Patent Publication Number: US-6215151-B1

Title: Methods of forming integrated circuitry and integrated circuitry

Description:
RELATED PATENT DATA 
     This patent resulted from a divisional application of U.S. patent application Ser. No. 08/912,108, filed Aug. 4, 1997, entitled “Methods of Forming Integrated Circuitry and Integrated Circuitry”, naming Zhiqiang Wu et al. as inventors, and which is now U.S. Pat. No. 5,946,564 the disclosure of which is incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This invention relates to methods of forming integrated circuitry and to related integrated circuitry. 
     BACKGROUND OF THE INVENTION 
     An MOS (metal-oxide-semiconductor) structure in semiconductor processing is created by superimposing several layers of conducting, insulating and transistor forming materials. After a series of processing steps, a typical structure might comprise levels of diffusion, polysilicon and metal that are separated by insulating layers. Integrated circuitry can employ different types of MOS structures or transistors which are formed on a common substrate. NMOS transistors include source/drain diffusion regions which comprise an n-type dopant. PMOS transistors include source/drain diffusion regions which comprise an p-type dopant. CMOS (complementary metal-oxide-semiconductor) is so-named because it uses two types of transistors, namely an n-type transistor (NMOS) and a p-type transistor (PMOS). These are fabricated in a semiconductor substrate, typically silicon, by using either negatively doped silicon that is rich in electrons or positively doped silicon that is rich in holes. Different dopant ions are utilized for doping the desired substrate regions with the desired concentration of produced holes or electrons. 
     NMOS remained the dominant MOS technology as long as the integration level devices on a chip was sufficiently low. It is comparatively inexpensive to fabricate, very functionally dense, and faster than PMOS. With the dawning of large scale integration, however, power consumption in NMOS circuits began to exceed tolerable limits. CMOS represented a lower-power technology capable of exploiting large scale integration fabrication techniques. 
     CMOS fabrication does however present a number of challenges to the fabricator as compared to using PMOS or NMOS alone. Specifically, typically independent or separate masking steps are utilized for masking one of the p-type regions while the n-type region is being doped. Also, the n-type regions are separately masked when the p-type regions are being doped. Accordingly, typical transistor flows use one mask each to form the n-channel and p-channel transistor source and drain regions. Higher levels of integration result in denser and denser circuits, leading CMOS fabrication to more difficulties. One manner of simplifying transistor flows has been to combine masking steps. This in itself presents unique challenges which this invention addresses. 
     It would be desirable to develop methods which further facilitate formation of integrated circuitry devices. It would also be desirable to develop methods which further facilitate formation of NMOS and PMOS devices. 
     SUMMARY OF THE INVENTION 
     Integrated circuitry and methods of forming integrated circuitry are described. In one implementation, a common masking step is utilized to provide source/drain diffusion regions and halo ion implantation or dopant regions relative to the source/drain regions within one well region of a substrate; and well contact diffusion regions within another well region of the substrate. The common masking step preferably defines at least one mask opening over the substrate within which the well contact diffusion region is to be formed, and the mask opening is suitably dimensioned to reduce the amount of halo ion implantation dopant which ultimately reaches the substrate therebelow. According to one aspect, a plurality of mask openings are provided. According to another aspect, a suitably-dimensioned single mask opening is provided. In yet another aspect, a unique well region construction is provided with one or more complementary mask openings which is (are) configured to, in connection with the provision of the halo ion implantation dopant, block the amount of implantation dopant which ultimately reaches the substrate adjacent the well contact diffusion regions. Accordingly, at least some of the well contact diffusion region(s) remain in substantial contact with the well region after the doping of the substrate with the halo ion implantation dopant. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are described below with reference to the following accompanying drawings. 
     FIG. 1 is a diagrammatic sectional view of a semiconductor wafer fragment at one processing step. 
     FIG. 2 is a top plan view of a portion of the FIG. 1 wafer fragment. 
     FIG. 3 is a top plan view of a semiconductor wafer fragment at one processing step in accordance with one preferred embodiment of the invention. 
     FIG. 4 is a view taken along line  4 — 4  in FIG.  3 . 
     FIG. 5 is a view which is similar to the FIG. 4 view, but one which shows another preferred embodiment of the invention. 
     FIG. 6 is a top plan view of a semiconductor wafer fragment at one processing step in accordance with another preferred embodiment of the invention. 
     FIG. 7 is a view taken along line  7 — 7  in FIG.  6 . 
     FIG. 8 is a view taken along line  8 — 8  in FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8). 
     Referring to FIG. 1, portions of a semiconductor wafer fragment in process are indicated generally with reference numeral  10 . Such comprises a bulk semiconductive substrate  12 . In the context of this document, the term &#39;semiconductive substrate is defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above. 
