JPH04157719A - Formation method of non-alloy type contact layer - Google Patents

Abstract

PURPOSE:To obtain a method which can form a non-alloy type contact layer in a desired pattern without executing a plurality of treatment processes by a method wherein the blank for the non-alloy type contact layer is vapor-deposited in the desired pattern on a semiconductor substrate by utilizing a focused ion beam from a focused ion beam device provided with an ion-beam deflecting function. CONSTITUTION:Fine particles extracted from an ion source 11 are accelerated toward the surface of a substrate (m) by means of a potential difference of 30 to 50[kV] given by an accelerating power supply; they are focused by a first electron lens 13a and are changed to a focused ion beam F3. At this stage, ions are selected by using a mass filter 14. The focused ion beam B which has been passed through the mass filter 14 is focused again by using a second electron lens 13b; its direction is adjusted by using a deflecting electrode 15 controlled by a deflecting-voltage control part 26 so as to obtain a desired contact pattern. When the focused ion beam 13 whose direction has been adjusted is passed through a decelerating electrode 16, it is decelerated down to a prescribed energy and is vapor-deposited on the gallium arsenide substrate (m). Consequently, it is possible to form a non-alloy type contact layer by executing one treatment process.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application This invention forms a contact layer exhibiting ohmic characteristics at the contact area by depositing a metal layer or a different type of semiconductor layer on a semiconductor substrate. Regarding the method.

Note that the present invention is utilized in manufacturing processes of various semiconductor elements using the above-described forming method.

B. Conventional technology Silicon (Si) and gallium arsenide (C; a As
) When a metal layer or a different type of semiconductor layer is formed by vapor deposition on a semiconductor substrate such as a semiconductor substrate, the first current voltage characteristics of the contact portion may exhibit a linear relationship (ohmic characteristics) depending on the combination. Typical examples thereof are the silicon substrate and aluminum layer, and the combination of the gallium arsenide substrate and germanium layer.

Methods for forming contact layers that provide ohmic contact can be roughly divided into the following two methods.

(1) Formation of contact layer by alloying treatment This is a method of alloying the contact surface between the semiconductor substrate and the contact layer to form an ohmink contact layer. First, the third
As shown in Figure (a), a contact layer 1 made of aluminum is deposited on a silicon wafer m. When this is heat-treated at a high temperature, the molten contact layer A diffuses into the silicon wafer m and is bonded to it, and the bonding surface (contact surface) is alloyed as shown by the hatched part G in the same figure.

Next, the process moves to the following steps shown in FIG. 4 to form contacts 11 in a desired pattern.

(2) Resist Coating and Exposure Process The entire surface of the contact layer 1 is coated with an anti-glare resin 2 (photoresist wA2). Next, the pattern portion to be formed is irradiated with light 3 (for example, ultraviolet rays or electron beams), and the photoresist film 2 in that portion is exposed to intense light to form a mask against etching.

(2) Etching treatment process There are various treatment methods for etching treatment, and here, plasma etching treatment will be taken as an example. This involves placing a low-pressure gas in a high-frequency electric field to turn it into plasma, and using the chemical reaction caused by the plasma to etch the contact layer 1 using the photoresist film 2 as a mask.

■Resist removal This is the process of removing the resist film 2 left on the desired pattern.This process involves removing the resist film 2 with chemicals,
Alternatively, the surface of the substrate m is exposed to 02 plasma, and unnecessary Renost film 2 is scraped off by the reaction.

(2) Formation of a non-alloy type contact layer A non-alloy type, in other words, forms an ohmink contact layer without alloying the contact area between the contact layer and the semiconductor substrate as described above. This is realized by a combination of materials for the semiconductor substrate and the contact layer (for example, a gallium arsenide substrate and germanium). The formation method includes -IC CVD method (c-h
elIical vapor deposition)
is used.

Further, after forming the contact layer, a desired pattern is formed in the same manner as in (1) above.

C1 Problems to be Solved by the Invention However, the above-mentioned conventional method has the following problems.

The method for forming a contact layer using the "alloying treatment" described in (1) has a problem in that a high temperature heat treatment step cannot be performed on the semiconductor substrate after the contact layer is formed.

