TWI553782B - Method of forming buried word line and isolation structure thereof - Google Patents

Description

Buried word line and manufacturing method thereof

The present invention relates to a method of fabricating a buried word line and its isolation structure, and more particularly to a method of fabricating an isolation structure for self-aligned buried word lines.

In order to improve the accumulative degree of dynamic random access memory to speed up the operation speed of components and meet the needs of consumers for miniaturized electronic devices, buried word line dynamic random access memory (buried word) has been developed in recent years. Line DRAM) to meet the above needs.

However, as the memory accumulation increases, the word line spacing and the isolation structure of the memory array will continue to shrink, resulting in various adverse effects. For example, cell-to-cell leakage, interference between word lines (also known as Row Hammer), t _WR failure, retention failure, bit line Bit Line coupling failure, etc.

Therefore, at present, for the interference between the word lines, there is a method in which the depth of the isolation structure of the buried word line is made deeper than the word line. This approach needs At least two lithography processes, one is to make a relatively deep isolation structure, and the other is to make a buried word line between the isolation structures.

The ideal state is shown in Figure 1, in which the display substrate 100 has an active The isolation structure 102 is defined by the regions 104, and there is a buried word line 106 between the isolation structures 102. Each active region 104 is divided by a buried word line 106 into an intermediate region 108 and contact regions 110 and 112 on both sides. In general, the area A1 of the contact area 110 is substantially equal to the area A2 of the contact area 112.

However, because the size of the component itself is small, it is most likely due to the lithography process. A slight offset in the resulting result of Figure 2. In FIG. 2, since the buried word line 106 is slightly shifted to the right, the area A2 of the contact area 112 is significantly smaller, thereby causing an increase in the resistance here and affecting the performance of the element itself.

The invention provides a manufacturer of a buried word line and an isolation structure thereof The method can produce a self-aligned isolation structure to ensure that the area of the contact area in the active area meets the requirements.

The method for manufacturing a buried word line and an isolation structure thereof according to the present invention includes A multilayer structure composed of a first nitride layer, an oxide layer and a second nitride layer is formed on the surface of a substrate. The multilayer structure is then patterned to form a first trench that exposes the surface of the substrate. The exposed substrate is etched by using a multilayer structure as an etch mask to form a buried word line trench. Buried word lines are formed in the buried word line trenches, and the top of the buried word lines is lower than the surface of the substrate. Connect A mask structure layer is formed in each of the first trenches on the buried word line. The second nitride layer and the oxide layer in the multilayer structure are separately removed to cause the mask structure layer to protrude from the first nitride layer. A spacer is formed in a sidewall of the mask structure layer to form a plurality of self-aligned second trenches. The spacer and the mask structure layer are used as an etching mask to etch and remove the substrate under the second trench to form a plurality of isolation structure trenches, and then form an isolation structure in the isolation structure trench.

In an embodiment of the invention, the first layer of the second nitride layer comprises a tantalum nitride layer or a hafnium oxynitride layer.

In an embodiment of the invention, a ruthenium oxide layer may be formed on the surface of the substrate before forming the multilayer structure. In addition, an active region isolation structure may be formed in the substrate, and the active region isolation structure and the isolation structure divide the substrate into a plurality of active regions.

In an embodiment of the invention, the step of patterning the multilayer structure includes forming a mask layer on the multilayer structure, and patterning the mask layer to expose a portion of the multilayer structure, and then removing the exposed multilayer structure to form the above The first trench, then remove the mask layer.

In an embodiment of the invention, the step of patterning the multilayer structure includes forming a polysilicon layer on the multilayer structure and patterning the polysilicon layer to form a plurality of polycrystalline strip structures, and then conforming on the polycrystalline strip structure The ground layer covers a sacrificial layer to form a plurality of third trenches, and the polysilicon material is filled in the third trench, and the exposed sacrificial layer is removed. Thereafter, the polycrystalline germanium strip structure and the polycrystalline germanium material are used as an etching mask to etch away the exposed multilayer structure, and then the polycrystalline strip structure, The polycrystalline germanium material is removed along with the remaining sacrificial layer.

In an embodiment of the invention, the step of forming the buried word lines includes forming a gate oxide layer on the surface of the buried word line trench, depositing a conductor layer, and etching the conductor layer back.

In an embodiment of the invention, the top of the buried word line is about 20 nm to 80 nm lower than the surface of the substrate.

