Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/76—Making of isolation regions between components
  • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
  • H01L21/76202—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers

Definitions

• the present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device and a method of forming a semiconductor device including a step of forming a thermal oxide film as an oxide film for element isolation.
• a silicon oxide film formed by thermally oxidizing silicon is used as an insulating film.
• an oxide film for element isolation is formed partially with a thickness of about several thousand angstroms for the purpose of electrically insulating and isolating adjacent transistors, for example, on a substrate.
• a so-called selective oxidation method is widely used as a method of forming an oxide film for element isolation. That is, a silicon nitride film is deposited on a silicon substrate via, for example, a thin thermal oxide film called a pad oxide film. Then, the silicon nitride film and the pad oxide film in the region where the device isolation oxide film is to be formed are removed by etching, and then the whole is oxidized to form a partially thick device isolation oxide film on the silicon substrate. Form.
• the selective oxidation method has been widely used in the past because of its ability to easily form a thick thermal oxide film at a predetermined position.
• oxidizing species eg, oxygen and H 20
• oxygen and H 20 also diffuse in the direction parallel to the substrate surface in the vicinity of the end of the silicon nitride film, and the oxidation reaction is three-dimensionally performed.
• an oxide film is also formed under the silicon nitride film.
• the oxide film formed under the silicon nitride film decreases in thickness as it moves away from the opening, and often grows like a bird's beak. I have.
• Japanese Unexamined Patent Publication No. 4-366532 discloses that a polycrystalline silicon (polysilicon) thin film is provided under a gay nitride film to oxidize the silicon, and that silicon for purse beak growth is supplied from the polycrystalline silicon thin film. This discloses that the growth of the pearl beak is suppressed and the surface of the silicon substrate is made relatively flat. .
• Japanese Unexamined Patent Publication No. Hei 4-4-23493 discloses that another gay nitride film is directly deposited on the side of the opening of the gay nitride film on a part of the opening on the surface of the silicon substrate or a very thin pad. It is disclosed that, by depositing on an oxide film, diffusion of oxygen from the opening to below the silicon nitride film is reduced and growth of a bird's beak is suppressed.
• An object of the present invention is to provide a method for forming an oxide film for element isolation that can sufficiently reduce the growth of a purse beak and sufficiently planarize the surface of an exposed silicon substrate after removing a non-opening film.
• An object of the present invention is to provide a method for manufacturing a semiconductor device using a film and a semiconductor device.
• the present invention provides a first step of forming at least one thin film on a silicon substrate.
• Step and an opening for exposing at least one predetermined region of the thin film.
• a second procedure for forming a third procedure for selectively oxidizing the silicon substrate through the opening to form an oxide film corresponding to the predetermined region, and removing a thin film other than the oxide film
• the present invention provides a method for forming an oxide film for element separation, comprising the steps of:
• the present invention also provides a first step of forming at least one thin film on a silicon substrate, a second step of forming an opening exposing a predetermined region of at least one of the thin films, A third step of selectively oxidizing the silicon substrate through the step of forming an oxide film corresponding to the predetermined region, and removing a thin film other than the oxide film; A fourth procedure of exposing the oxide film, a fifth procedure of oxidizing the entire exposed surface when the fourth procedure force is completed and at least the oxide film force is exposed, and A sixth procedure of forming an oxide film for element isolation by removing an unnecessary portion formed around the predetermined region in the oxide film formed by the fifth procedure, and then forming a transistor.
• the present invention further provides a semiconductor device obtained by the above manufacturing method.
• FIGS. IA-IH are schematic cross-sectional views showing changes in the cross section of the silicon substrate in the procedure for forming an oxide film for element isolation according to Example 1 of the present invention.
• FIG. 2 is a flowchart showing a procedure for forming an oxide film for element isolation shown in FIGS. IA-IH.
• 3A to 3G are conceptual cross-sectional views showing changes in the cross section of the silicon substrate in the procedure for forming the oxide film for element isolation according to Comparative Example 1.
• FIG. 4 is a graph showing the measurement results of the oxide film thickness distribution near the end of the bird's beak formed at the end of the procedure shown in FIG. 3E.
