Speaker
Description
Beside LGADs are now considered a promising solution for 4D-tracking thanks to the excellent timing resolution, in some HEP applications the latter should come with a state-of-the-art spatial resolution of the segmented sensors. The currently available LGAD technology typically features large pixels, in the range 500 µm – 1 mm, due to the presence of a gain-loss region between adjacent pixels, typically 50–100 micrometers wide, in which the gain is partially or completely suppressed.
In this contribution, we will discuss the segmentation issues in standard LGAD technology and we will present new segmentation strategies, developed by FBK and INFN, aimed at producing sensors with small pixels (50-200 um) and high fill factor.
Resistive AC-coupled detectors (RSD) are an evolution of LGADs where a not-segmented resistive n-well and multiplication layers have been implemented. In this scheme, the segmentation is provided by the metal read-out pads, AC-coupled to the resistive n-well via a thin dielectric layer. In the first batch, sensors with very fine pitch (50, 100, and 200 µm) and 100% fill factor have been produced and characterized in terms of gain, timing, and spatial resolution.
The second proposed technology is the so-called Trench-Isolated LGAD (TI-LGAD). In this new design, the standard inter-pixel isolating structures (Junction Termination Edge) has been replaced with a trench, physically etched in the silicon and filled with silicon oxide, which provides electrical isolation between adjacent pixels. Numerical simulations show that this isolation technology is effective in reducing the gain-loss inter-pixel region to less than 5um, an order of magnitude less than in standard LGADs, without affecting the other detector performance. The first produced TI-LGAD samples with 250 µm pitch have been characterized and the main results demonstrate that the new trench isolation structure: i) provides electrical isolation among pixels; ii) supports high-bias voltage (> 300V) without edge-breakdown; iii) strongly increases the pixel fill-factor paving the way at the developing of LGADs sensors with pitch < 100 um.
| Submission declaration | Original and unpublished |
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