RU2694289C1 - Method of forming copper distribution with a thick cobalt-containing insert in the structure of devices operating based on magnetic tunnel junction - Google Patents

Abstract

FIELD: manufacturing technology.

SUBSTANCE: disclosed is a method of forming copper distribution with a thick cobalt-containing insert in the structure of devices operating based on magnetic tunnel junction. As a result of the method implementation, according to 3 versions, a groove with copper distribution and a cobalt insert without defects is formed. Method includes the following steps in the following sequence: etching the groove in silicon dioxide on silicon; deposition of cobalt insert; copper inoculating layer deposition. According to the first version of CMP invention seed layer copper and cobalt process is divided into 2 stages. At the first step, after depositing the copper seed layer using the CMP, cobalt is completely removed from the SiO₂ top surface. Thereafter, copper is galvanically deposited. At the second stage, the CMP is performed by removing copper from the upper surface of the groove and the upper surface of SiO₂. According to the second version of the invention, the cobalt insert is formed between two barrier layers of Ta (TaN) and/or Ti (TiN) with only one CMP process and removal of cobalt from the upper surface of SiO₂. According to the third version of the invention, at the beginning, creating a standard structure with a groove filled with a cobalt insert, depositing a thick seed layer of copper, without further use of the electrochemical deposition of copper to thickness of more than 2,000 nm, which actually enables to avoid the process of galvanic copper deposition, use only one CMP process to achieve the result, during which copper and cobalt are removed from the surface of silicon oxide, forming a groove with copper distribution and cobalt inserts without defects.

EFFECT: invention provides reduced number of defects in the process of formation of distribution.

9 cl, 9 dwg

Description

TECHNICAL FIELD

The method of forming copper wiring with a thick cobalt-containing inlay in the structure of devices operating on the basis of a magnetic tunnel junction relates to the manufacturing techniques of semiconductor devices, for example, the type of MRAM (magneto-resistive random-access memory), magnetic sensors, etc.

BACKGROUND

For the manufacture of some devices operating on the basis of magnetic tunnel junctions, the magnetic field lines generated by the current passing through the copper grooves are used to switch the direction of the magnetization of the storage layer. The lines of force of the magnetic field that occurs when current flows through the grooves are used to control the operation of MRAM cells and magnetic sensors. To localize the magnetic field in the cell in a certain direction, a ferromagnetic insert is formed on the side walls of the copper groove. The ferromagnetic tab plays the role of a screen (mirror) for a magnetic field. Due to this, the distribution of the magnetic field is not uniform along the perimeter of the copper conductor, but is directed strictly to the magnetic cell. Local directivity reduces the amount of current flowing through the conductor, because the magnitude of the magnetic field, sufficient to switch the cell, in the case of a scattered field is achieved with a much larger current than with the localization of the magnetic field by reflection using a ferromagnetic insert. This in turn significantly reduces heat load and energy consumption. The choice of cobalt and cobalt-containing materials as a ferromagnetic material, which can be used as a ferromagnetic insert in the groove during wiring formation, is due to the fact that both cobalt and cobalt-containing materials, when used as a ferro-magnetic insert, most effectively direct the magnetic field per cell.

