TW201428923A - Semiconductor device and its process of manufacture - Google Patents

Abstract

The present invention relates to a semiconductor device comprising a semiconducting substrate having interconnection structures or through silicon vias in which the surface of the structures is covered with a polymer layer and then with a metal layer, the polymer layer simultaneously fulfilling the role of electrical insulator between the semiconductor and the metal layer and the role of barrier to the possible migration, toward the semiconducting substrate, of the metal ions originating from the metal layer. The invention also relates to a process for the manufacture of this device. Application: Metallization of very thin interconnections and of through silicon vias in 3D integrated circuits.

Description

Semiconductor device and method of manufacturing same

SUMMARY OF THE INVENTION The present invention generally relates to a semiconductor device having a simplified structure that does not include a metal material that forms a barrier to diffusion of metal ions from the conductive layer to the semiconducting substrate between the insulating layer and the conductive layer.

The present invention is also directed to a method of fabricating the semiconductor device in which the surface of the substrate is coated with an electrically insulating layer and a metal layer. The method includes a limited number of stages compared to prior art methods.

The present inventors have found an application for the metallization of tantalum perforations (TSV) and interconnect components of printed circuits by copper primarily in the field of microelectronics.

Microelectronic devices include two types of conductive structural networks: interconnects that are in the form of relatively thin lines and that run on the surface of a semiconducting substrate to electrically connect transistors and other components in the same layer. And 矽 perforations, which are used to electrically connect a plurality of layers of substrates for a three-dimensionally integrated longitudinal cavity having a larger size.

These structures intended for electrical conduction are typically filled with copper. It is insulated from the semiconductor crucible support by the insertion of a dielectric material. However, the conductive metal (specifically, copper) deposited in such structures has a tendency to easily diffuse into the substrate (generally cerium oxide or doped cerium). Therefore, it is desirable to insert a barrier material for diffusion of metal ions between the conductive metal and the semiconducting substrate to prevent any diffusion of the metal into the adjacent dielectric material. If the metal migrates to the sensitive semiconducting region, this greatly changes its properties and disables the semiconductor device.

Thus, a method of metallizing a conductive structure in a semiconductor device typically includes a series of stages including: - etching of lines and germanium vias in a germanium wafer; - deposition of an insulating dielectric material layer in an etched structure; Deposition of a barrier layer or liner for preventing migration of copper to the insulating layer; - filling the structures by electrodeposition of copper; and - removing excess copper from the surface of the wafer by chemical mechanical polishing of the surface of the substrate.

In this method, it is therefore necessary to deposit on the insulator a barrier layer that prevents migration of metal atoms generated under the effect of heat and current density applied during operation of the device. This layer, referred to as "a barrier for diffusion or migration of copper" or simply "barrier", consists of a metal or metal alloy such as titanium nitride, tantalum nitride or nickel/boron alloy.

The application FR 2 933 425 describes the preparation of a stack having an insulating layer, a barrier layer and subsequently a copper seed layer on the surface of a p-doped ruthenium substrate comprising a precursor cavity before the ruthenium perforation. Poly(4-vinylpyridine) used as an insulating material was deposited on the crucible by electrografting. Nickel/boron (a barrier material for diffusion of copper) is interposed between the poly(4-vinylpyridine) and the copper layer.

Prior art methods for metallizing conductive structures employ a deposition phase of a barrier layer or liner for preventing migration of copper to the crucible. Thus, advantageously, the manufacturing methods of such devices can be simplified to reduce the processing time and amount of starting materials required to fabricate such devices.

Accordingly, it is an object of the present invention to solve the technical problem in that a semiconductor device which is reliable over time during its operation is manufactured at low cost. The goal is to remove the stage of coating the substrate with a metal barrier material as practiced in the prior art.

It has been discovered (and this discovery forms the basis of the present invention) that some dielectric compounds exhibit barrier properties to the electromigration of metal ions, thereby (as opposed to all expectations) providing a need to deposit a metal barrier material on a dielectric material. A device that resists the layer and operates correctly at voltage. The dielectric compounds identified in the context of the present invention simultaneously satisfy the insulating effect and Barrier function.

