JPH0377321A - Formation of electrode connecting hole in semiconductor device - Google Patents

Abstract

PURPOSE:To make a coverage of an electrode interconnection layer good in a part of an electrode connecting hole and to reduce a danger of a disconnection and the like in the part by a method wherein a recessed part which is larger than the electrode connecting hole to be formed is formed in a definite depth on an insulating film by a photolithographic operation and, after that, the electrode connecting hole is formed in a position where the recessed part has been formed by executing the photolithographic operation again. CONSTITUTION:A patterning operation of an electrode connecting hole is executed by using a photomask having an opening pattern which is larger than the electrode connecting hole to be formed. By adopting an RIE operation, an insulating film 2 is etched down to a definite depth from its surface to form a recessed part 3. Then, the BPSG film 2 in which the recessed part has been formed is annealed in a steam atmosphere; side faces of the vertically steep recessed part 3 are made to reflow; a gentle curve-shaped recessed part 4 is formed. By a second photolithographic operation, an electrode connecting hole 5 which has pierced the insulating film 2 is formed in the recessed part 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for forming electrode connection holes in an insulating film formed on a semiconductor substrate. .

[Conventional technology]

In semiconductor devices, such as silicon semiconductor devices, AI is used to interconnect elements such as diodes and transistors formed on the wafer surface to form a circuit.
electrode wiring is required. This electrode wiring is formed on an insulating film made of an oxide film such as Sin formed on the wafer surface, and the electrode wiring formed in this way is
It is connected to each element formed on the wafer surface through electrode connection holes drilled in the insulating film.

Photolithography is generally used as a conventional method for forming such electrode connection holes.

In this method, as is well known, the electrode connection holes are patterned using a photomask having a pattern corresponding to the electrode connection holes, and then the insulating film is etched by RIE (reactive ion etching). Electrode connection holes are etched perpendicularly to the surface. moreover,
After this, taper etching is performed on the electrode connection hole that has been formed using a glue flow process or other methods, so that the side surface of the electrode connection hole has a gently sloped surface. I have to.

By forming the side surface of the electrode connection hole into a gently sloped surface, the step coverage of the electrode wiring layer that covers this area is improved, and as a result, the electrode wiring can be formed in such a part of the electrode connection hole. This is to avoid the risk of disconnection.

(Problem to be Solved by the Invention) However, even when the side surface of the electrode connection hole is formed into a gently sloped surface, the ratio between the height and width (aspect ratio) of the formed electrode connection hole is It remains constant regardless of whether an inclined surface is attached or not. Therefore, when the thickness of the insulating layer is constant and the height of the electrode connection hole is constant, the aspect ratio increases as the width of the electrode connection hole decreases. Such a large aspect ratio is undesirable because the coverage of the electrode wiring layer deteriorates accordingly, increasing the risk that the wiring at the electrode connection hole will become disconnected.

In view of these conventional problems, it is an object of the present invention to provide a method for forming electrode connection holes that is better than the conventional method for forming electrode connection holes, even when the thickness of the insulating film and the size of the electrode connection holes to be formed are the same.
The object of the present invention is to propose a method for forming electrode connection holes that makes it possible to reduce the effective aspect ratio of the electrode connection holes that are formed.

[Means to solve the problem]

In order to solve the above problems, in the method of the present invention, photolithography is performed multiple times, usually twice, to form electrode connection holes. That is,
In the first photolithography, patterning was performed at the electrode connection hole formation position using a photomask with a large opening forming part that encompassed the electrode hole, and then patterning was performed to a depth that did not penetrate the insulating film. Etching is performed to form a recessed portion larger than the electrode connection hole at the electrode connection hole formation position. After this, the insulating film is reflowed and the formed recess is made into a curved recess as a whole.A second photolithography is performed to taper-etch the recess formation position and form an electrode connection hole. Form. At this time, a photomask having a pattern corresponding to the electrode connection hole is used to make the electrode connection hole in the portion of the insulating film where the recess is formed.

[Effect]

In the above method, by the first photolithography, a recess with a constant depth larger than the electrode connection hole is formed at the electrode connection hole formation position in the insulating film having the thickness T. In this part, the thickness of the insulating film is as thin as t (<T). Since the electrode connection hole is formed in the thinned insulating film part by the second photolithography, the effective aspect ratio of the connection hole in this case is as follows, where W is the width of the electrode connection hole. The aspect ratio is T/W, which is smaller than the aspect ratio T/W of the connection hole according to the conventional method. As described above, in the method of the present invention, by increasing the depth of the recess formed in the first photolithography and reducing the thickness t of the insulating film in the electrode connection hole forming part, The aspect ratio can be reduced. Therefore, it is possible to prevent the step coverage of the electrode wiring layer from deteriorating in such a portion of the electrode connection hole.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1(A) to FIG. 1(E) show an embodiment of the present invention, and as shown in FIG. 1(A), Si-based Fi
1 shows the process of forming electrode connection holes of 1 μm square in an insulating film 2 formed on the surface of a semiconductor device 1. The insulating film 2 of this example is a BPSG film (P: 5wt%, B: 2wt%) with a thickness of 1 μm.
).