Standard methods for the formation of copper wiring with a cobalt-containing inlay in the structure of devices operating on the basis of a magnetic tunnel junction, when using a galvanic copper deposition process to form a conductive material that creates a magnetic field (described, for example, in US application number US20040175845, priority 03.03, have long been known .2003 (https://patents.google.com/patent/US20040175845)). Common to the known invention for the formation of the wiring are the following signs - the formation of a groove in which the first barrier layer containing Ta within the groove is sequentially created first, then a copper layer is created on top of it, on which a copper layer is formed on which by electrochemical deposition put a layer of soft magnetic material with the subsequent formation of the second barrier layer and complete the formation of a metal layer on top of the second barrier layer followed by removal of the first barrier layer, the first seed layer, the layer of magnetic material and the metal layer outside the groove. Since both cobalt and cobalt-containing materials have both magnetic and barrier properties (diffusion barrier properties for copper), this reduces the number of wiring layers. Thus, in the prior art and in the claimed invention, when forming copper wiring with a cobalt (cobalt-containing) inset, only signs characterizing part of the layers (their combination) will be common, in particular, the process of forming wiring with a cobalt inset is carried out in the following sequence. First, etching of the groove in the silicon oxide layer on the semiconductor is performed (FIG. 1), followed by deposition of the cobalt insert. Then, a seed layer of copper is deposited, which becomes the basis for the galvanic deposition of copper (Fig. 2). For the formation of layers of wiring using such methods of deposition as electrochemical, electrolysis deposition, chemical, physical deposition from the vapor phase, the deposition of atomic layers. Due to the peculiarities of the galvanic deposition of copper, defects are formed, distributed over the volume of the deposited cobalt layer, which can affect the configuration of the magnetic field lines. When galvanic copper is deposited, due to the acid composition of the chemical solutions used, cobalt dissolves, voids form between the copper layer and the oxide, and the number of defects increases.

The number of defects can vary with changing process conditions, but none of the known approaches using the method of electroplating copper and forming a thick cobalt insert to localize the direction of the magnetic field in a certain direction does not work and does not significantly reduce the number of defects.

SUMMARY OF INVENTION

The objective of the stated solution is to reduce the number of or eliminate the formation of defects resulting from corrosion (dissolution) of cobalt (cobalt-containing material) (300) in the process of galvanic copper deposition (500) when performing chemical-mechanical polishing (CMP) of copper and cobalt (cobalt-containing material) on the surface of the groove (Fig. 3) when creating the structure of the device operating on the basis of a magnetic tunnel junction of the MRAM type, magnetic sensor, etc.

The technical result of the invention, the method of forming copper wiring with a thick cobalt-containing inlay in the structure of devices operating on the basis of a magnetic tunnel junction, is the elimination of the above-described defects in the cobalt layer (cobalt-containing material), which appear as a result of galvanic copper deposition and / or after a chemical-mechanical process polishing the structure of the copper groove with a cobalt (cobalt-containing) tab. It is established that this technical result can be achieved in three variants of the method.

To achieve a technical result, it is important to remove cobalt (cobalt-containing material) (300) from the surface of silicon oxide (100) so that at the same time cobalt (cobalt-containing material) and copper remain only in the groove. This can be done using methods of chemical-mechanical polishing (CMP) or etching before the beginning of the process of electroplating copper deposition in certain combinations. Cobalt-containing tab can contain material from the group Co, CoFe, Co _x Fe _at B _z (x + y + z = 1), Co _x Fe _at B _z Ta _k Z _l (x + y + z + k + l = 1) , Co _x Zr _y Ta _z (x + y + z = 1), Co _x Fe _y SiO _z (x + y + z = 1). Further, to simplify the presentation of the essence and implementation of embodiments of the invention, simply cobalt will be referred to as cobalt-containing materials or cobalt-containing tab, since similar results are achieved using the above-mentioned materials.

The claimed process of forming copper wiring with a thick cobalt-containing inset in the structure of devices operating on the basis of a magnetic tunnel junction is characterized by the fact that it may include technological steps in the following sequence (Fig. 4):

- etching grooves in silicon dioxide (100) on a semiconductor (silicon);

- deposition of cobalt tabs (300);

- deposition of the seed layer of copper (400), for example, by the method of magnetron sputtering for the subsequent deposition of copper by the method of galvanic deposition.

In the first embodiment of the invention, the CMP seed layer of copper and cobalt process is divided into 2 stages.

At the first stage, after deposition of a seed layer of copper (400) using CMP, cobalt (300) is completely removed from the upper surface of SiO ₂ (100) (Fig. 5). After that, galvanic deposition of copper (500) is carried out (Fig. 6).

In the second stage, CMP is performed by removing copper from the upper surface of the groove and the upper surface of SiO ₂ (Fig. 7).

