KR20090008240A - Dry etch stop process for elimination electrical shorting in mram device structures - Google Patents

Abstract

The present invention relates generally to semiconductor fabrication and particularly to fabricating magnetic tunnel junction devices. In particular, this invention relates to a method for using the dielectric layer in tunnel junctions as an etch stop layer to eliminate electrical shorting that can result from the patterning process.

Description

DRY ETCH STOP PROCESS FOR ELIMINATION ELECTRICAL SHORTING IN MRAM DEVICE STRUCTURES

FIELD OF THE INVENTION The present invention relates generally to semiconductor fabrication, and in particular to device structure fabrication comprising magnetic tunnel junction devices and thin film stacks of metal-insulator-metal layers such as those used in memory devices. will be.

Laminate films of metal-insulator-metal are used as storage elements in memory devices such as magnetic random access memories (MRAM) and the like. The memory device of the MRAM technology is a patterned structure of a multi-layered material, usually composed of a stack of different materials such as NiFe, CoFe, PtMn, Ru, and the like, and may include materials such as insulators such as Al ₂ O ₃ or MgO. have. A typical stack may include ten or more layers of these materials, some of which are non-magnetic, some are magnetic, and one or two are insulators, ten or more. It will include layers of materials. In this description, insulating films are defined as layers of oxide or metal nitride that exhibit high electrical resistance in their bulk form. In order to fabricate the storage device, it is necessary to laminate the materials on the upper blanket films, to create a patterned layer of photoresist, and to etch the films to a suitable structure.

Ion beam milling or ion beam etching methods have been used to remove magnetoresistive materials. However, ion beam milling is a physical milling method. Areas not protected by the mask are removed by ion bombardment. The ion bombardment sputters or shaves off the unprotected material. Ion beam milling is done at low selectivity, and stack regions near the edge of the mask or near the boundary of the MRAM cell body can easily be damaged.

Chemical etching techniques have been used to selectively remove some of the stacked layers. Examples of etching techniques include dry etching techniques and wet etching techniques.

One drawback of current etching techniques is that the profiles of MRAM structures are sensitive to electrical shorts across thin tunnel junctions. Vertical separation between the upper magnetic layer above the insulating dielectric tunneling layer and the lower magnetic layer below this tunneling layer is not suitable to prevent electrical shorting.

Embodiments of the invention relate to the manufacture of a magnetic tunnel junction (MTJ) device, among others, in which the tunnel barrier layer acts as a stop layer during plasma overeching of the upper magnetic layer. The resulting MTJ device provides better electrical isolation across the tunnel barrier layer.

In another embodiment, the gases used during plasma overetch exclude preferably halogen containing species that cause high selectivity etching on the upper magnetic layer overlying the tunnel barrier layer. Injecting oxygen into the gas improves the reproducibility of the method.

In another embodiment, a fluorine-chlorine gas mixture is used to partially etch the magnetic layer over the tunnel barrier layer.

Finally, another embodiment is directed to performing a corrosive plasma treatment with He and H ₂ gases prior to or during stripping the photoresist mask. Optionally, rinsing with water, He, H ₂ dehydration baking may be used after the stripping step.

Figure 1. A typical MRAM structure with magnetic tunneling junctions.

2. Simplified MRAM structure with magnetic tunneling junction.

Figure 3. MRAM process sequence of the invention.

4. MRAM process flow chart of the invention.

Figure 5a. MRAM process flow chart of the invention.

Figure 5b. MRAM process flow chart of the invention.

6. MRAM stack structure after top contact patterning.

7. The MRAM stack structure after the reactive magnetic layer etching step.

8. MRAM stack structure after reactive magnetic layer etching.

9. An embodiment of the patterning sequence of the present invention wherein the tunneling dielectric layer is not breached in proximity to the feature and is breached in regions not in proximity to the mask feature.

10. An embodiment of the MRAM patterning sequence of the present invention wherein the magnetic stack layers are etched with an intentionally inclined profile during the reactive etch step prior to the etch stop process.

NiFe/15

알루미나/50

NiFe 스택 구조체의 식각 동안 획득되는 광학적 방사(optical emission) 신호 강도의 도면. 상기 도면의 두개의 피크(peak)는 두 NiFe층의 제거를 나타낸다. 두 피크사이의 시간은 상기 15

알루미층을 제거하기위해 필요한 시간을 나타낸다. 이 그래프를 만들기 위해 사용된 방법으로부터 얻어지는 NiFe 대 알루미나(NiFe-to-Alumina)의 식각 선택도는 90:1보다 크다. Fig. 50

NiFe / 15

Alumina / 50

Plot of optical emission signal strength obtained during etching of a NiFe stack structure. Two peaks in the figure indicate removal of the two NiFe layers. The time between the two peaks is above 15

The time required to remove the aluminium layer The etching selectivity of NiFe-to-Alumina obtained from the method used to make this graph is greater than 90: 1.

12. Graph of each of the etch sputter velocities for CoFe, NiFe, and alumina.

13. MRAM stack structure after reactive magnetic layer etching (see FIG. 6) and etch stop step.

14. MRAM stack structure after reactive magnetic layer etching (see FIG. 7) and etch stop step.

15. MRAM stack structure after reactive magnetic layer etching (see FIG. 8) and etch stop step.

The present invention is based on the development of a patterning method for manufacturing a magnetic tunnel junction (MTJ) device for use in a magnetic random access memory (MRAM) device. As will be described further herein, an important aspect of the present invention is that an MJT device prepared by the method of the present invention provides better electrical insulation between the magnetic layers in contact with the dielectric tunnel layer when compared to current technology. To make it possible.

