such as _4.

The obtained sublayer is particularly suitable for an electrolytic metallization. For example. Electrolytic metallization with increased current may be used.

The formation of the sublayer according to the first method consists in particular of the following operations: exposure of the metal oxide particles contained in the first layer of the photosensitive resin. This operation is preferably performed with an alkaline etch (e.g., using sodium hydroxide or potassium hydroxide in a water-soluble / alichol-based medium) to remove exposed oxide particles, and optionally, Performed by rinsing with water in an ultrasonic bath; if the first layer of photosensitive resin contains an inert filler, such as a calcium carbonate filler, the surface is slightly roughened by acidic etching. This operation is preferably separated from the operation for forming the metal sublayer; forming a continuous metal sublayer of the noble metal by contact with a water-soluble, acidic solution of the noble metal. Note that because the noble metal acts as a barrier (or barrier) for a continuous oxidation-reduction reaction, the resulting sublayer is generally a monoatomic layer.
The layer becomes continuous as some of the metal oxide particles release ions upon dissolution. These ions react in an aqueous medium containing a salt of a noble metal, reducing this metal, which attaches and fills the space between the particles. Inclusion of a more water-soluble precious metal salt medium results in a more efficient and economical reaction. For this reason, it is preferred to carry out the reaction in a thin layer. That is, immersion in an aqueous solution containing a salt of a noble metal, and then removing it as soon as possible. The reaction contained the desired product (or
Occurs in a layer of aqueous solution (entrained).

According to another method of forming a sublayer, a compound capable of inducing a metal film in a later treatment is selected from the above-mentioned metal oxides, and the sublayer is formed of a first layer.
The exposed portion of the layer or first layer is formed by contacting the exposed portion with a reducing agent capable of reducing oxide particles.

At this step, other layers may come into contact with the reducing agent, but this is not convenient. Therefore, the reduced sublayer and the conductive form are formed on the surface of the first layer from the metal oxide.

According to a second method of forming a sublayer, the preferred metal oxide is cuprous oxide Cu ₂ O. According to this method, the first layer is preferably 10 to 90% by weight, more preferably 2 to 90% by weight.
Contains 5 to 90% metal oxide. In the alternative, it contains no more than 10% cuprous oxide. Depending on the case at that time, the formed sublayer may be continuous or discontinuous, and may be 0.01 to 10 ⁶ Ω / □.
With surface resistivity.

The achievable surface resistivity on the sublayer depends on the composition of the first layer of photosensitive resin. It should be understood that the higher the density of the oxide, the better the adhesion of the sublayer.

The first layer of the photosensitive resin has a weight ratio of 10 to 9
From 0% metal oxide; from 0 to 50% by weight of one or more inert, non-conductive fillers; and from 10 to 90% by weight of polymer resin, reduction is preferred. The process is continued until a surface resistivity of 0.01 to 10 ³ Ω / □ is obtained. In general, a continuous sublayer is obtained. The achieved continuity and surface resistivity, in particular, make it possible to use a direct electrolytic metallization on the sublayer. For example, an electrolytic metallization with increased current may be used.

Preferably, the first layer is at least 10% by weight of a metal oxide; from 0 to 50% by weight of one or more inert, non-conductive fillers; and If the ratio consists of 50-90% polymer resin, the reduction is continued as preferred until a surface resistivity of greater than 10 ⁶ Ω / □ is obtained. in this case,
The sublayer may be discontinuous.

The continuous or discontinuous sublayer also allows the catalysis of the metal deposit produced in step g), which is compatible.

More specifically, this step prevents breakage or interruption of electrical conduction in the metallized vias and helps to improve the adhesion of metal deposition in subsequent processing.

