Patent Publication Number: US-9406569-B2

Title: Semiconductor device having diffusion barrier to reduce back channel leakage

Description:
DOMESTIC PRIORITY 
     This application is a division of U.S. patent application Ser. No. 13/676,412, filed Nov. 14, 2012, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The present disclosure generally relates to a semiconductor device, and more specifically, to a semiconductor device having reduced back channel leakage. 
     Various conventional methods exist for reducing leakage current in the back gate channel of semiconductor devices fabricated on Semiconductor-on-Insulator (SOI) wafers. One technique referred to as “well implantation,” applies an excessive amount of doped impurity such as boron for nFET and arsenic or phosphorus for pFET at specific regions of the back gate channel before forming the gate stack. Another technique referred to as “halo implantation,” applies an excessive amount of doped impurity at specific regions of the back gate channel after performing a gate etching procedure. 
     These doped impurity atoms such as boron, however, may have a high diffusivity in semiconductor materials, such as silicon and diffuse to all place during thermal anneal in normal silicon process flow. As SOI thickness scaling continues to become thinner, it is more difficult to keep a retrograded doping profile, i.e., providing a higher doping concentration at the back channel region while maintaining a lower doping concentration at the surface channel region near front transistor gate. The lack of doping profile control raises the threshold voltage of the transistors, i.e., the front gate Vt, and degrades drive current which results in low device performance. It may be desirable to locate higher doping at the back channel region to suppress back channel leakage without realizing excessive diffusion at the front surface and without excessively increasing the transistor threshold voltage. 
     A leakage path typically forms at corners of the back gate channel. The leakage path causes a reduction in the voltage threshold at corresponding regions of the back gate channel, e.g., the corner of the back gate channel. As a result, the voltage threshold at the back gate channel may decrease. As the voltage threshold at the back gate channel decreases, the back gate channel may realize a partially conductive state, i.e., a parasitic gating phenomenon, thereby causing current to leak from the back gate channel via the leakage path and contribute a significant portion of leakage between the source and drain. Accordingly, operational characteristics of semiconductor devices may be controlled by reducing the occurrence of parasitic gating phenomenon. 
     SUMMARY 
     According to at least one embodiment of the present disclosure, a method of fabricating a semiconductor device comprises implanting impurities to a optimized depth within an active semiconductor layer formed on a buried insulator layer of a semiconductor-on-insulator (SOI) substrate. The method further includes forming a diffusion barrier by implant second impurities in the active semiconductor layer. The impurities to form diffusion barrier is implanted between the impurities and an upper surface of the active semiconductor layer. The method further includes annealing the diffusion barrier material to form a diffusion barrier layer that prevents the first implanted impurities from diffusing therethrough. 
     According to another embodiment of the disclosure, a method of reducing leakage from a gate channel region of a semiconductor device comprises forming first and second trenches through an active semiconductor layer and a buried insulator layer of a semiconductor-on-insulator (SOI) substrate. The first and second trenches define a gate channel region therebetween. The method further includes depositing impurities in at least one leakage region within the active semiconductor layer of the gate channel region, and forming a diffusion barrier layer between the impurities and an upper surface of the gate channel region. The diffusion barrier layer prevents the impurities from diffusing therethrough such that a voltage threshold at the at least one leakage region is increased. 
     In yet another embodiment of the disclosure, a semiconductor memory device comprises a semiconductor-on-insulator (SOI) substrate including an active semiconductor layer formed on a buried insulator layer. A semiconductor device is formed on the SOI substrate, and includes a gate channel region formed between a source region and a drain region. At least one storage element is formed adjacent the gate channel region, and at least one isolation region is disposed between the gate channel region and the at least one storage element. First impurities are implanted near the interface of the active semiconductor layer and buried oxide near the gate channel region. For example, impurities such as boron may be utilized for an nFET device, and phosphorus for a pFET device. The first impurities adjust back channel threshold voltage to reduce the back channel leakage. Second impurities including at least one of nitrogen and carbon form a diffusion barrier that is implanted at a peak position located between the first implanted layer and surface channel such that the semiconductor memory device includes a diffusion barrier layer formed in the active semiconductor layer. The diffusion barrier layer is formed by the second implanted impurities with anneal to increase a voltage threshold at a region shared by the BOX layer, the back gate channel region, and the at least one isolation region. 