In an embodiment of the invention, the first mask structure layer and the mask structure layer on one side have a first spacing, and the mask structure layer on the other side has a second spacing, and the first The ratio to the second pitch is between about 1:2 and 1:5.

In an embodiment of the invention, the step of forming the spacers includes conformally covering a third nitride layer on the mask structure layer and performing etch back.

In an embodiment of the invention, the first nitride layer on the surface of the substrate may also be removed after forming the isolation structure.

In an embodiment of the invention, the step of forming the isolation structure includes oxidizing the surface of the isolation structure trench and filling therein with tantalum nitride.

Based on the above, the present invention utilizes a trench above the previously formed buried word line, and additionally forms a convex mask structure layer, and then self-aligns to form a buried type by forming a gap layer of the mask structure layer. The isolation structure of the word line. Therefore, the present invention can effectively reduce the interference between the word lines (Row Hammer) and maintain the area of the contact area in the active area.

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

100, 300‧‧‧ substrate

102, 332‧‧ ‧ isolation structure

104‧‧‧Active Area

106, 320‧‧‧ Buried word line

108‧‧‧Intermediate area

110, 112‧‧‧Contact area

300a‧‧‧ surface

301‧‧‧Oxide layer

302, 306‧‧‧ nitride layer

304‧‧‧Oxide layer

308‧‧‧Multilayer structure

310‧‧‧Polycrystalline strip structure

312‧‧‧ Sacrifice layer

314‧‧‧Polysilicon material

316, 328‧‧‧ Ditch

318‧‧‧ Buried word line ditch

320a‧‧‧ top

322‧‧‧ gate oxide layer

324‧‧‧ Cover structure layer

326‧‧‧ spacers

330‧‧‧Isolation structure ditches

334‧‧‧ lining

336‧‧‧ nitride

A1, A2‧‧‧ area

D1, d2‧‧‧ spacing

T‧‧‧thickness

FIG. 1 is a schematic diagram of a layout of a conventional dynamic random access memory with embedded word lines.

2 is a schematic diagram showing the layout of the dynamic random access memory after the embedded word line of FIG. 1 is shifted.

3A-3J are cross-sectional views showing a manufacturing process of a buried word line and its isolation structure in accordance with an 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.

3A-3J are cross-sectional views showing a manufacturing process of a buried word line and its isolation structure in accordance with an embodiment of the present invention.

Referring to FIG. 3A, a multilayer structure composed of a first nitride layer 302, an oxide layer 304 and a second nitride layer 306 is formed on a surface 300a of a substrate 300. 308. The first and second nitride layers 302 and 306 are, for example, a tantalum nitride layer or a hafnium oxynitride layer. The thickness t of the above oxide layer 304 is, for example, between 20 nm and 200 nm. In addition, a ruthenium oxide layer 301 may be formed on the surface 300a of the substrate 300 before forming the multilayer structure 308, which not only protects the substrate 300 but also enhances the adhesion between the substrate 300 and the first nitride layer 302. In addition, since FIG. 3A is a cross-sectional view, there is an active region isolation structure in another direction not shown in the substrate 300. The active region isolation structure can separate the substrate 300 into a plurality of active regions from the subsequently formed isolation structure. Then, in order to pattern the multilayer structure 308, a mask layer (not shown) may be formed on the multilayer structure 308, and the mask layer may be directly patterned to expose a portion of the multilayer structure 308, and then the exposed multilayer structure 308 may be removed. Form a trench and then remove the mask layer. However, when the component size (e.g., line pitch) is reduced to a certain extent, it may be necessary to modify the process of the above patterned multilayer structure 308, as in the present embodiment, the following process is employed.

Referring again to FIG. 3A, a polycrystalline germanium layer is formed on the multilayer structure 308 (not drawn The polycrystalline germanium layer is patterned to form a plurality of polycrystalline germanium strip structures 310.

Then, referring to FIG. 3B, conformally covering the polycrystalline strip structure 310 A sacrificial layer 312, such as a hafnium oxide layer, is applied. Next, a polysilicon material 314 is filled in the trench formed by the sacrificial layer 312, and part of the polysilicon material 314 can be removed by etch back, chemical polishing or mechanical polishing, and the sacrificial layer 312 is exposed.

Subsequently, referring to FIG. 3C, the exposed sacrificial layer 312 is removed. Due to more The wafer itself has a high etching selectivity ratio between the oxide layer and the nitride layer, so the polysilicon strip structure 310 and the polysilicon material 314 can be used as an etching mask to etch away the exposed multilayer structure 308 to the patterned multilayer structure 308. Result and take this The process forms a first trench 316 that exposes the substrate 300.

