TWI302343B - Method for preparing a deep trench - Google Patents

Description

1302343 IX. DESCRIPTION OF THE INVENTION: TECHNICAL FIELD The present invention relates to a method for preparing a deep trench, and more particularly to a deep trench having a large internal surface area and thus applicable to a high-concentration dynamic random access memory. Preparation method. [Prior Art] Capacitors of the dynamic random access memory can be classified into a stacked type and a deep trench type. The stacked capacitor is formed on the surface of the germanium substrate, and the deep trench capacitor is formed inside the substrate. In recent years, the degree of accumulation of dynamic random access memory has rapidly increased with the innovation of semiconductor process technology, and the size of transistors and capacitors has to be reduced in order to achieve high integration. Since the capacitance of the capacitor is proportional to the surface area of the electrode plate, reducing the size of the capacitor will result in a decrease in the capacitance value, which is not conducive to the correct interpretation of the stored data. Therefore, researchers have developed bottle-shaped deep trench capacitors that increase the capacitance of capacitors by increasing the internal surface area of the deep trenches in the germanium substrate to increase the surface area of the electrode plates that are subsequently formed in the deep trenches. 1 to 5 illustrate a method of preparing a roughened deep trench 1 by conventional techniques. Two adjacent trenches 16 are formed in the substrate 12. n, forming an electrode 18 on the lower outer edge of the trench 16, and using thermal oxidation (or chemical rolling deposition) with anisotropic etching to form an annular oxide layer 2 over the trench 16 Half inner edge surface. /Test Figure 2, Low Pressure Chemical Vapor Deposition Process, Thermal Oxidation Process or Thermal ""The formation of a mask layer with a thickness of 0.3-10 nm (masking)

101S73.DOC P26164 101873 004^8^^7 -6- 1302343 1(d)) 22 is on the lower electrode 18 and the annular oxide layer 2〇. The mask layer may be composed of a cerium or a nitrite, and after covering the inner wall of the lower inner edge of the trench 16, a plurality of nanocrystals are formed by a low pressure chemical vapor deposition process. 24 is a partial surface of the mask layer 22, as shown in FIG. The test garden uses a sulphuric acid or hydrofluoric acid-containing engraving solution to perform a wet etching process to selectively etch the mask layer 22 not covered by the nanocrystal wafer 24, since the beta mask layer 22 It is composed of oxidation 9 or nitridation, and the nanocrystal is composed of ruthenium, so the etchant containing phosphoric acid is selectively masked by the nanocrystal 矽24 as a worm mask. The wafer 24 covers the mask layer 22, but retains the nanocrystal grains 24 and the mask layer 22 therebelow. Figure 5 is a method of selectively removing the nanocrystal grains 24 and etching the inner walls of the trenches 16 not covered by the mask layer 22 by using a residual solution of hydrofluoric acid and nitric acid to form a moisture residue. A plurality of microchannels 26 are provided. Thereafter, the mask layer 22 is removed by hydrofluoric acid or phosphoric acid to form the roughened deep trench. The roughened deep trench 1 has a large internal surface area, which helps to increase the capacitance of the subsequently formed deep trench capacitor. Since the inner wall of the trench 16 and the nanocrystal grain 24 are composed of tantalum, the mask layer 22 is composed of tantalum oxide or tantalum nitride. Therefore, the residual layer of hydrofluoric acid and nitric acid may be used for the mask layer. 22 is a pen for money; a cover is selectively engraved to form the deep saccharified deep trench 10 〇 As described above, conventional techniques utilize a poorly flowing phosphoric acid to etch a mask on the lower half of the trench 16 Layer 22. However, as the aperture of the trench 16 is reduced, phosphoric acid is not easily transported to the lower half of the trench 16, resulting in the wet etching.

I01873.DOC P26164 101873 〇〇4.ς8ϋΤ7 1302343 . The etch rate of 胄' is not good. That is, the etching rate of the wet etching process is not effectively increased by the reduced aperture and the depth of growth of the trench 16. • [Summary of the Invention] The main purpose of this month is to provide a method for preparing deep trenches with a large internal surface area and thus can be applied to a high-concentration dynamic random access memory (DRAM). The residual liquid removes the nitrogen-containing layer in the lower half of the bead ditch, thereby solving the problem that the conventional surname is not easily transported to the lower half of the deep trench. In order to achieve the above object, the present invention discloses a method for preparing a deep trench, wherein 匕3 forms at least one trench in a substrate to form a nitrogen-containing layer on the inner wall of the trench to form a plurality of partial surfaces covering the nitrogen-containing layer. The crystal grains form a phosphorus-containing oxide layer on the surface of the nitrogen-containing layer and convert the phosphorus-containing oxide layer into an etching solution to remove the nitrogen-containing layer not covered by the crystal grains. The nitrogen-containing layer may be a tantalum nitride layer, and the phosphorus-containing oxide layer may be a phosphorous glass layer φ (PSG) or a borophosphon glass layer (BpsG). The method for converting the phosphorus-containing oxide layer into a rice engraving liquid can be placed in a spa atmosphere between a temperature range of 7 〇〇 1 〇〇〇 c > c, the phosphorus-containing oxide layer and water vapor The reaction produces phosphoric acid which etches the nitrogen containing layer. Thereafter, the phosphorus-containing oxide layer in the trench is removed by performing a wet etching process using diluted hydrofluoric acid or buffered hydrofluoric acid. Then, another wet etching process is performed by using an etching solution containing ammonia water, wherein the ammonia water selectively etches only the germanium without etching the tantalum nitride, so the wet etching process only removes the crystal grains on the nitrogen-containing layer and remains unfinished. The inner wall of the trench covered by the tantalum nitride, forming a

