METHOD FOR FORMING A STRUCTURE USING REDEPOSITION

Abstract: A method is described for forming a structure by redepositing a starting material (5) on sidewalls of a foundation (15) during an etch of the starting material. The starting material can be a layer of conductive material formed into an electrode of a capacitor. Multiple layers of conductive material (50, 55) and dielectric material (60) can be etched to form a multilayered structure, such as a capacitor.

Description: METHOD FOR FORMING A STRUCTURE USING REDEPOSITION Field of the Invention The invention relates to the fabrication of semiconductors and more particularly to the fabrication of a structure formed by redepositing a starting material. Background of the Invention Side all passivation occurs during a chemical deposition on sidewalls of a structure. Typically, sidewall passivation is used to enhance a mask in order to increase the integrity of the mask thereby eliminating undercut and other etching defects caused when portions of the mask itself are consumed during an etch. The chemical deposit is then typically removed since it is used to perform the process and is not a structural goal of the total process. Summary of the Invention The invention is a method for forming a structure wherein a starting material is etched and redeposited during the etch on a sidewall of a foundation. In one embodiment the foundation is removed subsequent to the etch to leave the redeposited starting material and unetched starting material to form the structure. This structure may be a capacitor electrode. In this embodiment a capacitor may be formed by forming a dielectric layer and a conductive layer overlying the structure. In a second embodiment the foundation may form an integral part of the final structure. In this case a capacitor can be formed by depositing a dielectric and a conductive layer overlying the structure. In still a further embodiment a capacitor may be formed using a single etch wherein redeposition occurs during the single etch. In this case two conductive layers are formed overlying a substrate and a dielectric layer is formed interposed between the conductive layers. The etch is performed after masking of the layers with a foundation. The etch creates particles or portions of each layer which are then deposited on a sidewall of the foundation to create the capacitor. When a photoresist mask is used as the foundation the size of the structure made by the method of the invention is determined only by photolithography limits. The smallest size mask definable by lithography may be used for forming the container cell. Brief Description of the Drawings Figure 1 is a cross-sectional view of a masked portion of a substrate having a starting material and positioned in an etching environment; Figure 2 is the portion of the substrate shown in Figure 1 following an etch and redeposit of the starting material; Figure 3 is the portion of the substrate shown in Figure 2 following the removal of the mask; Figure 4 is a top planar view of the portion of the substrate shown in Figure 3; Figure 5 is the portion of the substrate and the structure shown in Figure 3 following the formation of a dielectric layer, a conductive layer and a mask; Figure 6 is the portion of the substrate and the structure shown in Figure 5 following an etch of the dielectric layer and the conductive layer and following the removal of the mask; Figure 7 is a cross-sectional view of a portion of a substrate and masked conductive layers interposed with a dielectric layer; Figure 8 is the portion of the substrate shown in Figure 7 following etching and redeposition of the conductive layers and the dielectric layer; Figure 9 is the cross sectional view of the portion of the substrate shown in Figure 8 following the removal of the mask; Figure 10 is a cross-sectional view of conductive layers interposed with a dielectric layer and masked with a conductive plug and overlying a portion of a substrate; Figure 11 is the portion of the substrate of Figure 10 following an etch and redeposition of the conductive