     In still another embodiment of the disclosure, a semiconductor-on-insulator (SOI) substrate comprises a bulk semiconductor substrate having a buried insulator layer formed thereon. The SOI substrate further includes an active semiconductor layer disposed on the buried insulator layer. A layer of impurities is formed within the active semiconductor layer. The SOI substrate further includes a diffusion barrier layer formed between the impurities and an upper surface of the active semiconductor layer. The barrier diffusing layer blocks the impurities from diffusing therethrough. 
     Additional features and utilities may be realized through the various embodiments described in the detailed description. Further, other embodiments and utilities of the disclosure are described in detail herein and are considered a part of the claimed embodiments. For a better understanding of the subjected matter and related features, refer to the following description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The subject matter of the various embodiments is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The forgoing and other features of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings.  FIGS. 1-6  are a series of views illustrating a method of forming a semiconductor device according to embodiments of the disclosure, in which: 
         FIG. 1  illustrates a cross-sectional view of a semiconductor-on-insulator (SOI) starting substrate; 
         FIG. 2  illustrates implantation of impurities into an active semiconductor layer of the SOI substrate shown in  FIG. 1 ; 
         FIG. 3  illustrates implantation of atoms to form a diffusion barrier into the active semiconductor layer of the SOI substrate shown in  FIG. 2 ; 
         FIG. 4  illustrates an annealing process applied to the diffusion barrier material of the SOI substrate shown in  FIG. 3 ; 
         FIG. 5  illustrates a diffusion barrier layer formed between impurities and an upper portion of an active semiconductor layer following an annealing process performed on the SOI substrate shown in  FIG. 4 ; and 
         FIG. 6  illustrates the SOI substrate of  FIG. 5  following formation of a semiconductor device, a storage element and an isolation element. 
         FIGS. 7-13  are a series of views illustrating another method of forming a semiconductor device according to embodiments of the disclosure, in which: 
         FIG. 7  illustrates a cross-sectional view of a semiconductor-on-insulator (SOI) starting substrate; 
         FIG. 8  illustrates a plurality of isolation trenches, a plurality of storage trenches, and a channel region located between the isolation trenches following etching of the SOI substrate shown in  FIG. 7 ; 
         FIG. 9  illustrates deposition of impurities into the active semiconductor layer of the gate channel region included with the SOI substrate shown in  FIG. 8 ; 
         FIG. 10  illustrates deposition of a diffusion barrier material into the active semiconductor layer of the gate channel region included with the SOI substrate shown in  FIG. 9 ; 
         FIG. 11  illustrates an annealing process applied to the diffusion barrier material of the SOI substrate shown in  FIG. 10 ; 
         FIG. 12  illustrates a diffusion barrier layer formed between impurities and an upper portion of a gate channel region following an annealing process performed on the SOI substrate shown in  FIG. 11 ; and 
         FIG. 13  illustrates formation of isolation elements and storage elements in the SOI substrate shown in  FIG. 12 . 
         FIGS. 14-19  are a series of views illustrating yet another method of forming a semiconductor device according to embodiments of the disclosure, in which: 
         FIG. 14  illustrates a cross-sectional view of a silicon-on-insulator (SOI) starting substrate following formation of a plurality of isolation trenches, a plurality of storage trenches, and a gate channel region between the isolation trenches; 
         FIG. 15  illustrates deposition of impurities at leakage regions of a gate channel region included in the SOI substrate shown in  FIG. 14 ; 
         FIG. 16  illustrates deposition of a diffusion barrier material into an active semiconductor layer of the gate channel region included with the SOI substrate shown in  FIG. 15 ; 
         FIG. 17  illustrates an annealing process applied to the diffusion barrier material of the SOI substrate shown in  FIG. 16 ; 
         FIG. 18  illustrates a diffusion barrier layer formed between impurities and an upper portion of a gate channel region following an annealing process performed on the SOI substrate shown in  FIG. 17 ; and 
         FIG. 19  illustrates formation of isolation elements and storage elements in the SOI substrate shown in  FIG. 18 . 
