TW201622070A - Active area contact of dynamic random access memory and method of manufacturing the same - Google Patents

Abstract

A method of manufacturing active area contacts of dynamic random access memory (DRAM) includes forming a conductive layer on a substrate to cover contact areas and bit lines. The DRAM includes the substrate, isolation structures in the substrate, active areas (AA) separated by the isolation structures, buried word lines through the AA, and the bit lines on the substrate, wherein each of AA contains the contact areas. After forming the conductive layer, the conductive layer is removed outside the contact areas to form a plurality of AA contacts. An insulating layer is then formed on the substrate to cover the AA contacts.

Description

Active area contact window of dynamic random access memory and manufacturing method thereof

The present invention relates to a dynamic random access memory (DRAM), and more particularly to an active area contact window (AA contact) of a dynamic random access memory and a method of fabricating the same.

With the impact of the expansion of large factories, the memory market environment is becoming more and more severe. Major manufacturers are actively pursuing process technology research and development and reducing process costs. Process miniaturization is the main cost reduction path. The shrinking of the chip size is not only challenging for the exposure machine technology and etching capability, but also because the word line spacing and the isolation structure of the memory array are shrinking, resulting in various adverse effects. For example, the contact resistance Rs part of the contact window, because the size of the wafer is reduced, the volume of the contact window is reduced, and the contact window resistance is greatly increased. Therefore, how to improve the contact window Rs is also a major problem.

The current contact window is a trench filling method formed after the etching, that is, the contact window opening is etched in the insulating layer or the dielectric layer by an etching process, and then the conductor material is filled.

The invention provides a method for manufacturing an active area contact window of a dynamic random access memory, which can improve the resistance of the contact window and enlarge the process window of the contact window.

A method for fabricating an active area contact window of a dynamic random access memory according to the present invention includes forming a conductive layer on a substrate to cover a contact window region and a bit line. The dynamic random access memory includes at least a substrate, an isolation structure in the substrate, an active area separated by the isolation structure, a buried word line passing through the active area, and a bit line on the substrate, wherein each active The area includes several contact window areas. Then, the conductive layer outside the contact window region is removed to form a plurality of active region contact windows, and an insulating layer is formed on the substrate to cover the active region contact window.

In an embodiment of the invention, the method for forming the active region contact window includes removing conductive layers outside the contact window region by dot lithography to form a cylindrical active region contact window.

In an embodiment of the invention, the method for forming the active region contact window comprises first planarizing the conductive layer until the top surface of the bit line is exposed, and then removing the conductive layer outside the contact window region by linear lithography.

In an embodiment of the invention, the step of removing the conductive layer outside the contact window region comprises leaving a plurality of conductive layer layers, and the method for forming the insulating layer comprises converting a portion of the conductive layer into an insulating layer by using a self-oxidation technique. material.

In an embodiment of the invention, the self-oxidation technique includes a spot vapor generation technique (ISSG), a wet oxidation process, or a low temperature plasma oxidation process (SPA oxide).

In an embodiment of the invention, the method for forming the insulating layer includes conformally forming a tantalum nitride layer and a ruthenium oxynitride layer covering the contact window of the active region, and forming a spin-on glass layer on the substrate by spin coating. (SOG).

In an embodiment of the invention, a method of forming the insulating layer includes filling a tantalum nitride layer between active contact openings on a substrate by atomic layer deposition (ALD).

In an embodiment of the invention, a spacer may be formed on the side of the bit line to form the conductive layer and the bit line before forming the conductive layer.

The present invention further provides an active area contact window of a dynamic random access memory capable of maintaining its low resistance value and having a large bottom area when the wafer size is increasingly reduced.

In another active random access memory of the present invention, the dynamic random access memory includes at least a substrate, an isolation structure in the substrate, an active region separated by the isolation structure, and a buried through the active region. The input word line and the bit line intersecting the buried word line on the substrate. Each active zone includes a plurality of contact window areas. The active area contact windows are respectively located on the contact window area, wherein each active area contact window is cylindrical; the side of the active area contact window between the two two-dimensional lines is a curved surface; and each active area The bottom surface area of the contact window is larger than the top surface area, and the bottom surface is the side directly contacting the contact window area.

