JP2012156172A - Magnetic resistance element and manufacturing method thereof and semiconductor storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further increase the thermal stability index Δ of a magnetic resistance element by means of stress control concerning a magnetic resistance element and its manufacturing method and a semiconductor storage device.SOLUTION: A magnetoresistance effect element includes an antiferromagnetic layer, a pinned layer, a tunnel insulation film, a free layer, a cap layer, an etching stopper film, a hard mask and an upper electrode which are all formed on a lower electrode in that order from the lower electrode side and an insulation film formed on at least a side face of the free layer, characterized in that a product of stress of the etching stopper film and magnetostriction constant of the free layer is made to be negative.

Description

  The present invention relates to a magnetoresistive element, a method for manufacturing the same, and a semiconductor memory device. For example, the present invention relates to a means for increasing a thermal stability index Δ.

  2. Description of the Related Art Conventionally, a ferromagnetic tunnel junction (MTJ) element is used as a magnetic sensor unit constituting a reproducing magnetic head or as an information storage unit of a magnetic random access memory device (MRAM; Magnetic Random Access Memory). Yes.

  A ferromagnetic tunnel junction element has a structure in which a pinning layer composed of an antiferromagnetic layer, a pinned layer composed of a ferromagnetic layer, a tunnel insulating film such as MgO, and a free layer composed of a ferromagnetic layer are sequentially laminated. It is comprised so that an electric current may flow in a direction.

  In this ferromagnetic tunnel junction device, when the magnetization direction of the free layer is parallel to the magnetization direction of the pinned layer, the tunnel current easily flows, so that the resistance state is low, and when both are antiparallel, the tunnel current does not easily flow. It becomes a state. The magnetic information written on the magnetic recording medium is read or the information “0” or “1” is stored due to the difference in resistance state.

  In recent years, a so-called spin-injection MRAM that supplies a write current directly to an MTJ element and records information in the MTJ element according to the direction of the write current has attracted attention (for example, see Patent Document 1). With the recent demand for a large storage capacity, the memory size of a spin-injection MRAM device is also being reduced, and the write current is being reduced along with the reduction.

JP 2009-212156 A

  However, although the write current is reduced with the reduction in size, there is a problem of a decrease in thermal stability in which magnetization reversal is likely to occur due to heat. In order to maintain the characteristics as a magnetoresistive element, it is necessary to ensure the thermal stability index Δ at a certain level or more so that magnetization reversal due to heat does not occur.

Incidentally, the thermal stability index delta, saturation magnetization of the free layer M _s, the volume of the free layer V, anisotropy field of the H _k free layer, absolute temperature T, when the k _b is Boltzmann constant,
_{Δ = (M s · V ·} H k) / (2k b T) ··· (1)
It is represented by Therefore, since the thermal stability index Δ decreases with a decrease in the volume V of the free layer accompanying the reduction of the element, the element characteristics become unstable.

  Further, as apparent from the equation (1), since the thermal stability index Δ is inversely proportional to the temperature T, the thermal stability index Δ decreases due to the temperature rise of the element, and the element characteristics become unstable. There is also.

  Accordingly, an object of the present invention is to increase the thermal stability index Δ of the spin-injection magnetoresistive element by stress control.

  From one aspect to be disclosed, an antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, a cap layer, an etching stopper film, a hard mask, and an upper electrode provided in this order on the lower electrode from the lower electrode side, and at least the above A magnetoresistive element having an insulating film provided on a side surface of a free layer and having a negative product of the stress of the etching stopper film and the magnetostriction constant of the free layer is provided.

  Further, from another viewpoint to be disclosed, an antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, a cap layer, an etching stopper film, a hard mask, and an upper electrode provided in order from the lower electrode side on the lower electrode; A magnetoresistive element having an insulating film provided at least on a side surface of the free layer, wherein the product of the stress of the insulating film and the magnetostriction constant of the free layer is positive and the absolute value is 1 GPa or more. An element is provided.

  From another viewpoint disclosed, an antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, and a cap layer are sequentially formed on the lower electrode, and the free layer is formed on the cap layer. A step of forming an etching stopper film under a condition having a stress that makes the product of the magnetostriction constant negative, a step of forming a hard mask on the etching stopper film, the lower electrode, the antiferromagnetic layer, the pinned layer, A magnetoresistive element comprising: a step of depositing an insulating film so as to cover a tunnel insulating film, a free layer, a cap layer, an etching stopper film, and a hard mask; and a step of forming an upper electrode on the hard mask A manufacturing method is provided.