     In a preferred implementation, substrate  12  comprises a first well region  14  and an adjacent second well region  16 . According to one aspect, substrate  12  comprises an intrinsically p-type doped substrate and first well region  14  comprises an n-well or well region which is formed through suitable provision of n-type dopant into the substrate. Accordingly, second well region  16  can comprise the intrinsically p-type doped substrate. Alternately, p-type dopant can be separately provided into the substrate adjacent first well region  14  to form second well region  16 . A conductive line  18  is formed over substrate  12  and relative to second well region  16 . In an exemplary and preferred aspect, conductive line  18  constitutes a portion of NMOS circuitry. Similar conductive lines having associated source/drain diffusion regions are formed over or relative to well region  14 , but for purposes of brevity are not specifically shown. Such conductive lines over well region  14  constitute, in accordance with this aspect of the invention, PMOS circuitry which is supported by the well region. Typically, conductive lines such as conductive gate line  18  include a thin oxide layer  20 , a conductive polysilicon layer  22 , a conductive silicide layer  24  and an insulative cap  26 . Such lines are typically provided with insulative sidewall spacers  28  as shown. Such constitutes only an exemplary conductive line construction. 
     Referring to FIGS. 1 and 2, an isolation oxide region  30  is formed relative to substrate  12 . A portion of isolation oxide region  30  is shown in FIG. 1 laterally spaced from p-type well region  16 . An active area  32  constitutes an area relative to which PMOS circuitry or devices, such as the conductive lines mentioned above, are to be formed. Masking steps are ideally combined to reduce the number of processing steps in a particular processing flow. For example, it is desired to use a common masking step to form source/drain diffusion regions and the heavily doped diffusion or tie contact to an opposing well region. Accordingly, a masking material  34  (FIG.  1 ), such as photoresist, is provided over substrate  12  and patterned to define mask openings  35 ,  36  relative thereto. For purposes of the ongoing discussion, mask opening.  35  over well region  14  constitutes a first mask opening or openings, and mask opening  36  over well region  16  constitutes a second mask opening or openings. Accordingly, such constitutes a common masking step in which the substrate is masked relative to first and second well regions  14 ,  16  respectively. Lightly doped drain regions (LDDs)  37  are provided and can typically be formed in advance of the illustrated sidewall spacers  28 . An amount of LDD dopant is also received within well region  14 . 
     A first conductivity type impurity is provided into the substrate through mask openings  36  to form source/drain diffusion regions  38  relative to the NMOS device in unmasked portions of well region  16 , and well contact diffusion regions  38  relative to well region  14 . In this exemplary implementation, the first conductivity type impurity constitutes an n-type impurity. A second conductivity type impurity is also provided into the substrate through the common mask openings and constitutes p-type halo ion implant regions  40  which are received within well region  16  relative to the NMOS devices. An exemplary p-type dopant is boron. Of course, the provision of the second conductivity type impurity can take place prior to provision of the first conductivity type impurity. 
     A problem stemming from the use of a common masking step is that such can also undesirably enable the illustrated p-type diffusion regions  40  to form within well region  14 . While the p-type diffusion regions  40  are desirable relative to the illustrated NMOS conductive line  18 , such regions are not desirable relative to the PMOS devices of well region  14 . Such undesirable regions can entirely occupy space between well contact diffusion region  38  and well region  14 , and can extend laterally from well region  16  to isolation oxide  30 . Accordingly, desirable electrical connection of well contact diffusion region  38  relative to well region  14  is made more difficult because of the presence of p-type diffusion region  40 . 
     Referring to FIGS. 3 and 4, one preferred aspect of the invention is set forth. Like numbers from the above-described embodiment are utilized where appropriate, with differences being indicated with the suffix “a” or with different numerals. Accordingly, and in a common masking step, substrate  12  is masked relative to first and second well regions  14 ,  16 . Such defines at least two, and preferably more, spaced apart mask openings  35   a  relative to first well region  14 . As best seen in FIG. 3, the illustrated mask openings  35   a  individually extend from active area  32 , over isolation oxide region  30 , over well region  14  and into a portion of substrate  12  which comprises well region  16  (not specifically designated). First mask openings  36  (FIG. 1) are also provided over well region  16  as in the example above. With the mask openings  35   a ,  36  in place, first conductivity type impurity is provided into substrate  12  thereby doping the substrate through the respective mask openings. Accordingly, at least two well contact diffusion regions  38   a  (FIG. 4) are formed within well region  14 . Such also desirably forms the FIG. 1 source/drain diffusion regions  38 . Second conductivity type impurity is provided into the substrate to provide the halo ion implantation regions  40  of FIG.  1 . Some of the second conductivity type impurity is provided through mask openings  35   a  and forms dopant regions  40   a  within well region  14 . 
