JPH08107106A - Method for controlling angle of taper at contact hole opening part - Google Patents

Abstract

PURPOSE: To easily but accurately taper the opening part of a contact hole at the desired taper angle by easily controlling the taper angle. CONSTITUTION: The prescribed taper angle is formed on an upper layer part 2 by conducting etching of the upper layer part of the taper-forming part of a contact hole by the first etching process at a high etching rate in both vertical and horizontal directions when a flattening process is conducted. Subsequently, when a flattening process is conducted, the lower layer part 1 of the taper- forming part is etched by the second etching process at a high etching rate in vertical direction only. In the above-mentioned two-step etching process, in which the lower layer part is tapered the taper angle 2 of the lower layer part 1 is controlled by controlling the etching amount RH1 in horizontal direction of the upper layer part 2 of the first etching process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for etching an insulating layer of a semiconductor device, and more particularly to a method for controlling a taper angle of an opening for improving coverage of a contact hole.

[0002]

2. Description of the Related Art When a wiring layer of a semiconductor device such as a transistor is formed, an insulating layer is provided on a substrate, a contact hole is formed in the insulating layer of an electrode portion, and the contact hole is filled with a conductive material such as aluminum. A wiring pattern is formed on the insulating layer, and the electrode on the substrate side and the wiring pattern are connected via a contact (a conductive material filled in a contact hole). Such contact holes are formed by performing dry etching such as RIE on the insulating layer.

FIG. 6 shows TEOS (Tetra) as an insulating layer.
The contact hole formation state when using Ethoxy Silane) is shown. A TEOS layer 9 is formed on the substrate 8 and a photoresist 10 is laminated and patterned on the TEOS layer 9. In contrast to ion etching, TEOS hardly progresses in the horizontal direction when etching from a flat surface, but progresses only in the vertical direction. That is,
The etching rate (speed) RH in the horizontal direction is almost zero, and only the etching rate (speed) RV in the vertical direction becomes large. Therefore, as shown, substantially vertical holes are formed in the TEOS layer 9.

However, as the contact holes become finer with the recent trend of higher integration of semiconductor devices, the vertical contact holes formed in the TEOS layer as described above have poor coverage in the lower part of the holes when aluminum is filled. Causes problems such as poor connection and deterioration of conductive characteristics.

To address this problem, the insulating layer is TEO.
It has a two-layer structure of S layer and BPSG (boron-phosphorus silicate glass) layer provided thereabove, and after forming a vertical contact hole, heat treatment by reflow is performed to make the opening of the BPSG round and open area. Methods are used to widen and thereby improve aluminum coverage.

However, in the method using such a reflow process of BPSG, the BPSG process is performed during the reflow process.
Ions of boron and phosphorus therein may enter the substrate in the lower part of the hole and affect the characteristics. Therefore, particularly in the case of forming a hole in which it is necessary to avoid the influence of foreign ions, the reflow process is not performed and the BP is formed by etching.
A taper is formed in the contact hole opening of the SG or other insulating film to expand the opening area and improve the coverage of aluminum.

[0007]

However, in the conventional taper formation by etching, it is very difficult to control the taper angle, and it is possible to form an opening having an optimum taper angle corresponding to the hole diameter and depth. It was difficult and the coverage could not be improved sufficiently.

The present invention has been made in view of the above-mentioned drawbacks of the prior art. When a taper is formed at the contact hole opening, the taper angle can be easily controlled to form a taper of a desired angle. To provide a taper angle control method for

[0009]

In order to achieve the above object, in the present invention, an upper layer portion of a tapered portion of a contact hole is formed by a first etching process which has a high etching rate in both vertical and horizontal directions during flat surface treatment. Etching is performed to form a taper of a predetermined angle on the upper layer portion, and subsequently, the lower layer portion of the taper forming portion is etched by a second etching process in which the etching rate is high only in the vertical direction during flat surface treatment. In the two-step etching process that forms a taper in the lower layer,
A taper angle control method for a contact hole opening, wherein the taper angle of the lower layer portion is controlled by controlling the horizontal etching amount of the upper layer portion by the first etching process.

In a preferred embodiment, the upper layer portion is formed of a first insulating film having a high etching rate in both the vertical and horizontal directions, and the lower layer portion is formed of a second insulating film having a high etching rate only in the vertical direction. Configure and
It is characterized in that the first etching process for the upper layer portion and the second etching process for the lower layer portion are continuously performed under the same etching condition.

In another preferred embodiment, the upper layer portion and the lower layer portion are formed of the same insulating film, and the first etching process is performed under the first etching condition in which the etching rate is high in both vertical and horizontal directions. Then, the etching condition is changed, and the second etching process is performed under the second etching condition in which the etching rate is high only in the vertical direction.