The formation of the sublayer according to the second method particularly comprises the following steps: exposure of the metal oxide particles contained in the first layer of photosensitive resin. This operation is preferably performed with an alkaline etch (e.g., using sodium hydroxide or potassium hydroxide in a water-soluble / alichol-based medium) to remove exposed oxide particles, and optionally, Performed by rinsing with water in an ultrasonic bath; if the first layer of photosensitive resin contains an inert filler, such as a calcium carbonate filler, the surface is slightly roughened by acidic etching. This operation is preferably separated from the operation for forming the metal sublayer; formation of the metal sublayer by contact with an aqueous solution containing a reducing agent. The sublayer is preferably formed as a thin layer by immersion in an aqueous solution containing a reducing agent and rapid removal according to principles similar to those described above.

Note that when the metal oxide is cuprous oxide, some of the copper is reduced to the CuH state, a state that acts as a catalyst for the formation of the sublayer. If excess CuH is present, it slowly converts to copper metal at room temperature and hydrogen diffuses out. Here, the existence of the transitional hydroxide will not be further described, but only the metal layer will be described.

To carry out the reduction, the person skilled in the art will be able to select one of the reducing agents capable of reducing the metal oxide to oxidation state zero.

In this step, achieving the desired resistivity value depends, on the one hand, on the proportion and properties of the metal oxides in the polymer matrix forming the insulator, and, on the other hand, on the reduction. Degree, especially the type of reducing agent and
Depends on prior stripping.

The properties of the deposited metal layer vary depending on the type of reducing agent used and the properties of the metal oxide to be reduced. According to a preferred method of practicing the invention, the reducing agent is a borohydride.

The behavior of the borohydride when the metal oxide is cuprous oxide will be described in detail below.

Cu ₂ O is reduced to metallic copper by the behavior of borohydride. With the use of this type of reducing agent, the layer formed on the surface of the insulator is a continuous or discontinuous copper layer.

The borohydrides which can be used are substituted borohydrides or unsubstituted borohydrides. Substituted borohydrides in which most three hydrogen atoms of the borohydride ion have been replaced by substituents that are inert in a reduced state, such as alkyl, allyl, and alkoxyl groups, may be used. Preference is given to using alkaline borohydrides whose alkaline part consists of sodium or potassium. Typical examples of suitable compounds are: sodium borohydride, potassium borohydride, sodium disil sodium borohydride, and potassium triphenyl hydride.

The reduction treatment is performed simply by contacting the insulating surface with a solution of borohydride in water or a mixture of water and an inert polar solvent such as a lower aliphatic alcohol.

Preferred is a solution of pure borohydride. The concentration of these solutions may vary in a wide range, but is preferably between 0.05 and 1% (by weight of borohydride active hydrogen in the solution). The reduction treatment may be performed at an elevated temperature. However, it is preferred to be carried out at a temperature close to room temperature, for example, 15 to 30 degrees. Talking about performing the reaction, it must be noted that it gives B (OH) ₃ a rise to OH ^- ions, which has the effect of increasing the pH of the solution during the reaction. However, at high pH values, e.g., 13 or more, the rate of reduction is reduced, so it is preferred to work in a buffered medium to have a precisely defined reduction rate.

It is possible to easily control the degree of reduction mainly by changing the processing time. The processing time required to obtain the desired value of surface resistance is generally short and depends on the amount of oxide contained in the insulator, and is typically between about 1 minute and about 15 minutes. For any treatment time, for example, boric acid, oxalic acid, citric acid, tartaric acid, or
The addition of various promoters, such as metal chlorides such as cobalt (II) chloride, nickel (II) chloride, manganese (II) chloride, and copper (II) chloride, further alters the rate of reduction. It is possible to do.

It is also possible to vary the amount of borohydride in order to control the degree of reduction. A preferred method consists of immersing the substrate to be reduced in a relatively viscous borohydride solution and extracting the substrate for the reduction operation in air. It consumed the borohydride ions BH4 ^- the amount of which depends on the viscosity. BH4 ^- is thereby reacted with a thin layer of the surface to be reduced. This method has the advantage that it does not contaminate the original aquarium and does not destabilize it.

The exact state of the reduction with borohydride is described in EP 82,094 and the like. However, it should be understood that, according to the present invention, only the surface portion of the insulator needs to be reduced.

