JPH0559577A - Fine working method - Google Patents

Abstract

PURPOSE:To provide the three-dimensional fine working method of a high speed and low damages. CONSTITUTION:A resist film 2 is formed on a substrate 1 to be worked and thereafter, the resist film 2 is subjected to ion implantation, by which a reforming distribution is provided in the resist film 2. The reformed resist film 2 is then ashed, by which the surface of the resist film 2 is worked to a curved surface meeting the reforming distribution and thereafter, the substrate 1 and the resist film 2 are simultaneously etched. The shape meeting the surface shape of the resist film 2 is thereby formed on the substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine processing method for processing a minute three-dimensional curved surface shape required in micromachining and the like.

[0002]

2. Description of the Related Art In micromachining or the like, for example, when forming a microlens, a groove of an electrostatic precession motor, or the like, a focused ion beam etching method is used as a method for forming a minute three-dimensional curved surface on a substrate to be processed. It has been known.

In this method, the focused ion beam is locally applied to the processed portion of the substrate to be processed. The substrate material to be processed reacts with incident ions physically or chemically and is etched. At this time, the irradiation position of the ion beam is scanned, but a portion having a large processing amount (etching amount) is irradiated with a high-intensity beam for a long time to form a desired three-dimensional curved surface.

[0004]

In the above three-dimensional curved surface processing method, the substrate material is directly etched by the focused ion beam. In the case of physical etching, that is, sputter etching of a substrate material by incident ions, the processing speed depends on the number of sputtered atoms per incident ion, that is, the sputter rate. The sputter rate cannot be unequivocally stated because it greatly changes depending on many parameters such as the type and energy of incident ions and the substrate material to be processed, but it is several tens or less even under the best conditions. Therefore, it is necessary to irradiate with a processing amount, that is, an ion amount of 1 / several tens of the number of atoms removed by etching. Therefore, considering that it is difficult to improve the amount of implanted ions per unit time of the focused ion beam apparatus, that is, the ion current value, there is a problem that a long time is required for processing.

Further, sputter etching cannot avoid damage to the substrate to be processed, and there is a concern that device characteristics will be adversely affected. The present invention solves such problems, and an object thereof is to provide a high-speed, low-damage three-dimensional microfabrication method.

[0006]

In order to achieve the above object, the fine processing method of the present invention comprises: (a) a step of forming a film on a substrate to be processed; and (b) an ion for the film. And (c) processing the surface of the film into a curved surface according to the modified distribution by etching the modified film by performing implantation, and (c) etching the modified film. And (d) a step of simultaneously etching the substrate and the film to form a shape corresponding to the surface shape of the film on the substrate.

The step (a) is a step of forming a resist film on the substrate to be processed, and the step (b) is a step of controlling the hardness of the resist film by mainly controlling the ion implantation amount distribution. The step of providing a distribution may be performed, and the step (c) may be a step of ashing the resist film.

Further, the step (a) is a step of forming a silicon film on the substrate to be processed, and the step (b) is mainly for controlling the implantation energy distribution of the ion implantation to remove impurities in the silicon film. It may be a step of giving distribution to conductivity type or concentration.

[0009]

[Operation / Effect] According to the above-described processing method, when ions are implanted into the film formed on the substrate to be processed, the implantation dose distribution or implantation energy distribution of the ion implantation is controlled, and accordingly A spatial distribution occurs in the degree of modification of the film. After that, by etching the modified film, the surface of the film is processed into a curved surface according to the modified distribution, and further, by simultaneously etching the substrate and the film, the shape according to the surface shape of the film becomes a substrate. Formed in. Here, since the amount of ion implantation required for modifying the film may be much smaller than that in the case of directly etching the substrate with the conventional ion beam, the time required for the processing is significantly reduced. Further, since the substrate is not directly etched by sputter etching, there is no damage to the substrate to be processed and there is no adverse effect on the device characteristics formed on the substrate.

For example, a resist film can be given a hardness distribution by forming a resist film on a substrate to be processed and then mainly controlling the distribution of ion implantation amount. That is, the resist film has a property of hardening as the amount of ion implantation increases, and by utilizing this property, the hardness distribution can be provided. After that, when the resist film is ashed, the ashing rate of the resist film becomes smaller as the hardening progresses, so that the resist film is processed into a curved surface according to the hardness distribution.