In another embodiment of the invention, the material of the active area contact window comprises polysilicon.

In another embodiment of the invention, the surface of the active area contact window that is in contact with the bit line is a flat surface.

In another embodiment of the invention, the top surface of the active area contact window is higher than the top surface of the bit line.

In another embodiment of the invention, the top surface of the active area contact window is flush with the top surface of the bit line.

Based on the above, the present invention increases the contact area between the active area contact window and the active area by forming a contact window to form an insulating layer between the contact windows, thereby reducing the contact window resistance value Rs, and because the active area contact window It is formed first, so that the problem that the bit line and the contact window are short-circuited or the threshold voltage becomes low can be avoided. In addition, when the present invention forms the above insulating layer by self-oxidation technology, the step height difference between the memory region and the peripheral region can be avoided.

The above described features and advantages of the invention will be apparent from the following description.

100‧‧‧Substrate

100a‧‧‧Contact window area

102‧‧‧Isolation structure

104‧‧‧Blinded word line

106‧‧‧ bit line

106a, 124a, 304, 322, 400a, 602a, 604a‧‧‧ top

108‧‧‧Insulation structure

112‧‧‧ epitaxial or polycrystalline layer

114‧‧‧metal layer

116‧‧‧ nitride layer

118‧‧‧ spacer

120‧‧‧Barrier layer

122‧‧‧ Conductive layer

124, 300a, 300b, 300c, 300d, 400, 604‧‧ ‧ active area contact window

124b, 306, 324‧‧‧ bottom

126‧‧‧Lamination of tantalum nitride layer or tantalum nitride/aluminum oxide

128‧‧‧Spin-on glass layer

200‧‧‧active area

202‧‧‧Contact window area

302, 310, 316, 320‧‧‧ plane

308, 312, 314, 318, 602b, 604b‧‧‧ side

402‧‧‧ nitride layer

600‧‧‧ mask

602‧‧‧ Conductive layer

606‧‧‧Insulation materials

1A to 1D are schematic cross-sectional views showing a manufacturing process of an active area contact window of a dynamic random access memory according to a first embodiment of the present invention.

2 is a schematic diagram showing the layout of the dynamic random access memory of FIG. 1C.

3A-3D are perspective views of active area contact windows of several types of dynamic random access memories in accordance with a second embodiment of the present invention.

4A-4B are schematic cross-sectional views showing a manufacturing process of an active area contact window of a dynamic random access memory according to a third embodiment of the present invention.

FIG. 5 is a schematic diagram of the layout of the dynamic random access memory of FIG. 4A.

6A-6C are schematic cross-sectional views showing a manufacturing process of an active area contact window of a dynamic random access memory according to a fourth embodiment of the present invention.

The embodiments of the present invention are shown in the accompanying drawings. However, the invention may be practiced in many different forms and should not be construed as being limited to the embodiments described. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and the scope of the invention will be fully conveyed to those of ordinary skill in the art.

In the drawings, the dimensions and relative dimensions of the various layers and regions may be exaggerated for clarity.

1A to 1D are schematic cross-sectional views showing a manufacturing process of an active area contact window of a dynamic random access memory according to a first embodiment of the present invention.

1A, the dynamic random access memory of the present embodiment includes at least a substrate 100, an isolation structure 102 in the substrate 100, and an active region separated by the isolation structure 102 (ie, a substrate 100 position between the isolation structures 102). The buried word line 104 passing through the active area and the bit line 106 on the substrate 100. The buried word line 104 and the bit line 106 may have an insulating structure 108 separating the two. The bit line 106 is composed of, for example, an epitaxial layer or a polysilicon layer 112, a metal layer 114, and a tantalum nitride layer 116, but the present invention is not limited thereto. Additionally, spacers 118 may be formed on the sides of the bit lines 106 to protect the bit lines 106 from subsequent processing. Buried word line Between 104 and substrate 100 there is typically a barrier layer 120.