  From another viewpoint to be disclosed, a semiconductor memory device using the above-described magnetoresistive element as an information storage portion of a memory cell is provided.

  According to the disclosed magnetoresistive element, manufacturing method thereof, and semiconductor memory device, the thermal stability index Δ of the magnetoresistive element can be increased by stress control.

It is explanatory drawing of the relationship between the magnetization easy axis | shaft in a free layer, a magnetization difficult axis | shaft, and the direction of a spin. It is explanatory drawing of the relationship between the magnetostriction constant (lambda) and the applied stress in the case of making the coercive force Hc large. It is a notional perspective view of the magnetoresistive element of an embodiment of the invention. It is explanatory drawing of the effect of the magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process to the middle of the magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process until the middle of FIG. 5 or subsequent of the magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process to the middle after FIG. 6 of the magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process after FIG. 7 of the magnetoresistive element of embodiment of this invention. It is a conceptual perspective view of the other magnetoresistive element of embodiment of this invention. It is explanatory drawing of the effect of the other magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process to the middle of the other magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process to the middle after FIG. 11 of the other magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process after FIG. 12 of the other magnetoresistive element of embodiment of this invention. It is explanatory drawing of the manufacturing process to the middle of the semiconductor memory device of Example 1 of this invention. It is explanatory drawing of the manufacturing process until the middle of FIG. 14 or subsequent of the semiconductor memory device of Example 1 of this invention. FIG. 16 is an explanatory diagram of the manufacturing process up to the middle of FIG. 15 and subsequent drawings of the semiconductor memory device according to Example 1 of the present invention; FIG. 17 is an explanatory diagram of the manufacturing process up to the middle of FIG. 16 and subsequent drawings of the semiconductor memory device according to Example 1 of the present invention; FIG. 18 is an explanatory diagram of the manufacturing process up to the middle of FIG. 17 and subsequent drawings of the semiconductor memory device according to Example 1 of the present invention; FIG. 19 is an explanatory diagram of the manufacturing process up to the middle of FIG. 18 and subsequent drawings of the semiconductor memory device according to Example 1 of the present invention; FIG. 20 is an explanatory diagram of the manufacturing process of FIG. 19 and subsequent drawings of the semiconductor memory device according to Example 1 of the present invention;

Here, the thermal stability index Δ is examined. As described above, the thermal stability index Δ is expressed as follows: M _s is the saturation magnetization of the free layer, V is the volume of the free layer, H _k is the anisotropic magnetic field of the free layer, T is the absolute temperature, and k _b is the Boltzmann constant. Then
_{Δ = (M s · V ·} H k) / (2k b T) ··· (1)
It is represented by

On the other hand, by applying a magnetic field in the direction opposite to the direction magnetized on the magnetic material, the magnetic field at the time when the magnetization becomes 0 while taking various magnetization processes is used, and the coercive force is a value for estimating the ease of magnetization reversal. there are (coercivity) _{H c.} The coercivity H _c is related below between the anisotropy field H _k.
H _c ∝H _k (2)
Thus, increasing the coercivity H _c can be increased anisotropy field H _k, as a result, it is possible to improve the thermal stability index delta.

The coercive force H _c is the eigenvalue with H _c1 is a magnetic material, the value resulting from the shape of the magnetic and H _c2 body, the magnetostriction constant of the free and λ layer, stress value of σ free layer, and the constants A and B Then
Hc = H _c1 + H _c2 + A · λ · σ / Ms + B (3)
It is represented by

  Therefore, the first term is limited in terms of material and the second term is limited in terms of shape. As a result of intensive studies, in order to increase the value of the coercive force Hc, the value of the third term is increased. It was concluded that this is the most effective.

  FIG. 1 is an explanatory diagram of the relationship between the easy and hard magnetization axes and the spin direction in the free layer. The free layer has an easy magnetization axis and a hard magnetization axis orthogonal to the free layer, and the easy magnetization axis is longer than the hard magnetization axis. That is, the longitudinal direction of the free layer is the easy axis of magnetization.

