Method for forming top contact of magnetic tunnel junction

Abstract

Embodiments of the present disclosure relate to methods for manufacturing structures used in memory devices. More specifically, embodiments of the present disclosure relate to methods for manufacturing MTJ structures in memory devices. In one embodiment, the method includes the following steps: forming an MTJ structure; depositing an encapsulation layer on the top and sides of the MTJ structure; depositing a dielectric material on the encapsulation layer; removing the dielectric material and the encapsulation layer disposed on the top of the MTJ structure by a chemical mechanical planarization (CMP) process to expose the top of the MTJ structure; and depositing a contact layer on the MTJ structure. The method utilizes a CMP process without an etching process to expose the top of the MTJ structure, which avoids damaging the MTJ structure and results in improved electrical contact between the MTJ structure and the contact layer.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to methods for fabricating structures used in memory devices. More specifically, embodiments of the present disclosure relate to methods for fabricating magnetic tunnel junction structures in memory devices. Background Art

[0002] Magnetoresistive random access memory (MRAM) is a memory device containing an array of MRAM cells that use their resistance values ​​rather than charge to store data. Typically, each MRAM cell includes a magnetic tunnel junction (MTJ) structure. The MTJ structure can have an adjustable resistance to represent a logic state of "0" or "1". The MTJ structure typically includes two ferromagnetic layers separated by a thin non-magnetic layer (e.g., a tunnel barrier layer). The top contact layer and the bottom contact layer are used to sandwich the MTJ structure so that current can flow through the MTJ structure.

[0003] The layers of the MTJ structure are typically deposited sequentially as an overlying blanket film. The layers are then patterned by various etching processes to form the MTJ structure, in which one or more layers are partially or completely removed. However, the etching process may damage the MTJ structure and may result in poor electrical contact with the top electrode.

[0004] Therefore, there is a need for improved methods for forming MTJ structures. Summary of the invention

[0005] Embodiments of the present disclosure relate to a method for manufacturing a structure used in a memory device. More specifically, embodiments of the present disclosure relate to a method for manufacturing an MTJ structure in a memory device. In one embodiment, the method includes the following steps: forming a magnetic tunnel junction structure on a first contact layer; depositing an encapsulation layer on the top and side of the magnetic tunnel junction structure; removing the encapsulation layer disposed on the top of the magnetic tunnel junction by a chemical mechanical planarization process to expose the top of the magnetic tunnel junction structure; and depositing a second contact layer on the magnetic tunnel junction structure.

[0006] In another embodiment, a method includes the following steps: forming a magnetic tunnel junction structure on a first contact layer; depositing an encapsulation layer on the top and side of the magnetic tunnel junction structure; depositing a dielectric material on the encapsulation layer; removing the dielectric material and the encapsulation layer disposed on the top of the magnetic tunnel junction by a chemical mechanical planarization process to expose the top of the magnetic tunnel junction structure; and depositing a second contact layer on the magnetic tunnel junction structure.

[0007] In another embodiment, a method includes the following steps: forming a magnetic tunnel junction structure on a first contact layer; depositing an encapsulation layer on the top and sides of the magnetic tunnel junction structure, the encapsulation layer comprising silicon carbon nitride; depositing a dielectric material on the encapsulation layer; removing a portion of the dielectric material and a portion of the encapsulation layer to form a through hole and a trench on the top of the through hole, with the top of the magnetic tunnel junction structure exposed; and depositing a second contact layer in the trench and the through hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order that the manner in which the above-mentioned features of the present disclosure can be understood in detail, a more detailed description of the present disclosure briefly summarized above can be obtained by reference to the embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings only show exemplary embodiments and therefore should not be considered as limiting the scope thereof, and other equivalent embodiments may be allowed.

[0009] Figure 1 is a flow chart of a method for forming a structure.

[0010] Figure 2A-2E Shown in Figure 1 Schematic cross-sectional views of the structure during different stages of the method.

[0011] Figure 3 is a flow chart of a method for forming a structure.

[0012] Figure 4A-4E Shown in Figure 3 Schematic cross-sectional views of the structure during different stages of the method.