The sublayer metallization is generated as described above. During circuit level generation, the layer of photosensitive resin is removed. This method may be performed in various steps, depending on the method of implementation. Removal may be performed by lysis or stripping. A technique for completely removing a photosensitive resin layer is known.

Removal is easier if the second layer of photosensitive resin is not in a cured state. Preferably, it is removed in the A-stage.

The method includes a processing step, such as a B-stage, for disposing the first layer of the photosensitive resin in the cured state. Processing may include, for example, a curing operation. It is preferably performed after the second layer of photosensitive resin has been removed. The process provides a more stable circuit (especially in terms of dimensions) and allows for improved placement accuracy in the exposure and development steps. In addition, it limits the phenomenon of swelling (or bumping) on contact with solutions used in various processes.

The method is particularly suitable for printed circuits and multilayer modules with a high integration density.

[0083] Further details and advantages of the present invention will become more apparent from the following description of specific embodiments. More particularly, three implementation methods are described, illustrated by the drawings showing schematic cross-sectional views of circuits made in accordance with the present invention at various steps of the process.

[0084]

EXAMPLE 1 According to a first embodiment, the method comprises the following steps: a1) On a substrate 101 with a metallized part 102 and / or a potential metallized part. , Cu, Co, Cr, Ni,
Pb, Sb, and Sn oxides and their mixtures, metal oxide particles, and, depending on the state, one or more nonconductive and insulative photosensitive materials containing an inert filler Forming a first layer 103 of resin; b1) exposing and developing the first layer to selectively expose metallizable or potentially metallizable portions of the substrate; c1. A) forming a second layer 105 of a photosensitive resin which is intended for selective protection and does not contain metal oxide particles on exposed portions of the first layer and the substrate; d1) specific portions of the first layer and Exposing and developing the second layer to selectively expose certain portions of the substrate; e1) a metallizable sublayer 108 in the following manner.
Forming: contacting a solution of a salt of a noble metal that can be reduced by the metal oxide particles; or contacting the metal oxide particles with a reducing agent that can be reduced. f1) electrochemically and / or electrolytically depositing a metal layer to deposit the metal layer 109 on the first layer and exposed portions of the substrate; g1) removing the second layer of photosensitive resin.

The first embodiment employs a pattern type (patt
ern-type) Corresponds to the metal film according to the treatment. In the first embodiment, the second layer of photosensitive resin is removed in step g1). Steps a1) and b1) correspond to steps a) and b). The composite of the first layer of insulating photosensitive resin capable of inducing a metal film in later processing is Cu, Co,
A metal oxide selected from oxides of Cr, Ni, Pb, and Sn. Step c) of forming the conductive paths and microvias is a sequence (or series of steps) of steps c1), d1), e1), f1) and g1).

The method for performing each step is as described above. In a manner according to the first embodiment, the photosensitive via 104, ie, the insulating photosensitive resin that appears (or is created) in the metallizable part 102 or the potentially metallizable part. The via of step b1)
Is formed. In step d1), a via 106 is created in the photosensitive via area 104 to expose the metallizable portion 102, and a via 107 is created in a partial area of the first layer of photosensitive resin. Doing so creates selective protection. In step e1), a metallizable sublayer 108 is formed according to one of two optional methods (preferably the first method) with the aid of a salt of a noble metal in an acidic medium. Step f
In 1), a metal coating is formed (preferably electrolytically). In particular, forming conductive paths and micro vias,
A metal interconnect 109 is obtained. In step g1),
The second layer of the photosensitive resin is removed. The surface of the resulting circuit consists of: a first layer 113 of photosensitive resin; a portion 11 of the conductive path on the surface of the first layer which is not in contact with the substrate.
1; micro via 110 in contact with the substrate; part 1 of the conductive path on the surface of the first layer in contact with the micro via
12.