  FIG. 2 is an explanatory diagram of the relationship between the magnetostriction constant λ and the applied stress when the coercive force Hc is increased. As shown in FIG. 2A, when the magnetostriction constant λ of the free layer is positive, the third term in the above formula (3) is increased by applying a tensile stress in the direction of the easy axis of the free layer. Can do. On the other hand, as shown in FIG. 2B, when the magnetostriction constant λ of the free layer is negative, the third term in the above equation (3) is increased by applying a compressive stress in the direction of the easy axis of the free layer. can do.

  Therefore, in both cases where the magnetostriction constant λ of the free layer is positive or negative, the coercive force Hc can be increased by increasing the absolute value of the stress applied in the direction of the easy axis of the free layer. The thermal stability of the free layer can be improved.

  FIG. 3 is a conceptual perspective view of the magnetoresistive element according to the embodiment of the present invention. As shown in FIG. 3, the element portion of the magnetoresistive element according to the embodiment of the present invention includes a lower electrode 12, an antiferromagnetic layer 13, a pinned layer 14, a tunnel insulating film 15, a free electrode provided on the base insulating layer 11. A layer 16, a cap layer 17, an etching stopper film 18, and a hard mask 19 are formed. The element portion is covered with an insulating film 20 so that the flat portion is higher than the position of the free layer 16, an interlayer insulating film 21 is provided thereon, and an upper electrode 22 is formed thereon.

  In this case, the lower electrode 12 is composed of, for example, a laminated structure of a Ta film and an Al film, PtMn, IrMn, or the like is used as the antiferromagnetic layer 13, and a single layer structure of CoFeB or NiFe is used as the pinned layer 14. Alternatively, a multilayer structure such as CoFeB / Ru / CoFeB is formed. The tunnel insulating film 15 is made of MgO or Al—O.

  The free layer 16 is made of CoFeB, NiFe, or the like, but the magnetostriction constant λ in the case of CoFeB has a negative value. As the cap layer 17, for example, Ta is used. The etching stopper film 18 also serves as a stress adjustment layer that applies a stress that makes the product of the magnetostriction constant λ of the free layer 16 negative to the free layer 16. Therefore, when the magnetostriction constant λ is negative, the stress value is controlled by the film forming conditions using Ru or Cr so as to form a film having a tensile stress. As film forming conditions, the tensile stress can be increased as the gas pressure is increased and the applied power is decreased. The absolute value of stress is desirably 200 MPa or more, and although there is no upper limit, it is practically 600 MPa or less.

  If the stress of the etching stopper film 18 that also serves as the stress adjusting layer is a tensile stress, a force for contracting acts on the contrary, and a compressive stress is applied to the free layer 16 immediately below. Since the cap layer 17 is very thin compared to the stress adjustment layer, the influence of the stress on the free layer 16 is limited.

As the hard mask 19, for example, Ta is used. The insulating film 20 serving as the cover film is formed by depositing SiC, SiN, or SiCN by the CVD method. Again, by changing the film forming conditions, the product of the free layer 16 and the magnetostriction constant λ becomes positive and the stress is increased. Adjust so that the absolute value is 1 GPa or more. Since the magnetostriction constant λ of CoFeB is negative, when CoFeB is used as the free layer, it is set to a compressive stress. Further, it is possible to generate a compressive stress by implanting Ar ions after film formation. For example, it may be implanted at a dose of 1 × 10 ¹⁴ cm ⁻² with an acceleration energy of 100 keV.

As the interlayer insulating film 21, a SiO ₂ , SiOC, or Low-k film is used. Again, when the magnetostriction constant λ of the free layer 16 is negative, the CVD method is used so as to have a compressive stress of −500 MPa or more. Alternatively, the film is formed by a coating method. The upper electrode 22 is formed using, for example, Cu and a damascene method.

  FIG. 4 is an explanatory diagram of the operation and effect of the magnetoresistive element according to the embodiment of the present invention, FIG. 4 (a) is an explanatory diagram of a stress application state, and FIG. 4 (b) is a graph of the thermal stability index Δ. It is explanatory drawing of stress dependence. As shown in FIG. 4B, the thermal stability index Δ increases as the stress of the stress adjustment layer increases, that is, as the tensile stress increases, and when the stress of the insulating film 20 is high compressive stress. It gets bigger. Note that the etching stopper layer 18 serving as a stress adjustment layer is directly above the free layer 16, and therefore has a greater influence than the insulating film 20.