[0013] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure relate to methods for manufacturing structures used in memory devices. More specifically, embodiments of the present disclosure relate to methods for manufacturing MTJ structures in memory devices. In one embodiment, the method includes the following steps: forming an MTJ structure; depositing an encapsulation layer on the top and sides of the MTJ structure; depositing a dielectric material on the encapsulation layer; removing the dielectric material and the encapsulation layer disposed on the top of the MTJ structure by a chemical mechanical planarization (CMP) process to expose the top of the MTJ structure; and depositing a contact layer on the MTJ structure. The method utilizes a CMP process rather than an etching process to expose the top of the MTJ structure, which avoids damaging the MTJ structure and results in improved electrical contact between the MTJ structure and the contact layer.

[0015] Figure 1 is a flow chart of a method 100 for forming a structure 200 . Figure 2A-2E Shown in Figure 1 Schematic cross-sectional views of structure 200 during different stages of method 100. Method 100 comprises forming Figure 2A The MTJ structure 204 shown in FIG. 1 begins with operation 102. The MTJ structure 204 is formed on a contact layer 202. The contact layer 202 is made of a conductive material such as a metal. For example, the contact layer 202 is made of copper, cobalt, tungsten, tantalum, tantalum nitride, titanium, titanium nitride, tungsten nitride, or other suitable materials. The MTJ structure 204 includes a first magnetic layer 206, a non-magnetic layer 208 disposed above the first magnetic layer 206, a second magnetic layer 210 disposed above the non-magnetic layer 208, and a cap layer 212 disposed above the second magnetic layer 210. The first magnetic layer 206 and the second magnetic layer 210 are made of a ferromagnetic material such as a metal alloy with a dopant such as a boron dopant, an oxygen dopant, or other suitable materials. The metal alloy may be a nickel-containing material, a platinum-containing material, a ruthenium-containing material, a cobalt-containing material, a tantalum-containing material, and a palladium-containing material. Suitable examples of ferromagnetic materials include Ru, Ta, Co, Pt, TaN, NiFeOx, NiFeB, CoFeOxB, CoFeB, CoFe, NiOxB, CoBOx, FeBOx, CoFeNiB, CoPt, CoPd, TaOx, and the like. The nonmagnetic layer 208 may be made of a dielectric material for a tunnel junction magnetoresistive (TMR) sensor or a conductive material for a giant magnetoresistive (GMR) sensor. If the MTJ structure 204 is a TMR sensor, the nonmagnetic layer 208 is made of MgO, HfO2, TiO2, Ta2O5, Al2O3, or other suitable materials. If the MTJ structure 204 is a GMR sensor, the nonmagnetic layer 208 is made of copper, silver, molybdenum, tantalum, tungsten, or other suitable materials. The cap layer 212 may be made of ruthenium, iridium, tantalum, tungsten, titanium, tantalum nitride, tungsten nitride, titanium nitride, magnesium oxide, or other suitable materials.

[0016] The layers 206, 208, 210, 212 of the MTJ structure 204 may be sequentially blanket deposited on the contact layer 202 and then patterned by one or more etching processes. The deposition process may be any suitable process, such as a chemical vapor deposition (CVD) process, a plasma enhanced chemical vapor deposition process (PECVD) process, and / or a physical vapor deposition (PVD) process. The etching process may be any suitable etching process, such as a reactive ion etching (RIE) process.

[0017] Next, at operation 104, an encapsulation layer 214 is deposited on the top 213 and the side 215 of the MTJ structure 204, as shown in FIG. Figure 2B As shown. Encapsulation layer 214 is made of a dielectric material. Encapsulation layer 214 may be made of a nitrogen-containing material, a carbon-containing material, or an oxide-containing material. Suitable exemplary materials for forming encapsulation layer 214 include silicon nitride (SiN), silicon nitride carbon (SiCN), silicon dioxide (SiO2), silicon oxynitride (SiON), silicon carbide (SiC), amorphous carbon, silicon oxycarbide (SiOC), aluminum oxide (Al2O3), aluminum nitride (AlN), and the like. Encapsulation layer 214 may be formed by atomic layer deposition (ALD) processing, and encapsulation layer 214 may be a conformal layer.

