JPS59213135A - Fine processing for semiconductor - Google Patents

Abstract

PURPOSE:To realize a fine processing method for semiconductors, which effects a superior processing precision and facilitates the control of processing form, by a method wherein an ion implantation with a concentration, which is formed by an amorphous substance, is performed in regions in the surface of a substrate and then only crystal growth regions just above the ion-implanted regions in the substrate are selectively removed by performing an etching treatment on an crystal growth layer formed on the surface of the substrate. CONSTITUTION:Ions 3 are previously implanted in regions 2, where oppose to positions to be performed a processing on a crystal growth layer 6 on the surface of a substrate 1, whereon the crystal growth layer 6 is to be formed, and after the prescribed amount of ion-implantation was completed, the crystal growth layer 6 is formed on the surface of the substrate 1 by a molecular beam crystal growth method. After the crystal growth layer 6 of a prescribed thickness was formed by the molecular beam crystal growth method, the crystal growth layer 6 is performed an etching treatment by using a selective etching solution. By appropriately selecting the etching solution, the treating time, etc., only the crystal growth regions just above the ion-implanted regions in the substrate 1 are preferentially etched, removed and apertures 8 are formed.

Description

[Detailed description of the invention] The present invention relates to a semiconductor microfabrication method.

With the development of optical communication and optical information processing technology, there are hopes for the realization of opto-electronic integrated circuits in which groups of various optical elements and electronic elements are integrated on the same substrate in thousands of ways, instead of the conventional single optical elements and electronic elements. ing.

In realizing this opto-electronic integrated circuit, various parties, collaboration between electronic micro elements, laser resonator mirror creation,
Semiconductor microfabrication technology is indispensable in the creation of optical branches and branching channels, streamlining the manufacturing process, improving the performance of each element,
Microfabrication technology will have a major impact on reliability.

Wet or dry etching methods using patterns formed by beam lithography have been known as semiconductor microfabrication techniques to date, but it is difficult to control the depth of etching, and etching also occurs on the sides. This progressed, making it difficult to form fine patterns accurately. Furthermore, when a semiconductor substrate is directly etched using a dry etching method or a focused ion beam, the processed surface is damaged by plasma or ion irradiation, and the damaged portion must be removed or annealed.

An object of the present invention is to provide a semiconductor microfabrication method with excellent processing accuracy and easy control of the processed shape.

Therefore, in the semiconductor microfabrication method according to the present invention, ions are implanted at a concentration that forms an amorphous material in a substrate surface area corresponding to the position where the crystal growth layer is to be processed on the substrate surface where the crystal growth layer is to be formed. Next, a whip-crystal growth layer is formed on the surface of the substrate, and the formed crystal growth layer is etched to selectively remove only the crystal growth region directly above the ion implantation region of the substrate. .

In this way, since the crystal growth region directly above the ion implantation region of the substrate is polycrystalline, the etching speed is significantly faster than that of a single crystal, and therefore, the etching process can be performed accurately and quickly to the ion implantation region of the substrate. Can be done. Furthermore, since the lateral spread of etching is suppressed by the single crystal region of the crystal growth layer, fine patterns can be precisely etched, and parts of the substrate damaged by ion irradiation can also be removed.

Next, the present invention will be explained with reference to FIG. 1. Ions 3 are implanted in advance into a region on the surface of the substrate 7 where the crystal growth layer 6 is to be formed, corresponding to a position to be processed into the crystal growth layer. The substrate 1 includes not only a semi-insulating substrate crystal such as GaAs but also a growth layer formed on the substrate crystal. A known ion implantation method can be used for the above-mentioned ion implantation, and the ion concentration to be implanted is such that a large amount of ion irradiation damage is formed in the ion implantation region, and at least amorphous clusters are formed at a high density. degree, specifically I
Requires approximately 1016♂ or more. The ion species used include Bg ions, h ions, and uniform ions, but ion species with a large mass number are more effective. In addition, the acceleration energy is a number of 10, which is used in normal ion implantation.
It can be suitably used in the range of KgV to several 100 KgV,
It may exceed I MgV. Although it is effective at about 10 KgV, as the acceleration energy decreases, the sputtering effect due to incident ions becomes more pronounced and the effect decreases.

The ion implantation method is a maskless ion implantation method in which a predetermined region of the substrate is directly irradiated with an ion beam 3 focused on the order of submicrons as shown in FIG. 1, or a maskless ion implantation method as shown in FIG. As shown in the figure, an implantation mask such as 8401 thin film is applied to the substrate l, a predetermined pattern 5 is drawn with the resist thin film, and the ion beam 3 is irradiated to implant the ions 3 into a predetermined area of the substrate. You can also do it.