In other words, although the contact area between the semiconductor substrate and the contact layer is alloyed by heat treatment, if this is further heat treated at high temperature, the alloyed part will melt due to the heat treatment, and the alloy bond will collapse. There is a risk that the ohmic characteristics will deteriorate. Therefore, it is not possible to provide a high-temperature heat treatment process in various subsequent processing steps, and the degree of freedom in processing related to the manufacture of semiconductor elements is reduced.

On the other hand, in the case of forming a non-alloy type contact layer as described in (2), the contact area between the semiconductor substrate and the contact layer is not alloyed by heat treatment, but the ohmink contact is created by a combination of mutual materials. Therefore, even if high-temperature heat treatment is performed in various later processing steps, the ohmic characteristics will not deteriorate. The present invention also relates to a method of forming this lump 0-type contact layer.

However, in the conventional method of forming a non-alloy contact layer, after forming a contact layer on the entire surface of the substrate by CVD, multiple processing steps such as resist coating, etching treatment 1, and resist supply removal treatment are performed to form a desired pattern. Since I have gone through this process, I have the following problems.

That is, in resist processing, which is an essential process, problems occur such that resist residue (dust) exists on the contact layer or the surface of the semiconductor substrate is damaged due to the asonon method using plasma.

Further, when going through the above-mentioned processing steps, various apparatuses are required to carry out the respective processes, so the semiconductor substrate must be transported between the various apparatuses. During this transportation process,
Since the semiconductor substrate is transferred from a vacuum to the atmosphere, there is a possibility that the semiconductor substrate will be contaminated by the atmosphere, leading to a decrease in quality.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method that can form a non-alloy contact layer in a desired pattern without going through a plurality of processing steps as described above. The purpose is

91 Means for Solving the Problems The present invention takes the following method to achieve the above object.

That is, the present invention provides a method for forming a non-alloy contact layer whose contact surface exhibits ohmic characteristics when bonded to a specific semiconductor substrate material. A non-alloy contact layer is formed by depositing seven materials for the non-alloy contact layer on the semiconductor substrate in an arbitrary pattern using a focused ion beam.

80 Effect When forming a non-alloy contact layer using the method of the present invention, for example, the material of the non-alloy contact layer itself is ionized, a focused ion beam is created, and a desired pattern is formed using this! / - If the beam is deflected to a certain degree and decelerated below a certain level of energy and irradiated onto the semiconductor substrate,
A non-alloy contact layer is formed at the irradiated position.

Alternatively, a semiconductor substrate is placed in a gas atmosphere containing gas molecules of a non-alloy contact material, and a focused ion beam made of arbitrary ions is deflected to trace a desired pattern and irradiated into the gas atmosphere. When gas molecules are forced onto a semiconductor substrate with the ion beam, a non-alloy contact layer is formed at the irradiated location.

In either case, the formation of the non-alloyed contact layer is achieved within one processing step, thereby eliminating the inconveniences associated with multiple processing steps.

F. Example Embodiments of the present invention will be described below based on the drawings.

Blu! iJL Doctor In this first embodiment, a method for forming a non-alloy contact layer using a focused ion beam that ionizes the material of the non-alloy contact layer itself will be described.

FIG. 1 is a cross-sectional view showing a schematic configuration of a focused ion beam device used to carry out the formation method of this example.

In the figure, reference numeral 10 is a vacuum chamber, which is the main casing of this device. The following components are housed inside this true chamber 10.

11 is a liquid metal ion source that generates ions, and is a non-alloy contact material (
This is a melting furnace that melts and liquefies, for example, germanium as a contact material (hereinafter abbreviated as contact material). A needle 25 is provided at the sharp tip of the ion source 11 (the tip at the bottom in the drawing), and the molten contact material is configured to be supplied to the tip of the needle 25. .

An acceleration Hs23 is connected to the ion source 11, which applies acceleration energy to the ions through the potential difference. Note that a heater for heating the ion source 11 is not shown.

