METHOD FOR ETCHING SILICON OXYNITRIDE AND INORGANIC ANTIREFLECTION COATINGS

Abstract: The present disclosure pertains to a method for plasma etching a semiconductor patterning stack (100). The patterning stack includes at least one layer comprising either a dielectric-comprising antireflective material (120) or an oxygen-comprising material (120). In many instances the dielectric-comprising antireflective material (120) will be an oxygen-comprising material, but it need not be limited to such materials. In one preferred embodiment of the method, the chemistry enables the plasma etching of both a layer of the dielectric-comprising antireflective material (120) or oxygen-comprising material and an adjacent or underlying layer (118) of material. In another preferred embodiment of the method, the layer of dielectric-comprising antireflective material (120) or oxygen-comprising material is etched using one chemistry, while the adjacent or underlying layer (118) is etched using another chemistry, but in the same process chamber. Of particular interest is silicon oxynitride, an oxygen-comprising material which functions as an antireflective material. A preferred embodiment of the method provides for the use of a source of carbon and an appropriate halogen-comprising plasma, to achieve selective etch of one oxygen-containing material compared with another material which contains a more limited amount of oxygen.

Description: METHOD FOR ETCHING SILICON OXYNITRIDE AND INORGANIC ANTIREFLECTION COATINGS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to a method of etching silicon oxynitride and other oxygen containing materials. In addition, the method is applicable to inorganic antireflective coaling (ARC) materials. Silicon oxynitride is commonly used as an antireflective coating in combination with deep ultraviolet (DUV) photoresists. 2. Brief Description of the Background Art In the field of semiconductor device fabrication, DUV photoresists have been developed which lake advantage of shorter wavelengths of ultraviolet radiation to enable Hie patterning of smaller-dimensioned electronic and optical devices than possible with tradilional, or so called I-line photoresists.. Generally, the photoresist is applied over a slack of layers of various materials to be patterned in subsequent processing steps. Some of the layers in the stack are consumed during the process of patterning underlying layers which become part of the functioning device. To take advantage of the spacial resolution of the photoresist, it is necessary to use an antireflective coating (ARC) layer underlying the photoresist, to suppress reflection off other layers in the stack during photoresist exposure. Thus, the ARC layer enables patterning of the photoresist to provide an accurate pattern replication. Though the most commonly used ARC material is titanium nitride, a number of other materials have been suggested for use in combination with DUV photoresists. For example, U. S. Patent No. 5,441,914 issued August 15, 1995 to Taft el al. describes the use of a silicon nitride anti-reflective layer, while U. S. Patent No. 5,525,542, issued June 1 1 , 1996 to Maniar et al. discloses the use of an aluminum nitride anti-rcflcctivc layer. U. S. Patent No. 5,539,249 of Roman el al., issued July 23, 1996, describes the use of an antireflective layer of silicon-rich silicon nitride. U. S. Patent No. 5,635,338 lo Joshi el al., issued June 3, 1997, describes a class of silicon-containing materials which display particular sensitivity in the unlraviolcl and deep ultraviolet for the formation of patterns by radiation induced conversion into glassy compounds. Joshi el al. recommend the use of anti-reflective coatings such as amorphous silicon and an organic plasma polymerized anli-rcfleclivc coaling generated from cyclohcptatricnc. U. S. Patent No. 5,633,210 to Yang el al., issued May 27, 1997 discloses the use of an anti-rcflcclivc coating material selected from titanium nitride materials, silicon oxide materials, and silicon oxynitride materials. Recently there has been increased interest in the use of silicon oxynitride as an anti-rcfleclivc coaling, due to its ability lo function well in combination with DUV photoresist. Silicon oxynitride typically (but not by way of limitation) has a formula of SiO x N y I I t , where x ranges from 0 lo about 2, y ranges from 0 to about 1, and z ranges from 0 lo about 1. By changing the composition of the silicon oxynitride ARC layer, one can control reflection onto the photoresist during imaging of the photoresist layer. When SiO x N y I \. is used as an ARC, x, y, and z typically range between about 0.2 and about 0.5. Silicon oxynitride as an ARC enables efficient suppression of the reflection from underlying layers while providing superior chemical properties which prevent an undesirable effect in photoresist pallcrning known as photoresist poisoning. Photoresist poisoning refers lo reaction of the surface underlying the photoresist with moisture to form amino basic groups (NH 2 - ) which react with the phologcncralcd acid which is responsible for Ihc photoresist development. Deactivation of the acid by Ihc amino groups is believed lo be responsible for formation of the "fool" (widening of the photoresist line just above the substrate) on some ARC materials such as titanium nitride. The present invention addresses details of the application of