Next, with reference to FIGS. 5 to 8, the manufacturing process of the magnetoresistive element according to the embodiment of the present invention will be described. First, as shown in FIG. 5A, on the base insulating film 11, the lower electrode 12, the antiferromagnetic layer 13, the pinned layer 14, the tunnel insulating film 15, the free layer 16, the cap layer 17, the etching stopper film 18, A hard mask 19 and an insulating film hard mask 23 such as SiO ₂ are sequentially stacked. Here, as described above, the film is formed so that the product of the free layer 16 and the magnetostriction constant λ is negative and the absolute value is 200 MPa or more so that the etching stopper film 18 also serves as a stress adjusting layer.

  Next, as shown in FIG. 5B, the insulating film hard mask 23 is etched using the resist pattern 24 as a mask. Next, as shown in FIG. 5C, the hard mask 19 is etched using the insulating film hard mask 23 as a mask. At this time, the etching is stopped on the etching stopper film 18 so that the magnetoresistive element portion is not oxidized in the ashing process.

  Next, as shown in FIG. 6D, the etching stopper film 18 to the antiferromagnetic layer 13 are etched using the hard mask 19 as a mask to expose the lower electrode 12. Next, as shown in FIG. 6E, an insulating film 20 serving as a cover film is formed so that the film thickness on the lower electrode 12 exceeds the height of the free layer 16. At this time, as described above, the film is formed under the condition that the product of the free layer 16 and the magnetostriction constant λ is positive and the absolute value of the stress is 1 GPa or more.

  Next, as shown in FIG. 6F, a trilevel resist composed of a lower layer resist 25, an SOG (Spin on Glass) film 26, and a resist 27 is provided, and ArF exposure is performed. Note that the SOG film also serves as an antireflection film by adjusting the film thickness. KrF exposure may be used.

  Next, as shown in FIG. 7G, the insulating film 20 is etched using the trilevel structure resist pattern as a mask. Next, as shown in FIG. 7H, the lower electrode 12 is etched.

  Next, as shown in FIG. 7I, an interlayer insulating film 21 having a thickness of 100 nm to 500 nm is deposited and then planarized by CMP to expose the top surface of the hard mask 19. At this time, as described above, the film is formed so that the product of the free layer 16 and the magnetostriction constant λ is positive and has an absolute value of 500 MPa or more.

Next, as shown in FIG. 8J, a second interlayer insulating film 28 having a thickness of 100 nm to 200 nm is deposited on the entire surface. The second interlayer insulating film 28 is formed by a CVD method or a coating method using a SiO ₂ , SiC or Low-k film.

  Next, as shown in FIG. 8K, a recess 29 for forming an upper electrode is formed in the second interlayer insulating film. Next, as shown in FIG. 8L, for example, the recess 29 is filled with a Cu plating film by Cu electrolytic plating, and then the upper electrode 22 is formed by planarization by CMP, thereby completing the basic process flow. To do.

  As described above, in the embodiment of the present invention, the etching stopper film provided immediately above the free layer is formed so as to also serve as the stress adjustment layer. Therefore, the third term of the coercive force of the free layer should be increased. As a result, the thermal stability index Δ can be increased.

  Further, since the insulating film covering the magnetoresistive element portion is also formed so as to have a stress that increases the third term of the coercive force of the free layer, the thermal stability index Δ can be increased. In the above-described embodiment, both the etching stopper film and the insulating film are given a stress that increases the thermal stability index Δ, but either one of them may be given such a stress. good.

  FIG. 9 is a conceptual perspective view of another magnetoresistive element according to the embodiment of the present invention. As shown in FIG. 9, the element portion of another magnetoresistive element according to the embodiment of the present invention includes a lower electrode 12, an antiferromagnetic layer 13, a pinned layer 14, and a tunnel insulating film 15 provided on the base insulating layer 11. , A free layer 16, a cap layer 17, an etching stopper film 18, and a hard mask 19. The element portion is covered with the insulating film 20 so that the flat portion is higher than the position of the free layer 16, and the metal film 30 and the interlayer insulating film 21 are sequentially provided thereon, and the upper electrode 22 is formed thereon. .

