US20030047532A1 - Method of etching ferroelectric layers - Google Patents
Method of etching ferroelectric layers Download PDFInfo
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- US20030047532A1 US20030047532A1 US10/210,550 US21055002A US2003047532A1 US 20030047532 A1 US20030047532 A1 US 20030047532A1 US 21055002 A US21055002 A US 21055002A US 2003047532 A1 US2003047532 A1 US 2003047532A1
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- 238000000034 method Methods 0.000 title claims abstract description 66
- 238000005530 etching Methods 0.000 title claims abstract description 60
- 239000007789 gas Substances 0.000 claims abstract description 95
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 25
- FAQYAMRNWDIXMY-UHFFFAOYSA-N trichloroborane Chemical compound ClB(Cl)Cl FAQYAMRNWDIXMY-UHFFFAOYSA-N 0.000 claims abstract description 17
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims abstract description 16
- XPDWGBQVDMORPB-UHFFFAOYSA-N Fluoroform Chemical compound FC(F)F XPDWGBQVDMORPB-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052451 lead zirconate titanate Inorganic materials 0.000 claims description 42
- 239000000758 substrate Substances 0.000 claims description 24
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 18
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 10
- 239000003990 capacitor Substances 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 5
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052697 platinum Inorganic materials 0.000 claims description 4
- 229910052741 iridium Inorganic materials 0.000 claims description 3
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 claims description 3
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 2
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 claims description 2
- 239000010970 precious metal Substances 0.000 claims description 2
- 229910052707 ruthenium Inorganic materials 0.000 claims description 2
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 claims description 2
- 229910000457 iridium oxide Inorganic materials 0.000 claims 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 229910052814 silicon oxide Inorganic materials 0.000 description 10
- 238000010586 diagram Methods 0.000 description 8
- 238000001020 plasma etching Methods 0.000 description 6
- 238000005240 physical vapour deposition Methods 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000005229 chemical vapour deposition Methods 0.000 description 4
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- 150000002831 nitrogen free-radicals Chemical class 0.000 description 2
- -1 nitrogen ions Chemical class 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 1
- 238000004380 ashing Methods 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 238000005268 plasma chemical vapour deposition Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
- H01L21/3105—After-treatment
- H01L21/311—Etching the insulating layers by chemical or physical means
- H01L21/31105—Etching inorganic layers
- H01L21/31111—Etching inorganic layers by chemical means
- H01L21/31116—Etching inorganic layers by chemical means by dry-etching
- H01L21/31122—Etching inorganic layers by chemical means by dry-etching of layers not containing Si, e.g. PZT, Al2O3
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L28/00—Passive two-terminal components without a potential-jump or surface barrier for integrated circuits; Details thereof; Multistep manufacturing processes therefor
- H01L28/40—Capacitors
- H01L28/55—Capacitors with a dielectric comprising a perovskite structure material
Definitions
- the present invention generally relates to etching ferroelectric materials and, more particularly, to the use of carbon-containing gases and nitrogen-containing gases to etch ferroelectric layers.
- PZT Lead zirconate titanate
- Various methods for processing PZT have been discussed in the art.
- process gases including boron trichloride (BCl 3 ) gas and argon (Ar) gas have been used.
- BCl 3 boron trichloride
- Ar argon
- an etching process comprises etching a PZT-based ferroelectric layer with a process gas, wherein the process gas includes boron trichloride gas and at least one auxiliary gas selected from the group consisting of a carbon-containing gas e.g., hydroflurocarbon and a nitrogen-containing gas.
- the at least one auxiliary gas may comprise, for example, CHF 3 , C 2 H 4 , N 2 , NF 3 , or combinations thereof.
- the process gas may further comprise argon. The use of an auxiliary gas limits side etching.
- a method of forming a capacitor having dielectric portions disposed between first electrodes and second electrodes comprises etching the first conductive layer to form first electrodes.
- the PZT-based ferroelectric layer is then etched with a process gas comprising boron trichloride and at least one auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas to form dielectric portions.
- the second conductive layer is then etched to form second electrodes.
- FIG. 1 a -FIG. 1 j are cross-sectional views of a substrate during various stages of processing according to one embodiment of the present invention
- FIG. 2( a ) depicts a schematic cross-sectional diagram of a dielectric portion formed using embodiments of the invention described herein.