(Embodiment 2) According to the second embodiment,
The method comprises the following steps: a2) Cu, Co, Cr, Ni, Cu on the substrate 201 with the metallized part 202 and / or the potential metallized part.
Pb, Sb and Sn oxides and metal oxide particles which are mixtures thereof and, depending on the state, an insulating photosensitive resin containing one or more non-conductors and an inert filler B2) exposing and developing the first layer to selectively expose metallizable or potentially metallizable portions of the substrate; c2) Forming a metallizable sublayer 205 on the surface of the first layer of photosensitive resin and exposed portions of the substrate: contacting with a solution of a salt of a noble metal that can be reduced by metal oxide particles Or by contacting the metal oxide particles with a reducing agent capable of reducing; d2) electrochemically depositing the metal layer 206 on the first layer and the exposed portions of the substrate; And / or
E2) a second layer 207 of a photosensitive resin on the metalized surface;
F2) exposing and developing the second layer to selectively expose certain portions of the metal layer; g2) removing the metal layer from the areas of the portions exposed in step f2) H2) removing the second layer of photosensitive resin.

The second embodiment employs a panel type (panel-
type) Corresponds to the metal film according to the treatment. In a second embodiment, the second layer of photosensitive resin is removed in step h2). Steps a2) and b2) correspond to steps a) and b). The composite of the first layer of insulating photosensitive resin capable of inducing a metal film in later processing is Cu, Co,
It is selected from oxides of Cr, Ni, Pb, and Sn. Step c) for forming the conductive path and the micro via includes steps c2), d2), e2), f2), g2), and h
It is a sequence (or a series of steps) of the steps consisting of 2).

The method for performing each step is as described above. In a manner according to the second embodiment, an insulating photosensitive resin that appears (or is created) in the photosensitive via 204, ie, the metallizable portion 202 or potentially metallizable portion. The via in step b
It is formed in 2). In step c2), according to one of the two methods (preferably the first method), with the aid of a salt of a noble metal in an acidic medium, the metal coating is applied over the available surface of the first layer A possible layer 205 is formed. In step d2), a metal coating is performed to obtain a continuous metal layer 206 over the available surface.
The metal coating is preferably performed electrolytically in an acidic medium. In step f2), selective protection is obtained by creating vias 208 in the second layer, so that the second layer of photosensitive resin remains in place on the surface of the metal layer. Therefore, the protection 209 of the second layer in the region of the via 204 and the protection 210 of the second layer on the portion where the via of the first layer does not exist are left.

In step g2), the portion of the metal layer exposed in step f2) is removed. Removal may be removed by etching or dissolution using methods known in the art. In general, the part to be removed is that part of the metal layer which is not in contact with the part exposed in step b2) before the metal coating. Preferably, the removal is performed by etching in an acidic medium. After the removal of the second layer of photosensitive resin in step h2), the surface of the resulting circuit consists of: a first layer of photosensitive resin 214; A portion 212 of a conductive path on the surface; a portion of a conductive via 213 on a surface of the first layer in contact with the microvia 211;

(Embodiment 3) According to the third embodiment,
The method comprises the following steps: a3) Cu, Co, Cr, Ni, Cu on the substrate 301 with the metallized part 302 and / or the potential metallized part.
Pb, Sb and Sn oxides and metal oxide particles which are mixtures thereof and, depending on the state, an insulating photosensitive resin containing one or more non-conductors and an inert filler B3) exposing and developing the first layer to selectively expose metallizable or potentially metallizable portions of the substrate; c3) Forming a metallizable sublayer 305 on the surface of the first layer of photosensitive resin and the exposed portion of the substrate: contacting with a solution of a salt of a noble metal that can be reduced by metal oxide particles Or by contacting the metal oxide particles with a reducing agent capable of reducing; d3) electrochemically depositing the final metal layer 306 to the first layer and to the exposed portions of the substrate. , And ( E3) forming a second layer 307 of a photosensitive resin that does not contain metal oxide particles on the metalized surface; f3) selectively exposing certain portions of the metal layer G3) Reinforcing the metal layer in the area of the portion exposed in step f3) with a metal film; h3) Refining the metal layer in which a specific portion is reinforced Removing the second layer of photosensitive resin to expose; i3) etching the metal layer to remove the entire unreinforced portion of the layer.

