A test of a circuit formed on a semiconductor substrate or a liquid crystal display is generally performed using a test apparatus with an electrode portion (which is called, for example, a probe card) having a number of contacts (or contact needles) called contact probes being arranged correspondingly to a circuit pattern to be tested. Miniaturization of contact probes has been required, and as disclosed in Japanese Patent Laying-Open No. 2000-162241, for example, it is possible to manufacture a ultra-fine contact probe having a thickness of 0.1 mm or less by a combined method of lithography and electroforming. Conventionally, Japanese Patent Application No. 2000-164407 has proposed a structure of each contact probe, as shown in FIG. 35. In this contact probe, a tip end portion 501 is supported by a spring portion 502. This is formed by lithography and electroforming using a mask having a pattern as shown in FIG. 36.
Similarly, a method of manufacturing a probe using lithography and electroforming is also disclosed in Japanese Patent Laying-Open No. 11-337575 and the like.
In many cases, the surface of a circuit under test is generally provided with an insulating film such as an oxide film. In a test, it is necessary to break the insulating film such as a natural oxide film formed on the surface of the circuit under test, in order to assure electrical contact. A contact pressure is desirably increased to some extent in order to break the insulating film. For this purpose, at the tip end of the contact probe, as shown in FIG. 37, for example, a tip end portion 501a may be sharpened.
In a method of forming a conductive contact probe by lithography and electroforming, however, as a three-dimensional shape is formed based on a two-dimensional pattern, even using the pattern as shown in FIG. 37, tip end portion 501a that is a projection of the tip end of the resultant contact probe is actually shaped like a triangular prism as shown in FIG. 38, providing linear contact. It has also been proposed to manufacture a contact probe as shown in FIG. 40 using a mask as shown in FIG. 39. In this case, a tip end portion 501b is also shaped like triangular prism, providing linear contact. In other words, point contact cannot be achieved and therefore the contact pressure cannot be increased above a prescribed level.
Furthermore, while the contact pressure has to be increased to some extent in order to break through the insulating film, the finer the contact probe becomes, the weaker the contact probe itself becomes, making it difficult to increase a load. Moreover, application of a high pressure is also unfavorable for the substrate under test.
As an approach to effectively break the insulating film, for example, Japanese Patent Laying Open No. 2000-292436 has proposed a mechanism for rotating a contact probe itself. Such a method, however, requires a combination of multiple components, which would complicates the structure, thereby making miniaturization difficult and also increasing the cost, inevitably.
The tip end of the contact probe is advantageously sharp like a needle. In the method of manufacturing a contact probe by lithography and electroforming, a three-dimensional shape is manufactured using a die fabricated based on a two-dimensional mask. Therefore, even if the contact probe is produced using the pattern with an open window having the shape as shown in FIG. 41A, for example, a projection portion 91 at the tip end is shaped like a triangular prism, as perspectively shown in FIG. 41B. In other words, linear contact is provided on the test circuit, which increases the contact area. Therefore, the probe has to be brought into contact under an excessively high contact pressure to break through the insulating film, and additional shaping process is required to obtain a needle-like tip end.
USPTO Backgrounds
USPTO Backgrounds