JPH081897B2 - Side etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In side etching in which the first layer is etched so as to enter the region of the second layer on the first layer from the exposed portion of the first layer, the second layer By making the light-transmissive material and exciting the etching gas in the etching part by light, it is possible to increase the side etching amount and reduce damage to the etching surface while still obtaining a clean and smooth surface. Is.

[Industrial applications]

The present invention relates to a method of side etching in which the first layer is etched so as to enter the region of the second layer on the first layer from the exposed portion of the first layer.

The etching is heavily used in a wafer process for manufacturing a semiconductor device, and the side etching, which is one of the processes, expands the degree of freedom in designing the semiconductor device and the like.

If the side etching amount can be increased, the above-mentioned degree of freedom in design can be further expanded.

[Conventional technology]

FIG. 3 is a side view illustrating an example of a conventional side etching method.

The side etching shown in the figure is the same as that shown in FIG.
A first layer 2 made of Si on a substrate 1 whose surface is made of Si ₃ N ₄ , and a second layer made of SiO ₂ having an opening 4 thereabove for exposing the first layer 2 3 in the first layer 2
Is subject to side etching by wet etching.

As the etching solution, KOH + H ₂ O that selectively etches Si with the above combination is used. The etching solution etches the first layer 2 through the opening 4 by a chemical reaction, and this etching is performed as shown in FIG.
To extend to the region of the first layer 2 from just below to achieve side etching.

FIG. 4 is a side view for explaining another conventional method example.

The side etching shown in the same figure is the same as in the case of the above-mentioned conventional method, in which the first layer 2 shown in FIG. 3 (a) is subjected to side etching, and dry etching using plasma generated by high frequency is performed, for example. It is performed by reactive ion etching (RIE).

As the etching gas, CCl ₄ that selectively etches Si with the above combination is used. The generated CCl ₄ plasma and the ions generated together pass through the opening 4 and etch the first layer 2 by the chemical reaction and the sputtering effect. This etching is performed immediately below the opening 4 as shown in FIG. To the area of the first layer 2 to achieve side etching.

[Problems to be solved by the invention]

However, in both of the above conventional method examples, the etching solution or plasma or the like performs the side etching through the opening 4, so that the etching rate increases as the side etching amount (depth that penetrates into the region of the first layer 2) increases. Is lowered, and the etching stops when reaching a certain size, so that there is a problem that the possible side etching amount is limited.

Further, in the former wet etching, the etching solution contaminates the contacted surface, and the etching surface of the first layer 2 becomes rough, and in the latter dry etching, the contamination or surface is contaminated. Although the surface is clean and smooth with less roughness, there is a problem that the etching surface of the first layer 2 is damaged by the above-mentioned sputtering effect.

[Means for solving problems]

The above problem is that the first layer is provided on the substrate, and then
A transparent second layer is provided on the first layer, and then,
An opening is provided in the second layer to expose the first layer,
Then, by irradiating the side etching region with light through the second layer to excite an etching gas for selectively etching the first layer, a side etching method for etching the first layer is performed. Will be resolved.

[Action]

It is known that the etching gas exhibits an etching action even when excited by light, and the action is a chemical reaction.

The present invention utilizes this phenomenon so that side etching can be effectively performed.

That is, since the second layer is translucent, the irradiation light for excitation reaches the side etching portion, so that the etching gas is continuously excited near the etching surface where the side etching is in progress.

Therefore, in the side etching in the case of this method, it is possible to maintain a substantially constant etching rate even when the side etching amount becomes large, and to make the side etching amount much larger than in the case of the conventional method described in the previous example. It is possible.

In addition, since the action of the excited etching gas in this case has no sputtering effect, the damage to the etching surface of the first layer is significantly smaller than that in the case of the conventional dry etching. Needless to say, the surface after etching is clean and smooth, as in the case of dry etching in the conventional method.

〔Example〕

An embodiment of the method of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a side view for explaining an embodiment, and FIG. 2 is a side view for a main part of an example of an apparatus for carrying out the embodiment. The same reference numerals denote the same objects throughout the drawings.

In the side etching shown in FIG. 1, the first layer 2 shown in FIG. 3 described in the conventional method is targeted for side etching. Here, the surface of the substrate 1 is Si ₃ N ₄ , the thickness of the first layer 2 made of Si is about 0.3 μm, the thickness of the second layer 3 made of SiO ₂ is about 0.1 μm, The size is about 0.3 μm square,
Is.