In semiconductor integrated circuits, such as computer chips with high power, high storage density, and low loss, it has become necessary to reduce the size of such structures. The reduction in wafer size and the increase in circuit density therefore require miniaturization of the interconnect.

However, when the trenches reach an oversized size, it becomes difficult (actually impossible) to deposit several layers having different materials due to the lack of sufficient space in the structures. In order to fill a thinner interconnect structure, it is necessary to remove some intermediate material layer between the substrate and the metal.

Another object of the present invention is to solve the technical problem by providing a novel device having a very fine interconnect (such as an interconnect structure having a width of less than 50 nm (e.g., 7 nm, 10 nm, or 15 nm).

To this end, the present invention provides a novel device that does not include a metal barrier layer. The absence of a metal barrier saves space and saves the conductivity of the etched structure that must be filled with conductive metal.

Accordingly, the present invention is directed to a semiconductor device comprising a semiconducting substrate having an interconnect or tantalum perforated structure, wherein the surface of the structures is successively covered by a polymer layer and a metal layer, regardless of whether the device is placed under voltage Also under the effect of thermal stress, the polymer layer simultaneously satisfies the action of the electrical insulator between the semiconductor and the metal layer and the barrier to possible migration of metal ions from the metal layer to the semiconducting substrate. .

More particularly, the present invention relates to a device comprising a semiconductive or conductive substrate having an interconnect structure or a perforated substrate, wherein the surface of the structure of the semiconductive substrate is covered by an organic polymer layer, The organic polymer layer itself is covered and in contact with the metallic copper layer, characterized in that the polymer layer simultaneously satisfies: - the role of an electrical insulator between the semiconductor and the metal layer, and a barrier to the migration of metal ions from the metal layer to the semiconducting substrate, and characterized in that the device does not comprise a metal having a barrier to migration of metal ions from the metal layer to the semiconducting substrate The layer of material of nature.

The device exhibits the advantage of not including the prior art metal intercalation between the electrically insulating layer and the conductive metal to limit the electromigration of the metal to the tantalum substrate (a barrier for diffusion of metal ions).

The device exhibits the advantage of not including a barrier layer containing a layer of material having a metallic property selected from the group consisting of ruthenium, titanium, nickel and cobalt. In order to establish a barrier between the tantalum substrate and the conductive metal, the layer used in the prior art is generally made of tantalum (Ta), titanium (Ti), nickel (Ni), cobalt (Co), nickel/tungsten (NiW). Alloy, cobalt/tungsten (CoW) alloy, nickel/boron (NiB) alloy, cobalt/boron (CoB) alloy, nickel/phosphorus (NiP) alloy, cobalt/phosphorus (CoP) alloy, tantalum nitride (TaN), nitrogen Titanium (TiN), titanium/tungsten (TiW) alloy, tungsten nitride/tungsten carbide (WCN) or a combination of these materials.

According to a second aspect, the title of the present invention is a method of coating a conductive or semiconductive substrate, such as a tantalum substrate, comprising the following stages: - coating the first layer with an electrically insulating film Substrate, coating the first layer with a second layer in contact with the first layer and forming a conductive metal layer, characterized in that the first layer comprises at least one which is stable at high temperatures and contains hydrogen bonds via ionic bonds Or a Van der Waals bond polymer that combines groups of metal ions from the metal layer, which polymer thus exhibits a barrier effect of diffusion of such metal ions toward the substrate.

Figure 1 shows the front surface TOF-SIMS analysis spectrum of the P4VP-Cu sample of the present invention after annealing at 400 °C for 2 hours.

Figure 2 shows the P4VP-Cu sample of the present invention before and after annealing at 400 ° C for 2 hours. The breakdown voltage is measured.

The first insulating layer is a layer that resists migration of metal ions of the metal layer to the conductive or semiconductive substrate under the effect of current.