• FIG. 5 is a graph showing the measurement results of the oxide film thickness distribution near the end of the parse beak formed at the end of the procedure shown in FIG. 1G.
• FIG. 6 is a flowchart showing a procedure for forming an oxide film for element isolation according to Embodiment 2 of the present invention.
• FIG. 7A to 7H are conceptual cross-sectional views showing changes in the cross section of the silicon substrate in the procedure for forming the element isolation oxide film shown in FIG.
• FIG. 8 is a flowchart showing a procedure for forming an oxide film for element isolation according to Embodiment 3 of the present invention.
• 9A to 9H are conceptual cross-sectional views showing changes in the cross section of the silicon substrate in the procedure for forming the oxide film for element isolation shown in FIG.
• 10A to 10P are conceptual cross-sectional views showing changes in the cross section of the silicon substrate in each step of the method for manufacturing the MOS transistor shown in FIG.
• FIG. 11 is a flow chart showing a method for manufacturing a MOS type transistor according to Embodiment 4 of the present invention.
• FIGS. 12A to 12F are conceptual cross-sectional views showing changes in the cross-section of the silicon substrate in each step of the method of manufacturing the flash memory shown in FIG.
• FIG. 13 is a flowchart showing a method for manufacturing a flash memory according to Embodiment 5 of the present invention.
• a first step of forming at least one thin film on a silicon substrate an opening is formed by exposing at least one predetermined region of the thin film, and the rest is a non-opening.
• a second step a third step of selectively oxidizing the silicon substrate through the opening to form an oxide film corresponding to the predetermined region, and removing a thin film other than the oxide film
• a fourth step of exposing at least the oxide film out of the oxide film and the silicon substrate; and a step of additionally oxidizing the entire exposed surface when the fourth step is completed and at least the oxide film is exposed.
• a method for forming an element isolation oxide film comprising: a fifth step; and a sixth step of removing unnecessary portions formed around the predetermined region in the oxide film formed by the fifth step. , And then a transi Formation of a gate oxide film necessary for forming the data, the introduction of impurities, Provided is a method for manufacturing a semiconductor device, which includes forming an electrode, a wiring, and forming an insulating film.
• the first procedure is a procedure of depositing a silicon nitride film on the silicon substrate via a pad oxide film
• the second procedure Is a step of forming an opening by removing at least a part of the silicon nitride film so that the pad oxide film is exposed.
• the fourth step is: A method of removing at least a silicon nitride film among the above, and exposing at least an oxide film of the oxide film and the silicon substrate.
• the first procedure is a procedure for directly depositing a silicon nitride film on the silicon substrate
• the second procedure is Removing the part of the silicon nitride film so as to expose the silicon substrate to form an opening
• the fourth step is removing the silicon nitride film and removing the oxide film and the silicon substrate.
• the first step is a step of depositing a silicon nitride film on the silicon substrate via a pad oxide film;
• the procedure is a step of forming an opening by removing a part of the silicon nitride film and a part of the pad oxide film so that the silicon substrate is exposed.
• a method of removing at least a silicon nitride film of a pad oxide film and exposing at least an oxide film of the oxide film and the silicon substrate is provided.
• a method is provided in which, when the opening is formed in the second step, the silicon substrate is removed by 10 nm or more from the surface. I do.
• the first step is a step of depositing a silicon nitride film on the silicon substrate via a pad oxide film and a polycrystalline silicon thin film.
• the second step includes removing a part of the gay nitride film and a part of the polycrystalline silicon thin film so that the pad oxide film is exposed.
• the fourth step is to remove at least the gay nitride film, the polycrystalline silicon film, and the pad oxide film of the gay nitride film and the polycrystalline silicon film. And a method of exposing at least an oxide film of the oxide film and the silicon substrate.
• the first step is a step of depositing a silicon nitride film on the silicon substrate via a polycrystalline silicon thin film.
• the second step is a step of forming an opening by removing a part of the silicon nitride film and the polycrystalline silicon thin film so that the silicon substrate is exposed.