As a result, a groove with copper (copper wiring) and a cobalt insert without defects is formed.

According to the second variant of the invention, a cobalt insert (300) is formed between two Ta (TaN) or Ti (TiN) barrier layers (200) under a seed layer of copper (400), and then copper is deposited using a galvanic deposition method (500) (Fig. 8). ). For this option, only one CMP process is performed.

As a result, a groove with copper (copper wiring) and a cobalt insert without defects is formed.

According to the third variant of the invention, at the beginning they create a standard structure with a groove filled with a cobalt insert (300), then a thick seed layer of copper (400) is deposited, without further using the process of electrochemical deposition of copper. This means that, in order to potentially protect the cobalt from corrosion in the upper part of the groove wall, the seed layer thickness is additionally increased, and if the groove size allows, the seed layer thickness can be increased to a thickness of more than 2000 nm, which actually avoids the process of galvanic copper deposition. (Fig. 9), to use only one CMP process to achieve the result, during which copper and cobalt are removed from the silicon oxide surface, a groove with copper (copper wiring) is formed and a cobalt tab without defects.

LIST OF DRAWINGS

FIG. 1. Schematic representation of the cross-sectional structure of the MRAM during the formation of a cobalt-containing tab in the standard way.

FIG. 2. A schematic cross-section of the MRAM structure shown in FIG. 1, but already with precipitated copper (500) by the method of galvanic deposition.

FIG. 3. A schematic cross-section of the structure shown in FIG. 2 with a cobalt-containing insert and removed due to chemical-mechanical polishing of copper and cobalt from the upper surface of the groove and SiO _2.

FIG. Fig. 4. Schematic representation of the cross section of an MRAM structure with a groove filled with a cobalt-containing inset and a seed layer of copper at the beginning of the process in the first embodiment of the invention.

FIG. 5. The first stage of polishing the structure shown in figure 4, the removal of cobalt and the seed layer to silica in the first embodiment of the invention.

FIG. 6. Electroplating of copper after the first stage of polishing the structure shown in FIG. 5 in the first embodiment of the invention.

FIG. 7. Schematic representation of the cross-sectional structure of the MRAM with a groove filled with copper, after the second stage of the CMP according to the first embodiment of the invention.

FIG. 8. Schematic representation of a cross section of an MRAM structure with a groove filled with a cobalt-containing inset, sandwiched between two Ta (TaN) or Ti (TiN) barrier layers under the seed copper layer, and after galvanic copper deposition of the second embodiment of the invention.

FIG. 9. Schematic representation of a cross section of an MRAM structure with a groove filled with a cobalt-containing insert and a thick seed layer of copper, without an electrochemical copper deposition process according to the third embodiment of the invention.

EXAMPLES OF IMPLEMENTATION OF THE INVENTION

The claimed method of forming copper wiring with a thick cobalt-containing inlay in the structure of devices operating on the basis of a magnetic tunnel junction is characterized by the fact that it includes standard technological stages (various known standard technological methods of forming layers and CMP can be used) in the following sequence (Fig. 4 ):

- etching the groove, for example, by plasma – chemical etching, resulting in a 300–500 nm (100) depth groove in the SiO ₂ volume _{of the} silicon substrate;

- deposition of cobalt-containing inlays (300), for example, by magnetron sputtering until a layer thickness of 5-100 nm is reached (the thickness of the cobalt-containing material on the walls of the groove can reach 5-100 nm);

- the deposition of the seed layer of copper (400), for example, by the method of magnetron sputtering (the layer is the seed for the subsequent deposition of copper by the method of galvanic deposition).

When implementing the first embodiment of the invention, the CMP of the seed layer of copper and cobalt-containing material is further carried out, and the process is divided into 2 stages.

