CN210092082U

CN210092082U - Semiconductor structure

Info

Publication number: CN210092082U
Application number: CN201921515065.4U
Authority: CN
Inventors: 陶大伟
Original assignee: Changxin Memory Technologies Inc
Current assignee: Changxin Memory Technologies Inc
Priority date: 2019-09-11
Filing date: 2019-09-11
Publication date: 2020-02-18
Anticipated expiration: 2029-09-11

Abstract

The utility model relates to a semiconductor structure. Wherein the semiconductor structure comprises: a substrate; a plurality of first trenches disposed within the substrate; a plurality of active regions separated by the first trench; a second trench through the active region; a dielectric layer on the upper surface of the substrate; and the window penetrates through the dielectric layer and is connected with the substrate, is arranged between two adjacent first grooves and two adjacent second grooves, and the projection area of the window on the upper surface of the substrate is larger than or equal to the size of an active region between two adjacent first grooves and two adjacent second grooves.

Description

Semiconductor structure

Technical Field

The utility model relates to a DRAM processing field, concretely relates to semiconductor structure.

Background

DRAM (Dynamic Random Access Memory) is a semiconductor Memory widely used in computer systems. Each DRAM generally includes a capacitor and a transistor, with the gate of the transistor connected to the wordline, the drain connected to the hazard, and the source connected to the capacitor. The voltage signal on the word line can control the transistor to be turned on or off, so that data information stored in the capacitor can be read through the bit line, or the data information can be written into the capacitor through the bit line for storage.

With the continuous reduction of the feature size of semiconductor integrated circuit devices, the critical dimension of DRAM is also getting smaller, the process is more and more complicated, and the cost is also getting higher. However, the yield of the DRAM produced in the prior art is limited, and the yield cannot meet the increasing demand.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a semiconductor structure can improve the DRAM yield that produces, adapts to the output demand that rises increasingly.

In order to solve the above technical problem, the following provides a semiconductor structure comprising: a substrate; a plurality of first trenches disposed within the substrate; a plurality of active regions separated by the first trench; a second trench through the active region; a dielectric layer on the upper surface of the substrate; and the window penetrates through the dielectric layer and is connected with the substrate, is arranged between two adjacent first grooves and two adjacent second grooves, and the projection area of the window on the upper surface of the substrate is larger than or equal to the size of an active region between two adjacent first grooves and two adjacent second grooves.

Optionally, the first trench is filled with a dielectric material to form a shallow trench isolation structure.

Optionally, the depth range of the shallow trench isolation structure is 800-1600 nm.

Optionally, the K value of the dielectric material is less than 3.

Optionally, the second trench is filled with a gate material and a dielectric material to form a word line.

Optionally, the dielectric constant of the dielectric material is between 1 and 8.

Optionally, the gate material includes at least one of tungsten, titanium, nickel, aluminum, platinum, titanium nitride, N-type polysilicon, and P-type polysilicon.

Optionally, the window is a square window, and a projection of the square window on the upper surface of the substrate in the length direction of the second trench is wider than a distance between two adjacent first trenches, and a width in the length direction perpendicular to the second trench is wider than a distance between two adjacent second trenches.

Optionally, the window extends vertically downward into the interior of the substrate to a predetermined depth.

Optionally, the dielectric layer comprises an amorphous silicon layer.

The utility model discloses a semiconductor structure can cut off the active area between the adjacent two bit lines completely, prevents the contact of the electric capacity contact window of exerted active area and follow-up formation, prevents the short circuit that causes by the contact between active area and the electric capacity contact window, improves DRAM's production yield, adapts to the DRAM output demand that rises gradually day by day.

Drawings

Fig. 1a is a schematic cross-sectional view of a semiconductor structure in a word line direction according to an embodiment of the present invention.

Fig. 1b is a schematic cross-sectional view of a semiconductor structure in a vertical word line direction according to an embodiment of the present invention.

Fig. 2a is a schematic cross-sectional view of a semiconductor structure in a word line direction according to an embodiment of the present invention.

Fig. 2b is a schematic cross-sectional view of a semiconductor structure in a vertical word line direction according to an embodiment of the present invention.

Fig. 3 is a schematic top view of a semiconductor structure according to an embodiment of the present invention.