In addition, a silicon film is formed on the substrate to be processed,
After that, by mainly controlling the implantation energy distribution of the ion implantation, it is possible to give the conductivity type or the concentration of the impurity in the silicon film. Therefore, the silicon film is processed into a curved surface according to the implantation energy distribution by etching with an etchant capable of selectively etching the region where the conductivity type or the concentration of the impurities is different from the original silicon film.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A microfabrication method of an embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 (a) to 1 (c) are sectional views for explaining a microfabrication method in an embodiment of the present invention in the order of steps. In the figure, the substrate 1 to be processed is a single crystal Si substrate,
Alternatively, it is made of a glass substrate or the like, and in the present embodiment, single crystal S
i substrate is used. A resist film 2 is applied on the main surface of the substrate 1. Although a general photoresist film can be adopted as the resist film 2 used here, for example, as a negative resist film, IC43T-3 (trade name, manufactured by Fuji Hunt Co., Ltd.), SC-900, -450. ,-
100 (trade name, both manufactured by Fuji Hunt Co., Ltd.), 1300, 1400 (trade name, both manufactured by Shipley Co., Ltd.) and the like can be adopted as the positive type resist film.

Then, in the step of FIG. 1A, phosphorus ions are implanted into the resist film 2 by a focused ion beam device. At this time, the implantation energy is fixed, for example, and the beam is scanned while changing the implantation time and the ion current value to change the implantation ion amount. The resist film 2 is modified, that is, hardened by implanting phosphorus ions, and the degree of hardening increases as the amount of implanted ions increases. In this example, the injection amount is controlled so that the degree of cure of the peripheral portion is higher than the degree of cure of the central portion. Next, in the step of FIG. 1B, the substrate is put into an ashing chamber, and the resist film 2 is ashed (ashing) in the presence of oxygen plasma. The ashing rate of the resist film 2 becomes smaller as the curing progresses. Therefore, in this example, the ashing of the central portion progresses preferentially, the central portion is etched more than the peripheral portion, and a curved surface dented from the peripheral portion toward the central portion is formed. If the ashing process is interrupted at an appropriate place, for example, when the ashing of the central portion progresses and the substrate material is exposed for the first time, the resist film 2 is formed in the state shown in the figure.
Will remain.

Next, in the step of FIG. 1 (c), the substrate is placed in an etching chamber, a mixed gas of CF4 gas and oxygen gas is introduced, and plasma treatment is performed. The CF4 gas mainly serves as an etchant raw material of Si which is the material of the substrate 1, and the oxygen gas serves as an etchant raw material of the resist film 2. Therefore, when etching is performed in the presence of plasma of these mixed gases, the etching of the substrate 1 and the resist film 2 proceeds simultaneously. Here, the etching rate ratio of the substrate 1 and the resist film 2 can be arbitrarily controlled by changing the mixing ratio or pressure of the mixed gas. In this example, the etching rates of both are set to be equal, and constant-rate etching is performed. As a result, the three-dimensional curved surface shape of the resist film 2 formed in the previous step is directly transferred to the substrate 1.

Therefore, according to the present embodiment, the resist film 2 is formed on the substrate 1, and then the distribution of hardness is imparted to the resist film by mainly controlling the distribution of the amount of ion implantation. Since the resist film 2 is ashed and the resist film 2 is processed into a curved surface according to the hardness distribution, the substrate 1 and the resist film 2 are simultaneously etched to process the substrate 1, so that the resist film 2 can be modified. The required ion implantation amount is much smaller than that in the case of directly etching the substrate with the ion beam of the conventional technique (1/1 of the conventional technique).
(100 to 1/1000), the time required for processing can be significantly reduced. Further, since the substrate is not directly etched by sputter etching, there is an effect that the substrate 1 is not damaged and the device characteristics formed on the substrate 1 are not adversely affected.

Next, a microfabrication method in another embodiment of the present invention will be described in the order of steps with reference to the sectional views shown in FIGS. In the figure, the substrate 10 to be processed is made of a single crystal Si substrate, a glass substrate, or the like. In this embodiment, a glass substrate is used. An n-type polycrystalline silicon film 20 is formed on the main surface of substrate 10 by a vapor growth method.