     According to one aspect of the invention, dopant regions  40   a  have individual average dopant depths within the substrate which are different from those of well contact diffusion regions  38   a  in well region  14  and source/drain regions  38  in well region  16  (FIG.  1 ). The difference in average dopant depth between well contact diffusion regions  38   a  and regions  40   a , together with the plurality of well contact diffusion regions ensures that at least some portions of the individual well or tie contact diffusion regions remain in substantial physical contact with their associated well regions. Exemplary portions in such physical contact are illustrated at  39  and constitute sidewall portions of the individual well contact diffusion regions. Hence, electrical contact between individual well contact diffusion regions and the associated well region in which each is formed is, better achieved after the second conductivity type doping. In the illustrated example, the average dopant depths of the second conductivity type dopant regions  40   a  are greater than those of well contact diffusion regions  38   a  (FIG.  4 ). The average dopant depth of the second conductivity type dopant can, however, be less than the average dopant depth of well contact diffusion regions  38   a  as discussed in more detail below. 
     The masking of substrate  12  in the embodiment just described, defines a plurality of discrete mask openings  35   a  which are not interconnected within first well region  14 . 
     Referring to FIG. 5, an alternate preferred embodiment is shown. Like numbers from the above-described embodiment are utilized where appropriate, with differences being indicated with the suffix “b” or with different numerals. Here, masking material  34   b  is formed over the substrate and patterned to form the illustrated mask openings  35   b . Mask openings  36  (FIG. 1) are also formed to accommodate formation of the above described source/drain regions. In this embodiment, mask openings  35   b  are suitably dimensioned so that, in concert with provision of the second conductivity type dopant, at least some portions of individual well contact diffusion regions  38   b  remain in physical contact with well region  14  after both the well contact diffusion regions and the FIG. 1 halo ion implant regions  40  are formed. 
     In one aspect, individual contact openings  35   b  have a height h, and the second conductivity type dopant regions  40  (FIG. 1) are formed through ion implantation of a suitable impurity at a desired angle away from vertical. The height h of the contact openings is selected to effectively block or interfere with the second conductivity type dopant so that, in a worst case, only dopant regions  40   b  are formed relative to the well contact diffusion regions  38   b . An exemplary height h for the contact openings is about lm and an example doping angle away from vertical is 30°. Of course, other heights and doping angles can be used. 
     In another aspect, individual contact openings  35   b  have a width w, and the second conductivity type dopant regions  40  (FIG. 1) are formed through ion implantation of a suitable impurity at a desired angle away from vertical. An exemplary width w is about 0.5 μm and a suitable doping angle is about 30°. Together, selection of an appropriate width or widths for contact openings  35   b  and an appropriate doping angle at which the FIG. 1 source/drain diffusion regions are formed can ensure that reduced amounts of the second conductivity type dopant are received within well region  14 . 
     In another aspect, both the height and width of the contact openings are selected so that, in concert with the desired angled ion implantation, only dopant regions  40   b  are formed. The illustrated dopant regions  40   b  have average dopant depths which are different, and preferably less than the dopant depths of the well contact diffusion regions. 
     Desirable advantages of the above-described aspects are that at least some portions of the individual well contact diffusion regions remain in substantial physical contact with the associated well region in which each is formed. Exemplary portions are illustrated at  39   b . Accordingly, portions of the substrate within the mask openings are not doped by the second doping which facilitates subsequent electrical contact thereto. 
     Referring to FIG. 6, an alternate preferred embodiment of the invention is set forth. Like numbers from the above-described embodiment are utilized where appropriate, with differences being indicated with the suffix “c” or with different numerals. 
     A first well region  14   c  is formed within substrate  12  and includes a main body portion  42 . At least one extension portion  44  which is joined with main body portion  42  and extends generally away therefrom. In the illustrated and preferred embodiment, a plurality of extension portions  44  are provided, with three such extension portions being illustrated. As in the above-described embodiments, a masking layer  34   c  (FIGS. 7 and 8) is formed over the substrate and in a common masking step, a first mask opening  35   c  is formed over well region  14   c  and extension portions  44 , and a second mask opening  36  (FIG. 1) is formed over well region  16 . The mask openings over extension portions  44  define interconnected mask openings within first well region  14   c . Alternately, a plurality of discrete mask openings similar to those shown at  35   a  in FIG. 3 can be formed relative to the extension portions. 