layers and the dielectric layer; Figure 12 is a cross-sectional view of a dielectric layer and a conductive layer redeposited on a sidewall of a conductive plug; Figure 13 is a copy of a photograph taken with a scanning electron microscope showing an isometric view of a structure of the invention; and Figure 14 is a copy of a photograph taken with a scanning electron microscope showing a cross-sectional view of a structure of the invention. Detailed Description of the Invention A method for forming a structure by redepositing a deposited material during an etch of the deposited material is disclosed. The redeposit is mechanical in that the etch accelerates particles of the deposited material some of which bombard sidewalls of a foundation provided to create a base on which the accelerated particles can form the redeposited material. Thus the redeposited material has the same chemical composition as the originally deposited (or formed) material. In one embodiment shown in Figure 1 a starting material 5 is deposited to overlie a substrate 10. In a preferred embodiment the starting material 5 is platinum although other materials such as TiPt, TiNPt, TiAlN-Pt, Ru, RuO,, RuPt, RuO 2 Pt, W, WPt, WSi, Ti, TiSi, Ta, TaN, TaSi, doped and undoped Poly Si, Al, Pd and Ir may be used. A foundation 15 is formed overlying the starting material 5. In this embodiment the foundation 15 is a photoresist mask the size of which is limited only by photolithic techniques. Although the foundation 15 shown in the accompanying drawings is rectangular any shape may be formed. The starting material 5 is etched in an argon plasma environment at radio frequencies using an Ion Mill etcher as an RF ion source 20. Etching with argon in an Ion Mill etcher is well known to those skilled in the art. It is also possible to use other materials as etchants. During etching portions of the starting material 5, in this case platinum, are redeposited as portions 25 on the sidewalls of the foundation 15, see Figure 2. Typically, the angle of incidence between the starting material 5 and the trajectory of an accelerated etchant ion is selected to maximize the amount of redeposition of the starting material 5 on the sidewalls of the foundation 15. A 90 degree angle of incidence typically works well. In Figures 3 and 4 the photoresist has been striped leaving the structure 27 comprising platinum portions 5 and 25 formed by the method of the invention. The platinum structure 27 may be used as a storage node electrode for a container cell capacitor. In this case the process is continued, as shown in Figures 5 and 6, in order to complete the capacitor fabrication. In Figure 5 a dielectric layer 30 has been deposited to overlie the platinum structure 27. This deposition is followed by the deposition, typically a sputtering, of a conductive layer 35 to overlie the dielectric layer 30. The dielectric layer 30 and the conductive layer 35 are then patterned with mask 38. The dielectric layer 30 and the conductive layer 35 are etched according to means known to those skilled in the art to form the capacitor 40 shown in Figure 6. In a case where Osmium, Iridium, or Ruthenium is used in place of Platinum, the structures formed by the process of the invention may be oxidized thereby forming OsO x , IrO 2 or RuO, respectively. In a further embodiment, shown in Figures 7-9, three starting materials, two conductive layers 50 and 55 having a dielectric layer 60 interposed therein, are deposited overlying a substrate 65 (see Figure 7). The conductive layers 50 and 55 are patterned with a foundation 70, typically a photoresist mask, and then the conductive layers 50 and 55 and the dielectric layer 60 are etched insitu, typically using a single etch step. In Figure 8, as conductive layer 55 is etched it is redeposited on the sidewalls of the foundation 70 to form a vertical conductive (to the substrate) layer 75. The etch continues and the dielectric layer 60 is redeposited to form a vertical dielectric layer 80. The etch further continues to etch conductive layer 50 which is redeposited