dry etch SUBSTTTUTE SHEET (RULE 26) techniques for pattern transfer into a silicon oxynitride layer. However, the concepts developed for dry etch of a silicon oxynilridc layer have application lo the dry etch of oilier oxygen containing subslralcs. With reference lo a silicon oxynilridc layer used as a anli-rcfleclivc coaling, in such an application, a typical slack of materials for pattern transfer would include: A subslrale, which is a dielectric layer used lo separate a metal interconnect layer (lo be patterned on plasma etching of the clch stack) from underlying device layers. A barrier layer, which prevents Ihc diffusion of material between a conductive layer and the substrate. A conductive layer, which is typically aluminum or an alloy thereof. Λn anli-rcflcctivc-coaling (ARC) layer thai reduces rcfleclion back inlo the photoresist during its exposure in the lithography slcp and allows for bcllcr pattern reproduction. And, a photoresist layer which is imaged lo provide the pallcrn for transfer lo underlying layers. ll would, then, be desirable lo have a dry, plasma-based clch process for Iransfcr of Ihc pallcrn from Ihc developed photoresist llirough all of the layers within the complete clch slack, including an ARC layer, a conductive layer, and a barrier layer. Etching of a mclal-comprising slack is traditionally achieved in a mclal clch chamber using clch slacks with ARC layers such as titanium nitride. However, as silicon oxynilridc is a dielectric material, ils patterning is traditionally reserved for dielectric clch chambers, and moving Ihc substrate from one process chamber lo another, lowers the productivity of the whole process. The present invention details a method permitting the clch of a dielectric comprising ARC layer sucli as a silicon-oxynitridc ARC in the same chamber as is used for etching Ihc rcsl of Ihc mclal-comprising slack. We have developed a plasma clch process which provides adequate selectivity for a silicon oxynitride ARC layer over organic-based photoresists. In addition, we have obtained a good etch rale for a silicon oxynilridc ARC layer while providing excellent pallcrn transfer llirough Ihc ARC layer and other layers of a six layer mclal-comprising slack. SUMMARY OF THE INVENTION The present invention perlains lo a method for plasma etching a semiconductor patterning slack. The patterning slack includes at least one layer comprising either a dielectric-comprising antireflective material or an oxygen-comprising material. In many instances the diclcclric-comprising anlireflcclive material will be an oxygen- comprising material, but it need not be limited to such materials. In one preferred embodiment of the method, the chemistry enables the plasma etching of both a layer of Ihc diclcclric-comprising anlireflcclive material or oxygen-comprising material and an adjacent or underlying layer of material. In another preferred embodiment of the method, the layer of dielectric-comprising antireflective material or oxygen-comprising material is etched using one chemistry, while the adjacent or underlying layer is etched using another chemistry, but in the same process chamber. Of particular interest is silicon oxynilridc, an oxygen-comprising material which functions as an anlirefleclivc material. A preferred embodiment of the method provides for the use of a source of carbon and an appropriate halogen-comprising plasma, lo achieve selective etch of one oxygcn-conlaining material compared with another material which contains a more limited amount of oxygen. In a highly preferred embodiment of the invention, a film of silicon oxynilridc is plasma etched, and bcllcr selectivity is achieved relative lo a film of a lower oxygen content material, such as a photoresist, by using fluorine comprising plasma. Preferably the fluorine comprising plasma also comprises a source of carbon. Example of materials which provide both fluorine and carbon include fluorocarbons such as CIIF j , CF 4 , CF 3 C1, C Z F 4 , C 2 F 6 and combinations thereof. The fluorocarbons may be combined with other gases which increase the halogen content of the plasma, such as Clj , I ' j , I IF, I ICI, NI ' ., or SF β , for example, but not by way of limitation. The addition of such other gases is helpful in increasing the clch rale, and in some instances the selectivity, of the silicon oxynilridc. When Ihc gas used lo increase the halogen conlcnl comprises a halogen oilier than fluorine, such as chlorine, the clch rale of some olhcr slack layer materials such as a TiN x barrier layer is also increased. The addition of chlorine lo a fluorocarbon plasma should enhance clch of such a barrier layer material along wilh Ihc silicon oxynilridc, while the clch of an oxygen- poor material such as a photoresist is suppressed. We have discovered a preferred combination of plasma clch gases which provides an unexpectedly high etch rale while providing selectivity for silicon oxynilridc over patterning photoresist. The preferred combination of plasma clch gases is O IF- and CI 2 , wherein the gas flow ratio of CIIF j lo Cl 2 ranges between about 2 : 1 and aboul 1 : 3, wherein a ralio of about 2 : 1 is recommended for high silicon oxynilridc lo photoresist selectivity, and a higher chlorine conlcnl is recommended for etching bolh Ihc layer of silicon oxynilridc and an underlying layer containing a metal or a refractory mclal such as lilanium nitride. It