AVS 51st International Symposium
    Manufacturing Science and Technology Tuesday Sessions
       Session MS-TuP

Paper MS-TuP2
A New Way to Get Steady Trichlorosilane (TCS) Vapor Flow for EPI Deposition Process

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: Z. Lu, STMicroelectronics, Inc
Authors: A. Sidhwa, STMicroelectronics, Inc
Z. Lu, STMicroelectronics, Inc
S. Bansal, STMicroelectronics, Inc
C. Cross, STMicroelectronics, Inc.
Correspondent: Click to Email
TCS has been used for many years as silicon source in high temperature EPI applications. It is still preferred in many applications since its low material cost and high deposition rate. In TCS EPI process, hydrogen (H2) is frequently used as carrier gas to convert TCS from liquid to vapor and carry TCS vapor to reaction chambers. The flow of TCS vapor is normally controlled by a Liquid Vapor Controller (LVC). It requires stable TCS liquid temperature to achieve good repeatability of TCS vapor flow. If both low and high TCS vapor flows are required, two LVCs have to be installed in parallel to achieve both low and high flow controls. A traditional LVC controls TCS vapor flow by measuring the mass difference between incoming gas (H2) and outgoing (H2+TCS) of the controller. It can provide steady TCS vapor flow if the temperature of TCS liquid is stable. Since TCS vapor pressure is extremely sensitive to TCS temperature, LVC can no longer provide steady TCS flows if TCS temperature fluctuates. The reason is that the temperature of outgoing gas (H2+TCS) and TCS partial pressure fluctuate according to the fluctuating TCS liquid temperature. In order to resolve the overhead/delay of TCS minibubbler/ conducting lines and their temperatures, a Piezocon flow controller was introduced and installed downstream of the TCS minibubbler. Since Piezocon controller calculates the accurate TCS flows in real time and its located downstream of the whole minibubbler unit, it becomes independent of the TCS liquid temperature. Piezocon controller also has high accuracy and repeatability in a wide range of vapor flows, which includes our low and high TCS applications. Once it combines with a digital MFC, which also has high repeatability in both low and high flow, the combination would provide us very steady TCS vapor flows in both low and high ranges.