 Etching is performed as follows.

That is, in FIG. 1, the substrate 1 provided with the first and second layers 2 and 3 is placed in a Cl ₂ gas atmosphere having a pressure of about 20 Torr so that the temperature of the substrate 1 is always 100 ° C. . A mercury lamp that emits ultraviolet light having a wavelength of around 340 nm is irradiated with excitation light 5 composed of the ultraviolet light from the side of the second layer 3 at an energy density of about 200 mW / cm ² .

This operation can be performed by the device shown in FIG. 2, for example. In the figure, 11 is a vacuum chamber, 12 is a gas inlet for introducing an etching gas into the chamber 11, 13 is a gas exhaust port for reducing the pressure in the chamber 11 to a predetermined pressure, and 14 is the chamber 11 for holding the substrate 1. A susceptor to be placed, 15 is a heater incorporated in the susceptor 14 to keep the substrate 1 at a predetermined temperature, 16 is a window for keeping the vacuum of the chamber 11 and transmitting light 5, and 17 is a light source of light 5 (a mercury lamp). ),

Then, since the etching gas of Cl ₂ is excited by the light 5, the first layer 2 is selectively etched only while the light source 17 is turned on.

Here, the temperature of the substrate 1 is set to 100 ° C. in order to easily keep the temperature of the substrate 1 constant regardless of the irradiation of the light 5 in order to avoid the change of the etching rate due to the temperature change of the substrate 1. If you keep a constant temperature, it is 10
It does not have to be 0 ° C.

Then, the etching region enters the region of the first layer 2 from directly below the opening 4 and has a diameter of about 2.
It is approximately 4.3 μm after being lit for 10 minutes in a substantially circular shape of 3 μm.
Becomes

Therefore, in this side etching, it is found that the etching rate is maintained at about 0.2 μm / min, and it is also found that the side etching amount can be further increased by extending the lighting time.

The reason why the etching progresses so that the side etching amount becomes large is that the second layer 3 transmits the light 5 and therefore, as described above, the light 5 reaches the etching portion and the side etching is in progress. This is because the etching gas in the vicinity of the etching surface is continuously excited. In FIG. 1, the etching gas molecules, the excited etching gas molecules, and the gas molecules generated by the etching reaction are indicated by ◯, Δ, and □, respectively, in order to facilitate understanding of the state.

Further, when the material etched as described above was examined, the surface was clean and smooth, and no damage was found on the etched surface.

In the embodiment described above, the surface of the substrate 1, the first layer 2
And the materials of the second layer 3 are Si ₃ N ₄ , Si and SiO, respectively.
Was _2, but a combination of etching gas to selectively etch the first layer 2 and second layer 3 is present method if conditions are met for transmitting light 5 for exciting the etching gas It can be implemented.

Further, in the example, the second layer 3 has the openings 4, but it is easily understood that the method of the present invention is effective even if the second layer 3 has an arbitrary pattern shape. See.

〔The invention's effect〕

As described above, according to the configuration of the present invention, in the side etching in which the first layer is etched so as to enter the region of the second layer on the first layer from the exposed portion of the first layer, The etching amount can be increased, the damage on the etching surface can be reduced while a clean and smooth surface is obtained, and the degree of freedom in designing, for example, a semiconductor device can be increased.

[Brief description of drawings]

FIG. 1 is a side view illustrating an embodiment of the method of the present invention, FIG. 2 is a side view of an essential part of an apparatus example for performing the embodiment, FIG. 3 is a side view illustrating an example of a conventional method, and FIG. FIG. 6 is a side view illustrating an example of the conventional method of FIG. In the figure, 1 is a substrate, 2 is a first layer, 3 is a second layer,
4 is a hole, 5 is light for excitation, ◯ is etching gas molecule,
△ is an excited etching gas molecule, □ is a gas molecule generated by the etching reaction, 11 is a vacuum chamber, 12 is a gas inlet, 13 is a gas outlet, 14 is a susceptor, 15 is a heater, 16
Is a window and 17 is a light source.

Claims (1)

[Claims] 1. A step of providing a first layer on a substrate, a step of providing a transparent second layer on the first layer, and a step of forming an opening on the second layer. A step of providing a hole to expose the first layer, and then an etching gas for selectively etching the first layer by irradiating the side etching region with light through the second layer. And a step of etching the first layer while exciting the side etching method.