[0018] Next, at operation 106, a dielectric material 216 is deposited on the encapsulation layer 214, such as Figure 2C As shown. The dielectric material 216 may be an inter-layer dielectric (ILD) and may be made of an oxide such as silicon oxide. At operation 108, a portion of the dielectric material 216 disposed above the top 213 of the MTJ structure 204 and a portion of the encapsulation layer 214 disposed on the top 213 of the MTJ structure 204 are removed by a CMP process to expose the top 213 of the MTJ structure 204, as shown. Figure 2D As shown. The side 215 of the MTJ structure 204 remains covered by the encapsulation layer 214. Unlike conventional etching processes used to expose the MTJ structure 204, the CMP process avoids damaging the MTJ structure 204 and results in improved electrical contact between the MTJ structure 204 and the contact layer 218 (see Figure 2E ).

[0019] Next, at operation 110, a contact layer 218 is deposited on the top 213 of the MTJ structure 204, such as Figure 2E The contact layer 218 may be made of the same material as the contact layer 202. The contact layer 218 may be disposed on the encapsulation layer 214 and the dielectric material 216. The contact layer 218 may first be blanket deposited and then patterned by an etching process.

[0020] Figure 3 is a flow chart of a method 300 for forming a structure 400 . Figure 4A-4E Shown in Figure 3 Schematic cross-sectional view of structure 400 during different stages of method 300. Method 300 comprises forming Figure 4A The MTJ structure 404 is formed on a contact layer 402. The contact layer 402 is made of a conductive material such as a metal. The contact layer 402 may be made of a conductive material such as a metal. Figure 2AThe MTJ structure 404 includes a first magnetic layer 406, a non-magnetic layer 408 disposed above the first magnetic layer 406, a second magnetic layer 410 disposed above the non-magnetic layer 408, and a cap layer 412 disposed above the second magnetic layer 410. The first magnetic layer 406 and the second magnetic layer 410 are made of a ferromagnetic material such as a metal alloy with a dopant such as a boron dopant, an oxygen dopant, or other suitable materials. The metal alloy may be a nickel-containing material, a platinum-containing material, a ruthenium-containing material, a cobalt-containing material, a tantalum-containing material, and a palladium-containing material. Suitable examples of ferromagnetic materials include Ru, Ta, Co, Pt, TaN, NiFeOx, NiFeB, CoFeOxB, CoFeB, CoFe, NiOxB, CoBOx, FeBOx, CoFeNiB, CoPt, CoPd, TaOx, and the like. The non-magnetic layer 408 may be made of a dielectric material for a TMR sensor or of a conductive material for a GMR sensor. If the MTJ structure 404 is a TMR sensor, the non-magnetic layer 408 is made of MgO, HfO2, TiO2, Ta2O5, Al2O3, or other suitable materials. If the MTJ structure 404 is a GMR sensor, the non-magnetic layer 408 is made of copper, silver, molybdenum, tantalum, tungsten, or other suitable materials. The cap layer 412 can be made of ruthenium, iridium, tantalum, tungsten, titanium, tantalum nitride, tungsten nitride, titanium nitride, magnesium oxide, or other suitable materials.

[0021] The layers 406, 408, 410, 412 of the MTJ structure 404 may be sequentially blanket deposited on the contact layer 402 and then patterned by one or more etching processes. The deposition process may be any suitable process, such as a CVD process, a PECVD process, and / or a PVD process. The etching process may be any suitable etching process, such as a RIE process.

[0022] Next, at operation 304, an encapsulation layer 414 is deposited on the top 413 and the side 415 of the MTJ structure 404, such as Figure 4B As shown. The encapsulation layer 414 is made of a dielectric material having good etching selectivity to the dielectric material 416 ( Figure 4C In one embodiment, the encapsulation layer 414 is made of SiCN. The encapsulation layer 414 may be formed by an atomic layer deposition (ALD) process and may be a conformal layer.