 A typical MRAM structure with MTJ is shown in FIG. The MRAM structure is a composite stack having a magnetic film, a conductive film, and an insulating film on a substrate. In FIG. 1, specific elements of a typical MRAM structure are shown, which consist of a substrate 10, a barrier layer 12, a lower contact layer 14, CoFe, Ru, NiFe, IrMn, PtMn and the like. Multilayer magnetic structure 16, dielectric tunnel layer 18, such as alumina or MgO, switchable magnetic layer 20 (NiFe, CoFe, CoNiFe, CoFeB classes), and upper contact layer 22 (Ta, TaN, Ti) , TiN, W class).

Also shown in FIG. 1 is a hard mask layer 24, an antireflective coating 26, and a patterned layer 28 of photoresist. Photoresist layer 28 is a photosensitive material, which is a mask for etching one or more of the underlying layers below the photoresist so that a portion of the underlying layer that is not protected by the resist layer can be etched. Commonly used by them. Antireflective coatings 26 are commonly used to absorb radiation to create optically opaque films to enhance the contrast of the image resist. ARC coatings can effectively reduce the reflection of radiation into the upper PR mask layer. This can prevent overexposure of the photoresist material. The hard mask layer 24 is widely used as an intermediate mask transfer layer in device fabrication. When used, the photoresist is used as a dry etch mask for transferring the pattern to the hard mask layer, and possibly to one or more of the underlying layers, after which the hard mask layer is defined using a photoresist. It is used as a mask for transferring the pattern to the remaining lower layers that are not. Hard mask layers such as silicon dioxide and silicon nitride can be processed to improve durability compared to photoresist or at temperatures above the softening point of polymeric phtoresist layers. It is generally used to make it possible.

The magnetic stack structure is typically created on the substrate 10. The substrate 10 may include any structure having an exposed surface. The structures are semiconductors doped with silicon wafers, silicon-on insulators (SOIs), silicon-on sapphire (SOS), aluminum titanum carbide (AlTiC) And undoped semiconductors, III-V or III-VI semiconductors, epitaxial layers of silicon supported by a base semiconductor base, and other semiconductor structures. . The semiconductor need not be silicon-based. The semiconductor may be silicon-germanium, germanium, or gallium arsenide. The structure may also be a non-semiconductor, such as glass or a polymer. The substrate 10 may include such embedded electronic devices such as transistors, diodes, capacitors, and resistors, or any other device or circuit element that may be used in conjunction with a magnetic multilayer stack.

In a typical multilayer MRAM structure including MTJ, shown in FIG. 1, it can be seen that the specific layers (eg, materials and their arrangement) that produce the multilayer structure may vary. MTJ and MRAM structures are known in the art, see, eg, US Pat. No. 6,673,675 (Yates, et al.) "Methods of Fabricating an MRAM Device Using Chemical Mechanical Polishing"; U. S. Patent No. 6,677, 165 to Lu, et al. "Magnetoresistive Random Access Memory (MRAM) Cell Patterning"; Gurney, et al., “Magnetic Memory with Tunnel Junction Memory Cells and Phase Transition Material for Controlling Current to the Cells”; US Pat. No. 6,024,885 to Pendharkar, et al., “Process for Patterning Magnetic Films”; US 5,650,958 (Gallagher, et al.) “Magnetic Tunnel Junctions with Controlled Magnetic Response”; Is explained in. These documents are incorporated herein by reference.

It should be understood that the orientation of the magnetic film stack may be reversed to the order shown in FIG. 1. That is, the direction of the film structure is in the reversed order in which the upper contact layer and the self-free layer are located below the dielectric tunnel layer and the fixed multilayer and the antiferromagnetic layers are located above the dielectric tunnel layer. It may be in the same orientation as the film stack is laminated. It should also be understood that the magnetic film stack may be composed of multiple magnetic tunnel junctions in orientations where the self-free layer is stacked over or below the dielectric tunnel layer.

In one simplified embodiment shown in FIG. 2, the MTJ stack comprises a substrate 10, a bottom contact layer 14, a fixed bottom magnetic layer 16, a dielectric tunnel layer 18, a switchable top magnetic layer. Layer 16, and top contact layer 22. The stack structure is patterned with a photoresist layer 28. This simplified structure is used in the preferred embodiments of the present invention in the following description.

An etch stop step procedure of the present invention is shown in FIGS. 3, 4 and 5.

3 shows that the magnetic stack is stacked (100), the PR is patterned (102), one or both of the hardmask layer and the top contact layer are etched (104), and the top magnetic layer ( The process sequence of the invention of 106 where a reactive etching process is used to remove a portion of 106 is shown. Following the reactive etching step of the upper magnetic layer 106, the MTJ device structure is either directly exposed to the etch stop step 108 of the present invention or first subjected to a corrosion treatment step consisting of DI rinse, PR strip, and plasma based corrosion treatment. Are exposed, followed by the etch stop step 108 of the invention.

In one embodiment shown in FIG. 3, immediately following the reactive partial etching step 106 of the upper magnetic layer, followed by the etch stop step 108 of the present invention, the patterning of the MTJ device structure is completed and the device is subjected to the subsequent step ( Go to 114). In a second embodiment where the etch stop step 108 of the invention follows the reactive partial etch step 106 of the upper magnetic layer, the device is exposed to a step for corrosion protection. Exposing the magnetic film to chlorine-containing and bromine-containing etching chemicals may cause a reverse reaction as the device is removed from the vacuum and subsequently exposed to the ambient moisture of the etched film. Depending on the sensitivity of the film, various orders have been developed, such as shown in Figure 3, to prevent reverse corrosion reactions.

