TW201234469A - Shallow trench isolation chemical mechanical planarization - Google Patents

Abstract

A polishing method includes polishing, in a first polish, a wafer to remove overburden and planarize a top layer leaving a portion remaining on an underlying layer. A second polishing step includes two phases. In a first phase, the top layer is removed and the underlying layer is exposed, with a top layer to underlying layer selectivity of between about 1: 1 to about 2: 1 to provide a planar topography. In a second phase, residual portions of the top layer are removed from a top of the underlying layer to ensure complete exposure of an underlying layer surface.

Description

201234469 VI. Description of the invention: [Technical field to which the invention pertains] U.S. Provisional Serial proposed in this application on October 4, 2010

No. 6 1 / 3 89,546 claims priority and is incorporated herein by reference in its entirety. This application is related to the application for joint transfer: "Chemical mechanical flattening with overlay mask", serial number (TBD) (agent case number YOR9 20100499USl (163-369)), one at the same time; A chemical mechanical planarization method for manufacturing a fin field effect transistor device, serial number (TBD) (proxy case number Y〇R920 1 005 3 7US2 (1 63-3 72)), one at the same time; and The method for manufacturing a replacement metal gate device, the serial number (TBD) (agent case number YOR920100538USl (1 63 - 3 73)), is also proposed at the same time, and is incorporated herein by reference. [Prior Art] The present invention relates to semiconductor fabrication and devices, and more particularly to systems and methods for chemical mechanical planarization (CMP). The shallow trench isolation (STI) structure introduces a 0.25 μη technology node to replace the conventional LOCOS (local niobium oxide) structure to provide better device isolation. The STI fabrication process includes a chemical mechanical planarization (CMP) step. Shallow trench isolation CMP is one of the applications of the Front End Process (FEOL) CMP method and presents some technical and manufacturability challenges. The main factors affecting the S TI C Μ P method are i) the variation of the pattern density of the whole wafer, Π the variability of the trench etching method affecting the wall slope and the oxide filling, and iii) the use of 201234469 "Oxide" type of cerium oxide (eg, tetraethyl orthosilicate (TEOS), high density plasma (HDP) oxide, high aspect ratio method (HARP) oxide) and hereinafter referred to as "nitride" Niobium nitride (such as plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), rapid high temperature chemical vapor deposition (RTCVD)). Variations in thickness and uniformity of oxide and nitride deposition on the entire wafer are also factors influencing STI CMP. Second, subsequent method steps are affected by the CMP method. It is advantageous to completely remove all oxides on the nitride. Otherwise, the residual oxide becomes a mask when the nitride is stripped, leaving the remaining nitride. To ensure complete removal of oxides on the nitride, a dilute buffered HF etch can be used. However, this increases the loss of the trench oxide and amplifies the scratch defects. The final morphology will be significantly affected by both the CMP process and the post-CMP wet etch process. Discrimination, erosion, and nitride thickness associated with pattern density are some contributing factors to the non-flatness of the STI CMP method. However, even if the STI CMP method achieves perfect flatness and the overall pattern density is perfectly uniform for the post-CMP nitride thickness, the sacrifice of nitride removal results in a non-flat surface. Because both the polishing rate and the wet etch rate are related to the pattern density, the non-uniformity accumulated from all sources results in large morphological variations. The effect of pattern density significantly affects the flatness of the post-CMP. Due to the close similarity of oxide dielectric materials used for interlayer dielectric (ILD) polishing, the early STI CMP method used the same consumables (pads, prizes) and method parameters as ILD CMP. Since all oxides on the nitride should be removed in a large active area as well as in a highly dense array, a specific amount is required.