The third embodiment corresponds to a metal film following a panel-type process using patterned reinforcement. In the case of the third embodiment, the second layer of photosensitive resin is removed in step h3). Step a
3) and b3) correspond to steps a) and b). The composite of the first layer of insulating photosensitive resin capable of inducing a metal film in later processing is Cu, Co, Cr, Ni, Pb, and Sn
Selected from oxides of Step c) for forming the conductive path and the micro via includes steps c3), d3),
It is a sequence of steps (or a series of steps) consisting of e3), f3), g3), h3) and i3).

The method for performing each step is as described above. In a manner according to the method of the third embodiment, the photosensitive vias 304, ie vias in the insulating photosensitive resin which appear on the metallizable or potentially metallizable part 302, are step b3). Is formed. In step c3), according to one of two methods (preferably the first method), with the aid of a salt of a noble metal in an acidic medium, a metal coating is applied over the available surface of the first layer. A possible sublayer 305 is formed. In step d3), a continuous metal layer 306 over the available surface
In order to obtain, a metal coating may be implemented. Vias 308 to expose the metal layer in the area of the photosensitive via 304 and vias 309 to expose the metal layer in the area of the first layer where no photosensitive via is present, by means of step f3). , Provides selective protection.

In step g3), these parts of the metal layer exposed in step f3), ie the areas of vias 308 and 309, are reinforced. Reinforcement 310 may be, for example, a simple and easily etchable metal film of similar properties as the metal layer, and is preferably obtained by an electrolytic metal coating. The thickness of the metal layer in the reinforced portion is greater than the thickness of the unreinforced portion. The reinforcement may also be composed of a metallic material that cannot be easily etched, such as gold.

After the photosensitive resin layer is removed in step h3), all the metal layers in the unreinforced portions are removed.
The metal layer is etched in step i3) to leave a metal film on the reinforced part. This is, for example,
Performed by differential etching. The etching is performed, for example, in an acidic medium. The surface of the resulting circuit consists of: a first layer 31 of photosensitive resin.
4; part 312 of the conductive path on the surface of the first layer not in contact with the substrate; microvia 31 in contact with the substrate
1: part 313 of the conductive path on the surface of the first layer in contact with the microvia.

(Embodiment 4) The level of the generated circuit is generated by a similar sequence of steps.
Two circuit levels may be supported. One embodiment of the second circuit level is described below and is illustrated in FIGS. 4 (a)-(c).

In this example, the operation is performed according to a method similar to that of the first embodiment. In step a4),
A first layer of photosensitive resin is formed on a circuit-level surface obtained by one of the embodiments described above. It consists of a preceding circuit level (here referred to as the lower level), a layer 401 of insulating photosensitive resin containing metal oxide particles, and conductive paths and microvias 402,40.
Have three. In step b4), the appropriate of the vias or microvia portions 402, 403 and a potential metallization portion 405 consisting of a portion of the lower level first layer (the lower level second layer has been removed). The first layer of resin is exposed and developed to form photosensitive vias 406, 407 that appear (or are created) in different locations.

In steps c4) and d4), a second layer of photosensitive resin is applied to form a selective protection,
Exposure and further exposure.

In step e4), a metallizable sublayer is formed in the manner described above. In addition, sublayers are formed on the unprotected surface of the first layer and on the potential metallization surface 405. Step f4 for metal coating
Will be implemented. Conductive paths and microvias 410, 41
1, 412 are formed. In step g4), the second layer of the photosensitive resin is removed.

[0100]

According to the present invention, the planarity in a multilayer circuit is improved by reducing the expansion (or bulging) phenomenon of the photosensitive resin, and the positioning between circuit levels and the arrangement of micro vias can be reduced. It becomes possible to be more accurate than the multilayer circuit of the technology. As a result, the number of nonstandard products generated during manufacturing can be reduced, and the reliability and life of the products can be improved.

