Abstract:
The present invention provides a manufacturing method of a non-volatile memory including forming a gate dielectric layer on a substrate; forming a floating gate on the gate dielectric layer; forming a first charge blocking layer on the floating gate; forming a nitride layer on the first charge blocking layer; forming a second charge blocking layer on the nitride layer; forming a control gate on the second charge blocking layer; and performing a treatment to the nitride layer to get a higher dielectric constant.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional application of U.S. application Ser. No. 13/494,720, filed on Jun. 12, 2012, now allowed. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a memory and a manufacturing method thereof, and more particularly, to a non-volatile memory and a manufacturing method thereof. 
         [0004]    2. Description of Related Art 
         [0005]    A non-volatile memory is able to retain the stored data even when the electrical power is off. As a result, many electronic products have such memories to provide normal operations when booted. In particular, a flash memory allows multiple data writing, reading, and erasing operations. With these advantages, the flash memory has become one of the most widely adopted memory devices in personal computers and electronic equipments. 
         [0006]    Higher gate coupling ratio (GCR) and transconductance (Gm) are desired for a flash memory to enable the memory to have better performance. The gate coupling ratio and transconductance are associated with the inter-gate dielectric layer. The capacitance of the inter-gate dielectric layer can be increased as the inter-gate dielectric layer becomes thinner and the dielectric constant thereof gets higher. In addition, the gate coupling ratio can be increased as the area of the inter-gate dielectric layer becomes greater. 
         [0007]    However, a thin inter-gate dielectric layer frequently results in the degradation of data retention. Further, a high dielectric constant (high-k) material is usually not compatible with the existing memory processes. Besides, the manufacturing process is difficult when the area of the inter-gate dielectric layer is increased. Therefore, how to effectively increase the gate coupling ratio and transconductance in the existing processes has become one of the main topics in the industry. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a non-volatile memory with a charged nitride layer. 
         [0009]    The present invention further provides a method of forming a non-volatile memory, by which a non-volatile memory with a nitride layer having a higher dielectric constant is formed. 
         [0010]    The present invention provides a non-volatile memory including a gate dielectric layer, a floating gate, a control gate, an inter-gate dielectric structure and two doped regions. The gate dielectric layer is disposed on a substrate. The floating gate is disposed on the gate dielectric layer. The control gate is disposed on the floating gate. The inter-gate dielectric structure is disposed between the control gate and the floating gate. The inter-gate dielectric structure includes a first oxide layer, a second oxide layer and a charged nitride layer. The first oxide layer is disposed on the floating gate. The second oxide layer is disposed on the first oxide layer. The charged nitride layer is disposed between the first oxide layer and the second oxide layer. The doped regions are disposed in the substrate at two sides of the floating gate, respectively. 
         [0011]    According to an embodiment of the present invention, the charged nitride layer includes an N-type dopant therein. 
         [0012]    According to an embodiment of the present invention, the charged nitride layer includes electrons therein. 
         [0013]    According to an embodiment of the present invention, the thickness of the charged nitride layer can be, but is not limited to, between 15 angstroms and 100 angstroms. 
         [0014]    According to an embodiment of the present invention, the thickness of the first oxide layer can be, but is not limited to, between 15 angstroms and 60 angstroms. 
         [0015]    According to an embodiment of the present invention, the thickness of the second oxide layer can be, but is not limited to, between 15 angstroms and 60 angstroms. 
         [0016]    The present invention further provides a manufacturing method of a non-volatile memory including forming a gate dielectric layer on a substrate; forming a floating gate on the gate dielectric layer; forming a first charge blocking layer on the floating gate; forming a nitride layer on the first charge blocking layer; forming a second charge blocking layer on the nitride layer; forming a control gate on the second charge blocking layer; and performing a treatment to the nitride layer to get a higher dielectric constant. 
         [0017]    According to an embodiment of the present invention, the charging treatment includes performing an implantation to the nitride layer with an N-type dopant. 
         [0018]    According to an embodiment of the present invention, wherein the treatment is performed after the step of forming the nitride layer and before the step of forming the second charge blocking layer. 