• the fourth step is a step of forming the silicon nitride film. Removing the film and the polycrystalline silicon film, and exposing at least the oxide film of the oxide film and the silicon substrate.
• the second step is a step of forming an opening by removing at least one predetermined region of the thin film by etching.
• a method of characterizing is provided.
• the additional oxidation in the fifth step is performed until a new oxide film is oxidized to a thickness of 5 nm or more. I will provide a.
• the additional oxidation in the fifth step is performed at the oxidation temperature for a time equal to or longer than the time for forming an oxide film of 5 nm.
• the additional oxidation in the fifth step is from 950 ° C. to 120 ° C., more preferably from 100 ° C.
• the method is performed at an oxidation temperature of C to 110 ° C. for 1 minute or more.
• the present invention provides a method for manufacturing a semiconductor device, comprising: forming at least one thin film formed on a silicon substrate with an opening exposing a predetermined region and leaving the remaining portion unopened; Selectively oxidizing the silicon substrate to form an oxide film corresponding to the predetermined region, and removing a thin film other than the oxide film to expose at least the oxide film of the oxide film and the silicon substrate. Add acid to the entire exposed surface After the formation of the oxide film, an unnecessary portion of the formed oxide film around the predetermined region is removed to form an oxide film for element isolation, preferably when the distance between the non-opening portions is 1 ⁇ m or less.
• the present invention provides a method for manufacturing a semiconductor device, comprising: forming an oxide film on a predetermined region of a silicon substrate by using a selective oxidation method; removing a thin film other than the oxide film; Forming a device isolation oxide film by exposing at least the oxide film and subjecting the entire exposed surface to additional oxidation, and then removing unnecessary portions around the predetermined region in the formed oxide film.
• the surface of the lower silicon substrate between the isolation oxide films is made substantially flat, and then a gate oxide film necessary for forming a transistor, impurities are introduced, electrodes and wires are formed. And a semiconductor device obtained by forming an insulating film.
• At least one thin film for example, a silicon nitride film, a pad oxide film / a silicon nitride film, a polycrystalline silicon film, and a pad oxide film are formed on a silicon substrate.
• a silicon nitride film, a polycrystalline silicon film and a silicon nitride film are formed.
• an opening is formed in at least one of these thin films, for example, a thin film other than the pad oxide film, to expose a predetermined region where an element isolation oxide film is to be formed, and the other is left unopened. Department.
• the silicon substrate is selectively oxidized through the opening by, for example, a thermal oxidation method, and a predetermined region of the silicon substrate exposed from the opening is formed into a thick film of oxidized silicon.
• oxidizing species such as oxygen and H 20 diffuse in the pad oxide film in a direction parallel to the substrate surface, and the oxidation reaction proceeds three-dimensionally.
• a parse beak of gay oxide is formed under a portion of the silicon nitride film or the like.
• a thin film other than the oxidized film of GaN including the purse beak that is, a GaN film, a polycrystalline silicon film, or the like is removed, and the oxidized film of the oxidized silicon or the silicon substrate is exposed.
• Fifth hand oxidize the entire exposed surface.
• the oxidizing species reacts at the interface with the silicon substrate to form a gay oxide film. Silicon exposed at the very beginning of oxidation The oxidizing species diffuses into the already formed oxide film by the direct reaction between the oxidation substrate and the oxidizing species, and then the oxidation reaction diffuses when reaching the oxide film-silicon substrate interface. Proceed by rate-limiting. In other words, when the oxide film thickness already formed has a distribution, the oxidation reaction is started in order from the region having the smaller oxide film thickness.
• the fifth hand In the case of additional oxidation, the bird's beak of the gay oxide film, whose thickness decreases as the distance from the opening increases, the oxidation proceeds faster as the distance from the opening increases. It gradually disappears with the increase, that is, with the increase of the oxide film thickness. As a result, after the end of the supplemental oxidizing force, the non-opening portion becomes almost uniform as compared with the total oxide film thickness before oxidizing. At this time, the peripheral portion other than the predetermined region where the oxide film for element isolation is to be formed is also oxidized, and a thin silicon oxide film is formed in this peripheral portion.
• an unnecessary oxide film formed around a predetermined region where an oxide film for element isolation is to be formed is removed.
