Semiconductor device having a composite insulating interlayer

Abstract: A semiconductor device has a first interconnection pattern (22) formed on a semiconductor substrate (21), and a second interconnection pattern (25) located in and over a through hole (A) formed at a composite insulating layer structure (23, 24). The composite insulating layer structure is constituted by a first inorganic insulating film (23) and an organic insulating film (24). At a peripheral region of the second interconnec­ tion pattern (25), the organic insulating film (24) is partially eliminated to form an eliminated portion (B). The semiconductor device also has a second inorganic insulating film (25) which is formed over the organic insulating film (24) and is directly formed on the first inorganic insulating film (23), via the eliminated portion (B).

Description: The present invention relates to a semiconductor device having a multi-layered interconnection structure. A conventional multi-layered interconnection structure will be explained below in connection with the process of forming an inorganic insulating film as a passivation film over a composite organic/inorganic insulating layer structure, by referring to Fig. 2. First, 1.0 µm-thick plasma SiN film 13 (hereinafter referred to as a P-SiN) is deposited by a plasma CVD method on first interconnection layer 12 (1.0 µm-thick Aℓ-Si layer) of a predetermined pattern formed on a thermal SiO 2 -carrying semiconductor substrate 11 and then a through-hole A of a predetermined pattern is formed in the surface portion of the resultant structure by virtue of an ordinary photolithography and RIE (reactive ion etching) methods. A second through-hole of a predetermined pattern is formed by virtue of the ordinary photolithography and RIE methods on the structure subsequent to the coating of polyimide resin 14 and a predetermined heat treatment. Then second interconnection layer 15 (Aℓ-Si 10 µm-thick) of a predetermined pattern is formed by the ordinary sputtering, photolithography and RIE methods. After a sintering step, 1.0 µm-thick P-SiN layer 16 is formed as a passivation film and pad opening 18 is formed by the ordinary photolithography and CDE (chemical dry etching) methods. After eliminating the photo-resist, a semiconductor device is completed which has a conventional multi-layered interconnection structure-see Fig. 2(b). Fig. 2(c) is a plan view where 17 denotes a dicing line and 19 shows cracks in inorganic insulating film 16 for passivation. The composite interlayer of organic insulating film 14 and inorganic insulating film 13 has the advantages of being easier-to-handle in process, less in an electrical variation, higher in breakdown voltage and lower in cost. On the other hand, inorganic passivation film 16 is excellent in the resistance to humidity, as well as in the mechanical strength, as well known in the art. For this reason, a great number of semiconductor devices have been manufactured which adopt a combination of the composite interlayer and inorganic passivation film. When, after the assembly of the conventional combination type semiconductor structure, it is incorporated into an associated circuit board, a thermal shock test is conducted at which time a sample is quickly heated at 280° for 30 seconds, followed by a PCT step at 2.5 atmospheres at 127°C for 20 hours. It has been found that 10% of samples tested are bad in a corrosion mode. In this connection reference is made to Fig. 3. Here, PCT is a forced humidity-resistance test using pressure and temperature. By the term "corrosion" is meant the corrosion of an interconnection layer due to, for example, water. Corrosion occurs all at pad site 18. This is due to stress because of the inorganic passivation film, per se, at the pad site and to stress because of the mold resin, as set out below. That is, inorganic passivation film 16 is formed on organic insulating film 14 and, upon the application of stress thereto, readily moved in the direction of a force applied. Since pad site 18 at the boundary of a pattern-free field area is moved by such a force to a greater extent, greater deformation occurs at the metal area of pad site 18 and cracks 19 occur at inorganic passivation film 16 with which the pad site is covered. US 4 613 888 discloses a semiconductor device having a multi-layered wiring structure. On the semiconductor substrate, a first patterned wiring layer is formed. A first inorganic insulating film covers the exposed portions of substrate and the wiring layer. An organic insulating film is formed on the resulting structure and a second wiring layer is provided on the organic insulating film. The organic insulating layer is etched using the second wiring layer as a mask to form an eleminated portion. A second inorganic insulating film is formed on the structure which film is in contact with the first