         [0019]    According to an embodiment of the present invention, the treatment is performed after the step of forming the second charge blocking layer and before the step of forming the control gate. 
         [0020]    According to an embodiment of the present invention, the treatment is performed after the step of forming the control gate and before the step of forming the doped regions. 
         [0021]    According to an embodiment of the present invention, the treatment is performed simultaneously during the step of forming the doped regions. 
         [0022]    According to an embodiment of the present invention, the treatment includes injecting charges into the nitride layer. 
         [0023]    According to an embodiment of the present invention, the treatment is performed after the step of forming the doped regions, and the treatment includes applying a voltage of more than 7 MV/cm to the control gate, so as to inject the electrons into the nitride layer. 
         [0024]    The present invention further provides a manufacturing method of a non-volatile memory including forming a gate dielectric layer on a substrate; forming a floating gate on the gate dielectric layer; forming an inter-gate dielectric structure on the floating gate, wherein the inter-gate dielectric structure comprising a nitride layer; forming a control gate on the inter-gate dielectric structure; forming two doped regions in the substrate respectively at two sides of the floating gate; and performing a trapping treatment to the inter-gate dielectric structure. 
         [0025]    According to an embodiment of the present invention, the trapping treatment comprises performing an implantation to the nitride layer with an N-type dopant. 
         [0026]    According to an embodiment of the present invention, the inter-gate dielectric structure comprises a first charge blocking layer formed on the floating gate, the nitride layer formed on the first charge blocking layer and a second charge blocking layer formed on the nitride layer. 
         [0027]    According to an embodiment of the present invention, the trapping treatment is performed after the step of forming the nitride layer and before the step of forming the second charge blocking layer. 
         [0028]    According to an embodiment of the present invention, the trapping treatment is performed after the step of forming the second charge blocking layer and before the step of forming the control gate. 
         [0029]    According to an embodiment of the present invention, the trapping treatment is performed after the step of forming the control gate and before the step of forming the doped regions. 
         [0030]    According to an embodiment of the present invention, the trapping treatment is performed simultaneously during the step of forming the doped regions. 
         [0031]    According to an embodiment of the present invention, the trapping treatment comprises injecting charges into the inter-gate dielectric structure. 
         [0032]    According to an embodiment of the present invention, the trapping treatment is performed after the step of forming the doped regions, and the charging treatment comprises applying a voltage of more than  7  MV/cm to the control gate, so as to inject the electrons into the nitride layer. 
         [0033]    According to an embodiment of the present invention, the trapping treatment comprises injecting electrons into the inter-gate dielectric structure. 
         [0034]    According to an embodiment of the present invention, the inter-gate dielectric getting higher dielectric constant after the trapping treatment. 
         [0035]    According to an embodiment of the present invention, the inter-gate dielectric structure comprising a nitride material. 
         [0036]    In view of the above, in the present invention, after the nitride layer in the inter-gate dielectric structure is formed, a charging treatment is performed thereto as so to form a charged nitride layer. Therefore, the conductivity of the nitride layer is enhanced and the gate coupling ratio and transconductance of the non-volatile memory is accordingly increased. 
         [0037]    In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures is described in detail below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    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. 
           [0039]      FIG. 1A  to  FIG. 1D  are cross-sectional views illustrating a manufacturing method of a non-volatile memory according to an embodiment of the present invention. 
           [0040]      FIG. 2  is a comparison chart between the inter-gate dielectric structure with a charged nitride layer of the present embodiment and the conventional inter-gate dielectric structure with a non-charged nitride layer. 
           [0041]      FIG. 3  is a correlation chart between the transconductance and the threshold voltage (Vt) of the non-volatile memory of the present embodiment. 
           [0042]      FIG. 4  to  FIG. 6  are cross-sectional views of performing a charging treatment to each of the nitride layers in various embodiments of the present invention. 
           [0043]      FIG. 7A  to  FIG. 7B  are cross-sectional views illustrating a manufacturing method of a non-volatile memory according to another embodiment of the present invention. 