is expected thai Ihc use of CF 4 rather than G IF, would require less Cl 2 to selectively clch silicon oxynilridc and thai CF 4 alone might be sufficient. Further, since the silicon clch rale is dependent on fluorine ralhcr lhan chlorine, Ihc use of CF 4 should increase Ihc clch rale of silicon oxynilridc and may provide an improvement in selectivity as compared wilh CI IF, . BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a schematic of the cross-scclional view the preferred embodiment metal clch slack incorporating silicon oxynilridc as the ARC layer. Figures 2Λ - 2D illustrate ihc Example One slack cross-scclional view schematic as the clch slack shown in Figure I progresses llirough a llircc step clch process. Figures 3Λ - 3C illustrate the Example Two slack cross-sectional view schematic as the clch slack shown in Figure 1 progresses llirough a two step clch process, including one step for etching the silicon oxynilridc and titanium nitride layers and a second mclal clch slcp for etching the three layers as described wilh reference to figure 2C. Figure 4 shows a plasma processing apparatus of the kind used in carrying oul Ihc etching processes described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method is disclosed for the selective etching of silicon oxynitride and other oxygen-comprising layers on a mullilaycred subslralc. The method provides for the selective etching of such oxygen-comprising substrates in a halocarbon-comprising clch plasma, and particularly in a fluorocarbon-comprising clch plasma. Finally, an especially preferred embodiment for the selective etching of silicon oxynitride is described. Polymer films derived from carbon and halogens which arc present in an clch plasma have been observed lo deposit on the surfaces of silicon and silicon oxide during clch processing, sec for example, S. Λrai el al., Japanese J. of Appl. Phys., Part 1 , V. 31 , 201 1-2019 (1992). We wanlcd lo use silicon oxynilridc as an anti-rcflcclivc coaling in a multi- layered clch structure for the plasma etching of an aluminum conductive layer. To clch Ihc silicon oxynilridc wc used a fluorocarbon-comprising plasma. Although we were not certain thai polymer films were depositing on substrate surfaces during the etching of the silicon oxynilridc, wc suspected this might be the case. During development of Ihc etching process, wc discovered that wc could adjust the selectivity of Ihc clch for silicon oxynilridc compared lo the photoresist used to pattern the multi- layered clch structure (slack) by adjusting the atomic ratio of fluorine lo carbon in the gases supplied lo Ihc process chamber. Il appears that Ihc selectivity of silicon oxynilridc clch is improved through the formation of a fluorine-comprising polymer. Wc believe that while Ihc polymer builds up on the surfaces of non-oxygenated materials, slowing down etching on these surfaces, on the surface of silicon oxynilridc, the following reaction lakes place: (-CF n -) w (s) + SiO x N y π, (s) → (-CF n -) w ., (s) + CO and/or CO 2 (g) + SiF, (g) + (NII/N 2 /II 2 O/II 2 /MX/X 2 . . .) (g), where (-CF n -) w is the polymer layer. This reaction results in consumption of the polymer simultaneously wilh etching of silicon oxynilridc, while producing highly volatile byproducts. These byproducts arc later removed as exhaust wilh Ihc help of a vacuum pump. To maximize the selectivity of the clch, Ihc proper balance of carbon and fluorine in the plasma is achieved by adjusting the flow rales of gases injected into the clch processing chamber. Such adjustment is usually made by selecting from Ihc following oplions: Choosing Ihc primary gas feed with a particular carbon lo fluorine atomic ratio, where Ihc ratio may be adjusted by selection from gases such as CIIFj, CF , C 2 F 4 , C 2 F 6 or a combination thereof; adding oxygen or another oxidizing agent which binds wilh carbon in Ihc plasma lo suppress the formation of polymer; and adding a gas which serves as a source of carbon, such as CO, when il is desired lo increase Ihc polymer formation. It should be mentioned thai if photoresist is present in Ihc clch chamber, ils erosion during Ihc plasma etching process produces considerable amounts of carbon, and Ihc composition of Ihc gas feed has lo be adjusted in conjunction wilh Ihc pallcrn density of the photoresist and possible with the kind of photoresist. Wc have achieved a surprising increase in the elch rale of silicon oxynilridc by adding an assisting halogen-comprising gas such as Cl 2 , F 2 , IIF, HC1, or SF 6 (preferably CI 2 and SF 6 ) lo the fluorocarbon-comprising plasma feed gases. This list of gases can be extended to include other gases which serve as a source of halogen atoms in Ihc plasma. The benefits of using such an assisting gas arc twofold. If etching of silicon oxynilridc is carried out in a metal clch chamber, and this is desirable when the silicon oxynitride is used as an ARC layer in a metal slack, such halogen-containing gases are likely lo be connected lo the clch system for the purpose of mclal etch. Also, Ihc addition of a halogen other than fluorine appears to provide additional flexibility in controlling the clch rates of other materials exposed lo Ihc plasma. For example, the etching of a titanium nitride barrier layer is belter using chlorine than fluorine, and Ihc addition of chlorine to a fluorocarbon-comprising plasma enlianccs Ihc etching of