- FIG. 2( b ) depicts a schematic diagram showing the cross section of the PZT layer etched using a process gas composed of only BCl 3 gas and Ar gas;
- FIG. 3 is a schematic diagram showing an exemplary plasma etching apparatus that may be used to practice embodiments of the invention described herein;
- FIG. 4 is a circuit diagram showing a capacitor comprising a memory cell formed by the etching process according to embodiments of the invention described herein;
- FIG. 5 is a graph depicting a hysteresis phenomenon of a ferroelectric material that may be etched using embodiments of the invention described herein.
- FIG. 1 a -FIG. 1 j are cross-sectional views of a substrate during various stages of processing according to one embodiment of the present invention.
- a conductive layer such as platinum (Pt) layer 3 is formed on a substrate 2 .
- the substrate 2 may be, for example, a semiconductor substrate such as a silicon (Si) wafer, a Si wafer having an insulating layer such as a silicon oxide (SiO 2 ) layer formed thereon, or a Si wafer upon which a partially completed semiconductor integrated circuit has been fabricated.
- the method employed for forming Pt layer 3 may be, for example, a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method.
- a ferroelectric layer such as a PZT layer 4 is formed on the first Pt layer 3 .
- the PZT layer 4 may be formed by a physical vapor deposition (PVD) process or a sol-gel process.
- a conductive layer such as an iridium (lr) layer 5 is formed on the PZT layer 4 , using a deposition method such as, for example, chemical vapor deposition (CVD) or PVD.
- CVD chemical vapor deposition
- PVD physical vapor deposition
- an SiO 2 layer 6 is formed on the lr layer 5 , as shown in FIG. 1 d.
- the SiO 2 layer 6 may be formed by, for example, a plasma CVD method using tetraethyl orthosilicate (TEOS) and oxygen (O 2 ) gas as raw materials.
- TEOS tetraethyl orthosilicate
- O 2 oxygen
- a resist layer (not shown) is applied on the SiO 2 layer 6 , and the resist layer is then exposed via a photomask having a predetermined pattern.
- resist masks 7 are thereby formed.
- the resist masks 7 are then used to etch the SiO 2 layer 6 , as shown in FIG. 1 f.
- This etching may be performed using, for example, a plasma etching apparatus appropriate for SiO 2 layer etching.
- a process gas including, for example, Cl 2 and CF 4 may be used to perform the SiO 2 layer etching.
- the resist mask 7 is removed by ashing.
- hard masks 8 are formed as shown in FIG. 1 g.
- the substrate 2 is placed in an etching chamber of a predetermined plasma etching apparatus. After the substrate 2 is placed in the etching chamber, a substrate support temperature is maintained within a range not lower than 250 degrees and not higher than 400 degrees. The temperature may be, for example, 310 degrees. After the temperature of the substrate 2 becomes stable at 310 degrees, process gas is introduced into the etching chamber. The portions of the lr layer 5 that are not covered by the hard masks 8 are etched, and the portions of the lr layer 5 that are covered by hard masks 8 are unetched, thus forming upper lr electrodes 9 , as shown in FIG. 1 h.
- the process gas used to etch the IR layer 5 may include chlorine (Cl 2 ) gas and oxygen (O 2 ) gas.
- the PZT layer 4 is etched in the same etching chamber as used to etch the lr layer 5 .
- the etching of the PZT layer 4 may be performed at a substrate temperature substantially the same as that during the etching of the Pt layer 3 .
- a process gas comprising BCl 3 gas, Ar gas and a carbon-containing gas such as a fluorohydrocarbon, e.g., CHF 3 may be used to etch the PZT layer 4 .
- Process conditions useful for etching the PZT layer 4 are, for example, a flow rate of BCl 3 of 40 standard cubic centimeters per minute (sccm), a flow rate of Ar of 90 sccm, a flow rate of CHF 3 of 5 sccm, a chamber pressure of about 2.0 Pa (15 mTorr), a power output of for plasma generation of 1500W, a substrate bias output of 150W, and a substrate temperature of 310 degrees.
- the supply of BCl 3 gas and Ar gas is terminated, and Cl 2 gas and O 2 are supplied to etch the Pt layer 3 .
- upper Pt electrodes 11 are formed, and the formation of a ferroelectric capacitor 1 is completed, as shown in FIG. 1 j.
- the hard masks 8 may remain in the semiconductor device without being removed. Alternatively, the hard masks 8 are removed by etching the hard masks 8 with a hydrofluoric acid solution.
- FIG. 2 a depicts a schematic cross-sectional diagram of the dielectric portion 10 formed using the method described above. This cross-sectional diagram was prepared on the basis of a SEM photograph. The sidewall of dielectric portion 10 composed of PZT is substantially uniform, thereby indicating that side-etching has been sufficiently prevented using the above-described method.
