Patent ID: 12232309

DETAILED DESCRIPTION

FIG.1illustrates a cross-sectional view of forming a capacitor according to some embodiments of the present disclosure.

First, a substrate100is provided. InFIG.1, the substrate100includes a base102, a cap layer104, and a dielectric layer106.

In some embodiments, the base102includes an isolation structure102adisposed therein to define an active region. A word line (not shown) is further embedded in the base102. In some embodiments, the word line serves as a gate, which includes a gate dielectric layer, a gate liner, and a gate electrode (not shown).

In some embodiments, the cap layer is disposed on the base102. The cap layer104may include silicon oxide (such as thermal silicon oxide, tetraethylorthosilicate (TEOS) oxide), silicon nitride (SiN), silicon oxynitride (SiON), or a combination thereof.

In some embodiments, the dielectric layer106is disposed on the cap layer104. The dielectric layer106may include silicon nitride, silicon oxynitride, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), spin-on glass (SOG), undoped silicate glass (USG), tetraethylorthosilicate (TEOS) oxide, low-k dielectric materials, and/or other suitable dielectric materials, and the like.

In some embodiments, the substrate100further includes a bit line120and a capacitor contact130disposed in the dielectric layer106. The bit line120includes conductive layers122and124and a dielectric layer126. The conductive layers122and124may include conductive materials, which include doped polysilicon, metal, or metal nitride, such as tungsten (W), titanium (Ti), titanium nitride (TiN), and the like. The dielectric layer126may include a dielectric material, which includes nitride or oxide, such as silicon nitride or silicon oxide.

In some embodiments, the capacitor contact130includes a conductive layer132, a silicide layer134, and a conductive layer136. The material of the conductive layer132is similar to that of the conductive layers122and124. The silicide layer134may include a metal silicide layer, such as cobalt silicide.

As shown inFIG.1, a support layer200and a template layer300are formed on the substrate100sequentially. In the embodiment ofFIG.1, the support layer200and the template layer300are alternately arranged up and down. Specifically, the lower support layer210, the lower template layer310, the middle support layer220, the upper template layer320, and the upper support layer230are sequentially formed. In some embodiments, the support layer200is used to connect the cup-shaped lower electrode to be formed later.

In some embodiments, the lower support layer210includes a contact pad210afor subsequent electrical connection between the capacitor contact130and the cup-shaped lower electrode (not shown). The contact pad210aincludes a conductive material, which is similar to the conductive layer136described above, and will not be repeated here.

In some embodiments, the support layer200and the template layer300includes materials with etching selectivity. The materials of the support layer200may be nitride, such as silicon nitride, silicon oxynitride, silicon carbon oxynitride, silicon carbide, or a combination thereof. In some embodiments, the materials of the template layer300may be an oxide, such as silicon oxide, borophosphosilicate glass, or a combination thereof.

As shown inFIG.2, a mask400is formed on the upper support layer230. Also referring toFIG.3, the mask400is patterned to form an array of openings to expose the upper support layer230below. The mask400will be used to define cup-shaped openings (not shown) that forms cup-shaped bottom electrodes in the following.

In some embodiments, the mask400may be a photoresist layer. The mask400may be a hard protective layer, which includes oxide, oxynitride, or other suitable dielectric materials.

Next, as shown inFIG.4, cup-shaped openings O are formed in the template layer300and the support layer200. The cup-shaped openings O penetrate the upper support layer230′, the upper template layer320′, the middle support layer220′, and the lower template layer310′ and expose the contact pad210ain the lower support layer210′. The cup-shaped openings O do not penetrate the lower support layer210′.

Also referring toFIG.5, the cup-shaped openings O may be arranged in an array. In the embodiment ofFIG.5, in the radial direction extending from the center of the cup-shaped openings O, the contact pad210a, the lower support layer210′ and the mask400are sequentially arranged.

In some embodiments, the aspect ratio of the cup-shaped openings O is greater than 10 and less than 100. Within the above range, the contact area between the subsequent lower electrode and the capacitor dielectric layer may be increased without shifting or tipping of the cup-shaped lower electrode formed subsequently.