[0012]

The taper is formed in the upper first insulating film by the first etching process. In the subsequent second etching process, the lower second insulating film is etched into a taper shape corresponding to the taper angle of the upper insulating film.

[0013]

1 is a flow chart of a taper angle control method according to an embodiment of the present invention. Further, FIG. 3 is an explanatory view of a sectional structure of a contact hole portion corresponding to this embodiment. The lower insulating film 1 made of TEOS is formed on the substrate 11 (step S1). A polysilicon electrode (not shown) is formed on the substrate 11, and a contact hole is formed in the insulating film on the polysilicon electrode by the method of the present invention. As described above, the TEOS forming the lower insulating film 1 is an insulating material that hardly etches in the horizontal direction when the ordinary flat surface is etched, but only in the vertical direction.

Next, the lower insulating film 1 made of TEOS
An upper insulating film 2 made of BPSG is laminated on the upper layer (step S2). As described above, this BPSG is an insulating material in which etching progresses in both vertical and horizontal directions when a normal flat surface is etched.

Subsequently, a photoresist 3 having a contact hole portion to be etched is formed by patterning (step S3).

Next, in step S4, the upper insulating film 2 is formed.
Is etched by RIE or the like. In this upper layer etching process of BPSG, the vertical etching rate is RV1 and the horizontal etching rate is RH1.
The etching progresses in both horizontal and vertical directions. Therefore, when the etching reaches the bottom surface of the upper insulating film 2, a taper having an angle θ1 of tan θ1 = RV1 / RH1 is formed on the upper insulating film 2.

Further, the upper layer etching process is directly advanced to the lower layer portion to etch the lower layer insulating film 1 made of TEOS (step S5). This lower layer etching process has the same etching conditions as the upper layer etching process. Normally, etching does not proceed in the horizontal direction with respect to TEOS but is performed at the etching rate RV2 only in the vertical direction. Since the taper is formed, etching progresses in the horizontal direction at RH1 corresponding to the taper angle θ1. Therefore, a taper with an angle θ2 that satisfies tan θ2 = RV2 / RH1 is formed on the lower insulating film 1. Therefore, by appropriately selecting the horizontal etching rate RH1 of the upper insulating film 2 in accordance with the vertical etching rate RV2 with respect to the lower insulating film 1 and controlling the horizontal etchback amount, the taper of the lower insulating film 1 can be reduced. The angle θ2 can be controlled.

Note that a taper with an angle of θ2 may be formed to the bottom surface of the lower TEOS layer, or the TEOS layer may be formed in two steps by changing the heat treatment conditions, and the lower TEOS layer may be subjected to vertical etching processing.

Specific examples of the etching conditions in the embodiment in which such an insulating film having a two-layer structure is processed by the etching process under the same conditions are as follows. Pressure: 1700 mTorr RF Power: 750 W Reaction gas: CHF3 / CF4 / Ar = 60/60/90
0 (SCCM) SCCM is Standard Cubic Cm per Minutes.

FIG. 2 is a flowchart of a contact hole taper angle control method according to another embodiment of the present invention. Further, FIG. 4 is an explanatory view of a sectional structure of a contact hole portion of this embodiment. First, an insulating film 4 (for example, a silicon oxide film formed by low pressure CVD of monosilane (SiH4)) is formed on the substrate 11 (step S6). Next, the resist 3 is patterned on the insulating film 4 in the same manner as in the embodiment of FIG. 3 (step S7).

Next, in step S8, a first etching process is performed to a predetermined depth d under the etching conditions in which the etching proceeds in both the vertical and horizontal directions.
If the vertical and horizontal etching rates at this time are RV and RH, respectively, tan θ1 = RV / in the upper layer portion of the insulating film 4 by this first etching process.
A taper with an angle θ1 of RH is formed.

Next, in step S9, the etching conditions are changed, and the insulating film 4 in the lower layer portion is etched under the etching conditions in which the etching rate RV 'advances only in the vertical direction on a normal flat surface. Under this etching condition, the etching rate in the horizontal direction is almost zero, but since the taper angle θ1 is formed in the upper layer portion, RH = RV
An etching rate component of / tan θ1 is generated, and the etching progresses not only in the vertical direction but also in the horizontal direction. Therefore, a taper with an angle θ2 that satisfies tan θ2 = RV ′ / RH is formed in the lower layer portion. Therefore, also in this embodiment,
Similar to the above-mentioned embodiment, by appropriately selecting RH corresponding to RV 'and controlling the etchback amount in the horizontal direction so that the taper angle θ1 of the upper layer portion becomes a predetermined angle, the taper of the lower layer portion is tapered. The angle θ2 can be controlled.