during the etch as vertical conductive layer 90. Among the appropriate materials for the conductive layers 50 and 55 are platinum, conductive oxides, and polysilicon. The redeposited layers 75 and 90 are the same material as the original conductive layers 50 and 55. Therefore if 50 and 55 are platinum the redeposited layers 75 and 90 are also platinum. The same is true of the dielectric layer. Dielectric layer 60 may be chosen from a group of dielectrics selected from the group consisting of Ba(l-x)SrxO 3 , PbZr(l-x)TixO 3 . PZT with various dopants such as LA etc., Sr(l-x)BixTaO 3 , Sr(l-x)BixTiO 3 and all of the other Smolenski compounds, PbMg(l-x)NbxTiO 3 (PMN), compounds with PbTiO 3 (PMN-PT), CaBi,Nb,O 9 , SrBi,Nb 2 O 9 , BaBi,Nb,O 9 , PbBi,Nb,O 9 , BiBi 2 NbTiO 9 , BaBi 4 Ti 4 O I5 , CaBi,Ta 2 O 9 , SrBi,Ta 2 O 9 , BaBi,Ta,O 9 , PbBi,Ta,O 9 , Bi 4 Ti 3 O l2 , SrBi 4 Ti 4 O l5 , BaBi 4 Ti 4 O 15 , PbBi 4 Ti 4 O 15 , (Pb, Sr)Bi,Nb 2 O 9 , (Pb, Ba)Bi,Nb,O 9 , (Ba, Ca)Bi,Nb,O 9 , (Ba, Sr)Bi 2 Nb 2 O 9 , BaBi 2 Nb_,O 9 , Bao 75 Bi 2 2 jTi 02s Nb 1 7S O 9 , Ba„ 5 Bi, 5 Ti 0 5 Nb| 5 O 9 , Bi 3 TiNbO 9 , SrBi,Nb,O 9 , Sr 0 8 Bi 2 2 Ti 02 Nb l g O 9 , Sr 06 Bi 24 Ti 04 Nb, 6 O 9 , Bi 3 TiNbO 9 , PbBi,Nb,O 9 , Pb 075 ,Bi 2 , 5 Ti 025 Nb, 75 O 9 , Pb 05 Bi, 5 Ti 0 5 Nb, 5 O 9 , Pb 025 Bi 2 75 Ti 0 75 Nb, 25 O 9 , Bi 3 TiNbO 9 , PbBi 4 Ti 4 O, 5 , Pb 075 Bi 425 Ti 375 Gao 25 O, 5 , Pb 05 Bi 4 5 Ti 3 5 Gao 5 O l5 , and Bi 5 Ti 3 GaO 15 . Although it is desirable, in order to minimize processing steps, to use only one etchant and only etch step it is possible to perform the method of the invention using multiple etchants or multiple etch steps. As in the previous embodiment the foundation 70 is removed using conventional methods, see Figure 9. The structure 100 of the invention remains. In this case the structure 100 is a storage cell capacitor formed using a single etch process performed in an argon plasma environment at radio frequencies using an Ion Mill etcher as an RF ion source wherein the angle of incidence is 90 degrees. Variations of this etch, including etchants and angle of incidence, may be used as long as the desired sidewall deposition occurs during the etch. In still a further embodiment, as shown in Figures 10 and 1 1 , two conductive layers 105 and 1 10, interposed with a deposited dielectric layer 115, are deposited to overlie a substrate 120. A conductive plug 125 is fabricated by conventional means to overlie conductive layer 105. A polysilicon plug is one preferred choice for the conductive plug 125 however the conductive plug 125 may be of a material selected from the group consisting of TiPt, TiNPt, TiAlN-Pt, Ru, RuO 2 , RuPt, RuO,Pt, W, WPt, WSi, Ti, TiSi, Ta, TaN, TaSi, doped and undoped Poly Si, Al, Pd and Ir. Other conductive materials may be used as well. Figure 1 1 shows the redeposition of the conductive layers 105 and 1 10 and the redeposition of dielectric layer 115 following an etch of the layers 105, 1 10, and 1 15. A storage node capacitor 130 is formed during the redeposition. The storage node capacitor 130 has conductive layer 1 10 as a storage node electrode and has conductive layer 105 and conductive plug 125 as a cell plate electrode. In an alternate embodiment the deposition of conductive layer 105 may be eliminated. The storage node electrode thus formed has conductive layer 1 10 as the storage node electrode and has the conductive plug 125 as the cell plate electrode, see Figure 12. Figure 13 is a copy of a photograph taken with a scanning electron microscope showing an isometric view of a structure of the invention, and Figure 14 is a copy of a photograph taken with a scanning electron microscope showing a cross-sectional view of a structure of the invention. While the invention has been described in its preferred embodiments it is to be understood that the words which have been used are words of description rather than limitation and that changes may be made within the purview of the appended claims without departing from the true scope and spirit of the invention in its broader aspects.