In some embodiments, the formation of the cup-shaped openings O includes using the mask400as an etching mask, and etching the support layer200and the template layer300that are not covered by the mask400by an etching process. Next, as shown inFIG.6, the mask400is removed.

Also referring toFIG.7, in the radial direction extending from the center of the cup-shaped openings O, the contact pad210a, the lower support layer210′ and the upper support layer230′ are sequentially arranged.

Next, as shown inFIG.8, a lower electrode material layer500is conformally formed along the sidewall and the top surface of the support layer200. Specifically, the lower electrode material layer500is conformally formed on the top surface of the lower support layer210′ (including the contact pad210a), on the sidewall surfaces of the lower template layer310′, the middle support layer220′, the template layer320′, the sidewall surfaces and the top surface of the upper support layer230′.

Also referring toFIG.9, the lower electrode material layer500covers the surface of the cup-shaped openings O, so the cup-shaped openings O under the bottom electrode material layer500is represented by dashed lines.

In some embodiments, the materials of the lower electrode material layer500may include metal, metal nitride, or metal silicide, such as titanium nitride, tantalum nitride, tungsten, titanium tungsten, aluminum, copper, titanium, and the like.

Next, as shown inFIG.10, the lower electrode material layer500on the top surface of the support layer200is removed, and the remaining lower electrode material layer serves as cup-shaped lower electrodes500′. Also, removing the lower electrode material layer500also removes an upper portion of the support layer200, so that the sidewalls of any two adjacent cup-shaped lower electrodes500′ protrude from the top surface of the support layer200.

In some embodiments, the removal of the lower electrode material layer500and the removal of the upper portion of the support layer200are performed at the same time by dry etching. The dry etching has a selective etching ratio (etching rate ratio) of the cup-shaped lower electrode material layer500to the support layer200of about 10:1-30:1. Within the above etching selective ratio, the top surface of the lower electrode material layer may be cut off.

In some embodiments, removing the upper portion of the support layer200includes removing the upper portion of the upper support layer230′ to reduce the height of the upper support layer230′, so that the subsequently formed annealed oxide layer may remain in the outer surface of the cup-shaped lower electrodes to facilitate maintaining the height of the cup-shaped lower electrodes. Here, the upper support layer230′ whose height has been reduced is denoted as230″.

In some embodiments, the lower support layer210′ extends continuously at the bottoms of each cup-shaped lower electrode500′. The middle support layer220′ connects the middle portion of the outer surfaces of each cup-shaped lower electrode500′. The upper support layer230″ is connected to the upper portion of the outer surfaces of each of the cup-shaped lower electrodes500′.

Also referring toFIG.11, each of the cup-shaped openings O is surrounded by one cup-shaped lower electrode500′. Each of the cup-shaped lower electrodes is surrounded by the upper support layer230″. It should be noted that the lower electrode material layer500(or the cup-shaped lower electrode500′) still covers the surfaces of the cup-shaped openings O, so the cup-shaped openings O under the bottom electrode material layer500is still represented by dashed lines.

Next, as shown inFIG.12, an oxide layer is formed on the surfaces of each of the cup-shaped lower electrodes500′ and on the surface of the support layer200. The oxide layer includes metal oxide, such as aluminum oxide. Next, the oxide layer is annealed to form an annealed oxide layer600.

In some embodiments, the annealed oxide layer600is formed on the inner and outer surfaces of the cup-shaped lower electrodes500′ by an annealing process, which may reduce the work function and inhibit the leakage current of the high-k dielectric. In some embodiments, the annealed oxide layer600may further protect the cup-shaped lower electrodes500′ from being affected by subsequent process, thereby avoiding reducing the height of the cup-shaped lower electrodes500′.

In some embodiments, the cup-shaped lower electrodes500′ include metal, such as titanium and titanium nitride. In some embodiments, the annealing process may make the annealed oxide layer600contain the same metal element or/and oxide of the same metal as the cup-shaped lower electrode500′ to increase the resistance and improve the capacitance. The annealed oxide layer600includes TiAl, TiAIO, TiOx, Al2O3, and the like.