As described above, when a predetermined amount of ions have been implanted into the substrate region corresponding to the position where the crystal growth layer to be formed on the substrate is to be processed, the crystal growth layer 6 is formed on the substrate surface by molecular beam crystal growth. (Figure 3). The crystal growth temperature may be the commonly used 500°C to 750°C, but if it is too high, the substrate will have the effect of being annealed.
Relatively low temperatures give better results.

When a crystal growth layer is formed on the substrate in this way, the ion-implanted region λ of the substrate is not a single crystal, but a high-density amorphous layer formed due to damage caused by a large amount of ion irradiation. Since high-density defects remain during crystal growth, the crystal growth region 7 that grows directly above the ion implantation region is not a single crystal but a polycrystal.

After the crystal growth layer 6 of a predetermined thickness is formed by the molecular beam crystal growth method, the crystal growth layer 6 is then etched using a selective etching solution. This etching process can be carried out by a known method, and by appropriately selecting the etching solution, processing time, etc., only the crystal growth region 7 directly above the ion implantation region λ of the substrate is etched away, without ion implantation. The crystal growth region formed on the region shows almost no reduction due to etching. This is because the crystal growth region directly above the ion implantation region is polycrystalline as described above, so the etching rate is much higher than that for single crystal, and as a result, only the crystal growth region directly above the ion implantation region is etched preferentially. It is removed to form an opening (Fig. 4). At this time, the lateral spread of the etching is naturally prevented by the single crystal region, so that only a predetermined region is precisely etched to the substrate.

Of course, by controlling the etching conditions, it is also possible to perform the etching process to the ion implanted region on the substrate and remove the damaged region caused by the ion implantation.

In the above, we explained how to remove the crystal growth region formed directly above the ion implantation region of the substrate using the wet etching method, but since the growth region formed on the ion implantation region is polycrystalline, the etching method is The method is not strictly limited, and dry etching methods using a reactive gas such as organic sputtering or Oat4 gas can also be used.

As is clear from the above description, in this invention, before the growth layer is formed, a significant amount of ions are implanted into the region of the substrate corresponding to the processed portion of the growth layer to make it amorphous, and then crystal growth is performed. Therefore, the growth region formed on the above region becomes polycrystalline and can be selectively removed by etching, and the depth of etching is determined by the thickness of the crystal growth layer, making it easy to control. The region is limited to just above the ion implantation region, and lateral etching is suppressed, so that accurate etching can be performed. Particularly when performing fine etching on the order of submicrons, it is sufficient to draw the pattern directly on the substrate using an ion beam focused on submicrons, without the need for other processes such as transfer and alignment. Therefore, the crystal growth layer can be etched extremely easily and accurately. Therefore, good results can be obtained in microfabrication of semiconductors grown at relatively low crystal growth temperatures. Furthermore, GaAs/
This invention can also be used for etching when forming an AAGαA8 heteroepitaxial layer.
This will greatly contribute to the microfabrication of semiconductors such as opto-electronic integrated circuits.

Next, embodiments of this invention will be described.

Using a GaAs layer crystal-grown on an Or-doped semi-insulating GaAs crystal as a substrate, a Be ion beam focused to a diameter of 0.1 μm was applied to a predetermined area on the surface of the GaAs layer.
160 K at room temperature with a concentration of X 10"cy++-"
After implantation with acceleration energy of gV, a GaAa crystal growth layer with a thickness of 2.5 μm was further formed on the GaAs crystal growth layer substrate by molecular beam growth. Crystal growth temperature is 60
The temperature was 0°C. Next, this GaAa crystal growth layer is heated with HF:
Etching was performed using an etching solution with a mixing ratio of H2O,:I(,0) of 1:1:10.The etching time was 30 seconds, and the GaA3 crystal growth region immediately above the ion implantation of the substrate was completely etched away. The GaA8 crystal growth region other than directly above the ion implantation region showed almost no reduction due to etching, and the etching was formed by etching the width of the ion implantation region.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment for implementing the method of the present invention, FIG. 2 is a perspective view showing another embodiment for implementing the method of the present invention, and FIG. 3 is a perspective view showing another embodiment for implementing the method of the present invention. FIG. 4 is a cross-sectional view showing a state in which a crystal growth layer is formed on a substrate by the method, and FIG. 4 is a cross-sectional view of a semiconductor after being etched according to the present invention. l...substrate crystal, co...ion implantation region, 3...
ion, 6... crystal growth layer, 7... polycrystalline region, za... opening.

Claims (1)

[Claims] Ion implantation is performed at a concentration that forms an amorphous substance in a region of the substrate surface corresponding to a position where the crystal growth layer is to be processed on the substrate surface where the crystal growth layer is to be formed, and then a crystal growth layer is formed on the substrate surface. A semiconductor microfabrication method characterized in that the formed crystal growth layer is etched to selectively remove only the crystal growth region immediately above the ion implantation region of the substrate.