[0023] Next, at operation 306, a dielectric material 416 is deposited on the encapsulation layer 414, such as Figure 4C. The dielectric material 416 may be an ILD and may be made of an oxide, such as silicon oxide. The dielectric material 416 may be planarized by a CMP process. At operation 308, a portion of the dielectric material 416 disposed above the top 413 of the MTJ structure 404 and around the side 415 of the MTJ structure 404 is removed by one or more etching processes, such as Figure 4D As shown. The one or more etching processes also remove a portion of the encapsulation layer 414 disposed on the top 413 of the MTJ structure 404, and the top 413 of the MTJ structure 404 is exposed. In one embodiment, a single etching process is performed to remove a portion of the dielectric material 416 and a portion of the encapsulation layer 414, and to form an opening 418. In another embodiment, a dual damascene process is performed, which includes a first etching process to form a through hole 420 and a second etching process to form a trench 422 above the through hole 420, as shown. Figure 4D The side 415 of the MTJ structure 404 is still covered by the encapsulation layer 414. Because the encapsulation layer 414 is made of a dielectric material having good etching selectivity to the dielectric material 416 (i.e., having an etching rate much slower than that of the dielectric material 416), the MTJ structure 404 is not damaged during the etching of the dielectric material 416.

[0024] Next, at operation 310, a contact layer 424 is deposited in the opening 418 (or via 420 and trench 422) and on the top 413 of the MTJ structure 404, as shown in FIG. Figure 4E As shown. The contact layer 424 may be made of the same material as the contact layer 402. The contact layer 424 may be formed by an electrochemical plating (ECP) process. The contact layer 424 may be planarized by a CMP process to be coplanar with the dielectric material 416.

[0025] By using a CMP process to expose the MTJ structure, the MTJ structure is not damaged. Alternatively, by using a material having good etching selectivity to the interlayer dielectric as the encapsulation layer, the interlayer dielectric is removed by an etching process to expose the MTJ structure without damaging the MTJ structure.

[0026] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope of the disclosure, the scope of which is to be determined by the claims that follow.

Claims

1. A method comprising the following steps: forming a magnetic tunnel junction structure on the first contact layer; depositing an encapsulation layer on top and sides of the magnetic tunnel junction structure; depositing a dielectric material on the encapsulation layer; performing a dual damascene process to remove a portion of the dielectric material disposed on the top of the magnetic tunnel junction structure and surrounding the side of the magnetic tunnel junction structure and remove a portion of the encapsulation layer disposed on the top of the magnetic tunnel junction structure to expose the top of the magnetic tunnel junction structure, wherein the dual damascene process forms a via and a trench on the top of the via, and wherein the encapsulation layer has a lower etch rate than the dielectric material, wherein the dual damascene process comprises sequentially performing the following steps: performing a first etching process to form the through hole, and performing a second etching process to form the trench; and A second contact layer is deposited on the magnetic tunnel junction structure. 2 . The method according to claim 1 , wherein the magnetic tunnel junction structure comprises a first magnetic layer, a second magnetic layer, and a nonmagnetic layer disposed between the first magnetic layer and the second magnetic layer.

3. The method of claim 2, wherein the nonmagnetic layer comprises MgO, HfO2, TiO2, Ta2O5 or Al2O3.

4. The method of claim 2, wherein the nonmagnetic layer comprises copper, silver, molybdenum, tantalum, or tungsten. The method of claim 2 , wherein the magnetic tunnel junction structure further comprises a capping layer disposed on the second magnetic layer.

6. The method of claim 5, wherein the capping layer comprises ruthenium, iridium, tantalum, tungsten, titanium, tantalum nitride, tungsten nitride, titanium nitride, or magnesium oxide.

7. The method of claim 1, wherein the encapsulation layer comprises silicon nitride, silicon carbon nitride, silicon dioxide, silicon oxynitride, silicon carbide, amorphous carbon, silicon oxycarbide, aluminum oxide, or aluminum nitride (AlN). The method of claim 1 , wherein the dielectric material comprises an oxide.

9. The method of claim 1, wherein the second contact layer comprises copper, cobalt, tungsten, tantalum, tantalum nitride, titanium, titanium nitride, or tungsten nitride.

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