Method and apparatus for non-aggressive plasma-enhanced vapor deposition of dielectric films

Abstract

While performing plasma-enhanced chemical vapor deposition on a substrate by exposing the substrate in a vacuum to a flow of particles generated by a plasma, which particles react to form a passivation layer on the substrate, a grid is interposed between the plasma and the substrate, thereby reducing the flow of charged particles towards the substrate while conserving a flow of neutral particles. The grid is formed of metal wires that are crossed at a pitch that is less than two or three times the Debye length (λD) of the plasma used, at least at the beginning of deposition. The aging properties of semiconductor components made by such a method is thereby improved.

Description

[0001] This is a divisional application of U.S. application Ser. No. 10 / 902,582, filed Jul. 30, 2004, the disclosure of which is incorporated herein.BACKGROUND OF THE INVENTION [0002] The present invention relates to methods of fabricating semiconductor components in which at least one step of plasma-enhanced chemical vapor deposition is performed consisting in exposing a semiconductor substrate in a vacuum to a flow of particles generated by a plasma, the particles reacting to form a passivation layer on the substrate of a material that has dielectric properties. [0003] Traditional chemical vapor deposition methods, which are in widespread use for depositing films on substrates, lead to the substrates becoming heated to high temperatures. Such methods can therefore be used only for substrates that withstand high temperatures without significant degradation. [0004] To make deposits on substrates that are relatively fragile, it is common practice to use plasma-enhanced chemical vapor...

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Benefits of technology

[0017] In order to achieve these objects, and others, a first aspect of the invention provides a particular method of depositing dielectric films by plasma-enhanced chemical vapor deposition, in which a substrate is exposed in a vacuum to a flow of particles generated by a plasma, which particles react to form a passivation layer on the substrate. A selective trap is interposed between the plasma and the substrate, thereby reducing the flow of charged particles towards the substrate while conserving the flow of neutral particles.

[0020] a) an initial step of non-aggressive deposition, during which the selective trap effectively reduces the flow of charges particles; and

[0022] It is found that degradation of the surface layer of the substrate takes place essentially at the beginning of deposition, a period during which the substrate is not protected by the deposited layer against aggression by particles of the plasma. Thus, during the initial deposition step, deposition is performed in a “non-aggressive” manner so as to avoid degrading the surface layer of the substrate. Subsequently, once a certain amount of deposition has been achieved, a fast deposition step is performed by inhibiting the retarding effect of the selective trap, so as to further increase the rate at which the deposit is made.

[0027] a selective trap for eliminating or significantly reducing the flow of charged particles towards the substrate, while conserving a flow of neutral particles which react to form a passivation layer on the substrate; and

[0035] a selective trap for eliminating or significantly reducing the flow of charged particles towards the substrate while conserving a flow of neutral particles which react to form a passivation layer on the substrate; in which the selective trap comprises a metal grid interposed between the plasma and the substrate, the grid being formed by metal wires crossed at a pitch P that is determined as a function of the characteristics of the plasma to block the flow of charged particles.

Problems solved by technology

Traditional chemical vapor deposition methods, which are in widespread use for depositing films on substrates, lead to the substrates becoming heated to high temperatures.

Such methods can therefore be used only for substrates that withstand high temperatures without significant degradation.

Such a deposit can be applied at a lower temperature, of the order of 250° C. to 400° C. However, most plasma sources lead to performing the method at a temperature which is still too high for certain fragile semiconductor substrates, and the semiconductor components made in this way present progressive aging defects which rapidly make them unsuitable for use.

Rapid and unacceptable aging is also observed on items having a fragile semiconductor substrate such as indium phosphide InP, gallium arsenide GaAs, or even substrates of silicon or of germanium.

Over time, PIN diodes made by present-day methods lose their characteristic of being insulating in the absence of light.

This leads to undesirable leakage current which reduces the overall detection ability of the diode and its sensitivity.

However, such a deposit does not have sufficient effectiveness over time, and the diode progressively loses its character of being insulating in the absence of light.

If the negative bias of the substrate is reduced, e.g. by putting it at a floating potential, that does not suffice to prevent the action of charged particles on the substrate.

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