• a portion which was originally formed as a parse beak and was oxidized by the fifth procedure to become a relatively thick gay oxide film is also removed at the same time. Since the oxide film thickness in the non-opening portion was substantially uniform due to additional oxidation, the surface after the removal can be made substantially flat. In this way, by performing additional oxidation after the removal of the silicon nitride film, the region having a uniform oxide film thickness can be greatly expanded. Therefore, the surface of the silicon substrate can be sufficiently flattened.
• the silicon nitride film and part of the pad oxide film are exposed in the second step so that the silicon substrate is exposed.
• the silicon substrate may also be removed from the surface by 10 nm or more. This makes it possible to suppress the amount of the silicon oxide film rising from the surface of the silicon substrate when a thick silicon oxide film corresponding to a predetermined region is formed in the third step. And the like can be suppressed to a small level when printing using an exposure method.
• a polycrystalline silicon thin film or a polycrystalline silicon thin film is deposited on a silicon substrate via a pad oxide film.
• An opening may be formed so that the substrate or pad oxide film is exposed, and selective oxidation may be performed in the third procedure.
• part of the silicon consumed when the parse beak of gay oxide is formed in the third step is supplied from the polycrystalline silicon thin film, and the silicon consumed from the silicon substrate is reduced. Parse beak growth can be relatively suppressed.
• the silicon nitride film or the remaining polycrystalline silicon film is removed to expose the oxide film of the silicon oxide or the silicon substrate, and in the fifth step, additional oxidation may be performed on the entire exposed surface.
• the additional oxidation is performed until a thickness of 5 nm or more is oxidized, or a force for performing the oxidation at the oxidation temperature for a time of forming a 5 nm oxide film, or By performing the process at an oxidation temperature of 950 ° C. or more for 1 minute or more, it is possible to surely enlarge a region where the total oxide film thickness is uniform in the non-opening portion after the additional oxidation is completed.
• the portion other than the opening spread between the element isolation oxide films ie, the lower portion of the non-opening portion, for example, the lower portion of the silicon nitride film
• This flatness becomes a serious problem especially when the distance of the non-aperture becomes less than 1 m.
• the flat portion below the non-opening was less than about 56%, and mostly less than about 50%.
• the flat portion is enlarged to about 90%, and the flat portion of usually about 60% or more and about 80% is protected.
• the term "flat" refers to the fact that the surface is not parallel to the atomic level of silicon and is substantially parallel to the flat surface of the original silicon substrate.
• the portion of the silicon substrate 1 below 4C is flat according to the present invention.
• Figure 4 shows an actual pad oxide film thickness of 15 nm and a gay nitride film thickness of 15 O nm.
• the openings during selective oxidation are formed in stripes with a width of 1 m and an interval of 1 // m. Parse beak when thermally oxidized under the condition that the oxide film thickness becomes 0.4 m at 1000 ° C
• the oxide film thickness distribution near O ⁇ Q is shown in Fig. 5.
• Fig. 5 shows the conditions under which the oxide film grows to about 100 nm at 100 ° C again after removing the silicon nitride film after completion of selective oxidation.
• the measurement results of the distribution of the oxidation film thickness after the additional oxidation are shown.
• the vertical axis is the oxide film thickness.
• the width dimension of the silicon nitride film is 1 ⁇ m, and ideally, the oxide film thickness force should be less than 0.5 ⁇ m from the center of the nitride film (that is, 1 Z 2 of the non-opening distance).
• a flat silicon substrate surface can be obtained after removing the oxide film. In fact, since a parse beak grows, the area of uniform oxide thickness from the center of the gay nitride film after selective oxidation is reduced to 0.28 / m (see Fig. 4) ).
• the overall oxide film thickness naturally increases, but it can be seen that the flat region extends to about 0.4 m (see Fig. 5).
• a region having a uniform oxide film thickness can be greatly expanded, and a flat region on the surface of the silicon substrate after removing the oxide film is remarkably formed. Can be expanded to
• the method of the present invention can be applied to the manufacture of a semiconductor device such as a MOS transistor or a flash memory.
