JPS6142127A - Ion beam irradiation method - Google Patents

Abstract

PURPOSE:To accurately irradiate the specified position with ion beam by obtaining the center point of groove pattern with the secondary electrons emitted from the inclined surfaces at both side walls of groove pattern of marker and using it as the reference point of ion beam irradiation. CONSTITUTION:A groove pattern 2 with the side walls 3 formed as the inclined surfaces is formed as the marker at the surface of substrate 1 with the wet etching, etc. and when the surface of substrate 1 is scanned with the focused ion beam 4 in such a way as crossing the groove pattern, the secondary electrons 5 can be emitted from the substrate. Since the ion implantation depth at the inclined surface 3 becomes equivalently smaller than that at the surface, the emission of secondary electrons remarkably increases. When the inclined surface 3 of groove pattern 2 is scanned with ion beam on the occasion of measuring such emitted secondary electrons 5 with a secondary electron intensity measuring apparatus, signal is intensified several times than that at the flat area and it can be displayed as the peak 6a.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an ion beam irradiation method in a maskless ion implantation method in which impurity ions are directly implanted into a semiconductor substrate using a focused ion beam on the order of submicrons. be.

<Prior art> Molecular beam crystal growth method and mask are used as a method for monolithically integrating optical devices such as lasers, light emitting diodes, photodetectors, and electronic devices such as various transistors and diodes on semiconductor substrates such as gallium arsenide. A process combining less ion implantation is seen as promising.

Maskless ion implantation is a method of directly doping impurity ions into a semiconductor substrate while freely scanning an impurity ion beam focused to a submicron diameter, and it does not require complicated mask creation, alignment, mask removal, etc. It has the characteristics of a process. In order to manufacture highly precisely integrated devices with good reproducibility using this maskless ion implantation method, it is essential to accurately irradiate a predetermined position with a focused ion beam. However, in electron beam exposure, although a method for determining the position to be irradiated with an electron beam has been known, a method for determining the position to be irradiated with an ion beam has not been known.

A common method for determining the irradiation position of the electron beam is to form a cross-shaped groove as a marker by etching or other means at a position on the surface of the semiconductor substrate where no device will be created.
The marker position is detected and recorded by signal processing of the secondary electrons emitted by multiple scanning of the substrate surface with an electron beam, and the electron beam is irradiated using this as a reference point.

<Problems to be solved by the invention> Shikashi, maskless ion implantation uses a focused ion beam on the order of submicrons, so a reference point is determined by applying the electron beam irradiation position determination method, and the ion beam When irradiating an ion beam, the width of the groove in the pattern formed as a marker must be made extremely narrow in order to accurately irradiate a predetermined position with the ion beam. However, it has been difficult to form markers with such narrow patterns. Especially in recent years, in order to miniaturize devices and manufacture devices with good reproducibility, even in electron beam exposure technology, the method for determining the beam irradiation position described above is no longer satisfactory, and methods for irradiating the beam to even more accurate positions are being developed. development was desired.

The present invention has been made in view of the above, and an object of the present invention is to provide an ion beam irradiation method in a maskless ion implantation method that can irradiate a semiconductor substrate with an accurately focused ion beam at a predetermined position.

<Means for Solving the Problem> In order to achieve the above object, in the present invention, a groove pattern with sloped side walls is formed on a semiconductor substrate as a marker, and an ion beam is scanned across the groove pattern. measure the secondary electrons emitted from the slope, detect the peak positions of the secondary electron signals emitted from the above-mentioned slope, and find the center point between the two peak positions from the above-mentioned two peak positions. The method is characterized in that the semiconductor substrate is irradiated with the ion beam using the obtained center point as a reference point for ion beam irradiation.

Next, the present invention will be explained based on an embodiment shown in the drawings. L is a semiconductor substrate, and etching or the like is performed at a position on the surface of the substrate where no device is to be formed to a depth of 1 as a marking force.
A groove pattern with a width of about 3 to 20 μm and a width of about 5 μm is formed. It is preferable that the width of the groove pattern is at least larger than the depth. Both side walls 3 of this groove pattern are sloped surfaces that can receive light perpendicular to the substrate 1. The inclination angle θ of this side wall is in the range of about 45 degrees to 80 degrees, and the larger it is, the more accurate the setting of the irradiation reference point, which will be described later, becomes. If the inclination angle θ is less than 45 degrees, the intensity of secondary electron emission becomes too low, making it impossible to detect the reference point with high precision. In the illustrated embodiment, the shape of the marker is a cross, but it may have any shape as long as both side walls of the groove pattern are sloped surfaces.

As a method for forming such a groove pattern with sidewalls 3 having inclined surfaces, it is possible to form a groove pattern with sidewalls having a predetermined inclination angle with good reproducibility by etching using a wet etching liquid having crystal orientation selectivity. can.

<Operation> As described above, a groove pattern with the side wall 3 as an inclined surface is formed on the substrate/surface as a marker by wet etching or the like, and the surface of the substrate 7 is etched across the groove pattern as shown in FIG. When scanning with a focused ion beam, secondary electrons S are emitted from the substrate. When the width of the groove is larger than the depth of the groove, the intensity of the emitted secondary electrons is almost the same between the substrate surface and the inner bottom surface of the groove pattern.

However, in the sidewall inclined surface 3 of the groove pattern, the ion implantation depth is mainly isometrically smaller than that at the surface, so that the amount of secondary electron emission increases dramatically. When the emitted secondary electrons S are measured by a secondary electron intensity measuring device (not shown) such as an electron multiplier tube, an output signal as shown in the graph of FIG. 5 is often obtained. That is,
When the ion beam q is scanning the surface of the substrate l, r
The secondary electron intensity signal received by the measuring device is small, but when the ion beam scans the groove pattern - the slope 3, the signal suddenly becomes several times larger than when scanning a flat area, and Since the width is narrow, it is displayed as peak 6α.

