Semiconductor device having an inspection hole striding a boundary

This application is based on Japanese patent application No. 2005-016067, the content of which is incorporated hereinto by reference.

1. Technical Field

The present invention relates to a semiconductor device.

2. Related Art

The integration level and micronization of semiconductor devices are advancing further and further. This naturally requires designing a contact for connecting an interconnect layer and an electrode of elements such as transistors and capacitors, and a via for connecting the interconnect layers, in a smaller diameter. If a contact or a via (hereinafter generally referred to as “conductive plug”) is not properly opened, the semiconductor device results in being defective. Accordingly, in-line inspection of the conductive plug hole is becoming more critically important. Such inspection can be executed by providing an inspection hole apart from the conductive plug hole, and observing the bottom of the inspection hole through a scanning electron microscope (SEM).

In this relation, for example JP-A No. 2004-119449 discloses a semiconductor device as shown in FIG. 7 , which is a plan view for explaining positioning of an inspection hole in the semiconductor device. In FIG. 7 , an inspection hole 101 in the conventional semiconductor device is located, like the conductive plug hole, on a diffusion layer or an interconnect layer 102 .

With the structure as shown in FIG. 7 , however, only the diffusion layer or the interconnect layer 102 is exposed at the bottom of the inspection hole 101 , as shown in FIG. 8 . Here, FIG. 8 is a schematic drawing of a SEM image taken at the time of the inspection of the hole. Accordingly, the SEM only provides a uniform image of the bottom of the inspection hole 101 , from which it is difficult to decide whether the hole is properly formed. Just because of the foregoing progress in integration level and micronization of the semiconductor device, this problem has come up as an important issue to be addressed.

According to the present invention, there is provided a semiconductor device comprising a semiconductor substrate; a diffusion layer provided in a surface layer of the semiconductor substrate; an interconnect layer provided at an upper level from the semiconductor substrate; a conductive plug provided in a plug hole extending from the diffusion layer to the interconnect layer; and an inspection hole extending from the diffusion layer to the interconnect layer; wherein the inspection hole is located so that an opening of the inspection hole on the side of the diffusion layer strides across a boundary of the diffusion layer.

The semiconductor device thus configured includes the inspection hole extending from the diffusion layer to the interconnect layer, like the plug hole. Moreover, the opening of the inspection hole on the diffusion layer side strides across the boundary of the diffusion layer. With such structure, the boundary of the diffusion layer can be recognized at the in-line inspection, when the hole is properly formed. This significantly facilitates deciding whether the hole is properly formed.

The present invention also provides a semiconductor device comprising a first interconnect; a second interconnect layer provided at an upper level of a first interconnect layer including the first interconnect; a conductive plug provided in a plug hole extending from the first interconnect layer to the second interconnect layer; and an inspection hole extending from the first interconnect layer to the second interconnect layer; wherein the inspection hole is located so that an opening of the inspection hole on the side of the first interconnect layer strides across a boundary of the first interconnect layer.

The semiconductor device thus configured includes the inspection hole extending from the first interconnect layer to the second interconnect layer, like the plug hole. Moreover, the opening of the inspection hole on the first interconnect layer side strides across the boundary of the first interconnect layer. With such structure, the boundary of the first interconnect layer can be recognized at the in-line inspection, when the hole is properly formed. This significantly facilitates deciding whether the hole is properly formed.

Accordingly, the present invention provides a semiconductor device that facilitates effectively inspecting the conductive plug holes.

The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view showing a semiconductor device according to an embodiment of the present invention;

FIG. 2 is an enlarged fragmentary plan view of the same, for explaining positioning of a contact-inspection hole;

FIG. 3 is an enlarged fragmentary plan view of the same, for explaining positioning of a via-inspection hole;

FIG. 4 is a schematic drawing of a SEM image taken at a contact hole inspection of the semiconductor device according to the embodiment;

FIG. 5 is a schematic drawing of a SEM image taken at a via hole inspection of the semiconductor device according to the embodiment;

FIG. 6 is an enlarged fragmentary plan view showing a variation of the semiconductor device according to the embodiment;

FIG. 7 is a plan view of a conventional semiconductor device, for explaining the positioning of the inspection hole; and

FIG. 8 is a schematic drawing of a SEM image taken at a contact hole inspection of the conventional semiconductor device.

The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposed.

Hereunder, a preferred embodiment of a semiconductor device according to the present invention will be described in details, referring to the accompanying drawings. Regarding the drawings, same constituents are given the same numerals, and duplicating description thereof will be omitted.

FIG. 1 is a cross-sectional view showing the semiconductor device according to the embodiment of the present invention. The semiconductor device 1 includes a semiconductor substrate 10 , a diffusion layer 12 , an interconnect layer 20 , a contact plug 30 , a contact-inspection hole 34 , a via plug 40 , and a via-inspection hole 44 .

In the surface layer of the semiconductor substrate 10 , the diffusion layer 12 is provided. The diffusion layer 12 , a gate electrode 14 and so on constitute a MOS transistor. An insulating layer 16 is provided so as to bury the MOS transistor. In the surface layer of the semiconductor substrate 10 , also an isolation region 18 is provided.

Above the semiconductor substrate 10 , the interconnect layer 20 is provided. The interconnect layer 20 includes an interconnect layer 20 a (first interconnect layer) and an interconnect layer 20 b (second interconnect layer). The interconnect layers 20 a , 20 b respectively include an interconnect 22 a (first interconnect) and an interconnect 22 b (second interconnect). In the interconnect layer 20 a , the interconnect 22 a is covered with an insulating layer 26 a . Likewise, in the interconnect layer 20 b the interconnect 22 b is covered with an insulating layer 26 b.

