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Selective Dry Etching Methods and Metrology

IP.com Disclosure Number: IPCOM000238107D
Publication Date: 2014-Aug-01
Document File: 4 page(s) / 150K

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The IP.com Prior Art Database

Abstract

The objective of this paper is to define methods and apparatus by which selective dry etching of semiconductor materials can be achieved. Materials such as silicon oxide, silicon nitride, and amorphous or crystalline silicon, metal oxides, and metal nitrides require selective etching relative to adjacent materials used on the same substrate. As a consequence of the need for selectivity of material A vs. B or vice versa, the dry etching process must be very tunable in terms of the reactant species used, this ‘tunability’ is a key attribute. In addition to high selectivity this process must avoid substrate damage from charged particle exposure. These requirements can be met using the methods outlined in this paper and the results can be measured by methods described in this paper.

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Selective Dry Etching Methods and Metrology

Abstract

    The objective of this paper is to define methods and apparatus by which selective dry etching of semiconductor materials can be achieved. Materials such as silicon oxide, silicon nitride, and amorphous or crystalline silicon, metal oxides, and metal nitrides require selective etching relative to adjacent materials used on the same substrate. As a consequence of the need for selectivity of material A vs. B or vice versa, the dry etching process must be very tunable in terms of the reactant species used, this 'tunability' is a key attribute. In addition to high selectivity this process must avoid substrate damage from charged particle exposure. These requirements can be met using the methods outlined in this paper and the results can be measured by methods described in this paper.

Section 1: Etch chemistry

    One possible chemistry for achieving a tunable process is that using HF, NH3:HF, or NH3:HF:HF. (references?) This chemistry can for example be reactive with silicon, silicon oxide, or silicon nitride. The etchant species typically forms a solid byproduct which may then be sublimed (thermally) from the substrate to remove it. For practical reasons, the etchant species are not supplied to a processing chamber, instead they are formed from precursor gases that are made to react and produce the etching species in situ.

    The possible etchant species are formed from reactions using atomic radicals. These radicals may be formed in a remote plasma and then combined to produce the desired etchant species or combination of species. For example, HF may be formed using precursor gases that can supply a hydrogen atom and a fluorine atom. One way to do this is to dissociate hydrogen or ammonia in a plasma and thereby create atomic hydrogen. Similarly, atomic fluorine may be created by dissociation of suitable molecular gas, such as NF3. The atomic H and F may then combine, either in the plasma or downstream from it to form HF. With the addition of NH3 to the process, the other potential etchant species of NH3:HF and NH3:HF:HF may be formed as well. The added NH3 may be introduced into the plasma or downstream. This is conceptually illustrated in figure 1 below, where the atomic fluorine (F) is created by introducing NF3 into a first remote plasma source (pink box) which dissociates the gas and creates atomic F. Likewise, atomic hydrogen
(H) is created by introducing H2 or NH3 into a second remote plasma source (green box) which dissociates the gas and creates atomic H. These two atomic species combine to form HF when mixed, either in the same plasma or downstream as shown in figure 1. Additional NH3 is introduced downstream in figure 1, but may also come from excess NH3 introduced into the second remote plasma source. The etchant species of NH3:HF and NH3:HF:HF may then be formed through downstream reactions between NH3 and HF molecules (or H and F radicals directly).


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Figure 1 Con...