[Brief description of the drawings]

FIG. 1 shows a circuit at various steps of a process according to a first embodiment method.

FIG. 2 shows a circuit at various steps of a process according to a second embodiment method.

FIG. 3 shows a circuit at various steps of a process according to a third embodiment.

FIG. 4 illustrates a multilayer circuit at various steps of the process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Substrate 102 Metal film part 103 First layer of photosensitive resin 104 Photosensitive via 105 Second layer of photosensitive resin 106 Via 107 Via 108 Sublayer 109 Metal layer (or metal interconnection) 110 Micro via 111 Conductive path on the surface of the layer (not in contact) 112 Conductive path on the surface of the layer (in contact with the microvia) 113 First layer of photosensitive resin 201 Substrate 202 Metal coating portion 203 First layer of photosensitive resin 204 Photosensitive via 205 Sublayer 206 Metal layer 207 Second layer of photosensitive resin 208 Via 209 Protection by second layer 210 Protection by second layer 211 Microvia 212 Conductive path on layer surface 213 Conductive path on layer surface 213 Photosensitive First layer of resin 301 Substrate 302 Metal film portion 303 First layer of photosensitive resin 304 Optical via 305 Sublayer 306 Metal layer 307 Photosensitive resin second layer 308 Via 309 Via 310 Reinforcement of metal 311 Micro via 312 Conductive path on surface of layer 313 Conductive path on surface of layer 314 First layer of photosensitive resin 401 Insulating photosensitive resin layer 402 Micro via 403 Micro via 405 Metal film surface 406 Photo sensitive via 410 Micro via 411 Conductive path 412 Micro via

Continued on the front page F term (reference)

Claims (21)