In one embodiment of the inventive process wherein anticorrosive treatments are used, which are used after the etch stop step 108 on the tunnel layer, the corrosion treatment sequence is a photoresist (PR) strip / corrosive treatment 112 followed by a DI water rinse step 110. In a second embodiment of the process of the present invention wherein an anticorrosion treatment is used and this corrosion protection treatment is used after the etch stop step 108 of the tunnel layer, the anticorrosion treatment sequence comprises a photoresist strip / corrosion prevention step 112 and This is followed by a DI water rinse step 110.

In one embodiment shown in FIG. 3, the etch stop step 108 of the present invention does not immediately follow the reactive partial etch step 106 of the upper magnetic layer, and the anti-corrosion treatment (110) and (112) It will run before this. In the first embodiment shown in FIG. 3 where the etch stop step 108 of the present invention does not immediately follow the reactive partial etch step 106 of the upper magnetic layer, the MTJ device structure is exposed to the DI water rinse step 110. And a photoresist strip / corrosion treatment step 112 followed by an etch stop step 108 above the tunneling layer. In a second embodiment of the process of the invention where the etch stop step 108 does not immediately follow the reactive partial etch step 106 of the upper magnetic layer, the device is exposed to the photoresist strip / corrosion treatment step 112 and The DI water rinse step is followed by the etch stop step 108.

4 illustrates a process sequence of the invention in which a magnetic stack is stacked (100), the PR is patterned (102), and the hard mask is etched (103). Following the hard mask etching step 103, the MTJ device structure is exposed to the photoresist strip step 107 or the reactive etching step 105 for removing the upper contact layer and for removing a portion of the upper magnetic layer. Exposed to reactive etching step 106. In a first embodiment of the inventive process, wherein the hard mask etching step 103 is followed by a photoresist strip step 107, following the photoresist step 107, the MTJ device removes the upper contact layer. And a reactive etching step 106 for removing a portion of the upper magnetic layer. A second implementation of the process of the present invention following the hard mask etching process 103 followed by a reactive etching step 105 for removing the upper contact layer and a reactive etching step 106 for removing a portion of the upper magnetic layer. In an example, the MTJ device is subsequently exposed to photoresist stripping step 107.

The photoresist strip step 107, the reactive etching step 105 for removing the upper contact layer, and the step of removing the upper contact layer 106 for removing a portion of the upper magnetic layer are combined. The MTJ device is either directly exposed to the etch stop step 108 of the present invention, or first undergoes a corrosion treatment sequence consisting of DI rinse and plasma based corrosion treatment step 113 followed by the etch stop step 108 of the invention. Follow.

Photoresist stripping step 107 of the present invention may be followed by the etch stop step 108 immediately following the reactive partial etch step 106 of the upper magnetic layer, or prior to the reactive partial etch step 106 of the upper magnetic layer. In one embodiment shown in FIG. 4 following, the patterning of the MTJ device structure is completed and the device moves to a subsequent step 114. The photoresist strip step 107 of the present invention may be followed by the etch stop step 108 immediately following the reactive partial etch step 106 of the upper magnetic layer or through the reactive partial etch step 106 of the upper magnetic layer. In a second embodiment of the etch stop process of the present invention following hereinafter, the device is exposed to a process sequence to prevent corrosion. Exposing the magnetic film to chlorine-containing and bromine-containing etch chemistries may cause a reverse reaction as the device is removed from vacuum and subsequently exposed to the ambient moisture of the etched film. Depending on the sensitivity of the film, various sequences, such as those shown in FIG. 4, have been developed to prevent reverse corrosion reactions.

In an embodiment of the inventive process wherein an anticorrosive treatment is used, which is then used after the etch stop step 108 on the tunnel layer, the anticorrosion treatment sequence is a plasma based anticorrosion treatment step ( 112 followed by a DI water rinse step 110. In a second embodiment of the process of the present invention wherein an anticorrosion treatment is used and this anticorrosion treatment is used after the etch stop step 108 of the tunnel layer, the anticorrosion treatment sequence is a plasma based anticorrosion treatment step 112. Followed by a DI water rinse step 110.

In one embodiment shown in FIG. 4, the etch stop step 108 of the present invention does not immediately follow the reactive partial etch 106 of the upper magnetic layer, but rather the corrosion prevention treatment steps (110) and (113). Is preceded by this. In the first embodiment shown in FIG. 4 where the etch stop step 108 of the present invention does not immediately follow the reactive partial etch step 106 of the upper magnetic layer, the device is exposed to a plasma based corrosion treatment step 113. DI water rinse is followed by the etch stop step 108 above the tunnel layer.

Two approaches to the subsequent step 114 shown in FIGS. 3 and 4 are shown in FIGS. 5A and 5B. 5A and 5B illustrate two specific methods that specifically specify the unique characteristics obtained by the etch stop step 108 of the present invention.

In FIG. 5A, a spacer is used to passivate sidewalls of the MTJ device structure for the purpose of preventing electrical shorts during subsequent processing. The sidewall spacers are used in connection with an etch stop process as described by the etch stop step 108 shown in FIGS. 3 and 4. In a preferred embodiment, the subsequent step 114 described by FIGS. 3 and 4 is a spacer dielectric deposition step 130, a spacer etch step 132, and a lower magnetic layer / bottom contact layer etch to complete the process. Step 134, or a DI water rinse step and a plasma based anti-corrosion treatment step 142 are followed by a bottom magnetic layer / bottom contact layer etch step 134. Alternatively, the plasma based anti-corrosion treatment step 142 may be performed before the DI water rinse, as shown in FIG. 5A, before the subsequent step 150 of the device proceeds.