     According to one aspect of the invention, individual mask openings which extend over individual extension portions  44  have length (l) and width (w) dimensions which are different from one another. An exemplary length dimension l is about 0.8 μm with an exemplary width dimension being somewhat less than 0.8 μm. In addition, mask opening  35   c  comprises a height h. 
     Referring to FIGS. 7 and 8 and with mask openings  35   c  in place, a desired first conductivity type dopant is provided into the substrate to form the well contact diffusion regions. An exemplary well contact diffusion region is shown at  38   c  within an exemplary extension portion  44 . As in the above-described embodiments, the provision of the first conductivity type dopant into the substrate also desirably forms the FIG. 1 source/drain diffusion regions  38  relative to second mask opening  36  over well region  16 . 
     A second conductivity type dopant is provided into the substrate and forms the above described halo ion implantation regions  40  of FIG.  1 . As in the above-described embodiments and as a result of using a same or common masking step to form the exemplary source/drain diffusion regions  38  (FIG.  1 ), halo ion implantation or dopant regions  40  (FIG.  1 ), and well contact diffusion regions  38   c  (FIGS.  7  and  8 ), a certain amount of second conductivity type dopant can reach the substrate within well region  14   c . According to a preferred aspect of the invention, the amount of undesired dopant which is ultimately provided into well region  14   c  is reduced by configuring the mask openings relative to well region  14   c  in a manner which, in connection with the provision or delivery of the second conductivity type dopant, reduces the amount of dopant which reaches the well region. Accordingly, the mask opening is configured to interfere with the second conductivity type doping in a manner which permits physical contact between portions  39   c  of the well contact diffusion region  38   c  and well region  14   c  after the second conductivity type doping is conducted. This will result in exemplary diffusion regions  40   c  which effectively leave at least some portion heavily doped region  38   c  in substantial physical contact with well region  14   c.    
     The preferred manner of providing or delivering the second conductivity type dopant is to conduct an angled ion implantation of the dopant at a desired angle away from vertical. Adjusting the mask opening dimensions, including the length, width, and height thereof relative to the well region can, in concert with the preferred angled ion implantation, reduce the amount of second conductivity type dopant which ultimately reaches well region  14   c , thus forming implant regions  40   c . The dimensions of the mask opening as well as the desired angle at which the angled ion implantation takes place are similar to those described above. 
     In the above-described embodiments, a common masking step is utilized to provide source/drain diffusion regions and halo ion implantation or dopant regions relative to the source/drain regions within one well region of a substrate; and well contact diffusion regions within another well region of the substrate. The masking step preferably defines at least one mask opening over the substrate within which the well contact diffusion region is to be formed, and the mask opening is suitably dimensioned to reduce the amount of halo ion implantation dopant which ultimately reaches the substrate therebelow. According to one aspect, a plurality of mask openings are provided. According to another aspect, a suitably-dimensioned single mask opening is provided. In another aspect, a unique well region construction is provided with one or more complementary mask openings which is (are) configured to, in connection with the provision of the halo ion implantation dopant, block the amount of implantation dopant which ultimately reaches the substrate adjacent the well contact diffusion regions. Accordingly, at least some of the well contact diffusion region(s) remain in substantial contact with the well region after the doping of the substrate with the halo ion implantation dopant. Of course, the above-described first and second conductivity type doping steps can be performed in reverse order. 
     In one implementation, the halo ion implantation dopant defines a dopant region having an average dopant depth within the substrate which is different from that of the well contact diffusion region or the source/drain regions which are contemporaneously formed therewith. The dopant region average depth can be either greater or less than the average dopant depth of the well contact diffusion region. Of course, it is possible that only a negligible amount (or less) of halo ion implantation dopant reaches the subject well region. 
     In a preferred aspect, the above-mentioned source/drain diffusion regions and halo ion implantation regions constitute portions of NMOS circuitry which is formed relative to a p-type well or well region. As mentioned above, exemplary p-type wells or well regions can constitute an intrinsically p-type doped substrate, or p-type well regions which are individually formed or diffused into the substrate. Accordingly, the well contact diffusion regions, in this aspect, are provided relative to the n-type well regions which support the PMOS circuitry. It is to be understood, however, that the above-described implementation is an exemplary implementation only, and is not intended to limit application of the invention. Accordingly, the source/drain diffusion regions and halo ion implantation regions can be provided relative to PMOS devices which are formed over and/or within n-type wells or well regions, and the well contact diffusion regions can be formed relative p-type wells or well regions which support NMOS circuitry. Various dopant concentrations, implant doses, implant energies and the like, which are suitable for forming the above-described integrated circuitry will be understood by those of skill in the art. Exemplary processing parameters are set forth in U.S. Pat. No. 5,534,449, the disclosure of which is expressly incorporated herein by reference. 
     In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.