Next, referring to FIG. 3D, the polycrystalline bar structure 310, the polycrystalline coffin The material 314 is removed together with the remaining sacrificial layer 312, and the exposed substrate 300 and the hafnium oxide layer 301 are etched away using the multilayer structure 308 as an etch mask to form the buried word line trench 318. In other words, the pattern of the first trench 316 is transferred to the buried word line trench 318 by the process of the figure.

Thereafter, please refer to FIG. 3E to form a buried in the buried word line trench 318. The word line 320 is entered, and the top 320a of the buried word line 320 is lower than the surface 300a of the substrate 300. For example, a gate oxide layer 322 may be formed on the surface of the buried word line trench 318, and a conductor layer (not shown) may be deposited, and the conductor layer may be etched back to obtain the buried word line 320. . In the present embodiment, the top portion 320a of the buried word line 320 is about 20 nm to 80 nm lower than the surface 300a of the substrate 300, but the present invention is not limited thereto. Next, a mask structure layer 324, such as a tantalum nitride layer, a titanium nitride layer, or a structural layer composed of a titanium nitride layer and tungsten, is formed in the first trench 316 on the buried word line 320.

Then, referring to FIG. 3F, the second nitrogen in the multilayer structure 308 is removed, respectively. The layer 306 and the oxide layer 304 are such that the mask structure layer 324 protrudes from the first nitride layer 302. Since the position of the mask structure layer 324 is substantially the same as the layout of the buried word line 320, each mask structure layer 324 may be equidistant between different component designs; or as shown in this figure, each cover The curtain structure layer 324 has a first spacing d1 between the mask structure layer 324 on one side and the mask structure layer 324 on the other side, and a second spacing d2 between the mask structure layer 324 on the other side, and the first and second spacings d1:d2 The ratio is as follows: 1:2 Between 1:5. Since the layout of the buried word line 320 is generally two relatively close in the same active area, a distribution of two pairs is presented.

Thereafter, referring to FIG. 3G, a gap is formed on the sidewall of the mask structure layer 324. Wall 326 is formed to form a plurality of self-aligned second trenches 328. The method for forming the spacers 326 is, for example, conformally covered on the mask structure layer 324 with a third nitride layer (not shown) and etched back. Moreover, if the first nitride layer 302 is still present on the substrate 300, the first nitride layer 302 in the second trench 328 can be removed at this time. In addition, if the mask structure layers 324 are equidistant or spaced apart, spacers 326 can be formed on the sidewalls of each of the mask structure layers 324; conversely, if the spacing between the mask structure layers 324 is small It is possible that, as shown in this figure, a second trench 328 is not formed between the two less spaced mask structure layers 324.

Then, referring to FIG. 3H, since the crucible itself has a high etching selectivity ratio between materials such as tantalum nitride and titanium nitride, the spacers 326 and the mask structure layer 324 can be used as an etching mask to etch the second. The substrate 300 under the trench 328 is formed to form a plurality of isolation structure trenches 330. Because the isolation structure trenches 330 are formed in a self-aligned manner, the areas A1 and A2 of the contact areas on both sides of the buried word line 320 in the same active region are substantially the same. In addition, after forming the isolation structure trenches 330, a boron ion implantation step may be selected for the substrate 300 to prevent interference between the word lines (Row Hammer).

Next, referring to FIG. 3I, an isolation structure 332 is formed in the isolation structure trench 330. In the figure, the step of forming the isolation structure 332 includes oxidizing the surface of the isolation structure trench 330 to form an oxide layer similar to the liner layer 334, and then separating Nitridium nitride 336 is filled into the structural trench 330. And the oxidation is, for example, a thermal oxidation method or a plasma oxidation method.

Subsequently, referring to FIG. 3J, the substrate can be formed after the isolation structure 332 is formed. The first nitride layer 302 on the 300 surface 300a is removed until the tantalum oxide layer 301 or the substrate 300 is exposed.

The above embodiments are only one way to accomplish the present invention, and are not The steps of the present invention are to be completely the same as those of the above embodiment. For example, the manner of forming the isolation structure 332 is as follows, but the present invention is not limited thereto.

(1). The surface of the isolation structure trench 330 is directly oxidized.

(2). Oxygen is applied to the surface of the isolation structure trench 330 by plasma oxidation. Then, spin-on glass (SOG) is filled in the isolation structure trench 330, followed by chemical mechanical polishing (CMP).