In FIG. 5B, an insulating hard mask layer such as silicon dioxide or silicon nitride is stacked 120, a photoresist is patterned 122, the hard mask is etched 124, and the photoresist is stripped. Another embodiment of a subsequent step 114 is shown, including step 126 and step 128 where the lower magnetic layer and the lower contact layer are etched. In this manner, the photoresist patterning is performed by the silicon dioxide or silicon nitride hard mask layer using an original hard mask etching step 103, an upper contact etching step 105, a reactive upper magnetic layer etching step 120, and an etch stop step. And extend laterally beyond the vertical sidewalls generated from 108. The lateral extension of the hard mask 120 beyond the vertical sidewall is such that the sidewalls of the original hard mask, the top contact, and the top magnetic layer are covered with the hard mask layer 120 after etching 124 of the hard mask layer. It should be done so that it remains true.

The layers comprising the MRAM stack or other magnetic device structure are stacked 100 using techniques employed by those skilled in the art of film lamination. The films may be deposited by physical vapor deposition, chemical vapor deposition, atomic layer deposition, nanolayer deposition, atomic layer deposition, evaporation, and other techniques. The film of the stack may be laminated in one form by one of these methods and may be later altered in the second chamber. For example, an aluminum (Al ₂ O ₃ ) dielectric can be produced by stacking an aluminum layer and then exposing the aluminum to an oxidation process for producing alumina. Similarly, MgO can be produced by stacking a magnesium layer and then exposing the Mg to an oxidation process for MgO production.

Photoresist stacking and patterning step 102 is used to form a pattern for defining the MTJ or MRAM structure. Although not shown in the simplified MRAM stack example of FIG. 2, an antireflective coating can be used in conjunction with the photoresist to improve the accuracy of the pattern transfer. In addition, a hard mask layer may be included between the photoresist and the upper contact layer. Hard mask layers such as silicon dioxide and silicon nitride may be used. In another embodiment, the thickness of the conductive top contact layer should be made available for both purposes of the hard mask layer and the top contact layer. 2 shows a simplified MRAM stack structure after the magnetic stack deposition step 100 and subsequent photoresist patterning step 102.

In a preferred embodiment, the hard mask layer and the top contact layers are patterned 103 by those skilled in the art using common techniques. One common process for reactively etching silicon oxide hard masks is to use a mixture of CHF ₄ and Ar if present. Oxide etching processes are widely shown in the literature. Similarly, an example of the process chemistry commonly used to conformally etch 104,105 the upper conductive layer is to use a mixture of Ar / Cl ₂ . That is, metal contact layer etchings have been disclosed in detail in the literature. Oxide and nitride hard masks and metal contact layers have been used for a long time, and the technique used to remove these layers will be apparent to those skilled in the art. The simplified MRAM stack structure after contact etching will be shown in FIG. 6.

The removal of the magnetic layers found in the magnetic multilayer stack is not well established in the art. The use of a process that is particularly suitable for the reactive top magnetic layer etching step 106 in conjunction with the etch stop step 108 is within the scope of the present invention. In step 106 of the present invention, a chlorine-containing gas mixture such as Cl ₂ , BCl ₃ , and HCl and a fluorine-containing gas mixture such as CF ₄ , SF ₆ , and CHF ₃ for removing a portion of the upper magnetic layer are removed. It is configured to include. Alternatively, gas molecules containing Cl and F atoms can also be used. The ratio of chlorine-containing gas to fluorine-containing gas should be in the range from 2: 1 to 20: 1. Typical process conditions for the reactive etching step 106 described in the Spectra® inductive coupling process manufactured by Tegal Corporation are: 400 W rf power of 13.56 MHz on an induction source coil. , 450 kHz 20 W rf power applied on the substrate, 40 ccm Cl ₂ , 8 ccm CF ₄ , and ₄ mT process pressure. to be. The simplified MRAM stack structure after the reactive magnetic layer etching step 106 is shown in FIG.

범위 가 되도록 상기 상부 자기층을 제거하게 해 줄 것이다. Further addition of fluorine to the chlorine-containing etch process produces a smooth etch surface (such as shown in FIG. 8) and Cl species through very thin magnetic material films remaining after the reactive top magnetic layer etching step 106. It has been known to prevent the spread of chlorine species. The use of a fluorine / chlorine-containing gas mixture is 5-25 at the interface between the remaining upper magnetic layer and the lower dielectric tunnel layer.

This will allow the upper magnetic layer to be removed.

In a preferred embodiment of the upper magnetic layer etching step 106 of the present invention, the remaining upper magnetic layer is a subsequent process such as an etch stop step 108, a DI water rinse step 110 or a PR strip / corrosion treatment step 112, and the like. Prior to moving to, it will be etched as close as possible to the interface between the remaining top magnetic layer 20 and the bottom dielectric layer 18 without penetrating the tunneling dielectric layer near the feature. In a preferred embodiment, the upper magnetic layer 20 will be uniformly etched during the reactive upper magnetic layer etching step 106 as shown in FIG. 7 and the lower dielectric layer 18 will not be breached anywhere on the wafer.

However, in one embodiment of the inventive process, the upper magnetic layer 20 is completely removed and the lower dielectric layer 18 is breached but not very close to the patterned MTJ stack features. In this embodiment of the process of the invention, the upper magnetic layer etch 106 is removed in an etch process comprising one or more of the following gases or gas mixtures: Cl ₂ , CL ₂ / Ar, Cl ₂ / CF. ₄ , Cl ₂ / CHF ₃ , Cl ₂ / Ar, BCl ₃ / Cl ₂ , BCl ₃ / Cl ₂ / Ar, BCl ₃ / HBr, BCl ₃ / HBr / Ar, NH ₃ , NH ₃ / CO.