Fig. 4a to 4l are schematic structural diagrams corresponding to each step of forming the semiconductor structure according to an embodiment of the present invention.

Fig. 5 is a flowchart illustrating a method for forming a semiconductor structure according to an embodiment of the present invention.

Detailed Description

The research finds that the short circuit problem between the capacitor contact window and the active area in the memory cell of the DRAM is an important factor influencing the production yield of the DRAM. In the prior art, the active region is usually cut off through the bit line contact window, and the active region cannot be completely cut off due to the bit line contact window, so that the active region still exposes on the bit line contact window, and thus, in the subsequent word line forming process, even if silicon nitride is filled on two sides of a gate of a transistor of a DRAM to be used as isolation, the contact between the active region and the capacitor contact window cannot be completely blocked, and the problem of contact short circuit between the capacitor contact window and the active region is caused.

The semiconductor structure provided by the present invention will be described in further detail with reference to the accompanying drawings and the detailed description.

Referring to fig. 1a and fig. 1b, fig. 1a is a schematic cross-sectional view of a semiconductor structure in a word line direction according to an embodiment of the present invention, and fig. 1b is a schematic cross-sectional view of a semiconductor structure in a vertical word line direction according to an embodiment of the present invention.

In this particular embodiment, a semiconductor structure is provided, comprising: a substrate 100; a plurality of first trenches 102 disposed within the substrate 100; a plurality of active regions 107 separated by first trenches 102; a plurality of second trenches 103 passing through the active region 107; a dielectric layer 104 formed on the upper surface of the substrate 100; and the window 101 penetrates through the dielectric layer 104 to be in contact with the upper surface of the substrate 100 and is arranged between two adjacent first trenches 102 and two adjacent second trenches 103, and the projection size of the window 101 on the upper surface of the substrate 100 is larger than or equal to the size of the active region 107 between two adjacent second trenches 103 and two adjacent first trenches 102.

In one embodiment, the material of the substrate 100 may be a single crystal silicon material, and the material structure of the active region 107 may be a single crystal silicon material doped with an element having a resistivity of 5 × 10³Ωm～5×10³Omega m.

In one embodiment, the first trench 102 is filled with a dielectric material to form a shallow trench isolation structure. In the embodiment, the shallow trench isolation structure includes a first trench 102 and a dielectric material filled in the first trench 102, where K is less than 3, K is a relative dielectric constant, which is a ratio of an absolute dielectric constant of the dielectric material to an absolute dielectric constant of a vacuum, the dielectric material is used for isolating shallow trench leakage and mitigating electrical coupling (coupling), the dielectric material may include a silicon oxide material, and the depth of the shallow trench is between 800 nm and 1600 nm to control the transistor isolation degree.

In one embodiment, the second trench 103 is filled with a gate material and a dielectric material to form a word line. In the embodiment, the word line is an embedded word line, the dielectric material layer has a dielectric constant of 1-8, includes one of silicon oxide and silicon nitride, and has a thickness of 1-10 nm; the gate material layer comprises at least one of tungsten, titanium, nickel, aluminum, platinum, titanium nitride, N-type polysilicon and P-type polysilicon, and has a resistivity of 2 × 10^-8Ωm～1×10²Omega m.

In this embodiment, since the projection dimension of the window 101 on the upper surface of the substrate 100 is greater than or equal to the dimension of the active region 107 between two adjacent second trenches 103 and two adjacent first trenches 102, when the window 101 is filled with polysilicon or the like to form a bit line structure, all the active regions 107 between two adjacent second trenches 103 and two adjacent first trenches 102 are covered by bit lines, and there is no active region 107 exposed to the bit lines, which greatly reduces the possibility of the active regions 107 contacting with a capacitance contact (nodeconact). When the semiconductor structure is used for the production and the manufacture of the DRAM, the probability of DRAM scrapping caused by the short circuit of the active region 107 and the capacitor contact window can be effectively reduced, and the production yield of the DRAM is improved.

Referring to fig. 2a and 2b, fig. 2a is a schematic cross-sectional view of a semiconductor structure in a direction of a word line 103 according to another embodiment of the present invention, and fig. 2b is a schematic cross-sectional view of a semiconductor structure in a direction perpendicular to the word line 103 according to another embodiment of the present invention.