-6- S 201234469 Over-polished. This results in the removal of the entire nitride layer in some features and the erosion of trench oxides in other regions. This is due to the high polishing rate of the nitride of the conventionally used oxide paste (about 300 A/min). A method of polishing a wafer, which is included in the first polishing step, removes the cover layer and The top layer is flattened so that the portion remains on the lower layer. The second polishing step includes two stages. In the first stage, the top layer is removed and the lower layer is exposed, so that the top layer to the lower layer is selected at a ratio of about 1:1 to Approximately 2:1 to provide a flat topography. In the second stage, the remaining portion of the top layer is removed from above the lower layer to ensure complete exposure of the underlying surface. A method of polishing a shallow trench isolation (STI) structure, To planarize the oxide layer and expose the underlying nitride, comprising a first chemical mechanical polishing step to remove the cap layer and planarize the oxide layer, leaving an oxide of 300 to 600 A; second chemical mechanical polishing The step includes two stages, having: the first stage includes removing the oxide layer and exposing the underlying nitride surface such that the oxide to nitride selection ratio is about 1:1 to 2:1 to provide a flat shape And the second stage involves removing the residual oxide remaining above the nitride surface to ensure complete exposure of the nitride surface. A detailed description of the following illustrative examples will be made in conjunction with the accompanying drawings, which will Advantages are obvious. [Embodiment] 201234469 The present invention provides a chemical mechanical planarization method for a semiconductor device structure. In a particularly applicable embodiment, the semiconductor device structure includes a shallow trench isolation structure. The method uses a series of steps including different The electrical material has a different ratio of the slurry. Although other materials that are selectively etched relative to the other can be used, the dielectric material can comprise an oxide and nitride layer. In one method, the first step comprises colloidal The cerium oxide slurry or cerium oxide/surfactant slurry is polished to reduce the cover layer and flatten the initial topography, leaving a thin layer, such as an oxide of about 300 to 600 A. The next step includes two stages. In the first stage, the slurry with the top to bottom ratio is used to remove the top layer and remove the underlying layer. In a specific example, the selection ratio may include an oxide (top layer) to a nitride (lower layer) of about 1:1 to 2:. In the second stage, a higher top layer polishing rate and no significant lower layer are used. Rate slurry to remove any residual top layer material remaining above the lower layer. This ensures complete exposure of the entire lower layer' so that the lower layer can be removed by wet etching in subsequent processing. This principle uses different choices between layers. Ratio of slurry, such as oxides and nitrides, to a highly flat post-chemical mechanical planarization (CMP) surface. In methods using oxides and nitrides, excessive oxide capping is removed', for example, after polishing An oxide of about 300 A. For this planarization step, an oxide polishing slurry having an oxide to nitride selectivity ratio of, for example, 4:1 or a cerium oxide/surfactant-based slurry can be used. In the next step 'a slurry with an oxide-to-nitride selectivity of approximately 1:1 can be used to achieve an equal polishing rate for the oxide and nitride regions' to avoid differences in polishing rates between the two materials. Diskization and invasion

-8- S 201234469 Eclipse. In order to ensure no residual oxide on the nitride, the use rate and negligible nitride rate plus trimming to prevent the nitride from being removed during trimming and polishing to remove trace oxides can be accomplished by changing the composition of the slurry used. . The flow and block diagrams in the drawing are performed in the order in which the alternative graphics are indicated. For example, depending on the functionality contained in the continuously displayed views, the blocks may in fact be executed substantially in reverse order. It should be understood that the words of the illustrative architecture are given. However, other architectures, structures, substrate materials, and methods vary within the scope of the invention. The entire article reveals the oxide crystalline material. However, these materials are illustrative and other materials within the scope. In addition, the entire disclosure reveals that the thickness dimension is illustrative and that other dimensions can be used as in this principle. The apparatus described herein can be designed for use in a computer programming language for the integrated circuit chip design, in a storage medium (eg, magnetic Discs, tapes, and physical hard drives capture virtual hard drives in the network). If the designer does not make a lithographic mask to fabricate the wafer, the designer can use a physical mechanism to design a copy of the stored storage medium. The resulting design is indirectly electronically converted (eg, via the network) to the actual design to the appropriate design. The fabrication of the format (eg, GDS 11) typically involves the formation of a crystal replica on the wafer. The lithographic mask is used to define the high oxide speed to be etched or other options. This can be any loss. In this example, the present invention may be implemented in the following two blocks, or the present invention may be described, and the steps may be in the form of nitrides and more considerations in the dimensions of the present invention. These degrees. Part of it. Crystallized and stored in a computer, or for example, a wafer for storage or use (for example, providing a wafer that is to be metered, or directly or in bulk, and then stored for lithographic mask design) (and • 9 - 201234469 / Or a layer thereon. The method described herein can be used to fabricate integrated circuit wafers. The resulting bulk circuit wafer can be in the form of a coarse wafer as a dummy mode (ie, a single wafer with multiple packaged wafers) or packaged. The manufacturer of the form is divided into the latter, the wafer is packaged in a single chip (such as a plastic carrier with wires fixed to the board, or other higher order carrier) or in multiple packages (eg, interconnected or buried) One or two ceramic carriers are attached. In either case, the wafer is added to its sheets, discrete circuit components, and/or other signal processing devices as (a) intermediate products, such as motherboards or (b) a portion of the final product, which may include integrated circuit chips, ranging from toys and low-end applications to higher levels with displays, keyboards or other input devices, and intermediate devices Any product of a brain product. Reference is now made to the accompanying drawings, wherein like numerals represent the same or like parts, and the cross-section of the method as shown in the illustrative embodiment of FIG. 1. An advantage of this method is that it provides a different ratio. The flexibility of the slurry to achieve a highly flat post-polish morphology. This uses a slurry that provides different polishing rates for the top and bottom layers, which can be added to a highly flat post-polished surface. For purposes of explanation, oxides are described. The top layer and the nitride. These materials represent the commonly used material pairs and are particularly suitable for shallow trench separation methods. Other materials and material pairs can also be used. The slurry composition of the STI CMP method is also described. At the time, the semiconductor substrate 10 has the accumulated weight of the trench formed therein. The crystal of the host recrystallizer is described by the meta-CMP selection method of the other central portion to change the lower channel.