In another embodiment, the upper magnetic layer 20 is completely removed, and the lower dielectric layer 18 is also removed outside the inclined region where it is very close to the patterned MTJ stack, and the lower magnetic layer 16 All or part of and all or part of the lower contact layer 14 are also removed (see FIG. 10). No subsequent step 114 is required. In this embodiment of the process of the invention, the upper magnetic layer etch 106 is removed in an etch process comprising one or more of the following reactive gases or gas mixtures. : Cl ₂ , CL ₂ / Ar, Cl ₂ / CF ₄ , Cl ₂ / CHF ₃ , Cl ₂ / Ar, BCl ₃ / Cl ₂ , BCl ₃ / Cl ₂ / Ar, BCl ₃ / HBr, BCl ₃ / HBr / Ar, NH ₃ , NH ₃ / CO.

Some of the remaining upper magnetic layer is not removed in the reactive step 106. The aforementioned embodiment is a non-reactive gas mixture (such as oxygen) such as argon and oxidizing gas, whereby the dielectric of the tunnel barrier layer acts as a stop layer. In a preferred embodiment, the flow of inert gas is typically in the range of 10 to 350 sccm and the flow of the oxygen-containing gas is in the range of 0.02 to 0.15 sccm. Substantial flows for the oxygen-containing gas may vary depending on the flow of inert gas, the choice of oxygen-containing gas, and the type of plasma system used. A typical step 108 used in a Spectra® Inductively Coupled Etch Process Module manufactured by Tegal Corporation is as follows for a 200 mm diameter silicon substrate: 100 W rf power of 13.56 MHz on a source coil, substrate Applied to 450kHz 20W power, 350sccm Ar, 0.08scm O2, and 10mT process pressure. The conditions for etch stop presented above and the sputtering step 108 are exemplary of the conditions found to produce a sputter selectivity of ˜90: 1 between NiFe and alumina in a Spectra ICP process module manufactured by Tegal Corporation. It is intended to provide a set (see Figure 11).

A range of process conditions and chamber configurations can be used to produce high selectivity results between the upper magnetic material and the dielectric. Two aspects that must be considered to achieve high selectivity are the ratio control of inert gas to oxygen-containing gas and process operation at low bias power levels. These two aspects will be explained in more detail in the following paragraphs.

In a preferred embodiment, the etch stop process requires high selectivity (> 5: 1) between the upper magnetic layer 20 and the lower dielectric layer 18. The upper magnetic layer 20 is expected to be etched at a speed that is at least five times faster than the rate at which the lower dielectric layer 18 is etched. Precise NiFe / CoFe etch rate control is possible because of the large difference in sputtering thresholds between NiFe and CoFe and between oxides such as Al ₂ O ₃ and MgO. Experiments confirming these phenomena were performed using Spectra® process modules manufactured by Tegaluma (CA).

)으로 구성되었다. 측정된 알루미나 식각 속도들은 자기 터널 접합들을 포함하는 스택들에서 찾아볼 수 있는 박막 속성들을 나타냈다.Specifically, NiFe and CoFe sputter rates have been measured using single layer test wafers, and alumina etch rates have been measured using alumina / NiFe test structures. The test structure includes a substrate having a NiFe layer laminated thereon and a very thin alumina layer (~ 15) on the NiFe.

). The measured alumina etch rates showed thin film properties found in stacks containing magnetic tunnel junctions.

As is evident in the graph of FIG. 12, a large difference is found between the onset of sputtering for magnetic alloys and the sputtering onset for alumina. This difference was further observed in each speed test performed on alumina / NiFe test structures at bias power level conditions greater than 10 W and less than 25 W. These observations show that, under certain process conditions, only a small amount of alumina is removed during the same time, while large amounts of NiFe and CoFe can be etched from the TMR stack.

The resulting device profiles resulting from the above preferred embodiments of the reactive etching step 106 and the etch stop process 108 as shown in FIGS. 7, 9, and 10 are shown in FIGS. 13, 14, and 15. In each of these embodiments, the remaining metal layer remaining in the upper magnetic layer 20 after the reactive etching step 106 is removed from the lower dielectric layer 18. The removal of the upper magnetic layer 20 remaining after the low bias non-reactive etch stop step 108 and the reactive etch step 106 provides improved electrical performance over other known methods without damaging the lower dielectric layer 18. Provide insulation. Geometrical isolation is provided in each of the three embodiments of the inventive process without the risk of inherent electrical shorts that have been known to limit device performance of structures containing MTJ stacks. In addition, a better electrical short between the upper magnetic layer 20 and the lower magnetic layer 16 is achieved without the risk of using corrosive chemicals in the most dangerous step in producing a reliable device.

Typical process conditions for the etch stop step 108 provided above are intended to represent the process found to give very high selectivity between NiFe or CoFe and alumina. Various process conditions in the spectra reactors can be used in the scope of the etch stop step 108 of the present invention.

One or two of a first step of removing bulk of the upper magnetic layer using a mixture of chlorine and fluorine containing gas and a second step of using a mixture of inert gas and oxygen-containing gas to stop over the dielectric tunneling layer. Similar processes using a stepwise approach include devices from other inductively coupled plasma reactors, capacitively coupled plasma reactors, electron cyclotron resonance reactors, and magnetic films. It may also be carried out in other reactors used to make a plasma to produce a, such processes will be within the scope of the object of the present invention.

In addition, the use of the dielectric layer as an etch stop layer without the initial step of using a mixture of chlorine / fluorine containing-gas to remove the bulk of the upper magnetic layer would also be within the scope of the present invention.