The insulating layer 16 includes a contact plug hole 32 . The contact plug hole 32 penetrates through the insulating layer 16 , thus extending from the diffusion layer 12 to the interconnect layer 20 . The contact plug hole 32 includes the contact plug 30 . The contact plug 30 has one end connected to the diffusion layer 12 , and the other end connected to the interconnect 22 a . The contact plug 30 serves as a conductive plug that electrically connects the diffusion layer 12 and the interconnect 22 a.

The insulating layer 16 also includes the contact-inspection hole 34 . Similarly to the contact plug hole 32 , the contact-inspection hole 34 also penetrates through the insulating layer 16 thus extending from the diffusion layer 12 to the interconnect layer 20 . The contact-inspection hole 34 is generally the same as the contact plug hole 32 in diameter, depth and profile.

Referring to FIG. 2 , the positioning of the contact-inspection hole 34 will be described. As is apparent from FIG. 2 , the opening of the contact-inspection hole 34 on the side of the diffusion layer 12 is disposed across the boundary B 1 of the diffusion layer 12 , on the surface of the semiconductor substrate 10 . In this embodiment, the boundary B 1 represents the boundary between the diffusion layer 12 and the isolation region 18 .

Referring back to FIG. 1 , the insulating layer 26 a includes a via plug hole 42 . The via plug hole 42 penetrates through the insulating layer 26 a , thus extending from the interconnect 22 a to the interconnect layer 20 b . The via plug hole 42 includes the via plug 40 . The via plug 40 has one end connected to the interconnect 22 a , and the other end connected to the interconnect 22 b . The via plug 40 serves as a conductive plug that electrically connects the interconnect 22 a and the interconnect 22 b.

The insulating layer 26 a also includes the via-inspection hole 44 . Similarly to the via plug hole 42 , the via-inspection hole 44 also penetrates through the insulating layer 26 a thus extending from the interconnect 22 a to the interconnect layer 20 b . The via-inspection hole 44 is generally the same as the via plug hole 42 in diameter, depth and profile.

Referring to FIG. 3 , the positioning of the via-inspection hole 44 will be described. As is apparent from FIG. 3 , the opening of the via-inspection hole 44 on the side of the interconnect 22 a is disposed across the boundary B 2 of the interconnect 22 a . In this embodiment, the boundary B 2 represents the boundary between the interconnect 22 a and the insulating layer 26 a.

Again back to FIG. 1 , on the interconnect layer 20 b , another interconnect layer of a similar structure to that of the interconnect layers 20 a , 20 b is stacked. At an uppermost level, an uppermost interconnect 52 , and a passivation layer 54 covering the uppermost interconnect 52 are provided.

Advantageous effects of the semiconductor device 1 are described here below. The semiconductor device 1 includes the contact-inspection hole 34 extending from the diffusion layer 12 to the interconnect layer 20 . Here, the opening of the contact-inspection hole 34 on the side of the diffusion layer 12 strides across the boundary B 1 ( FIG. 2 ) of the diffusion layer 12 . Under such structure, the boundary B 1 of the diffusion layer 12 can be recognized at the bottom of the contact-inspection hole 34 , at the in-line inspection thereof as shown in FIG. 4 , provided that the hole is properly formed. At the bottom of the contact-inspection hole 34 , the diffusion layer 12 and the isolation region 18 are exposed on the respective sides of the boundary B 1 . FIG. 4 is a schematic drawing of a SEM image taken at the contact hole inspection. Such structure significantly facilitates deciding whether the contact plug hole 32 is properly formed.

Further, the semiconductor device 1 includes the via-inspection hole 44 extending from the interconnect 22 a to the interconnect layer 20 b . Here, the opening of the via-inspection hole 44 on the side of the interconnect 22 a strides across the boundary B 2 ( FIG. 3 ) of the interconnect 22 a . Under such structure, the boundary B 2 of the interconnect 22 a can be recognized at the bottom of the via-inspection hole 44 , at the in-line inspection thereof as shown in FIG. 5 , provided that the hole is properly formed. At the bottom of the via-inspection hole 44 , the interconnect 22 a and the insulating layer 26 a are exposed on the respective sides of the boundary B 2 . FIG. 5 is a schematic drawing of a SEM image taken at the via hole inspection. Such structure significantly facilitates deciding whether the via-inspection hole 42 is properly formed.

While the semiconductor device according to this embodiment includes both of the contact-inspection hole 34 and the via-inspection hole 44 , the semiconductor device may include only either thereof. Also, the number the interconnect layers is not limited to that of the structure shown in FIG. 1 , but may be any different number.

Further, the contact-inspection hole 34 may be disposed in various different manners, as long as being located so as to stride across the boundary of the diffusion layer 12 . For example, the contact-inspection hole 34 may be disposed so that the opening thereof on the side of the diffusion layer 12 partially overlaps a corner portion of the diffusion layer 12 , as shown in FIG. 6 . This also applies to the via-inspection hole 44 , i.e. the opening on the side of the interconnect 22 a may be disposed so as to partially overlap a corner portion of the interconnect 22 a.

Further, in this embodiment, while the contact-inspection hole 34 and the via-inspection hole 44 are filled with the conductive materials constituting the contact plug 30 and the via plug 40 , the contact-inspection hole 34 and the via-inspection hole 44 may be not filled with anything. That is, there may remain a gap in the contact-inspection hole 34 and/or the via-inspection hole 44 .

It is apparent that the present invention is not limited to the above embodiment, and may be modified and changed without departing from the scope and spirit of the invention.