Also referring toFIG.13, the annealed oxide layer600covers the surfaces of the cup-shaped openings, so the cup-shaped openings O under the annealed oxide layer600are represented by dashed lines.

Next, as shown inFIG.14, a protective layer700is formed on the annealed oxide layer600, wherein the protective layer700covers the tops of the cup-shaped openings O. Next, a mask800is formed on the top surface of a portion of the cup-shaped lower electrodes500′.

In some embodiments, the protective layer700is formed to provide a flat surface to facilitate subsequent pattern definition. In some embodiments, the protective layer700includes a first protective layer710and a second protective layer720. In other embodiments, the protective layer700may include only one protective layer.

In the embodiment ofFIG.14, since the aspect ratio of the cup-shaped openings O is quite large, the step coverage of the first protective layer710is poor. Thus, the upper sidewall of the cup-shaped opening O is covered by the first protective layer710, and the top of the cup-shaped opening O is closed by an overhang710aof the first protective layer710. Thus, the cup-shaped openings O are not filled completely.

In some embodiments, the first protective layer710and the second protective layer720may include oxygen-containing materials or carbon-containing materials, such as silicon oxide or carbon or the like.

Next, still referring toFIG.14, after forming the second protective layer720, an anti-reflection layer730may be further formed on the second protective layer720to prevent the reflection of the underlying film during exposure, which helps to improve the pattern transfer.

Next, still referring toFIG.14, the mask800is formed on the top surface of a portion of the cup-shaped lower electrodes500′. Also referring toFIG.15, the mask800covers a portion of each of the cup-shaped openings O (corresponding to the cup-shaped lower electrode) and exposes the other portion of each of the cup-shaped openings O (corresponding to the cup-shaped lower electrode). In some embodiments, each region, which is not covered by the mask800, includes openings O to facilitate subsequent removal of the template layer300.

Next, as shown inFIG.16, the protective layer700and the support layer200, which are not covered by the mask800will be removed, and the mask800is subsequently removed. Specifically, the second protective layer720, the first protective layer710, the upper support layer230″, the upper template layer320′, and the middle support layer220′, which are not covered by the mask800are removed. In some embodiments, the removal of the protective layer700and the support layer200further includes removing a portion of the annealed oxide layer600and a portion of the cup-shaped lower electrodes500′. In detail, the removal of the portion of the annealed oxide layer600includes removing the annealed oxide layer600which is not covered by the mask800and is located on the outer surfaces of the cup-shaped lower electrodes500′. The removal of the portion of the cup-shaped lower electrode500′ includes thinning the upper portion of the cup-shaped lower electrode500′ which is not covered by the mask800. Since the cup-shaped openings O have a relatively large aspect ratio, even if the annealed oxide layer600not covered by the mask800is removed, a portion of the annealing oxide layer600will remain on the inner surface of the cup-shaped lower electrode500′. Here, the remaining annealed oxide layer600is denoted as600′, and the remaining cup-shaped lower electrodes500′ are denoted as500″.

In some embodiments, the removal of the protective layer700and the support layer200, which are not covered by the mask800, may include dry etching using halogenated hydrocarbon etchant (such as CF4, CHF3, CH2F2, or the like). The ratio of halogenated hydrocarbon carbon, fluorine, and hydrogen may improve the etching selectivity of the etchant to the cup-shaped lower electrode500′. Therefore, the protective layer700and the support layer200may be removed while reducing damage to the cup-shaped lower electrodes500′.

Compared with the case where the top surface of the lower electrode material layer is continuously removed after the mask is formed, the embodiment of the present disclosure removes the top surface of the lower electrode material layer500before the mask800is formed. Thus, the distance between the top surface of the cup-shaped lower electrode500″ and the upper support layer230″ is increased, thereby increasing the contact area between the subsequent capacitor dielectric layer900and the cup-shaped lower electrode500″. In addition, the embodiment of the present disclosure further forms an annealed oxide layer600after removing the top surface of the lower electrode material layer500, which may protect the cup-shaped lower electrode500″ from damage during the subsequent process.