- FIG. 2 b depicts a schematic cross-sectional diagram of the dielectric portion 10 formed from a PZT layer formed on an Ru layer 30 .
- the dielectric portion 10 was etched without supplying CHF 3 .
- an overhang is formed on a sidewall 40 of the PZT layer 4 .
- the presence of the overhang reveals that significant side-etching occurred during the etching of the PZT layer 4 .
- the flow rate of the carbon-containing gas, such as CHF 3 , supplied to the chamber is, in an illustrative embodiment, not less than 1 sccm.
- the flow rate of the carbon-containing gas is less than 1 sccm, prevention of the side-etching effect may be insufficient because the carbon or the organic substances generated from the decomposition of, for example, CHF 3 , cannot cover the sidewall sufficiently.
- the flow rate of carbon-containing gas is greater than 10 sccm, the material adhering to the sidewall 40 may be too thick and peel off, thus failing to prevent side-etching.
- the carbon-containing gas may be supplied at a flow rate that is not less than 1% by mole with respect to a total flow rate of the process gas supplied during the etching. It is believed that if the ratio of the carbon-containing gas to BCl 3 gas is too small, the side-etching cannot be prevented due to an insufficient amount of material adhering to the sidewall. It is also believed that if the carbon-containing gas is supplied in a concentration greater than 10% by mole, the carbon-containing gas would inhibit the etching of the PZT layer 4 .
- the process gas used to etch the PZT layer 4 comprises a nitrogen-containing gas such as N 2 .
- the flow rate of the N-containing gas may be between 1 standard cubic centimeter per second (sccm) and 10 sccm.
- the ratio of the N-containing gas to the total process gas flow rate may be between 1% by mole and 10% by mole.
- active nitrogen species such as nitrogen radicals and nitrogen ions generated within the plasma combine with the reaction products of other gases forming products that adhere to the sidewall of the PZT layer to prevent the sidewall from etching.
- the use of nitrogen-containing gas may result in preventing side wall etching due to the generation of nitrogen radicals and nitrogen ions in the plasma.
- the process gas when etching the PZT layer 4 , the process gas comprises BCl 3 , a carbon-containing gas and a nitrogen-containing gas.
- the flow rate of the N-containing gas may be substantially the same as the flow rate of the CHF 3 gas.
- FIG. 3 shows a plasma etching apparatus employed to etch the lr layer 5 , the Pt layer 3 , and the PZT-based ferroelectric layer 4 .
- the substrate 2 after having a multi-layer film formed thereon, is placed in an etching chamber 31 of an etching apparatus 30 .
- the plasma etching apparatus 30 comprises the etching chamber 31 , a gas supply source 32 , a high-frequency power source 33 , a temperature regulator 34 and a gas exhausting system (not shown).
- An electrode 35 for supplying high-frequency power, and a substrate support 36 for carrying substrate 2 are disposed in the etching chamber 31 .
- the substrate support 36 has, for example, a heater 36 a disposed therein.
- the heater 36 a is controlled by the temperature regulator 34 , and the temperature of the substrate support 36 is thereby set to a predetermined temperature.
- the temperature of the substrate 2 placed on the substrate support 36 is defined by the temperature of the substrate support 36 .
- the temperature of the substrate support 36 can be raised to, for example, about 400 degrees, as a temperature within the range suitable for the etching of the PZT-based ferroelectric layer 4 . After being placed on the substrate support 36 , the substrate 2 is maintained at a temperature exceeding 100 degrees.
- FIG. 4 is a circuit diagram showing an example of a memory cell semiconductor 20 device comprising a ferroelectric capacitor 1 and a field effect transistor (FET).
- the capacitor is formed using an etching process according to embodiments described herein.
- the capacitor 1 comprises dielectric portions such as the dielectric portions 10 shown in FIG. 1 i.
- the dielectric portions 10 are ferroelectric and may thereby exhibit hysteresis characteristics, as depicted in FIG. 6, thereby providing the device 20 with a memory effect.
- the abscissa represents an applied electric field and the ordinate represents polarization.
- the scope of the present invention is not limited to the embodiments discussed above.
- the conductive layers are described above as iridium (Ir) and platinum (Pt) layers, other materials, including other precious metals such as ruthenium (Ru), and the like, as well as conductive oxides such as iridium oxide (IrO 2 ) and ruthenium oxide (RuO 2 ) may be used.
- the ferroelectric layer is described above as a PZT layer, the ferroelectric layer may include other elements such as lanthanum (La), niobium (Nb) and bismuth (Bi).