In an embodiment, the material of the isolation structure 102 is, for example, hafnium oxide, tantalum nitride, or other suitable material. In one embodiment, the material of the buried word line 104 is, for example, tungsten, aluminum, copper, or other suitable material. In an embodiment, the insulating structure 108 is, for example, tantalum oxide, tantalum nitride or other suitable material. In one embodiment, the material of the metal layer 114 is, for example, a stack of titanium, titanium nitride, tungsten or aluminum/copper, and other suitable materials. In an embodiment, the material of the spacers 118 is, for example, tantalum oxide, tantalum nitride or other suitable materials. In an embodiment, the barrier layer 120 is, for example, tantalum oxide or other suitable material.

Next, referring to FIG. 1B, a conductive layer 122 is formed on the substrate 100 to cover the contact window region 100a in each active region, and the conductive layer 122 has a thickness as large enough to cover the top surface 106a of the bit line. The material of the conductive layer 122 is, for example, doped with polysilicon, titanium, titanium nitride, tungsten or other suitable conductive material.

Then, referring to FIG. 1C, the conductive layer other than the contact window region 100a is removed (see 122 of FIG. 1B), and a plurality of active region contact windows 124 are formed, and please refer to FIG. 2 at the same time, wherein the section line segment corresponds to FIG. 1C. s position. In FIG. 2, bit line 106 intersects buried word line 104, and single active area 200 is divided by buried word line 104 into a plurality of contact window regions (see 100a of FIG. 1C). In the first embodiment, the method of forming the active region contact window 124 removes the conductive layer other than the contact window region 202, for example, by dot lithography etching to form a cylindrical active region contact window 124, a so-called dot shape. (dot) lithography etching is to form a dot photoresist layer by a lithography process, and the dot photoresist layer is used as an etching mask to perform an etching process of the conductive layer. Since the etching process is faster because the etching rate is closer to the central etching region and the etching rate of the sidewall etching region is slower, the etching cross-sectional area is gradually reduced from the top to the bottom, and thus the bottom surface of the cylindrical active region contact window 124 is formed. The area of 124b is larger than the area of the top surface 124a.

Thereafter, referring to FIG. 1D, an insulating layer is formed on the substrate 100, for example, a tantalum nitride layer or a tantalum nitride/niobium oxynitride stack 126 covering the active region contact window 124 is formed in a conformal manner, and then spin coating is performed. A spin coating glass layer (SOG) 128 is formed on the substrate 100 to cover the active area contact window 124. In this embodiment, the active region contact window 124 is formed first to form the insulating layer (the film layers 126 and 128), so that the upper and lower cylindrical active region contact windows 124 can be formed by the looser process window to make the active region. The contact area between the contact window 124 and the contact window region 100a is increased, thereby achieving the effect of lowering the contact window resistance value Rs. The so-called looser process window is because the formed cylindrical active contact window 124 is larger than the conventionally formed contact window, and the conventional rear formed contact window is filled with the conductor by etching the contact window opening ( That is, the trench filling method), so in order to avoid damage to the adjacent bit line 106, the size thereof is smaller than the cylindrical active contact window 124 of the present embodiment, and the position thereof must be precisely controlled, so for example, the tolerance of the contact window position is allowed. The amount of shift is also relatively small. Moreover, since the active area contact window 124 is not fabricated by the trench filling method, it is also possible to avoid a short circuit or a threshold voltage caused by the front side of the bit line (such as the spacer 118 of FIG. 1A) for forming a contact opening ( Vth) low problem.

3A through 3D are perspective views showing the structure of active area contact windows 300a to 300d of several kinds of dynamic random access memories according to a second embodiment of the present invention.

In FIG. 3A, the position of the active area contact window 30oa in the position of the dynamic random access memory can be referred to the contact window area 202 between the bit lines with reference to the layout of FIG. 2, and the top surface 304 of the active area contact window 300a is high. On the top surface of the bit line (106a in Figure 1C), there is also a portion of the active area contact window 300a above the surface 302 (e.g., plane) that is in contact with the bit line. Figure 3A shows a single active area contact window 300a that is slightly cylindrical and has a curved side 308 between the bit lines. Moreover, the area of the bottom surface 306 of the active area contact window 300a is greater than the area of the top surface 304, and the bottom surface 306 herein refers to the side that is in direct contact with the contact window area.

