JPH0628256B2 - Semiconductor fine processing method and semiconductor fine embedded structure forming method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for performing fine etching processing of a semiconductor on a nanometer scale, and a method for forming a fine embedded structure by thin film deposition after the fine etching processing. INDUSTRIAL APPLICABILITY The present invention can be used for forming a semiconductor quantum wire structure and a quantum box structure which have been difficult to manufacture in the past.

(Prior Art) In recent years, by utilizing the physical properties of semiconductor quantum wells, research aiming at the development of devices with dramatically improved characteristics and completely new semiconductor devices has advanced, and semiconductor quantum well Attempts are being made to form thin wires and quantum boxes. In order to realize these structures, it is necessary to etch a semiconductor having a quantum well structure with a precision of nanometer (nm) scale, and then deposit a semiconductor thin film to completely embed the etched pattern. . N is the biggest technical issue for that
Aiming at the realization of etching with an accuracy of m scale, recently, instead of the photolithography method, a method of directly irradiating a semiconductor with a beam of light or charged particles to etch the irradiation portion has been actively researched. In the latter etching method, etching is usually performed by adsorbing an etching gas on the semiconductor surface and irradiating with a beam.

(Problems to be Solved by the Invention) In addition to using an etching gas in the above-mentioned etching by direct irradiation of a beam, an adsorption layer of an etching gas is used in order to avoid interface contamination before the subsequent microstructure embedding process. There is a problem that the process as a whole becomes a little complicated because a process for completely desorbing is required.

Most recently, attempts have been made to etch a semiconductor using laser light irradiation without using any etching gas. In this example, we use photo-induced desorption of the semiconductor,
Since there is no problem of etching gas diffusion, a processing size determined by the resolution of laser light irradiation has been realized. But,
Since the laser beam is used, the minimum etching size is only about several hundred nm, which is about the wavelength, and sufficient processing accuracy cannot be obtained to form the quantum wire and the quantum box structure. This etching of semiconductors using photoinduced desorption is described in Appl. Phys. Lett., Pp. 48, 1986, by Arnone, Rothschild and Ehrlich.
Vol. 11, No. 11, pp. 736-738. In the example of this paper, several hundred mW of A was added to a single crystal CdTe heated to about 300 ° C in a low vacuum of 10 ^-3 Torr.
rBy converging and irradiating laser light, an etching pattern with a width of about 500 nm and a depth of about 10 μm is formed.

In addition, in order to actually form quantum wires and quantum boxes, it is necessary to embed thin wires and box structures having a width and height of several nm to several tens of nm in a solid without interfacial contamination as described above. There is. However, a suitable method for embedding the above-mentioned fine etching pattern has not been studied so far.

An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional method, etch a semiconductor with an accuracy of several nm or less, and then deposit a thin film without contaminating the interface to form a fine embedded structure. To provide a simplified process method for.

(Means for Solving Problems) In order to solve the above problems, a semiconductor microfabrication method provided by the first invention of the present application is to irradiate a semiconductor heated to 200 ° C. or higher in vacuum with a focused electron beam. By doing so, the irradiation part is directly etched.

Furthermore, the method for forming a semiconductor fine embedded structure provided by the second invention of the present application is that after the semiconductor is irradiated with a focused electron beam in a vacuum, the irradiation part is directly etched by utilizing electron-induced desorption, It is characterized in that a thin film is formed on the semiconductor by chemical vapor deposition without exposing the semiconductor to the atmosphere even once.

(Operation) The etching according to the first and second inventions of the present application utilizes that the desorption phenomenon of the elements forming the semiconductor is caused by the irradiation of the semiconductor with the electron beam. AgBr,
It has been reported that, in many semiconductors such as CdS and CdTe, constituent elements are desorbed by non-thermal action when light or electron beam irradiation is performed under appropriate conditions. Since the energy of irradiated electrons is usually several hundred times to several hundred thousand times higher than that of photons, it is said that the former and the latter have different desorption mechanisms by irradiation. Although the mechanism of desorption is still unclear, several models such as Auger process and localization of multiple holes to a single bond have been proposed. In any case, the experiments of electron-induced desorption up to now have the purpose of confirming the phenomenon and understanding the mechanism, and whether or not high-speed etching processing at a practical level has been examined. The present invention is characterized in that electron induced desorption is remarkably enhanced by heating the semiconductor substrate to an appropriate temperature to enable high speed etching processing.

Although the etching processing of the semiconductor using the photo-induced desorption phenomenon has been described above, the etching using the electron-induced desorption according to the present invention enables the processing with an accuracy of several times the focused electron beam diameter. A fine pattern with a size of several nm can be formed. Therefore, according to the present invention, it is possible to perform a fine etching process sufficient to form a semiconductor quantum wire structure and a quantum box structure, which has been extremely difficult in the past.

