KR20030044596A - A wordline with a magnetic field keeper for magnetic memory devices and sensors and method of manufacture therefor - Google Patents

Abstract

PURPOSE: A method for manufacturing a wordline having a keeper layer capable of applying to a magnetic memory and a sensor is provided to supply a magnetic layer mainly constituted of Co serving as a magnetic field keeper and having an excellent characteristics as a barrier layer. CONSTITUTION: A method for manufacturing a wordline having a keeper layer capable of applying to a magnetic memory and a sensor includes the steps of: forming an insulating layer(102) on a semiconductor substrate(100), forming a trench in the insulating layer(102) at a predetermined depth by using photolithography method, coating a magnetic keeper layer(106) on the inner and exterior surface of the trench by using a physical vapor deposition method, depositing seed layer made of copper(Cu) on the entire surface of the magnetic keeper layer(106), depositing a conducting layer(110) made of Cu at a predetermined thickness so as to cover the trench(104) formed on the top of the seed layer by using an electroplating method and planarizing the conducting layer(110) by using a chemical mechanical polishing(CMP) method until the top surface of the insulating layer is exposed.

Description

A wordline with a magnetic field keeper for magnetic memory devices and sensors and method of manufacture therefor}

The present invention relates to a word line manufacturing method having a keeper layer applicable to a magnetic memory and a sensor. More particularly, the present invention relates to a method of manufacturing a word line (or bit line) having a keeper layer for generating a magnetic field necessary for inverting magnetization in a magnetic memory and a sensor.

Magnetic memories and sensors consist of a multilayered film whose core component is a thin film of magnetic material. The operation of the magnetic memory and the sensor requires the magnetization reversal of some or all of the magnetic multilayer films, and the magnetic field required for the magnetization reversal is obtained by passing a current through the word line and the bit line. Magnetic memory devices known as magnetic random access memory (MRAM) are broadly referred to as memory devices using magnetic materials, which have a long history from the ferrite core of the 1970s to magnetic bubble technology.

However, the negotiated magnetic memory device uses a magnetoresistance (MR) phenomenon. As an example, the recent giant magnetoresistance (GMR) and turnneling magnetoresistance (GMR) have been used in the initial anisotropic MR (AMR). Magnetic memory devices using TMR (tunneling-type magnetoresistance) phenomenon. In such magnetic memory devices, digital information is determined by the direction of magnetization in the magnetic multilayer. The magnetic multilayer film is usually composed of three core layers, and the two magnetic films have a structure surrounding the conductive film (GMR development) or the insulating film (TMR development). The process of writing and reading digital information involves the magnetization reversal of one or two magnetic films.

As an example, in the case of a magnetic memory device using a TMR phenomenon, the magnetization of one magnetic film is always fixed during operation of the device, and only the other magnetic film is magnetized inverted. The fixed magnetic film is called a fixed layer, and the magnetic film whose magnetization is reversed is called a free layer. Consider the case where the magnetization of the pinned layer is fixed in the (+) X direction, and the free layer also has uniaxial magnetic anisotropy in the X-axis direction, so that the magnetization is directed only in the (+) X or (-) X direction.

In the magnetoresistive thin film, the resistance depends on the direction of magnetization in the two magnetic layers. Specifically, when the magnetization directions are parallel, the resistance is low, and when the magnetization directions are antiparallel, the resistance is high. When the magnetization of the free layer is in the (+) X direction, the magnetization of the two magnetic layers is in the same direction, and thus the resistance is low. On the contrary, the magnetization of the free layer is in the high resistance state when the magnetization of the free layer is in the (-) X direction. The magnetization direction of the free layer is capable of storing digital information because the magnetization state of the free layer is directed only in two directions of (+) X or (-) X directions.

A typical magnetic memory element is composed of a large number of word lines and bit lines, and the two lines cross each other perpendicularly. Word lines and bit lines are usually made of a low resistivity copper (Cu) or aluminum (Al) -copper (Cu) alloy. A magnetic multilayer film for storing digital information is located between word lines and bit lines that are orthogonal to each other. In the magnetic multilayer film, inversion of magnetization is achieved by a magnetic field generated from current flowing through the word lines and bit lines.

This is accomplished in the magnetic memory device consisting of two magnetic layers, a free layer and a fixed layer, by magnetizing reversal of the free layer by simultaneously flowing a current through the word line and the bit line. At this time, the magnitude of the current flowing through the word line and the bit line depends on the magnitude of the magnetic field required for magnetization inversion of the free layer.

That is, if the magnetic field required for magnetization reversal is large, a large amount of current must be flowed into the word line and the bit line. If the magnetization reversal magnetic field is small, the magnetization is inverted even if a small current is flowed. If too much current flows through the word line and bit line, it may not only consume a lot of power, but may also cause problems with the performance of the device due to heat generation. Will be higher.

