JP2690574B2 - Device making method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an element, and more particularly to a method for manufacturing an element such as an electronic device or an optical device using a focused ion beam (FIB: Focused Ion Beam). .

[Prior Art] Taking a MESFET as an example of an element, a conventional art will be described with reference to FIG.

An alignment mark (hereinafter referred to as a mark) 2a is formed on the GaAs substrate 1 by using a plasma etching apparatus or a sputter etching apparatus. At that time, the conventional ion implantation apparatus uses an unfocused ion beam that irradiates the entire surface of the wafer with ions, and it is not possible to selectively etch only the portion that should be the mark 2a. Etching is performed using a mask made of resist, SiO ₂ , Si ₃ N ₄ , metal or the like. After forming the mark 2a, the Si ₃ N ₄ film 5 and the resist 8a are deposited on the substrate 1. An opening 9 for ion implantation is patterned by lithography in the resist 8a using 2b or 2a as a mark and a mask or the like, and Si ions are implanted through the opening 9 to form an n region 10 (see FIG. a)). Ions are implanted at an acceleration voltage of 100 KeV and a dose amount of 2.5 × 10 ¹² / cm ² .

Further, as shown in FIG. 4 (b), the source and drain portions 11 and 12 are masked with a resist 8b except the source and drain portions 11 and 12.
Deep ion implantation with an acceleration voltage of 300 keV is performed on the drain parts 11 and 12 to form an n ⁺ layer having an impurity concentration of 9 × 10 ¹⁶ / cm ² . This layer becomes an ohmic contact layer for electrode formation.

After that, an element is processed through an activation heat treatment step at 850 ° C. (FIG. 4C), a step of forming an ohmic electrode 13 (FIG. 4D), and a step of forming a Schottky electrode 14 (FIG. 4E). I was working on it.

[Problems to be Solved by the Invention] However, in the above conventional example, as shown in FIGS. 4 (a) and 4 (b), two resist steps are performed for etching (mark formation) and ion implantation. Inevitably, the etching process and the ion implantation process are independent processes. Therefore, the number of steps is complicated, and there is not much freedom in the conditions for manufacturing the device.

[Means for Solving the Problems] According to the element manufacturing method of the present invention, in the element manufacturing method having at least an etching step and an ion implantation step, the etching step and the ion implantation step are the same without using a focused ion beam. It is characterized in that it is performed in the process.

[Operation] According to the present invention, by using FIB, ion implantation and etching can be selectively performed without using a resist and a mask, and the ion species and the acceleration voltage of implantation can be changed. It is possible to carry out etching and ion implantation in the inside, and it is possible to form the device extremely easily.

FIG. 3 shows an example of the FIB device used in the present invention.
The ion beam field-emitted from the i-Be liquid metal ion source 301 is focused by the condenser lens 302, and the E × B mass separator 3
In 03, only the necessary ions are separated. Then the objective lens
The beam is focused again at 304, and the ion beam is deflected by computer control to irradiate the substrate 307. The substrate 307 is set at a desired position by freely moving the stage 306 of the movable stage device 305 in the XY plane by moving means attached to the stage device 305. Reference numeral 308 is a detector for obtaining beam position information, and 309 is a Faraday cup for detecting ion beam current.

The element manufacturing method shown in the present invention is realized by using such device means.

[Embodiment] FIG. 1 is an example of making a MESFET, and an example of making the mark and the element part in the same step by controlling the depth direction by the change of the acceleration voltage and selectively changing the dose using the same FIB. It is shown.

In FIG. 1 (a), 1 is a semi-insulating GaAs substrate, the FIB device was set to a 40 keV Au ion beam, and the mark 2 was created by sputter etching without a mask (first
Figure (b).

Next, the ion species were switched to a 40 keV Si ion beam by E × B mass separation, and Si was used for the gate 3 and the source / drain section 4.
Ions were implanted. The peak impurity concentration was 2 × 10 ¹⁷ / cm ³ . At this time, ions were implanted after aligning with the mark 2 formed by the Au ion beam as a reference.

Next, a Si ion beam with an accelerating voltage of 200 keV was used, and after adjusting the position of the Si beam with the mark 2, deep ion implantation was performed on the source and drain portions 4 to obtain a peak impurity concentration of 9 × 10 ¹⁶ / c.
got m ³ . By this ion implantation, good ohmic contact characteristics could be obtained.

