MULTILAYER INTERCONNECTION STRUCTURE FOR SEMICONDUCTOR DEVICE

Abstract: A multilayer interconnection structure for a semiconduc­ tor device has interconnection layers superposed on each other on the surface of a semiconductor substrate with an insulating layer interposed therebetween. Connection be­ tween the desired interconnection layers or between the desired interconnection layer and semiconductor substrate is effected by means of a contact hole formed in the respective insulating layers. Two upper and lower intercon­ nection layers intersect each other above the contact holes, and the contact hole (8a, 8b, 8c, 8d) does not overlap part of the traverse region of the upper interconnection layer (7) in the intersecting section.

Description: This invention relates to an improvement on a multilayer interconnection structure for a semiconductor device and more particularly to an improvement on a contact hole pattern of said semiconductor device. In recent years, noticeable progress has been achieved in the semiconductor-manufacturing technique, particularly in the technique of forming a multilayer interconnection structure for a semiconductor device, for example, not only a 2-ply or 3-ply type, but also a 4 or more ply type. An enlarged number of interconnection layers, however, leads to the difficulties that the step configuration on the surface of the semiconductor structure is increasingly complicated, giving rise to the deterioration of wiring characteristics and reduced reliability of wiring caused by, for example, breakage. It has hitherto been generally accepted and regarded as advantageous to enlarge as much as possible the contact hole used for connection between the desired interconnection layers. However, the enlargement of the contact hole is accompanied with the undermentioned drawbacks. Fig. 1 is a plan view of the conventional multilayer interconnection structure. Fig. 2 is a sectional view along line A-A of Fig. 1. As seen from Fig. 2, a first interconnection layer 2 consisting of an impurity region is formed in the surface portion of a semiconductor substrate 1. A first insulating layer 3 is deposited on said surface. A contact hole 4 is bored in that part of the first insulating layer 3 which contacts the surface of the first interconnection layer 2. A second interconnection layer 5 prepared from aluminium is formed on the surface of the first insulating layer 3. This second interconnection layer 5 is connected to the first interconnection layer 2 by means of the contact hole 4. To ensure connection between the first and second interconnection layers 2, 5, the contact hole 4 is relatively enlarged in that region where the first and second interconnection layers 2, 5 are superposed on each other, and extended along the second interconnection layer 5. A second insulating layer 6 is mounted on the first insulating layer 3 and second interconnection layer 5. A third interconnection layer 7 is laid on the second insulating layer 6. This third interconnection layer 7 crosses over the second interconnection layer 5 and passes over the contact hole 4. The conventional multilayer interconnection structure constructed as described above has the drawbacks that as seen from Fig. 2, a stepped portion of the second insulating layer 6 which is defined by the surface shape of the first insulating layer 3 above the contact hole 4 causes the third interconnection layer 7 to cover the second insulating layer 6 with less reliability. In other words, the third interconnection layer 7 is much thinner in the above-mentioned stepped portion of the second insulating layer 6. Consequently, the conventional multilayer interconnection structure has the drawbacks that the third interconnection layer 7 tends to disconnect in the aforesaid stepped portion of the second insulating layer 6; wiring characteristics are deteriorated by, for example, increased wiring resistance; and electro-migration arises particularly in the thinned portion of the third interconnection layer 7, resulting in a decline in the reliability of a multilayer interconnection structure for a semiconductor device. US-A-4 260 436 discloses a multilayer interconnection structure for a semiconductor device having upper and lower interconnection layers deposited on a first insulating layer with a second insulating layer interposed between the upper and lower interconnection layers. The second insulating layer has a step portion in its upper surface above a contact hole formed in the first insulating layer. The upper interconnection layer crosses the lower interconnection layer above the contact hole. It is accordingly an object of this invention to provide a novel multilayer interconnection structure for a semiconductor device which prevents an interconnection layer from being broken where it passes over a stepped portion formed above a contact hole and suppresses an increase in wiring resistance, thereby assuring an improvement in the characteristics and reliability of a multilayer interconnection structure. According to this invention there is a multilayer interconnection structure for a semiconductor device comprising: a semiconductor substrate on which a first insulating layer is formed; a lower interconnection layer positioned on said first insulating layer, said lower interconnection layer being connected to the semiconductor substrate by means of a number of separate contact holes which are formed in said first insulating layer and which are linearly arranged in the direction in which said lower interconnection layer extends; a second insulating layer having a stepped portion on its upper surface which is defined by the surface shape of said first insulating layer above said contact holes; and an upper interconnection layer deposited an said second insulating layer, said upper interconnection layer crossing said lower intercannection layer and traversing a plurality of said contact holes, thereby passing over a stepped portion of said second insulating layer as well as a region free from any stepped portion. A multilayer interconnection structure embodying this invention has the advantages that the upper interconnection layer where it crosses the lower interconnection layer, passes over a portion of the lower interconnection layer between adjacent contact holes, thereby suppressing the disconnection of the interconnection layer and the increased resistance of wiring; and improvement is assured on the characteristics and reliability of a multilayer interconnection structure, thereby prominently increasing the application of said structure to the technical field of a semiconductor device. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a plan view of the conventional multilayer interconnection structure for a semiconductor device; Fig. 2 is a sectional view along line A-A of Fig. 1 ; Fig. 3 is a plan view of a multilayer interconnection structure according to a first embodiment of this invention; and Fig. 4 is a cross-sectional view along line C-C of Fig. 3. Description will now be given with reference to Fig. 3 of a multilayer interconnection structure according to a first embodiment of this invention. The parts of Fig. 3 the same as those of Fig. 1 are denoted by the same numerals, description thereof being omitted. The structure of Fig. 3 is different from that of Fig. 1 in that in the conventional multilayer interconnection structure, a single contact hole 4 is drilled in a state to cross the whole width of a third interconnection layer 7, while in the multilayer interconnection structure embodying this invention, a plurality of separate contact holes 8a, 8c, 8d are provided below the third interconnection layer 7. In other words, four small contact holes 8a, 8b, 8c, 8d are linearly drilled in the first insulating film 3 along the second interconnection layer 5. In the multilayer interconnection structure arranged as described above, part of the transverse region of the third interconnection layer 7 in that section which crosses the second interconnection layer 5 does not overlap the contact holes 8a, 8b, 8c, 8d. Therefore, the above-mentioned portion of the third interconnection layer 7 passes a region free from any stepped portion. In this case, the section along line B-B of Fig. 3 indicates the same pattern as that of Fig. 2. Namely, the third interconnection layer 7 overlap the contact hole 8c and cross a stepped portion. In the section along line C-C of Fig. 3, however, the third interconnection layer 7 does not overlap any of the contact holes. As shown in Fig. 4, therefore, the third interconnection layer 7 crosses a step-free region. Accordingly, the embodiment of Fig. 3 offers the advantages that it is possible to suppress the disconnection of a third interconnection layer 7 in the stepped portion, and the cutting of wiring and increased wiring resistance caused by the reduced thickness of the thus interconnection layer 7, thereby assuring improvement in the characteristics and reliability of a multilayer interconnection structure. The characteristics of connection between adjacent interconnection layers through an intervening contact hole are governed not only by the area of the contact hole but also its peripheral length. In the embodiment of Fig. 3, a plurality of contact holes collectively occupy a smaller area than in the convention multilayer interconnection structure, but the total length of their peripheries is more enlarged. Therefore, the characteristics of connecting between adjacent interconnection layers deteriorate little. With a multilayer interconnection structure embodying this invention, the interconnection layer and contact portion are prepared from aluminium, polysilicon, or refractory metal silicide. Further, the number of contact holes need not be limited to four as previously described, but may be varied. There may also be more than three interconnection layers. The foregoing embodiments refer to the case where the substrate and the interconnection layer were connected together through a contact hole formed in the first insulating film. However, it will be noted that this invention is not limited to said embodiments, but is applicable to the case where any selected interconnection layers are connected together through a through hole formed in an insulating film interposed between said interconnection layers. Throughout the specification of this invention, it should be understood that the form "contact hole" is defined to include a through hole.

Claims: 1. A multilayer interconnection structure for a semiconductor device comprising: a semiconductor substrate (1) on which a first insulating layer (3) is formed; a lower interconnection layer (5) positioned on said first insulating layer (3), said lower interconnection layer (5) being connected to the semiconductor substrate (1) by means of a number of separate contact holes (8a, 8b, 8c, 8d) which are formed in said first insulating layer (3) and which are linearly arranged in the direction in which said lower interconnection layer (5) extends; a second insulating layer (6) having a stepped portion on its upper surface which is defined by the surface shape of said first insulating layer (3) above said contact holes (8a, 8b, 8c, 8d); and an upper interconnection layer (7) deposited an said second insulating Layer (6), said upper interconnection layer (7) crossing said lower interconnection layer (5) and traversing a plurality of said contact holes (8b, 8c), thereby passing over a stepped portion of said second insulating layer (6) as well as a region free from any stepped portion.

Inventors: USHIKU, YUKIHIRO
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1983
Main classification: H01L23
IPC codes: H01L23, H01L21