Further, in order to actually form a quantum wire and a quantum box structure, it is necessary to deposit a semiconductor thin film or a dielectric film on the fine pattern obtained by the above-mentioned etching and completely fill the fine pattern. is there. In that case, it is necessary to suppress contamination of the interface between the fine pattern and the thin film to be deposited thereon as much as possible. This is because the target to be embedded is not only the problem of interface contamination but the fine pattern on the nm scale, and therefore the shape of the fine pattern itself may be changed even in a contaminant layer of about several atomic layers. Therefore, it is of course impossible to use a method of etching the entire semiconductor to be processed by several atomic layers after exposing it to the atmosphere once. Therefore, in the second invention of the present application, in order to prevent interface contamination, after the etching, the sample is not exposed to the atmosphere in the same container where the etching is performed, or the inside of the container where the etching is performed is changed to another container by a load lock mechanism. Transfer and perform thin film deposition. Further, chemical vapor deposition (CVD) is used for thin film deposition in order to uniformly and completely embed fine patterns by etching.
Use the method.

(Embodiment) Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram schematically showing a configuration of an apparatus for performing etching processing and CVD in the first and second inventions of the present application. Since the first invention of the present application is used for the second invention of the present application, the embodiments of both inventions of the present application will be described below together. A semiconductor 11 to be processed (hereinafter referred to as a semiconductor sample) is fixed on a heater 21 and placed in a chamber 31. The electron beam 41 is generated by the electron gun 42, in which case the exhaust pump with the valve 51 closed.
The chamber 31 is evacuated to a high vacuum by 32. The sequencer 43 controls the energy, intensity and scanning of the electron beam 41,
It also has a function of processing a signal from the secondary electron detector 44 and observing a scanning electron microscope image on the monitor 45. The electron-induced desorption etching of the semiconductor sample 11 by the irradiation of the electron beam 41 occurs by heating the semiconductor sample 11 to an appropriate temperature with the heater 21. In order to form a fine pattern by etching, first, the scanning electron microscope image is observed without heating the semiconductor sample 11, the place where etching is desired is determined, the scanning place of the electron beam 41 at the time of etching, energy, beam diameter, The beam intensity and scanning speed are set by the sequencer 43. Subsequently, the semiconductor sample 11 is heated to a designated temperature and irradiated with the electron beam 41 under the set conditions.

Next, in order to deposit a thin film by CVD on the semiconductor sample 11 on which the fine etching process has been completed, an electron beam is used.
With the generation of 41 stopped, the semiconductor sample 11 is heated to an appropriate temperature, the valve 51 is opened, and the reactive gas as the raw material of the thin film is introduced into the chamber 31 through the reactive gas inlet 52.
At this time, by operating the exhaust pump 32 and controlling the supply amount of the reactive gas, the internal pressure of the chamber 31 and the deposition rate of the thin film can be controlled.

The semiconductor sample having the quantum well structure is shown in FIG.
41 schematically shows the etching process.
The arrow 104 indicates the scanning direction of the electron beam 41. This figure (a) shows a state in which the single quantum well layer 101 and the barrier layer 102 sandwiching the single quantum well layer 101 are finely etched by linearly scanning the electron beam 41 at appropriate intervals. The width and depth etched by one scan are the material of the semiconductor sample, the energy of the electron beam 41, the beam diameter,
It depends on the beam intensity and scanning speed. FIG. 2B shows how the box-shaped etching pattern 105 is formed by scanning the electron beam 41 in the vertical direction of the fine linear etching pattern 103 of FIG.

3 (a) and 3 (b) are respectively FIG. 2 (a) and
The thin linear etching pattern 103 and the box-shaped etching pattern 105 shown in (b) are deposited by embedding a thin film having the same composition as the barrier layer 102 to form a quantum wire 201 and a quantum box 202 structure. ing. If the depth of etching by electron beam is on the order of tens of nm, the etching pattern is completely filled by depositing a thin film to a thickness of several hundreds nm by CVD, and the surface after the thin film deposition is almost completely flat. Become.

In the present embodiment, as the semiconductor sample 11, undoped (10
10n on a β-type zinc sulfide (ZnS) substrate cut out on the (0) plane
An undoped zinc selenide (ZnSe) quantum well layer having a thickness of m and an undoped ZnS layer having a thickness of 10 nm epitaxially grown thereon were used. When performing the etching process, the electron beam 41 should be applied at a vacuum degree of 10 ^-8 Torr or less.
Energy 25keV, beam diameter 10nm, beam current 100
The semiconductor sample 11 heated to 300 ° C. was scanned at a speed of 10 μm / s so as to obtain pA. Under these conditions, processing with an etching depth and an etching width of 30 nm could be performed. By scanning the electron beam 41 in parallel at intervals of 40 nm, a fine linear etching pattern 103 having a width of 10 nm and a height of 30 nm was obtained. Also this fine linear etching pattern 1
By scanning the electron beam 41 in a direction perpendicular to 03 in parallel with an interval of 40 nm, one side of the upper surface is 10 nm and the height is 30 nm.
A box-shaped etching pattern 105 was obtained. These etchings were performed over an area of 10 μm × 10 μm.

