Background technology
(Phase Change Random Access Memory, PCRAM) technology is based on S.R.Ovshinsky and proposes in late 1960s that conception that phase-change thin film can be applied to the phase change memory medium sets up phase transition storage.As a kind of emerging nonvolatile storage technologies, phase transition storage all has bigger superiority in all many-sides such as read or write speed, read-write number of times, data hold time, cellar area, many-valued realizations to flash memory, has become the focus of present non-volatile memory technology research.
In phase transition storage, can change the value of memory by the phase change layer that has recorded data is heat-treated.The phase-change material that constitutes phase change layer can enter crystalline state or noncrystalline state owing to the thermal effect that adds of applying electric current.When phase change layer was in crystalline state, the resistance of PCRAM was lower, and this moment, the memory assignment was " 0 ".When phase change layer was in noncrystalline state, the resistance of PCRAM was higher, and this moment, the memory assignment was " 1 ".Therefore, PCRAM is the nonvolatile memory that the resistance difference of utilization when phase change layer is in crystalline state or noncrystalline state write/read data.
The phase transition storage of prior art generally includes the phase change layer between bottom electrode, top electrodes and bottom electrode and the top electrodes.Wherein the crystalline state transition process of phase change layer needs higher temperature, generally by bottom electrode phase change layer is heated, and top electrodes only plays the interconnection effect.Bottom electrode will directly influence the read-write speed of phase transition storage to the heating effect quality of phase change layer.In being the Chinese patent application of CN101271918, publication number discloses a kind of phase transition storage.
In the prior art by dwindling the contact area of bottom electrode and phase change layer, improve contact resistance, thereby obtain the good thermal effect that adds, with reference to figure 1 with reference to figure 2, show end view and the vertical view of prior art bottom electrode one embodiment respectively, described bottom electrode comprises: the conductive plunger 11 that is positioned at first insulating barrier 15, annular electrode 12 in second insulating barrier 14, described second insulating barrier 14 is positioned on first insulating barrier 15, described annular electrode 12 is positioned on the conductive plunger 11, also comprise the 3rd insulating barrier 13 that is filled in the annular electrode 12, in the phase transition storage application process, the phase change layer (not shown) that is positioned at the bottom electrode top by 12 pairs of annular electrodes heats, because the sidewall of annular electrode 12 is thinner, so less with the contact area of phase change layer, thus contact resistance improved, and then can obtain the good thermal effect that adds.
The manufacture method of phase transition storage bottom electrode comprises in the prior art: at first comprising first insulating barrier, 15 depositions, second insulating barrier 14 of conductive plunger; Described second insulating barrier 14 of etching again, the groove 16 (as shown in Figure 3) of conductive plunger is exposed in formation, deposit metallic material and the described metal materials of etching in the groove 16 then form 17 (as shown in Figure 4) of annular electrode hole, at last deposition of insulative material in the annular electrode hole 17.In said method, described second insulating barrier 14 of etching is when forming the groove 16 that is positioned on the conductive plunger, because the groove aperture is less and the degree of depth is bigger, so be difficult to form more straight recess sidewall; In addition, when deposition of insulative material in the annular electrode hole, because the depth-to-width ratio in annular electrode hole is bigger, when deposition of insulative material, insulating material is difficult to be filled in the annular electrode hole.
Summary of the invention
The problem that the present invention solves provides a kind of manufacture method of phase transition storage annular electrode, reduces manufacture difficulty, improves reliability.
The invention provides a kind of manufacture method of phase transition storage bottom electrode, comprising:
The conductive plunger that forms first insulating barrier and be arranged in first insulating barrier at substrate;
The frustum mask body that forms the cylindrical metal electrode and be located thereon at conductive plunger;
Form second insulating barrier on first insulating barrier, metal electrode and mask body surface, and make described second insulating layer exposing go out the top table top of frustum mask body;
Be mask etching frustum mask body and part cylindrical metal electrode successively with second insulating barrier, form Baltimore groove; Wherein remaining metal electrode is spill after the etching, as bottom electrode;
Fill insulant in the described Baltimore groove forms the 3rd insulating barrier;
Expose described bottom electrode.
Describedly form the cylindrical metal electrode and the step of the frustum mask body that is located thereon comprises at conductive plunger: form metal level and mask layer at first insulating barrier successively; Adopt the described mask layer of photoetching process etching, form the frustum mask body of bottom alignment conductive plunger; Be the described metal level of mask etching with described frustum mask body again, form the cylindrical metal electrode.
Preferably, described frustum mask body is circular cone shape.The sidewall inclination angle scope of the described frustum of a cone is 3 °~8 °.Described cylindrical metal electrode covers conductive plunger at least.Described metal level material comprises tungsten or aluminium.Described mask layer material comprises the silicon nitride that silicon nitride, silicon oxynitride and carbon containing mix.The material of described second insulating barrier comprises silica, fluorine silex glass, and described silica forms by deposition tetraethoxysilane and thermal decomposition.