It may have a thickness in the perforated structure of at least 80 nm and preferably between 100 and 500 nm.

The insulating layer comprises or consists of a polymer which is advantageously stable at elevated temperatures, which advantageously stabilizes at high temperatures means that the polymer loses its weight after exposure to a temperature between 100 and 400 ° C for at least one hour. less than 1%. A polymer in the meaning of the present invention is a macromolecule composed of repeating units. It comes from the reaction of one or two molecules known as monomers. The single systems react with one another by addition or condensation. The organic polymer in the meaning of the present invention contains carbon and hydrogen.

Preferably, the organic polymer is crosslinked and bonded to the substrate by covalent bonding. The covalent bond can be formed, for example, by electrografting during the polymerization of the polymer in the presence of a substrate.

The polymer used in the context of the present invention contains a free functional group which can form a bond with a metal ion. On the other hand, polymers used as insulators in the prior art, such as fluoropolymer-(CF ₂ ) _n -, polyoxyl polymer, poly-p-xylylene, and polyimine, do not include such functional groups. The polymers used in the context of the present invention may be bonded to metal ions via non-covalent bonds such as ionic, hydrogen or van der Waals properties.

According to one embodiment, the polymer comprises groups that can mate with metal ions from the metal layer and, therefore, exhibit a barrier effect of diffusion of such metal ions toward the substrate.

The polymer may be selected from polymers comprising one or more functional groups selected from the group consisting of primary amines, secondary amines, enamines, alcohols, thiols, carboxylic acids, non-aromatic heterocyclic rings, and aromatic heterocyclic groups ( Specifically, a nitrogen-containing aromatic heterocyclic ring such as pyridine, pyrrole or thiophene).

For example, the polymer is obtained from at least one polymerizable carbon-based monomer comprising at least one of the above functional groups.

A monomer which can be chain-polymerized by a radical route is preferred, such as, for example, a vinyl monomer. Accordingly, the monomers will advantageously be selected from water-soluble vinyl monomers comprising at least one functional group that can form a non-covalent bond with a metal ion.

The monomers will advantageously be selected from poly(vinylamine), in particular vinyl derivatives selected from amines, such as: - primary aliphatic amines, in particular ethylamines, cyclohexylamines or cyclohexanes Amine;- a secondary aliphatic amine, in particular pyrrolidine; a tertiary aliphatic amine, in particular hydroxyethyldiethylamine or triethylenediamine; - an aromatic amine, in particular 1,2 -diaminobenzene or 3,5-dimethylaniline; - nitrogen-containing heterocycle, specifically pyridine, 2,2'-bipyridine, 8-hydroxyquinoline sulfonic acid, 1,10-morpholine, 3 , 5-dimethylpyridine or 2,2'-bipyrimidine; - anthracene, specifically a diketene oxime, specifically a polymer of a nitrogen-containing vinyl aromatic heterocycle.

In the poly(vinylamine) used in the context of the present invention, the nitrogen atom is not bonded to the vinyl group, so that the nitrogen atom remains available for bonding to the metal ion.

For example, the single systems are selected from the group consisting of unsaturated nitrogen-containing carbon-based monomers and their sulfur-based analogs, including: - vinyl pyridines such as 2-vinyl pyridine or 4-vinyl pyridine, and lower grades (C) _a C-substituted vinyl pyridine of ₁ - C ₈ ) alkyl group, such as 2-methyl-5-vinyl pyridine, 2-ethyl-5-vinyl pyridine, 3-methyl-5-vinyl pyridine, 2,3-Dimethyl-5-vinylpyridine and 2-methyl-3-ethyl-5-vinylpyridine; -vinylquinoline, vinylpyrrolidone, vinylimidazole, vinylcarbazole And vinyl amber imine.

In one embodiment, the monomer is 4-vinylpyridine or 2-vinylpyridine.

The monomers may also be selected from: - monomers comprising carbon-carbon double bonds bonded to a carboxyl group, such as acrylic acid, methacrylic acid Acid, itaconic acid, maleic acid, fumaric acid and sodium, potassium, ammonium or amine salts thereof, - a monomer comprising a carbon-carbon double bond bonded to a guanamine group of the above carboxylic acid, and specifically a propylene oxime Amines and methacrylamides and N-substituted derivatives thereof, monomers comprising carbon-carbon double bonds bonded to ester groups of the above-mentioned carboxylic acids, such as 2-hydroxyethyl methacrylate, glycidyl methacrylate Esters, dimethyl- or diethylamino(ethyl) acrylates and their salts, and quaternized derivatives of such cationic esters, such as, for example, propylene oxyalkylene chloride Ethyltrimethylammonium, 2-propenylamido-2-methylpropanesulfonic acid (AMPS), vinylsulfonic acid, vinyl phosphoric acid, vinyl lactic acid and salts thereof, acrylonitrile, N-vinylpyrrolidine Ketones, vinyl acetates, N-vinyl imidazolines and their derivatives, N-vinylimidazoles and derivatives of diallyl ammonium type (such as dimethyl diallyl ammonium chloride, dimethyl bromide) Diallyl ammonium or diethyl diallyl ammonium chloride).

According to a particular embodiment, the wall of the structure of the device of the invention is covered by a layer of poly(4-vinylpyridine) having a thickness of between 100 and 400 nm, the poly(4-vinylpyridine) layer The self is covered by copper, which forms the seed layer or filling layer of the structures.

The insulating dielectric layer can be deposited by a dry route or by a wet route to obtain a uniform insulating layer.

The polymer is preferably deposited on the substrate by electrografting or spin coating.

Electrografting is a wet pathway deposition technique based on the initiation of electroactive monomers on the surface to be coated and subsequent polymerization by electrical induced chain growth.

In general, electrografting requires: - on the one hand, a liquid solution comprising an initiator compound and the above monomers; and - on the other hand, a polymerization reaction on the surface of the substrate to be coated and formation of a polymer Electrochemical scheme of the membrane.

According to one of the electrografting processes described in the application FR 2 933 425, the polymer is preferably deposited on a substrate having blind holes. One of the methods of the present invention comprises: a) contacting the surface with a liquid solution comprising: a protic solvent, preferably water; - a diazonium salt, preferably a 4-nitrodiazobenzene salt; - a polymerizable monomer soluble in the protic solvent, preferably a vinyl pyridine; - at least one acid sufficient to stabilize the pH of the solution to a value below 7 (preferably below 2.5) to stabilize the diazonium salt; b) to polarize the surface according to a potential- or electrochemical-pulse mode .

In general, the polarization of the surface to be covered by the membrane is based on a pulse pattern, each of which is characterized by: - a total period P between 10 ms and 2 s; - between 0.01 and 1 s The polarization time T is _{turned on} , during which a potential difference or current is applied to the surface of the substrate; and - at zero potential or current, there is a break time of 0.01 to 1 s.

The conductive or semi-conductive substrate can be a flat surface or have a surface that is etched or cavity-embedded by interconnects or turns, respectively.

The depth of the cavity varies as a function of position and as a function of the turns of the crucible that need to be formed in the germanium wafer. Thus, it can vary from 1 to 500 microns, typically from 10 to 250 microns. For example, the cavities have a diameter in their opening ranging from 200 nm to 200 microns, typically from 1 to 75 microns.

According to one embodiment of the invention, the openings of the cavities are in the range of 1 to 10 microns, however the depth is in the range of 10 to 50 microns.

The width of the interconnect is typically less than 200 nm and can reach tens of nanometers. The present invention can, in particular, metallize very fine lines having a width of less than 50 nm (e.g., 7 nm, 10 nm, or 15 nm).

The metal layer may comprise copper, tin, aluminum, gold or silver.

Copper is preferably used as a metal because it exhibits excellent electrical conductivity and electromigration The high resistance of the image, that is, the weak migration of copper atoms under the effect of current density, which can be the main cause of failure.

