TW200412644A - Method of fabricating shallow trench isolation structure - Google Patents

Abstract

A method of fabricating a shallow trench isolation (STI) structure. A substrate is provided and then a pad oxide layer, a mask layer and a first trench are sequentially formed on the substrate. An insulation layer is formed inside the first trench and over the substrate. The insulation layer has a second trench in a location above the first trench. Thereafter, a conformal cap layer is formed over the insulation layer. The cap layer has a third trench in a location above the second trench. A reverse mask is formed over the cap layer covering the third trench. The cap layer and the insulation layer outside the reverse mask are removed to expose the upper surface of the mask layer. The reverse mask is removed and then the residual insulation layer outside the remaining cap layer and the trench are moved to expose the upper surface of the mask layer. Finally, the mask layer and the pad oxide layer are removed.

Description

200412644 V. Description of the invention (1) The technology to which the invention belongs The invention relates to a method for manufacturing an electrical insulation (E 1 ectrica 1 1 yi nsu 1 at i ng) structure, and in particular to a shallow trench isolation (Shallow Trench Isolation (STI) structure manufacturing method. In the prior art, with the increasing accumulation of semiconductor elements, the design rules for elements have become smaller. 'In the process below 0. 18 microns, the electrical insulation structure in the memory cell', such as a silicon oxide insulation layer, is no longer available. Local Oxidation (LOCOS) is used for manufacturing. One of the most widely used methods today is to use a method of forming a shallow trench isolation structure to manufacture an electrically insulating structure. Generally speaking. In the process of manufacturing a shallow trench isolation structure, a high density electrochemical polymerized chemical vapor deposition (HDPCVD) method is used to fill the silicon oxide into the trenches due to the South Density Plasma Chemical Vapor Deposition method. It has the problem of poor uniform coverage (Conformity). Therefore, excess silicon oxide must be filled into the grooves, and then the silicon oxide layer must be ground back to an appropriate thickness by chemical mechanical polishing (CMP) method. However, the distribution of trenches on the substrate will have different dense and dense patterns depending on the actual situation. When it is regrinded by chemical mechanical polishing, it will be removed in areas with high density due to the effect of pattern density. The speed is faster, which in turn causes the Dishing effect in this area to be more serious than in areas with low density, which seriously affects the uniformity of components. mountain

200412644 V. Description of the invention (2) "The conventional method uses a process that uses a reverse cover (difficult to use Reverse). _ M W㈣M 'Please refer to item}. In the first figure, only part of the picture is shown. ^ # 々 A high-density plasma chemical vapor deposition method is used to form the Λ-deposited layer 108 on a substrate 100 # having a pad oxide layer 〇2, a cover layer 〇04 layer, and a two-layered glass 06, and then A photoresist layer is formed on the silicon oxide layer 108. The photoresist layer is used to cover the area i or ′ of the pattern with dense photoresist layer and is formed over the trench m in the area with low pattern density. Reversing the mask Π 2. The photoresist layer and the reversing mask 112 are etched to expose the surface of the mask layer 104 by contact oxidation. After that, the photoresist layer and the mask 112 are rotated to make the original pattern density. The low area is reversed to the area i or between the pattern densities, and then the silicon oxide layer is removed by chemical mechanical polishing to expose the nitrogen == surface. Its | 'remove the pure cut layer and pad the oxide layer to form a' trench isolation structure. However, as the components continue to shrink, the above-mentioned manufacturing method of the shallow trench isolation structure by the inversion mask method is described above. In the process, the margin of the process of forming the reversal mask is relatively narrow, and it is easy to cause misalignment. As a result, the reversal mask 112 is formed on the hypotenuse in the trench 110, which further causes a depression (reCeSS). The generation of 114. In the subsequent etching of the oxide oxide layer 108 with the mask layer 104 as an etch stop layer, 'the depression 114 may etch through the mask layer 104 and continue to be engraved to the next name', thereby causing a surname. The two phenomena of over etching cause damage to the silicon substrate. On the other hand, in the process of reversing the mask, the reversing mask system must be designed to exceed the two sides of the trench opening to ensure that the above due to the depression guide

