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New EPD (End Point Detection) method of etching amount control

IP.com Disclosure Number: IPCOM000013441D
Original Publication Date: 2002-Apr-11
Included in the Prior Art Database: 2003-Jun-18
Document File: 3 page(s) / 104K

Publishing Venue

IBM

Abstract

Disclosed is a new endpoint detection method for dry etching process by RIE (Reactive Ion Etcher) that is used in semiconductor manufacturing. This method is effective for the line/via etching in dual damascene process in particular. Usually, optical devices which can detect the variety of photo-emissions of an ion, such as CO or F, through plasma during etching process are used to detect an appropriate endpoint of etching. When top layer film (material A in figure 1 (a) deposited on the other material (material B in figure 1 (a) is etched by RIE, the variety of the photo-emissions will be occurred at the end of elimination of top layer film. This phenomenon enables optical devices to detect an appropriate endpoint of this type of etching. However, optical devices are not suitable for finding an appropriate endpoint during etching in a same material, such as line etching in dual damascene process. This etching process needs to stop etching at the same depth like shown in Figure 1 (b). In this case, optical devices can't detect an appropriate endpoint because there is no variety of photo-emissions through all of etching process. material A Figure 1. Tw o types of requirem ent for the endpoint detection material B

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New EPD (End Point Detection) method of etching amount control

   Disclosed is a new endpoint detection method for dry etching process by RIE (Reactive Ion Etcher) that is used in semiconductor manufacturing. This method is effective for the line/via etching in dual damascene process in particular. Usually, optical devices which can detect the variety of photo-emissions of an ion, such as CO or F, through plasma during etching process are used to detect an appropriate endpoint of etching. When top layer film (material A in figure 1 (a) ) deposited on the other material (material B in figure 1 (a) ) is etched by RIE, the variety of the photo-emissions will be occurred at the end of elimination of top layer film. This phenomenon enables optical devices to detect an appropriate endpoint of this type of etching. However, optical devices are not suitable for finding an appropriate endpoint during etching in a same material, such as line etching in dual damascene process. This etching process needs to stop etching at the same depth like shown in Figure 1 (b). In this case, optical devices can't detect an appropriate endpoint because there is no variety of photo-emissions through all of etching process.

material A

Figure 1. Tw o types of requirem ent for the endpoint detection

material B

(a) Stacked layer structure

material A

(b) Single layer structure

On the other hand, our proposed method is very useful to detect an appropriate endpoint in above case. Our method propose to use a cumulative amount of a molecule that is emitted as by-product during dry etching, like SiF4. When SiO2 (silicon dioxide) film is being etched by NF3(nitrogen trifluoride), SiF4 (silicon tetrafluoride) is emitted as by-product based on the below reaction formula.

2NF3 -> N2 + 3F2

SiO2 + 2F2 -> SiF4 + O2

To measure the cumulative amount of emitted SiF4 from the beginning of etching enables us to estimate the amount of removed SiO2 from the beginning of etching. If the etching is stopped when the cumulative amount of emitted molecule reaches up to a target amount, our proposed method can be used as one of an endpoint detection method of RIE.

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Figure 2 shows our experimen...