TW506058B - Method for profiling corner by chemical dry etching in shallow trench isolation process - Google Patents

Abstract

A method for profiling a corner by a chemical dry etching in a shallow trench isolation process comprises: after completion of a shallow trench etching, using a chemical dry etching method having a higher silicon nitride/silicon selectivity and an isotropic etching to push back the silicon nitride layer and expose the silicon corner from the surface of the silicon nitride layer; and using an isotropic etching having a higher silicon/silicon nitride selectivity to profile the silicon corner, thereby obtaining a shallow trench with profiled corner. The present invention can avoid the formation of wrap rounding in the corner of a shallow trench and the occurrence of electrical abnormalities and thus can facilitate following processes.

Description

Field of the Invention: The invention relates to an etching method in a semiconductor process, and particularly to a method for isolation in shallow trenches (ShallOw Trench :, 1 & 20%: =). A method for forming a rounded corner by forming a layer of nitrided stone. BACKGROUND OF THE INVENTION: In the advanced integrated circuit manufacturing process in which the power is advanced, the surface of the stone with a limited area can be used. ^ t; H ^ ^ # a ^ The MOS transistor which has reached hundreds of thousands, "The transistor on the integrated circuit between the electric body and the electric body is a complex transistor. A short circuit will occur. The field oxide layer (^ eif 'electrical / bulk isolation, to avoid active reg ^ d \) in the part is to isolate the opening and closing of the elementary sound §1〇nS ) 'Before the most commonly used field oxygen 〇fsnιΛΛΤΓ 0 dation, LOCOS was widely used, so in the 0.25 m process process there is a bird's beak effect and the field oxide layer refinement rf away from I', but due to LOC〇S, The Month of the Month is at 6, ^ 1 g 1 d oxide thinning as two [ΐ 'i 5 " m or less Components, it is no longer possible to use LOCOS for horse vulture insulation, and replaced it with a trench isolation insulation process. Compared with the L0C0S: Yali process, it has better anti-death bolts (Latch_up 'I process,! Τ insulation separation width' and magic shaw In addition to programming the channel of material / force'm, it has a better flat beak commonly used in the LOCOS insulation and isolation process. It becomes the mainstream of the insulation and isolation process in the semiconductor process. solve

Page 4 V. Description of the invention (2) Problems such as refinement of the field oxide layer caused by the π bird-song effect of θS-. First open the surface 4 = STI insulation isolation structure, the first is a substrate Shi Xi surface = oxide layer 'is deposited on it-a layer of nitrogen cut layer on this siliconized silicon layer to form a picture pull θ in the domain, and use Etching and drying output 出, 一, to define the area to be etched to avoid the formation of edges due to shallow pole trenches. Right: shallow trench structure. In order to solidify the process, the corners of σ have a shape close to a right angle, which leads to an increase in the follow-up. Therefore, the silicon corners in the shallow trench structure are combined into: The second method of the silicon corner and corner book will be re-formed to push back the nitride layer, and use /// such as wet silver engraving or oxidation to cut off the edges and edges of the surface. 'Reform