In this embodiment, the bit line contact 101 extends vertically downward into the interior of the substrate 100 to a predetermined depth. By setting the depth of the bit line contact window 101 to a certain level, the contact area between the bit line and the word line 103 when the bit line is formed in the bit line contact window 101 is increased, and the conductivity is improved.

In one embodiment, the bit line contact window 101 is filled with polysilicon to form a polysilicon contact layer, a bit line pattern is formed on the polysilicon contact layer by a Pitch doubling (Pitch doubling) method, the pattern is etched to form a bit line electrode, and finally, the portion of the polysilicon contact layer not in contact with the bit line electrode is etched clean to form the bit line structure of the DRAM.

In this embodiment, during the formation of the bit lines, silicon nitride is also formed on the sidewalls of the bit line contact windows 101 to isolate the contact between the active regions 107 and the capacitor contact windows 301.

In this embodiment, two adjacent second trenches 103 are separated by a square window portion, and two adjacent first trenches 102 are also separated by a square window portion, and when the second trenches 103 and the first trenches 102 are filled with the filler, the square windows penetrate into the filler filled in the first trenches 102 and also penetrate into the filler filled in the second trenches 103.

When the first trench 102 is filled as a shallow trench isolation structure, the square window extends deep into the shallow trench isolation structure in the length direction of the second trench, and when the second trench 103 is filled as a word line, the square window extends deep into the interior of the second trench 103 in the direction perpendicular to the length direction of the second trench 103, but does not contact the word line structure.

In one embodiment, dielectric layer 104 comprises a layer of amorphous silicon having a thickness of about 1 nm to about 100 nm. In practice, the specific material and thickness of the dielectric layer 104 may be selected as desired.

In a specific embodiment, the window 101 is a square window, and a width CD2 of the square window projected on the upper surface of the substrate 100 in the length direction of the second trench 103 is greater than the distance between two adjacent first trenches 102, and a width CD1 in the length direction perpendicular to the second trench 103 is greater than the distance between two adjacent second trenches 103.

In this embodiment, the areas of the two adjacent second trenches 103 exposed out of the square window are equal, and the areas of the two adjacent first trenches 102 exposed out of the square window are also equal, so as to ensure that the electrical properties of the regions of the semiconductor structure are uniform.

In fact, the shape of the window 101 may be set as required as long as the projection of the window 101 on the upper surface of the substrate 100 can cover the active regions 107 between two adjacent second trenches 103 and two adjacent first trenches 102. Such as in a hexagonal, octagonal, etc. arrangement.

Referring to fig. 4a to 4l, fig. 4a to 4l are schematic structural diagrams corresponding to various steps of forming a semiconductor structure according to an embodiment of the present invention, and fig. 5 is a schematic step flow diagram of a method for forming a semiconductor structure according to an embodiment of the present invention.

In this embodiment, there is also provided a semiconductor structure forming method including the steps of: s51 providing a substrate 100, referring to fig. 4a, a dielectric layer 104 is formed on a surface of the substrate 100, a plurality of first trenches 102 are formed in the substrate 100, and a plurality of active regions 107 separated by the plurality of first trenches 102 are formed in the substrate 100, and a plurality of second trenches 103 are formed in the active regions 107; s52, a window 101 is formed, the window 101 is in contact with the substrate 100, and is disposed between two adjacent first trenches 102 and two adjacent second trenches 103, and a projected area of the window 101 on the upper surface of the substrate 100 is greater than or equal to a size of the active region 107 between two adjacent first trenches 102 and two adjacent second trenches 103. The window 101 can be seen in fig. 1 to 3.

In one embodiment, prior to the formation of the window 101, the method comprises the steps of: forming a first window 401 penetrating the dielectric layer, the first window 401 being in contact with the upper surface of the substrate 100; forming a second window 402 in the region of the first trench 102 and the second trench 103 exposed by the first window 401, and extending into the substrate 100; a third window is formed downward in the region of the substrate 100 exposed by the first window 401, and the third window extends into the substrate 100 and is communicated with the second window 402.

Referring to fig. 4h, the size of the projection of the first window 401 on the upper surface of the substrate 100 is the same as the size of the projection of the window 101 on the upper surface of the substrate 100, and is also equal to or larger than the size of the active region 107 between two adjacent second trenches 103 and two adjacent first trenches 102. The second window 402 surrounds the active regions 107 mainly formed by two adjacent first trenches 102 and two adjacent second trenches 103 one turn, and extends to a predetermined depth inside the substrate 100.