While scanning the bottom surface of the groove pattern, the signal becomes small, but when scanning the inclined surface again, the secondary electron intensity signal suddenly rises to form a peak 6b.

The center point 7 of the e-pattern is determined from the positions of the two peaks 6α and 46 obtained, and when ion beam irradiation is performed using the center point of this groove pattern as the reference point for ion beam irradiation, the reference point is always a point. Since it is recognized as 0.5
Ion beam irradiation can be performed with an accuracy of P or less. In this case, as the inclination angle θ of the side wall of the groove pattern increases, the received output signal becomes smaller, but the formed peak becomes steeper, and the detection accuracy of the center point of the groove pattern becomes higher.

<Example> Etching solution (H, So, : 'H
, O, : H, 0=4:1:1), a cross-shaped pattern with a groove width of 2op and a depth of 2μ was formed as a marker. The angle of inclination of both side walls formed was approximately 54 degrees.

The photograph in FIG. 4 is a secondary electron image of this cross-shaped ion beam.

Diameter 0.2μ across the above cross-shaped groove pattern.
As a result of scanning with a focused ion beam of Since all the peaks were steep, the peak positions were determined with an accuracy of about 0.2 μm. Therefore, the marker reference point could also be determined with a high accuracy of 0.2 μm.

Next, a 1 μm thick GaAs layer was grown on the GaA3 substrate on which the cross-shaped pattern was formed by molecular beam crystal growth. The photograph in FIG. 5 is a secondary electron image taken by an ion beam when the GaAs layer was grown on a GaAs substrate.

Next, as in the previous example, a focused ion beam with a diameter of 0.2 μm was used to scan across the cross-shaped groove pattern, and as a result, two secondary electron peaks with the same shape as above were obtained. However, the spacing between the peak positions was always about 1.0 microns larger than the spacing between the peak positions on the substrate. This is because the thickness of the grown film formed on the sloped surface was slightly thinner than that on the flat surface, but the film thickness on the left and right sloped surfaces was different, and the direction of the peak deviation was from the center. Since the directions were away from each other, the center point between the two peak positions on the grown film coincided with the center point that was used as the irradiation reference point of the substrate described above.

<Effects of the Invention> As described above, in this invention, both side walls of the groove pattern of the marker are made into sloped surfaces, and the center point of the groove pattern is determined by the secondary electrons emitted from the slopes, and the center point of the groove pattern is determined as a reference point for ion beam irradiation. Since the ion beam is used, there is no need to deepen the groove pattern of the marker, and even if the width of the groove pattern of the marker is much wider than the ion beam, the reference point is always detected and determined as a point. Therefore, the ion beam will be irradiated to a precise position. Further, when a crystal is grown on a semiconductor substrate, the crystal also grows on the i-force, and the shape of the groove pattern changes slightly, changing the peak position of secondary electrons. but,
Since the left and right inclined surfaces are formed symmetrically, the directions of the two peak positions are opposite to each other, and the amount of deviation is the same, so the ρ center point between the two peak positions is Ic is the center point which is the ion beam irradiation reference point of the groove pattern.

Therefore, according to the present invention, even when impurity ions are implanted into the substrate after crystal growth on the substrate, the ion implantation can always be carried out reliably at the correct position.

[Brief explanation of drawings]

@Figure 1 is an enlarged perspective view of the marker according to the present invention, and Figure 2 is the ion beam 1! ``An explanatory diagram showing the secondary electron emission pattern when scanning. Figure 3 is a graph showing the secondary electron intensity during emission. Figure 4 is the secondary electron emission pattern by the cross-shaped groove pattern ion beam according to the present invention. A photograph showing the image, and FIG. 5 is a photograph showing a secondary electron image by an ion beam after crystal growth on the groove pattern in FIG. 4. l...Semiconductor substrate, C...Groove pattern , 3... inclined side wall, D... ion beam, S... secondary electron, 6
α. 6b...Secondary electron peak, 7...Reference point. Patent Applicant Director of the Agency of Industrial Science and Technology Hirobe Yoda Yoshi 1 Corner Beam L Gonogen 1 Foreign Books of the Besieged (Contents No Changes No. 41 5th Internal Procedure Amendment (Method) 1. Indication of Case Patent Application 161530/1982 % 2. Name of the invention Ion beam irradiation method 3. Relationship with the case of the person making the amendment Patent applicant November 7, 1982 5. Amendment vs. S In this specification, a column for a brief explanation of the drawings; Drawing 3, contents of the amendment as shown in the attached sheet.
``Figure 4 is a photograph of 0011.'' written on the 9th line is changed to ``Figure 4 is a diagram showing a secondary electron image of a cross-shaped groove pattern by an ion beam according to the present invention, and Figure 5 is s1. !This is a diagram showing a secondary electron image by an ion beam after crystal growth on the groove pattern in Figure 4.'' In the attached drawings, Figures 4 and 5 are corrected as shown in the attached sheet. Procedural amendment (voluntary) Date of 1933

Claims (1)

[Claims] A groove pattern with sloped side walls is formed on a semiconductor substrate, and an ion beam is scanned across the groove pattern to measure the emitted secondary electrons. Detecting each peak position generated from the surface, determining the center point between the two peak positions from the above two peak positions, and irradiating the semiconductor substrate with the ion beam using the obtained center point as a reference point for ion beam irradiation. An ion beam irradiation method characterized by: