Memory structure and manufacturing method thereof

Abstract

A memory structure including a substrate, a first dielectric layer, a second dielectric layer, a charge storage layer, an oxide layer, and a conductive layer is provided. The first dielectric layer is disposed on the substrate. The second dielectric layer is disposed on the first dielectric layer. The charge storage layer is disposed between the first dielectric layer and the second dielectric layer. The oxide layer is located at two ends of the charge storage layer and is disposed between the first dielectric layer and the second dielectric layer. The conductive layer is disposed on the second dielectric layer.

Claims

1. A manufacturing method of a memory structure, comprising: providing a substrate; forming a first dielectric material layer on the substrate; forming a charge storage material layer on the first dielectric material layer; forming a second dielectric material layer on the charge storage material layer; performing a patterning process on the second dielectric material layer, the charge storage material layer, and the first dielectric material layer to form a second patterned dielectric material layer, a patterned charge storage material layer, and a first patterned dielectric material layer; performing an oxidation process on the patterned charge storage material layer to form an oxide material layer at an end of the patterned charge storage material layer; forming a conductive layer on the second patterned dielectric material layer; and removing a portion of the second patterned dielectric material layer, a portion of the patterned charge storage material layer, a portion of the oxide material layer, and a portion of the first patterned dielectric material layer by using the conductive layer as a mask to form a second dielectric layer, a charge storage layer, an oxide layer, and a first dielectric layer, wherein the oxide layer is located at two ends of the charge storage layer.

2. The manufacturing method of the memory structure according to claim 1, wherein a gas used in the oxidation process comprises hydrogen, nitrous oxide, oxygen, or ozone.

3. The manufacturing method of the memory structure according to claim 1, wherein a temperature range of the oxidation process is 800° C. to 900° C.

4. The manufacturing method of the memory structure according to claim 1, wherein a time range of the oxidation process is 10 seconds to 60 seconds.

5. The manufacturing method of the memory structure according to claim 1, wherein a pressure range of the oxidation process is 2 Torr to 8 Torr.

6. The manufacturing method of the memory structure according to claim 1, wherein a top view shape of the oxide material layer comprises a ring shape, and the oxide material layer surrounds the patterned charge storage material layer.

7. The manufacturing method of the memory structure according to claim 1, wherein the patterning process comprises: forming a patterned photoresist layer on the second dielectric material layer; and removing a portion of the second dielectric material layer, a portion of the charge storage material layer, and a portion of the first dielectric material layer by using the patterned photoresist layer as a mask to form the second patterned dielectric material layer, the patterned charge storage material layer, and the first patterned dielectric material layer.

8. The manufacturing method of the memory structure according to claim 7, further comprising: removing the patterned photoresist layer.

9. The manufacturing method of the memory structure according to claim 8, wherein the oxidation process is performed on the patterned charge storage material layer before removing the patterned photoresist layer.

10. The manufacturing method of the memory structure according to claim 8, wherein the oxidation process is performed on the patterned charge storage material layer after removing the patterned photoresist layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

(2) FIG. 1A to FIG. 1F are top views illustrating a manufacturing process of a memory structure according to an embodiment of the invention.

(3) FIG. 2A to FIG. 2F are cross-sectional views taken along section line I-I′ in FIG. 1A to FIG. 1F.

(4) FIG. 3 is a sectional view taken along section line II-II ′ in FIG. 1F.

(5) FIG. 4 is a cross-sectional view illustrating a memory structure according to other embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

(6) FIG. 1A to FIG. 1F are top views illustrating a manufacturing process of a memory structure according to an embodiment of the invention. FIG. 2A to FIG. 2F are cross-sectional views taken along section line I-I′ in FIG. 1A to FIG. 1F. FIG. 3 is a sectional view taken along section line II-II ′ in FIG. 1F.

(7) Referring to FIG. 1A and FIG. 2A, a substrate 100 is provided. The substrate 100 may be a semiconductor substrate such as a silicon substrate. In addition, there may be an isolation structure 102 in the substrate 100. The isolation structure 102 can define the active area AA in the substrate 100. The upper surface S1 of the isolation structure 102 may have a recess R. The recess R may be adjacent to substrate 100. In the present embodiment, although the upper surface S1 of the isolation structure 102 has the recess as an example, the invention is not limited thereto. In other embodiments, as shown in FIG. 4, the upper surface S2 of the isolation structure 202 may be a flat surface. The isolation structure 102 is, for example, a shallow trench isolation structure. The material of the isolation structure 102 is, for example, silicon oxide.

(8) Referring to FIG. 1B and FIG. 2B, a dielectric material layer 104 is formed on the substrate 100. The material of the dielectric material layer 104 is, for example, oxide such as silicon oxide. The method of forming the dielectric material layer 104 is, for example, a thermal oxidation method or a chemical vapor deposition method. In some embodiments, the dielectric material layer 104 may be further formed on the isolation structure 102. In some embodiments, although not shown in FIG. 2B, when the dielectric material layer 104 is formed by the thermal oxidation method, the thickness of the dielectric material layer 104 located on the substrate 100 may be greater than the thickness of the dielectric material layer 104 located on the isolation structure 102.

(9) A charge storage material layer 106 is formed on the dielectric material layer 104. The material of the charge storage material layer 106 may be a charge trapping material. In some embodiments, the material of the charge storage material layer 106 is, for example, nitride such as silicon nitride. The method of forming the charge storage material layer 106 is, for example, a chemical vapor deposition method.

(10) A dielectric material layer 108 is formed on the charge storage material layer 106. The material of the dielectric material layer 108 is, for example, oxide such as silicon oxide. The method of forming the dielectric material layer 104 is, for example, a chemical vapor deposition method.

(11) A patterned photoresist layer 110 may be formed on the dielectric material layer 108. The patterned photoresist layer 110 may expose a portion of the dielectric material layer 108. The patterned photoresist layer 110 may be formed by a lithography process.

(12) Referring to FIG. 1C and FIG. 2C, a portion of the dielectric material layer 108, a portion of the charge storage material layer 106, and a portion of the dielectric material layer 104 may be removed by using the patterned photoresist layer 110 as a mask. Thereby, a patterning process may be performed on the dielectric material layer 108, the charge storage material layer 106, and the dielectric material layer 104 to form a patterned dielectric material layer 108a, a patterned charge storage material layer 106a, and a patterned dielectric material layer 104a. The method of removing a portion of the dielectric material layer 108, a portion of the charge storage material layer 106, and a portion of the dielectric material layer 104 is, for example, a dry etching method.

(13) Referring to FIG. 1D and FIG. 2D, an oxidation process is performed on the patterned charge storage material layer 106a to form an oxide material layer 112 at the end of the patterned charge storage material layer 106a. The top view shape of the oxide material layer 112 may be a ring shape (FIG. 1D). In addition, the oxide material layer 112 may surround the patterned charge storage material layer 106a (FIG. 1D). The material of the oxide material layer 112 is, for example, silicon oxide. In some embodiments, an oxide material layer 114 may be simultaneously formed on the substrate 100 not covered by the patterned dielectric material layer 104a by the oxidation process. In some embodiments, the oxide material layer 114 may be further formed on the isolation structure 102. In some embodiments, when the oxide material layer 114 is formed by the oxidation process, the thickness of the oxide material layer 114 located on the substrate 100 may be greater than the thickness of the oxide material layer 114 located on the isolation structure 102. The material of the oxide material layer 114 is, for example, silicon oxide. The gas used in the oxidation process may include hydrogen (H.sub.2), nitrous oxide (N.sub.2O), oxygen (O.sub.2), or ozone (O.sub.3). The temperature range of the oxidation process is, for example, 800° C. to 900° C. The time range of the oxidation process is, for example, 10 seconds to 60 seconds. The pressure range of the oxidation process is, for example, 2 Torr to 8 Torr.

(14) Furthermore, although the etching process used to form the patterned dielectric material layer 104a, the patterned charge storage material layer 106a, and the patterned dielectric material layer 108a may damage the sidewall of the patterned dielectric material layer 104a, the sidewall of the patterned charge storage material layer 106a, and the sidewall of the patterned dielectric material layer 108a, the sidewall damage of the patterned dielectric material layer 104a, the patterned charge storage material layer 106a, and the patterned dielectric material layer 108a can be repaired by the oxidation process.

(15) The patterned photoresist layer 110 may be removed. The method of removing the patterned photoresist layer 110 is, for example, a dry stripping method or a wet stripping method. In the present embodiment, although the oxidation process is performed on the patterned charge storage material layer 106a to form the oxide material layer 112 before removing the patterned photoresist layer 110, the invention is not limited thereto. In other embodiments, the oxidation process may be performed on the patterned charge storage material layer 106a to form the oxide material layer 112 after removing the patterned photoresist layer 110.

(16) Referring to FIG. 1E and FIG. 2E, a conductive layer 116 is formed on the patterned dielectric material layer 108a. In some embodiments, a portion of the conductive layer 116 may be located on the oxide material layer 114. The conductive layer 116 may be used as a control gate. In addition, a conductive layer 118 may be formed on the oxide material layer 114 (FIG. 1E). Referring to FIG. 1E, the conductive layer 118 may be used as a select gate. The conductive layer 116 and the conductive layer 118 may extend along the direction D1. The material of the conductive layer 116 and the conductive layer 118 is, for example, doped polysilicon. The method of forming the conductive layer 116 and the conductive layer 118 may include the following steps, but the invention is not limited thereto. A conductive material layer (not shown) covering the patterned dielectric material layer 108a and the oxide material layer 114 may be formed. Then, the conductive material layer may be patterned by a lithography process and an etching process to form the conductive layer 116 and the conductive layer 118.

(17) Referring to FIG. 1F, FIG. 2F, and FIG. 3, a portion of the patterned dielectric material layer 108a, a portion of the patterned charge storage material layer 106a, a portion of the oxide material layer 112, and a portion of the patterned dielectric material layer 104a are removed by using the conductive layer 116 as a mask to form a dielectric layer 108b, a charge storage layer 106b, an oxide layer 112a, and a dielectric layer 104b, wherein the oxide layer 112a is located at two ends of the charge storage layer 106b. Since the oxide layer 112a is located at the two ends of the charge storage layer 106b, the two ends of the charge storage layer 106b can be sealed by the oxide layer 112a to prevent charge loss from the two ends of the charge storage layer 106b, thereby improving the data retention capacity and the reliability of the memory device. For example, the oxide layer 112a may be located at two opposite ends of the charge storage layer 106b in the direction D1. The method of removing a portion of the patterned dielectric material layer 108a, a portion of the patterned charge storage material layer 106a, a portion of the oxide material layer 112, and a portion of the patterned dielectric material layer 104a is, for example, a dry etching method.

(18) Furthermore, a portion of the oxide material layer 114 may be removed by using the conductive layer 116 and the conductive layer 118 as a mask to form an oxide layer 114a located under the conductive layer 116 and to form an oxide layer 114b located under the conductive layer 118. The oxide layer 114b may be used as a gate dielectric layer under the conductive layer 118 (select gate). In the present embodiment, although the gate dielectric layer under the conductive layer 118 (select gate) is, for example, the oxide layer 114b, the invention is not limited thereto. In other embodiments, the oxide material layer 114 in FIG. 1D may be removed, and then a new dielectric layer may be formed on the substrate 100, and the dielectric layer may be patterned to form a gate dielectric layer under the conductive layer 118. The method of removing a portion of the oxide material layer 114 is, for example, a dry etching method.

(19) Moreover, in the subsequent manufacturing process, the required components (not shown) such as spacers, doped regions, and interconnect structures may be formed according to product requirements, which are known to one of ordinary skill in the art, and therefore the description thereof is omitted here.

(20) Hereinafter, the memory structure 10 of the present embodiment will be described with reference to FIG. 1F and FIG. 2F. In addition, although the method of forming the memory structure 10 is described by taking the above method as an example, the invention is not limited thereto.