Therefore, it is very important to reduce the magnitude of the current flowing through the word line and the bit line to less than the proper size when the memory device operates.

On the other hand, one of the most commercially important factors in memory devices including magnetic memory is density. In order to achieve high density in magnetic memory devices, it is necessary to reduce the size of the magnetic multilayer film that stores information. At the density required for magnetic memory devices to compete with other existing memory technologies, the size of the magnetic film is expected to be in the submicron range. Because of the large magnetostatic interactions in this size range of the magnetic film, a very large magnetic field is required to invert the magnetization, thus driving a large amount of current to the word and bit lines to operate the device. .

To solve this problem, Hurst et al. Proposed a method of enclosing a part of a word line with a soft magnetic film in US Pat. No. 5,956,267. The soft magnetic film surrounding the word line is called a magnetic field keeper layer. The use of the keeper layer has shown that the magnetic field applied to the magnetic multilayer film from the word line / bit line increases. This reduces the magnitude of the current applied to the word line and the bit line, thus reducing the problems associated with high current density.

In order to achieve higher density of the magnetic memory device, it is required to reduce the size of the magnetic multilayer film as well as the width and thickness of the word line and the bit line. This reduces the cross-sectional area of the conductor through which current flows, and increases the current density flowing through the conductor even though a constant current flows.

In summary, as the size of the magnetic film decreases in the high-density magnetic memory device, the size of the word line and the bit line also decreases even though the magnetic field required for the magnetization reversal greatly increases, making it difficult to flow a large current to the word line and the bit line. It is difficult to obtain the required magnetic field, which is one of the biggest obstacles in achieving high density of magnetic memory.

In addition, as the density of the magnetic memory device is increased, the distance between neighboring cells decreases, thereby increasing the possibility of cross-talk between cells. The keeper layer also reduces the interference between cells.

The word line and the bit line are fabricated through a process of fabricating a trench or cavity by a micromachining technique in a thick insulating film composed mainly of a silicon oxide film and then electroplating copper. In the prior art, the magnetic field keeper layer was enclosed in a part of the conductor to increase the magnetic field required for magnetization reversal. In this case, NiFe, NiFeCo and CoFe materials were used as the magnetic field keeper layer.

If the magnetic field keeper layer of such material is placed directly between the insulating film and the word line / bit line, the keeper layer material may diffuse into the insulating film or the reaction between the keeper layer and copper may cause a big problem in the performance and reliability of the device. There is this. In order to prevent this problem, in the related art, a barrier layer is inserted before and after the magnetic field keeper layer.

That is, the barrier layer is located between the insulating film and the keeper layer and between the keeper layer and the word line / bit line. Ta, TiW, TiN or TaN or the like has been used as the barrier layer. Insertion of such barrier layers not only requires an additional process, but also increases current density because it reduces the cross-sectional area of copper through which current flows.

Accordingly, the present invention has been made to solve this problem, and an object of the present invention is to provide a magnetic layer mainly composed of Co as a magnetic field keeper layer. At this time, since the magnetic layer composed of Co as a main component provided in the present invention has excellent soft magnetic properties and serves as a magnetic field keeper and also has excellent characteristics as a barrier layer, no additional barrier layer is required to be inserted.

Further, another object provided by the present invention is that the size of the magnetic field required for magnetization reversal of the magnetic multilayer film storing information is very sensitive to the shape of the word line and the bit line having the keeper layer, and thus the It is to provide a technique for optimizing the shape.

More specifically, the size of the magnetic field applied to the magnetic multilayer film varies depending on the specific shape of the word line and the bit line and the spacing between the word line / bit line and the magnetic multilayer film. We want to achieve optimization. However, it is well known that the principles of the present invention can be equally applied to word lines and bit lines having similar magnetic field keeper layers.

As a technical idea for achieving the above object of the present invention

Forming an insulating layer on the semiconductor substrate; Forming a trench having a predetermined depth in the insulating layer using a photoetch process; Coating a magnetic field keeper layer on the inner and outer surfaces of the trench by using physical vapor deposition; Depositing a seed layer made of copper (Cu) on an entire surface of the keeper layer; Depositing a copper (Cu) conductive layer by electroplating to a thickness sufficient to cover the trench on the seed layer; It provides a word line manufacturing method having a keeper layer applicable to a magnetic memory and a sensor comprising the step of planarizing using a CMP process until the upper surface of the insulating layer is exposed.

1A to 1F are cross-sectional views illustrating a process of manufacturing a word line having a keeper layer according to the present invention.

2 is a graph comparing the magnitude of a magnetic field generated from a word line with or without a keeper layer.

3 and 4 are graphs showing the effect of the aspect ratio on the magnitude of the magnetic field generated from the word line in the word line in which the keeper layer is present.