         FIG. 20  is a flow diagram illustrating a method of fabricating a SOI substrate including impurities and a diffusion barrier layer; and 
         FIG. 21  is flow diagram illustrating a method of fabricating a semiconductor device including a gate channel having impurities and a diffusion barrier layer. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a starting semiconductor-on-insulator, such as a silicon-on-insulator (SOI) substrate  100  is illustrated. The SOI substrate  100  may extend along an X-axis to define a length, and a Y-axis perpendicular to the X-axis to define a width. The SOI substrate  100  includes a bulk substrate layer  102  and an active semiconductor layer  104 . The bulk substrate layer  102  and active semiconductor layer  104  may be formed from a semiconductor material such as, for example, silicon (Si). The bulk substrate layer  102  may have a width of about 90 nanometers (nm) to about 200 nm. The active semiconductor layer  104  may have a width of about 30 nm to about 200 nm. The SOI substrate  100  further includes a buried insulator layer, such as a buried oxide (BOX) layer  106  for example, formed between the bulk substrate layer  102  and the active semiconductor layer  104 . The BOX layer  106  may comprise, for example, silicon oxide (SiO 2 ) to isolate the active semiconductor layer  104  from the bulk substrate layer  102 . 
     Referring now to  FIG. 2 , impurities  108  may be deposited in the active semiconductor layer  104  of the SOI substrate. In at least one embodiment of the disclosure, for example, the impurities  108  are implanted in the active semiconductor layer  104  and substantially near an interface shared between the BOX layer  106  and the active semiconductor layer  104 . The impurities  108  may be implanted at selected locations in the active semiconductor layer  104 , or may continuously extend across the entire length of the active semi semiconductor layer  104 . In at least one embodiment, the impurities  108  are implanted to form a layer of impurities  108  having a width ranging from about 40 nm to about 80 nm. The impurities  108  may be selected according to the type of semiconductor device to be fabricated. For example, the impurities  108  may include, but are not limited to, boron (B), boron difluoride (BF 2 ) and gallium (Ga), if the semiconductor device is an n-type field effect transistor (FET). In another embodiment, the impurities  108  may include, but are not limited to, arsenic (As) and phosphorous (P), if the semiconductor device is a p-type FET. 
     Referring now to  FIG. 3 , a diffusion barrier material  110  is implanted into the active semiconductor layer  104  of the SOI substrate  100 . The diffusion barrier material  110  may include, for example, nitrogen, carbon, indium, and gallium. Alternatively, the diffusion barrier may include germanium and xenon. According to still a further embodiment, the diffusion barrier material  110  may include a combination of indium, gallium, nitrogen and carbon. For example, the barrier diffusion material  110  may comprise a combination of indium and nitrogen. 
     The diffusion barrier material  110  may be annealed according to a heating process for example, as illustrated in  FIG. 4 , which forms a diffusion barrier layer  112  between the implanted impurities  108  and an upper surface of the active semiconductor layer  104  as further illustrated in  FIG. 5 . The diffusion barrier layer  112  prevents the impurities  108  from diffusing therethrough. That is, the diffusion barrier layer  112  prevents the impurities  108  from diffusing toward an upper surface of the active semiconductor layer  104 , and instead maintains the impurities  108  at a desired region in the active semiconductor layer  104 . The diffusion barrier layer  112  may have a width ranging from about 40 nm to about 80 nm. In at least one embodiment, the diffusion barrier layer  112  has a peak position at about the middle of the active semiconductor layer  104 . Further, the diffusion barrier layer  112  may extend across the length of the active semiconductor layer  112 . However, the formation of diffusion barrier layer  112  is not limited thereto. As a result, an increased V t  may be maintained at a desired implantation region of the active semiconductor layer  104  where the impurities  108  are deposited, as discussed in greater detail below. 
     The SOI substrate  100  having the diffusion barrier layer  112  may be utilized to form one or more semiconductor components, as illustrated in  FIG. 6 . In at least one embodiment, the semiconductor component is a semiconductor memory device  114 . The semiconductor memory device  114  may include, for example, an embedded dynamic random-access memory (eDRAM) cell. It can be appreciated that the eDRAM cell may be included in an eDRAM array device having a plurality of eDRAM cells. 