In the step of FIG. 2 (a), the focused ion beam apparatus is used for the n-type polycrystalline silicon film 20 to
Boron ions, which are p-type impurities, are selectively implanted. At this time, the beam is scanned while changing the implantation ion energy. The n-type polycrystalline silicon film 20 becomes p-type by implanting boron ions, and the depth of the p-type layer increases as the implanted ion energy increases. In this example,
The implantation energy is controlled so that the central portion is deeper than the peripheral portion.

Next, in the step of FIG. 2 (b), electrochemical etching with a KOH solution is performed while applying a positive potential to the substrate 10. The etching rate of the p-type layer in the polycrystalline silicon film 20 is several tens of times that of the n-type layer, and only the p-type layer is selectively etched, leaving only the n-type layer, that is, the layer into which no impurity has been implanted. Therefore, the central portion is etched more than the peripheral portion, and a curved surface that is recessed from the peripheral portion toward the central portion is formed.

Next, in the step of FIG. 2 (c), the same substrate is placed in an etching chamber and a mixed gas of CF4 gas and hydrogen gas is introduced. Due to the CF4 plasma, SiO2 and Si, which are the materials of the substrate 10, are simultaneously etched. Further, the etching rate ratio of SiO2 and Si can be controlled by the mixture ratio of hydrogen gas. In this example, the etching rates of both are set to be equal, and constant-rate etching is performed. As a result, the three-dimensional curved surface shape of the polycrystalline silicon film 20 formed in the previous step is directly transferred to the substrate 10.

Therefore, according to the present embodiment, the n-type polycrystalline silicon film 20 is formed on the substrate 10, and then the implantation energy distribution of the ion implantation is mainly controlled to control the impurities in the polycrystalline silicon film 20. By changing the conductivity type to p-type so as to have a distribution in the n-type region and the p-type region, and selectively etching the p-type region, the polycrystalline silicon film 20
Is processed into a curved surface according to its distribution, and the substrate 10 and the polycrystalline silicon film 20 are simultaneously etched to process the substrate 10. Therefore, similar to the above-described embodiment, the polycrystalline silicon film 20 can be modified. The required ion implantation amount is much smaller than that in the case of directly etching a substrate with an ion beam of the conventional technique (1/100 to 1 of the conventional technique).
/ 1000), the time required for processing can be significantly reduced.
Moreover, since the substrate is not directly etched by sputter etching, there is an effect that the substrate 10 is not damaged and the device characteristics formed on the substrate 10 are not adversely affected.

Although the p-type region distribution is formed in the n-type polycrystalline silicon film 20 in the present embodiment, the n-type region distribution is formed in the p-type polycrystalline silicon film. Alternatively, a hydrofluoric acid-based etching solution may be used as the etching solution in FIG. 2B. Moreover, the n-type polycrystalline silicon film 2 is formed by ion implantation.
The n + region distribution with a high impurity concentration may be formed without changing the conductivity type of 0. In that case, the etching may be performed by wet etching as the etching in FIG. 2B.

Further, instead of the polycrystalline silicon film 20, an amorphous silicon film or a single crystal silicon film may be used. In short, when etching is carried out after ion implantation, a region where ions are implanted and a region where they are not implanted are used. It suffices if the etching selection ratio can be obtained in the interval.

[Brief description of drawings]

1A, 1B and 1C are cross-sectional views for explaining a microfabrication method in an embodiment of the present invention in the order of steps.

2 (a), (b) and (c) are sectional views for explaining a microfabrication method in another embodiment of the present invention in the order of steps.

[Explanation of symbols]

 1 substrate 2 resist film 10 substrate 20 polycrystalline silicon film 20

Claims (3)

[Claims] 1. (a) a step of forming a film on a substrate to be processed; (b) a step of providing a modified distribution in the film by performing ion implantation on the film; (c) By etching the modified film,
A step of processing the surface of the film into a curved surface corresponding to the modified distribution; and (d) a step of simultaneously etching the substrate and the film to form a shape corresponding to the surface shape of the film on the substrate. And a microfabrication method. 2. The step (a) is a step of forming a resist film on a substrate to be processed, and the step (b) is a step of controlling the implantation amount distribution of ion implantation to control the hardness of the resist film. The microfabrication method according to claim 1, wherein the step (c) is a step of ashing the resist film. 3. The step (a) is a step of forming a silicon film on a substrate to be processed, and the step (b) is a step of controlling impurities in the silicon film mainly by controlling an ion implantation energy distribution. 2. The microfabrication method according to claim 1, which is a step of giving a distribution to the conductivity type or the concentration of.