The described frustum mask body of etching successively and part cylindrical metal electrode comprise:
Be mask with second insulating barrier, adopt the described frustum mask body of plasma etching industrial etching that the frustum mask body is had big selective etching ratio, until exposing the cylindrical metal electrode;
Be mask with second insulating barrier and remaining frustum mask body, adopt the cylindrical metal electrode that the column metal electrode is had the described part of plasma etching industrial etching of big selective etching ratio.
Preferably, in the described concave bottom electrode, its ring wall wall thickness is less than bottom thickness, and described ring wall wall thickness equals the top table top of the preceding frustum mask body of etching and the radius difference of bottom table top.The depth-to-width ratio scope of described Baltimore groove is 1: 1~3: 1.Described the 3rd insulating barrier is filled the concave portions of completely described bottom electrode at least.The described bottom electrode that exposes comprises: use cmp attenuate the 3rd insulating barrier and second insulating barrier, until exposing described bottom electrode.
Compared with prior art, the present invention has the following advantages: by adjusting the inclination angle of frustum mask body, and be mask with second insulating barrier, can accurately control the openings of sizes that etching forms groove, be easy to adjust depth-to-width ratio and the ring wall thickness in annular electrode hole in the metal electrode of final formation.Method is simple and improved the reliability of device.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, below in conjunction with accompanying drawing the specific embodiment of the present invention is described in detail.
Set forth a lot of details in the following description so that fully understand the present invention, implement but the present invention can also adopt other to be different from alternate manner described here, so the present invention has not been subjected to the restriction of following public specific embodiment.
Just as described in the background section, in the manufacture method of prior art phase transition storage annular electrode, need deposition second insulating barrier earlier, described second insulating barrier of etching forms the groove that exposes conductive plunger again, afterwards in the groove deposit metallic material and the described metal material of etching to form annular electrode, because the groove aperture is less and the degree of depth is bigger, thus be difficult to form more straight recess sidewall, thus increased manufacture difficulty.
At the problems referred to above, the invention provides a kind of manufacture method of phase transition storage annular electrode, show the schematic flow sheet of phase transition storage annular electrode manufacture method one execution mode of the present invention with reference to figure 5.Described manufacture method may further comprise the steps:
S1, the conductive plunger that forms first insulating barrier and be arranged in first insulating barrier at substrate; Described first insulating barrier can be interlayer dielectric layer or intermetallic dielectric layer etc., and described conductive plunger can be the contact hole that is filled with interconnecting metal, groove etc., also can be the metal interconnect structure of other conductions.
S2, the frustum mask body that forms the cylindrical metal electrode and be located thereon at conductive plunger; Described cylindrical metal electrode can be cylindrical, square column type or polygon cylinder, but with its on the bottom table top of frustum mask body be consistent.The sidewall with inclination angle of described frustum mask body can utilize anisotropic plasma etching to form.Preferably, described frustum mask body is circular cone shape.
S3, form second insulating barrier at first insulating barrier, metal electrode and mask body surface, and make described second insulating layer exposing go out the top table top of taper mask body;
Preferably, can be earlier in the surface coverage deposition insulation material of first insulating barrier, cylindrical metal electrode and frustum mask body, carry out planarization then and expose the frustum mask body and get final product.
S4, be mask etching frustum mask body and part cylindrical metal electrode successively with second insulating barrier, form Baltimore groove; Because the top footprint of frustum mask body is greater than the bottom table top, if be mask etching frustum mask body with second insulating barrier therefore, with the Baltimore groove that to form with its top mesa shape be opening shape, when further being etched to the cylindrical metal electrode along above-mentioned Baltimore groove, will form the metal ring wall at the cylindrical metal electrode.In order to guarantee that metal electrode is good with contacting of bottom conductive connector, usually need be at the bottom of described Baltimore groove reserve part metal electrode.Like this, remaining metal electrode is spill after the etching, namely can be used as bottom electrode.
S5, in the described Baltimore groove fill insulant, form the 3rd insulating barrier; Described the 3rd insulating barrier can overflow in Baltimore groove and be overlying on second surface of insulating layer, also can the filling part Baltimore groove, but need fill the concave portions of full bottom electrode at least.
S6, expose described bottom electrode by planarization.Preferably, described planarization can adopt cmp.
Further describe each step of the inventive method below in conjunction with a specific embodiment.
To Figure 14, show the generalized section of phase transition storage annular electrode one embodiment of phase transition storage annular electrode manufacture method formation of the present invention with reference to figure 6.
