Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-12-13
2003-09-02
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S405000, C219S411000, C392S416000, C392S418000, C118S724000, C250S492200
Reexamination Certificate
active
06614005
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and a method for the thermal treatment of substrates, especially semiconductor wafers, including at least one heating device for heating at least one substrate by means of electromagnetic radiation, whereby the heating device includes at least two arc lamps.
An apparatus of the aforementioned type is known, for example, from U.S. Pat. No. 4,698,486, according to which a semiconductor wafer that is located in a reaction chamber is initially heated by an arrangement of quartz halogen lamps. After the wafer has reached a certain temperature, an additional lamp arrangement, namely a high-power pulsed lamp arrangement, is used for heating the wafer. The pulsed lamp arrangement is used only for a short period of time, whereby the surface temperature of the wafer is raised to a temperature in the vicinity of the melting point of the semiconductor material. Due to the short periods of use of the pulsed lamps, the temperature of the wafer is influenced by the pulsed lamps only in the region of the wafer surface, which leads to a non-homogeneous temperature distribution over the thickness of the wafer. The quartz halogen lamps, as well as the pulsed lamps, are disposed in a highly reflective chamber that surrounds the reaction chamber and that is built up in the form of a kaleidoscope. In order to achieve a homogeneous temperature distribution on the surface of the wafer in the reaction chamber, it is important with this known apparatus that the spacing between the respective lamps and the surface of the wafer be greater than or at least equal to the diameter of the reflective chamber. The spacing between the respective lamps and the wafer surface, in particular with an apparatus that is suitable for heating both sides of the wafer, leads to a large overall size of the apparatus. With the ever increasing wafer diameters, such as for example 300 mm wafers, it is therefore necessary to have a very large reflective chamber, which leads to high manufacturing and maintenance costs of the apparatus.
From U.S. Pat. No. 4,398,094 as well as U.S. Pat. No. 5,336,641 respective apparatus are known for the thermal treatment of semiconductor wafers, according to which in each case an individual arc lamp having a mirror is used as the heat source. The arc lamps used as the heat source are thereby generally high-power arc lamps having an expensive construction and a complicated cooling device. Due to the use of an individual lamp, it is not possible to achieve a homogeneous thermal treatment of the wafer.
From DD-A-295950 it is furthermore known to use UV radiating systems having varying configurations in combination with glow lamps for the thermal treatment of semiconductor wafers. In this connection, a metallic vapor, low-pressure UV source is used that contributes only insignificantly to the overall radiation density of the heating device. The object of the UV radiation system is not the actual heating of the wafer, but rather the promotion of photochemical reactions in conjunction with thermally activated processes via the UV irradiation.
Most of the presently commercially available apparatus for the thermal treatment of substrates utilize exclusively glow lamps for the thermal treatment of semiconductor wafers. However, these lamps have the drawback that the radiation of the glow lamps is only very slightly absorbed at wafer temperatures below 600° C. This is due to the characteristic spectrum of the glow lamps, which at wave lengths of about 1000 nm is at its maximum. The rate of absorption of an Si semiconductor substrate is, however, for wave lengths in this range greatly dependent upon temperature and varies from about 0.1 to 0.7. Only at temperatures of more than 600° C. is the rate of absorption in this wave length range nearly independent of wave length. The result of this is that the energy of the glow lamps can be effectively absorbed only at a wafer temperature of greater than about 600° C.
Proceeding from the known apparatus, it is an object of the present invention to provide an apparatus of the aforementioned type that enables an effective economical and homogeneous thermal treatment of substrates.
SUMMARY OF THE INVENTION
Pursuant to the present invention, this object is realized with an apparatus of the aforementioned type in that the radiation characteristics for each arc lamp can be individually controlled by a control device, and in that the electromagnetic radiation of the arc lamps contribute substantially to the power density of the electromagnetic radiation of the heating device. The use of arc lamps, which contribute significantly to the power density of the electromagnetic radiation of the heating device, has the advantage that these lamps radiate in a spectral range in which, for example Si wafers, have the highest absorption, and in particular already at room temperature. Thus, as a result of the arc lamps an effective heating in particular of semiconductor wafers is possible even at room temperatures. Due to the possibility of an individual control of the arc lamps, the spatial radiation field of the lamps can be established, which enables a homogeneous radiation distribution and thus a homogeneous temperature distribution upon the wafer surface. Due to the ability to set the spatial radiation field, the heating device, including the arc lamps, can be disposed in the vicinity of the substrate that is to be treated, and it is not necessary to maintain a certain spacing between the heating device and the substrate, which spacing is prescribed by the diameter of the treatment apparatus, in order to be able to carry out a homogeneous substrate treatment. As a result, the overall size of the apparatus, and the cost connected therewith, can be considerably reduced.
For an optimal adaptation of the radiation characteristics of the apparatus to the process conditions, especially to the substrate that is to be treated, the operating mode and/or the lamp current of the arc lamps is advantageously individually controllable. The arc lamps are advantageously controllable in a direct current operation and/or in a pulsed manner as flash or pulsed lamps. For an effective use of the arc lamps, these contribute at least {fraction (1/10)} to the power density of the heating device. For a good, effective cooling of the arc lamps, these are preferably fluid cooled. As a result of a good cooling of the arc lamps, their life expectancy can be extended considerably.
In order to achieve a good, homogeneous temperature distribution on the substrate that is to be treated, the gas or glow discharge zone of the arc lamps corresponds essentially to a dimension of the substrate, such as the edge, length or the diameter of the substrate. It is preferably longer than the dimension of the substrate. The arc lamps are preferably disposed in the region of the outer periphery of the substrate in order to be able to easily control the temperature distribution. Arc lamps are particularly suitable in this region, because they have a rapid response characteristic.
The heating device preferably has a bank of lamps having at least two rod-shaped lamps that are disposed nearly parallel to one another. In this connection, the lamps of the bank of lamps have, preferably in addition to the arc lamps, glow lamps that enable an economical heating of the substrates. Pursuant to one specific embodiment of the invention, the glow lamps and the arc lamps have essentially the same dimensions so that they can be interchanged in order to be able to specifically adapt the radiation characteristics within the apparatus to the respective substrate or the respective thermal process. The glow lamps and the arc lamps advantageously have essentially the same lamp power, so that the same cooling system can be utilized for the lamps. For an increased effectiveness of the apparatus, the heating device is surrounded by a chamber that at least in stages reflects the electromagnetic radiation, so that radiation of the lamps that is not directed directly upon the s
Blersch Werner
Hauf Markus
Mader Roland
Walk Heinrich
Becker R W
Fuqua Shawntina
R W Becker & Associates
STEAG RTP Systems GmbH
Walberg Teresa
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