- the above description details the use of the etching method for use in the fabrication of a capacitor, the etching method of the present invention may be used to form other devices.
- the hard masks are described above as a SiO 2 layer, hard masks comprising a silicon-based inorganic insulating layer or hard masks composed of titanium nitride (TiN) may also be used.
- the carbon-containing gas is not limited to CHF 3 .
- it may be a compound represented by a chemical formula C x H y or C x H y F z , such as, for example, C 2 H 4 .
- the nitrogen-containing gas is not limited to N 2 and may include, for example, NF 3 .
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Abstract
A method of etching a ferroelectric layer comprises etching a ferroelectric layer using boron trichloride gas and at least one auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas. The carbon-containing gas may include CHF3 or C2H4. The nitrogen-containing gas may include N2 or NF3. The method reduces side etching of ferroelectric layers, and in particular, PZT-based ferroelectric layers and thereby improves electrical performance and reliability of devices made therefrom.
Description
- This application claims priority to co-pending Japanese patent application number 2001-232528, filed in Japan on Jul. 31, 2001.
- 1. Field of the Invention
- The present invention generally relates to etching ferroelectric materials and, more particularly, to the use of carbon-containing gases and nitrogen-containing gases to etch ferroelectric layers.
- 2. Description of the Related Art
- Lead zirconate titanate (PZT), a ferroelectric oxide material, is often used for memory cell applications. Various methods for processing PZT have been discussed in the art. In order to etch PZT, process gases including boron trichloride (BCl3) gas and argon (Ar) gas have been used. However, using boron trichloride (BCl3) gas and argon (Ar) gas to etch PZT layers has been found to result in etching the side of the PZT layer. This side-etching may result in various problems in subsequent processing steps. For example, when forming an insulating layer on the PZT layer, side-etching may result in unsatisfactory step coverage of the insulating layer. Furthermore, variations in side-etching of the PZT layer may result in memory cells formed therefrom having different capacitance, thereby causing unreliable electrical performance. Therefore, a need exists to reduce side-etching in PZT layers.
- Embodiments of the present invention generally relate to a method of etching a PZT-based ferroelectric layer with limited side etching. In one embodiment of the invention, an etching process comprises etching a PZT-based ferroelectric layer with a process gas, wherein the process gas includes boron trichloride gas and at least one auxiliary gas selected from the group consisting of a carbon-containing gas e.g., hydroflurocarbon and a nitrogen-containing gas. The at least one auxiliary gas may comprise, for example, CHF3, C2H4, N2, NF3, or combinations thereof. The process gas may further comprise argon. The use of an auxiliary gas limits side etching.
- In another embodiment of the invention, a method of forming a capacitor having dielectric portions disposed between first electrodes and second electrodes is provided. The process comprises etching the first conductive layer to form first electrodes. The PZT-based ferroelectric layer is then etched with a process gas comprising boron trichloride and at least one auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas to form dielectric portions. The second conductive layer is then etched to form second electrodes.
- So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.
- It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
- FIG. 1a-FIG. 1j are cross-sectional views of a substrate during various stages of processing according to one embodiment of the present invention;
- FIG. 2(a) depicts a schematic cross-sectional diagram of a dielectric portion formed using embodiments of the invention described herein. FIG. 2(b) depicts a schematic diagram showing the cross section of the PZT layer etched using a process gas composed of only BCl3 gas and Ar gas;
- FIG. 3 is a schematic diagram showing an exemplary plasma etching apparatus that may be used to practice embodiments of the invention described herein;
- FIG. 4 is a circuit diagram showing a capacitor comprising a memory cell formed by the etching process according to embodiments of the invention described herein; and
- FIG. 5 is a graph depicting a hysteresis phenomenon of a ferroelectric material that may be etched using embodiments of the invention described herein.