<Description of Symbols for Major Parts of Drawings>

100 semiconductor substrate 102 insulating layer

104: trench 106: keeper layer

108: seed layer 110: conductive layer

Hereinafter, with reference to the accompanying drawings, the configuration and operation of the embodiment of the present invention will be described in detail.

Prior to the detailed description of the present invention, the magnetization reversal of the magnetic multilayer film that normally stores information in the magnetic memory device is achieved by simultaneously applying current to the word line and the bit line, but in the present invention, only the word line is described for convenience of description. do. For reference, the shape of the word line and the bit line in the present invention is represented by an aspect ratio (thickness / width ratio).

1A to 1F are cross-sectional views showing the manufacturing process of a word line having a keeper layer according to the present invention.

An insulating layer 102 made of a silicon oxide film is formed on the semiconductor substrate 100, that is, a silicon substrate. (See FIG. 1A). A trench having a predetermined depth may be formed on the insulating layer 102 using a conventional photolithography process. A trench (or cavity) 104 is formed (see FIG. 1B).

Then, the magnetic field keeper layer 106 is coated on the inner and outer surfaces of the trench 104 using a physical vapor deposition method such as sputtering method (see FIG. 1C), and then copper (Cu) on the upper front surface thereof. The seed layer 108 of the material is thinly formed.

At this time, the magnetic field keeper layer 106 mainly uses an alloy composed of Co. Specifically, Co-P alloy, Co-B alloy, Co-Si alloy, Co-Nb alloy, Co-Ta alloy, Co-Mo alloy, Co-Cu alloy, Co-W alloy, etc. are mentioned. These alloys also have a high permeability, as well as an insulating role that prevents copper from diffusing into the insulating layer 102 (see FIG. 1D).

Next, copper (Cu) is coated on the front surface of the seed layer 108 to the conductive layer 110 by electroplating. At this time, the conductive layer 110 is deposited to a thickness sufficient to cover the trench 104 (see FIG. 1E).

Subsequently, the final upper layer is planarized while removing unnecessary thin films using a chemical-mechanical planarization (CMP) process until the upper surface of the insulating layer 102 is exposed (see FIG. 1F).

Here, in FIG. 1F, the horizontal axis is represented by y as the coordinate axis and the vertical axis is represented by z. The x-axis is the direction perpendicular to the paper plane and is the same as the direction in which the current flows.

1F shows a process diagram for the case where the aspect ratio of the word line is similar to 1, the process for producing word lines having other aspect ratios is similar to the present invention. Various types of word line aspect ratios and actual cross-sectional areas of word lines considered in the present invention are as follows.

For aspect ratio 16 (4.0 μm (thickness) × 0.25 μm (width)), for 9 (3.0 μm (thickness) × 0.333 μm (width)), for 4 (2.0 μm (thickness) × 0.5 μm (width) ))to be.

For an aspect ratio of 1.56 (1.25 μm (thickness) × 0.8 μm (width)), for 1.0 (1.0 μm (thickness) × 1.0 μm (width)), for 0.44 (0.67 μm (thickness) × 1.5 μm (width) )), Which is 0.25 (0.5 μm (thickness) x 2.0 μm (width)).

Figure 2 is a graph comparing the magnitude of the magnetic field generated from the word line without the keeper layer and the magnetic field generated from the word line having a keeper layer consisting of Co according to the present invention in order to obtain the effect of the keeper layer.

At this time, the aspect ratios of the two word lines are each 1.0, and the thickness of the keeper layer is 0.03 µm. The magnitude of the current applied to the word line is 10 mA and the cross section is 1 um2. 2 represents the length in the y direction (horizontal direction), where y = 0 represents the center of the word line. The vertical axis represents the magnetic field Hy of the y-direction component at a distance 0.13 μm away from the word line in the z-direction (vertical direction) (that is, z = 0.13 μm). z = 0.13 μm corresponds to the distance between the word line and the free layer in a conventional magnetic memory.

Two dashed lines shown vertically in FIG. 2 indicate the width of the word line. As shown in Fig. 2, the magnetic field generated from the word line due to the presence of the keeper layer is greatly increased. In addition, the generated magnetic field exists only around the word line and decreases very rapidly as the distance from the word line increases. From the results of FIG. 2, it can be seen that the keeper layer is very effective in reducing the current density of the word line and reducing the interference between cells generated in the high density magnetic memory.

3 is a graph showing how an aspect ratio affects the magnitude of a magnetic field generated from a word line in a word line in which a keeper layer exists. Referring to Figure 3, the magnitude of the current applied to the word line is 10 mA, the cross-sectional area is 1 um2. The horizontal axis is the distance away from the word line in the z direction at the center of the word line (y = 0) and the vertical axis is the y-direction component (Hy) of the magnetic field.