oxide) in shallow trenches, and then re-fed the South Density Plasma Oxide (HDP t. Uet ralcal clean) by repeated wet chemical cleaning such as removal of the nitrogen passivation layer, resulting in the formation of corners of the STI surface. The phenomenon of ap rounding (sag rounding) occurs—the sag rounding Γ 2: 1: causes the oxide layer to fail to cover the corners of the lake, which leads to the next step. During human thermal oxidation, this depression develops unevenly, and then produces Y-images at the edges of the STI. The thermal current subthreshold current neck-knot effect (d bl i 'e-breakd〇wn) and other electrical properties The situation of the south electric field and the generation of Wu Wei in advance makes it impossible for the semiconductor device to effectively exert its electrical characteristics. Therefore, the present invention is directed to the above-mentioned shortcomings, and #the method of making STI arc corners with the y-cut method is used to overcome the above-mentioned shortcomings. 560858 5. Description of the invention (3) Purpose and summary of the invention: The main purpose of the invention is to use a chemical dry etching method to etch the nitride nitride layer to push back the silicon top corner (top-coner), and then perform an etching step on the corner to remove the top corner of the shallow trench. Arcing to facilitate subsequent processes. Another object of the present invention is to provide a method for forming rounded corners of shallow trenches, so that after the subsequent isolation of shallow trenches, it is possible to avoid the phenomenon of wrap rounding at the corners of shallow trenches. To avoid the phenomenon of electrical abnormality of parasitic elements. Another object of the present invention is to provide a method for quickly forming arc-shaped corners in a shallow trench isolation process, which has the shortest processing time. Another aspect of the present invention is to learn the engraving of the lateral surname after the dryness of the nitrided stone layer. To achieve this, the first step is to pattern the photoresist structure. Then, the efficiency of the nitrogen reuse Shi Xi to push the square nitride Shi Xi is dry etched on a silicon substrate, in order to use the method of silicon nitride layer nitride Xi Xi, the method is used to push the phase layer back to 0 purpose. The formation of the photo-nitride stone sinking in the formation material is pushed backward. In terms of proposing a method using chemical dry etching technology to compare with other in-situ methods, the present invention has better The method for isolating the rounded corners in a shallow trench includes the following steps: depositing a silicon nitride layer, forming a barrier on the surface, and etching to form a shallow trench with a relatively high chemical resistance to Shi Xi. Etch 'to expose the stone corners of the surface of the shallow trench. Higher chemical dry etching rounds silicon corners

surface

Page 6

10 silicon substrate 1 2 Shi Xibianxiao 14 circular arc corner 20 pad oxide layer 30 silicon nitride layer 40 photoresist layer 42 etched window 50 shallow trenches In the isolation process, chemical dry etching is used to push back silicon to increase the arc angle. The first figure to the figure depict the process and steps of this etching method. As shown in the first figure, a semiconductor silicon substrate 10 is provided, on which the basic components of the previous process have been completed. To simplify the overall pattern structure, basic components such as MOS transistor structures located in the semiconductor silicon substrate 10 are temporarily provided. Ignore it. On the surface of the semiconductor silicon substrate 10, genus 058 is formed by thermal oxidation deposition. 5. Description of the invention (5) A pad oxide layer 20, usually a silicon dioxide layer, is flattened. A silicon nitride layer is deposited on the layer 20. The stress between the nitride layer 30 and the substrate 10 is very large, and the oxide layer 20 is required as a buffer layer therebetween to eliminate the silicon substrate.

The stress of stone ^ 30. Next, a lithography process is performed, and nitriding; H ": a layer of photoresist layer, 1 is formed using a yellow light development etching technique-figure /, photoresist layer 40, which is an etching window 42 with an appropriate size, The size and position of the shallow trenches to be etched are determined according to the definition. After definition, the shallow trenches are etched using the existing etching technology to form the shallow trenches 50, and the pattern is shown in the second figure. The photoresist layer 40 is changed to go to: the nitride stone layer 30 exposed from the engraved window 42 and the pad emulsified layer 20 under it, until a portion of the silicon substrate 10 is etched to form a shallow layer.

After that, the patterned photoresist 40 is removed, as shown in the third figure. The gas used for etching is carbon tetrafluoride and oxygen (CF: the remaining step of the stage; among them, the shallow trench 50 is formed by the dry etching technology of Anisotropic), It is connected to a 90 ° right angle profile (pr0fUe). /. It is close to the second stage of the etching step. First, the silicon nitride is etched using a relatively high etching rate of silicon and is an isotropic etching. The edges of the layer 30 and the samarium oxide layer 20, J = neodymium, quasi-nitride layer and samarium oxide layer 20 are pushed backwards, and the silicon corner i 2 with a vertical shape on the surface of the radon trench 50 is " The gas used in the layer is carbon tetraoxide, oxygen, and nitrogen (cC), and the etching rate selection ratio of silicon to silicon is greater than 1 (SiN / Si2 > 2