           [0044]      FIG. 8  is a chart for verifying that high memory performance is associated with the charged nitride layer by using an Nbit cell model. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0045]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
         [0046]    Several embodiments are provided below to illustrate a manufacturing method of a non-volatile memory of the present invention. In the method of the present invention, the gate coupling ratio and transconductance of the non-volatile memory can be effectively increased by forming the inter-gate dielectric structure with a charged nitride layer. It is noted that the step of forming the charged nitride layer can be applied to the process for forming the later-described non-volatile memory structure, but the present invention is not limited thereto. In other words, the step of forming the charged nitride layer can be applied to the process for forming any other non-volatile memory structure, as long as such non-volatile memory structure has an oxide/nitride/oxide (ONO) inter-gate dielectric structure. 
         [0047]      FIG. 1A  to  FIG. 1D  are cross-sectional views illustrating a manufacturing method of a non-volatile memory according to an embodiment of the present invention. Referring to  FIG. 1A , a dielectric layer  102  is formed on a substrate  100 . The dielectric layer  102  includes silicon oxide, and the forming method thereof includes performing a thermal oxidation process or a chemical vapour deposition (CVD) process. Thereafter, a conductive layer  104  is formed on the dielectric layer  102 . The conductive layer  104  includes polysilicon, and the forming method thereof includes performing a CVD process. 
         [0048]    Referring to  FIG. 1B , the conductive layer  104  and the dielectric layer  102  are patterned to form a floating gate  104   a  and a gate dielectric layer  102   a.  Thereafter, an oxide layer  106 , a nitride layer  108  and an oxide layer  110  are conformally formed on the substrate  100 . The method of forming the oxide layer  106  includes performing a CVD process. The thickness of the oxide layer  106  can be between 15 angstroms and 60 angstroms, preferably between 30 angstroms and 50 angstroms, and more preferably 40 angstroms. The method of forming the nitride layer  108  includes performing a CVD process. The thickness of the nitride layer  108  can be between 15 angstroms and 100 angstroms, preferably between 30 angstroms and 50 angstroms, and more preferably 40 angstroms. The method of forming the oxide layer  110  includes performing a CVD process. The thickness of the oxide layer  110  can be between 15 angstroms and 60 angstroms, preferably between 30 angstroms and 50 angstroms, and more preferably 50 angstroms. 
         [0049]    Referring to  FIG. 1C , a charging treatment  112  is preformed to the nitride layer  108 , so as to form a charged nitride layer  114 . In the present embodiment, the charging treatment  112  can be, but is not limited to, performing an implantation to the nitride layer  108  with an N-type dopant. The N-type dopant includes phosphorous (P) or boron (B). 
         [0050]    Referring to  FIG. 1D , a conductive layer (not shown) is formed on the substrate  100  covering the oxide layer  110 . The conductive layer includes polysilicon, and the forming method thereof includes performing a CVD process. Thereafter, a pattering step is preformed to remove a portion of the conductive layer, so as to form a control gate  116 . Besides, a portion of the oxide layer  110 , a portion of the charged nitride layer  114  and a portion of the oxide layer  110  are simultaneously removed during the patterning step, so as to form an oxide layer  110   a,  a charged nitride layer  114   a  and an oxide layer  106   a.  The oxide layer  110   a,  the charged nitride layer  114   a  and the oxide layer  106   a  form an inter-gate dielectric structure  118  between the floating gate  104   a  and the control gate  116 . Afterwards, two doped regions  120  are formed in the substrate  100  respectively at two sides of the floating gate  104   a.  The non-volatile memory  10  of this embodiment is thus completed. The method of forming the doped regions  120  includes performing an ion implantation process. 
         [0051]    In the non-volatile memory  10 , the nitride layer in the inter-gate dielectric structure  118  is charged and therefore builds in an internal E-field. As a result, a trapping barrier for electrons becomes shallow, so that the electrons have a greater possibility of moving randomly and the conductivity of the nitride layer is accordingly increased. The nitride layer becomes more conductive and can be regarded as having a reduced electrical thickness, so that the nitride layer having a higher capacitance is obtained. Since the nitride layer in the inter-gate dielectric structure  118  has a higher capacitance, the gate coupling ratio and transconductance of the non-volatile memory  10  can be increased. 