First, as shown in FIG. 1(B), a recess 3 was formed in the BPSG film 2 at the electrode connection hole formation position by a first photolithography process. In this example, patterning of the electrode connection holes is performed using a photomask that has an open pattern of 2 μm square, four times the size of the electrode connection hole to be formed, at the electrode connection hole formation position. Ta. Then, RYE was employed as the etching method, and the insulating film 2 was etched to a depth of about 0.6 μm from the surface. In this way, a recess 3 having a square size of 2 μm and a depth of 0.6 μm was formed as shown in the figure.

Next, the BPSG film 2 in which the recesses have been formed is annealed for 30 minutes in a steam atmosphere at 950°C, and the side surfaces 3a of the vertical recesses 3 are reflowed, as shown in FIG.
As shown in C), a gently curved recess 4 was formed. As a result, the BPSC at the position where the recess 4 is formed;
The thickness t of the film was approximately 0.5 μm.

Thereafter, electrode connection holes were formed in the recessed portions 4 by a second photolithography process. In this case, patterning of the electrode connection holes was performed using a photomask having a 1 μm square open pattern corresponding to the electrode connection holes to be formed. Taper etching was then performed by RIE to form a 1 μm square electrode connection hole 5 penetrating the insulating film, as shown in FIG. 1(D).

In the electrode connection hole No. 5 formed in this way,
The thickness of the insulating film 2, which is the depth thereof, is approximately 0.5 μm, and the width W thereof is 1 μm, and the effective aspect ratio in this case can be considered to be 0.5. Therefore, the aspect ratio (2) is half of the conventional case where a 1 .mu.m square electrode connection hole is formed in a 1 .mu.m thick insulating film by a single photolithography process.

Finally, as shown in FIG. 6 to 0.8μm
only deposited. As a result, disconnection at the contact portion 7 between the wiring side and the SN substrate through the electrode connection hole 4 does not occur.
The step coverage rate of the Al-1%St wiring in the electrode connection hole portion was about 60%, which was a good result.

Here, in the above example, the first photolithography is performed to form a recess that is twice the width of the electrode connection hole to be formed and has a depth that is approximately half the depth of the insulating film. However, the present invention is not limited to these values. The size of the recess may be any size that includes the electrode connection hole to be formed and is larger than this. It has been confirmed that this dimension is desirably in a range of, for example, about 1.5 to about 3 times the width of the electrode connection hole.

Furthermore, it has been confirmed that the depth of the recess is desirably in the range of about 1/3 to about 2/3 of the thickness of the insulating film.

Note that the above example shows one embodiment of the present invention,
It is not intended that the invention be limited to this example. For example, it goes without saying that the dimensions of the electrode connection hole to be formed, the thickness of the insulating film, etc. may be different from those in the above example, and the sides of the formed recess or electrode connection hole may be smoothed. Of course, methods other than those described above may also be used for forming the inclined surface.

(Effects of the Invention) As explained above, in the method of the present invention, first, a recess larger than the electrode connection hole to be formed is formed at a certain depth on the insulating film by photolithography, and then again by photolithography. Accordingly, an electrode connection hole is formed at the position where the recess is to be formed. Therefore, according to the method of the present invention, since the electrode connection hole is formed at the recess formation position where the thickness of the insulating film is thinner, the aspect ratio of the formed electrode connection hole is lower than the thickness of the insulating film at the recess formation position. It becomes substantially smaller depending on the thickness of the insulating film. Therefore, the coverage of the electrode wiring layer in the electrode connection hole portion is improved, the possibility of disconnection in this portion is reduced, and the reliability of the electrode wiring is improved.

[Brief explanation of drawings]

FIG. 1(A) is a block diagram showing a Si substrate on which an insulating film is formed, FIG. 1(B) is a block diagram showing a state in which a recess is formed on the insulating film by the first photolithography, Figure 1 (C) is a configuration diagram showing the state after the side surfaces of the recess on the insulating film are made into gently sloped surfaces, and Figure 1 (D) is a configuration diagram showing the state after the side surfaces of the recess on the insulating film are made into gentle slopes. FIG. 1(E) is a block diagram showing the state after formation, and FIG. 1(E) is a block diagram showing the state in which the electrode wiring layer is deposited on the insulating film in which the electrode connection hole is formed. Explanation of symbols 1... St substrate 2... BPSG film (insulating film) 3... - Recess 3a - - Sharp side surface of the recess 4 - Curved recess 5 - Electrode connection hole 6 −・−Wiring.

Claims (1)

[Claims] In a method for forming an electrode connection hole in an insulating film made of an oxide film containing phosphorus and boron formed on a semiconductor substrate, a hole larger than the electrode connection hole is provided at a position where the electrode connection hole is formed. forming a recess on the insulating film with a size that includes the electrode connection hole and a depth that does not penetrate the insulating film by photolithography using a photomask having an opening forming part with the same dimensions; a step of reflowing the insulating film in which the recess is formed; and taper etching the recess formed on the insulating film by photolithography using a photomask for forming the electrode connection hole to form the electrode connection. A method for forming an electrode connection hole in a semiconductor device, comprising the steps of forming a hole.