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5. Description of the invention (3) The situation of over-etching the silicon substrate will not occur. However, with the shrinking of components, the distance between trenches has also decreased, and the width of the inversion masks covering the trenches is larger than the width of the trenches. Therefore, the distance between the inversion masks has been further reduced. When the pitch is reduced to be smaller than the critical size of the exposure, the outline of the space between the inversion masks cannot be correctly transferred by the exposure process, so that a correct inversion mask pattern cannot be formed. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a shallow trench isolation structure, which can improve the process margin of the yellow light process for reversing the mask. Another object of the present invention is to provide a method for manufacturing a shallow trench isolation structure, which can avoid damage to the silicon substrate due to over-etching when the insulating layer is etched. The invention provides a method for manufacturing a shallow trench isolation structure. This method provides a substrate, and a pad oxide layer, a mask layer, and a first trench have been sequentially formed on the substrate, and then formed in the first trench and on the substrate. The insulating layer fills the first trench, and the insulating layer above the first trench has a second trench. Then, a conformal cap layer is formed on the insulating layer, and the cap layer above the second trench has a third trench, wherein the width of the third trench is smaller than the width of the second trench, and then forming an inverse on the cap layer. Turn the mask to cover the third trench, and then remove the cap layer and the insulation layer outside the inversion mask to expose the surface of the mask layer, and then remove the inversion mask. Thereafter, the remaining cap layer and the remaining insulating layer outside the trench are removed to expose the surface of the mask layer, and then the mask layer and the hafnium oxide layer are removed. From the above, it is known that since a conformal cap is formed on the insulating layer

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V. Description of the invention (4) layer, so that the width of the trench on the insulating layer can be reduced by the trench formed by the cap layer, so that the process margin for forming the inversion mask on the trench can be widened, and The turn screen can completely cover the ditch to avoid the depression at the junction of the turn screen and the ditch. In addition, since the formed reversal mask does not generate a depression at the interface with the trench, the etching of the insulating layer can be stopped in the mask layer during the etching process of the insulating layer, and it will not be caused by the depression. Causes over-etching and damages the substrate. Moreover, because a thin, slightly conformal cap layer is formed on the insulating layer, the narrower gap between the trenches on the insulating layer is formed. The width of the gap between the trenches can be formed by the trench formed by the cap layer. Enlargement, and appropriate adjustment of the width of the reversal masks by matching the trenches on the cap layer can widen the gap between the reversal masks formed on the trenches, so as to prevent the gap between the reversal masks from being too small and Situations where exposure is not correct. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings for detailed description as follows: Embodiments: FIG. 2A to 2G The drawing shows a schematic cross-sectional view of a manufacturing process of a shallow trench isolation structure according to a preferred embodiment of the present invention. First, referring to FIG. 2A, a semiconductor substrate 200 is provided, and a pad oxide layer 202 and a mask layer 204 are formed on the substrate 200 in this order. Among them, a method for forming the pad-forming layer 202 is, for example, a thermal oxidation method. The material of the cover layer 204 is, for example, silicon nitride, and a method of forming the cover layer 204 is, for example, using