101873.DOC P26164 101873 1302343 The inner wall of the concave and convex surface, which increases the internal surface area of the deep trench. Conventional techniques must transport a poorly flowing phosphoric acid etchant from the opening of the trench to the lower half of the trench to etch a layer of nitride in the lower half of the trench' such that its (four) rate is limited by the trench The size of the aperture. In contrast, in this month, the nitrogen-containing layer on the inner wall of the trench is removed by the reaction of the oxide layer containing the oxide layer in the trench and the water vapor, and the water vapor is used. The transport of the H-channel to the τ half is not limited by the aperture of the ditch. The present invention can effectively solve the problems faced by the prior art due to the reduction of the aperture of the ditch. [Embodiment] Figs. 6 to 11 illustrate a method of preparing a rough-slit deep trench without the present invention. First, two trenches 46 are formed in the substrate 42. In general, a plurality of trenches 46 are typically formed on the substrate 42. Figures 6 through n are merely illustrative. Thereafter, a lower electrode 48 is formed on the lower outer edge of the trench 46, and is anisotropically etched by thermal oxidation (or gas phase/integration) to form an annular oxide layer 44 in the trench 46. Upper semi-inner edge surface. Referring to FIG. 7, a nitrogen-containing layer 52 is formed on the surface of the substrate 42 and the inner wall of the trench 46 by a low pressure chemical vapor deposition process. Thereafter, a plurality of crystal grains 54' are formed which cover a partial surface of the nitrogen-containing layer 52 as shown in FIG. The crystal grains 54 may be polycrystalline crystals/grains having a size range of 15 to 3 G between nanometers, for example, hemi-spherical grains (HSG) formed by a low pressure chemical vapor deposition process. An oxide-containing layer is formed on the surface of the gas-containing layer 52 by a low-pressure chemical vapor deposition process. The disk-containing oxide layer 56 covers the nitrogen-containing layer 52.

IOI 873.DOC P26164 101873 004 <=; 8^^^7 1302343 and the die 54. Preferably, the nitrogen-containing layer 52 may be a tantalum nitride layer, and the phosphorus-containing oxide layer 56 may be a borophosphophosphorus glass layer or a phosphorous-phosphorus glass layer. Thereafter, the phosphorus-containing oxide layer 56 is converted into an etchant to selectively remove the nitrogen-containing layer 52 directly in contact with the phosphorus-containing oxide layer 56, that is, the nitrogen-containing layer 52 not covered by the crystal grains 54 is removed. Further, a wet etching process is performed by diluting hydrofluoric acid or buffered hydrofluoric acid to remove the phosphorus-containing oxide layer 5 6 which is not converted into an etching liquid, as shown in FIG. The method for converting the phosphorus-containing oxide layer 56 into an etching solution may be to place the substrate 42 in a water vapor environment having a temperature between 70 〇 and 1 〇〇〇〇c, and the phosphorus-containing oxide layer 56 and water. The vapor reaction produces phosphoric acid with the die 54 as an etch mask, etching the nitrogen-containing layer 52 that is not covered by the die 54, and retaining the die 54 and the nitrogen-containing layer 52 that is covered. Then, using a etchant containing ammonia, the nitrogen-containing layer 52 covered by the die 54 is subjected to a wet etching process for etching the trench, and the inner wall of the trench is etched to form a plurality of microchannels 58. Thereafter, The nitrogen-containing layer 52 is removed to form the roughened deep trench 4〇, as shown in FIG. 。. Since the ammonia water selectively etches only the germanium and does not etch the tantalum nitride, the wet etching process removes only the gas-bearing layer. a polycrystalline germanium grain 54 on 52 and an inner wall of the trench 46 not covered by the nitrogen-containing layer 52 to form an inner wall having a concave-convex surface. The inner wall of the trench having a concave-convex surface serves as an electrode of a capacitor, and the addition The internal surface area of the rough slit trench 40 can increase the capacitance value of the capacitor. It is known in the art to transport an etchant having poor fluidity from the opening of the trench to the lower half of the trench to be etched in the lower half of the trench. The tantalum nitride layer, and thus its I insect engraving rate is limited by the pore size of the trench.

