Semiconductor processing methods of forming contact openings, methods of forming electrical connections and interconnections

[0002] This is a continuation of U.S. patent application Ser. No. 09/146,840, filed Sep. 3, 1998, and titled “Semiconductor Processing Methods of Forming Contact Openings, Methods of Forming Electrical Connections and Interconnections and Integrated Circuitry”, now U.S. Pat. No. 6,242,302, naming Charles H. Dennison as the inventor, the disclosure of which is hereby incorporated herein by reference.

[0003] This invention relates to semiconductor processing methods of forming contact openings, methods of forming electrical connections and interconnections, and integrated circuitry comprising such contact openings and electrical connections and interconnections.

[0004] Referring to FIGS. 1 and 2, a semiconductor wafer fragment is indicated generally at 10 and comprises a semiconductive substrate 12. In the context of this document, the term “semiconductive substrate” is defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above. Substrate 12 comprises a field oxide region 13 having an outer surface 14 (FIG. 2) over which a plurality of conductive runners or conductive lines 16, 18, and 20 are formed. The illustrated conductive lines or runners include conductive portions and insulative portions. Exemplary conductive portions are constituted, in this example, by a respective polysilicon layer 22 and an overlying silicide layer 24. The insulative portions of the runners or lines are constituted by respective overlying caps 26 and associated sidewall spacers 28. Exemplary materials for the insulative portions include oxides and nitrides.

[0005] An insulative layer 30 such as borophosphosilicate glass is formed over runners 16, 18, and 20 and a contact opening 32 is formed through a masked etch of layer 30 to outwardly expose a portion of silicide layer 24. Thereafter, conductive material such as conductively doped polysilicon is formed within contact opening 32 to provide a conductive contact 34 to conductive line 18. A metal layer 36 is provided thereover to form an electrical connection with conductive line 18.

[0006] A typical practice within the semiconductor industry is to provide a conductive line or runner with a widened landing pad in order to accommodate mask misalignments when contact openings are formed. An exemplary widened landing pad is shown in FIG. 1 at 38 and FIG. 2 by area A. By having a widened landing pad, contact opening 32 can shift left or right some distance relative to the position shown in FIGS. 1 and 2 without making undesirable contact with the substrate. For purposes of the ongoing discussion, landing pad 38 includes the conductive and insulative portions of conductive line 18; and the conductive portions of conductive line 18 define a contact pad with which electrical communication is desired. Accordingly, in the illustrated example a contact pad is defined by polysilicon layer 22 and silicide layer 24 of conductive line 18. The contact pad defines a target area A inside of which it is desirable to form a contact opening. An electrical connection through contact opening 32 can be formed anywhere within target area A and still effectively make a desirable connection with the conductive contact pad. Hence, the target area tolerates a contact opening mask misalignment on either side of the illustrated and desired contact opening 32. A tradeoff for improved mask misalignment tolerance is a reduction in wafer real estate available for supporting conductive lines and other integrated circuitry components. This is due largely in part to the increased area which is occupied by the widened landing pad 38. This also adversely impacts the conductive line spacing such that desired minimum spacing adjacent conductive lines is not achieved. Hence, integrated circuitry cannot be packed as densely upon a wafer as is desirable when the widened landing pads are used.

[0007] This invention grew out of concerns associated with enhancing the efficiency with which wafer real estate is used to support integrated circuitry. This invention also grew out of concerns associated with improving the methods and structures through which contact is made relative to conductive lines.

[0008] Methods of forming contact openings, making electrical interconnections, and related integrated circuitry are described. Integrated circuitry formed through one or more of the inventive methodologies is also described. In one implementation, a conductive runner or line having a contact pad with which electrical communication is desired is formed over a substrate outer surface. A conductive plug is formed laterally proximate the contact pad and together therewith defines an effectively widened contact pad. Conductive material is formed within a contact opening which is received within insulative material over the effectively widened contact pad. In a preferred implementation, a pair of conductive plugs are formed on either side of the contact pad laterally proximate thereof. The conductive plug(s) can extend away from the substrate outer surface a distance which is greater or less than a conductive line height of a conductive line adjacent which the plug is formed. In the former instance and in accordance with one aspect, such plug(s) can include a portion which overlaps with the contact pad of the associated conductive line.

[0009] Preferred embodiments of the invention are described below with reference to the following accompanying drawings.

[0010] FIG. 1 is a top plan view of a prior art semiconductor wafer fragment and a plurality of conductive lines supported thereon.

[0011] FIG. 2 is a view which is taken along line 2—2 in FIG. 1 at a subsequent processing step.

[0012] FIG. 3 is a diagrammatic sectional view of a semiconductor wafer fragment at one processing step in accordance with one implementation of the invention.

[0013] FIG. 4 is a view of the FIG. 3 wafer fragment at another processing step.

[0014] FIG. 5 is a view of the FIG. 3 wafer fragment at another processing step.

[0015] FIG. 6 is a view of the FIG. 3 wafer fragment at another processing step.

[0016] FIG. 7 is a view which is similar to the FIG. 6 view, but which shows an alternate embodiment in accordance with another implementation of the invention.

[0017] FIG. 8 is a view of the FIG. 3 wafer fragment at another processing step.

[0018] FIGS. 9 and 10 are top plan views of semiconductor wafer fragments which have been processed in accordance with the inventive methodologies.

[0019] This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).