In this embodiment, the window 101 is formed by the combination of the first window 401, the second window 402, and the third window 403, and the window 101 which can be a bit line contact window is formed.

In this embodiment, since the projection dimension of the first window 401 on the upper surface of the substrate 100 is greater than or equal to the dimension of the active region 107 between two adjacent second trenches 103 and two adjacent first trenches 102, when the bit line structure is formed by filling polysilicon and the like in the window 101 formed according to the first window 401, all the active regions 107 between two adjacent second trenches 103 and two adjacent first trenches 102 are covered by the bit line structure, and there is no active region 107 exposed on the bit line, which greatly reduces the possibility that the active region 107 contacts the capacitor Contact window 301(Node Contact). When the semiconductor structure is used for the production and the manufacture of the DRAM, the probability of DRAM scrapping caused by the short circuit of the active region 107 and the capacitor contact window can be effectively reduced, and the production yield of the DRAM is improved.

In one embodiment, before forming the first window 401 on the surface of the dielectric layer 104, the following steps are included: forming a mask layer 105 on the upper surface of the dielectric layer 104; a photoresist layer 106 is formed on the upper surface of the mask layer 105. Reference is made here to fig. 4b to 4 d.

In one embodiment, the mask layer 105 includes at least a first mask layer 1051 and a second mask layer 1051 stacked in sequence in a direction perpendicular to the upper surface of the substrate 100. In this embodiment, the number of mask layers 105 may be set as needed, and the number of mask layers 105 is large, which is beneficial to the etching process.

In one embodiment, each mask layer may be a combination of one or more of SiN, SiON, and BARC (Bottom Anti-reflective Coating). In actual use, the material of the mask layer 105 may be set as desired. In one particular implementation, the material of each mask layer 105 may be the same or different.

In fig. 4c, the mask layer 105 has two layers, including a first mask layer 1051 disposed on the top surface of the dielectric layer 104, and a second mask layer 1051 disposed on the top surface of the first mask layer 1051. The first mask layer 1051 may be made of carbon or the like and has a thickness of 100-500nm, and the second mask layer 1051 may be made of carbon and has a thickness of 100-500 nm. Actually, the material and thickness of the first mask layer 1051 and the second mask layer 1051 are different.

In one embodiment, before forming the first window 401 on the surface of the dielectric layer 104, the method further comprises the following steps: a pattern is formed on the surface of the photoresist layer 106, wherein the pattern is in the shape of the first window 401. Reference is made here to fig. 4 e.

In this embodiment, the pattern is square, and a width CD2 of the square projected on the upper surface of the substrate 100 in the length direction of the second trench 103 is greater than the distance between two adjacent first trenches 102, and a width CD1 in the length direction perpendicular to the second trench 103 is greater than the distance between two adjacent second trenches 103.

In one embodiment, the first trench 102 is filled with a dielectric material to form a shallow trench isolation structure. The shallow trench isolation structure includes a first trench 102 and a dielectric material filled in the first trench 102, wherein a K value of the dielectric material is generally less than 3, the dielectric material is used for isolating shallow trench leakage and reducing coupling (coupling), the dielectric material may include a silicon oxide material and the like, and a depth of the shallow trench is between 800 nm and 1600 nm to control a transistor isolation degree.

In this embodiment, the second trench 103 is filled with a gate material and a dielectric material to form a word line. The word line is an embedded word line, the dielectric constant of the dielectric material layer is between 1 and 8, the dielectric material layer comprises one of silicon oxide and silicon nitride, and the thickness of the dielectric material layer is between 1 and 10 nanometersTo (c) to (d); the gate material layer comprises at least one of tungsten, titanium, nickel, aluminum, platinum, titanium nitride, N-type polysilicon and P-type polysilicon, and has a resistivity of 2 × 10^-8Ωm～1×10²Omega m.

Referring to fig. 4f, 4g, and 4h, in this embodiment, each of the mask layer 105 and the dielectric layer 104 is sequentially etched down to the upper surface of the substrate 100 according to the pattern formed on the surface of the photoresist layer 106 in a direction perpendicular to the upper surface of the substrate 100 until reaching the upper surface of the substrate 100. At this time, the first window 401 is formed.

