JPH0533163A - Shape forming method of insulating film layer - Google Patents

Abstract

PURPOSE:To provide the technique of smoothing the profile which is formed at the time of etching away the insulating film layer on a substrate and leads to various kinds of problems. CONSTITUTION:A silicon oxide film layer 4 is formed on a silicon substrate 2 (a). Ar<+> is then implanted by ion implantation into the surface of the silicon oxide film layer 4 to form a damage layer 6 of a high etching rate (b). A photoresist 8 is then formed as a mask and is chemically etched to selectively remove the silicon oxide film layer 4 to a taper shape (c). Finally, the entire part of the silicon substrate 2 is heat treated. The damage layer 6 is recovered by this annealing and a smooth taper 14 in which a kink shape 12 does not exist formed (e).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a shape of an insulating film layer used in a semiconductor process or an optical integrated circuit process.

[0002]

2. Description of the Related Art Conventionally, in the formation of an insulating film layer of a semiconductor element, a boundary between a portion where the insulating film layer is etched and a portion where the insulating film layer remains is likely to have a sharp step. There is a problem that the metal wiring that crosses the wire is easily broken. Further, in forming an optical waveguide or the like of an optical integrated circuit, in order to guide or split light efficiently,
It is necessary to form the optical waveguide in a taper shape with a vertical / horizontal ratio of about 1/3 to 1/5, and development of a technique for forming the insulating film layer in a taper shape is desired.

Conventionally, the following methods have been known as a method of forming a tapered shape of an insulating film layer. (Prior Art 1) A layer having damage and a high etching rate is formed on the surface of an insulating film layer by means of ion implantation or the like, and then a desired pattern is selectively removed by chemical etching (for example, JP-B-55-8590). issue). (Prior Art 2) After forming a layer having a high etching rate on the surface of an insulating film layer, a desired pattern is selectively removed by chemical etching (for example, IEEE PROCEEDIN).
GS, Vol. 133, Pt. I, No. 1 (198
6) pg. 13). (Prior Art 3) Utilizing penetration of an etchant into the interface between an insulating film layer surface and a resist (for example, J. Ele.
chem. Soc: SOLID STATE SCIE
NCE and TECHNOLOGY, Vol. 12
4, No. 6 (1977) pg. 917).

[0004]

However, the above-mentioned taper forming method for the insulating film layer has the following drawbacks. First, in the method of using the etchant soak (Prior Art 3), the shape is smooth, but the process reproducibility and stability are not achieved. Further, although the method using a layer having a high etching rate such as (Prior Art 1) and (Prior Art 2) can improve the process reproducibility,
Since a kink-shaped profile is formed on the upper end of the tapered shape, this portion is, for example, in a semiconductor device,
It may cause breakage of the metal electrode formed on the top,
Further, the waveguide type optical device has been a problem such as a cause of scattering of guided light.

In view of this point, an object of the present invention is to provide a technique for smoothing various problematic profiles formed when the insulating film layer on the substrate is removed by etching.

[0006]

The invention according to claim 1 is
A step of forming an insulating film layer on the substrate, and implanting ions by a method such as ion implantation in the vicinity of the surface of the insulating film layer,
After forming the shape of the insulating film layer by a step of changing the etching rate in the thickness direction of the insulating film layer and a step of selectively removing the insulating film layer into a desired pattern by etching, It is characterized by adding a step of treating at a temperature higher than the temperature required for formation.

According to a second aspect of the present invention, a step of forming an insulating film layer on a substrate, and an etching rate higher than that of the insulating film layer with respect to at least one etchant having the insulating film layer above the insulating film layer are provided. Forming a large layer,
The shape of the insulating film layer is formed by a step of selectively removing the insulating film layer and the layer having a high etching rate into a desired pattern by etching, and a step of removing the layer having a high etching rate over the entire surface by etching. After that, a step of treating at a high temperature higher than the temperature required for forming the insulating film layer is added.

[0008]

In both of the first and second aspects of the invention, the required shape of the insulating film layer can be formed smoothly by the process of treating at a high temperature. For example, when the insulating film layer on the substrate is removed by etching,
A kink-shaped profile can be smoothed.

[0009]

EXAMPLES Examples of the present invention will be described below. First, the first embodiment will be described. 1A to 1E are cross-sectional views in which the method for forming the shape of an insulating film layer according to the first embodiment is applied to a semiconductor device. First, the silicon substrate 2
Silicon oxide film layer 4 at 1000 ° C. in a water vapor atmosphere
Of about 1 μm is formed (see FIG. 1A). Next, Ar + is implanted into the surface of the silicon oxide film layer 4 by ion implantation under the conditions of 50 keV and 5 × 10 ¹⁵ atoms / cm ² to form a damaged layer 6 having a high etching rate (see FIG. 1B). ).

Next, when the photoresist 8 is formed as a mask and chemical etching is performed, since the damage layer 6 has a higher etching rate than the silicon oxide film layer 4, the silicon oxide film layer 4 is selectively removed in a taper 10 shape. (Fig. 1
(See (c)). At this time, the etching is performed by a so-called wet etchant. Usually, hydrofluoric acid (5
0%): ammonium fluoride (40%) = 1: 6 is used as the buffered hydrofluoric acid.

Next, when the photoresist 8 is removed by etching, the kink shape 12 remains at the upper end portion of the taper 10 (see FIG. 1 (d)). Finally,
The entire silicon substrate 2 is heat-treated in nitrogen at 1100 ° C. for 2 hours. By this annealing, the damaged layer 6 is recovered, and the smooth taper 1 without the kink shape 12 is present.
4 are formed (see FIG. 1 (e)). The taper 14 formed at this time has a vertical / horizontal ratio of about 1/3 to 1/4 if the adhesion of the photoresist 8 is sufficiently good.