With reference to figure 6, the conductive plunger 102 that forms first insulating barrier 101 and be arranged in first insulating barrier 101 at the substrate (not shown).Concrete, the material of described first insulating barrier 101 can be conventional interlayer dielectric layer or inter-metal medium layer material such as silica or silicon nitride, described conductive plunger 102 is for being filled with contact hole or groove and other metal interconnect structures of interconnecting metals such as copper, tungsten, aluminium, described substrate also comprises the semiconductor device such as gate tube with described conductive plunger 102 electric connections, this step is same as the prior art, repeats no more.
With reference to figure 7, form metal level 103 and mask layer 104 successively on the surface of described first insulating barrier 101, described metal level is easy to etching, is used to form metal electrode, and material can be tungsten, aluminium etc., can adopt physical vapour deposition (PVD) to form.Described mask layer 104 is used for as the used hard mask of subsequent etching metal level 103, and material can be the silicon nitride of silicon nitride, silicon oxynitride or carbon containing, can adopt chemical vapour deposition (CVD) to form.
With reference to figure 8, at the surperficial spin coating photoresist of described mask layer 104, and it is carried out exposure imaging, form patterned photoresist 105.Described photoresist 105 is aimed at the conductive plunger 102 of bottom, is generally the metal electrode that guarantees follow-up formation and covers conductive plunger 102 at least, and described photoresist 105 also can cover described conductive plunger 102 positions.
With reference to figure 9, adopt the described mask layer 104 of plasma etching industrial etching, until exposing metal level 103, form frustum mask body 106, photoresist 105 is removed in ashing again.
Can utilize the pattern of photoresist 105 to adjust top mesa shape and the size of described frustum mask body 106, for example square, polygon etc.Can utilize the anisotropic properties of plasma etching to make the frustum mask body 106 of etching formation have angled side walls.Because more sharp-pointed surface portion etching very fast always in the plasma etching process, so the frustum mask body after the etching, its bottom table top always trends towards circular.As preferred version, the mask body of frustum described in the present embodiment 106 is the frustum of a cone, and the shape of top table top and bottom table top is circle.
Concrete, can in plasma etching industrial, regulate the flow-rate ratio of different etching gas, thereby the speed of control lateral etching and vertical etching, the speed ratio of described lateral etching and vertical etching has determined the sidewall draft angles α (angle of sidewall and vertical direction) of frustum mask body 106.The scope of common described inclined angle alpha is 3 °~8 °, and the height h of described frustum mask body 106 equals the thickness of the mask layer 104 of previous deposition.In the final frustum mask body 106 that forms, the height h that the semidiameter Δ d of top table top and bottom table top namely equals frustum mask body 106 multiply by described inclination angle cotangent value ctg α.
With reference to Figure 10, be mask with described frustum mask body 106, the described metal level 103 of etching until exposing first insulating barrier 101, forms cylindrical metal electrode 107.The height H of described cylindrical metal electrode 107 equals the thickness of the metal level 103 of previous deposition, and the cross sectional shape size is identical with the bottom table top of frustum mask body 106, also is the diameter that the diameter D of cylindrical metal electrode 107 equals the bottom table top of frustum mask body 106.
With reference to Figure 11, surface coverage at first insulating barrier 101, cylindrical metal electrode 107 and frustum mask body 106 deposits second insulating barrier 108, and make that the surface of described second insulating barrier 108 is concordant with the top of frustum mask body 106, thereby expose its top table top.
Concrete, can be earlier at the surface coverage deposition dielectric of semiconductor structure shown in Figure 10, and then carry out chemico-mechanical polishing above-mentioned dielectric carried out attenuate, until the top table top that exposes frustum mask body 106, form second insulating barrier 108.The material of described second insulating barrier 108 should be different with frustum mask body 106, so that carry out follow-up selective etch, in the present embodiment, the material of described second insulating barrier 108 can adopt low k dielectrics such as silica, fluorine silex glass, can carry out above-mentioned covering depositing operation by chemical vapour deposition (CVD).In addition, when described second insulating barrier 108 is selected silica for use, can also pass through deposition tetraethoxysilane (TEOS), and carry out thermal decomposition formation, to obtain good adhesiveness.
With reference to Figure 12, be mask with second insulating barrier 108, adopt plasma etching industrial step by step etching frustum mask body 106 and part cylindrical metal electrode 107 successively, form Baltimore groove 200.Metal electrode after the etching is spill, as bottom electrode.
Concrete, be mask with second insulating barrier 108 at first, adopt the described frustum mask body 106 of plasma etching industrial etching that frustum mask body 106 is had big selective etching ratio, until exposing cylindrical metal electrode 107; And then be mask with second insulating barrier 108 and remaining frustum mask body 106, adopt the cylindrical metal electrode 107 that column metal electrode 107 is had the plasma etching industrial etched portions thickness of big selective etching ratio, finally form Baltimore groove 200.Wherein, in order to make the inwall of Baltimore groove 200 vertical, need to adjust the flow-rate ratio of different etching gas to avoid the influence of lateral etching.
