A method of manufacturing semiconductor devices

 

(57) Abstract:

Usage: in microelectronics for the production of Schottky transistors on the Mesa-structures. The inventive method includes the manufacture of semiconductor devices on politology plusline of gallium arsenide with an active structure by forming a Mesa structure, forming a mask of silicon dioxide with a window above the active region of the device, forming a protective mask anodic oxidation, removing the mask of silicon dioxide by plasma-chemical etching, annealing protective mask anodic oxide, the formation of the contact to the reverse side of the wafer and the deposition of the ohmic contact of the electrolyte with an additional plate lighting. This is achieved by improving the quality of ohmic contacts. 5 Il.

The invention relates to semiconductor technology and can be used in the manufacture of Schottky field-effect transistors.

A known method of manufacturing field-effect transistors on the Mesa-structures [1] . Mesa structure is formed by chemical etching in a solution of NH4OH:H2O: H2O. Ohmic contacts create thermal spraying of a layer of Au-Ge-Ni with a thickness of 0.15 μm, followed by "Bang" photoresistive swity relief, numerous pores. The result is increased ohmic resistance. In addition, most of the deposited layer is removed along with photoresistive mask, which is uneconomical.

The closest technical solution of the invention is a method of manufacturing semiconductor devices, comprising the oxidation of meso-structures and electrochemical deposition of the contact mask anodic oxide [2]. Use patterns GaAlAs. For local oxidation Mesa and deposition of contacts using conductive layer GaAs n-type.

The disadvantage of this method is that when the deposition from the electrolyte Au-Ge contacts the dissolution occurs mask anodic oxide. In the contaminated electrolyte, shortens its life. In addition, this method does not allow to use politology substrate.

Technical result achieved during implementation of the method is to improve the quality of ohmic contacts by reducing contamination of the electrolyte in the process of their deposition, by increasing the chemical resistance of the mask anodic oxide and reducing its area.

The result is achieved by conducting anodic oxidation only areas of the channel, after-the La in the channel and as the plate material used politology gallium arsenide.

In the proposed method, the annealing is carried out in the temperature range 300-500aboutWith to improve chemical resistance of oxide. At lower temperatures, the anodic oxide thickness of 0.1 μm almost completely dissolved in the electrolyte during the deposition of the metal. At temperatures above 500aboutWith the surface of the semiconductor in the channel is enriched with arsenic, increase the point of leakage of the transistor.

According to the proposed method of anodic oxidation of the plates is carried out only in the channel region of a transistor, which reduces the amount of anodic oxide, dissolving in the deposition of contacts. The deposition is carried out at intensive plate lighting. As a result, the contacts are formed only on the n+-the surface of the active regions. On the surface of the Mesa deposition of metal does not occur in the absence of additional photoresistive mask.

In Fig. 1 shows a plate with a Mesa structure of Fig. 2 - plate with a photoresistive mask for forming the channel of Fig. 3 - plate with anode oxide in the channel of Fig. 4 - plate with deposited from the electrolyte contacts; Fig. 5 - shows a General view of the manufactured device.

For a specific example of the use of UP>3< / BR>
thickness of dn+=0.2 μm

n=1.5 1017at/cm3dn=0,35 µm

dn 0.5 micron.

On the surface of the plate create a photoresistive mask that protects the active area of semiconductor devices. Form a Mesa structure by etching in a solution of H3PO4:H2O2:H2O the depth of the Mesa 0.8 μm, the angle of the Mesa-faces 10about. The photoresist is removed in dimethylformamide (Fig. 1). Put a layer of SiO2the thickness of 0.3 μm. Create a photoresistive mask with Windows over the channel regions of the transistors (Fig. 2). Remove SiO2in the Windows in the buffer provide the Etchant NH4F:HF:H2O. the Photoresist is removed. Carry out anodic oxidation of the plate mask SiO2forming the channel of the transistor. The thickness of the oxide layer of 0.2 μm, the depth of etching of 0.14 μm. The cell voltage 130 Century.