inorganic insulating film without going through a soft inorganic or organic film. The device exhibits improved characteristics regarding reliability as discussed above. Against this background in the prior art, it is the object of the invention to provide a semiconductor device with a multi-layered interconnection strucuture achieving a still higher reliability by preventing the occurence of cracks caused by thermal shocks. To achieve this object, the semiconductor device of a multi-layered interconnection structure according to the invention comprises: a semiconductor substrate; at least a first and second patterned interconnection layer subsequently formed over said semiconductor substrate; - a first inorganic insulating film formed over said semiconductor substrate and the first interconnection layer; an organic insulating film which is formed on said inorganic insulating film and on which said second patterned interconnection layer is formed, which has an eliminated portion; a second inorganic insulating film formed on said second interconnection layer, said organic insulating film and said first inorganic insulating film, said second inorganic insulating film being in contact with said first inorganic insulating film through said eliminated portion in said organic insulating film. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Figs. 1(a), 1(b) and 1(c) are views showing a practical semiconductor device according to an embodiment of the present invention; Figs. 2(a), 2(b) and 2(c) are views showing a conventional semiconductor device; Fig. 3 is a graph showing a relation of a PCT to an accumulated rate of defects (%); Fig. 4 is a view showing a practical semiconductor device employing a composite insulating layer structure having a plurality of layers; Fig. 5 is a view showing a practical semiconductor device including a capacitive element; Fig. 6 is a view showing a practical semiconductor device with an eliminated portion of its organic insulating film formed as being broader in area; and Fig. 7 is a cross-sectional view showing a semiconductor device having an uneven surface according to another embodiment of the present invention. The embodiment of the present invention will be explained below with reference to Fig. 1. An Aℓ-Si interconnection layer 22 was formed as a first layer of a predetermined pattern on thermal SiO 2 film-formed semiconductor substrate 21 by virtue of an ordinary sputter, photolithography and RIE methods. Then 1.0 µm-thick P-SiN film 23 was deposited by a plasma CVD method on the resultant structure and a given through-hole A was formed in P-SiN film 23 by the photo-lithography and RIE methods. Subsequent to removing a photoresist for the formation of the through-hole, coating a polyimide resin and heat-treating the resultant structure at 100° for 30 minutes and 250° for 60 minutes, a through-hole was formed by the ordinary photolithography and O2 RIE method such that it merges with the through-hole A in the P-SiN film and, at the same time, the polyimide was eliminated (indicated by B in Fig. 1), over a width of 20 µm, at a portion 15 µm from an area at which second interconnection pattern was formed inside a broader field area to provide 0.5 µm-thick polyimide film 24. After removing the photoresist for the formation of an opening, Aℓ-Si interconnection layer 25 of a predetermined pattern was formed as a second interconnection layer on the resultant structure by virtue of the ordinary sputtering and photolithography methods. Then 1.0 µm-thick P-SiN film 26 was formed as a passivation film on the resultant structure by virtue of a plasma CVD method and a predetermined pad opening C was formed on the semiconductor structure by the ordinary photolithography and CDE methods (see Fig. 1(b)). Fig. 1(c) is a plan view where 27 and 28 represent a dicing line and bonding pad site, respectively. Although, in the embodiment of the present invention, 0.5 µm-thick polyimide film and 1.0 µm-thick P-SiN film have been explained as being as the organic insulating film and inorganic insulating film, respectively, these films may be formed with a proper choice of their materials, their combination and their film thickness. The dimension of the eliminated portion of the polyimide film around the second interconnection pattern, if having a crack prevention effect, may be properly selected. The aforementioned embodiment of the present invention has various advantages over the multi-interconnection structure of a conventional composite insulating interlayer, that is, the advantages of being easier-to-handle in process, of a high breakdown voltage, a higher resistance to humidity, of low cost and, for the reason set forth below, of being higher in reliability (see Fig. 3). Since the inorganic insulating film underlying the organic insulating film and inorganic insulating film overlaying a metal