Claims: WHAT IS CLAIMED IS: 1. A method for fabricating a semiconductor structure, comprising the following steps: a) masking a first layer of material with a patterned second layer; and b) etching the first layer of material in a manner sufficient to cause the first layer to deposit on a portion of the patterned second layer. 2. The method as specified in Claim 1, further comprising the step of bombarding, during said step of etching, the first layer with etchant ions at an angle sufficient to cause the first layer to deposit on the portion of the patterned second layer. 3. The method as specified in Claim 1 , further comprising initially depositing said first layer overlying a substrate. 4. A method for fabricating a semiconductor structure on a semiconductor device comprising multiple layers of material, comprising the following steps: a) forming a first layer of material; b) forming a patterned second layer overlying the first layer; and c) depositing portions of the first layer on a portion of the patterned second layer, wherein at least the portions deposited form the semiconductor structure. 5. The method as specified in claim 4, further comprising the step of: etching the first layer to remove portions thereof. 6. The method as specified in Claims 4 or 5, further comprising the step of removing the patterned second layer, the portions of the first layer deposited on the patterned second layer and a portion of the first layer initially underlying the patterned second layer forming the semiconductor structure. 7. The method as specified in Claim 4, further comprising the following steps: a) removing the patterned second layer; b) forming a dielectric layer overlying the semiconductor structure; and c) forming a conductive layer overlying the dielectric layer thereby creating a capacitor having electrodes comprising the conductive layer and the semiconductor structure. 8. The method as specified in Claim 4, further comprising the step of oxidizing the semiconductor structure. 9. A method for forming a semiconductor structure comprising the following steps: a) forming a plurality of layers overlying a substrate; b) masking the plurality of layers with a patterned layer; c) etching the plurality of layers thereby creating etched particles; and d) depositing the etched particles to form a further plurality of layers on a sidewall of the patterned layer, at least said further plurality of layers and the plurality of layers overlying the substrate following the step of etching forming the semiconductor structure. 10. The method as specified in Claim 9, further comprising the step of removing the patterned layer. 11. A method for forming a capacitor comprising the following steps: a) forming a conductive layer overlying a substrate; b) forming a dielectric layer overlying the conductive layer; c) masking the dielectric layer with a patterned layer; 9 d) etching the dielectric layer to create portions of the dielectric layer having a same chemical composition as the dielectric layer; e) depositing the portions of the dielectric layer on a portion of the patterned layer; f) etching the conductive layer to create portions of the conductive layer having a same chemical composition as the conductive layer; and g) depositing the portions of the conductive layer on the deposited portions of the dielectric layer, wherein the conductive particles which were deposited and the conductive layer remaining after the step of etching the conductive layer form at least a portion of an electrode of the capacitor. 12. The method as specified in Claim 1 1, wherein said patterned layer is conductive and forms at least a portion of a further electrode of the capacitor. 13. The method as specified in Claim 1 1, further comprising a) removing the patterned layer; and b) depositing a further conductive layer overlying the dielectric layer, said further conductive layer forming a further electrode of the capacitor. 14. A method for forming a capacitor comprising the following steps: a) forming a first conductive layer overlying a substrate; b) forming a dielectric layer overlying the first conductive layer; c) forming a second conductive layer overlying the dielectric layer; d) masking the second conductive layer with a patterned layer; e) etching the second conductive layer to create portions of the first conductive layer having a same chemical composition as does the second conductive layer; f) depositing the portions of the first conductive layer on a portion of the patterned layer; g) etching the dielectric layer to create portions of the dielectric layer having a same chemical composition as the dielectric layer; h) depositing the portions of the dielectric layer on the portions of the first conductive layer; i) etching the first conductive layer to create portions of the second conductive layer having a same chemical composition as the first conductive layer; and j) depositing the portions of the second conductive layer on the portions of the dielectric layer, wherein the first portions of the first conductive layer form at least a portion of a first electrode of the capacitor and wherein the portions of the second conductive layer form at least a portion of a second electrode of the capacitor. 15. The method as specified in Claim 14, further comprising the step of performing said steps of etching (e, g, and i) and said steps of depositing insitu in one etch step.

Inventors: MCCLURE BRENT A, NEW DARYL C, MCCLURE, BRENT, A., NEW, DARYL, C.
Applicants: MICRON TECHNOLOGY INC, MICRON TECHNOLOGY, INC.
Application year: 1996
Main classification: H01L21
IPC codes: H01L21, H01L27