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Horizontal Sample Attachment For Vertical Sample Ellipsometer

IP.com Disclosure Number: IPCOM000049465D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 5 page(s) / 30K

Publishing Venue

IBM

Related People

Chastang, JC: AUTHOR [+4]

Abstract

1. Introduction- In most ellipsometric arrangements the samples are either horizontal or vertical. Sketches of both arrangements (in the so-called PSCA configuration)(*) are shown by Figs. 1 and 2, respectively. Fig. 1 shows a horizontal sample ellipsometric arrangement. Fig. 2 shows a vertical sample ellipsometric arrangement. In general, instruments which require vertical samples do not lend themselves easily to the examination of horizontal samples. Figs. 1 and 2 include sources of a beam, a polarizer P, and a sample to which normal line N is drawn. The reflected beam passes through compensator C and analyzer A to means for detection D.

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Horizontal Sample Attachment For Vertical Sample Ellipsometer

1. Introduction- In most ellipsometric arrangements the samples are either horizontal or vertical. Sketches of both arrangements (in the so-called PSCA configuration)(*) are shown by Figs. 1 and 2, respectively. Fig. 1 shows a horizontal sample ellipsometric arrangement. Fig. 2 shows a vertical sample ellipsometric arrangement. In general, instruments which require vertical samples do not lend themselves easily to the examination of horizontal samples. Figs. 1 and 2 include sources of a beam, a polarizer P, and a sample to which normal line N is drawn. The reflected beam passes through compensator C and analyzer A to means for detection D.

The following study describes two simple optical attachments which, when implemented in an ellipsometer using the so-called PSCA configuration (1) and designed to handle only vertical samples, will enable this instrument to be used for the examination of horizontal samples as well. The ellipsometer which will incorporate this attachment is a Rudolf RR 2000 model, used for oxide layer growth and corrosion experiments. Future work will include the study of oxide layer growth in lead-tin and lead-indium solders at temperatures above their melting point; hence the requirement that the sample be horizontal.

The polarization characteristics of these attachments are examined. It is shown that their influence on the results can easily be taken into account or even cancelled. 2. Description of Proposed Attachments

The current vertical sample arrangement and a new horizontal sample arrangement, which includes the simpler of the proposed attachments, are shown in Figs. 3 and 4, respectively. Fig. 3 is a horizontal sample arrangement. The two attachments, which are shown in greater detail in Figs. 4A and 4B, consist of two identical fused silica prisms 1 and 2 working at their minimum deviation. The first prism 1 deviates the incoming beam by 20 degrees so that the incidence on the sample is 70 degrees (as in the vertical arrangement). The second prism 2 deviates the outgoing beam by 20 degrees also, which restores the original propagation direction of the beam. In the horizontal arrangement, the optical axes of the polarized and the compensator analyzer portions of the ellipsometer are now aligned.

The second attachment shown in Fig. 4B incorporates two half wave plates HW1 and HW2 whose axes are at 45 degrees from the plane of symmetry of the system. 3. Characteristics of the Prisms

The material chosen for the prisms is the best grade of fused silica because of its excellent optical properties (in particular, negligible residual birefringence), great resistance to mechanical wear and abrasion, and low susceptibility to chemical attack.

At minimum deviation, the propagation of a light ray through a prism is symmetrical with respect to the plane which, passing through the apex line, bisects the prism (Fig. 5). In this configuration we also have(2...