Tip, in particular for a vacuum pipette.

p0001The invention relates to the technical sector of the manufacture of integrated circuits. More particularly, the invention relates to tools vacuum pipette the type used for handling semiconductor wafers, such as silicon wafers.

p0002Indeed, during the fabrication of integrated circuits, it is often necessary to capture and manipulate semiconductor wafers on which circuits are fabricated. Different tools can be used for this purpose.

p0003Can be used, for example, vacuum pipette whose tip grip is described in US patent 4,981,315 belonging to the owner of this application.

p0004Although the tips described in this patent are satisfactory, however it appears at least one problem during the fabrication of integrated circuits, a problem that is not solved.

p0005Indeed, very often during the manufacturing process, the pellets are charged with static electricity, which has the effect of attracting particles at the circiuit having the opposite charge. Such particles, if they are actually in contact with the wafer may damage the Emerging circuits on the wafer, causing various disturbances of operation.

p0006A grounded vacuum tools such as pipettes, is a known technique that avoids this disadvantage. However, this technique generates a sudden static discharge when the vacuum tool, normally grounded, comes in contact with a pellet charge, which can, again, result in damage to the circuit.

p0007Also exemplary WO 90/12977 teaches a connecting device between the body and the nozzle of a vacuum pipette. This device uses a means capable of ensuring the removal of electrostatic charge. This means, as a cylinder made of conductive material, is disposed at the tip of the coupling and the body, so as to be in contact with a portion of said body and of the mouthpiece.

p0008The problem to be solved by the invention is to allow, at a vacuum pipette tip, the static electricity without creating damage to the circuits being formed on the wafer.

p0009More particularly the invention refers to a connection for vacuum pipette, comprising in known manner a connecting means for coupling to the pipette body and a gripping zone with an opening, for the application of vacuum at the pellet.

p0010To solve such a problem, the tip comprises a sleeve with two ends, the first end being coupled to the connecting means, while the second end is coupled to the gripping area, said sleeve of insulating material, electrically connecting the gripping zone connecting means via an electrical resistor of high ohmic value the sleeve includes a duct means interior in communication with the opening, which is coupled to the connecting means, for communicating the vacuum in said zone gripping.

p0011Given these provisions, it appears, the resistance is coupled to the nozzle, the large individual electrostatic discharge that occurs when the tips are used with charged pellets is reduced to a series of small shocks. Each of these discharges is not large enough to deteriorate the pellet.

p0012Advantageously, the resistance to a value within a range from 10 to 50 MΩ.

p0013To resolve the problem of carrying electrical current, the gripping zone and the connecting means consist of a thermoplastic material into which are embedded conductive fibers for transporting electric current.

p0014More particularly, the problem of the transmission and dissipation of the electric current is achieved in that the resistive sleeve consists of a thermoplastic material, within which is embedded the electric resistance, said resistive sleeve being non-conductive of electricity, the electrical resistor being electrically connected to the grip region and the connection means for the transport and the dissipation of an electric current.

p0015The thermoplastic material is selected from poly-ether ether ketone materials and poly ether ketone, the conductive fibers are selected from carbon fibers or silicon carbide fibers.

p0016The percentage of carbon fibers is of the order of 8%.

p0017To resolve the problem to minimize chemical contamination at the nozzle, the gripping area is covered with a ceramic coating. This ceramic coating is produced with a controlled conductivity and can contribute to adjustment of the impedance of the tip, to allow the electrostatic discharge of the charged pellets.

p0018Advantageously, the coating consists of silicon carbide, silicon dioxide or silicon.

p0019The invention is described hereinafter in more detail using the appended drawings, in which:

p0020Figure 1 is a perspective view from above of a pipette tip according to the invention.

p00212a and 2b are sectional views of the resistive sleeve.

p0022Figure 3 is a graph showing the change of the voltage with respect to time when the tip is used for taking a semiconductor wafer.

p0023Figure 1 shows a mouthpiece for the vacuum pipette type described in US Patent 4,981,315 supra. The tip may be made of poly-ether ether ketone material (PEEK), poly ether ketone (PEK) or other thermoplastic materials having similar characteristics and wherein were blended conductive fibers are carbon or carbide component silicon.

p0024In a preferred embodiment, the end piece consists of PEK mixed with carbon fibers. The proportion of carbon fibers relative to the PEK may be varied in a range extending from 5 to 12%. In a preferred manner, the proportion of the fibers is 8%.

p0025The nozzle (1) is coated completely with a ceramic coating to avoid particulate and ionic contamination from PEK and carbon fibers. Since the PEK and the fibers contain elements such as Na, K, Mg and Pb, the contamination from the nozzle, can be an important source of chemical contamination of the pellets at the time of handling.

p0026This coating consists of SiC, SiO2 and Si. The coating is deposited, either using the cold precipitation chemical vapor, plasma, or by using a reactive sputter or spit. In a preferred embodiment, a technique is used for reactive sputtering the coating of the tip. Is applied to the tip, a layer of a few micrometers, the thickness is preferably about 10 micrometers.

p0027In other implementations, the coating can have a conductivity capable of replacing the discontinuous impedance coupled to the tip and described below. Similarly, the coating may be made less conductive than the base material used to manufacture the tip. When using this type of coating, static electricity discharges shall debit through the coating and the base material of the mouthpiece. In addition, the friction coating may high, which reduces the possibility of abrasion of the pellet.

p0028The nozzle (1) further comprises a sleeve (3) and a connecting portion (2) to the gripping zone. 2a and 2b show how to incorporate a resistor (4) of great value at the tip (1). Advantageously, the resistor (4) to a value within a range from 10 to 50 MΩ.

p0029The sleeve (3) of cylindrical shape has two axial passages (a) and (b). The resistor (4) is arranged in the portion (b) and welded fixedly at its ends by means of small cylinders (6) consisting of PEEK with carbon fiber embedded in PEEK. This produces an electrical connection from the cylinders (6) and through the resistor (4). In addition, the metallic resistance wire (4) being closed in a positive manner, it can not contaminate the pellets and will not be affected by chemical detergents, solvents, etc ...

p0030The portion (a) permits the vacuum supply in the sleeve (3). The end of the tip (1) is fitted to one end of the sleeve (3), whose other end receives the connecting portion (2) of the grip area of ​​the pipette. Is established in (5), the electrical contact resistance with the small cylinders (6).

p0031PEEK sleeve (3) is an insulator. The result is that all the current debiting from the tip is in charge resistance (3) before switching on the connection part (2). When the tip is inserré in a vacuum tool, a coiled wire passing through the vacuum source said tool, connects the tip to a ground potential.

p0032As shown in FIG 3, when a nozzle incorporating the special material and special resistance according to the invention is used for gripping a disc loaded, the individual static discharge is a discontinuous series of small shocks, each being too little important for damaging the wafer.

p0033The present invention has been described with a preferred embodiment, but may have many variants, in particular at the value of the resistance and the nature of the coatings.