Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2000-07-12
2001-09-18
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S405000, C392S418000, C118S724000, C414S217000
Reexamination Certificate
active
06291801
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a method and an apparatus for the rapid thermal processing of at least one workpiece and more particularly, relates to a method and an apparatus for the rapid thermal processing of at least one workpiece which can be rapidly heated/cooled by exposing the workpiece to a time dependent, continuous convolution of nearly black body distributions of electromagnetic radiation in the presence of processing gases or in vacuum.
BACKGROUND OF THE INVENTION
In the high volume fabrication of semiconductor integrated circuit devices, the technique of rapid thermal processing (RTP) or rapid thermal annealing (RTA) has become an important processing step in the fabrication of IC devices. In a conventional RTP process, a workpiece is heated by a heat source such as a plurality of tungsten-halogen lamps or arc lamps which provides almost instant heating effect on a workpiece such as a semiconducting substrate in the shape of a wafer In most RTP methods, the heat treatment of a wafer takes place in a single process chamber with the appropriate process gas flow and composition.
A typical single-wafer RTP chamber
10
is shown in FIG.
1
A. In RTP chamber
10
, an outer chamber wall
12
made of metal is cooled by ambient air and liquid circulating in cooling channels
14
. The wafer
18
and the wafer supports
20
are situated inside a fused silica inner chamber wall
24
equipped with a process gas inlet
26
and outlet
28
. The wafer
18
supported by the fused silica supports
20
is heated radiatively by banks of lamps
22
of either tungsten-halogen or arc-type lamps.
The mode of heating provided by the RTP chamber
10
shown in
FIG. 1A
is dynamic in that the wafer never reaches thermal equilibrium with the heating elements. As a result, the temperature uniformity over the wafer surface depends on the heating rate of the wafer. Furthermore, the radiative coupling between the wafer and the heating lamps varies greatly with temperature due to the fact that the emissivity of silicon depends strongly on temperature up to about 700° C. In addition, the radiative coupling depends on the physical state of the wafer front and back surfaces. During a typical RTP process as that shown in
FIG. 1A
, the wafer
18
is heated on both the top and the bottom surfaces and heat from the wafer radiates to cold wall surfaces. Based on this simultaneous heating and cooling, the rate of wafer heating and the wafer final temperature depend strongly on the wafer emissivity, which is in turn a strong function of the wafer surface structure, the wafer backside textures film stack, and wafer temperature.
Another conventional lamp based RTP chamber
30
is shown in FIG.
1
B. In this chamber design, a semiconductor wafer
32
to be processed is placed on a susceptor
34
which can be raised up or down by an elevator
36
. The lamp heaters
40
which are enclosed in a reflective dome
42
direct radiative energy toward the wafer
44
. Process gases are pumped into chamber
46
through gas inlet
48
and exhausted through outlet
52
. It should be noted that, unlike the chamber construction shown in
FIG. 1A
, the susceptor
34
is heated simultaneously with the wafer and aids in achieving temperature uniformity across the workpiece.
The present trends in semiconductor manufacturing indicate that in the near future the wafer heating rate and cooling rate will increase and that the time interval during which a wafer is maintained at a desired peak temperature will decrease substantially. The trends are dictated by high performance logic circuits that are based on very shallow junctions that must be prepared in a fabrication process with stringent thermal budget limitations. Moreover, in today's highly competitive environment, the manufacturing of semiconductor devices continues to strive for efficiency and throughput gains and thus, a more uniform and higher throughput RTP process is desired.
Conventional RTP chambers such as those shown in
FIGS. 1A and 1B
have performance limitations that limit their ability to meet future requirements of significantly faster heating rates. On the one hand, from a performance consideration, the ramp rate of conventional RTP chambers is limited by the requirement of temperature uniformity in the highly transient environment of conventional RTP chambers, which require feed-back control and independently addressable lamps in order to achieve an acceptable degree of temperature uniformity across the wafer workpiece. On the other hand, at the outer limits of tool performance the rate at which the wafer of a given size can be heated is limited by the time it takes for the lamp filament to achieve operational temperature and furthermore, by the radiant flux at the wafer. The latter is limited by how closely the heating lamps can be stacked together and the maximum radiant power flux of each lamp which is limited by the melting point of the tungsten filament and the softening point of the lamp's conventional fused silica enclosure. It has been found that the maximum achievable heating rate for an industry standard silicon wafer of 200 mm diameter in a conventional, lamp-based RTP chamber is limited to about 150° C./sec.
In recent years, RTP has also been conducted in vertical hot wall furnace-type chambers in limited applications. One of such devices is shown in
FIG. 1C. A
hot wall RTP furnace
50
is closed on all but one side (the bottom) through which wafers
54
are introduced and subsequently removed from the furnace upon completion of the thermal cycling treatment. The hot wall RTP furnace
50
has a vertical axis along which the wafers move by the action of elevator
66
on a wafer carrier
46
while maintaining the plane of the wafers perpendicular to the vertical ax of the chamber
50
. The furnace
50
is closed at the top and is equipped with a top heater
58
, and closed on the sides where side upper heaters
62
are mounted thereto. The furnace
50
has a chamber
64
defined by a fused silica chamber wall
76
and may include additional heating zones
68
, each of which is maintained at a specific temperature. The wafers
54
, positioned on wafer carrier
46
can be moved into or out of the chamber
64
by an elevator
66
. The chamber
64
is further heated by lower side heaters
68
to facilitate the control of chamber temperature. Various process gases may enter the chamber
64
through gas inlet
72
and be exhausted from the chamber through gas outlet
74
. During operation, wafers
54
are slowly transported vertically through one or more temperature zones coming to a full stop at a desirable location where the wafers achieve a temperature that is much less (100-500° C.) than that of the surrounding hot walls. After a suitable amount of time which may vary from several seconds to several minutes, the wafers can be withdrawn and allowed to cool. Limited by its basic design, the existing hot wall RTP furnace cannot achieve very high heating rates and short dwell times at a desirable wafer temperature.
Neither the lamp-based nor the hot wall-based RTP furnaces that are presently available can be used to process large workpieces (or wafers) at heating rates that are much higher than 150° C./sec and at dwell times at peak temperatures that are much shorter than one second. Therefore, prevailing art in current practice cannot meet the processing requirements for high performance logic circuits.
It is therefore an object of the present invention to provide a method and an apparatus for RTP that does not have the drawbacks and shortcomings of conventional lamp-based or hot wall-based RTP furnaces.
It is another object of the present invention to provide a method and an apparatus for RTP in which the temperature of at least one workpiece can be increased and decreased uniformly at rates that are much greater than 150° C./sec.
It is a further object of the present invention to provide a method and an apparatus for RTP which can be used to provide similar heating and cooling rates to wafers that are o
Guidotti Daniel
Lee Kam Leung
Fuqua Shawntina
International Business Machines - Corporation
Trepp Robert M.
Tung Randy W.
Walberg Teresa
LandOfFree
Continual flow rapid thermal processing apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Continual flow rapid thermal processing apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Continual flow rapid thermal processing apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2518992