The structure of each member in this case is exactly the same as that of the magnetoresistive element according to the embodiment of the present invention shown in FIG. 3, but the metal film 30 has a high linear thermal expansion coefficient and a high Young's modulus and is dry. Use materials that are easy to etch. As such a material, Ru, Al, Cr or Ta is suitable as shown in Table 1.

  FIG. 10 is an explanatory view of the action and effect of another magnetoresistive element according to the embodiment of the present invention, and FIG. 10 (a) is an explanatory view of a stress application state when the element temperature rises, and FIG. ) Is an explanatory diagram of the element temperature dependence of the thermal stability index Δ.

  As shown in FIG. 10A, when the element temperature rises, the metal film 30 having a large linear thermal expansion coefficient expands and compressive stress is applied to the free layer 16. As shown in FIG. 10B, the thermal stability index Δ decreases as the element temperature increases. At this time, when the metal film 30 is provided, a decrease in the thermal stability index Δ is suppressed as compared with the case where the metal film 30 is not provided.

  Next, with reference to FIG. 11 to FIG. 13, another manufacturing process of the magnetoresistive element according to the embodiment of the present invention will be described. First, as shown in FIG. 11A, the process up to the step of forming the insulating film 20 is exactly the same as the process of FIGS. 5A to 6E.

  Next, as shown in FIG. 11B, a metal film 30 is formed on the insulating film 20. At this time, the film is formed under the condition that the product of the free layer 16 and the magnetostriction constant λ is positive and the absolute value of the stress is 1 GPa or more. For example, when the magnetostriction constant λ of the free layer 16 is negative, it can be made to have a compressive stress by forming a film under conditions of low gas pressure or high applied power.

  Next, as shown in FIG. 11C, a trilevel resist composed of the lower layer resist 25, the SOG film 26, and the resist 27 is provided, and ArF exposure is performed. Note that the SOG film also serves as an antireflection film by adjusting the film thickness. KrF exposure may be used.

  Next, as shown in FIG. 12D, the metal film 30 is etched using the resist pattern having a trilevel structure as a mask. Subsequently, the insulating film 20 is etched as shown in FIG. Next, as shown in FIG. 12F, the lower electrode 12 is etched.

  Next, as shown in FIG. 13G, an interlayer insulating film 21 having a thickness of 100 nm to 500 nm is deposited and then planarized by CMP to expose the top surface of the hard mask 19. At this time, as described above, the film is formed so that the product of the free layer 16 and the magnetostriction constant λ is positive and has an absolute value of 500 MPa or more.

  Next, as shown in FIG. 13H, after depositing a second interlayer insulating film 28 having a thickness of 100 nm to 200 nm on the entire surface, a recess 29 for forming an upper electrode is formed in the second interlayer insulating film 28. . Next, as shown in FIG. 13I, for example, the recess 29 is filled with a Cu plating film by Cu electrolytic plating, and then planarized by CMP to form the upper electrode 22 to complete the basic process flow. To do.

  As described above, in another magnetoresistive element according to the embodiment of the present invention, both the etching stopper film and the insulating film have a stress that increases the thermal stability index Δ, and the metal film has a large linear thermal expansion coefficient. Therefore, stability against fluctuations in element temperature is improved.

  Based on the above, next, a manufacturing process of the semiconductor memory device according to the first embodiment of the present invention will be described with reference to FIGS. First, as shown in FIG. 14A, an element isolation insulating film 32 by shallow trench isolation (STI) is formed on the surface of a silicon substrate 31, and the active region surrounded by the element isolation insulating film 32 is formed. Then, the MOSFET 33 is formed.

  The MOSFET 33 includes a gate insulating film 34, a gate electrode 35, a source region 36, and a drain region 37, and side walls 38 are provided on both sides of the gate electrode 35. An extension region is formed near the gate electrode of the source region 36 and the drain region 37.

  Next, after depositing an interlayer insulating film 39 having a thickness of 1.5 μm made of phosphor glass (PSG) on the entire surface, two via holes that penetrate the interlayer insulating film 39 and reach the source region 36 and the drain region 37 are formed. Form. Next, the via hole is filled with conductive plugs 40 and 41 made of tungsten (W) using a CMP method.

  Next, an etching stopper film 42 having a thickness of 30 nm made of a silicon oxycarbide film having a relative dielectric constant of 3.6 is formed on the interlayer insulating film 39 by, for example, a CVD method using tetramethylsilane and carbon dioxide as source gases. To do.

  Next, a liquid silica-based composition containing water is applied onto the etching stopper film 42 by a coating method, and after coating, curing is performed at 400 ° C. for 60 minutes, so that the k value mainly composed of MSQ is obtained. An interlayer insulating film 43 made of 2.4 or less porous silica is formed.

  Next, after forming the cap film 44, a plurality of wiring trenches or connection conductor recesses are formed in the cap film 44, the interlayer insulating film 43, and the etching stopper film 42. Next, after burying with a barrier metal layer made of Ta and a Cu film, the connection conductor 45 is formed by polishing by a CMP method.

  Next, an etching stopper layer 42, an interlayer insulating film 43, and a cap film 44 are formed again, and then a plug 46 and a connection conductor 47 connected to the plug 46 are formed using a dual damascene method. In other regions, plugs and wirings connected to the plugs are formed. By repeating this process as appropriate (three times in the figure), a multilayer wiring structure is formed.

  Next, as shown in FIG. 14B, a lower electrode 48 made of a Ta film having a thickness of 10 nm and an Al film having a thickness of 40 nm is formed on the cap film 44 by sputtering. Subsequently, an antiferromagnetic layer 49 made of a PtMn film having a thickness of 15 nm and a pinned layer 50 made of 2 nm CoFeB / 1 nm Ru / 3 nm CoFeB are formed. Subsequently, a tunnel insulating film 51 made of MgO having a thickness of 1 nm, a free layer 52 made of CoFeB having a thickness of 2 nm, and a cap layer 53 made of Ta having a thickness of 1 nm are formed. As these film forming conditions, the gas pressure of Ar gas is 0.2 Pa, and the power is 500 W.

  Next, an etching stopper film 54 made of Ru having a film thickness of 10 nm is formed with the Ar gas pressure raised to 0.5 Pa. At this time, since the gas pressure is increased, the etching stopper film 54 has a tensile stress of +200 MPa or more, and functions as a stress adjustment layer.

Next, the Ar gas pressure is returned to 0.2 Pa and a hard mask 55 made of Ta having a film thickness of 80 nm is formed, and then a SiO ₂ film having a film thickness of 50 nm is formed by CVD to form an insulating hard The mask 56 is used.

Next, as shown in FIG. 15C, a resist having a thickness of 200 nm is applied, and ArF exposure is performed to form a rectangular resist pattern 57 of 50 nm × 150 nm. Next, the insulating film hard mask 56 is etched using the resist pattern 57 as a mask. As an etching condition at this time, an RF power of 800 W is applied under a pressure of 10 Pa with CF ₄ flowing at 100 sccm.

Next, as shown in FIG. 15D, after the resist pattern 57 is removed by ashing, the hard mask 55 is etched using the insulating film hard mask 56 as a mask. The ashing condition at this time is performed by flowing O ₂ gas at 100 sccm and applying RF power of 200 W under a pressure of 10 Pa. Etching conditions for the hard mask 55 are performed by applying an RF power of 500 W under a pressure of 2 Pa with a Cl ₂ gas flow of 20 sccm and a BCl ₃ gas of 60 sccm. In the etching of the hard mask 55, the etching is stopped on the etching stopper film 54 so that the magnetoresistive element portion is not oxidized in a second ashing process described later.

Next, a _second ashing process is performed by flowing 300 sccm of O ₂ gas and applying RF power of 300 W under a pressure of 10 Pa. At this time, the etching stopper film 54 is etched by about 5 nm.

Next, as shown in FIG. 15E, the etching stopper film 54 to the antiferromagnetic layer 49 are etched using the hard mask 55 as a mask to expose the lower electrode 48. Etching conditions at this time are performed by flowing CH ₃ OH gas at 100 sccm and applying RF power of 800 W under a pressure of 2 Pa.

  Next, as shown in FIG. 16F, an insulating film 58 serving as a cover film made of SiC having a film thickness of 24 nm is formed by using the CVD method, and the film thickness on the lower electrode 48 is reduced to that of the free layer 52. The film is formed to exceed the height. At this time, the film is formed under the condition of a compressive stress of 1 GPa or more.

  Next, as shown in FIG. 16G, a tri-level resist composed of a lower layer resist 59, an SOG film 60, and a resist 61 having a thickness of 200 nm is provided, and a rectangular pattern having a size of 200 nm × 300 nm is formed by Ar exposure. .

Next, as shown in FIG. 17H, the insulating film 58 is etched using the resist pattern having the trilevel structure as a mask. As etching conditions at this time, CF ₄ gas is allowed to flow at 100 sccm, and RF power of 800 W is applied under a pressure of 5 Pa.

Next, as shown in FIG. 17I, after the lower electrode 48 is etched, the resist pattern is removed by ashing. Etching conditions at this time are performed by applying an RF power of 500 W under a pressure of 2 Pa with a flow of 20 sccm of Cl ₂ gas and 60 sccm of BCl ₃ gas. The ashing condition is performed by flowing O ₂ gas at 100 sccm and applying RF power of 200 W under a pressure of 10 Pa.

  Next, as shown in FIG. 18J, a barrier insulating film 62 made of SiC having a thickness of 20 nm is formed by CVD.

Next, as shown in FIG. 18K, an interlayer insulating film 63 made of SiO ₂ having a thickness of 400 nm is deposited, and then planarized by CMP to expose the top surface of the hard mask 55. At this time, the film is formed under a condition having a compressive stress of 500 MPa or more.

Next, as shown in FIG. 19L, an interlayer insulating film 64 made of SiO ₂ having a thickness of 200 nm is deposited on the entire surface by CVD.

  Next, as shown in FIG. 19M, a resist pattern 65 having a recess 66 is formed in the interlayer insulating film 64, and a via 67 is formed by etching using the resist pattern 65 as a mask.

  Next, as shown in FIG. 20 (n), after removing the resist pattern 65, a new resist is applied to form a resist pattern 68 having recesses 69 and 70, and a recess 71 is formed in the interlayer insulating film 64 by etching. , 72 are formed.

  Next, as shown in FIG. 20 (o), after the resist pattern 68 is removed, the via 67 and the recesses 71 and 72 are filled with a Cu plating film by a Cu electrolytic plating method, and then planarized by a CMP method to form the upper electrode 73. To complete the basic process flow. In the via 67 and the recess 71, a plug 74 and a wiring 75 connected to the plug 74 are formed. Thereafter, a bit line and the like connected to the upper electrode 73 are formed, and a necessary multilayer wiring structure is formed.

In Example 1 of the present invention, compressive stress is applied to the free layer by the etching stopper film that also serves as the stress adjustment layer and the cover insulating film. As shown in FIG. 9, a metal having a large linear thermal expansion coefficient is used. A film may be interposed. In the case of etching the metal film, for example, 100 sccm of Cl ₂ and 10 sccm of O ₂ are supplied and 400 W RF power is applied under a pressure of 5 Pa.

  In Example 1, since CoFeB having a negative magnetostriction constant λ is used as the free layer, compressive stress is applied to the free layer by the etching stopper film and the cover insulating film, but the magnetostriction constant λ of the free layer is applied. When a positive material is used, reverse stress is applied. That is, the etching stopper film may be formed to have a compressive stress so that a tensile stress is applied to the free layer and the cover insulating film has a tensile stress.