(3) oxidizing the surface of the isolation structure trench 330, and then isolating the junction A titanium nitride layer or a structural layer composed of a titanium nitride layer and tungsten is formed in the trench 330.

In summary, the present invention has an isolation structure formed by self-alignment, Effectively reduces the interference between the word lines (Row Hammer) and maintains the area of the contact area within the active area.

Although the present invention has been disclosed above by way of example, it is not intended to limit the present invention. The invention is intended to be within the spirit and scope of the invention, and may be modified and retouched without departing from the spirit and scope of the invention. It is subject to the definition of the scope of the patent application attached.

300‧‧‧Substrate

302‧‧‧ nitride layer

324‧‧‧ Cover structure layer

326‧‧‧ spacers

328‧‧‧ Ditch

Claims (11)

A method for fabricating a buried word line and an isolation structure thereof comprises: forming a multilayer structure composed of a first nitride layer, an oxide layer and a second nitride layer on a surface of a substrate; patterning the a multilayer structure to form a plurality of first trenches exposing the surface of the substrate; etching the removed substrate with the multilayer structure as an etch mask to form a plurality of buried word line trenches; Buried word lines are formed in the buried word line trenches, and the top of the buried word line is lower than the surface of the substrate; in the first trenches on the buried word line Forming a mask structure layer respectively; removing the second nitride layer and the oxide layer in the multilayer structure respectively, so that the mask structure layers protrude from the first nitride layer; and the mask structures are The sidewalls of the layer form a spacer to form a plurality of self-aligned second trenches; the spacers and the mask structure layer are etched masks, and the substrate under the second trenches is etched away to form a plurality of Isolation structure trenches; and within the isolation structure trenches Isolation structure. The method for manufacturing a buried word line and an isolation structure thereof according to claim 1, wherein the first nitride layer and the second nitride layer comprise a tantalum nitride layer or a hafnium oxynitride layer. The method for manufacturing a buried word line and the isolation structure thereof according to claim 1, wherein before forming the multilayer structure, further comprising: forming a ruthenium oxide layer on the surface of the substrate; and on the substrate An active area isolation structure is formed therein, and the active area isolation structure and the isolation structures divide the substrate into a plurality of active areas. The method for manufacturing a buried word line and an isolation structure thereof according to claim 1, wherein the step of patterning the multilayer structure comprises: forming a mask layer on the multilayer structure; patterning the mask layer And exposing a portion of the multilayer structure; removing the exposed multilayer structure to form the first trench; and removing the mask layer. The method for manufacturing a buried word line and the isolation structure thereof according to claim 1, wherein the step of patterning the multilayer structure comprises: forming a polysilicon layer on the multilayer structure; patterning the polysilicon layer to Forming a plurality of polycrystalline strip-like structures; conformally covering a sacrificial layer on the polycrystalline strip-like structures to form a plurality of third trenches; filling the third trenches with polycrystalline germanium material; removing the exposed sacrificial layer And removing the exposed multilayer structure by using the polycrystalline germanium strip structure and the polycrystalline germanium material as an etching mask; and removing the polycrystalline germanium strip structures, the polycrystalline germanium materials and the remaining sacrifice Floor. The method for manufacturing a buried word line and the isolation structure thereof according to claim 1, wherein the step of forming the buried word line comprises: forming a surface of the buried word line trench a gate oxide layer; depositing a conductor layer in the buried word line trench; and etching back the conductor layers. The method for manufacturing a buried word line and an isolation structure thereof according to claim 1, wherein the top of the buried word line is 20 nm to 80 nm lower than the surface of the substrate. The method for manufacturing a buried word line and an isolation structure thereof according to claim 1, wherein each of the mask structure layer and the mask structure layer on one side has a first pitch and another The side of the mask structure layer has a second spacing between the first spacing and the second spacing is between 1:2 and 1:5. The method for manufacturing a buried word line and the isolation structure thereof according to claim 1, wherein the forming the spacers comprises conformally covering a third nitrogen on the mask structure layers. a layer; and etching back the third nitride layer. The method for fabricating a buried word line and an isolation structure thereof according to claim 1, wherein the forming the isolation structure further comprises removing the first nitride layer on the surface of the substrate. The method for manufacturing a buried word line and an isolation structure thereof according to claim 1, wherein the step of forming the isolation structure comprises: Oxidizing the surfaces of the isolation structure trenches; and filling the isolation structure trenches with tantalum nitride.