At the first stage, after the deposition of a seed layer of copper using CMP, the cobalt-containing material (300) and the seed copper layer (400) are completely removed from the upper surface of the groove (Fig. 5). In this case, the layer of cobalt-containing material is removed from the upper surface of SiO2 and the groove (100) and remains only on the side walls of the groove. Then carry out the galvanic deposition of copper (500) (Fig. 6). The cobalt-containing tab according to the first embodiment of the invention may contain any material from the group Co, CoFe, Co _x Fe _y B _z (x + y + z = 1), Co _x Fe _y B _z Ta _k Z _l (x + y + z + k + l = 1), Co _x Zr _y Ta _z (x + y + z = 1), Co _x Fe _y SiO _z (x + y + z = 1) with the achievement of a similar result.

At the second stage of the CMP, copper is removed. (Fig. 7).

As a result, a groove is formed with copper and a cobalt insert without defects according to the first embodiment of the invention.

для последующего гальванического осаждения меди (500). Далее осаждается медь, методом гальванического осаждения.When implementing the second embodiment of the invention, a cobalt-containing inlay is formed between Ta / TaN and / or Ti / TiN (200) barrier layers (in any order) that are created on a magnetron sputtering unit, while the Ta / TaN or Ti / TiN barrier layer is deposited thickness from 5 to 25 nm, and cobalt-containing material thickness from 5 nm to 100 nm (300). After that, the same method precipitates a seed layer of copper (400) with a thickness from 400 to 700

for subsequent galvanic deposition of copper (500). Further copper is precipitated by electroplating.

Using the CMP process, copper removal is performed. As a result of carrying out the invention, according to the second embodiment, a groove is formed, filled with copper and a tab of cobalt-containing material, free of defects in silicon oxide (Fig. 8). Moreover, the use of the structure of the layers according to the second variant provides additional results - better adhesion and interdiffusion of materials, which in turn increases the reliability of power supply of the structure being created. The cobalt-containing tab according to the second embodiment of the invention may contain any material from the group Co, CoFe, Co _x Fe _y B _z (x + y + z = 1), Co _x Fe _y B _z Ta _k Z _l (x + y + z + k + l = 1), Co _x Zr _y Ta _z (x + y + z = 1), Co _x Fe _y SiO _z (x + y + z = 1) with the achievement of a similar result.

When implementing the third embodiment of the invention, the CMP seed layer of copper and cobalt-containing material, the CMP process is carried out in one step. At the beginning of the CMP, a standard structure is created with a groove of 300-500 nm in depth in the SiO ₂ volume _{of the} silicon substrate, filled with cobalt-containing inlays by magnetron sputtering until reaching a thickness of 5 - 100 nm, and a thick seed layer of magnetron sputtering is deposited. In the upper part of the groove wall, it is additionally possible to increase the thickness of the seed layer, while if the size of the groove allows, the thickness of the seed layer can be increased to a thickness of about 1000 nm and more than 2000 nm, which actually avoids the process of galvanic copper deposition (Fig. 9). After that, the resulting thick seed layer of copper (400) and the cobalt-containing layer (300) are removed during the CMP process in one step from the SiO ₂ surface, while the copper and cobalt-containing insert remain only inside the groove. Due to the fact that galvanic deposition of copper was not required to fill the groove, the stage of galvanic copper deposition, which is the main cause of corrosion of the cobalt-containing material (increase in the number of defects), is excluded. As a result, the claimed result is achieved when carrying out the invention in the third embodiment. The cobalt-containing tab according to the third embodiment of the invention may contain any material from the group Co, CoFe, Co _x Fe _y B _z (x + y + z = 1), Co _x Fe _y B _z Ta _k Z _l (x + y + z + k + l = 1), Co _x Zr _y Ta _z (x + y + z = 1), Co _x Fe _y SiO _z (x + y + z = 1) with the achievement of a similar result.