Next, after depositing an insulating film (Si ₃ N ₄ film) 5 and activating it by heat treatment at 850 ° C., a source is formed by reactive ion etching,
The drain portion was opened, the ohmic electrode 6 was formed of AuGe (FIG. 1 (c)), and then the Schottky electrode 7 was formed (FIG. 1 (d)).

Here, in the steps of FIGS. 1C and 1D, the mark 2 formed by the Au ion beam could be used, and the position of maskless ion implantation could be controlled with high precision.

[Other Embodiments] FIG. 2 shows a method for producing an electron-emitting device with element isolation using a Schottky electrode.

Here, a p ⁺ layer 202 having an impurity concentration of 5 × 10 ¹⁸ / cm ⁻³ with a thickness of 400 nm and an impurity concentration of 8 × 10 ¹⁶ / cm ⁻³ with a thickness of 300 nm is formed on the semi-insulating substrate 201 by MBE. A substrate made of the grown p-layer 203 was used.

In the step shown in FIG. 2B, an etching groove 204 which also serves as a mark and an element isolation was formed by an ion beam of 40 keV Au. Subsequently, after forming an insulating film (Si ₃ N ₄ ) 208, in order to form a guard ring 206 of a Schottky electrode, after aligning with a mark 204, a Si ion beam of 160 keV was injected to obtain an impurity concentration of 8 × 10 ¹⁷ / cm 2. Formed ³ . Here, after activation treatment by annealing at 850 ° C., a Be ion beam of 40 keV was aligned with the switching mark 204, and then a peak impurity concentration of 8 × 10 ¹⁷ / cm ³ was implanted into the central electron emitting portion 205.

In addition, to make contact between the p ⁺ layer 202 and the substrate 1
A 60 keV Be ion beam was aligned with the mark 204, then injected into 207 parts and annealed again at 650 ° C.

In the step of FIG. 2C, the electron emission surface is formed after the electrode formation with the p ⁺ layer 202 and the wiring electrode 211 of the electron emission surface electrode. Schottky electrode 20 with low work function material LaB ₆
9 was formed to complete the device fabrication (FIG. 2 (d)).

In the present invention, the etching is not limited to sputter etching and may be performed while introducing a reactive gas.

Further, the element that can be produced by the present invention is not limited to the above-mentioned element, but can be applied to optical devices and a wide variety of electronic devices.

[Advantages of the Invention] By using the FIB as described above, not only the ion implantation process is simplified without a mask, but also the implantation conditions are three-dimensionally expanded, and the etching process can be performed at the same time, which makes it possible to achieve the conventional structure. A simpler process has been realized.

A device such as a MESFET or a Schottky diode type electron-emitting device that forms a Schottky electrode having good characteristics on the surface can be formed by simplifying the process steps as described in the present invention. Damage and defects can be prevented, and improvement of device characteristics can be expected.

In addition, by using the formed mark, the accuracy of manufacturing the device is improved, and by performing the isolation between the devices by etching, the two functions of the mark and the isolation gap can be satisfied, and the function is further improved. did.

[Brief description of the drawings]

FIG. 1 is a process drawing of MESFET manufacturing of the present invention. FIG. 2 is a process drawing of the electron-emitting device. FIG. 3 is an explanatory view of a focused ion beam device. Figure 4 is a conventional MESFET fabrication process diagram. 1 ... Substrate, 2 ... Mark, 3 ... Gate, 4 ... Source, drain, 5 ... Insulating film (Si ₃ N ₄ film), 6 ... Ohmic electrode, 7 ... Schottky electrode, 201 ... Semi-insulating substrate, 202 …… p ⁺ layer, 203 …… p layer, 204 …… mark, 205…
… P ⁺ injection layer, 206 …… Guard ring, 208 …… Insulating layer, 20
9 …… Surface electrode, 210 …… p ⁺ substrate electrode, 211 …… Surface wiring electrode.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication H01L 29/812

Claims (6)

(57) [Claims] 1. A device manufacturing method having at least an etching process and an ion implantation process, wherein the etching process and the ion implantation process are performed in the same process without a mask by using a focused ion beam. Law. 2. The etching step is a step of forming a positioning mark in a subsequent step.
Described device manufacturing method. 3. The device manufacturing method according to claim 1, wherein the etching process is a process for manufacturing isolation between devices. 4. The method for producing an element according to claim 1, wherein the element is an electronic device. 5. The device manufacturing method according to claim 4, wherein the electronic device is a MESFET. 6. The device manufacturing method according to claim 4, wherein the electronic device is an electron-emitting device.