Here, the following supplementary notes are attached to the embodiment of the present invention including the first embodiment.
(Supplementary Note 1) An antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, a cap layer, an etching stopper film, a hard mask, and an upper electrode provided in this order on the lower electrode from the lower electrode side, and at least the free layer A magnetoresistive element comprising an insulating film provided on a side surface, wherein a product of a stress of the etching stopper film and a magnetostriction constant of the free layer is negative.
(Additional remark 2) The absolute value of the stress of the said etching stopper film | membrane is 200 Mpa or more, The magnetoresistive element of Additional remark 1 characterized by the above-mentioned.
(Supplementary Note 3) An antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, a cap layer, an etching stopper film, a hard mask, and an upper electrode provided in this order on the lower electrode from the lower electrode side;
A magnetoresistive element having an insulating film provided on at least a side surface of the free layer, wherein the product of the stress of the insulating film and the magnetostriction constant of the free layer is positive and the absolute value is 1 GPa or more.
(Appendix 5) The thickness of the flat portion of the insulating film is a thickness that does not exceed the position of the etching stopper film, and the product of the magnetostriction constant of the free layer is positive in the flat portion of the insulating film. 4. The magnetoresistive element according to any one of appendix 1 to appendix 3, wherein the magnetoresistive element includes a metal film having stress.
(Additional remark 5) The product of the process which forms an antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, and a cap layer in order on a lower electrode, and the magnetostriction constant of the said free layer on the said cap layer A step of forming an etching stopper film under a condition having a negative stress, a step of forming a hard mask on the etching stopper film, the lower electrode, an antiferromagnetic layer, a pinned layer, a tunnel insulating film, and a free layer And a step of depositing an insulating film so as to cover the cap layer, the etching stopper film and the hard mask, and a step of forming an upper electrode on the hard mask.
(Appendix 6) A step of forming an antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, a cap layer, an etching stopper film, and a hard mask in this order on the lower electrode, and a hard mask on the etching stopper film The lower electrode, the antiferromagnetic layer, the pinned layer, the tunnel insulating film, the free layer, under the condition that the product of the film forming step and the magnetostriction constant of the free layer is positive and the stress has an absolute value of 1 GPa or more, A method of manufacturing a magnetoresistive element, comprising: depositing an insulating film so as to cover a cap layer, an etching stopper film, and a hard mask; and forming an upper electrode on the hard mask.
(Appendix 7) The step of depositing the insulating film is a step of depositing so that the thickness of the flat portion of the insulating film does not exceed the position of the etching stopper film, and at least the insulating film 7. The method of manufacturing a magnetoresistive element according to appendix 5 or appendix 6, characterized in that it includes a step of depositing a metal film on a flat portion under a condition having a stress that makes a product of the magnetostriction constant of the free layer positive.
(Appendix 8) A semiconductor memory device using the magnetoresistive element according to any one of appendices 1 to 4 as an information storage unit of a memory cell.

11 Underlying insulating film 12, 48 Lower electrode 13, 49 Antiferromagnetic layer 14, 50 Pinned layer 15, 51 Tunnel insulating film 16, 52 Free layer 17, 53 Cap layer 18, 54 Etching stopper film 19, 55 Hard mask 20, 58 Insulating film 21, 63, 64 Interlayer insulating film 22, 73 Upper electrode 23, 56 Insulating film hard mask 24, 57 Resist pattern 25, 59 Lower resist 26, 60 SOG film 27, 61 Resist 28 Second interlayer insulating film 29 Recess 30 Metal film 31 Silicon substrate 32 Element isolation insulating film 33 MOSFET
34 Gate insulating film 35 Gate electrode 36 Source region 37 Drain region 38 Side wall 39 Interlayer insulating films 40 and 41 Conductive plug 42 Etching stopper film 43 Interlayer insulating film 44 Cap film 45 Connecting conductor 46 Plug 47 Connecting conductor 62 Barrier insulating film 65 , 68 Resist pattern 66, 69, 70, 71, 72 Recess 67 Via 74 Plug 75 Wiring

Claims (5)

An antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, a cap layer, an etching stopper film, a hard mask, and an upper electrode provided in order from the lower electrode side on the lower electrode;
An insulating film provided on at least a side surface of the free layer;
A magnetoresistive element characterized in that a product of a stress of the etching stopper film and a magnetostriction constant of the free layer becomes negative. An antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer, a cap layer, an etching stopper film, a hard mask, and an upper electrode provided in order from the lower electrode side on the lower electrode;
An insulating film provided on at least a side surface of the free layer;
The magnetoresistive element characterized in that the stress of the insulating film has a positive product with the magnetostriction constant of the free layer and an absolute value of 1 GPa or more. The thickness of the flat portion of the insulating film is a thickness that does not exceed the position of the etching stopper film,
3. The magnetoresistive element according to claim 1, wherein a metal film having a stress that makes a product of a magnetostriction constant of the free layer positive is provided on a flat portion of the insulating film. Forming an antiferromagnetic layer, a pinned layer, a tunnel insulating film, a free layer and a cap layer in order on the lower electrode;
Forming an etching stopper film on the cap layer under a condition having a stress that makes a product of the magnetostriction constant of the free layer negative;
Forming a hard mask on the etching stopper film;
Depositing an insulating film to cover the lower electrode, antiferromagnetic layer, pinned layer, tunnel insulating film, free layer, cap layer, etching stopper film and hard mask;
And a step of forming an upper electrode on the hard mask. 4. A semiconductor memory device, wherein the magnetoresistive element according to claim 1 is used as an information storage unit of a memory cell.

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