Remove SiO2plasmochemical selectively to the gallium arsenide and the anodic oxide (Fig. 3). Hold the lamp annealing plates with anodic oxide at a temperature of 400aboutC for 40 s using the "Impulse 5". Annealing is required to improve chemical resistance of anodic oxide. Thus the rate of dissolution of oxide in the deposition of ohmic contacts is reduced from 600 rpm (for geotagging), 400 /) 300aboutWith chemical resistance oxide almost does not increase. The layer of anodic oxide thickness of 0.15 μm in the deposition of contacts is completely dissolved. At annealing temperatures above 500aboutTo change the stoichiometric composition of the surface of a semiconductor. The surface is enriched with arsenic.

The plate is treated in a solution of NH4OH:H2O2:H2O=1:0,5:40 for 5 s to remove the natural oxide on exposed regions of n+-layer. Then install the plate in the cassette horizontally. Create electrical contact to the bottom politology side of the wafer in a solution of KOH:NH4H2PO4:H2O=3y: 0.3 g: 100 ml for lighting. The amount of light of 100,000 Lux. In the absence of light through the current through the plate does not leak. The electrolyte for the deposition of Au-Ge fill the upper part of the cassette plate. Precipitated Au-Ge ohmic contacts by the intense light of 100,000 Lux. Duration of 3 min cell Voltage of 2 V, the total current through the plate of 0.7 mA. The thickness of the formed contacts 800 . The deposition of metal occurs only on the surface of the n+-layer active regions on the mask anodic oxide in the channel. On the surface of the etched Mesa metal not academese-face the corresponding n-layer. When the amount of light more than 70,000 Lux metal on meze not find.

In the process of deposition of a metal anodic oxide is dissolved, contaminating the electrolyte. According to the proposed method the surface area of the anodic film is minimal, as they form only in the channel of the transistor. The dissolution rate of oxide reduce heat treated.

Fuse ohmic contacts on the installation of the lamp annealing "Impulse 5" at a temperature of 450aboutWith 3 pulse duration of 4 C. After the mould surface contacts preserves the original morphology. When the thickness of the contacts larger than 0.1 μm develops relief, at thicknesses of less than 400 increases the ohmic resistance. The ohmic resistance of the formed contacts 0.1 Ohm mm

Create a photoresistive mask with a pattern of the gate. Remove the anodic oxide remaining after the manifestation of the mask, in a solution of NH4OH:H2O=1:20 for 20 sec. Hold chemical etching of gate regions to provide a specified current saturation in a solution of NH4OH:H2O2:H2O=1:0,5:40. Sprayed layer of gate metallization V-Au-V with a thickness of 0.7 μm. "Explosion" photoresistive mask to form the gate. In areas kanaal the surface of a semiconductor. This increases the breakdown voltage of the transistor.

According to the proposed method, the deposition of ohmic contacts on the n+-the surface of the active regions is carried out only on the mask anodic oxide in the channel. This allows to decrease in the deposition of metal, the amount of soluble anodic oxide, to reduce contamination of the electrolyte to increase its service life. Carrying out heat treatment increases the chemical resistance of the anodic film. Anodic oxide in the channel increases the breakdown voltage of the transistor.

Samozavestna area of channel deposition of ohmic contacts eliminates the need for the formation of the photoresist mask, allows to minimize the distance of the source - drain.

Formed by deposition from the electrolyte thin (400-1000 ) Au-Ge contacts remain after the mould of the original morphology of the surface are low, 0.1 Ohm mm, ohmic resistance.

A method of MANUFACTURING a SEMICONDUCTOR device, comprising forming on the surface of the wafer of gallium arsenide with an active structure of the mask of silicon dioxide, the formation of the Mesa structure, the formation of a protective mask anodic oxidation, removing the mask of silicon dioxide n the side plates, characterized in that as the plate material used politology gallium arsenide, mesostructure formed before formation of the mask of silicon dioxide, a mask of silicon dioxide is formed with a window above the active region of the device, after removing the mask of silicon dioxide spend annealing protective mask anodic oxide, the contact to the back side of the plate is formed before the deposition of ohmic contacts, and in the deposition of ohmic contacts plate additionally light.

 

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