The high selectivity of this embodiment for the etch stop step 108 between NiFe and alumina described above is observed using an argon and oxygen gas mixture. The use of the oxidizing elements of the argon / oxygen gas mixture used in the etch stop step 108 of the preferred embodiment at ˜90: 1 and the use of replaceable inert elements for the operation It is within the scope of the present invention. For example, helium, neon, krypton, and nitrogen may be used to provide the inert element of the etch stop step 108 instead of or in combination with argon. Similarly, oxygen substitutes such as N ₂ O, NO, CO and CO ₂ may be used instead of or in combination with oxygen to produce the oxidizing element of the etch stop step 108. Instead, within the scope of the process of the present invention, as discussed in the following paragraphs, the oxygen-containing gas may be removed by controlling the oxygen level in the etching chamber by means other than the intentional injection of the oxygen-containing gas.

When plasma sputtering magnetic layers are composed of transition metals such as NiFe and inert sputtering gases such as Ar, regulating the amount of oxygen in the plasma chamber can affect the etch selectivity for the lower alumina. It has been proven. That is, by controlling the flow of oxygen into the plasma chamber, higher NiFe / alumina selectivity can be achieved. One embodiment of a plasma overetch process involves the result of re-introducing oxygen together into the plasma chamber in a predictable and controllable manner, while reducing the background oxygen to a level that does not affect the etching process. The sources of background oxygen entering the plasma chamber include, for example: (1) sputtering of oxygen-containing inner chamber parts, (2) oxygen in the atmosphere; (3) removing gas from the materials of the chamber; And (4) other process modules of the present process system.

When the "uncontrolled" background oxygen in the chamber is reduced, the selectivity between NiFe and alumina can be optimized by re-introducing a very small amount of oxygen (eg, ~ 0.08 sccm) into the chamber. . One technique for re-introducing the oxygen uses two separate carrier gas sources connected to the chamber. The second source supplies a gas containing 100% Ar in parallel to the chamber, while the first source supplies an Ar / O ₂ gas mixture consisting of 99.9% Ar and 0.1% O ₂ . It is supplied to the plasma chamber. When oxygen is re-introduced into the plasma chamber, it is desirable to lower the base pressure of the chamber to -0.001 mT or less. In addition, surface sputtering of the inner chamber parts should be minimized or controlled. For example, the conductive source power should be low (100-200 W) to minimize window sputtering. Excessive amounts of oxygen in the chamber can slow down the etch rate of the metallic magnetic film and result in a decrease in selectivity between the magnetic layers and the dielectric layers.

In the above and the second alternative technique, oxygen is introduced into the process chamber through an orifice separating the process chamber and the source of oxygen. The aperture is such that the flow of the oxygen containing gas, when mixed with an inert gas, improves the sputtering selectivity between the upper magnetic film and the tunneling dielectric.

/min 보다 빠른 속도로 제거되며 상기 유전체층은 1

/min보다 느린 속도로 제거될 수 있도록 조정될 것이다.Other methods for injecting a controlled concentration of oxygen into an inert gas are also within the scope of the present invention to provide the requirements for selectively etching the magnetic material over the dielectric layer. In such an embodiment, sputtering of the inner surfaces of the oxygen-containing materials in the plasma reactor is usable as a source of oxygen. In this embodiment, an inert gas such as argon is a mixture of inert gas and oxygen-containing species on the surface of the upper magnetic layer that is being etched to achieve selective removal between the magnetic material and the tunneling dielectric layers. The amount can be injected using conventional means such as a mass flow controller or a needle valve. The process conditions indicate that the magnetic material is 5

removed at a rate faster than / min and the dielectric layer is 1

It will be adjusted to be removed at a slower speed than / min.

In another embodiment of this invention, the concentration of the oxygen-containing gas is determined by controlling the background gas leakage. Plasma-based semiconductor fabrication processes are typically performed in the range of 0.1 to 1000 milliTorr. At conditions below this atmospheric pressure, oxygen can be inadvertently injected through incomplete sealing of the process chamber, through breathable materials, and from partial outgassing of the process chamber. Leak rate can be easily measured in conventional plasma processing equipment.

/min보다 빠른 속도로 제거하고, 상기 유전체층이 1

/min 보다 느린 속도로 제거할 수 있는 정도로 얻기 위해, 종래의 수단들을 통해 제어된 불활성 가스 흐름의 주입과 연계하여, 대기로부터 상기 산소-함유 누출을 제어하는 방식은 본 발명의 범주 내에 든다.In this embodiment, an inert gas such as argon is capable of producing mixtures of inert gas and oxygen-containing species on the surface of the upper magnetic layer being etched for selective removal of the magnetic material and the tunneling dielectric layers. As such, it may be injected using conventional methods such as a mass flow controller or a needle valve. The necessary mixture of inert gas and oxygen-containing species

removed at a rate faster than / min, and the dielectric layer is 1

In order to be able to remove at a rate slower than / min, the manner of controlling the oxygen-containing leak from the atmosphere, in conjunction with the injection of a controlled inert gas stream via conventional means, is within the scope of the present invention.

The process for removing the photoresist and preventing corrosion, i.e., 112 of FIG. 3, 113 of FIG. 4, 142 of FIG. 5A, and 126 and 142 of FIG. Can be applied. The use of suitable halogen-containing gas mixtures for the removal of resist and the corrosion protection that may be caused by exposure of the MRAM film stack to the halogen-containing etching chemicals is within the scope of the present invention. In a preferred embodiment, the magnetic film stack is exposed to a hydrogen-containing plasma, which is intended to remove the photoresist and to expose the magnetic layer to a process that will prevent corrosion as it is exposed to the atmospheric environment. Hydrogen is injected into the process chamber in the form of a mixture of hydrogen and an inert gas such as helium, neon, argon, or nitrogen.