-10- S 201234469 It is to be used to form shallow trench isolation. The trenches 12 are etched into the substrate 10 by forming and patterning a lithography mask and may include an oxide pad 14 and a nitride pad 16 in addition to a layer. Oxide 18 (e.g., TEOS, HDP oxide, HARP) is deposited in trench 12 and over nitride pad 16. It should be understood that other structures can be used. In step 100, the oxide cap layer 19 is removed by polishing. One goal of this step is to reduce the large initial topography, remove the overall oxide cap layer, and leave a flat oxide layer of approximately 300A to 600A, preferably approximately 300A, throughout the device (eg, a semiconductor die). 20. Since a high oxide removal rate is desired at the initial stage of polishing and the surface of the nitride is not actually exposed, the selection ratio of the slurry is less concerned in step 100. This can be achieved by an oxide polishing slurry having an oxide to nitride selectivity of about 4:1. The oxidizing slurry may include a base such as potassium hydroxide or ammonium hydroxide, and the oxidative honing agent may be selected from the group consisting of fumed cerium oxide and colloidal cerium oxide. However, in order to improve flatness and achieve a uniform oxide thickness throughout various pattern densities, it may be desirable to incorporate an additive into the oxide slurry. A cerium oxide/surfactant system can also be used in step 100 to achieve the desired level of flatness and uniformity. In step 200, planarization polishing is performed. Step 200 removes the oxide layer 18 remaining at about 300 A, exposing the underlying nitride-covered surface (nitride pad 16), and achieving a highly flat final without defects (eg, polishing scratches, pits, and other stains). surface. In order to achieve high flatness, it is preferred to have substantially the same polishing rate for the oxide and nitride covering surfaces. The polishing rate of oxides and nitrides should not be very high, as this would be incompetent -11 - 201234469 avoiding poor controllability. Therefore, it is highly desirable to have a slurry having a polishing rate for oxides and nitrides in the range of from about 300 to about 600 A/min. This will provide proper polishing time with good controllability and allow over-polishing edges to flatten difficult-to-polish structures. Chemical mechanical planarization polishing rates for different materials with line width, pattern density, and actual circuit configuration The feature size varies. In a warp-type structure, the local polishing rate of the different materials is a very complex function of the polishing rate of the same material in the cladding wafer. Therefore, it is advantageous to polish the warp of the pattern and experimentally measure the flatness to optimize the selection ratio of the slurry to ensure that the desired target is achieved. Since the configuration of the modes varies between the technical nodes and even between different products of the same technology node, it is highly desirable to be able to vary the polishing rate selection ratio by varying the concentration of the components in the slurry. The polishing rate selection is "adjustable" in step 200 over a range of slurry systems that can be used for a wide range of products and technology nodes. The ability to adjust the polishing rate selection ratio is a factor in the polishing step 200 using this process to achieve a highly flat final surface. Step 200 includes two phases. In stage 210, one target is to achieve a highly flat surface. This can be accomplished by an oxide to nitride selection ratio, for example, from about 1 to about 2:1. In some areas covered by nitride, a thin layer of oxide may remain above the nitride, and these areas may require further polishing (over-polishing) to remove oxides and completely expose the nitride. Excessive removal of nitride can occur if the slurry is selected for over-polishing with a ratio of 1:1 to 2:1. Therefore, a goal of the second stage polishing 2 20 (as needed) is to ensure that the oxide remaining above the nitride goes