[Claims] 1. A method for fabricating a multi-layer interconnect circuit comprising metal conductive paths and microvias, wherein the steps for fabricating at least one level include: a) a metallizable surface and (Or) forming a first layer of an insulative photosensitive resin on a substrate having a potentially metallizable portion, containing a compound capable of inducing a metallization in subsequent processing. B) exposing and developing the first layer to selectively expose metallizable and / or potentially metallizable portions of the substrate; c) selectively protecting; While using the second layer of photosensitive resin to be formed, a metal film is used to form metal conductive paths and microvias on the surface of the first layer of insulating photosensitive resin and the portion exposed in step b). Do: consisting of
The method of claim 1 further comprising removing the second layer of photosensitive resin to produce a desired level. 2. The substrate is at a lower circuit level, the metallizable portion is a metal conductive path or microvia, and the potentially metallizable portion is an insulating material for creating the lower level. The method according to claim 1, wherein the non-metallic film portion has a first layer of the photosensitive resin. 3. The method according to claim 1, wherein the second layer of the photosensitive resin does not contain a compound capable of inducing a metal film in a subsequent treatment. 4. The composition capable of inducing a metal film in a subsequent treatment is selected from oxides of Cu, Co, Cr, Ni, Pb, Sb, and Sn, and mixtures thereof. The production method according to any one of claims 1 to 3, wherein 5. The method according to claim 1, wherein the first layer of the resin comprises an inert, non-conductive filler. 6. The method according to claim 6, wherein (a metal film of) the surface of the first layer of the photosensitive resin or the exposed portion of the first layer of the photosensitive resin.
The method according to claim 1, wherein the metal coating is performed on a sublayer capable of metal coating. 7. A metal oxide selected from the group consisting of oxides of Cu, Co, Cr, Ni, Pb, Sb, and Sn, and mixtures thereof, wherein the compound capable of inducing a metal film in a later treatment is used. Wherein the sublayer is formed by contacting the first layer of the photosensitive resin or a portion of the first layer of the photosensitive resin with a solution of a salt of a noble metal that can be reduced by the oxide particles. The method according to claim 6, wherein: 8. The method according to claim 7, wherein the solution of the noble metal salt is an acidic solution. 9. Salts of the noble metal is C1 ^-, NO ^- _3, and CH ₃ COO ^- Au having a counterion selected from, Ag, Rh, Pd, Os , I
The method according to claim 6, wherein the method is selected from the group consisting of r and Pt. 10. A metal oxide selected from the group consisting of oxides of Cu, Co, Cr, Ni, Pb, Sb and Sn, and mixtures thereof, capable of inducing a metal film in a subsequent treatment. Wherein the sublayer is formed by contacting the first layer of the photosensitive resin or a part of the first layer of the photosensitive resin with a reducing agent capable of reducing oxide particles. The method according to claim 6, wherein 11. The method according to claim 6, wherein the particles of the first layer of the photosensitive resin are exposed before the sublayer capable of being metal-coated is formed. Production method. 12. The method according to claim 1, wherein the metal coating is performed electrochemically and / or electrolytically. 13. The method according to claim 1, wherein the metal coating is carried out electrolytically in an acidic medium. 14. The method according to claim 1, wherein step c) comprises: c1) exposing the first layer and the exposed parts of the substrate to a composition-free photosensitive material intended for selective protection and capable of inducing a metal film in a subsequent treatment. Forming a second layer of conductive resin; d1) exposing and developing the second layer to selectively expose certain portions of the first layer and certain portions of the substrate; e1) Forming a metallizable sublayer in a method: contacting a solution of a salt of a noble metal reducible by metal oxide particles; or contacting metal oxide particles with a reducible reducing agent; f1) Electrochemically and / or electrolytically depositing a metal layer on the first layer and the exposed portions of the substrate; g1) removing the second layer of photosensitive resin. 14. The method as claimed in claim 7, wherein: Method of manufacturing a crab described. 15. The method according to claim 1, wherein step c) comprises: c2) forming a metallizable sublayer on the surface of the first layer of photosensitive resin and the exposed part of the substrate in the following manner: by metal oxide particles Contacting with a solution of a reducible noble metal salt; or contacting the metal oxide particles with a reducing agent capable of reducing; d2) attaching a metal layer to the first layer and to the exposed portions of the substrate E2) forming a second layer of a photosensitive resin intended to provide selective protection on the metallized surface to provide an electrochemical and / or electrolytic metallization; F2) exposing and developing the second layer to selectively expose certain portions of the metal layer; g2) removing the metal layer from the portions exposed in step f2); h2) exposing Remove the second layer of conductive resin Rukoto, characterized in that it consists, production method according to any of claims 7 13. 16. Step c) comprises: c3) forming a metallizable sublayer on the surface of the first layer of photosensitive resin and the exposed part of the substrate in the following manner: by metal oxide particles Contacting with a solution of a reducible noble metal salt; or contacting the metal oxide particles with a reducing agent capable of being reduced; d3) final metal layer exposed on the first layer and the substrate An electrochemical and / or electrolytic metallization to adhere to the part; e3) the metallized surface contains no compounds capable of inducing a metallization in a subsequent treatment Forming a second layer of a photosensitive resin; f3) exposing and developing the second layer to selectively expose specific portions of the metal layer; g3) exposed by a metal coating in step f3). Of the area H3) removing the second layer of photosensitive resin to expose certain portions of the reinforced metal layer; i3) removing the entire unreinforced portion of the layer 14. The method according to claim 7, further comprising etching a metal layer. 17. The method of claim 1, further comprising treating the first layer of photosensitive resin to obtain a B-stage resin. 18. The method according to claim 17, wherein the processing step is a curing step performed after the second layer of the photosensitive resin is removed. 19. The substrate according to claim 1, wherein the substrate is a rigid printed circuit having a conductive path on its surface.
9. The production method according to any one of the above items 8. 20. The method according to claim 1, which is used for producing printed circuits and multilayer modules having a high integration density. 21. A circuit provided with a conductive path and a micro via which can be manufactured by the manufacturing method according to claim 1.