In addition, compared to the removal of the upper support layer and the middle support layer that are not covered by the mask in two steps, the embodiment of the present disclosure uses one step to remove the upper support layer230″ and the middle support layer220′ to reduce one cleaning process, thereby achieving the simplification of the process and reducing the damage of the cup-shaped lower electrodes500′ during the process.

Also referring toFIG.17, the cup-shaped lower electrode500″ and the annealed oxide layer600′ covered by the second protective layer720′ are represented by dashed lines. It can be seen fromFIG.17that the cup-shaped lower electrodes500″ and the annealed oxide layer600′, which surround the cup-shaped opening O, are both partially covered by the second protective layer720′ and are partially exposed. In addition, the annealed oxide layer600′ covered by the second protective layer720′ is located inside and outside the cup-shaped lower electrodes500″, while the annealed oxide layer600′ not covered by the second protective layer720′ is located only inside the cup-shaped lower electrodes500″.

Next, as shown inFIG.18, the remaining protective layer700, the template layer300, and a portion of the annealed oxide layer600′ are removed, so that the remaining annealed oxide layer600″ is attached to the inside surface of the cup-shaped lower electrodes500″. Specifically, the remaining second protective layer720′, the first protective layer710′, the upper template layer320, the lower template layer310, and a portion of the annealed oxide layer600′ are removed. This removal step further includes removing a portion of the upper support layer230″ so that the remaining upper support layer230″ does not contact the annealed oxide layer600″. Here, the remaining upper support layer230″ is denoted as230′″.

In some embodiments, this removal step reduces most of the thickness of the annealed oxide layer600′ and leaves only a thin film on the surfaces of the cup-shaped lower electrodes500″. The thin film includes high-k TiOxdangling bonds formed by the annealing process performed on the surfaces of the cup-shaped lower electrodes500″.

In some embodiments, an annealed oxide layer600″ is located on the inner surface of each of the cup-shaped lower electrodes500″. The annealed oxide layer600″ further extends to the top surface and a portion of the outer surface of the cup-shaped lower electrodes500″ with the upper support layer230′″ on the outer surface, but does not contact the upper support layer230″.

In some embodiments, the ratio of the distance D from the top surface of the cup-shaped lower electrodes500″ to the top surface of the upper support layer230′″ and the thickness TN of the upper support layer230′″ is 0.8 or more. Within the above ratio, the coverage area of the capacitor dielectric layer is increased, thereby improving the capacitance value. In some embodiments, the ratio of the distance D to the thickness TN may be about 1, for example.

In some embodiments, the sidewalls of the cup-shaped lower electrodes500″ with the upper support layer230″ on the outer surface are higher than the sidewalls of the cup-shaped lower electrode500″ without the upper support layer230″ on the outer surface.

In some embodiments, since the inner surface of the cup-shaped lower electrode500″ is protected by the annealed oxide layer600″, the inner surface of the sidewall of the cup-shaped lower electrode500″ is substantially unaffected by etching. The annealed oxide layer600′ shrinks into a cone shape on the upper portion due to etching. On the other hand, since a portion of the outer surfaces of the sidewalls of the cup-shaped lower electrodes500″ is affected by etching, the width at the upper portion thereof is also reduced. Specifically, the width of the upper portion of the sidewalls of the cup-shaped lower electrodes500″ that do not have the upper support layer230′″ on the outer surface is smaller than the width of the lower portion (WU<WL). In contrast, the upper portion of the sidewalls of the cup-shaped lower electrode500″ with the upper support layer230″ on the outer surface have substantially the same width as the lower portion (WU=WL). It should be noted that the term “substantially the same” may include the same or a variation within 10%.

In some embodiments, the ratio of the average width of the annealed oxide layer600″ to the average width of the cup-shaped lower electrode500″ is greater than 0 and equal to or less than 1.7. In this way, the capacitance value may be further increased while reducing the leakage current. The average width of the annealed oxide layer600″ is approximately 2.5 Å-20 Å.