this material simultaneously with the etching of silicon oxynilridc, while Ihc etching of an adjacent photoresist is suppressed due lo the presence of polymer or halocarbon species on its surface. We have discovered a preferred combination of plasma clch gases which provides an unexpectedly high clch rale while providing selectivity for silicon oxynilridc over patterning photoresist. The preferred combination of plasma etch gases is CHF 3 and CI 2 , wherein the gas flow ralio of CIIF 3 lo Cl 2 ranges between about 2 : 1 and about 1 : 3, wherein a ralio of about 2 : 1 is recommended for high silicon oxynilridc lo photoresist selectivity, and a higher chlorine content is recommended for simultaneous etching of silicon oxynilridc and a barrier layer such as titanium nitride. It is expected that Ihc use of CF 4 rather than CHF 3 would require less Cl 2 lo selectively etch silicon oxynitride and thai CF 4 alone is likely lo be sufficient. Further, since the silicon elch rale is dependent on fluorine rather than chlorine, Ihc use of CF 4 should increase the clch rate of silicon oxynilridc and may provide an improvement in selectivity as compared wilh CIIF 3 . In view of ihc successful etching of silicon oxynilridc, wc believe that in a halocarbon-bascd clch plasma il is possible lo improve the selectivity of oxygen- comprising layers over adjacent layers which contain substantially less oxygen or no oxygen, using Ihc method described above and expanded upon below. In particular, a carbon source and an appropriale halogen-comprising plasma can be used lo achieve selective etching of an oxygen-comprising material compared wilh a material which contains no oxygen or a substantially reduced amount of oxygen. Wc believe thai Ihc following reaction would take place between an oxygen-rich subslralc and a polymer film or halocarbon-comprising species on its surface. (-CX„-) y (s) -i- RO m (s) - (-CX n -) y ., (s) + CO and/or CO 2 (g) + wX k (g), where (-CX n -) y is Ihc polymer layer or halogen-comprising species; X is a halogen, such as F, Cl, Br, or I; RO m is an oxygen containing material, such as SiO x N y I I,, SiO 2 , or TiO,N y ; wX k is Ihc halogcnalcd clch byproducl, such as SiF 4 , TiF , or TiCl 4 ; and (s) and (g) represent a solid and a gas, respectively. The overall outcome of this reaction is that part of the polymer (or halocarbon- comprising species) reads wilh Ihc subslralc material lo form gaseous products that can be subsequently removed from the plasma process chamber wilh Ihc exhaust gases. Thus, an oxygen-comprising material is etched while the etching of a material which docs not contain oxygen is hindered. By choosing the appropriale halogen so thai Ihc halogcnalcd byproducts have Ihc highest possible vapor pressure, Ihc best results can be achieved. I. DEFINITIONS As a preface to ihc detailed description, il should be noted thai, as used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents, unless ihc conlcxl clearly dictates otherwise. Thus, for example, the term "a semiconductor" includes a variety of different materials which arc .known lo have Ihc behavioral characteristics of a semiconductor, reference to "a conductive material" includes mclals such aluminum, copper, platinum, iridium, rubidium, and combinations and alloys thereof, as well as other conductive materials which would be suitable in the application described. Specific terminology of particular importance to the description of the present invention is defined below. The lcrm "aluminum" includes alloys of aluminum of the kind typically used in the semiconductor industry. Such alloys include aluminum-copper alloys, and aluminum-coppcr-silicon alloys, for example. Typically such alloys of aluminum comprise about 0.5 % copper. In addition, as is known in the art, aluminum typically exhibits a surface layer of aluminum oxide. The term "anlireflcclive coaling", "anlireflcclive layer" or "ARC" includes materials which arc applied lo a surface lo reduce ils rcfleclion of electromagnetic radiation. The term "decoupled plasma source" or "DPS" as used herein refers lo a plasma clch apparatus wilh separate controls for Ihc inductive coupling of RF power which controls plasma density (source power) and. the bias power which controls ion bombardment energy of the subslralc surface. The lcrm "dielectric ARC" or "diclcclric-comprising ARC" refers lo an ARC which comprises a dielectric material. The lcr 'Tcalurc" refers lo mclal lines, trenches and openings in a dielectric layer, and other structures which make up the topography of the subslralc surface. Feature size often refers lo Ihc size of the smallest feature on the wafer. The lcrm "ion bombardment" refers lo the collision of ions wilh a surface. The ions arc accelerated toward Ihc surface by electric fields in the vicinily of the surface exposed lo a plasma. The lcrm "plasma" refers lo a partially ionized gas containing an approximately equal number of posilivc and negative charges, as well as some other number of non- ionized gas species. The term "selectivity" is used lo refer lo a) a ralio of clch rales of two materials; and b) a condition achieved during elch when elch rale of one material is increased in comparison wilh another material. Nole that there are various kinds of materials included in a slack of layers used in an etching process. The lcrm "source power" refers lo the power lhal is responsible for