The metal layer may be a thin layer of copper metal (referred to as a seed layer) having a thickness of about several tens to several hundreds of nanometers. It is also possible to fill the entire volume of the actuator cavity before etching the etched wire or the ruthenium.

The metal layer can be deposited by autocatalytic (or electroless) or by gas phase methods (PVD or physical vapor deposition and CVD or chemical vapor deposition, ALD or atomic layer deposition, respectively).

A method for autocatalytic deposition of copper is described, for example, in document US 2007/0261594 (LAM Patent).

A better understanding of the present invention will be obtained upon reading the description of the following non-limiting examples taken at the laboratory scale.

Unless otherwise indicated, this example was carried out in ambient air under standard temperature and pressure conditions (about 25 ° C at 1 atm) and the reactants used were purchased directly without additional purification.

The tantalum substrate used in this example exhibited a resistivity value between 1 and 100 Ω.cm.

Instance

A-Preparation of poly(4-vinylpyridine) (P4VP) film on a flat P-doped germanium substrate

Substrate:

In this example the substrate is used having a resistivity of 20Ω.cm, 4cm length of the edge (4 × 4cm) and a P- doped silicon coupons thickness of 750μm.

Solution:

The electrografting solution used in this example was introduced by introducing 5 ml of 4-vinylpyridine (4-VP, 4.5 x 10 ^-2 mol) into 95 ml of 1 M HCl and then 236 mg of 4-nitrodiazobenzene tetrafluoroborate. (DNO2, 1 × 10 ^-3 mol) An aqueous solution prepared by adding to the mixture thus formed.

The solution was degassed by a stream of argon for 10 minutes before using the solution.

Program:

In order to carry out electrografting on the crucible substrate, a system consisting of: - a sample holder equipped with a member for rotating at a predetermined speed and shaped to support the substrate, is formed, and the combination thus formed is intended to be a work Electrode; - carbon sheet to be used as counter electrode; - stable power supply and device for electrical contact; - light source (halogen lamp, 150W) placed in front of the P-doped erbium sample to maximize the surface of the sample Light intensity. To this end, the lamp was placed at a distance of about 10 cm from the surface of the sample. The sample was illuminated for the entire duration of the experiment.

The electrografting of P4VP on the surface of the ruthenium substrate is carried out by applying a potential to the substrate which is previously set at a rotation speed of 40 to 100 rev.min ^-1 (in this example, 60 rev. min ^-1 ) The -pulse" electrochemical scheme is carried out for a predetermined period of about 10 to 30 minutes (in this example, 15 minutes), wherein: - a total period P between 0.01 and 2 seconds (in this example, 0.220) Seconds; - a polarization time T between 0.01 and 1 second (in this example, 0.02 seconds) during which a potential difference of 1V to 10V is applied to the surface of the substrate (in this example, the cathode potential is -19V) ); and - a disconnection time (expressed as T- _off ) of 0.01 to 1 second at zero potential (in this example, 0.200 seconds).

It is understood that the duration of this electrografting stage depends on the desired thickness of the insulating polymer layer. This duration can be readily determined by those skilled in the art, and the growth of the layer is a function of the applied potential difference.

Under the above conditions, a polymer (P4VP) layer exhibiting a thickness of 200 nm was obtained.

Once the electrografting was completed, the sample was washed several times with water, then dried under a stream of argon and then dried in an oven under an inert atmosphere for 10 min (250 ° C).

Characterization:

Scanning electron microscopy (SEM) analysis shows homogeneous polymer film in P-doped 矽 The presence on the surface of the sample.

Deposition of B-copper and confirmation of barrier properties of P4VP film on copper diffusion

The deposition of 200 nm of copper by PVD was carried out on a previously covered P4VP coated substrate.