Reference numeral 12 denotes an extraction electrode for extracting ionized fine particles from ion sin, and an extraction power source 22 is connected between this extraction electrode 12 and the ion source 11. 13a is a first electron lens that focuses the ion beam B, 14 is a mass filter for selecting only desired ions, and 13b is a second electron lens.

Reference numeral 15 denotes a deflection electrode for deflecting the focused ion beam B, and the deflection of the focused ion beam B is adjusted by a deflection voltage control unit 26 connected thereto. A deceleration electrode 16 decelerates the acceleration energy of the ion beam B to weaken its speed, and a deceleration power source 24 is connected between the deceleration electrode 16 and the stage 17 on which the gallium arsenide substrate m is placed.

The stage 17 is an X-Y stage 2 that is movable in the X and Y directions (the left-right direction of the drawing and the horizontal direction orthogonal thereto).
0, and a drive motor 21 for driving the XY stage 20 is provided outside the vacuum chamber 10. The stage movement control section 27 controls the driving force of the drive motor 21 to move the stage 17.

At the bottom of the vacuum chamber 10 (lower part in the drawing), there is a communication pipe 1
A vacuum pump 19 is connected to the end of the communication pipe 18. Note that when moving the stage 17, a length measuring needle such as a laser length measuring needle (not shown) using laser interferometry is used to detect the moving distance, and a detection signal of this length measuring needle is used. The structure is such that movement control is performed by feedbanking.

Next, a method of forming a non-alloy contact layer using the above-described apparatus will be described.

First, a contact material (germanium) is placed in ions 'a11 and heated. The contact material is melted and liquefied and supplied to the tip of the needle 25. While keeping the temperature of ion a11 at the melting point, the extraction power supply 2 is turned on.
2 between the ion source 11 and the extraction electrode 12,
In other words, about 7 mL of water is applied to the tip of the needle 25 covered with the liquid material.
Give a potential difference of ~8 [kV]. When the electric field applied to the surface of the liquid material reaches the intensity of the trace electric field of the liquid material, the release of ionized particles begins. The fine particles extracted from the ion in are supplied with 30
Due to the potential difference of ~50 kV, the ions are accelerated onto the surface of the substrate m, focused by the first electron lens 13a, and become a focused ion beam B. At this stage, the ions are selected by the mass filter 14.

In general, it may be possible to lower the melting point by melting a compound material than by melting a single material, and in this case, only the desired particles are passed through the regular beam path, and the other particles are passed through the beam path. The mass filter 14 deflects the light to the outside and sorts it out.

Mass filter 14 i! The focused ion beam B that has been used for i weeks is focused again by the second electron lens 13b, and is then focused by the deflection electrode 15 controlled by the polarization voltage control unit 26.
The orientation is adjusted to obtain a desired contact pattern.

The focused ion beam B whose direction has been adjusted is transferred to the deceleration electrode 16.
When passing through, it is decelerated to a predetermined energy,
The 1,1 um arsenide reaches the surface of the arsenic substrate m. The energy of the focused ion beam B at this time is equal to the output voltage difference between the acceleration source 23 and the deceleration power source 24. That is, the focused ion beam B has acceleration energy given by the acceleration power source 23 until it approaches the deceleration electrode 24, but the potential of the deceleration electrode 24 and the stage 17 is reduced by the deceleration electrode 24.
, the focused ion beam B incident on the substrate m is decelerated by that amount. Therefore, by adjusting the output of the deceleration electrode 24, it is possible in principle to change the power of the focused ion beam B continuously between 0 and the output voltage value of the accelerating electrode 1ff123. Therefore, by adjusting the output value of the deceleration source 24 so that the focused ion beam B is not implanted into the gallium arsenide substrate m, the focused ion beam B is imprinted on the gallium arsenide substrate m, and non-alloyed with germanium. A shaped contact layer is formed.

Specifically, the mechanical strength of the focused ion beam B is 0 to 20.
This is possible by adjusting the potential difference between the deceleration electrode 16 and the stage 17 so that 01 eV].