sustaining Ihc plasma by providing a major portion of the energy lo ionize the neutral species in the chamber. The lcrm "slack" or "clch slack" refers lo a collection of layers of different materials deposited one over Ihc other, al least a portion of which are etched during an etching process. A "metal slack" refers lo a "slack" which, upon completion of a mclal clch process becomes a mclal-comprising fealurc on a subslralc. The lcrm "subslralc" includes semiconductor materials, glass, ceramics, polymeric materials, and other materials of use in the semiconductor industry. The lerm "vertical profile" refers lo a feature profile wherein a cross-section of the feature exhibits side walls which are perpendicular to the surface on which the feature stands. Alternatively, a "posilivc profile" is one wherein the width of the cross-section of Ihc feature is larger at Ihc surface on which the feature stands than al a distance away from Ihc surface. II. AN APPARATUS FOR PRACTICING THE INVENTION The preferred embodiment etch processes described herein were carried out in a Centura® Integrated Processing System available from Applied Materials, Inc. of Sanla Clara, California. The system is shown and described in United Slates Patent No. 5,186,718, the disclosure of which is hereby incorporated by reference. This equipment included a Decoupled Plasma Source (DPS) of the kind described by Yan Ye cl al. al the Proceedings of Ihc Eleventh International Symposium of Plasma Processing, May 7, 1996 and as published in the Electrochemical Society Proceedings, Volume 96-12, pp. 222 - 233 (1996). The plasma processing chamber enables the processing of an 8 inch (200 mm) diameter silicon wafer. A schematic of the processing chamber is shown in Figure 4 which shows an clching process chamber 10, which is constructed lo include at least one inductive coil antenna segment 412 positioned exterior lo the clch process chamber 410 and connected lo a radio frequency (RF) power generator 418 (source power generator wilh a frequency tunable around 2 MHz for impedance matching at different plasma conditions). Interior lo Ihc process chamber is a subslralc 414 support pedestal (cathode) 416 which is connected lo an RF frequency power generator 422 (bias power generator of frequency fixed at 13.56 MHz) through an impedance matching network 424, and a conductive chamber wall 430 which serves as the electrical ground 434. The semiconductor subslralc 414 is placed on the support pedestal 416 and gaseous components arc fed into the process chamber through entry ports 426. A plasma is ignited in process chamber 410 by applying RF powers 418 and 422. Pressure interior to the clch process chamber 410 is controlled using a vacuum pump (not shown) and a throttle valve 427 situated between process chamber 410 and the vacuum pump. The temperature on the surface of the clch chamber walls is controlled using liquid-containing conduits (not shown) which are located in the walls of Ihc clch chamber 410. The temperature of the semiconductor subslralc is controlled by stabilizing the temperature of the support pedestal and flowing helium gas in Ihc channels formed by the back of the substrate and grooves (not shown) on the pedestal 416 surface. The helium gas is used lo facilitate heal transfer between Ihc subslralc and Ihc pedestal. During the clch process, Ihc subslralc surface is gradually healed by Ihc plasma lo a steady slate temperature which is approximately 25 - 40 °C higher lhan the subslralc support plalen temperature, depending on Ihc process conditions. Il is estimated lhal Ihc subslralc surface temperature was typically around 75 °C during mosl of our experiments. The surface of the etching chamber 410 walls was maintained al about 80 °C using Ihc cooling conduils previously described. III. EXAMPLES OF ETCHING SILICON OXYNITRIDE Three sets of experiments were performed. First, the basic effect of elch chemistry was evaluated by clching unpallcrncd silicon oxynilridc and unpallcrncd I- Iinc pholorcsisl wafers and the clch rales were compared lo estimate the selectivity. (The pholorcsisl and silicon oxynilridc were not simultaneously present in the plasma.) CHF 3 , CI 2 , SF 6 , BC1 3 and combinations thereof were evaluated in this testing. The elch rales obtained arc provided in Table 1 below. The elch condilions were as follows. The plasma source power was 1400 W; Ihc bias power was 130 W; Ihc process chamber pressure was 13 mTorr; the substrate support plalen temperature was 45 °C; Ihc support plalen back side helium pressure was 10 Torr, wilh a typical leak of 3 - 6 seem, and clching was carried oul for 40 seconds. This experimentation indicated lhal CI IF 3 and Cl 2 used together provided the most promising combination of selectivity and clch rale. 13 Table I: Uiipnllcriicd SiO,N y and Photoresist Etch Rates and Selectivity As Λ Function of Etch Gas Feed Composition where: ER is clch rale; PR is pholorcsisl; and Select is selectivity. In the second set of experiments, wc pallcrn etched a silicon oxynilridc layer of aboul 3500 A in thickness which had been applied over a silicon dioxide surface. The pallcrn was lines and spaces having a feature size down lo aboul 0.25 μm which was transferred from a patterned layer of DUV photoresist (Shipley UV-5 of aboul 6500 - 7000 A in thickness). The subslralc was then examined wilh a scanning electron microscope lo dclcrmine ihc