In-Situ Patiterning and Regrowth of InP Based Heterostructures Using a Native Oxide Mask
- PDF / 1,159,708 Bytes
- 5 Pages / 420.48 x 639 pts Page_size
- 15 Downloads / 233 Views
IN-SITU PATITERNING AND REGROWTH OF InP BASED HETEROSTRUCTURES USING A NATIVE OXIDE MASK Y. L. Wang, L. R. Harriott, and H. Temkin AT&T Bell Laboratories, 600 Mountain Ave., Murray Hill, New Jersey 07974 ABSTRACT We have successfully used an ultrathin (20-50 A) native oxide layer on the surface of InP as an etch mask for transferring patterns onto the substrate. The oxide mask is grown in situ in 02 atmosphere, and the mask pattern is created by locally removing the oxide with a focused ion beam. Depending on the thickness of the mask, the required ion dose varies from 2x10 14 to 2x10 15 Ga/cm 2 . C12 etches the exposed areas selectively . Features as deep as 3 microns have been produced with such an ultrathin mask. High quality InGaAs and InP epitaxial layers have been overgrown on such patterned substrate. We have studied the formation and desorption of the oxide mask with Auger analysis. We also demonstrate that the secondary charged particle emission from a substrate during ion exposure provides a useful signal for the determination of the required dose. INTRODUCTION In situ pattern formation and epitaxial crystal growth conducted in a multi-chamber vacuum system has gained a lot of attention recently [1-8]. There are two driving forces behind this type of research. First, the conventional patterning technique, which uses photolithography, organic resist and wet chemical etching, usually leads to a contaminated substrate surface that is not compatible with subsequent overgrowth by molecular beam epitaxy (MBE). Therefore, a vacuum lithography process that is intrinsically compatible with MBE provides an attractive alternative. Second, the unprecedented control over the thickness of a heterostructure provided by MBE is yet to be complemented by a technique that allows the fabrication of structures with comparable lateral precision. Selective area epitaxy would be such a growth technique, but it remains to be demonstrated for III-V materials [9]. A vacuum lithographic process using a combination of radiation and/or chemicals to selectively remove material from the substrate provides an alternative. Since focused electron and ion beams are available, researchers have been using them to study the feasibility of a highspatial-resolution in situ lithography. In order to address, at least partially, the problem of low throughput intrinsic to any focused beam writing technique, we have chosen to create the desired pattern on an ultrathin mask [2,5,6] with a focused ion beam (FIB), and then transfer it deep into the substrate by dry etching. The current of a commercial scanning electron beam focused to 100 A diameter, and that of a ion beam focused to 1000 A are both on the order of 100 pA (1012 particles/hr ). This small current makes any process requiring doses higher than 1010 particles/cm 2 too time consuming, even in a research environment where production efficiency is not a major concern. Because ions are much heavier than electrons, they are more effective in exposing the mask. By writing on an ultrathin mask wit
Data Loading...