Claims (43)

1. The method of forming copper wiring with a thick cobalt-containing tab in the structure of devices operating on the basis of a magnetic tunnel junction, including etching grooves in the volume of SiO ₂ silicon substrate, the deposition of a layer of cobalt containing material to create tabs, the deposition of the seed layer of copper, copper deposition, characterized in that The groove is etched by the method of plasma-chemical etching with a depth of 300-500 nm, the deposition of a layer of cobalt-containing tabs carried out by the method of magnetron sputtering to achieve a thickness of 5-100 nm, the deposition of the seed layer of copper carried out by the method of magnetron sputtering, after the deposition of the copper seed layer, CMP is used, the cobalt-containing layer and the seed copper layer are completely removed from the upper surface of SiO ₂ , then carry out galvanic deposition of copper, then re-use the CMP and copper is removed from the upper surface of SiO _2, while copper and cobalt-containing material remain only inside the groove. 2. The method of forming the copper wiring structure of the device under item 1, characterized in that the cobalt-containing tab contains material from the group Co, CoFe, Co _x Fe _y B _z (x + y + z = 1), Co _x Fe _y B _{Z z k} Z _l (x + y + z + k + l = 1), Co _x Zr _y Ta _z (x + y + z = 1), Co _x Fe _y SiO _z (x + y + z = 1). 3. The method of forming copper wiring with a thick cobalt-containing tab in the structure of devices operating on the basis of a magnetic tunnel junction, including etching grooves in the volume of SiO ₂ silicon substrate, deposition of the first barrier layer the deposition of a layer of cobalt containing material to create tabs, the deposition of the second barrier layer the deposition of the seed layer of copper, copper deposition characterized in that The groove is etched by the method of plasma-chemical etching with a depth of 300-500 nm, barrier layers create a thickness of 5-25 nm using the installation for magnetron sputtering, the deposition of a layer of cobalt-containing tabs carried out by the method of magnetron sputtering to achieve a thickness of 5-100 nm, the deposition of the seed layer of copper with a thickness of 400 to 700

carried out by the method of magnetron sputtering, the deposition of a layer of copper is carried out by the method of galvanic deposition with a thickness of 1000-2000 nm, then re-use the CMP and remove the first barrier layer, the layer of cobalt-containing material, the second barrier layer and copper from the surface of SiO ₂ , while the copper and cobalt-containing material remain only inside the groove. 4. The method of forming the layout of the structure of the device according to p. 3, characterized in that the barrier layers create the type Ta / TaN. 5. The method of forming the layout of the structure of the device according to p. 3, characterized in that the barrier layers create a type of Ti / TiN. 6. The method of forming the layout of the structure of the device according to p. 3, characterized in that the barrier layers create the type Ta / TaN and / or Ti / TiN. 7. A method of forming a wiring structure according to Claim device. 5, characterized in that the cobalt tab comprises a material from the group of _{Co, CoFe, Co x Fe y} B z (x + y + z = _{1), Co x Fe y B z} Ta k Z _l (x + y + z + k + l = 1), Co _x Zr _y Ta _z (x + y + z = 1), Co _x Fe _y SiO _z (x + y + z = 1). 8. The method of forming copper wiring with a thick cobalt-containing tab in the structure of devices operating on the basis of a magnetic tunnel junction, including etching grooves in the volume of SiO ₂ silicon substrate, the deposition of a layer of cobalt containing inlays, the deposition of the seed layer of copper, characterized in that The groove is etched by the method of plasma-chemical etching with a depth of 300-500 nm, the deposition of a layer of cobalt-containing tabs carried out by the method of magnetron sputtering to achieve a thickness of 5-100 nm, the deposition of the seed layer of copper is carried out by the method of magnetron sputtering to a thickness of 1000-2000 nm, then the CMP is used again and the copper and the layer of cobalt-containing material are removed from the SiO ₂ surface, while the copper and cobalt-containing tab remain only inside the groove. 9. The method of forming the layout of the structure of the device according to claim 8, characterized in that the cobalt-containing inlay contains material from the group Co, CoFe, Co _x Fe _y B _z (x + y + z = 1), Co _x Fe _y B _z Ta _k Z _l (x + y + z + k + l = 1), Co _x Zr _y Ta _z (x + y + z = 1), Co _x Fe _y SiO _z (x + y + z = 1).

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