- Embodiments described herein relate to a method of etching a PZT-based ferroelectric layer. FIG. 1a-FIG. 1j are cross-sectional views of a substrate during various stages of processing according to one embodiment of the present invention. As shown in FIG. 1a, a conductive layer such as platinum (Pt)
layer 3 is formed on asubstrate 2. Thesubstrate 2 may be, for example, a semiconductor substrate such as a silicon (Si) wafer, a Si wafer having an insulating layer such as a silicon oxide (SiO2) layer formed thereon, or a Si wafer upon which a partially completed semiconductor integrated circuit has been fabricated. The method employed for formingPt layer 3, may be, for example, a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. As shown in FIG. 1b, a ferroelectric layer such as a PZT layer 4 is formed on thefirst Pt layer 3. The PZT layer 4 may be formed by a physical vapor deposition (PVD) process or a sol-gel process. Next, as shown in FIG. 1c, a conductive layer such as an iridium (lr)layer 5 is formed on the PZT layer 4, using a deposition method such as, for example, chemical vapor deposition (CVD) or PVD. As a result, a multi-layer film composed of the platinum (Pt)layer 3, the PZT layer 4 and thelr layer 5 is formed. - Subsequently, in order to form hard masks on the multi-layer film, an SiO2 layer 6 is formed on the
lr layer 5, as shown in FIG. 1d. The SiO2 layer 6 may be formed by, for example, a plasma CVD method using tetraethyl orthosilicate (TEOS) and oxygen (O2) gas as raw materials. Thereafter, a resist layer (not shown) is applied on the SiO2 layer 6, and the resist layer is then exposed via a photomask having a predetermined pattern. As shown in FIG. 1e, resist masks 7 are thereby formed. The resist masks 7 are then used to etch the SiO2 layer 6, as shown in FIG. 1f. This etching may be performed using, for example, a plasma etching apparatus appropriate for SiO2 layer etching. A process gas including, for example, Cl2 and CF4, may be used to perform the SiO2 layer etching. After etching the SiO2 layer, the resist mask 7 is removed by ashing. As a result,hard masks 8 are formed as shown in FIG. 1g. - After the formation of the
hard masks 8, thesubstrate 2 is placed in an etching chamber of a predetermined plasma etching apparatus. After thesubstrate 2 is placed in the etching chamber, a substrate support temperature is maintained within a range not lower than 250 degrees and not higher than 400 degrees. The temperature may be, for example, 310 degrees. After the temperature of thesubstrate 2 becomes stable at 310 degrees, process gas is introduced into the etching chamber. The portions of thelr layer 5 that are not covered by thehard masks 8 are etched, and the portions of thelr layer 5 that are covered byhard masks 8 are unetched, thus forming upperlr electrodes 9, as shown in FIG. 1h. The process gas used to etch theIR layer 5 may include chlorine (Cl2) gas and oxygen (O2) gas. - After the
lr electrodes 9 are formed, the PZT layer 4 is etched in the same etching chamber as used to etch thelr layer 5. The etching of the PZT layer 4 may be performed at a substrate temperature substantially the same as that during the etching of thePt layer 3. A process gas comprising BCl3 gas, Ar gas and a carbon-containing gas such as a fluorohydrocarbon, e.g., CHF3 may be used to etch the PZT layer 4. Process conditions useful for etching the PZT layer 4 are, for example, a flow rate of BCl3 of 40 standard cubic centimeters per minute (sccm), a flow rate of Ar of 90 sccm, a flow rate of CHF3 of 5 sccm, a chamber pressure of about 2.0 Pa (15 mTorr), a power output of for plasma generation of 1500W, a substrate bias output of 150W, and a substrate temperature of 310 degrees. As a result of the etching of PZT layer 4, portions of the PZT layer 4 that are not covered byhard masks 8 andlr electrodes 9 are removed, thereby formingdielectric portions 10 as indicated in FIG. 1f. - Subsequently, the supply of BCl3 gas and Ar gas is terminated, and Cl2 gas and O2 are supplied to etch the
Pt layer 3. Upon etching thePt layer 3,upper Pt electrodes 11 are formed, and the formation of aferroelectric capacitor 1 is completed, as shown in FIG. 1j. Thehard masks 8 may remain in the semiconductor device without being removed. Alternatively, thehard masks 8 are removed by etching thehard masks 8 with a hydrofluoric acid solution. - FIG. 2a depicts a schematic cross-sectional diagram of the
dielectric portion 10 formed using the method described above. This cross-sectional diagram was prepared on the basis of a SEM photograph. The sidewall ofdielectric portion 10 composed of PZT is substantially uniform, thereby indicating that side-etching has been sufficiently prevented using the above-described method. - For the purpose of comparison, FIG. 2b depicts a schematic cross-sectional diagram of the
dielectric portion 10 formed from a PZT layer formed on anRu layer 30. Thedielectric portion 10 was etched without supplying CHF3. As shown in FIG. 2b, an overhang is formed on asidewall 40 of the PZT layer 4. The presence of the overhang reveals that significant side-etching occurred during the etching of the PZT layer 4. - Without wishing to be bound by any particular theory or mechanism, the inventors believe that the side-etching of the PZT layer4 is prevented by the carbon, specifically, organic substances such as carbon-containing fragments generated from the decomposition of CHF3 that adhere to the
sidewall 40 of the PZT layer 4. - The flow rate of the carbon-containing gas, such as CHF3, supplied to the chamber is, in an illustrative embodiment, not less than 1 sccm. When the flow rate of the carbon-containing gas is less than 1 sccm, prevention of the side-etching effect may be insufficient because the carbon or the organic substances generated from the decomposition of, for example, CHF3, cannot cover the sidewall sufficiently. Furthermore, if the flow rate of carbon-containing gas is greater than 10 sccm, the material adhering to the
sidewall 40 may be too thick and peel off, thus failing to prevent side-etching. - Furthermore, the carbon-containing gas may be supplied at a flow rate that is not less than 1% by mole with respect to a total flow rate of the process gas supplied during the etching. It is believed that if the ratio of the carbon-containing gas to BCl3 gas is too small, the side-etching cannot be prevented due to an insufficient amount of material adhering to the sidewall. It is also believed that if the carbon-containing gas is supplied in a concentration greater than 10% by mole, the carbon-containing gas would inhibit the etching of the PZT layer 4.