(21) Referring to FIG. 1F and FIG. 2F, the memory structure 10 includes the substrate 100, the dielectric layer 104b, the dielectric layer 108b, the charge storage layer 106b, the oxide layer 112a, and the conductive layer 116. The memory structure 10 may be a non-volatile memory such as a semiconductor-oxide-nitride-oxide-semiconductor (SONOS) memory. The dielectric layer 104b is disposed on the substrate 100. The material of the dielectric layer 104b is, for example, oxide such as silicon oxide. The dielectric layer 108b is disposed on the dielectric layer 104b. The material of the dielectric layer 108b is, for example, oxide such as silicon oxide. The charge storage layer 106b is disposed between the dielectric layer 104b and the dielectric layer 108b. The material of the charge storage layer 106b is, for example, nitride such as silicon nitride. The oxide layer 112a is located at the two ends of the charge storage layer 106b and is disposed between the dielectric layer 104b and the dielectric layer 108b. For example, the oxide layer 112a may be connected between the bottom surface BS of the dielectric layer 108b and the top surface TS of the dielectric layer 104b. The material of the oxide layer 112a is, for example, silicon oxide. The dielectric layer 104b, the dielectric layer 108b, and the oxide layer 112a may surround the charge storage layer 106b (FIG. 2F). The conductive layer 116 is disposed on the dielectric layer 108b. In some embodiments, the conductive layer 116 may cover the sidewall of the oxide layer 112a (FIG. 2F).

(22) In addition, the memory structure 10 may further include an isolation structure 102. The isolation structure 102 is located in substrate 100. The oxide layer 112a may be located above the isolation structure 102. Furthermore, a portion of the dielectric layer 104b, a portion of the charge storage layer 106b, and a portion of the dielectric layer 108b may be located above the isolation structure 102. The upper surface S1 of the isolation structure 102 may have the recess R. The recess R may be adjacent to substrate 100.

(23) Moreover, the material, the arrangement, the forming method, the effect and the like of each component in the memory structure 10 have been described in detail in the above embodiments and are not repeated herein.

(24) Based on the above embodiments, in the memory structure 10 and the manufacturing method thereof, since the oxide layer 112a is located at the two ends of the charge storage layer 106b, the two ends of the charge storage layer 106b can be sealed by the oxide layer 112a to prevent charge loss from the two ends of the charge storage layer 106b, thereby improving the data retention capacity and the reliability of the memory device. In addition, in the manufacturing method of the memory structure 10, although the etching process used to form the patterned dielectric material layer 104a, the patterned charge storage material layer 106a, and the patterned dielectric material layer 108a may damage the sidewall of the patterned dielectric material layer 104a, the sidewall of the patterned charge storage material layer 106a, and the sidewall of the patterned dielectric material layer 108a, the sidewall damage of the patterned dielectric material layer 104a, the patterned charge storage material layer 106a, and the patterned dielectric material layer 108a can be repaired by the oxidation process.

(25) FIG. 4 is a cross-sectional view illustrating a memory structure according to other embodiment of the invention.

(26) Referring to FIG. 2F and FIG. 4, the difference between the memory structure 20 of FIG. 4 and the memory structure 10 of FIG. 2F is as follows. In memory structure 10, the upper surface S1 of the isolation structure 102 may have the recess R. However, in the memory structure 20, the upper surface S2 of the isolation structure 202 may be a flat surface. In addition, the same components in the memory structure 20 and the memory structure 10 are represented by the same reference numerals and are not repeated herein.

(27) In summary, in the memory structure and the manufacturing method thereof in the above embodiments, since the oxide layer is located at the two ends of the charge storage layer, the two ends of the charge storage layer can be sealed by the oxide layer to prevent charge loss from the two ends of the charge storage layer, thereby improving the data retention capacity and the reliability of the memory device. In addition, in the manufacturing method of the memory structure in the above embodiments, the sidewall damage caused by the etching process can be repaired by the oxidation process.

(28) Although the invention has been described with reference to the above embodiments, it will be apparent to one of ordinary skill in the art that modifications to the described embodiments may be made without departing from the spirit of the invention. Accordingly, the scope of the invention is defined by the attached claims not by the above detailed descriptions.