In some embodiments, the support layer200is located between the outer surfaces of the cup-shaped lower electrodes500″ to connect the cup-shaped lower electrodes. The upper support layer230′″, the middle support layer220′, and the lower support layer210′ are respectively connected to the upper, middle, and lower portions of the outer surfaces of the cup-shaped lower electrodes to strengthen the mechanical strength of the capacitor, thereby avoiding phenomenon of capacitor deformation or even tipping.

Also referring toFIGS.19and20,FIG.19also shows the relative positions of the cup-shaped bottom electrodes500″ and the annealed oxide layer600″ in the top view, whileFIG.20only shows the relative position of the cup-shaped lower electrodes500″ in the top view. In detail, inFIG.20, each of the cup-shaped opening O is surrounded by one cup-shaped lower electrode500″. In addition, the position covered by the mask800(refer toFIG.15) will expose the upper support layer230″ in the top view at this stage, while the position not covered by the mask800(refer toFIG.15) will expose the lower support layer210′ in the top view at this stage.

Correspondingly referring toFIG.19, the annealed oxide layer600″ at the position not covered by the mask800(referring toFIG.15) is only located inside each of the cup-shaped lower electrodes500″, while the annealing oxide layer600″ at the position covered by the mask800(referring toFIG.15) is located inside, outside, and above each of the cup-shaped lower electrode500″. That is, inFIG.19, the annealed oxide layer600″ completely covers the inner side of each of the cup-shaped lower electrodes500″ but only partially covers the upper and outer sides of each of the cup-shaped lower electrodes500″.

Next, as shown inFIG.21, a capacitor dielectric layer900is formed on the surfaces of the cup-shaped lower electrodes500″, on the surface of the remaining annealed oxide layer600″, and on the surface of the support layer200.

In some embodiments, the capacitor dielectric layer900conformally covers the inner and outer surfaces of the cup-shaped lower electrodes500″. The annealed oxide layer600″ is sandwiched between the capacitor dielectric layer900and the inner surface of the cup-shaped lower electrode500″ and is sandwiched between the capacitor dielectric layer900and a portion of the outer surface of the cup-shaped lower electrode500″, thereby inhibiting the generation of leakage current. The annealed oxide layer600″ is further sandwiched between the capacitor dielectric layer900and a portion of the top surface of the cup-shaped lower electrode500″.

In some embodiments, the capacitor dielectric layer900may include high-k dielectric materials, such as hafnium oxide (HfO), zirconium oxide (ZrO), aluminum oxide (AIO), aluminum nitride (AlN), Titanium oxide (TiO), lanthanum oxide (LaO), yttrium oxide (YO), gamma oxide (GdO), tantalum oxide (TaO), or a combination thereof.

Next, as shown inFIG.21, an upper electrode1000is formed on the surface of the capacitor dielectric layer900. In some embodiments, the upper electrode1000covers the surface of the capacitor dielectric layer900.

In some embodiments, the upper electrode1000may include metal, metal silicide, metal nitride or metal alloy, such as titanium nitride (TiN), tantalum nitride (TaN), tungsten (W), titanium tungsten (TiW), aluminum (Al), copper (Cu), or the like.

In summary, the embodiment of the present disclosure may protect the lower electrode from being affected by the process by forming an annealed oxide layer. By the annealing oxide layer sandwiched between a portion of the surface of the lower electrode and the capacitor dielectric layer, the work function may be reduced and leakage current may be inhibited. Forming the cup-shaped lower electrodes and the annealed oxide layer before the protective layer is formed may reduce the risk of greatly reducing the height of the cup-shaped lower electrodes when the template layer is removed. When removing the template layer, the upper support layer and the middle support layer may be removed together in the same step, which may reduce the complexity of the process. The strengthening structure formed by the lower support layer, the middle support layer, and the upper support layer increases the mechanical strength of the capacitor to avoid the phenomenon of deformation or even tipping of the capacitor. As above, the embodiment of the present disclosure may increase the capacitance value.

Although the present invention is disclosed in the foregoing embodiments, it is not intended to limit the present invention. Those with ordinary skill in the technical field to which the present invention pertains can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to those defined by the scope of the appended claims.