-12- S 201234469 No significant loss of nitride occurs during time division. This uses a slurry with a high oxide polishing rate and no significant nitride polishing rate. The slurry composition provided by this principle provides a oxide to nitride selectivity ratio of about 1:1 to 2:1 for the first stage polishing and a higher oxide to nitride for the second stage 220. The choice is better than that. In one embodiment, two different slurry composition components are used in the first stage 210 and the second stage 220. In another embodiment, a two component slurry system is provided, wherein both components are used in the first stage polishing 210 and only one component of the slurry system is used in the second stage 220. In another embodiment, only one component is used in the first phase 210 and both components are used in the second phase 2 20 . In step 300, additional etching may be performed to prepare the additional treatment to clean the surface. The etch may include an HF etch for oxide removal, or a dilute HF etch, and a hot phosphoric acid (H3P04) wet etch for nitride removal. As shown in Figure 1, nitride 16 is removed from oxide 14 after step 300. The slurry as a specific example may include the following components: a) a honing agent, b) a pH adjuster, and c) an organic acid. a) honing agent: The honing agent may be at least one type of honing agent selected from the group consisting of inorganic particles and organic particles. Examples of the inorganic particles may include cerium oxide, aluminum oxide, titanium oxide, zirconium oxide, cerium oxide, and the like. Examples of the cerium oxide may include fumed cerium oxide, cerium oxide synthesized by a sol method, colloidal cerium oxide, and the like. The ruthenium oxychloride is obtained by reacting ruthenium chloride or the like with oxygen and water in a gaseous state. The alkoxy ruthenium compound is hydrolyzed as a starting material and/or the ruthenium is synthesized by the sol method. Colloidal cerium oxide can be obtained, for example, by an inorganic colloidal method using a previously purified starting material. Examples of the organic particles may include polyvinyl chloride, styrene (co)polymer, polyacetal, polyester, polyamine, polycarbonate, olefinic hydrocarbon (co)polymer, phenoxy resin, acrylic acid (total ) polymers and the like. Examples of the olefinic (co)polymer may include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, and the like. Examples of the acrylic (co)polymer may include polymethyl methacrylate or the like. The average particle diameter of the honing agent is preferably from 5 to 500 nm, more preferably from 10 to 200 nm, and still more preferably from 20 to 150 nm. A suitable polishing rate can be achieved using honing agent particles having an average particle diameter within this range. b) pH adjuster: The pH of the slurry as in the specific example is preferably from 1 to ′′ and more preferably from 2 to 6. Adjusting the pH of the slurry to this range achieves an appropriate polishing rate. Examples of the pH adjuster may include an organic base, an inorganic base, and a mineral acid. Examples of the organic base may include tetramethylammonium hydroxide, triethylamine, and the like. Examples of the inorganic base may include ammonium hydroxide, potassium hydroxide, sodium hydroxide, and the like. Examples of the inorganic acid may include nitric acid, sulfuric acid, phosphoric acid, and the like. c) Organic acids: Organic acids are used as accelerators for the rate of nitride polishing. Various organic acids such as a monobasic acid (e.g., monodecanoic acid), a dibasic acid (e.g., dicarboxylic acid) 'polyacid (e.g., polycarboxylic acid), and a carboxylic acid having a substituent (hydroxyl, amine) can be used. Examples of the organic acid include a saturated acid, an unsaturated acid, an aromatic acid, and the like. Examples of the saturated acid may include formic acid, acetic acid, butyric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and the like. Examples of the acid containing a hydroxyl group may include lactic acid, malic acid, tartaric acid, citric acid, and the like. -14-