     The semiconductor memory device  114  may include a SOI substrate  100  having an active semiconductor layer  104  formed on a BOX layer  106  as further illustrated in  FIG. 6 . A semiconductor device  116 , such as a field effect transistor (FET) for example, may be formed on the active semiconductor layer  104  of the SOI substrate  100 . The semiconductor memory device  114  includes a gate channel region  118  formed between a source region  120  and a drain region  122 . At least one storage element  124  is formed adjacent the gate channel region  118 . The storage element  124  may include, for example, a capacitor. A spacer  125  may be formed on one or more inner surfaces of the storage element. The spacer  125  may comprise, for example, nitride. At least one isolation element  126  is disposed between the gate channel region  118  and the at least one storage element  124 . 
     The semiconductor memory device  114  further includes impurities  108  disposed at an implantation region within the active semiconductor layer  104  of the gate channel region  118 . The implantation region may be located, for example, at a region of the gate channel region  118  shared by the active semiconductor layer  104 , the BOX layer  106  and an isolation element  126 . Further, a diffusion barrier layer  112  is formed between the impurities  108  and an upper surface of the gate channel region  118 . The diffusion barrier layer  112  prevents the impurities  108  from diffusing therethrough such that the impurities  108  are substantially maintained at the implantation region. Accordingly, a semiconductor memory device  114  according to an embodiment of the disclosure may realize a reduction of current leakage in the gate channel region  118 . 
     Referring now to  FIGS. 7-13 , a series of illustrations shows a process flow of fabricating a semiconductor device such as, for example, a high density dynamic memory device  128  according to an embodiment of the disclosure. The high density dynamic memory device  128  may include, but is not limited to, an eDRAM device. 
     With respect to  FIG. 7 , a SOI substrate  100  includes a bulk substrate  102 , an active semiconductor layer  104  and a BOX layer  106  disposed between the bulk substrate  102  and the active semiconductor layer  104 . The SOI substrate  100  may be etched to form one or more storage trenches  130  and one or more isolation trenches  132 , as illustrated in  FIG. 8 . The storage trenches  130  may be formed by masking and performing a multi-step etching process on the active semiconductor layer  104 , the BOX layer  106  and the bulk substrate  102  to a desired depth in the bulk substrate  102 . Various methods may be used to form the storage trench  130  including, but not limited to, reactive-ion etching (RIE). The isolation trenches  132  may be formed in the SOI substrate  100  to intersect the active semiconductor layer  104  and the BOX layer  106 . Further, a gate channel region  118  may be defined between adjacent isolation trenches  132 , as further illustrated in  FIG. 8 . 
     Similar to the procedures described in detail above, impurities  108  may be deposited in an active semiconductor layer  104  of the gate channel region  118  as illustrated in  FIG. 9 . A diffusion barrier material  110  may be deposited in the active semiconductor layer  104  as illustrated in  FIG. 10 . The diffusion barrier material  110  may be annealed to form a diffusion barrier layer  112  in the active semiconductor layer  104  between the impurities  108  and an upper portion of the gate channel region  118 , as illustrated in  FIGS. 11-12 . In at least one embodiment of the disclosure, the diffusion barrier layer  112  may extend across a length of the gate channel region  118 . Further, according to at least one embodiment the diffusion barrier layer  112  extends the entire length of the gate channel region  118  defined by opposing isolation elements  126 . 
     One or more storage trenches  130  may be filled with a dielectric material such as, for example, silicon oxide (SiO 2 ) or silicon nitride (Si 3 N 4 ), to form a storage element  124  as illustrated in  FIG. 13 . The storage element  124  may include spacers  125  formed from nitrite, for example, which isolate the storage element  124  from the bulk substrate  102  and/or the BOX layer  106 . The storage element  124  includes, but is not limited to, a capacitor. The isolation trench  132  may be filled with a dielectric material such as, for example, SiO 2  thereby electrically isolating the gate channel region  118  as further illustrated in  FIG. 13 . Accordingly, a semiconductor memory device  128  may be provided including a diffusion barrier layer  112  formed in the gate channel region  118 . 
