CS200062B1 - Heating-up packing piece of semiconductor substrates for chemical deposition of oxide layers from the gaseous phase - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to the heating of a substrate for the conductor substrates for the chemical deposition of oxide layers from the gas phase in the temperature range of 20 to 500 ° C.

In the preparation of oxide films by chemical vapor deposition., E.g. layers of silicon oxide Si0 ₂ or aluminum oxide A1 ₂ O-oxidation of silane with oxygen or oxidabí triisopropylolkoholátu aluminum with oxygen on the surfaces of semiconductor substrates, e.g. on Si or fosfiů gallium GAP semiconductor the substrates are deposited on a heating pad in a deposition space, eg a tube or a bell in which the gaseous reaction mixture flows. Oxygen layers grow on and around heated semiconductor substrates by appropriate chemical reactions between the gaseous reactants.

The heating mat is at rest or sepohy depending on the design of the apparatus so that the gaseous reactants wash all semiconductor substrates deposited thereon.

Because of the further processing of the oxide layers on the semiconductor substrates, for example by photolithography, it is desirable that the thickness of the layers of not all semiconductor substrates in the batch be as uniform as possible; the temperature dissipation of the semiconductor substrates during deposition should be as low as the deposition rate of the oxide layers depends on temperature. This can only be achieved by using a heating pad made of a material with high thermal conductivity. E.g. in the preparation of SiO ₂ layers by oxidation of silane with oxygen, deposition rates in the range of 300 to 400 ° C are mentioned

200 062

0.5 to 0.6%.

In order to achieve the same temperature of the entire surface of the heating pad and hence the semiconductor bubbles, the heating pads are made of materials of high thermal conductivity. Aluminum and its alloys, graphite and stainless steel are used. However, these materials have a number of disadvantages.

In order to avoid direct contact of the heater mat material with the semiconductor substrates, the heater mats are coated with a SiO2 or Al2O4 layer of typical thickness of 0.5 to 1 µm prior to the first deposition on the semiconductor substrates. Semiconductor substrates are each on ^one silicon oxide layer of SiOx or aluminum oxide algo-j. This protective layer, along with the silicon dioxide layers deposited spontaneously in the vicinity of the semiconductor substrates, is periodically, usually once a week, scattered in hydrofluoric acid solutions and applied again. This regeneration of the heating pad is necessary because the oxide layers eventually peel off from the heating pad and contaminate the surface of the semiconductor substrates and further, due to the unequal size of the semiconductor substrates and the impossibility to store them at exactly the same location. At the same time, periodic regeneration of the heating pad prevents contamination of the contact surface of the heating pad semiconductor substrates by abrasion or diffusion.

Heating pads made of aluminum and its alloys deform during operation at temperatures up to 500 ° C and are corroded in etchers into which a layer of deposited oxides is removed from the heating pad, eg in hydrofluoric acid solutions. The graphite heating pads are porous and brittle with a relatively low thermal conductivity, about

2x lower aluminum. Stainless steel heating pads have 15 times lower thermal conductivity than aluminum.

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SUMMARY OF THE INVENTION The present invention provides a heating pad of semiconductor substrates for the chemical deposition of oxide layers from the gas phase to a temperature of 500 ° C, which is made of copper coated with a 10-20 µm nickel layer and 1 to 5 µm platinum or rhodium.

From the typical chemical deposition temperatures of the silica or alumina layers of 300-500 ° C, copper has a thermal conductivity close to that of silver, i.e. the highest of all existing technical materials. The thermal conductivity of copper at 300-500 ° C is 2 times higher aluminum, about 4 times higher graphite and about 30 times higher stainless steel. However, the copper itself is very easily oxidized by oxygen or water vapor, especially at higher temperatures to form copper oxides which peel off from the heating pad at room temperature. This problem is solved by the present protective layers. These protective layers can be deposited, for example, by electroplating. Of these protective coatings, rhodium is particularly preferred as one of the most resistant metals ever. Protective coatings of rhodium are very hard, excellent resistance to oxidation by oxygen or water vapor and hydrofluoric acid. Since the mean coefficient of linear thermal expansion of copper in the temperature range of 0 to 500 ° C is 1.9x higher platinum and 2.25x higher rhodium, it is desirable, in terms of expansion adjustment, to cover the copper heating pad prior to platinum or rhodium deposition with nickel, e.g.

The mean coefficient of linear thermal expansion of nickel in the temperature range of 0 to 500 ° C is only 1.5 times lower. In this way, even thicker platinum or rhodium protective layers can be deposited without breaking.

As an example, the support layer of pMe2 substrate materials for the chemical deposition of oxide layers from the gas phase is a heating pad for deposition of layers of silica on silicon substrates at temperatures up to 500 ° C. On a copper circular plate having a thickness of 5 to 10 mm, a nickel layer of 10 to 30 µm thickness is electroplated and a rhodium layer of 1 to 5 µm thickness is again electroplated.

Another example is a similar heating pad coated with nickel thicknesses of 10 to 30 µm and platinum thicknesses of 1 to 5 µm. ,

Claims (1)

SUBJECT OF THE INVENTION Heating pad of semiconductor substrates for chemical deposition of oxide In the gas phase layers, characterized in that it is made of electrolytically pure copper coated with a layer of 10 to 30 µm nickel, to which the layer is 1 to 5 µm rhodium or 1 to 5 yum platinum.