[0020] Referring to FIG. 3, like numerals from the above-described embodiment are utilized where appropriate, with differences being indicated by the suffix “a” or with different numerals. Accordingly, a plurality of conductive runners or lines 16a,18a,and 20aare formed over outer surface 14, and can be formed over oxide isolation regions 40. Exemplary isolation regions include shallow trench isolation regions or field oxide regions formed through LOCOS techniques. The conductive lines comprise respective outermost surfaces 44 portions of which define respective conductive line heights h outwardly of outer surface 14. Diffusion regions 42 can be provided between the conductive lines, and preferably comprise n-type regions having doping concentrations of 1×10¹⁸cm⁻³. The diffusion regions can be provided in a separate doping step, or through outdiffusion of dopant from conductive material which will become more apparent below. An outer contact opening target area B is defined by conductive line 18a.

[0021] Referring to FIG. 4, an insulating material layer 46 is formed over substrate 12. An exemplary material is borophosphosilicate glass.

[0022] Referring to FIG. 5, at least one, and preferably a pair of contact openings 48, 50 are formed through layer 46 and preferably outwardly expose respective portions of outer surface 14. The contact openings can be formed through a suitable masked etch of layer 46. Preferably, the individual contact openings are essentially self-aligned at and to the substrate at two locations 48a,48b,and 50a,50brespectively, along a line extending laterally from conductive runner or line 18a.In a preferred implementation, one of the two locations for the individual contact openings is defined by conductive runner 18a.Even more preferably, the other of the two respective locations are defined by respective next adjacent conductive lines 16a,20a.

[0023] Referring to FIG. 6, and in accordance with a first implementation, first conductive material 52, 54 is formed within contact openings 48, 50, between the illustrated conductive lines and laterally proximate or adjacent the contact pad defined by conductive line 18a.An exemplary and preferred first conductive material is conductively doped polysilicon, which can serve as a source of outdiffused dopant for regions 42. The polysilicon can be chemical vapor deposited over the substrate and subsequently removed through conventional processing to provide conductive plugs 56, 58. Such conventional processing can include planarization processing to isolate conductive material within the respective contact openings, followed by a suitable timed etch to recess the conductive material within the contact openings. In the illustrated example, conductive plugs are formed on both sides of conductive line 18a.It is possible, however, for only one conductive plug to be formed on either side of conductive line 18a.The individual conductive plugs are essentially self-aligned at and to the substrate at the same locations as are the contact openings in which each is formed.

[0024] Referring still to FIG. 6, the illustrated conductive plugs are formed to preferably extend outwardly from outer surface 14 a distance which is greater than conductive runner height h. Because the plugs in this example are formed atop the same surface (outer surface 14) atop which the conductive lines are formed, each extends elevationally beyond the respective conductive line heights. Such plugs could, however, be formed to extend from outer surface 14 a distance which is less than or no further than the conductive runner height. This could, for example, be done by conducting a timed etch for a longer period of time than is suitable for forming the illustrated FIG. 6 plugs. An exemplary construction is shown in FIG. 7.

[0025] In one implementation, individual conductive plugs include portions which overlap with portions of conductive line 18aand the respective next adjacent conductive lines 16a,20a.In a preferred implementation, the respective plugs overlap with the outermost surfaces of the conductive lines adjacent which each is formed. Accordingly, portions of at least one, and preferably both conductive plugs can overlap target area B. Collectively, the conductive material of conductive plugs 56, 58, and the conductive material of conductive line 18adefine an effective contact pad having an outermost surface 60, which defines an effectively widened target area A′. The widened target area reduces the wafer area which was formerly required by the prior art widened landing pad (FIGS. 1 and 2) described above.

[0026] Alternately considered, effective contact pad outermost surface 60 defines a generally non-planar surface. In a preferred implementation, at least one of the conductive plugs, and preferably both, define a region of outermost surface 60 having a higher topographical elevation than the region defined by the contact pad of line 18a.

[0027] Referring to FIG. 8, a layer 62 of insulative material is formed over the substrate and the effective contact pad. A contact opening 64 is etched or otherwise formed through layer 62 to outwardly expose portions of the effective contact pad. Preferably, the contact pad of line 18ais exposed, with any mask misalignment resulting in exposure of conductive material of either or both of conductive plugs 56, 58. Subsequently, a second conductive material 66 is formed within contact opening 64 and in electrical communication with at least portions of the contact pad and, if exposed, an associated portion of a conductive plug. A bit line 68 can then be formed over the substrate and in electrical communication with material 66.

[0028] Referring to FIG. 9, conductive lines 16a,18aand 20ahave first respective line widths w₁at respective first locations and second line widths w₂at respective second locations, an exemplary second line width and location being shown for line 18a.The second line width corresponds to a line location where at least a portion of contact opening 64 is formed. In one implementation, the first and second line widths are essentially the same or equivalent. This is made possible because the above-described conductive plugs 56, 58 (shown in dashed lines in FIGS. 9 and 10) reduce, if not eliminate, the requirement of the FIG. 1 widened landing pad. The illustrated conductive plugs provide an effective contact pad width which is greater than second line width w₂, and include respective portions proximate the first line width w₁which overlap with or extend elevationally over the conductive portions, e.g. the contact pad, of line 18a.The plugs can also include portions which overlap with corresponding portions of conductive lines 16a,20a.This compensates for a contact opening mask misalignment by enabling desired contact to be made through a respective one of the conductive plugs as discussed above.

[0029] Referring to FIG. 10 and in accordance with another implementation, localized first and second line widths w₁, w₂respectively, are different with second line width w₂being greater than first line width w₁. In this example, the second line width defines a portion of a landing pad which is smaller in dimension than the FIG. 1 landing pad. Portions of conductive lines 16band 20blaterally proximate respective conductive plugs 56, 58 can be tapered or otherwise configured to accommodate the somewhat wider landing pad.

[0030] In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.