In the step corresponding to fig. 4f, the second mask layer 1052 is etched, in the step corresponding to fig. 4g, the first mask layer 1051 is etched, and in the step corresponding to fig. 4h, the dielectric layer 104 is etched.

It is noted that all etches involved in this embodiment are anisotropic etches.

Referring to fig. 4i and 4j, in this embodiment, when forming the second window 402 in the region of the first trench 102 and the second trench 103 exposed by the first window 401, the method includes the following steps: etching downward from the upper surface of the substrate 100 in a direction perpendicular to the upper surface of the substrate 100 by using a first etching gas having a high selectivity ratio to the substrate 100, and etching a region of the first trench 102 exposed out of the first window 401 to a predetermined depth.

Referring to fig. 4k and 4l, in the embodiment, when forming the third window 403 below the region of the substrate 100 exposed by the first window 401, the method includes the following steps: and etching the region of the substrate 100 exposed out of the first window 401 to a predetermined depth from the upper surface of the substrate 100 downwards along a direction perpendicular to the upper surface of the substrate 100 by using a second etching gas having a high selectivity ratio to the filling materials filled in the first trench 102 and the second trench 103.

Thus, the window 101 formed by combining the first window 401, the second window 402, and the third window 403 is finally formed, and each region of the bottom of the window 101 is deep into the substrate 100 by a predetermined depth, so that the bottom of the window 101 is smooth. The window 101 extends into the substrate 100, so that the bit line structure is better electrically connected to the active region 107 when the bit line structure is formed in the window 101.

When the window 101 is formed by etching, first, the first etching gas is used to etch the fillers in the first trench 102 and the second trench 103 on both sides of the window 101 to form a second window 402 surrounding the active region 107, then, the second etching gas is used to etch the substrate 100 to form a third window 403 extending into the substrate 100 by a preset depth, and different etching gases are used for different objects to be etched to make each side wall of the finally obtained window 101 smoother.

In one embodiment, the etching gas is used to etch the substrate 100 and the films formed on the surface of the substrate 100 because the etching gas has good anisotropy, and the substrate 100 and the films formed on the surface of the substrate 100 can be etched perpendicular to the upper surface of the substrate 100 without lateral etching, so that it is ensured that the same image as the image formed on the upper surface of the photoresist layer 106 can be accurately reproduced on the etched film.

In fact, the etching solution can be selected to perform the corresponding etching according to the requirement, but the anisotropy of the etching solution is poor.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A semiconductor structure, comprising;

a substrate;

a plurality of first trenches disposed within the substrate;

a plurality of active regions separated by the first trench;

a plurality of second trenches through the active region;

a dielectric layer on the upper surface of the substrate;

and the window penetrates through the dielectric layer to be in contact with the upper surface of the substrate and is arranged between two adjacent first grooves and two adjacent second grooves, and the projection area of the window on the upper surface of the substrate is larger than or equal to the size of an active region between two adjacent first grooves and two adjacent second grooves.

2. The semiconductor structure of claim 1, wherein the first trench is filled with a dielectric material to form a shallow trench isolation structure.

3. The semiconductor structure of claim 2, wherein the shallow trench isolation structure has a depth in the range of 800-1600 nm.

4. The semiconductor structure of claim 2, wherein the dielectric material has a K value of less than 3.

5. The semiconductor structure of claim 1, wherein the second trench is filled with a gate material and a dielectric material to form a word line.

6. The semiconductor structure of claim 5, wherein the dielectric material has a dielectric constant between 1 and 8.

7. The semiconductor structure of claim 5, wherein the gate material comprises at least one of tungsten, titanium, nickel, aluminum, platinum, titanium nitride, N-type polysilicon, and P-type polysilicon.

8. The semiconductor structure of claim 1, wherein the window is a square window, and a projection of the square window on the upper surface of the substrate has a width in a length direction of the second trench that is greater than a distance between two adjacent first trenches, and a width in a direction perpendicular to the length direction of the second trench that is greater than a distance between two adjacent second trenches.

9. The semiconductor structure of claim 1, wherein the window extends vertically downward into the interior of the substrate to a predetermined depth.

10. The semiconductor structure of claim 1, wherein the dielectric layer comprises an amorphous silicon layer.