- In an alternative embodiment of the invention, the process gas used to etch the PZT layer4 comprises a nitrogen-containing gas such as N2. The flow rate of the N-containing gas may be between 1 standard cubic centimeter per second (sccm) and 10 sccm. Furthermore, the ratio of the N-containing gas to the total process gas flow rate may be between 1% by mole and 10% by mole. Without wishing to be bound by any particular theory or mechanism, the inventors believe that active nitrogen species such as nitrogen radicals and nitrogen ions generated within the plasma combine with the reaction products of other gases forming products that adhere to the sidewall of the PZT layer to prevent the sidewall from etching. The use of nitrogen-containing gas may result in preventing side wall etching due to the generation of nitrogen radicals and nitrogen ions in the plasma.
- In one embodiment of the invention, when etching the PZT layer4, the process gas comprises BCl3, a carbon-containing gas and a nitrogen-containing gas. The flow rate of the N-containing gas may be substantially the same as the flow rate of the CHF3 gas.
- FIG. 3 shows a plasma etching apparatus employed to etch the
lr layer 5, thePt layer 3, and the PZT-based ferroelectric layer 4. Thesubstrate 2, after having a multi-layer film formed thereon, is placed in anetching chamber 31 of anetching apparatus 30. Theplasma etching apparatus 30 comprises theetching chamber 31, agas supply source 32, a high-frequency power source 33, atemperature regulator 34 and a gas exhausting system (not shown). Anelectrode 35 for supplying high-frequency power, and asubstrate support 36 for carryingsubstrate 2 are disposed in theetching chamber 31. Thesubstrate support 36 has, for example, aheater 36 a disposed therein. Theheater 36 a is controlled by thetemperature regulator 34, and the temperature of thesubstrate support 36 is thereby set to a predetermined temperature. The temperature of thesubstrate 2 placed on thesubstrate support 36 is defined by the temperature of thesubstrate support 36. In theplasma etching apparatus 30, the temperature of thesubstrate support 36 can be raised to, for example, about 400 degrees, as a temperature within the range suitable for the etching of the PZT-based ferroelectric layer 4. After being placed on thesubstrate support 36, thesubstrate 2 is maintained at a temperature exceeding 100 degrees. - FIG. 4 is a circuit diagram showing an example of a
memory cell semiconductor 20 device comprising aferroelectric capacitor 1 and a field effect transistor (FET). The capacitor is formed using an etching process according to embodiments described herein. Thecapacitor 1 comprises dielectric portions such as thedielectric portions 10 shown in FIG. 1i. Thedielectric portions 10 are ferroelectric and may thereby exhibit hysteresis characteristics, as depicted in FIG. 6, thereby providing thedevice 20 with a memory effect. In FIG. 6, the abscissa represents an applied electric field and the ordinate represents polarization. - Using the etching process of the present invention, the side-etching of the PZT layer is prevented. Semiconductor devices manufactured using the method of the present invention are advantageous in that the reliability of the devices formed is improved.
- The scope of the present invention is not limited to the embodiments discussed above. For example, while the conductive layers are described above as iridium (Ir) and platinum (Pt) layers, other materials, including other precious metals such as ruthenium (Ru), and the like, as well as conductive oxides such as iridium oxide (IrO2) and ruthenium oxide (RuO2) may be used. Furthermore, while the ferroelectric layer is described above as a PZT layer, the ferroelectric layer may include other elements such as lanthanum (La), niobium (Nb) and bismuth (Bi). Furthermore, the above description details the use of the etching method for use in the fabrication of a capacitor, the etching method of the present invention may be used to form other devices. Furthermore, while the hard masks are described above as a SiO2 layer, hard masks comprising a silicon-based inorganic insulating layer or hard masks composed of titanium nitride (TiN) may also be used.