• MOS transistor may be used in a memory circuit such as a dynamic random access memory (DRAM) or a static random access memory (SRAM) or an arithmetic circuit such as a processor.
• DRAM dynamic random access memory
• SRAM static random access memory
• processor arithmetic circuit
• Example 1 will be described with reference to FIGS.
• FIG. 2 shows a manufacturing flowchart of the procedure for forming the oxide film for element isolation.
• Figures 1A-1H are conceptual diagrams showing the changes in the cross section of the silicon substrate (wafer) in each procedure at this time.
• step 101 element isolation oxidation is started in step 101, and in step 102, a thermal oxidation method is used on the surface of the silicon substrate 1 (FIG. 1A).
• a pad oxide film 2 is formed. ( Figure 1B).
• step 103 deposit a silicon nitride film 3 having a thickness of, for example, 150 nm on the pad oxide film 2 (FIG. 1C). Note that the pad oxide film 2 is not necessarily required, and the procedure may proceed from step 101 to step 103 to deposit the gay nitride film 3 directly on the surface of the silicon substrate 1.
• step 104 a part of the silicon nitride film 3 on the region where the oxide film for element isolation is to be finally formed is removed by etching, for example, a stripe having a width of 1 m and a spacing of 1 m.
• An opening 20 is formed to expose the pad oxide film 2 (FIG. 1D).
• step 105 the silicon substrate 1 is selectively oxidized through the opening 20 by a thermal oxidation method to form a thick silicon oxide film 4 (IE).
• IE thick silicon oxide film 4
• thermal oxidation is performed under the condition that the oxide film thickness becomes 0.4 ⁇ m at 100 ° C.
• an oxidizing species such as oxygen and oxygen 20 passes through the pad oxide film below the silicon nitride in a direction parallel to the silicon substrate 1 (see FIG. 1E) and the oxidation reaction proceeds three-dimensionally, and below the silicon nitride film 3 (and, if remaining, the pad oxide film 2 grows). Will be formed.
• step 106 removes the silicon nitride film 3 (FIG. 1F).
• step 107 with the thick gay oxide film 4 and the purse beak 4A (and the pad oxide film 2 if remaining) exposed, for example, at 100 ° C. Is oxidized over the entire surface under oxidizing conditions such that it grows to about 100 nm (Fig. 1G)
• step 108 In preparation for forming elements such as a transistor and a resistor on the surface of the silicon substrate 1 later, a known method is used to remove unnecessary gay oxide film 4 formed in the periphery. (For example, chemical methods using drugs or physical dry etch The entire thickness of the silicon oxide film 4 is removed by a predetermined thickness from above to form an oxide film 4 for element isolation (FIG. 1H), and the flow proceeds to step 109 to terminate the flow. I do.
• FIGS. 3G to 3G show a procedure of forming an oxide film for element isolation in a conventional method of manufacturing a semiconductor device.
• the same members as those in FIG. 1 are denoted by the same reference numerals.
• Fig. 3A-3E The procedure of Fig. 3A-3E is the same as the procedure of Fig. 1A-1E described above, and the silicon nitride 1 is placed on the silicon substrate 1 (Fig. 3A) via the pad oxide film 2 (Fig. 3B).
• the film 3 is deposited (FIG. 3C), and the silicon nitride film 3 in a predetermined region is removed by etching to form an opening 20 (FIG. 3D), and thermal oxidation is performed through the opening 20 on the silicon substrate 1.
• the silicon nitride film 3 (and the pad oxide film 2 if remaining) is removed (FIG. 3F), and the unnecessary silicon oxide film 4 formed in the periphery is removed by a known method (for example, An element isolation oxide film 4B is formed by removal by a chemical method using a chemical or a physical dry etching method.
• FIG. 4 shows the measurement results of the oxide film thickness distribution near the end of the gay nitride film 3 formed at the end of the procedure shown in FIG. 3E of Comparative Example 1.
• the horizontal axis of the figure is the distance X from the point 0) in the center of the striped gay nitride film 3 (FIG. 3E) to the opening 20.
• the vertical axis is the thickness of the gay oxide film 4. It is y.