Although the thermal oxide film is used in the first embodiment, the CVD (chemical vapor depo) is used.
The same effect can be seen in the insulating film layer formed by the above-mentioned (condition), and at this time, since the forming temperature of the insulating film layer is low, the subsequent annealing temperature can be set low.

Further, the element used for the implantation is Ar + in the above embodiment, but it is possible to enhance the fluidity by simultaneously implanting P + (phosphorus) and B + (boron). The subsequent annealing conditions can also be made gentle. In addition, in this embodiment, for the sake of explanation, a process of forming a taper shape is used. However, in reality, the annealing process also serves as the next oxidation process, or
Impurities are implanted in the part where the thermal oxide film is selectively removed,
In the actual process, it is necessary to appropriately design the process so that the optimum process sequence is achieved, for example, annealing is also used to activate the impurities. As described above, according to the first embodiment, it is possible to eliminate the kink-shaped step at the upper end of the taper formed when the taper of the insulating film layer is formed by using the layer having a high etching rate formed by the method such as ion implantation. This makes it possible to form a smoother sectional shape.

Next, a second embodiment of the present invention will be described. 2A to 2E are cross-sectional views in which the method for forming the shape of the insulating film layer according to the second embodiment is applied to a semiconductor element. First, silane gas (Si
H ₄ ) and oxygen gas (O ₂ ) at 430 ° C., 0.2
A silicon oxide film layer 24 of about 1 μm is formed at torr (see FIG. 2A).

Next, silicate glass (OCD; registered trademark) manufactured by Tokyo Ohka Co., Ltd. is applied by spin coating,
Cure at a temperature of about 250 ° C. As a result, the silicate glass layer 26 having a high etching rate is formed (see FIG. 2B). Next, when the photoresist 28 is formed using the mask as a mask and chemical etching is performed, the etching rate of the large silicate glass layer 26 is higher than that of the silicon oxide film layer 24, so that the silicon oxide film layer 24 is selectively removed in a taper 30 shape. (See FIG. 1 (c)).

Next, the photoresist 28 and the silicate glass layer 23 are removed by etching. In this state, some kink shape 32 remains at the upper end of the taper 30. (See FIG. 2 (d)). Finally,
The entire silicon substrate 20 is heat-treated in nitrogen at 900 ° C. for 2 hours. This annealing forms a smooth taper 34 without the kink shape 32 (see FIG. 2).
(See (e)).

In the example shown in the second embodiment, since the silicate glass layer 26, which is a layer having a high etching rate, is removed by etching, the kink shape 32 above the taper 30 is formed.
Is not so large as in the first embodiment, but still exists.
Further, even if some debris is generated when the layer having a high etching rate is removed by etching, with this process configuration, the kink shape 32 is relaxed, so that the process stability can be increased. Even in this method, in order to make the shape of the upper end portion smoother, the silicon oxide film layer 24 is formed.
It is also possible to implant P + or B + or both on the surface of and then anneal. Regarding the design of the process sequence, etc., what has been described in the first embodiment,
Almost as it is, this embodiment is also applicable.

According to the second embodiment, when a taper is formed using a layer having a high etching rate, a high temperature treatment process is performed after the layer having a high etching rate is removed, so that the upper end of the taper is reduced. Not only is it smooth, but it is possible to mitigate kinking of the tapered cross-sectional shape due to etching residue when removing a layer with a high etching rate, so unnecessary over-etching can be avoided, improving processing accuracy after processing. It will also contribute to.

In the above-mentioned two embodiments, the taper shape is taken as an example for forming the shape of the insulating film layer, but it is obvious that other shapes have the same smoothing effect. is there.

[0020]

As described above, according to the invention of claim 1 and the invention of claim 2, various problematic profiles formed when the insulating film layer on the substrate is removed by etching are obtained. Further, it is possible to make it smoother, and it is possible to greatly improve the reliability of an element formed in a semiconductor process or an optical integrated circuit process.

[Brief description of drawings]

1A to 1E are cross-sectional views in which a method for forming a shape of an insulating film layer according to a first example is applied to a semiconductor device.

FIGS. 2A to 2E are cross-sectional views in which a method of forming a shape of an insulating film layer according to a second example is applied to a semiconductor element.

[Explanation of symbols] 2,20 Silicon substrate 4,24 Silicon oxide film layer 6 Damage layer 26 Silicate glass layer 8,28 photoresist 12,32 kink shape

Claims (2)

[Claims] 1. A step of forming an insulating film layer on a substrate, and a step of changing the etching rate of the insulating film layer in the thickness direction by implanting ions in the vicinity of the surface of the insulating film layer by a method such as ion implantation. A step of selectively removing the insulating film layer into a desired pattern by etching, and a step of processing at a temperature higher than the temperature required for forming the insulating film layer after these steps are included. A method for forming the shape of a characteristic insulating film layer. 2. A step of forming an insulating film layer on a substrate, and a step of forming a layer having an etching rate higher than that of the insulating film layer with respect to at least one etchant of the insulating film layer on the substrate. A step of selectively removing the insulating film layer and the high etching rate layer into a desired pattern by etching, and a step of removing the high etching rate layer by etching over the entire surface,
After these steps, a step of performing treatment at a temperature higher than the temperature required for forming the insulating film layer is included, and the method for forming the shape of the insulating film layer.