pallcrn profile and lo estimate the clch rales and selectivity. The details arc provided in Tables II and III. Il was discovered lhal, due lo Ihc increased amount of carbon released into the plasma from Ihc pholorcsisl surface, silicon oxyniliidc could not be clchcd in pure CIIF 3 under the process condilions used (basically Ihc same condilions as described above for Ihc initial experimentation). The clch rale had dropped by a factor of aboul three in the area of the subslralc al a distance away from Ihc pholorcsisl lines (open area) and by a factor of about len in between the lines, as compared lo Ihc clch rale of unpallcrncd silicon oxynilridc. This situation was subsequently amended by adding Cl 2 lo the plasma gas feed. In particular, Ihc Cl 2 added made up from aboul 33% lo aboul 75 % of the total volumetric gas flow. 14 Table II: Process Conditions For The Pattern Etch Of Silicon oxynitride. Λ posilivc profile is one in which a line is wider at lite bollom Ihatt al the lop, so lhal Ihc included angle at the base or Ihc line is greater than Ihc desired 90". Helium backside pressure was 10 Torr throughout all trial runs. Table HI: Etch Kate And Selectivity Of Pattern Etching Silicon oxynitride. (Substrate numbers correspond wilh the ones given in Table II) itc rale n t e open area. ** Ralio of Ihe open area clch rale to Ihc pholorcsisl loss rale at Ihc top in a 0.25μm / 0.25 μm (line/space) line array. In Ihc third set of experiments, a full metal stack upon a silicon wafer subslralc, which included an aluminum metal layer and titanium nitride barrier layers was etched. The profiles were examined wilh the help of a scanning electron microscope. The details for the third set of experiments are given in the EXAMPLES provided below. Figure 1 illustrates a typical preferred embodiment clch slack 100 for patterning an aluminum conductive layer to feature sizes down to 0.25 μm or less using a DUV pholorcsisl as a patterning means. In particular, Ihc substrate 1 10 is a layer of silicon dioxide overlying a silicon wafer surface (not shown). The barrier layer is a bilaycr composed of a 300 A thick layer of titanium 1 12, followed by a 500 Λ thick layer of titanium nitride 1 14. Overlying titanium nitride barrier layer 1 14 is a 5,200 A thick layer 1 16 of aluminum alloy containing 0.5 % copper. Overlying aluminum alloy layer 1 16 is a second 300 A thick layer of titanium 1 17, followed by a 500 Λ thick layer of titanium nitride 1 18.. Overlying second titanium nitride layer 1 18 is a layer of silicon oxynilridc 120 aboul 300 A thick. Overlying silicon oxynilridc layer 120 is a layer of patterned DUV photoresist 121, where the pallcrn is lines and spaces and where Ihc lines and spaces have a varying width 122 of aboul 0.2 μm and larger, and have a height and a height 124 of aboul 0.7 μm (7,000 Λ). In Ihc preferred embodiments described herein, the DUV photoresist was UV-5, manufactured by Shipley Company of Marlborough, Massachusetts. Wc also evaluated a DUV pholorcsisl manufactured by Shin-Eslu of Japan, which preformed in a similar manner. EXAMPLE ONE: This Example is for a Ihrcc step clch in which Ihc SiO x N y ARC layer is etched in Step 1 , Ihc underlying TiN and Ti barrier layers arc etched in Slcp 2, wilh the aluminum alloy layer, and underlying TiN and Ti barrier layers being etched in Slcp 3. Wilh reference lo Figures 2Λ through 2D, Figure 2A illustrates the schematic cross-scclional profile of the preferred embodiment slack 200 (the same stack as 100 described with reference to Figure 1) during Ihc tlirce etching steps. Figure 2D shows Ihc schematic of the cross-scclional profile of the etch slack aflcr the first clch slcp in which Ihc pallcrn is transferred from DUV photoresist layer 221 llirough silicon oxynilridc layer 220, slopping al the upper surface of second titanium nitride layer 218. The clch condilions used lo carry out this firsl clch step were as follows. The source power was 1400 W; the bias power was 100 W; the process chamber pressure was 12 niTorr; ihc subslralc support plalen temperature was aboul 45 °C; Ihc gas flow rates were 50 seem of CHF 3 / 25 seem of Cl 2 , and the wafer back side helium pressure was 12 Torr, with a typical leak of 3 - 6 seem. The clch lime period was 5 seconds. Figure 2C shows Ihc schematic of Ihc cross-scclional profile of the clch slack aflcr the second clch step in which the pattern is transferred llirough the second lilanium nitride layer 218 underlying silicon oxynilridc layer 220, slopping al the upper surface of aluminum layer 216. The clch condilions used lo carry oul this second clch slcp were the same as in Ihc first slcp except lhal Ihc bias power was 50 W, and Ihc gas tlow rales were 15 seem or CIIF 90 seem of Cl 2 . The clch lime period was 12 seconds. Figure 2D shows the schematic of the cross-scclional profile of Ihc slack aflcr Ihc third clch slcp in which Ihc pallcrn is transferred through the aluminum layer 1 16, Ihc first lilanium nitride barrier layer 214, and the first lilanium barrier layer 212, slopping wilh a slight over clch 226 into the lop of silicon dioxide layer 210. The clch condilions used lo carry oul this second clch slcp were as follows. The plasma source power was 1 100 W; the bias power was 130 W; Ihc process chamber pressure was 8 niTorr; Ihc subslralc support plalen lcmpcralurc was 45 °C, the gas flow rales were 5 seem oT CIIF-/ 80 seem of Cl 2 /40 