         [0052]      FIG. 2  is a comparison chart between the inter-gate dielectric structure with a charged nitride layer of the present embodiment and the conventional inter-gate dielectric structure with a non-charged nitride layer. The inter-gate dielectric structure of the present embodiment has the same actual thickness as the conventional inter-gate dielectric structure. However, as shown in  FIG. 2 , the inter-gate dielectric structure of the present embodiment exhibits a smaller electrical thickness, which results in, in the present embodiment, a higher capacitance of the inter-gate dielectric structure and therefore a higher gate coupling ratio of the non-volatile memory. 
         [0053]      FIG. 3  is a correlation chart between the transconductance and the threshold voltage (Vt) of the non-volatile memory of the present embodiment. As shown in  FIG. 3 , the threshold voltage is increased as the transconductance becomes greater. In other words, a higher transconductance of the non-volatile memory of the present embodiment can be easily obtained. 
         [0054]    It is noted in the present embodiment, the charged nitride layer  114  is formed by performing a charging treatment  112  to the nitride layer  108  after the oxide layer  110  is formed. However, the present invention is not limited thereto. In other embodiments, the charging treatment  112  to the nitride layer  108  can be performed at any other time point after the nitride layer  108  is formed. For example, some suitable time points are described below. In an embodiment, the charging treatment  112  can be performed to the nitride layer  108  to form the charged nitride layer  114  immediately after the nitride layer  108  is formed, as shown in  FIG. 4 . In another embodiment, the charging treatment  112  can be performed to the patterned nitride layer  108  to form the charged nitride layer  114   a  immediately after the control gate  116  is formed, as shown in  FIG. 5 . In yet another embodiment, the charging treatment  112  can be performed to the patterned nitride layer  108  to form the charged nitride layer  114   a  during the step of forming the doped regions  120 , as shown in  FIG. 6 . 
         [0055]    Further, in the said embodiments, an N-type dopant implantation is performed to the nitride layer in the inter-gate dielectric structure to form a charged nitride layer. However, the present invention is not limited thereto. In another embodiment, a voltage can be applied to the control gate after the non-volatile memory is formed with the existing processes, and electrons are injected into the nitride layer in the inter-gate dielectric structure by using Fowler-Nordheim tunneling (FN tunneling), so as to form a charged nitride layer. 
         [0056]      FIG. 7A  to  FIG. 7B  are cross-sectional views illustrating a manufacturing method of a non-volatile memory according to another embodiment of the present invention. Referring to  FIG. 7A , a non-volatile memory  70  is formed with the similar process steps as described in  FIG. 1A  to  FIG. 1D , except that the 
         [0057]    N-type dopant implantation is omitted after forming the nitride layer  108 , so that a non-charged nitride layer  108   a  is formed. 
         [0058]    Referring to  FIG. 7B , a charging treatment  122  is performed, in which a voltage V is applied to the control gate  116  to inject electrons into the nitride layer  108   a  by using FN tunneling, so as to form a charged nitride layer  124 . The non-volatile memory  70   a  of the present embodiment is thus completed. In this embodiment, the voltage V can be, but is not limited to, more than 7 MV/cm. 
         [0059]      FIG. 8  is a chart for verifying that high memory performance is associated with the charged nitride layer by using an Nbit cell. As shown in  FIG. 8 , after applying a voltage to injecting electrons by using FN tunneling, the transconductance gradually trends up as the variance of the threshold voltage (ΔVt) is increased. 
         [0060]    In summary, in the present invention, after the nitride layer in the inter-gate dielectric structure is formed, a charging treatment is performed thereto as so to form a charged nitride layer. Therefore, the conductivity of the nitride layer is enhanced and the gate coupling ratio and transconductance of the non-volatile memory is accordingly increased. Since the inter-gate dielectric structure has a higher capacitance, the non-volatile memory of the present invention can exhibit higher gate coupling ratio and transconductance. 
         [0061]    The present invention has been disclosed above in the preferred embodiments, but is not limited to those. It is known to persons skilled in the art that some modifications and innovations may be made without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be defined by the following claims.