The embedding of the etching pattern was performed by CVD of the ZnS thin film while the semiconductor sample 11 after etching was heated to 400 ° C. Immediately after the irradiation of the electron beam 41 was stopped, the valve 51 was opened and dimethylzinc (DMZn) and hydrogen sulfide (H ₂ S) were introduced through the reactive gas inlet 52 at a molar ratio of 1: 1.
It was supplied into the chamber 31 at 0, and the flow rate was controlled so that the total pressure was 10 ^-2 Torr. Under this condition, the growth rate of ZnS thin film is 3
Although it was 00 nm / hour, in the example, it was grown to a thickness of 500 nm.

In order to confirm that the quantum wire 201 or the quantum box 202 was formed as expected in the sample manufactured by the above procedure, the peak position of exciton emission was examined using low temperature photoluminescence. 6.5k sample
Then, the sample was irradiated with an ultraviolet laser beam of about 100 μw in the vicinity of 360 nm obtained from an Ar ion laser, condensed to a diameter of 10 μm. Luminescence was collected and then received by a photomultiplier through a spectroscope. As a result of the measurement,
The luminescence due to excitons in the quantum well portion where the quantum wire and the quantum box are not formed has been found to have a peak position at 2.75 eV. On the other hand, the photoluminescence exciton peak of the portion where the fine line pattern was provided was at an energy position of about 2.7 eV, and it was found that the exciton peak moved to the low energy side as the width of the fine line pattern decreased. The exciton peak of photoluminescence in the box-shaped pattern is about 2.
It is located at the energy position of 6 eV, and in this case as well, it was found that the exciton peak moved significantly to the low energy side as the box size decreased.

The change in exciton peak position of the photoluminescence spictol is due to the increase in exciton binding energy due to the increase in quantum confinement effect, which is interpreted as a sign that a quantum wire or quantum box is formed.

Moreover, when the photoabsorption spectrum was measured instead of photoluminescence, the absorption spectrum shape on the high-energy side of the exciton peak was almost the same as the energy in the case of the quantum well structure, in addition to the similar tendency of the exciton peak position change. It was confirmed that in the case of the fine line and the box-shaped structure, the absorption decreased toward the high energy side and showed a more remarkable decrease with the decrease of the fine line width and the size of the box, as compared with the case where the fine line and the box-shaped structure did not show. This phenomenon is also interpreted as a sign of the formation of quantum wires and boxes.

In the above-described embodiment, in order to form the ZnSe / ZnS quantum wires and quantum boxes, the ZnSe / ZnS quantum well sample was etched, and further ZnS CVD was performed. However, the present invention is not limited to this material system and can be widely applied to many kinds of semiconductor materials of II-VI group and I-VII group. In order to perform desired etching for each material, the electron beam energy, intensity, beam diameter, and scanning speed may be appropriately selected. Regarding the size of the etching process, in the above-mentioned embodiment, the electron beam diameter was set to 10 nm and
Although the etching with a width of nm is performed, the electron beam diameter is sub-n
Since it can be made as small as m, it is clear that further miniaturization is possible. It is needless to say that different types of thin films deposited by CVD can be deposited by changing the type of gas supplied. Further, in the above-described embodiment, in order to prevent surface contamination of the sample after etching, etching and C
Although performed in the same chamber as the VD, the CVD may be performed after the sample is transferred to another chamber by the load lock mechanism after etching.

(Effects of the Invention) As described above, by using the present invention, it becomes possible to perform fine etching processing of a semiconductor on a nm scale by a very simple process, and further form a fine embedded structure after etching processing. It becomes possible. As a result, it becomes possible to provide devices with dramatically improved characteristics and semiconductor devices that are completely new compared to conventional ones.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an apparatus for performing etching processing and CVD in the first and second inventions of the present application. Further, FIG. 2 is a diagram schematically showing a state where a semiconductor sample having a quantum well structure is applied with the first invention of the present application and is etched into a fine line shape or a box shape by an electron beam. Furthermore, FIG. 3 is a schematic diagram showing a semiconductor quantum wire and a quantum box structure formed by depositing a semiconductor thin film by the CVD according to the second invention of the present application on a semiconductor sample after being etched by an electron beam. 11 …… Semiconductor sample, 21 …… Heater, 31 …… Chamber, 32
...... Exhaust pump, 41 …… Electron beam, 42 …… Electron gun, 43
…… Sequencer, 45 …… Monitor, 51 …… Valve, 52 ……
Reactive gas inlet, 101 ... Quantum well layer, 102 ... Barrier layer, 103 ... Fine linear etching pattern, 104 ... Electron beam scanning direction, 105 ... Box-shaped etching pattern, 201 ...
Quantum wire, 202 ... Quantum box.

Claims (2)

[Claims] 1. A semiconductor microfabrication method, which comprises directly irradiating a irradiated portion with a focused electron beam to irradiate a semiconductor heated in a vacuum at 200 ° C. or higher. 2. A semiconductor is chemically etched on a semiconductor without exposing the semiconductor to the atmosphere even after directly exposing the irradiated portion by utilizing electron-induced desorption by irradiating the semiconductor with a focused electron beam in a vacuum. A method for forming a semiconductor fine embedded structure, which comprises forming a thin film by dynamic vapor deposition.