Although the cross-sectional area of the word line is the same as shown in FIG. 3, Hy is very sensitive to the aspect ratio. In particular, when the distance from the word line is small, the change of Hy is very large depending on the aspect ratio. When applied to magnetic memory, the size of Hy shows the following two characteristics at the corresponding distance (typically in the range of z = 0.1 to 0.2 um).

The first is that the magnitude of Hy varies very sensitive to the aspect ratio, and the second is that the magnetic field is at its maximum in any aspect ratio range. This feature requires the optimization of the word line shape in the design of magnetic memory devices. More specifically, when the distance from the word line is small, Hy increases as the aspect ratio decreases, showing a maximum at an aspect ratio of 4.0, and Hy decreases again when the aspect ratio further decreases.

Another additional feature is that Hy rapidly changes depending on the distance from the word line when the aspect ratio is large, but Hy decreases gradually when the aspect ratio is small. As a result, when the distance from the word line is large, the change of Hy according to the aspect ratio is very small compared to the case where the distance from the word line is small.

FIG. 4 is a graph similar to FIG. 2 showing the results for a magnetic field generated from a word line with a keeper layer for different aspect ratios. That is, the horizontal axis represents the length in the y direction, and y = 0 represents the center of the word line. The vertical axis represents the magnetic field (Hy) of the y-direction component at a distance 0.13 μm away from the word line in the z direction (that is, z = 0.13 μm). The magnitude of the current applied to the word line is 10 mA and the cross section is 1 um2. In the case of the center of the word line (y = 0) As already mentioned in FIG. 3, when the aspect ratio is 4.0, Hy is very rapidly changed as Hy is out of the center of the word line. This change is more pronounced as the aspect ratio increases. However, the change in Hy is very small at an aspect ratio of 1.56, and the change in Hy decreases as the aspect ratio decreases.

As an example, at an aspect ratio of 1.0 or less, there is little change in Hy even if it deviates to a distance of 0.3 m from the center of the word line. Considering the magnitude of Hy and the change of Hy due to deviation from the center of the word line, the optimum aspect ratio is considered to be in the range of 0.44 to 4.0, and more preferably in the range of 1.0 to 1.56.

Although the present invention has been described above with reference to the magnetic memory, the present invention can be similarly applied to the application of a magnetic sensor, in particular a micro magnetic sensor. The magnetic field in a micromagnetic sensor is obtained by passing a current through a conductor such as copper similarly to a magnetic memory, and in this application, it is very important to obtain a large magnetic field at low current (current density) as in the magnetic memory.

As described above, the word line manufacturing method having the keeper layer applicable to the magnetic memory and the sensor according to the present invention has the following effects.

First, the present invention provides a magnetic layer mainly composed of Co, which is relatively excellent in soft magnetic properties and serves as a magnetic field keeper and also has excellent characteristics as a barrier layer.

In a word line / bit line having a conventional magnetic field keeper layer, a barrier layer is required before and after the keeper layer. However, when the main component provided by the present invention uses a film composed of Co, the barrier layer is not required. This reduces the process required for the magnetic memory device and also minimizes the reduction in cross-sectional area of the copper through which current flows. This lowers the current density through copper for a constant amount of current, thereby reducing the problems associated with high current density.

Second, the present invention provides an optimal shape for the word line / bit line so that the magnetic field necessary for magnetization reversal is maximized with respect to the word line / bit line having the magnetic field keeper layer.

In the device corresponding to the high density magnetic memory, the size of the magnetic field required for magnetization reversal is very sensitive to the shape of the word line / bit line, and the maximum magnetic field is obtained in the specific shape. In view of the magnetic field required for magnetization reversal, the optimum shape of the word line / bit line is when the aspect ratio is between 0.44 and 4.0.

Claims (3)

Forming an insulating layer on the semiconductor substrate; Forming a trench having a predetermined depth in the insulating layer using a photoetch process; Coating a magnetic field keeper layer on the inner and outer surfaces of the trench by using physical vapor deposition; Depositing a seed layer made of copper (Cu) on an entire surface of the keeper layer; Depositing a copper (Cu) conductive layer by electroplating to a thickness sufficient to cover the trench on the seed layer; And planarizing using a CMP process until the upper surface of the insulating layer is exposed, wherein the word line manufacturing method has a keeper layer applicable to a magnetic memory and a sensor. The method according to claim 1, wherein the keeper layer is optionally selected from Co-P alloy, Co-B alloy, Co-Si alloy, Co-Nb alloy, Co-Ta alloy, Co-Mo alloy, Co-Cu alloy, Co-W alloy A word line manufacturing method having a keeper layer applicable to a magnetic memory and a sensor, characterized in that it consists of any one layer selected. The word line manufacturing method according to claim 1, wherein an optimum shape aspect ratio of the word line is between 0.44 and 4.0.