• the width dimension of the gay nitride film 3 is 1 m.
• Example 1 of the present invention in the re-oxidation procedure shown in FIG. 1G, the purse beak 4A (and the pad oxide film 2 if remaining) The oxide film thickness of the part 4 C becomes almost uniform. This will be described in detail below.
• oxidizing species such as oxygen and H 2 O react at the interface of the silicon substrate 1 to form the oxidized silicon film 4.
• the exposed silicon substrate 1 reacts directly with the oxidizing species to form an extremely thin silicon oxide film 4, and thereafter, the oxidizing species in the already formed silicon oxide film 4 Is diffused, and reaches the interface between the silicon oxide film 4 and the silicon substrate 1, whereupon the oxidation reaction proceeds by diffusion control. That is, when the thickness of the already formed gay oxide film 4 has a distribution, the oxidation reaction is started in order from the thin oxide film, the region to the thickness L, and the region.
• the parse beak 4A (see FIG. 1F) having a shape in which the film thickness decreases as the distance from the opening 20 increases, Oxidation proceeds more rapidly as the distance from the opening 20 increases, and the oxidation gradually disappears as the oxidation time increases, that is, as the thickness of the new oxide film increases.
• the film thickness of the part 4 C which was a parse beak after the end of the sufficient reoxidation power becomes almost uniform. This is shown more specifically in FIG.
• FIG. 5 shows the measurement results of the oxide film thickness distribution in the vicinity of the portion 4 C where the bird's beak was formed in the state shown in FIG. 1G.
• the uniform region of the oxide film thickness y on the semiconductor element formation region after the selective oxidation is obtained. Since the area can be expanded, the flat region on the surface of the silicon substrate 1 after the removal of the gay oxide film 4 on the semiconductor element formation area can be expanded, and the high integration of the semiconductor element can be promoted. effective.
• Example 1 the thickness of the pad oxide film 2 was 15 nm, the thickness of the silicon nitride film 3 was 150 nm, and the width of the stripe-shaped opening 20 was 1 ⁇ m. / zm, but is not limited to this. Further, the selective oxidation was performed under the condition that the oxide film thickness becomes 0.4 m at 1000 ° C., but the present invention is not limited to this.
• the additional oxidation was performed under the oxidation conditions such that the oxide film thickness grows to about 100 nm at 100 ° C., but is not limited to this. It is sufficient to appropriately adjust the oxidation conditions (oxidation temperature, time, oxidizing atmosphere, etc.) so that the oxide film thickness after the supplemental oxidation becomes almost uniform.
• the time condition may be a condition that the oxide film strength at the oxidation temperature is at least 5 nm ⁇ the formation time or more, and if possible, until the thickness of 10 nm or more is oxidized.
• Additional oxidation may be performed at an oxidation temperature of 50 ° C or more for 1 minute or more.
• FIG. 6 is a manufacturing flowchart of the procedure for forming an oxide film for element isolation according to Example 2
• Figs. 7A to 7H are conceptual diagrams showing changes in the silicon substrate (wafer) cross section in each procedure. Show.
• the second embodiment is different from the first embodiment in that, after the step 104 of partially removing the silicon nitride film 3 to form the opening 230, the opening is further removed.
• a step 210 is formed in which the silicon substrate 1 is etched away by a thickness of 10 nm or more through 230 to form a step (FIG. 7D).
• the subsequent steps 105 to 109 are the same as in the first embodiment. However, the amount of oxidation at the time of additional oxidation is equal to or larger than in Example 1.
• the same effect as that of the first embodiment can be obtained.
• a step is formed by etching the silicon substrate 1 by 10 nm or more at the opening 230. Therefore, when the thick silicon oxide film 4 is formed, the amount of the surface of the silicon oxide film 4 rising from the surface of the silicon substrate 1 can be suppressed. Accordingly, the present invention is effective in that a step when printing a transistor pattern or the like later by using the exposure method can be reduced.
• This embodiment is an embodiment in which a polycrystalline silicon film is deposited between a pad oxide film 2 and a silicon nitride film 3.