- Similarly, the carbon-containing gas is not limited to CHF3. In general, it may be a compound represented by a chemical formula CxHy or CxHyFz, such as, for example, C2H4. Furthermore, the nitrogen-containing gas is not limited to N2 and may include, for example, NF3.
- While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (21)
1. A method of etching a ferroelectric layer, the method comprising:
providing a substrate comprising a ferroelectric layer; and
supplying a process gas comprising boron trichloride and at least one auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas.
2. The method of claim 1 wherein the process gas comprises boron trichloride, a carbon-containing gas and a nitrogen-containing gas.
3. The method of claim 2 wherein the carbon-containing gas has a flow rate that is substantially equal to a flow rate of the nitrogen-containing gas.
4. The method of claim 1 , wherein a flow rate of the at least one auxiliary gas is not less than 1 sccm and not greater than 10 sccm.
5. The method of claim 1 , wherein a flow rate of the at least one auxiliary gas is not less than 1% by mole and not greater than 10% by mole with respect to a total flow rate of process gas supplied during etching.
6. The method of claim 1 , wherein the carbon-containing gas is selected from the group consisting of CHF3 and C2H4.
7. The method of claim 1 , wherein the nitrogen-containing gas is selected from the group consisting of N2 and NF3.
8. The method of claim 1 , wherein the process gas further comprises argon.
9. The method of claim 1 wherein hard masks are used to etch the ferroelectric layer.
10. The method of claim 1 wherein the ferrorelectric material is lead zirconate titanate (PZT).
11. A method of forming a capacitor, comprising:
forming a multi-layer film comprising a first conductive layer, a ferroelectric layer, and a second conductive layer;
etching the first conductive layer to form first electrodes;
etching the ferroelectric layer with a process gas comprising boron trichloride and an auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas; and
etching the second conductive layer to form the second electrodes.
12. The method of claim 11 , wherein the first conductive layer and the second conductive layer include a material selected from the group consisting of precious metals and conductive oxides.
13. The method of claim 11 , wherein the first conductive layer and the second conductive layer include a material selected from the group consisting of iridium, platinum and ruthenium, iridium oxide (lrO2), and ruthenium oxide (RuO2).
14. The method of claim 11 wherein the process gas comprises boron trichloride, a carbon-containing gas and a nitrogen-containing gas.
15. The method of claim 11 , wherein the at least one auxiliary gas has a flow rate not less than 1 sccm and not greater than 10 sccm.
16. The method of claim 11 , wherein the at least one auxiliary gas has a flow rate not less than 1% by mole and not greater than 10% by mole with respect to a total flow rate of process gas supplied during etching.
17. The method of claim 11 , wherein the carbon-containing gas is selected from the group consisting of CHF3 and C2H4.
18. The method of claim 11 , wherein the nitrogen-containing gas is selected from the group consisting of N2 and NF3.
19. The method of claim 11 , wherein the process gas further comprises argon.
20. The method of claim 11 wherein the ferroelectric material is lead zirconate titanate (PZT).
21. The method of claim 11 further comprising:
forming hard masks on the second conductive layer; and
using the hard masks to etch the second conductive layer, the ferroelectric layer, and the first conductive layer.