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5. Description of the invention (5) A chemical vapor deposition (CVD) method is used to form a silicon nitride layer on the pad oxide layer 202. Next, a portion of the mask layer 204, the pad oxide layer 202, and the substrate 200 are removed to form a trench 206. The method for forming the trenches 206 is, for example, forming a patterned photoresist layer (not shown) on the mask layer 204. The photoresist layer is used as the mask ’to remove the mask layer 204, the pad oxide layer 102, and a portion of the substrate 200 using an anisotropic coin-cut method to form a trench 206. Thereafter, a plutonium layer 208 is formed on the inner surface of the trench 206. The method of forming the hafnium layer 208 is, for example, forming a silicon oxide layer by a thermal oxidation method. Next, referring to FIG. 2B, an insulating layer 2 10 is formed on the substrate 200 to fill the trench 2 06 and cover the entire substrate 2 0. The material of the insulating layer 2 1 0 is, for example, silicon oxide. The method of this insulating layer is, for example, using a high density plasma chemical vapor deposition (HDPCVD) method, and using silane (SiH4), oxygen, argon (Ar) as a reaction gas source on the substrate 20 0 A silicon oxide layer is formed on it. Due to the poor uniformity of the high-density plasma chemical vapor deposition method, the trench 212 is formed by the insulating layer 210 above the trench 206. Next, referring to FIG. 2C, a thin cap layer 214 is formed on the insulating layer 210 to completely cover the insulating layer 210, and the trench 212 on the insulating layer 210 becomes the cap layer 214. The trench 216, wherein the width of the trench 216 will be smaller than the width of the trench 212. The material of the capping layer 214 is, for example, silicon dioxide. A method for forming the capping layer 214 is, for example, using a chemical vapor deposition method to deposit a slightly conformal oxide layer on the insulating layer 2 10.

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5. Description of the invention (6) In the step of FIG. 2C above, the deposition system of the capping layer 2 1 4 can use the same deposition reaction chamber as the deposited insulating layer 2 1 0, which is, for example, a high-density plasma chemistry In the vapor deposition method, the RF bias applied to the wafer is reduced or even turned off, that is, a slightly conformal cap layer 2 1 4 can be formed on the insulating layer 2 10. However, the present invention is not limited to using the same deposition machine, and another deposition machine may be used to form the capping layer 2 1 4. Moreover, in addition to using the deposition machine table, the cap layer 2 1 4 can also be formed by using a hot furnace tube. Next, referring to FIG. 2D, a patterned mask layer 218 is formed on the cap layer 2 1 4 as a reverse mask, and the width of the mask layer 218 is at least larger than the width of the upper portion of the trench 216 to completely cover the trench 216. . The material of the cover layer 2 1 8 is, for example, a photoresist. The method for forming the cover layer 2 1 8 is, for example, forming a photoresist layer (not shown) on the cap layer 2 1 4 and then exposing and developing the photoresist layer. A patterned mask layer 218 is formed. In FIG. 2C, the trench 2 1 6 formed by forming the capping layer 214 can reduce the width of the original trench 2 1 2, so that the process margin of the mask layer 2 1 8 is widened, thereby making the mask The layer 2 1 8 can easily cover the trench 216 without causing a depression. Furthermore, the trenches 2 1 6 formed by forming the cap layer 2 1 4 can reduce the width of the original trenches 2 1 2 and also increase the spacing between the trenches 2 1 6. Therefore, in the trenches 2 1 The area with a dense pattern of 2 (not shown) can be formed by forming the trenches 2 1 6 to increase the spacing between the trenches and cooperate with the trenches 216 to appropriately adjust the size of the inversion mask, thereby avoiding the inversion mask. The space between the screens is too small to form a pattern correctly.