seem of BC1 3 , and the wafer back side helium pressure was 12 Torr, wilh a typical leak of 3 - 6 seem. The clch was carried oul for as long as the end point signal al 396 urn (aluminum and lilanium lines) was above the background level plus another 10 seconds. EXAMPLE TWO: This Example is for a two slcp clch in which Ihc SiO x N y ARC layer and the underlying lilanium nitride and lilanium barrier layers, arc etched in Slcp I ; and, Ihc aluminum layer, and lilaniυm nitride and lilanium layers which underlie Ihc aluminum layer arc clchcd in Slcp 2. Wilh reference lo Figures 3A llirough 3C, Figure 3Λ illustrates the schematic cross-scclional profile of the preferred embodiment slack 300 (Ihc same stack as 100 described wilh reference lo Figure 1) for the two clch steps. Figure 313 shows Ihc schematic of Ihc cross-scclional profile of the clch slack aflcr the firsl clch step in which ihc pallcrn is transferred from DUV photoresist layer 321 llvrough silicon oxynilridc layer 320, second lilanium nilridc barrier layer 318, and second titanium layer 3 17, slopping al the upper surface of aluminum layer 316. The clch conditions used lo carry oul this first clch step were as follows. The source power was 1400 W; Ihe bias power was 70 W; Ihc process chamber pressure was 12 mTorr; Ihc subslralc support plalen temperature was 45 °C, the gas flow rales were 20 seem of GIF/ 60 seem of Cl 2 , and Ihe wafer back side helium pressure was 12 Torr, wilh a typical leak of aboul 3 - 6 seem. The clch time period was 20 seconds. The increased concentration of chlorine, as compared wilh Example 1, sacrifices the selectivity of silicon oxynilridc clch, thus allowing clching of oilier materials such as lilanium nilridc. Considering Ihc small thickness of the silicon oxynilridc layer, the overall loss of pholorcsisl thickness is negligible and is well justified by Ihe simplification in the clch process. Figure 3C shows the schematic of the cross-scclional profile of the slack after the second clch slcp in which Ihc pallcrn is Iransfcrrcd llirough aluminum layer 316, first lilanium nilridc layer 314 and firsl lilanium layer 312, slopping wilh a slight over clch 326 inlo silicon dioxide layer 310. The clch conditions used to carry out this second clch slcp were as follows. The plasma source power was 1000 W; Ihc bias power was 130 W; the process chamber pressure was 8 mTorr; Ihc subslralc support platen lcmpcralurc was 45 σ C, the gas volumetric flow rales were 5 seem of CIIF/ 80 seem of Cl/ 40 seem of I3C1 3 , and Ihc wafer back side helium pressure was 12 Torr, with a typical leak of 3 - 6 seem. The clch was carried oul for as long as the end poinl signal al 396 nm (aluminum and lilanium lines) was above Ihc background level plus another 10 seconds. The above described preferred embodiments arc not intended lo limit the scope of Ihc present invention, as one skilled in Ihc art can, in view of Ihe present disclosure expand such embodiments lo correspond wilh Ihc subjeel mailer of the invention claimed below.

Claims: CLAIMS Wc claim: 1. A method for plasma etching at lcasl one layer of a dielectric-comprising ARC material in a semiconductor pallcrning slack, Ihe method comprising: using at least one fluorine-comprising etchanl gas, alone or in combination wilh a chlorine- comprising clchanl gas, in a manner which provides selectivity for the ARC dielectric material. 2. The method of Claim 1 , wherein said fluorine-comprising gas and said chlorine comprising gas arc used in combination wilh a carbon-comprising gas. 3. The method of Claim I , wherein said fluorine-comprising gas further comprises carbon. 4. The method of Claim 1 , wherein bolh said dielectric-comprising ARC material and al lcasl one other layer which makes up said semiconductor patterning slack arc etched using the same clchanl gas or combination of clchanl gases. 5. The method of Claim 1 , wherein both said diclcclric-comprising ARC material and al lcasl one oilier layer which makes up said semiconductor pallcrning slack are etched in the same process chamber. 6. The method of Claim 5, wherein said process chamber includes an apparatus which enables independent control of a plasma density and of a source of bias power 21 which affects an ion bombardment energy upon a surface of said pallcrning slack. 7. A method for plasma clching al least one layer of an oxygen-comprising ARC material in a semiconductor pallcrning stack, the method comprising: using at least one fluorine-comprising clchanl gas, alone or in combination with a carbon- comprising gas, in a manner which provides selectivity for the oxygen-comprising material. 8. The method of Claim 7, wherein said fluorine-comprising gas further comprises carbon. 9. The method of Claim 7, wherein bolh said oxygen-comprising ARC material and al least one other layer which makes up said semiconductor pallcrning slack arc etched using the same clchanl gas or combination of clchanl gases. 10. The method of Claim 7, wherein bolh said oxygen-comprising ARC material and al lcasl one other layer which makes up said semiconductor pallcrning slack arc elchcd in ihc same process chamber. 1 1. The method of Claim 10, wherein said process chamber includes an apparatus which enables independent control of a plasma density and of a source of bias power which affects an ion bombardment energy upon a surface of said pallcrning slack. 