     As discussed in detail above, the diffusion barrier layer  112  may prevent the impurities  108  from diffusing therethrough such that an increased V t  at a desired region of the gate channel region  118  is maintained and a current leakage is reduced. More specifically, an increased stored charge density may form in the bulk substrate  102  due to a hole charge (or electron charge in the case of a p-type semiconductor device) stored in the storage elements  124 . One or more storage elements  124  may be formed in substantial alignment with one side of the gate channel region  118 , and the increased stored charge density may form where the side of the gate channel region  118  and the side of the storage element  124  are in proximity of one another. This increase in charge density induces an increase in electron density in the active semiconductor layer  104 , also in substantial alignment with the gate channel region  118 . The charge density may occur, for example, in a lower portion of the gate channel region  118  remote from an upper surface of the gate channel region  118  where an applied voltage is less effective to control electron density. Consequently, the increase in electron density may form a leakage region, i.e., leakage path, in the gate channel region  118 . For example, the leakage region may be formed at a portion of the gate channel region  118  shared by the active semiconductor layer  104 , the BOX layer  106  and an isolation element  126 . 
     Moreover, the increase in electron density causes a reduction in the V t  at the lower portion of the gate channel region  118 . As a result, the V t  at the lower portion of the gate channel region  118 , i.e., the back gate voltage threshold V tb , may fall below the voltage threshold of the upper portion of the gate channel region  118 , i.e., V tu  which may be held very low, for example, from about zero volts to about one-half of a negative power supply voltage. As the V tb  falls below the V tu , the lower portion of the gate channel region may realize a partially conductive state, i.e., a parasitic gating phenomenon, thereby causing current to leak from the gate channel region  118  via the leakage region. 
     The implantation of the impurities  108  within the active semiconductor layer  104  may increase the V t  at a desired region of the active semiconductor layer  104  such as, for example, a leakage region. Accordingly, the V t  at the leakage region of the gate channel region  118  may be increased, while the V t  near the surface of the active semiconductor layer  104  may remain at a level preselected as a desired V t  for a particular semiconductor device design. However, various conditions such as heat, for example, may cause the impurities  108  implanted within the active semiconductor layer  104  to diffuse. Consequently, the impurities  108  may diffuse away from the desired implantation region, for example the leakage region, and may travel toward the upper surface of the active semiconductor layer  104 , i.e., the upper surface of the gate channel region  118 . The diffusion barrier layer  112 , however, inhibits the impurities  108  from diffusing away from a desired implantation region. That is, the impurities  108  are blocked by the diffusion barrier layer  112  from diffusing to an upper surface of the active semiconductor layer  104  of the gate channel region  118 . Instead, the impurities  108  are maintained at the desired implantation region in the active semiconductor layer  104  such that the increased V t  at the desired region, such as the leakage region, of the active semiconductor layer  104  is maintained. Accordingly, the parasitic gating phenomenon is prevented and leakage from the gate channel region  118  is reduced. Moreover, the diffusion barrier layer  112  allows fabrication of a semiconductor device  128  where the voltage threshold at a lower portion of the gate channel region, i.e., V tb , may be controlled independently from the voltage threshold at an upper portion of the gate channel region, i.e., V tu . 
     A semiconductor device  128  including a diffusion barrier layer  112  formed in the gate channel region  118  may be fabricated according another embodiment illustrated in  FIGS. 14-19 . Referring to  FIG. 14 , an SOI substrate  100  may be etched to form one or more storage trenches  130  and one or more isolation trenches  132  as discussed in detail above. Impurities  108  may be implanted at one or more desired regions in the active semiconductor layer  104  of the gate channel region  118 , as illustrated in  FIG. 15 . In at least one embodiment, the impurities  108  may be disposed at one or more corners of the active semiconductor substrate  104  corresponding to the gate channel region  118  via an isolation trench  130  as further illustrated in  FIG. 15 . 