9795twf.ptd Page 15 200412644 V. Description of the invention (7) Then 'please refer to Figure 2E' to remove the cover layer 2 1 8 and the insulating layer 210 outside the covered area to expose the cover layer 2. 4 surfaces to form a capping layer 2 1 9 and an insulating layer 2 2 0. The method is, for example, to use a mask 2 1 g as an etching mask, and use a mask layer 2 0 4 as an etching stop layer, and remove the mask layer 2 1 8 overlying area by an anisotropic engraving method. The outer capping layer 2 1 & and the insulating layer 210. Since no depression is generated at the boundary between the reversal mask 218 and the trench 216, the etching system of the insulating layer 220 can stop at the mask layer 204 without over-etching and damaging the substrate. Next, referring to FIG. 2F, the cover layer 218 'on the cap layer 2 1 9 is removed, and then the insulating layer mo other than the cap layer 219 and the trench 20 is removed to expose the cover layer 2 0 4 So as to form a flat insulating packing 222. The method for removing the cap layer 219 and part of the insulating layer 210 is, for example, using the mask layer 204 as a polishing termination layer, and removing the cap layer 2 1 9 and the trench 2 0 by chemical mechanical polishing. Insulation layer 2 2 0. Next, referring to FIG. 2G, the mask layer 204 and the pad oxidation layer 202 are sequentially removed to form a shallow trench isolation structure. The method of removing the mask layer 204 is, for example, a wet etching method using hot phosphoric acid etching. A method for removing the pad oxide layer 202 is, for example, a wet etching method by etching with hydrofluoric acid (HF). According to the statement, "the present invention has at least the following advantages: 1 · Since the present invention forms a thin conformal thin cap layer on the insulating layer", the trench width on the insulating layer can be determined by the cap layer. The formation of the trench is reduced, thus widening the margin of the process of forming a reversal mask on the trench. Even if misalignment occurs, the reversal mask can completely cover the trench and can be avoided during reversal. Depression at the junction of the curtain and the trench

9795twf.ptd Page 16 200412644 V. Description of Invention (8). 2 · Because the inversion mask formed by the present invention does not generate a depression at the interface with the trench, the insulation layer can stop the insulation layer of all parts to be removed during the etching process of the insulation layer. , Will not hurt the substrate because of the over-etching phenomenon caused by the depression. 3. The process of the present invention is simple and easy to implement, and is suitable for the current insulation film deposition process in the shallow trench isolation structure. Therefore, it can effectively increase the yellow light reversing process without increasing the difficulty of the process. Process margin. 4. Since the present invention is to form a thin conformal thin cap layer on the insulating layer, so that in the area with a narrow gap between the trenches on the insulating layer, the width of the gap between the trenches can be formed by the cap layer. The trench is enlarged, and the width of the reversing masks is adjusted appropriately by matching the trenches on the cap layer, so that the gap between the reversing masks formed on the trench can be widened, so that the gap between the reversing masks can be avoided. Too small to properly expose. Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes and retouch without departing from the spirit and scope of the present invention. The scope of protection of the invention shall be determined by the scope of the attached patent application.

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Brief Description of the Drawings Figure 1 shows a schematic cross-sectional view of a conventional method for forming a reversal mask on an insulating layer in a shallow trench isolation structure. Figures 2A to 2G are cross-sectional schematic diagrams illustrating the manufacturing process of a shallow trench isolation structure in accordance with a preferred embodiment of the present invention. Figures are labeled and explained: 1 00, 2 0 0: substrates 102, 202: Pad oxide layers 104, 1 12, 204, 218: mask layer 106 ^ 1 10 ^ 2 0 6 ^ 212 ^ 216: trench 1 0 8 · silicon oxide layer 1 1 4: depression 2 0 8: 榇 layer 2 1 4, 2 1 9: Cap layer 2 2 2: Insulation packing

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Claims (1)