The specific etching conditions in the embodiment in which the insulating film has a single-layer structure as described above and the two-step etching process is performed on the single-layer insulating film by changing the etching conditions are as follows. .

First etching process: Pressure: 2000 mTorr RF Power: 300 W Reactive gas: CF4 / O2 = 130/20 (SCCM) Second etching process: Pressure: 1700 mTorr RF Power: 750 W Reactive gas: CHF3 / CF4 / Ar = 60/60/90
0 (SCCM) SCCM is Standard Cubic Cm per Minutes.

FIG. 5 is a diagram showing that the taper angle of the lower insulating film changes in accordance with the horizontal etchback amount of the upper insulating film. This drawing is a drawing schematically drawn based on the result of actual etching. An insulating layer 5 on the substrate 8,
6, 7 are formed. The upper insulating layer 7 is made of BPSG, for example, and the insulating layer 6 thereunder is made of TEOS, for example.
The lowermost insulating layer 5 is made of, for example, TEOS having a different heat treatment condition from the TEOS of the insulating layer 6. As described above, the upper insulating layer 7 is tapered in advance and the horizontal etchback amount on the surface is 0 nm, 100 nm,
Openings of four kinds of contact holes of 200 nm and 300 nm are formed. Regarding these four kinds of upper insulating layers 7, the second insulating layer 6 according to the above-described embodiment is used.
Is etched. By the etching process of the second layer, the taper of the angles θ1, θ2, θ3, θ4 corresponding to the etch back amount of the upper insulating layer 7 is formed in the insulating layer 6. That is, by appropriately selecting the horizontal etching retreat amount for the upper insulating layer by the first etching process, it is possible to form a taper of a desired angle with respect to the second insulating layer in accordance with the retreating amount. it can.

[0026]

As described above, in the present invention, the contact hole opening is formed in two steps of the upper layer and the lower layer, the upper layer is etched to form a taper in the upper layer, and the etching back amount is adjusted to adjust the upper layer. By appropriately adjusting the taper angle of, the taper of an angle corresponding to the taper angle of the upper layer is formed in the lower layer in the etching process of the lower layer. Therefore, since the taper angle of the lower layer can be controlled by controlling the taper angle of the upper layer, the etching conditions can be easily set and controlled, and a contact hole having an appropriate taper angle corresponding to the hole diameter and depth of the contact hole can be formed. It is possible to obtain a highly reliable semiconductor device in which the coverage is easily and reliably formed and metal wiring is provided.

[Brief description of drawings]

FIG. 1 is a flowchart of a contact hole taper angle control method according to an embodiment of the present invention.

FIG. 2 is a flowchart of a contact hole taper angle control method according to another embodiment of the present invention.

FIG. 3 is an explanatory diagram of an etching process of the embodiment of FIG.

4 is an explanatory diagram of an etching process of the embodiment of FIG.

FIG. 5 is an explanatory view of the operation of the method of the present invention.

FIG. 6 is an explanatory diagram of a conventional contact hole forming method.

[Explanation of symbols]

 1: Lower layer insulating film 2: Upper layer insulating film 3: Resist 11: Substrate

Claims (3)

[Claims] 1. An upper layer portion of a tapered portion of a contact hole is etched by a first etching process having a high etching rate in both vertical and horizontal directions during flat surface treatment to form a taper of a predetermined angle on the upper layer portion. Subsequently, in the two-step etching process of etching the lower layer portion of the taper forming portion by a second etching process having a large etching rate only in the vertical direction during flat surface treatment to form a taper in the lower layer portion, A method for controlling the taper angle of a contact hole opening, wherein the taper angle of the lower layer portion is controlled by controlling the horizontal etching amount of the upper layer portion by the first etching process. 2. The upper layer portion is formed of a first insulating film having a high etching rate in both the vertical and horizontal directions, and the lower layer portion is formed of a second insulating film having a high etching rate only in the vertical direction. Under the same etching conditions, the first etching process of the upper layer part and the second etching process of the lower layer part
2. The method for controlling the taper angle of a contact hole opening according to claim 1, wherein the etching process is performed continuously. 3. The upper layer portion and the lower layer portion are formed of the same insulating film, the first etching process is performed under a first etching condition having a high etching rate in both the vertical direction and the horizontal direction, and then the etching condition is performed. 2. The method for controlling the taper angle of a contact hole opening according to claim 1, wherein the second etching process is performed under a second etching condition in which the etching rate is changed only in the vertical direction.