In FIG. 3B, the active area contact window 300b is planar with the surface 310 in contact with the bit line, the side 312 between the bit lines is curved, and the top surface of the active area contact window 300b is higher than the bit line, but The top and bottom surfaces of the active area contact window 300b in this figure are the same area.

In FIG. 3C, the top surface of the active region contact window 300c is flush with the top surface of the bit line, so the side surface 314 between the bit lines is a curved surface, and the surface 316 in contact with the bit line is a flat surface.

In FIG. 3D, since the top surface of the active region contact window 300d is flush with the top surface of the bit line, as in FIG. 3C, the side surface 318 between the bit lines is a curved surface and a surface in contact with the bit line. 320 is a plane with the difference that its bottom surface 324 is larger than the top surface 322.

3A to 3D are merely illustrative of several implementable examples of the active area contact window of the present invention, but are not limited thereto.

4A-4B are cross-sectional views showing a manufacturing process of an active area contact window of a dynamic random access memory according to a third embodiment of the present invention, wherein The same reference numerals are used to denote the same or similar components as the first embodiment.

In this embodiment, the step of forming the conductive layer may refer to FIG. 1B of the first embodiment. Referring to FIG. 4A, a plurality of active region contact windows 400 are formed by, for example, planarizing the conductive layer until the top surface 400a thereof The top surface 106a of the bit line is flush, and please refer to FIG. 5 simultaneously to remove a portion of the conductive layer by line lithography. The section line in FIG. 5 corresponds to the position of FIG. 4A, so the active area contact window 400 is substantially Between the bit lines 106 and in contact with the active area 200. The above-mentioned line lithography etching is to form a line type photoresist layer by a lithography process, and the line type photoresist layer is used as an etching mask to perform an etching process of the conductive layer.

Thereafter, referring to FIG. 4B, an insulating layer is formed on the substrate 100, and a tantalum nitride layer 402 is filled between the active region contact windows 400 on the substrate 100, for example, by atomic layer deposition (ALD). In this embodiment, the active region contact window 400 is formed first to form the tantalum nitride layer 402. Therefore, the contact area between the active region contact window 400 and the substrate 100 can be increased by a relatively loose process window, thereby reducing the contact window resistance. The effect of the value Rs. The so-called looser process window is because the traditional post-forming contact window has to be filled into the conductor by etching the contact window opening (ie, the trench filling method), so in order to avoid damage to the bit line 106 next to it, precise control must be performed. Its position, so the allowable offset of such contact window position is smaller than the active contact window 400 formed, so that the conventional post-formed contact window process window is obviously smaller than the active area contact window 40 of the present embodiment.

6A-6C are cross-sectional views showing a manufacturing process of an active area contact window of a dynamic random access memory according to a fourth embodiment of the present invention, wherein The same reference numerals are used to denote the same or similar components as the first embodiment.

In this embodiment, the step of forming the conductive layer may be followed by the planarization process of the conductive layer 122, such as chemical mechanical polishing (CMP), after referring to FIG. 1B of the first embodiment, and then referring to FIG. 6A, the conductive layer. A suitable mask on the 122 corresponding to the contact window region 100a forms a mask 600 of a material such as photoresist, tantalum nitride or other suitable material.

Next, referring to FIG. 6B, the mask 600 is used as an etch mask to remove the exposed conductive layer leaving the conductive layer 602. The top surface 602a of the conductive layer 602 can be higher than the top surface 106a of the bit line 106.

Then, referring to FIG. 6C, a portion of the conductive layer is converted into an insulating material 606 by self-oxidation, wherein the self-oxidation technique such as on-site vapor generation (ISSG), wet oxidation or low temperature plasma Oxidation method (SPA oxide). Since the present embodiment forms the insulating layer by self-oxidation technique, the conductive layer 602 of FIG. 6B becomes the active region contact window 604, and the top surface 602a of FIG. 6B is lowered to the top surface 604a of FIG. 6C, the side surface 602b. It will also contract to the side 604b of Figure 6C. Since this embodiment utilizes a self-oxidation technique instead of additionally depositing an insulating material, an insulating material is not formed in a peripheral region other than the memory region. Therefore, according to the process of the fourth embodiment, an additional CMP step is not required to eliminate the step height difference between the memory region and the peripheral region.