Claims (81)

A method for fabricating a magnetic junction memory device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper metal layer on the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step occurs in a non-reactive gas environment and bias power between the upper metal layer and the insulating layer sputter threshold. And applying a bias to the substrate. The method of claim 1, And wherein said non-reactive gas is comprised of Ar, He, Ne, Kr, N2, or Xe and combinations thereof. The method of claim 1, And forming a lower metal layer under said insulating layer. The method of claim 1, And wherein the plasma is generated using a non-reactive gas. The method of claim 1, And wherein said insulating layer comprises aluminum oxide, magnesium oxide, or other insulating oxide. The method of claim 1, And wherein the upper metal layer comprises a magnetic layer, a portion of an MRAM stack structure, or one or more layers of NiFe, CoFe, CoNiFe, and CoFeB. A method for fabricating a magnetic junction memory device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper layer over the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step comprises a physical spurting step using a mixture of <1% of a non-reactive gas and an oxygen-containing gas. Method of manufacturing a magnetic junction memory device comprising a. The method of claim 7, wherein And wherein said non-reactive gas is comprised of Ar, He, Ne, Kr, N2, or Xe and combinations thereof. The method of claim 7, wherein And the oxygen-containing gas is made of O, O ₂ , N ₂ O, NO, air, CO and combinations thereof. The method of claim 7, wherein And the mixture is 99.9% Ar and 0.1% O ₂ . The method of claim 7, wherein A mixture of non-reactive gas and oxygen-containing gas is introduced through a first flow controller and non-reactive gas is introduced through a second flow controller. The method of claim 7, wherein Wherein the first flow controller provides 80 sccm of argon and 0.08 ccm of O ₂ and the second flow controller provides 270ccm of argon. The method of claim 7, wherein And wherein said non-reactive gas is in the range of 10 to 350 sccm and said oxygen-containing gas is in the range of 0.02 to 0.15 sccm. The method of claim 7, wherein Oxygen-containing gas is introduced into the process from the sputtering of a solid source of oxygen-containing solids. The method of claim 14, And said solid source comprises alumina or quartz. The method of claim 7, wherein Wherein the oxygen-containing gas flows from leak control from the environment. The method of claim 7, wherein And forming a lower magnetic layer under the insulating layer. The method of claim 7, wherein And a plasma is generated with the non-reactive gas. The method of claim 7, wherein And wherein said insulating layer comprises aluminum oxide, magnesium oxide, or other insulating oxide. The method of claim 7, wherein And wherein the upper magnetic layer comprises a magnetic layer, part of an MRAM stack structure, or one or more layers of NiFe, CoFe, CoNiFe, and CoFeB. A method for fabricating a magnetic junction memory device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper metal layer on the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step comprises: i) applying a bias to the substrate with a bias power between the upper metal layer and the sputter threshold of the insulating layer; And ii) physical sputtering with a mixture of non-reactive gas and <1% oxygen-containing gas. Method of manufacturing a magnetic junction memory device, characterized in that comprising a. The method of claim 21, And wherein said non-reactive gas is comprised of Ar, He, Ne, Kr, N2, or Xe and combinations thereof. The method of claim 21, And the oxygen-containing gas is a soldier consisting of O, O 2, N ₂ O, NO, air, CO, and combinations thereof. The method of claim 21, And the mixture is 99.9% Ar and 0.1% O2. The method of claim 21, A mixture of non-reactive gas and oxygen-containing gas is introduced through a first flow controller and non-reactive gas is introduced through a second flow controller. The method of claim 21, Wherein the first flow controller provides 80 sccm of argon and 0.08 ccm of O 2, and the second flow controller provides 270ccm of argon. The method of claim 21, And wherein said non-reactive gas is in the range of 10 to 350 sccm and said oxygen-containing gas is in the range of 0.02 to 0.15 sccm. The method of claim 21, Wherein the oxygen-containing gas is introduced into the process by sputtering an oxygen-containing solid. The method of claim 28, And said solid source comprises alumina or quartz. The method of claim 21, Wherein the oxygen-containing gas flows from leak control from the environment. The method of claim 21, And forming a lower magnetic layer under the insulating layer. The method of claim 21, And a plasma is generated with the non-reactive gas. The method of claim 21, And wherein said insulating layer comprises aluminum oxide, magnesium oxide, or other insulating oxide. The method of claim 21, And wherein the upper magnetic layer comprises a magnetic layer, part of an MRAM stack structure, or one or more layers of NiFe, CoFe, CoNiFe, and CoFeB. As a method for manufacturing a device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper metal layer on the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step occurs in a non-reactive gaseous environment and biases between the upper metal layer and the insulating layer sputter threshold. And applying a bias to the substrate with electrical power. 36. The method of claim 35 wherein And wherein said insulating ts comprises insulating oxides. As a method for manufacturing a device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper layer over the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step comprises a physical sputtering step using a mixture of <1% of an inert gas and an oxygen-containing gas Device manufacturing method characterized in that. As a method for manufacturing a device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper layer over the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step comprises: i) applying a bias to the substrate with a bias power between the upper metal layer and the sputter threshold of the insulating layer; And ii) Physics using a mixture of non-reactive gases and <1% oxygen-containing gas          Enemy sputtering stage. Device manufacturing method characterized in that it comprises a. A method for fabricating a magnetic junction memory device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper layer over the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step occurs in a non-reactive gas environment