As shown in the fifth picture on page 8 of Lihou, the Tiantian visit to Jinjin is localized, and the engraved wind is equal to the engraved wind '= 2 The fossil eve's silver engraving rate is selected to be rounded than the straight shape, and you can: ίί: The angle of the vertical arc on the surface of the silicon corner 12 is 1 4; and the expected γ is obtained at the top corner of the Jimugou 50 (Si / SiN > J) ° ^ 0 The silicon etching rate selection ratio is greater than 1 (such as the deposition process / two :: after the corner of the groove arc, it is beneficial to the subsequent process f, which can avoid the dagger :: angle; the trench isolation process is completed ^; elephant 'to avoid parasitic elements : = = ;: nding, the present invention makes use of the phenomenon of chemical 皋 smoke drill ^ electrical different hanging. Then compared to the conventional wet etching or oxidation of two square η: silicon layer etching backwards, Shi Xi layer backwards ancient; _ 品 冋 -ren (in_situ) chemical dry etching method to push back the nitride: layer and t, the present invention has better side effect. The present invention needs to be formed in addition to the application in the shallow trench semiconductor process The method of solving the problem of the circular arc is clear, and the detailed process will not be described in detail. In addition to the isolation structure, the etching process of other corners can also be used in this publication. Therefore, the embodiments described above are only for explaining the technical ideas and characteristics of the present invention, and its purpose is to enable those skilled in the art to understand the inner valley of the present invention and implement it accordingly. The limitation of the scope of the patent of the present invention, that is, all equal changes or modifications made in accordance with the spirit disclosed by the present invention, should still be covered by the scope of the patent of the present invention. 506058 Brief description of the drawings The figure is a schematic diagram of the continuous steps of forming a shallow trench and its arc corners according to the present invention. Page 10

Claims (1)

506058 506058 1. A method for forming a corner in a shallow trench isolation process, which comprises the following steps: "Drying a nitrided layer on a substrate by forming a circular arc edge with chemical dry etching; forming a silicon nitride layer on the surface of said silicon nitride layer; The patterning uses the patterned photoresist as a mask, and uses a selection ratio of the nitride to the substrate to form a shallow trench structure. The layer is pushed backward to expose the shallow trench surface; Nitride stone uses the substrate to select and separate the nitride stone and the arc to obtain the corners of the arc. ^ Learn the dry etching method to round the corners. 2 · As described in the first patent application, there is a pad oxide layer between the square silicon layers. ’/, The substrate and the method described in item 1 of the patent scope, wherein the gas used to etch the shallow trench is carbon tetrafluoride and tritium gas (M "%). 4. The method according to item 丨 of the scope of patent application, wherein the etching rate selection ratio of the siliconized silicon material is greater than 1. -5. The method according to item 1 of the scope of patent application, wherein the gases used to etch the nitride layer are carbon tetrafluoride, oxygen, and nitrogen (CF4 / 〇2 / N2). 6 · The method according to item 1 of the scope of patent application, wherein the ratio of the substrate to Shi Xi's remaining cut ratio is greater than 1. 7 · A method for forming arc-shaped corners by chemical dry etching, repeating the following steps: ',', depositing a silicon nitride layer on a one-second substrate; forming / patterning light on the surface of the silicon nitride layer The patterned photoresist is used as a mask to perform etching to form a patterned pattern. The patent-application layer uses a chemical dry etching method with a high selectivity ratio of H and G to silicon. The nitrogenization layer is pushed backward to expose the silicon corners on the surface; and the chemical dry etching method with high selection ratio of silicon nitride by Shi Xi to the silicon corners 8: daggers: to obtain circular arc corners. The method described in item 7 of the scope of patent application, wherein a pad oxide layer is further formed between the substrate and the nitrogen g second layer. The method as described in item 7 of the scope of patent application, wherein the gas used to etch the patterned emulsified second layer is carbon tetrafluoride and oxygen (CF4 / 〇2). The method described above, wherein the selectivity ratio of the nitrogen etching rate is greater than one. For Shi Xi U · The method described in item 7 of the scope of the patent application, the direct etch 3 uses the gaseous carbon, oxygen, and nitrogen ⑽ 4 / V Γ Γ Fossil Xi 2 · As the scope of the patent application The method described in item 7, straight 2). The remaining ratio selection ratio is greater than 1. /, H Xi pour silicon nitride m p. 12