• a polycrystalline silicon film is deposited between a pad oxide film 2 and a silicon nitride film 3.
• Members and procedures equivalent to those in Examples 1 and 2 are given the same reference numerals.
• FIG. 8 is a manufacturing flowchart of a procedure for forming an oxide film for element isolation according to this embodiment
• FIGS. 9A to 9H are conceptual views showing changes in the cross section of a silicon substrate (wafer) in each procedure.
• step 101 element isolation oxidation is started in step 101, and thermal oxidation is applied to the surface of the silicon substrate 1 (FIG. 9A) in step 102, for example, with a film thickness of 15 nm.
• a pad oxide film 2 is formed (FIG. 9B).
• a polycrystalline silicon thin film 317 is deposited on the pad oxide film 2 in step 321.
• step 103 a silicon nitride film 3 having a thickness of, for example, 150 nm is deposited (FIG. 9C). Note that the pad oxide film 2 is not always necessary, and the procedure may shift from step 101 to step 31 to deposit the polycrystalline silicon thin film 317 directly on the surface of the silicon substrate 1.
• step 32 2 the silicon nitride film 3 and the polycrystalline silicon thin film 3 17 on the region where the thick oxide film for element isolation is to be formed are removed by etching, for example, a stripe having a width of 1 m and a spacing of 1 tz m.
• the silicon substrate 1 is selected through the opening 340 by a thermal oxidation method. Oxidized to form a thick gay oxide film 4 (FIG. 9E).
• thermal oxidation is performed under the condition that the oxide film thickness becomes 0.4 m at 100 ° C.
• the vicinity of the opening 340 end of the silicon nitride film 3 is below the silicon nitride film 3 (and, if remaining, the polycrystalline silicon thin film 31). 7 or the polycrystalline silicon thin film 3 17 is oxidized, or the pad oxide film 2 grows) and a bird's beak 4 A is formed.
• the process proceeds to step 323 to remove the silicon nitride film 3 (and the remaining polycrystalline silicon thin film 317) (FIG. 9F).
• step 107 with the thick gay oxide film 4 and the parse beak 4A (and the pad oxide film 2 if remaining) exposed, for example, at 100 ° C. The entire surface is oxidized in such a time as to grow to about 100 nm (Fig. 9G).
• step 108 in order to remove the unnecessary gay oxide film 4 formed in the periphery, the entire gay oxide film 4 is removed by a predetermined thickness from above. Then, an oxide film 4B for element isolation is formed (FIG. 9H), and the flow proceeds to step 109 to end this flow.
• the same effect as that of the first embodiment is obtained.
• a part of the silicon consumed when the bird's beak 4A is formed is supplied from the polycrystalline silicon thin film 3 17 and the total amount of silicon consumed from the silicon substrate 1 is reduced. This also has the effect that the parse beak growth on the side can be relatively suppressed.
• Embodiment 4 will be described with reference to FIGS. 10 and 11.
• This embodiment is an embodiment of a method of manufacturing an M0S type transistor provided with an element isolation oxide film formed by the procedure according to the first to third embodiments.
• Members equivalent to those in Embodiments 1 to 3 ⁇ The same reference numerals are used for the procedures.
• FIGS. 10A to 10D are conceptual diagrams showing changes in the cross section of the silicon substrate (wafer) in each step of the method of manufacturing the MOS transistor according to the present embodiment. Shown in 11.
• the MOS transistor manufactured in this embodiment is used for, for example, a memory circuit or an arithmetic circuit.
• an oxide film 4B for element isolation is formed by the method of any one of Examples 1 to 3 (FIG. 1OA).
• a gate oxide film 418 of a MOS transistor is formed on the surface of the silicon substrate 1 (FIG. 1 OB) c.
• a polycrystalline silicon is formed on the gate oxide film 418 as a gate electrode 419.
• a silicon thin film is deposited and etched as a gate electrode (Fig. 10C).
• the material of the gate electrode is not limited to polycrystalline silicon, but may be a high melting point metal material such as W or Ti, a high melting point metal material or a silicide alloy composed of cobalt and nickel and silicon, or a polycrystalline silicon. It may be a laminated structure with a thin film.