I01873.DOC P26164 101873 004585337 -10- I3〇2343 The use of a phosphoric acid oxide layer formed by the reaction of a phosphorus-containing oxide layer in the trench with water vapor to remove the nitrogen-containing layer on the inner wall of the trench, and the water vapor is removed from the The opening of the opening of the trench to the lower half is not limited by the size of the aperture of the trench, so the present invention can effectively solve the problems faced by the prior art due to the reduction of the aperture of the trench. In other words, the present invention only needs to place the substrate in a gas phase environment (for example, in a water vapor environment), in which the disk containing oxide layer in the trench can be converted into an etchable nitrogen-containing layer. Layer etchant. Therefore, the present invention does not need to transport the etchant of the nitrogen-containing layer from the opening of the trench to the bottom of the trench, and thus can be applied to a high-concentration dynamic random access memory having a trench having a small opening. The technical contents and technical features of the present invention have been disclosed as above, and those skilled in the art can still make various substitutions and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is not to be construed as limited by the scope of BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 5 illustrate a method of preparing a roughened deep trench by a conventional technique, and/or FIG. 6 to FIG. 11 illustrate a method of preparing a roughened trench of the present invention. [Main component symbol description] 10 Roughening deep trench 12 Substrate 16 Ditch 18 Lower electrode 20 Annular oxide layer 22 Mask layer 24 Nano grain 26 Micro trench

IOI873.DOC Ρ26164 101873 -11 - 1302343 40 Crude saccharification ditch 42 Substrate 44 Annular oxide layer 46 Ditch 48 Lower electrode 52 Nitrogen-containing layer 54 Grain 56 Filled with oxide layer 58 Microchannel

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Claims (1)

1302343' X. Patent application scope: ι A method for preparing a deep ditch • Forming at least one ditch in a patent application No. 094121824 to apply for a patent garden replacement (June 1997) b [Man] Original 'includes the following steps Forming a nitrogen-containing layer on the inner wall of the trench; forming a plurality of crystal grains covering a partial surface of the nitrogen-containing layer, forming a phosphorus-containing oxide layer on the nitrogen-containing layer and surfaces of the crystal grains And partially converting the phosphorus-containing oxide layer into an etching solution to remove the nitrogen-containing layer not covered by the crystal grains. % 2. The method for preparing a deep trench according to claim 1, wherein the crystallite is a polycrystalline sprite. 3. The method of preparing a deep trench according to claim 1, wherein the size of the crystal grain is between 15 and 30 nm. 4. The method of preparing a deep trench according to claim 1, wherein the nitrogen-containing layer is a nitrile layer and the disk-containing oxide layer is filled with a stone layer on one side. According to the preparation method of the moon-length item i, the nitrogen-containing layer is a nitrile layer and the niobium-containing layer is a scale stone layer. 6. The method for preparing a deep trench according to claim 1, wherein a surface system containing a ruthenium oxide is formed by a low pressure chemical vapor deposition process. • The method of preparing a deep trench of claim 1, wherein the substrate is placed in a water vapor environment. The method for preparing a deep trench of claim 7, wherein the reaction temperature of the oxide-containing layer: the etching solution is between 7 〇 (M〇〇〇〇C. 9) according to the request j酉s 夕, acupoint, The preparation method of the 8th-ditch of the squad, wherein the side is made 1302343 1〇.= According to the preparation method of the deep trench of claim 1, after removing the layer I without being covered by the grain, The method comprises the following steps: preparing a phosphorus-containing oxide layer which is not converted into a silver engraving liquid in the trench. 11. The method for preparing a deep trench according to claim 10, wherein the etching solution of the fish etching process dilutes hydrofluoric acid Or buffering hydrofluoric acid. 12. According to the preparation method of the deep trench of claim i, after removing the nitrogen layer not covered by the crystal grain, the method further comprises performing a one-touch process, and the button is not included in the The inner wall of the trench covered by the nitrogen layer forms a concave-convex surface. 13. The preparation method of the deep trench according to claim 12, wherein the residual liquid of the (four) etching process comprises ammonia water. 14. According to the deep trench of claim 12 a method for preparing a wood, wherein the wet etching process is covered by the die The nitrogen-containing layer is an etch mask. ', 15. According to claim 12, the method of preparing a gentle trench for a deep trench, wherein the wet-etched sputum is except for the grain on the nitrogen-containing layer. Item 12: The deep trench is the electrode of the 掣 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再 再