In above-mentioned etching process, the opening shape of described Baltimore groove 200 is the top mesa shape of former frustum mask body 106, its groove footpath d is less than the diameter of the bottom table top of former frustum mask body 106, also be the diameter D of cylindrical metal electrode 107, the diameter D difference of above-mentioned groove footpath d and cylindrical metal electrode 107 is 2 Δ d.Therefore when further being etched to metal electrode 107 along described Baltimore groove 200, the part that former cylindrical metal electrode 107 is etched will form metal ring wall 107a, and wall thickness equals above-mentioned diameter difference half, also is the semidiameter Δ d of top table top and bottom table top in the former frustum mask body 106.
For the contact that guarantees bottom electrode and bottom conductive connector 102 is good, the bottom of described Baltimore groove 200 should reserve part metal electrode thickness, makes formed bottom electrode be spill.As preferred version, the bottom thickness k of described concave bottom electrode also is the top table top of etching inner cone platform shape mask body and the radius difference DELTA d of bottom table top greater than the wall thickness of described metal ring wall 107a.The depth-to-width ratio of Baltimore groove 200 is (H+h-k)/d, and described depth-to-width ratio will influence follow-up complexity when filling dielectric in Baltimore groove 200, and comparatively desirable depth-to-width ratio scope is 1: 1~3: 1.
In sum, when carrying out the setting of above steps technological parameter, determine the physical dimension of the final products such as groove footpath d, depth-to-width ratio of the wall thickness Δ d of ring wall in the bottom electrode and Baltimore groove 200 at first as required; And then according to each geometrical relationship formula, select the physical dimension of corresponding intermediate structure, sidewall inclination angle of the deposit thickness of metal level 103, mask layer 104, frustum mask body 106 etc. for example; The last technological parameter of determining again in each step formation technology.As technology contents known in those skilled in the art, repeat no more.
With reference to Figure 13, in described Baltimore groove 200, fill dielectric, form the 3rd insulating barrier 109.Wherein, Baltimore groove 200 can be filled and overflow to described dielectric, and the 3rd insulating barrier 109 that make to form is overlying on the surface of second insulating barrier 108, also filling part Baltimore groove 200 only, but fill the concave portions of full bottom electrode at least.Concrete, described dielectric can be silica or silicon nitride, adopts chemical vapor deposition method to fill.
With reference to Figure 14, utilize planarization to expose bottom electrode.Concrete, can adopt chemico-mechanical polishing, described the 3rd insulating barrier 109 of attenuate and second insulating barrier 108 are removed remaining frustum mask body 106 simultaneously, until the bottom electrode that exposes spill, also namely expose metal ring wall 107a.。
In the manufacturing process of follow-up phase transition storage, described metal ring wall 107a will contact with the phase-change material of the side of being located thereon, because the wall thickness of metal ring wall 107a is less, thereby reduced the contact area of bottom electrode and phase-change material, improve contact resistance, and then can obtain the good thermal effect that adds.
Compare with the side wall that is positioned at second insulating barrier top in the prior art, in the manufacture method of the present invention, utilize second insulating barrier as mask, etching frustum mask body and column bottom electrode can accurately be controlled the openings of sizes that etching forms Baltimore groove successively.In addition, when being etched to the cylindrical metal electrode along described Baltimore groove, etching depth is as long as satisfy the remaining metal electrode thickness in bottom greater than the wall thickness of the metal ring wall that forms.Depth-to-width ratio that can the flexible Baltimore groove has reduced technology difficulty.
A nearlyer step ground, prior art is by etching second insulating barrier, the groove of conductive plunger is exposed in formation, because second insulating layer material is opaque, so position that the groove that forms might depart from conductive plunger, in the groove during deposit metallic material, metal material can't be connected with conductive plunger again, and it is bad to cause bottom electrode to be made.And in the technical scheme of the present invention, because the cylindrical metal electrode is covered in conductive plunger at least, and the part metals thickness of electrode that has kept the Baltimore groove bottom when aforementioned etching makes to have than large contact surface between the final bottom electrode that forms and the conductive plunger and amasss, thereby improved reliability.
Though it is pointed out that the present invention is example with the bottom electrode of phase transition storage, the manufacture method of described phase transition storage bottom electrode is equally applicable in the manufacture craft of other and the similar device of phase transition storage bottom electrode.Those skilled in the art of the present invention should apply based on technical scheme disclosed in this invention easily.
Though the present invention discloses as above with preferred embodiment, the present invention is defined in this.Any those skilled in the art without departing from the spirit and scope of the present invention, all can do various changes and modification, so protection scope of the present invention should be as the criterion with claim institute restricted portion.