• FIG. 10D shows an example of the cross-sectional structure of the transistor formed by this procedure. Note that the procedure for forming the transistor is not limited to the procedure shown in this flowchart, and the number of wiring layers is not limited to two. Further, the MOS transistor may be used in a memory circuit such as a dynamic random access memory (DRAM) or a static random access memory (SRAM) or an arithmetic circuit.
• DRAM dynamic random access memory
• SRAM static random access memory
• the surface of the silicon substrate under a non-opening, for example, a GaN film, between the element isolation oxide films is substantially flattened by about 60 to about 85%. Therefore, the flat region on the surface of the silicon substrate 1 can be enlarged. Therefore, the integration degree of the MOS transistor can be improved, and the reliability can be improved.
• Example 5 will be described with reference to FIGS.
• the present embodiment is an embodiment of a method for manufacturing a flash memory provided with an oxide film for element isolation formed by the procedure according to the first to third embodiments. Members equivalent to those in Examples 1 to 4 ⁇ The same reference numerals are used for the procedures.
• FIGS. 12A to 12F are conceptual diagrams showing changes in the cross section of the silicon substrate (wafer) in each procedure of the flash memory manufacturing method according to the present embodiment
• FIG. 1 is a flowchart showing the manufacturing method of the present embodiment. See Figure 3.
• an oxide film 4B for element isolation is formed by any of the methods of Embodiments 1 to 3 (FIG. 12A). Thereafter, a tunnel oxide film 511 of a MOS transistor is formed on the surface of the silicon substrate 1 (FIG. 12B). Floating electrode 5 1 on this tunnel oxide film 5 1 1 For example, deposit a polycrystalline silicon thin film as 1 o and perform etching as an electrode
• FIG. 12C an insulating film 512 made of a silicon oxide film, a gay nitride film or a laminated structure film thereof is formed (FIG. 12D), and a control electrode 513 is formed thereon.
• a polycrystalline silicon thin film is formed (FIG. 12E :).
• the material of the floating electrode 5 10 or the control electrode 5 13 is not limited to polycrystalline silicon, but may be a high melting point metal material such as W or Ti, or a high melting point metal material, cobalt, or the like. It may be a silicide alloy made of nickel or the like and silicon, or a laminated structure film of these and a polycrystalline silicon thin film.
• FIG. 12F shows an example of a transistor cross-sectional structure formed by this procedure. Note that the procedure for forming the transistor is not limited to the procedure shown in this flowchart, and the number of wiring layers is not limited to two. Further, the electrode structure and the like constituting the flash memory are not limited to this embodiment.
• the flat region on the surface of the silicon substrate 1 can be enlarged. Therefore, there is an effect that the integration degree of the flash memory can be improved.
• the additional oxidation is performed after the removal of the silicon nitride film in the fifth procedure, so that a region having a uniform oxide film thickness can be greatly expanded. Therefore, the surface of the silicon substrate can be sufficiently flattened, and the integration of a semiconductor element, for example, a MOS transistor flash memory can be improved.
• the silicon substrate is removed by 1 O nm or more from the surface, so that a step when a transistor pattern or the like is later printed by using an exposure method can be reduced. it can.
• the polycrystalline silicon thin film or the polycrystalline silicon thin film pad Since the silicon nitride film is deposited on the silicon substrate via the oxide film, bird's beak growth on the substrate side in the third procedure can be relatively suppressed.

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• Manufacturing & Machinery (AREA)
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• Local Oxidation Of Silicon (AREA)
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Citations (5)

• 1995
  • 1995-05-08 JP JP7109585A patent/JPH08306678A/ja active Pending
• 1996
  • 1996-04-30 TW TW085105149A patent/TW326099B/zh active
  • 1996-05-01 WO PCT/JP1996/001193 patent/WO1996036073A1/ja not_active Application Discontinuation
  • 1996-05-01 KR KR1019970707841A patent/KR19990008315A/ko not_active Ceased
  • 1996-05-06 MY MYPI96001700A patent/MY132186A/en unknown
  • 1996-05-06 IN IN824CA1996 patent/IN187708B/en unknown

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