In summary, the method of the present invention can produce a large and small contact window, and the side of the contact window between the bit lines is a curved surface, so that the contact between the active area contact window and the substrate (active area) can be increased. Area, in turn, to reduce the resistance of the contact window Rs fruit. Moreover, since the active area contact window is formed first, instead of the conventional method of forming the insulating layer in which the contact window is formed, it is possible to avoid a short circuit or a low threshold voltage caused by a protective structure such as a gap wall on the side of the bit line. problem. In addition, the present invention can also utilize self-oxidation techniques to form an insulating layer between the active area contact windows to avoid the problem of a step height difference between the memory area and the peripheral area.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Substrate

100a‧‧‧Contact window area

106a‧‧‧Top

124‧‧‧Active area contact window

124a‧‧‧ top

124b‧‧‧ bottom

Claims (13)

A method for manufacturing an active area contact window of a dynamic random access memory, the dynamic random access memory comprising at least a substrate, a plurality of isolation structures in the substrate, and a plurality of active regions separated by the isolation structure And a plurality of buried word lines passing through the active area, and a plurality of bit lines on the substrate, wherein each of the active areas includes a plurality of contact window areas, and the manufacturing method includes: Forming a conductive layer on the substrate to cover the contact window region and the bit line; removing the conductive layer outside the contact window region to form a plurality of active region contact windows; and forming on the substrate An insulating layer covering the active area contact window. The method for manufacturing an active area contact window of a dynamic random access memory according to claim 1, wherein the method of forming the active area contact window comprises: removing the contact window area by using dot lithography etching; The conductive layer forms a cylindrical contact area of the active region. The method for manufacturing an active area contact window of a dynamic random access memory according to claim 1, wherein the method of forming the active area contact window comprises: planarizing the conductive layer until the bit line is exposed a top surface; and removing the conductive layer outside the contact window region by linear lithography. The method of manufacturing an active area contact window of a dynamic random access memory according to claim 1, wherein the step of removing the conductive layer other than the contact window area comprises leaving a plurality of conductive layer; Method of forming the insulating layer A part of the conductive layer is converted into an insulating material by using a self-oxidation technique. The method for manufacturing an active area contact window of a dynamic random access memory according to claim 4, wherein the self-oxidation technique comprises on-site vapor generation technology (ISSG), wet oxidation method or low temperature plasma oxidation method. (SPA oxide). The method for manufacturing an active area contact window of a dynamic random access memory according to claim 1, wherein the method of forming the insulating layer comprises: conformally forming a tantalum nitride covering the active area contact window a layer and a ruthenium oxynitride layer; and a spin-on glass layer is formed on the substrate by spin coating. The method of manufacturing an active area contact window of a dynamic random access memory according to claim 1, wherein the method of forming the insulating layer comprises using the active layer contact window deposited on the substrate by an atomic layer. A layer of tantalum nitride is filled between them. The method for manufacturing an active area contact window of a dynamic random access memory according to claim 1, wherein before forming the conductive layer, further comprising forming a spacer on a side of the bit line to isolate the a conductive layer and the bit line. An active area contact window of a dynamic random access memory, the dynamic random access memory comprising at least a substrate, a plurality of isolation structures in the substrate, a plurality of active areas separated by the isolation structure, and through a plurality of buried word lines of the active area, and a plurality of bit lines intersecting the buried word line on the substrate, wherein each of the active areas includes a plurality of contact window areas The active area contact window is respectively located on the contact window area, wherein each of the active area contact windows is cylindrical; the active area contact window between the two bit lines The side is curved; And the bottom surface area of each of the active area contact windows is larger than the top surface area, and the bottom surface is in direct contact with the contact window area. The active area contact window of the dynamic random access memory according to claim 9, wherein the material of the active area contact window comprises polysilicon. The active area contact window of the dynamic random access memory according to claim 9, wherein the surface of the active area contact window in contact with the bit line is a plane. The active area contact window of the dynamic random access memory according to claim 9, wherein the top surface of the active area contact window is higher than a top surface of the bit line. The active area contact window of the dynamic random access memory according to claim 9, wherein the top surface of the active area contact window is flush with a top surface of the bit line.