interconnection layer formed on the organic insulating film are formed in direct contact with each other at the aforementioned eliminated portion of the organic insulating film around the second interconnection pattern, the inorganic passivation film per se, even if being subject to a force resulting from the stress of the molding resin for instance, is not moved in the direction of that force. As a result, there occurs almost no deformation at the metal interconnection layer portion, such as the pad site inside the broader filled area, and, furthermore, neither cracks nor corrosion is developed at the passivation film (inorganic insulating film). In addition, no corrosion occurs in the second interconnection layer. No extra process is necessary because it is possible to perform the removal of the organic insulating layer portion and the simultaneous formation of a through-hole. A plurality of insulating layers is used in the composite insulating interlayer as shown in Fig. 4. The composite insulating interlayer becomes complex and the individual layers become thinner. In this case, the involved film structure is weaker than a simpler layer structure in terms of its strength against thermal stress and, therefore, the present invention can effectively applied to this case in particular. Fig. 5 shows a semiconductor device when a capacitive element is formed on substrate 21 by using composite insulating interlayer 23,24. With an increasing capacitance area, the corresponding insulating layer structure becomes greater. This leads to a larger deviation caused by heat stress in the capacitance construction of the organic and inorganic insulating layer structure, and hence to a greater risk of cracks. The present invention is effectively applied to this type of structure. The aforementioned eliminated portion of the organic insulating film may be formed as being as an area as shown in Fig. 6, not as being linear in the first embodiment of the present invention. Since, according to the present invention, two inorganic insulating films are formed in direct contact with each other at the aforementioned eliminated portion of the organic insulating film, it is possible to enhance the resistance to stress as caused by heat shock and hence to attain an enhanced resistance with the presence of an increasing contact area of the aforementioned inorganic insulating films. Fig. 7 shows a portion of a semiconductor device including a multi-layered structure. In the arrangement shown in Fig. 7, first and second interconnection layers 22,25 are of aluminum; first and second insulating films 23 and 26 of P-SiN; organic insulating film 24 of a polyimide resin; insulating film 30 of a thermal SiO 2 ; insulating film 31 of a CVD-SiO 2 ; gate electrode 32 of poly-Si; insulating film 33 of a CVD-SiO 2 ; and resistive element 34 of poly-Si. In a complex semiconductor device including a multi-layered structure, semiconductor substrate 21 is often formed to have an uneven surface and the resultant structure becomes complex and unstable in terms of its strength. The present invention can also be applied to the semiconductor device including uneven semiconductor substrate 21 so that an added strength may be provided to the insulating layer structure. As first and second inorganic insulating films 23 and 26, use may be made of an oxide, nitride or carbide in the form of silicon oxide, silicon nitride or silicon carbide. A polyimide resin may be used for organic insulating film 24 which, together with the inorganic insulating film, forms a composite insulating layer structure.

Claims: A semiconductor device of a multi-layered interconnection structure comprising: a semiconductor substrate (21); at least a first and second patterned interconnection layer (22, 25) subsequently formed over said semiconductor substrate (21); a first inorganic insulating film (23) formed over said semiconductor substrate (21) and the first interconnection layer (22); an organic insulating film (24) which is formed on said inorganic insulating film (23) and on which said second patterned interconnection layer (25) is formed and which has an eliminated portion (B); a second inorganic insulating film (26) formed on said second interconnection layer (25), said organic insulating film (24) and said first inorganic insulating film, said second inorganic insulating film (26) being in contact with said first inorganic insulating film (23) through said eliminated portion (B) in said organic insulating film (24).

Inventors: ABE MASAHIRO, MASE YASUKAZU, YAMAMOTO TOMIE, ABE, MASAHIRO, MASE, YASUKAZU, YAMAMOTO, TOMIE, Abe, Masahiro c/o Patent Division, K.K. Toshiba, Mase, Yasukazu c/o Patent Division, K.K. Toshiba, Yamamoto, Tomie c/o Patent Division, K.K. Toshiba
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1988
Main classification: H01L23
IPC codes: H01L21, H01L23