After the sample was placed at a temperature of 400 ° C for 2 hours, the structure of the polymer was observed to be undegraded (weight loss of the sample was less than 1% by weight) and copper did not migrate into the full thickness of the polymer. To this end, an in-depth TOF-SIMS analysis was performed to see if copper was present in the polymer. The analysis was performed after polishing and the sample was analyzed via the back surface. Figure 1 shows the distribution of the components constituting the sample (i.e., the polymers P4VP (carbon C) and copper (Cu)). A very pronounced interface was observed between the copper and the polymer, reflecting the very weak interpenetration of the two materials. The obtained spectrum is presented in Figure 1.

Trace copper was only found in 10 nm above the P4VP film.

The P4VP-Cu sample was also electrically tested before and after annealing at 400 °C for 2 hours. The breakdown voltage of the P4VP insulator was measured by making a contact with a drop of mercury on a copper contact deposited on the surface of the P4VP. The results obtained are summarized in Figure 2.

A slight decrease in breakdown voltage (1.3 MV/cm) was observed, which reflects the slight penetration of copper into the polymer layer.

Since the P4VP film is resistant to the diffusion of copper ions, the P4VP film can thus be used in a semiconductor device.

Claims (11)

A device comprising a semiconducting or conductive substrate having an interconnect or tantalum perforated structure, wherein the surface of the structure of the semiconducting substrate is covered by an organic polymer layer that is itself covered and Contact with a metallic copper layer, characterized in that the polymer layer simultaneously satisfies the role of an electrical insulator between the semiconductor and the metal layer, and - the migration of metal ions from the metal layer to the semiconductive substrate Barrier effect, characterized in that the device does not comprise a layer of material having a metallic property that forms a barrier to migration of metal ions from the metal layer to the semiconducting substrate, and characterized in that the organic polymer is obtained from One or more vinyl monomers that can bind non-polymerizable functional groups of copper ions from the metal layer via ionic bonds, hydrogen bonds, or van der Waals bonds. The device of claim 1, wherein the layer of material having a metallic property forming the barrier comprises a metal selected from the group consisting of ruthenium, titanium, nickel, and cobalt. The device of claim 1, wherein the material layer of the barrier metal layer is made of tantalum (Ta), titanium (Ti), nickel (Ni), cobalt (Co), nickel/tungsten (NiW) alloy, cobalt/ Tungsten (CoW) alloy, nickel/boron (NiB) alloy, cobalt/boron (CoB) alloy, nickel/phosphorus (NiP) alloy, cobalt/phosphorus (CoP) alloy, tantalum nitride (TaN), titanium nitride (TiN) ), titanium/tungsten (TiW) alloy, tungsten nitride/tungsten carbide (WCN) or a combination of these materials. The device of claim 1, wherein the organic polymer is obtained from one or more selected from the group consisting of a primary amine, a secondary amine, an enamine, an alcohol, a thiol, a carboxylic acid, an aromatic heterocyclic ring, and a non-aromatic heterocyclic group. A group of non-polymerizable functional groups of vinyl monomers. The device of claim 1, wherein the organic polymer is bonded to the semiconductive substrate via a covalent bond. The device of claim 1, wherein the organic polymer is crosslinked and stabilized at a high temperature. The device of claim 1, wherein the organic polymer is obtained by polymerization of vinyl pyridine. The device of claim 1, wherein the device comprises a perforated structure, and the wall of the structure of the semiconductive substrate is poly(4-vinylpyridine) organically polymerized to a thickness of between 100 and 400 nm. Covered by the layer, the poly(4-vinylpyridine) layer itself is covered by a layer of copper that forms a seed layer having a thickness of less than 100 nm or a layer filling the volume of the structures. A method of manufacturing the apparatus of claim 1, comprising the steps of: - coating the substrate with an organic polymer layer forming an electrically insulating film, - coating the organic layer with a conductive metallic copper layer in contact with the polymer layer Polymer layer. The method of claim 9, wherein the organic polymer layer is deposited on the semiconductive substrate by electrografting or by spin coating. The method of claim 9, wherein the metal layer is deposited by an autocatalytic (or electroless) process or a gas phase process (PVD, CVD, ALD).