Examples of S 201234469 unsaturated acid may include maleic acid, fumaric acid, and the like. Examples of the aromatic acid may include benzoic acid, phthalic acid, and the like. It is preferred to use an organic acid having two or more carboxylic acid groups to obtain a high nitride polishing rate. Salts of these organic acids (for example potassium or ammonium salts) can also be used. Other Ingredients: This specific example allows other ingredients to be added to the slurry to adjust the oxide to nitride selectivity ratio. The slurry as a specific example may include a surfactant. Examples of the surfactant may include anionic, nonionic, and cationic surfactants. Examples of the anionic surfactant may include at least one functional group selected from the group consisting of a carboxyl group (-COOX), a sulfonic acid group (-so3x), and a phosphate group (-hpo4x) (wherein X represents hydrogen, ammonium, or a metal). Surfactant. Examples of the anionic surfactant may include aliphatic and aromatic sulfates and sulfonates, phosphates and the like. Preferably, for example, a compound such as potassium dodecylbenzenesulfonate, ammonium dodecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, alkylsulfosuccinate, potassium alkynylsuccinate or the like is used. An aliphatic soap such as potassium oleate can be used. These anionic surfactants can be used singly or in combination. Examples of the nonionic surfactant may include polyoxyethylene alkyl ether, ethylene oxide-propylene oxide block copolymer, acetylene glycol, ethylene oxide addition product of acetylene glycol, acetylene alcohol and the like. It is to be noted that a nonionic polymeric compound such as polyvinyl alcohol, cyclodextrin, polyvinyl methyl ether, or hydroxyethyl cellulose can also be used. Examples of the cationic surfactant may include aliphatic amine salts, aliphatic ammonium salts and the like. Further, in polishing to control the selection ratio, for example, poly(acrylic acid) and a polyelectrolyte thereof such as sodium, potassium, and ammonium salts may be added. Use the following examples to further illustrate the principles of the -15-201234469 including the function of the slurry components. It is to be noted that the present invention is not limited to the following examples. Although these materials can be used in other steps as in this principle, 'Examples 1 - 5 can be used for Step 1 0 0. In Example 1, the effect of additional ammonium hydroxide on a colloidal cerium oxide granule having a primary particle diameter of 35 nm (which is commercially available, for example, from Fuso Chemical Co., Ltd., Japan) is provided as an illustrative example. Suitable for slurry. This colloidal oxidative honing agent is an example of a commercial oxidative honing agent that can be used to achieve characteristics as in this principle. With this slurry, the rate of selection of oxide to nitride can be achieved from 0 to 1. However, the polishing rate for both oxides and nitrides can be kept low. In Example 2, citric acid with cerium oxide granules provided a very high selectivity to oxides. The polishing rate of the oxide is in the range of 450 to 600 A/min, and the rate of the nitride is close to 〇. In Example 3, citric acid and ammonium hydroxide with cerium oxide granules provided an oxide to nitride rate selection ratio of 〇1. The polishing rate of the oxide is in the range of 150 to 500 A/min, and the rate of the nitride is varied from 0 to 250 A/min. In Example 4, the phosphoric acid with cerium oxide provides a ratio of oxide to nitride rate selection from 〇 to 1. In this case, the rate of the oxide varies from 400 to 65 A/min, and the rate of the nitride varies within a narrow range of 150 to 200 A/min. Here, the change in the selection ratio is achieved by allowing the oxide rate to change while maintaining the polishing rate of the nitride almost fixed or in a very narrow range. In Example 5, citric acid, ammonium hydroxide and phosphorus with a gasification honing agent