200412644 6. Scope of Patent Application 1. A method for manufacturing a shallow trench isolation structure, characterized in that: a substrate is provided on which a pad oxide layer, a cover layer and a first trench have been sequentially formed; Forming an insulating layer in a trench and the substrate to fill the first trench, and the insulating layer above the first trench has a second trench; and forming a conformal cap layer on the insulating layer, And the cap layer above the second trench has a third trench; a reverse cover is formed on the cap layer to cover the third trench; and the cap outside the reverse cover is removed Layer and the insulating layer to expose the surface of the mask layer; removing the inversion mask; removing the remaining cap layer and the remaining insulating layer outside the trench until the surface of the mask layer is exposed, And removing the mask layer and the hafnium oxide layer. 2. The method for manufacturing a shallow trench isolation structure as described in item 1 of the scope of patent application, wherein the material of the capping layer includes silicon oxide. 3. The method for manufacturing a shallow trench isolation structure as described in item 1 of the scope of the patent application, characterized in that the method of forming the capping layer includes a chemical vapor deposition method. 4. The method for manufacturing a shallow trench isolation structure as described in item 1 of the scope of patent application, characterized in that the method of forming the insulating layer includes forming a silicon oxide layer by a high-density chemical vapor deposition method. 5. The system of shallow trench isolation structure as described in item 1 of the scope of patent application 9795twf.ptd Page 19 200412644 VI. Scope of Patent Application The manufacturing method is characterized in that the cap layer and the insulating layer are deposited in the same reaction chamber. 6. The method for manufacturing a shallow trench isolation structure as described in item 1 of the scope of the patent application, characterized in that the cap layer and the insulating layer are formed by depositing in different reaction chambers. 7. The method for manufacturing a shallow trench isolation structure as described in item 1 of the scope of the patent application, characterized in that the material of the inversion cover includes a photoresist material. 8. The method for manufacturing a shallow trench isolation structure as described in item 1 of the scope of the patent application, which is characterized by removing the remaining cap layer and the remaining insulating layer outside the trench until the surface of the cover layer is exposed The methods include chemical mechanical grinding. 9. The method for manufacturing a shallow trench isolation structure as described in item 1 of the scope of the patent application, characterized in that, before the step of forming the insulation layer in the trench and the substrate to fill the trench, it is further inside the trench. The surface forms a liner. 10—A method for manufacturing a shallow trench isolation structure, characterized in that: a substrate is provided on which a pad oxide layer, a cover layer and a first trench have been sequentially formed; and An insulating layer is formed on the substrate to fill the first trench, and the insulating layer above the first trench has a second trench; a capping layer is formed on the insulating layer, and the second trench is above the second trench The capping layer has a third trench, wherein the trench width of the third trench is smaller than the trench width of the second trench; 9795twf.ptd Page 20 200412644 Sixth, the scope of the patent application is to form an inversion cover on the cap layer to cover the third trench; remove the cap layer and the insulation layer outside the inversion cover to Expose the surface of the cover layer; remove the reverse cover; remove the remaining cap layer and the remaining insulating layer outside the trench until the surface of the cover layer is exposed; and remove the cover Layer and the plutonium oxide layer. 1 1. The method for manufacturing a shallow trench isolation structure as described in item 10 of the scope of patent application, wherein the material of the cap layer includes silicon oxide. 1 2. The method for manufacturing a shallow trench isolation structure as described in item 10 of the scope of patent application, characterized in that the method for forming the capping layer includes a chemical vapor deposition method. 1 3. The method for manufacturing a shallow trench isolation structure as described in item 10 of the scope of patent application, characterized in that the method for forming the insulating layer includes forming a monoxide layer by a high-density chemical vapor deposition method. 1 4. The method for manufacturing a shallow trench isolation structure as described in item 10 of the scope of the patent application, characterized in that the cap layer and the insulating layer are deposited and formed in the same reaction chamber. 15. The method for manufacturing a shallow trench isolation structure as described in item 10 of the scope of the patent application, wherein the cap layer and the insulating layer are deposited in different reaction chambers. 16. The method for manufacturing a shallow trench isolation structure as described in item 10 of the scope of the patent application, wherein the material of the inversion cover includes a photoresist material. 1 7. The shallow trench isolation structure described in item 10 of the scope of patent application 9795twf.ptd Page 21 200412644 VI. Patent application manufacturing method, which is characterized by removing the remaining cap layer and the remaining insulating layer outside the trench until the method of exposing the surface of the cover layer includes chemical machinery Grinding method. 1 8. The method for manufacturing a shallow trench isolation structure as described in item 10 of the scope of patent application, characterized in that the step of forming the insulating layer in the trench and the substrate to fill the trench is performed before the step of filling the trench. The inner surface forms a lining layer. 9795twf.pta Page 22