12. Λ method for plasma etching an oxygen-comprising layer in a semiconductor plasma elch pallcrning slack, comprising: using al lcasl one halogen-comprising clchanl gas alone or in combination wilh other clchant gases, in a manner which provides selectivity for an exposed pallcrning slack layer containing a higher percentage of oxygen. 13. The method of Claim 12, wherein said halogen-comprising etchanl gas forms a halogen-comprising polymer or species which deposits on surfaces adjacent lo said oxygen-comprising layer in an amount sufficient to reduce the elch rate of said adjacent surfaces while permitting the etching of a surface of said oxygen comprising layer, and wherein said oxygen-comprising layer comprises at least three elements or comprises two elements where neither of Ihc two elements is silicon. 14. The method of Claim 12 or Claim 13, wherein said oxygen-comprising layer is silicon oxynitride. 15. The method of Claim 14, wherein said silicon oxynitride is SiO x N y H.., where x ranges from 0 lo aboul 2, y ranges from about 0 lo about 1 , and z ranges from 0 to aboul 1. 16. The method of Claim 15, wherein x, y, and z range between aboul 0.2 and about 0.5. 17. The method of Claim 13, wherein said oxygen-comprising layer includes silicon oxynilridc and said adjacent surface comprises a photoresist. 18. The method of Claim 17, wherein said photoresist is a DUV photoresist. 19. The method of Claim 12, or Claim 13, wherein said plasma clching is carried oul in an apparatus which enables independent control of a plasma density and of a source of bias power which affccls an ion bombardment energy of a subslralc surface. 23 20. The method of Claim 14, wherein said plasma clching is carried oul in an apparatus which enables independent control of a plasma density and of a source of bias power which affccls an ion bombardment energy of a substrate surface. 21. The method of Claim 19, wherein plasma-generated ions are directed toward a surface said oxygen-comprising layer in a manner which activates oxygen contained on said layer surface lo react wilh carbon adjacent lo or in contact wilh said surface. 22. The method of Claim 12, or Claim 13, wherein said halogen-comprising gas is a fluorine-comprising gas. 23. The method of Claim 22, wherein said fluorine-comprising gas is used in combination wilh a carbon-comprising gas. 24. The method of Claim 22, wherein said fluorine-comprising gas further comprises carbon. 25. The method of Claim 12 or Claim 13, wherein said halogen-comprising elch gas includes an assisting gas which is used lo improve the selectivity of said oxygen- comprising layer. 26. The method of Claim 25. wherein said assisting gas is selected from Ihc group consisting of Cl 2 , F 2 , I IF, IICT, NF 3 , SF 6 , and combinations thereof. 27. The method of Claim 24, wherein said fiuorine-comprising gas is selected from 24 Ihc group consisting of CI IF., CF 4 , CF-CI, C 2 F„, C 2 F 6 , and combinations thereof. 28. The method of Claim 27, wherein said fiuorine-comprising gas is CHF 3 , CF 4 , or a combination thereof. 29. The method of Claim 27, wherein said assisting gas is selected from the group consisting of Cl 2 , F 2 , 1 IF, IICI, NF 3 , SF 6 , and combinations thereof. 30. The mclhod of Claim 29, wherein said assisting gas is chlorine, and wherein volumetric flow rale of said fiuorine-comprising gas lo said chlorine ranges between about 2 : 1 and aboul I : 3. 31. A mclhod for plasma clching a silicon oxynilride-comprising layer in a semiconductor plasma clch pallcrning slack, comprising: using al least one halogen- comprising clchanl gas alone or in combination wilh other clchanl gases, wherein said halogen-comprising clchanl gas forms a halogen-comprising polymer or species which deposits on surfaces adjacent lo said silicon oxynilride-comprising layer in an amount sufficient lo reduce the clch rale of said adjacent surfaces while permitting the clching of a surface of said silicon oxynilride-comprising layer. 32. The mclhod of Claim 31 , wherein said surface adjacent said silicon oxynilride- comprising layer comprises a pholorcsisl. 33. The mclhod of Claim 32, wherein said pholorcsisl is a DUV pholorcsisl. 34. The mclhod of Claim 31 , or Claim 32, or Claim 33, wherein said plasma clching is carried out in an apparatus which enables independent control of a plasma density 25 and of a source of bias power which affects an ion bombardment energy of a subslralc surface. 35. The mclhod of Claim 31, or Claim 31 , or Claim 33, wherein said halogen- comprising gas is a fluorine-comprising gas. 36. The mclhod of Claim 35, wherein said fluorine-comprising gas is selected from the group consisting of CHF-, CF 4 , CF 3 C1, C 2 F 4 , C F 6 , and combinations thereof. 37. The mclhod of Claim 35, wherein said plasma elch gas includes an assisting gas selected from the group consisting of Cl 2 , F 2 , HF, HC1, NF 3 , SF 6 and combinations thereof, which is used to control the deposition of said fluorine-comprising polymer or species on said slack surface. 38. The mclhod of Claim 37, wherein said assisting gas is chlorine, and wherein volumetric flow rate of said fluorine-comprising gas lo said chlorine ranges between aboul 2 : 1 and aboul 1 : 3. 26

Inventors: IONOV PAVEL, KIM SUNG HO, LI DEAN, IONOV, PAVEL, KIM, SUNG, HO, LI, DEAN
Applicants: APPLIED MATERIALS INC, APPLIED MATERIALS, INC.
Application year: 1998
Main classification: H01L21
IPC codes: H01L21