Applications Claiming Priority (2)
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JP2001-232528 | 2001-07-31 | ||
JP2001232528A JP2003059906A (en) | 2001-07-31 | 2001-07-31 | Etching method, and method of forming capacitor |
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US10/210,550 Abandoned US20030047532A1 (en) | 2001-07-31 | 2002-07-31 | Method of etching ferroelectric layers |
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US (1) | US20030047532A1 (en) |
JP (1) | JP2003059906A (en) |
TW (1) | TW565886B (en) |
WO (1) | WO2003012851A2 (en) |
Cited By (3)
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WO2005010958A1 (en) * | 2003-07-28 | 2005-02-03 | Infineon Technologies Ag | Fabrication of a feram capacitor using a noble metal hardmask |
US20050164511A1 (en) * | 2003-05-30 | 2005-07-28 | Tokyo Electron Limited | Method and system for etching a high-k dielectric material |
US20100003828A1 (en) * | 2007-11-28 | 2010-01-07 | Guowen Ding | Methods for adjusting critical dimension uniformity in an etch process with a highly concentrated unsaturated hydrocarbon gas |
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US7217665B2 (en) * | 2002-11-20 | 2007-05-15 | Applied Materials, Inc. | Method of plasma etching high-K dielectric materials with high selectivity to underlying layers |
JP4901105B2 (en) | 2003-04-15 | 2012-03-21 | 富士通セミコンダクター株式会社 | Manufacturing method of semiconductor device |
KR100732026B1 (en) | 2005-04-08 | 2007-06-27 | 후지쯔 가부시끼가이샤 | Method for fabricating semiconductor device |
JP4515956B2 (en) * | 2005-05-02 | 2010-08-04 | 株式会社日立ハイテクノロジーズ | Sample etching method |
JP2009266952A (en) * | 2008-04-23 | 2009-11-12 | Seiko Epson Corp | Method for manufacturing and manufacturing apparatus for device |
CN102484065B (en) * | 2009-09-09 | 2015-04-01 | 株式会社爱发科 | Method for operating substrate processing apparatus |
US10692759B2 (en) * | 2018-07-17 | 2020-06-23 | Applied Materials, Inc. | Methods for manufacturing an interconnect structure for semiconductor devices |
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US6100201A (en) * | 1997-03-05 | 2000-08-08 | Nec Corporation | Method of forming a semiconductor memory device |
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US6559001B2 (en) * | 2001-05-30 | 2003-05-06 | International Business Machines Corporation | Methods of patterning a multi-layer film stack and forming a lower electrode of a capacitor |
US6620733B2 (en) * | 2001-02-12 | 2003-09-16 | Lam Research Corporation | Use of hydrocarbon addition for the elimination of micromasking during etching of organic low-k dielectrics |
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ATE533178T1 (en) * | 1998-09-09 | 2011-11-15 | Texas Instruments Inc | INTEGRATED CIRCUIT WITH CAPACITOR AND RELATED PRODUCTION METHOD |
US6368517B1 (en) * | 1999-02-17 | 2002-04-09 | Applied Materials, Inc. | Method for preventing corrosion of a dielectric material |
US6436838B1 (en) * | 2000-04-21 | 2002-08-20 | Applied Materials, Inc. | Method of patterning lead zirconium titanate and barium strontium titanate |
DE10039411A1 (en) * | 2000-08-11 | 2002-02-28 | Infineon Technologies Ag | Structuring ferroelectric layers |
-
2001
- 2001-07-31 JP JP2001232528A patent/JP2003059906A/en active Pending
-
2002
- 2002-07-31 WO PCT/US2002/024346 patent/WO2003012851A2/en unknown
- 2002-07-31 US US10/210,550 patent/US20030047532A1/en not_active Abandoned
- 2002-08-08 TW TW091117927A patent/TW565886B/en not_active IP Right Cessation
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US5443688A (en) * | 1993-12-02 | 1995-08-22 | Raytheon Company | Method of manufacturing a ferroelectric device using a plasma etching process |
US6100201A (en) * | 1997-03-05 | 2000-08-08 | Nec Corporation | Method of forming a semiconductor memory device |
US6232174B1 (en) * | 1998-04-22 | 2001-05-15 | Sharp Kabushiki Kaisha | Methods for fabricating a semiconductor memory device including flattening of a capacitor dielectric film |
US6620733B2 (en) * | 2001-02-12 | 2003-09-16 | Lam Research Corporation | Use of hydrocarbon addition for the elimination of micromasking during etching of organic low-k dielectrics |
US6559001B2 (en) * | 2001-05-30 | 2003-05-06 | International Business Machines Corporation | Methods of patterning a multi-layer film stack and forming a lower electrode of a capacitor |
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US20050164511A1 (en) * | 2003-05-30 | 2005-07-28 | Tokyo Electron Limited | Method and system for etching a high-k dielectric material |
US7709397B2 (en) | 2003-05-30 | 2010-05-04 | Tokyo Electron Limited | Method and system for etching a high-k dielectric material |
WO2005010958A1 (en) * | 2003-07-28 | 2005-02-03 | Infineon Technologies Ag | Fabrication of a feram capacitor using a noble metal hardmask |
US20100003828A1 (en) * | 2007-11-28 | 2010-01-07 | Guowen Ding | Methods for adjusting critical dimension uniformity in an etch process with a highly concentrated unsaturated hydrocarbon gas |
Also Published As
Publication number | Publication date |
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JP2003059906A (en) | 2003-02-28 |
WO2003012851A2 (en) | 2003-02-13 |
TW565886B (en) | 2003-12-11 |
WO2003012851A3 (en) | 2003-04-24 |
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