In the previous explanation, when drawing a desired contact pattern with the focused ion beam B, the irradiation light is adjusted by the deflection electrode 15. However, if the drawing range of the contact pattern extends over a wide range, the deflection electrode 15 Due to the deflection limit (when the degree of deflection is increased, the beam width of the focused ion beam B becomes thicker, making it impossible to form fine contact patterns, so there is a limit to the deflection range), making it possible to draw all circuit patterns. In such a case, by giving a control signal from the stage movement control unit 27 to the drive motor 2I and moving the X-Y stage 20, the gallium arsenide substrate m can be moved together with the stage [7]. , the gallium arsenide substrate m is positioned within the deflection range of the deflection electrode 15.

11th Example In this second example, a method for forming a non-alloy contact layer using a focused ion beam made of appropriate ions will be described.

FIG. 2 is a cross-sectional view showing a schematic configuration of a focused ion beam device used to carry out this method.

Note that in FIG. 2, the same components as those in FIG.

There are two differences from the focused ion beam device used in the first embodiment.

One is that the deceleration electrode 16 and the deceleration power source 24 are eliminated, and the other is that a gas containing a contact material (for example, a gas containing germanium gas molecules) is supplied to the chamber chamber 10.
The point is that a new gas injection nozzle 30 has been installed to feed the gas into the interior.

In this example, ionized gallium is used as the ion to be irradiated, but it may also be, for example, the germanium ion described in the previous example.

To form a non-alloy contact layer using such an apparatus, first, a gas of a compound containing germanium gas molecules, such as G, H,
Gas is injected to change the upper atmosphere of the gallium arsenide substrate m to G,
H, gas atmosphere.

In this atmosphere, a focused ion beam consisting of gallium ions formed in the same manner as above is irradiated, and germanium molecules in the atmospheric gas are energized onto the gallium arsenide substrate m by the ion beam, thereby forming a germanium film. is deposited to form a non-alloy contact layer in a desired pattern.

In this method, a non-alloy type contact layer is not formed by irradiating a focused ion beam consisting of ions of the contact material onto the gallium arsenide substrate m, so as described above, the deceleration electrode 16 and the deceleration 'til! Although 24 is excluded, considering the damage caused to the gallium arsenide substrate m, it can be said that the forming method described in the "first embodiment" including these components is a more preferable example.

In each of the above embodiments, the combination of a gallium arsenide substrate and a germanium layer is taken as an example, but any other combination of bonding that exhibits ohmink characteristics in the contact area can be applied in the same manner as above. Thus, a non-alloyed contact layer can be formed in one processing step.

Effects of the G0 Invention As is clear from the above explanation, the method for forming a non-alloy contact layer according to the present invention uses a focused ion beam irradiated from a focused ion beam device to form the material of the non-alloy contact layer. Since the non-alloy contact layer is formed by vapor deposition in an arbitrary pattern on the semiconductor substrate, the non-alloy contact layer can be formed within one processing step.

Therefore, compared to the conventional method of achieving this through multiple processing steps, damage and contamination caused to the semiconductor substrate can be reduced, contributing to the production of high-multiplying, high-quality semiconductor devices. can.

[Brief explanation of drawings]

1 and 2 relate to one embodiment of the present invention, and FIG. 1 is a cross-sectional view showing a schematic configuration of a focused ion beam apparatus for realizing the method of forming a non-alloy contact layer of the first embodiment. 2 are cross-sectional views showing a schematic configuration of a focused ion beam apparatus for realizing the method of forming a non-alloy contact layer according to the second embodiment. Further, FIGS. 3 and 4 relate to conventional examples, FIG. 3 is a diagram explaining the formation of a non-alloy type contact layer by an alloying treatment method, and FIG. 4 is a diagram explaining the formation of a desired pattern of the non-alloy type contact layer. It is a diagram. 11... Ion source 15... Deflection electrode B.
...Focused ion beam m...Gallium arsenide substrate patent applicant Shimadzu Corporation

Claims (1)

[Claims] (1) In a method for forming a non-alloy contact layer whose contact surface has ohmic characteristics when bonded to a specific semiconductor substrate material, a focused ion beam from a focused ion beam device having at least an ion beam deflection function is used. A method for forming a non-alloy contact layer, characterized in that the non-alloy contact layer is formed by depositing a material for the non-alloy contact layer on the semiconductor substrate in an arbitrary pattern.