Method for forming magnetoresistive random access memory with magnetic tunnelling junction

First of all, a semiconductor substrate is provided. On the semiconductor substrate, a word line is formed and covered with a insulating layer. Next, forming a connected device in the insulating layer to connect with the first conducting line layer. In order, a pinned layer is then deposited along the first insulating layer and the connected device. On top of the pinned layer, an insulating tunnel barrier layer is formed. Then a free layer is deposited on the insulating tunnel barrier layer. There is a single large MTJ that covers the entire surface of the first insulating layer on the conducting line layer. This large MTJ is then patterned into a small MTJ by etching process and through the free layer to the surface of the insulating tunnel barrier layer. Subsequently, the small MTJ are then covered with a second insulating layer. Afterward, opening a contact hole in the second insulating layer to the top of the small MTJ. Finally, a second conducting line layer is then formed on top of the structure to contact the free layer in the small MTJ.

DESCRIPTION OF THE PREFERRED EMBODIMENT One preferred embodiment of the present invention will now be described in greater detail. Nevertheless, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims. As illustrated in FIG. 2 A, in an embodiment of the present invention, first of all, a semiconductor substrate 200 is provided. On the semiconductor substrate 200 , a first conducting line layer 210 , such as a word line, is formed and covered with a first insulating layer 220 . Next, forming a contact hole in the first insulating layer 220 to expose a partial surface of the first conducting line layer 210 . Afterward, forming a connected device 230 , such as a diode, in the contact hole to connect with the first conducting line layer 210 . Then the series of layers which make up the magnetic tunnel junction 240 A are deposited by magnetron sputter deposition uniformly on the surface which is held near ambient temperature. As illustrated in FIG. 2 B, in this embodiment, in order, a pinned layer 250 having multi-layers that are magnetizable material, such as Ni, Co and Fe alloy, is deposited along the first insulating layer 220 and the connected device 230 , wherein the direction of polarization of the pinned layer 250 is fixed. On top of the pinned layer 250 , an insulating tunnel barrier layer 260 is formed, wherein the method for forming the insulating tunnel barrier layer 260 utilizes a material of Al that is deposited and oxidized to form a aluminum oxide layer, such as Al 2 O 3 . Then a free layer 270 having multi-layers that are magnetizable material, such as Ni, Co and Fe alloy, is deposited on the insulating tunnel barrier layer 260 , wherein the direction of polarization of the free layer 270 is variable. There is a single large MTJ 240 A that covers the entire surface of the first insulating layer 220 on the first conducting line layer 210 . As illustrated in FIG. 2 C, in this embodiment, a photoresist layer 275 is formed and defined on the free layer 270 . The large MTJ 230 is then patterned into a small MTJ 240 B by way of using the the etching process and the photoresist layer 275 as an etching mask and through the free layer 270 to the surface of the insulating tunnel barrier layer 260 . Next, the photoresist layer 275 is removed. Subsequently, the small MTJ 240 B are then covered with a second insulating layer 280 . Afterward, a contact hole is then formed in the second insulating layer 280 to the top of the small MTJ 240 B. Finally, a second conducting line layer 290 , such as bit line, is then formed on top of the structure to contact the free layer 260 in the small MTJ 240 B, as shown in FIG. 2D . In this embodiment of the present invention, as discussed above, this invention can form a novel structure of the magnetic tunnel junction to substitute for conventional structure, so as to obtain a good magnetiresistance performance. Hence, the present invention is appropriate for deep sub-micron technology to provide the semiconductor devices. Furthermore, the present invention can form pinned layer having a larger area in the magnetic tunnel junction, so as to avoid the stray field of the pinned layer edge and prevent the edge defect of the sandwich structure during the etching process, as shown in FIG. 2E . Moreover, this invention can get an etching stop layer by forming a larger area pinned layer to decrease the complex of process. On the other hand, the magnetic field of the present cell is easy to be determined due to the stronger signal from the resistance. Accordingly, this invention can provide a magnetoresistive random access memory which has a magnetiresistance performance is better than the conventional one, so as to increase yield and quality of the process and, hence, decrease cost. In other words, the present invention can correspond to economic effect. Of course, it is possible to apply the present invention to the process for forming the magnetic tunnel junction, and also it is possible to the present invention to any one magnetoresistive random access memory devices in the semiconductor devices. Also, this invention can be applied to use the large pinned layer concerning the process of the magnetoresistive random access memory used for avoiding the edge defect and making the stronger signal from the resistance have not been developed at present. Method of the present invention is the best magnetoresistive random access memory compatible process for deep sub-micro process. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein. Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.