Coating apparatus – Gas or vapor deposition – Multizone chamber
Reexamination Certificate
2001-08-07
2003-11-18
Hassanzadeh, Parviz (Department: 1763)
Coating apparatus
Gas or vapor deposition
Multizone chamber
C156S345310, C438S907000, C414S941000
Reexamination Certificate
active
06648974
ABSTRACT:
The present invention relates to a device for handling substrates, in particular semiconductor slices, in an apparatus used for the chemical vapour deposition (CVD) of semiconductor material onto the said substrates and a method for operation of the said device. It especially relates to a device for handling substrates used in an epitaxial reactor and, in particular, relates to an epitaxial reactor for performing the chemical vapour deposition (CVD) of materials onto the said substrates, preferably silicon substrates used in the manufacture of semiconductor components, such as chips for integrated circuits.
More particularly, the present invention relates to a device used in epitaxial reactors such as those covered by the International Patent Application WO 96/10659 filed on Sep. 14, 1995, with the title “Epitaxial reactor provided with flat disk-shaped susceptor and having a gas flow parallel to the substrates”. With the aid of the present device, the abovementioned epitaxial reactor becomes a reactor of the “cassette-to-cassette” type because the cassettes containing the as yet unprocessed substrates are positioned inside the reactor and, during a product loading cycle, a first mechanized arm, or robot, not forming part of the present invention, is used to transport the substrates from a storage rack or “cassette” to a purging chamber and a second mechanized arm, or robot, carrying externally a gripping and transportation means, forming the subject of the present invention, for transporting the substrates from the purging chamber to the susceptor, whereas, during an unloading cycle, the second robot transports the substrates from the susceptor to the purging chamber and subsequently the first robot transports the said substrates, which have undergone processing, from the purging chamber to one of the cassettes, all of which occurring without manual intervention of an operator supervising operation of the reactor.
The invention may be applied in particular to cold-wall CVD systems, preferably, to reactors which are able to provide epitaxial growth on substrates or silicon slices which are used in the manufacture of semiconductor devices by means of deposition involving chlorosilane vapour pyrolysis.
The commercially most widespread epitaxial reactors can be divided into two main categories:
a) single-slice reactors, which are able to process a single slice at a time; and
b) batch-type reactors, which are able to process a plurality of substrates or slices at the same time.
The heating systems used for the abovementioned reactors may be classified as two types: lamp-type heating systems and medium or high frequency induction heating systems.
The batch-type reactors which are most widespread on an industrial level are essentially of two types: those which use the so-called “barrel” system, i.e. with a prismatic or truncated-pyramid susceptor, and those which use the “pancake” system, with a substantially flat disk-shaped susceptor.
Typically, at present, batch-type reactors are of the manual loading type, whereas single-slice reactors are of the automatic loading type.
In automatic-loading reactors, the substrate, or slice, may be handled in different ways which offer both advantages and disadvantages. Handling of the substrates is particularly critical in the sector of semiconductors and, in particular, in epitaxial reactors where there are temperature-related problems and problems resulting from particle contamination.
Generally, each substrate or slice has a bottom side (back), a top side (front) and a side wall (edge). The dimensions of the front and back are normally between 75 and 300 mm, and even as much as 400 mm, while the dimensions of the edge are smaller than or near to 1 mm. The front is the most important part of a slice because it is the part where the chemical reaction process, i.e. deposition, takes place.
For the abovementioned reason, it is important to avoid all contact between the front and any type of tool used for handling, because any contact, even of the slightest nature, causes imperfections in the crystal lattice. If the imperfections are formed during loading, they are magnified by the ensuing heat process; however, imperfections introduced during unloading must also be avoided.
Basically, it may be stated that contact, even of an accidental nature, with the front of the slice is nor permitted at any time. On the other hand, within certain limits, contact with the back and with the edge of the said slice is permitted.
Therefore, in order to move a slice, it is possible to act via the front (without any direct contact, however), the back or the edge.
Basically, there is only one system which allows handling from the front, without contact between tool and slice, and it is the system based on the Bernouilli effect, whereby, by providing a suitable gripping tool (end effector), it is possible, by blowing filtered inert gas, towards the front of the slice, to create an attraction effect for the slice, which, in the horizontal position, is sufficient to overcome the weight of the slice, keeping it suspended.
However, accidental contact between the edges of the slices and some fixed points of the tool necessarily occurs because, in the absence of a support and hence friction, it is necessary to have some fixed points for fixing the slice underneath the gripping tool, although this fact is not particularly negative.
During unloading, in order to raise the slice from the cavity inside which it is seated, it is necessary to overcome, in addition to its own weight, also a slight vacuum which is formed between the cavity and the said slice. Since this is not possible by means of the Bernouilli effect alone, it is necessary to avoid the formation of this vacuum, for example by means of a network of tiny channels which are formed in the cavity underneath the slice. This technique is excellent, but is better suited for lamp-heated reactors, rather than induction-heated reactors, because the presence of non-conducting channels in the graphite mass of the susceptors would adversely affect the uniformity of heating of the slices. Moreover, this technique is not particularly compatible with reactors of the batch type because, although a flow of inert gas helps in keeping the front of the slice clean during handling, it is probably harmful for the adjacent slices, especially if handling takes place in the vicinity if the susceptor, because the flow of gas moves any dust particles which are present in movement.
Another system consists in handling the slices from the back, although there is the problem that the back of the slice is accessible when the latter is inside the cassette, but is no longer so when the slice is located on the susceptor. In order to overcome this drawback, it is possible to form through-holes in the susceptor and raise the slice, when required, by means of small supports, passing through the holes, which are able to move up to perform raising and move down to allow seating of the slice in the susceptor. In fact, during the loading cycle, the supports are raised and the slices rested on them. Then the supports are lowered and the slices are deposited in the corresponding seats on the susceptor. During the unloading cycle, the supports are raised, together with the slices; a tongue or gripping tool (end effector) made of suitable material is then introduced underneath the slice and the latter removed. If greater stability is required, it is possible to brake the slice by applying a slight vacuum between slice and gripping tool. However, this technique, although being effective, in practice can only be properly applied to reactors of the lamp-heated type, while it is probably unacceptable for induction-heated reactors because the holes formed in the graphite of the susceptor would result in a non-uniform current flow and hence heating.
Another known system is that which allows the slice to be gripped along its external diameter, or edge, at two or more points using movable gripping systems, such as mechanical grippers. However, this system cannot be
Ogliari Vincenzo
Pozzetti Vittorio
Preti Franco
Dort David B.
Hassanzadeh Parviz
Hickman Paul L.
LPE SpA
Moore Karla
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