     Referring to  FIG. 16 , a diffusion barrier  110  may be formed by implanting at least one of nitrogen and carbon, but not limited to thereto, in the active semiconductor layer  104  of the gate channel region  118 . The diffusion barrier material  110  may undergo an annealing process to form a diffusion barrier layer  112 , as illustrated in  FIGS. 17 and 18 . In at least one exemplary embodiment, the diffusion barrier layer  112  is disposed between the impurities  108  and an upper portion of the active semiconductor layer  104 . Further, the diffusion barrier layer  112  may extend across a length of the gate channel region  118 . In at least one embodiment, for example, the diffusion barrier layer  112  extends across the entire length of the gate channel region  118 . 
     Referring now to  FIG. 19 , storage elements  124  and isolation elements  126  may be formed in the storage trenches  130  and isolation trenches  132 , respectively. The storage trenches  130  may be filled with a dielectric material such as, for example, silicon oxide (SiO 2 ) or silicon nitride (Si 3 N 4 ). The isolation trenches  132  may be filled with a dielectric material such as, for example, SiO 2  to electrically isolate the gate channel region  118 . Accordingly, the impurities  108  may be maintained at the desired implantation areas of the gate channel region  118 , such as the lower corners of the active semiconductor layer  104  corresponding to the gate channel region  118  as illustrated in  FIG. 19 . By maintaining the impurities  108  at the lower corners, an increased V t  at the corners may be maintained, thereby preventing current from leaking from the gate channel region  118  into the isolation elements  126 . 
     Referring now to  FIG. 20 , a flow diagram illustrates a method of fabricating a SOI substrate including impurities and a diffusion barrier layer. At operation  200 , an SOI substrate is formed having a bulk substrate layer, a BOX layer and an active semiconductor layer. The BOX layer is formed between the bulk substrate layer and the active semiconductor layer. The bulk substrate layer and the active semiconductor layer may be formed from silicon, for example, and the BOX layer may comprise, for example, SiO 2 . At operation  202 , impurities are implanted in the active semiconductor layer. In at least one embodiment, the impurities are implanted substantially near an interface shared between the active semiconductor layer and the BOX layer. At operation  204 , a diffusion barrier material is deposited in the active semiconductor layer. The diffusion barrier material may be disposed in a middle of the active semiconductor layer with respect to the impurities and an upper surface of the active semiconductor layer. However, the location of the diffusion barrier material is not limited thereto. At operation  206 , the SOI substrate undergoes an annealing process such that the diffusion barrier material is formed into a diffusion barrier layer, and the method ends. Accordingly, a SOI substrate is formed having a diffusion barrier layer that inhibits the impurities from diffusing therethrough and into an upper portion of the active semiconductor layer. 
     Referring to  FIG. 21 , a flow diagram illustrates a method of fabricating a semiconductor device including a gate channel having impurities and a diffusion barrier layer. At operation  300 , an SOI substrate is formed. The SOI substrate includes a bulk substrate layer, a BOX layer, and an active semiconductor layer formed on the BOX layer. At operation  302 , one or more storage trenches and one or more isolation trenches are formed in the SOI substrate. The trenches may be etched into the SOI substrate according to various etching process including, but not limited to, reactive-ion etching (RIE). A gate channel region may be defined between two isolation trenches. At operation  304 , impurities are implanted in the active semiconductor layer of the gate channel region. At operation  306 , a diffusion barrier material is deposited in the active semiconductor layer of the gate channel region. The diffusion barrier material is annealed to form a diffusion barrier layer at operation  308 . In at least one embodiment of the disclosure, the diffusion barrier layer is disposed between the impurities and an upper portion of the gate channel region such that the impurities are inhibited from diffusing into an upper portion of the gate channel region. Therefore, the gate channel region included in the SOI substrate according to at least one embodiment of the disclosure may realize a reduction in current leakage. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
     The flow diagrams depicted herein are just one example. There may be many variations to this diagram or operations described therein without departing from the spirit of the subject matter of the disclosure. For instance, operations may be performed in a differing order. Additionally, operations may be added, deleted or modified. All of these variations are considered within the scope of the claims. 
     While various embodiments have been described, it will be understood that those skilled in the art, both now and in the future, may make various modifications to the embodiments which fall within the scope of the following claims. These claims should be construed to maintain the proper protection of the subject matter recited therein.