and biases between the upper metal layer and the sputter threshold of the insulating layer. And applying a bias to the substrate as a power source. The method of claim 39, Wherein said chlorine-containing gas comprises Cl ₂ , BCl ₃ , HCl, atomic chlorine-containing gas, or a combination thereof. The method of claim 39, And said fluorine-containing gas comprises CF ₄ , SF ₆ , CHF ₃ , atomic fluorine-containing gas, or a combination thereof. The method of claim 39, Chlorine-containing gas to fluorine-containing gas is in the range of 2: 1 to 20: 1. The method of claim 39, And wherein said non-reactive gas comprises Ar, He, Ne, Kr, N ₂ , or Xe or a combination thereof. The method of claim 39, And forming a bottom metal layer under the insulating layer. The method of claim 39, A plasma is produced with a non-reactive gas. The method of claim 39, And wherein said insulating layer comprises aluminum oxide, magnesium oxide, or other insulating oxide. The method of claim 39, Wherein the upper metal layer comprises a magnetic layer, a portion of an MRAM stack structure, or one or more layers of NiFe, CoFe, CoNiFe, and CoFeB. As a method for manufacturing a device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper layer over the insulating layer; And (d) selectively removing the upper metal layer with respect to a lower insulating layer, wherein the selective removing step comprises: i) applying a bias to the substrate with a bias power between the upper metal layer and the sputter threshold of the insulating layer; And ii) physical sputtering with a mixture of non-reactive gas and <1% oxygen-containing gas. Device manufacturing method characterized in that it comprises a. The method of claim 48, Wherein said chlorine-containing gas comprises Cl ₂ , BCl ₃ , HCL, atomic chlorine-containing gas, or other combinations thereof. The method of claim 48, And said fluorine-containing gas comprises CF ₄ , SF ₆ , CHF ₃ , atomic fluorine-containing gas or other combinations thereof. The method of claim 48, The ratio of chlorine-containing gas to fluorine-containing gas is in the range of 2: 1 to 20: 1. The method of claim 48, And wherein said non-reactive gas is Ar, He, Ne, Kr, N ₂ , or Xe, or another combination thereof. The method of claim 48, And said oxygen-containing gas is O, O ₂ , N ₂ O, NO, air, CO or any other combination thereof. The method of claim 48, And the mixture is 99.9% Ar and 0.1% O ₂ . The method of claim 48, Wherein the mixture of non-reactive gas and oxygen-containing gas is injected through a first flow controller, and the non-reactive gas is injected through a second flow remover. The method of claim 48, Wherein said first flow controller provides argon 80 ccm and 0 ₂ 0.08 sccm and said second flow controller provides argon 270 sccm. The method of claim 48, And wherein said non-reactive gas is in the range of 10 to 350 sccm, and said oxygen-containing gas is in the range of 0.02 to 0.15 sccm. The method of claim 48, 10. A method of fabricating a magnetic junction memory device, characterized in that an oxygen-containing gas is injected into the process from sputtering a solid source of oxygen-containing solids. The method of claim 58, And said solid source comprises alumina or quartz. The method of claim 48, Wherein the oxygen-containing gas is injected from leak control from the atmosphere. The method of claim 48, And producing a bottom metal layer under said insulating layer. The method of claim 48, Wherein the plasma is generated with a non-reactive gas. The method of claim 48, And wherein said insulating layer comprises aluminum oxide, magnesium oxide, or other insulating oxide. The method of claim 48, Wherein the upper metal layer comprises a magnetic layer, part of an MRAM stack structure, or one or more layers of NiFe, CoFe, CoNiFe, and CoFeB. A method for fabricating a magnetic junction memory device, (a) providing a substrate; (b) forming an insulating layer on the substrate; (c) forming an upper layer over the insulating layer; And (d) removing a portion of the upper metal layer using a fluorine- and chlorine-containing gas mixture; And (E) selectively removing the remaining upper metal layer with respect to the lower insulating layer, wherein the selective removing step i) applying a bias to the substrate with a bias power between the upper metal layer and the sputter threshold of the insulating layer; And ii) a physical sputter process step using a mixture of non-reactive gas and <1% oxygen-containing gas. The method of claim 65, Wherein said fluorine-containing gas comprises Cl ₂ , BCL ₃ , HCL, atomic chlorine-containing gas, or other combinations thereof. The method of claim 65, And said fluorine-containing gas comprises CF ₄ , SF ₆ , CHF ₃ , atomic fluorine-containing gas, or other combinations thereof. The method of claim 65, The ratio of chlorine-containing gas to fluorine-containing gas is in the range of 2: 1 to 20: 1. The method of claim 65, And wherein said non-reactive gas is Ar, He, Ne, Kr, N ₂ , or Xe, or another combination thereof. The method of claim 65, And said oxygen-containing gas is O, O ₂ , N ₂ O, NO, air, CO or any other combination thereof. The method of claim 65, And the mixture is 99.9% Ar and 0.1% O ₂ . The method of claim 65, Wherein the mixture of non-reactive gas and oxygen-containing gas is injected through a first flow controller, and the non-reactive gas is injected through a second flow remover. The method of claim 65, Wherein said first flow controller provides argon 80 ccm and 0 ₂ 0.08 sccm and said second flow controller provides argon 270 sccm. The method of claim 65, And wherein said non-reactive gas is in the range of 10 to 350 sccm, and said oxygen-containing gas is in the range of 0.02 to 0.15 sccm. The method of claim 65, 10. A method of fabricating a magnetic junction memory device, characterized in that an oxygen-containing gas is injected into the process from sputtering a solid source of oxygen-containing solids. The method of claim 65, And said solid source comprises alumina or quartz. The method of claim 65, Wherein the oxygen-containing gas is injected from leak control from the atmosphere. The method of claim 65, And producing a bottom metal layer under said insulating layer. The method of claim 65, Wherein the plasma is generated with a non-reactive gas. The method of claim 65, And wherein said insulating layer comprises aluminum oxide, magnesium oxide, or other insulating oxide. The method of claim 65, Wherein the upper metal layer comprises a magnetic layer, part of an MRAM stack structure, or one or more layers of NiFe, CoFe, CoNiFe, and CoFeB.

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