1. Field of the Invention
The present disclosure relates generally to semiconductor fabrication, and more particularly to ion implantation processes during semiconductor fabrication.
2. Description of the Related Art
Semiconductor-on-insulator (SOI) structures have advantages over conventional bulk substrates such as elimination of latch-up, reduced short-channel effects, improved radiation hardness, and dynamic coupling, among others. Because of these advantages, semiconductor device manufacturers commonly form metal-oxide semiconductor field effect transistors (MOSFETs) on SOI structures.
In a typical MOSFET, a source and a drain are formed in an active semiconductor region by implanting N-type or P-type impurities in the layer of semiconductor material. Between the source and the drain is a channel (or body) region, above which is a gate electrode. Unfortunately, MOSFETs formed on SOI structures often experienced a floating body effect (FBE), which lead to the development of tied-body construction techniques, particularly in the manufacture of partially-depleted SOI devices such as the t-type or “hammer head” gate electrode seen in
While tied-body transistors such as t-type transistor 100 avoid FBE problems by tying the transistor body to a contact CMOS scaling, has resulted in increased resistance due to attendant reductions in the cross-sectional dimensions of certain conductive structures, as well as other factors. In t-type transistor 100, there are several components of body resistance: a) contact 5 resistance, b) resistance along the width of the transistor 100 under the gate structure 9, and c) pinch off resistance under the hammer head 10 along the boundary of the body tie implant from transistor S/D implant.
Of the three resistance components named above, the contact resistance is generally the smallest portion of the total resistance. The resistance along the width of the gate structure 9 is decreased somewhat by the halo implant 6, also known as pocket implants, which normally receives a dopant dose level about one order of magnitude greater than the well implant dose level. Well implant doses are trending downward in current manufacturing technology, which has led to an increase in resistance under the polysilicon hammer head 10 such that this resistance component has begun to dominate the body resistance.
In addition, resistance problems can be exacerbated by depletion phenomena, such as when source/drain extension depletion areas create a “pinch off” under the hammerhead 10, as shown in
Therefore, a method which overcomes these problems and limitations would be useful.
The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. Other advantages, features and characteristics of the present disclosure, as well as methods, operation and functions of related elements of structure, and the combinations of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of the specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein:
The present disclosure provides a method for ion implantation for producing transistors such as a t-type transistor with reduced body resistance. The method comprises the steps of placing a semiconductor wafer comprising a gate edge in an ion implantation device. The semiconductor wafer is then oriented to a first position relative to a beam path of the ion implantation device in order to obtain a substantially non-orthogonal twist orientation between the beam path and the gate edge. Following this orientation to the first position, at least one ion species, for example an n-type or p-type dopant, is implanted into a first implantation region of the wafer. The wafer is then rotated to a second substantially non-orthogonal twist orientation, where another ion implantation is conducted. This process continues in the same manner, such that further substantially non-orthogonal twists and ion implantations are conducted, until the desired number of implantation areas is created.
The method overcomes the limitations of previous implantation methods by preventing an increase in resistance caused by depletion regions associated with S/D extensions overlapping in the region between the contact and gate channel in body-tied SOI transistors. The method thus reduces the total body resistance in a transistor, which increases the overall performance characteristics of the device. In addition, the present method is appropriate for integration into existing manufacturing process lines for advanced sub-micron integrated circuit semiconductor devices without the requirement for additional capital expenditures.
The present disclosure is best understood with a reference to the specific embodiments illustrated in
Following twist orientation to the first position, an n-type or p-type dopant is implanted into a first implantation region of transistor portion 200 of the wafer. This implantation results in the creation of an initial portion of a halo or pocket implant region 26 located in the active region under hammerhead 20 of the transistor device portion 200 beyond that of the S/D extension. Additional rotations of portion 200 to beam paths indicated by the arrows numbered 32, 33, and 34 in
In an embodiment, the ion species utilized during halo region 26 implantation is a n-type dopant such as elements located in group 15 (VA) of the periodic table, e.g., phosphorus (P). In another embodiment, the ion species implanted is a p-type dopant, e.g., elements found in group 13 (IIIA) of the periodic table, such as boron (B). These pocket implantations occur at medium beam currents and energies. For example, for boron (B), the beam energy ranges from 7 keV to 15 keV, while the beam energy ranges for arsenic (As) are from 40 keV to 90 keV. The halo or pocket implantation dose can range from 1013 cm−2 to 1015 cm2, with 1013 cm−2 being a typical delivered dose.
The substantially non-orthogonal twist orientation can be 45 degrees relative to the gate 29 edge, as seen in
As seen in
The method and apparatus described herein provides for a flexible implementation. Although the invention has been described using certain specific examples, it will be apparent to those skilled in the art that the invention is not limited to these few examples. For example, the disclosure could be used to create other features not specifically illustrated. In addition, the invention can be employed with other device technologies to realize reduced resistance characteristics in implantation processes during device manufacture. Additionally, various types of ion implantation devices are currently available which could be suitable for use in employing the method as taught herein. Note also, that although an embodiment of the present invention has been shown and described in detail herein, along with certain variants thereof, many other varied embodiments that incorporate the teachings of the invention may be easily constructed by those skilled in the art. Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims. Accordingly, the present invention is not intended to be limited to the specific form set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the invention.
Number | Name | Date | Kind |
---|---|---|---|
5492847 | Kao et al. | Feb 1996 | A |
5811855 | Tyson et al. | Sep 1998 | A |
5821575 | Mistry et al. | Oct 1998 | A |
5874329 | Neary et al. | Feb 1999 | A |
5920093 | Huang et al. | Jul 1999 | A |
5973364 | Kawanaka | Oct 1999 | A |
5985726 | Yu et al. | Nov 1999 | A |
6005285 | Gardner et al. | Dec 1999 | A |
6191449 | Shino | Feb 2001 | B1 |
6194278 | Rengarajan | Feb 2001 | B1 |
6309933 | Li et al. | Oct 2001 | B1 |
6399989 | Dockerty et al. | Jun 2002 | B1 |
6448163 | Holbrook et al. | Sep 2002 | B1 |
6596554 | Unnikrishnan | Jul 2003 | B1 |
6630376 | Krishnan et al. | Oct 2003 | B1 |
6703280 | Kim et al. | Mar 2004 | B1 |
6794717 | Matsumoto et al. | Sep 2004 | B1 |
20020149058 | Culp et al. | Oct 2002 | A1 |
20030052347 | Fung | Mar 2003 | A1 |
Number | Date | Country |
---|---|---|
497216 | Jan 1992 | EP |
497216 | Jan 1992 | EP |
535917 | Sep 1992 | EP |
535917 | Sep 1992 | EP |
905789 | Jun 1996 | EP |
899793 | Jun 1998 | EP |
899793 | Jun 1998 | EP |
Number | Date | Country | |
---|---|---|---|
20040241969 A1 | Dec 2004 | US |