-16- S 201234469 Acid provides oxide to nitride rate selection ratio of 〇 to 0.4. The polishing rate of the oxide is almost fixed or in a very narrow range (450 to 470 Å/min), while the rate of nitride varies from 0 to 2 50 Å/min. The change in the 'selection ratio' is achieved by allowing the nitride rate to change while maintaining the polishing rate of the oxide almost fixed or in a very narrow range. The slurry suitable for the step 210 (first stage) polishing in Example 6 includes, for example: 1) a cerium oxide granule in the range of 0.5 to 30% by weight, preferably 5 to 10% by weight, 2) An organic acid in the range of 0.5 to 50 g/L, preferably in the range of 3 to 25 g/L, 3) an acidic pH adjusting agent in the range of 0.01 to 5 g/L, preferably in the range of 0 · 1 to 2 • 0 g/L, 4) an alkaline pH adjuster in the range of 0 to 5 g/L, preferably in the range of 〇 to 2 g/L, and 5) a pH of the slurry in the range of 1 to 11, preferably The range is 2 to 6. Particularly useful examples of the blend of Example 6 in Example 7 include: 1) 5 wt% colloidal cerium oxide granules dispersed in water, 2) 5 g/L citric acid, 3) 0.25 to 0.35 g/ The phosphoric acid of L, 4) 0.1 to 0.5 g/L of ammonium hydroxide, and 5) the pH in the range of 2 to 5, preferably a pH of about 4. Another particularly useful example of the blend of Example 6 in Example 8 includes:

S -17- 201234469 1) 1% by weight of colloidal cerium oxide grinding agent dispersed in water, 2) 10 g/L citric acid, 3) 1 to 2 g/L phosphoric acid, 4) 0.1 to 2.0 g /L of ammonium hydroxide, and 5) pH in the range of 2 to 5. Referring to Figure 2, in another embodiment, polishing table 404 is shown schematically as an illustrative example. Table 404 includes a rotating pad 402 upon which semiconductor wafer 410 is polished. The wafer carrier 414 holds the wafer 410 by vacuum suction through the back film 412. The wafer 410 is mounted in such a manner that the surface to be polished is in contact with the polishing pad 402. Polishing paste 406 (and/or 408) may comprise one component or multiple components. The flow rate of the components is controlled using a schematically described valve 416, which is preferably automated. In one embodiment, the slurry comprises two parts: a first part - a honing agent slurry (such as cerium oxide), an organic acid and an acidic pH adjusting agent, a second part - an alkaline p Η adjusting agent and an acid p Η regulator. The slurry can be supplied to the polishing table 404 as two components 406, 408 and allowed to mix on a polishing table to produce a slurry having the desired final composition. By using the same or different slurry flow rates, the slurry composition can be varied during polishing to achieve the desired polishing rate of the oxide and nitride at different polishing stages. In another example, the first part and the second part are used initially, and after a certain time, the second part is turned off to produce a slurry having a different oxide to nitride selectivity than the original blend. material. A similar effect can be achieved by maintaining a constant flow rate of one component while changing the polishing process. In another specific example, the slurry comprises two parts: Part 1 - 硏 -18 -

S 201234469 Grinding agent slurry (such as cerium oxide), organic acid and acid Ρ conditioner; Part 2 - cerium oxide grinding agent slurry, alkaline ρ Η adjusting agent and acidic Η Η adjusting agent. The slurry can be supplied to table 404 as two components 406, 408 and mixed on a polishing table 404 to produce a slurry having the desired final composition. By using the same or different slurry flow rates, the slurry composition can be varied during polishing to achieve the desired polishing rate of oxides and nitrides at different polishing stages. The first part is used initially, and after a certain period of time, the first part is turned off and the second part is turned on to produce a slurry having a different oxide to nitride selectivity than the original composition. In another embodiment, these slurries are used as the two separate slurries for the first stage and the second stage of polishing. The second stage slurry should have a high oxide to nitride selectivity ratio without significant nitride polishing rate. An example of a slurry composition having this ability is explained below. In Example 9, the slurry of the second stage (step 220) may comprise: 1) 5% by weight colloidal cerium oxide grinding agent dispersed in water, 2) 5 g/L citric acid, 3) 0.25 to 0.35 g /L of phosphoric acid, and 4) pH in the range of 2 to 3. Another example of the slurry of the second stage (step 220) in Example 10 includes: 1) 10% by weight of colloidal cerium oxide granules dispersed in water, 2μ 5 g/L of citric acid, 3) 0.25 to 0.35 g/L phosphoric acid, 4) 0.5 g/L ammonium hydroxide, and -19-201234469 5) pH in the range of 2 to 3. Referring to Figure 3, the removal rate versus pH plot is schematically shown to show the effect of pH on the oxide and nitride polishing rate of the cerium oxide etchant. At a pH ranging from 2 to 7, the polishing rate of the nitride is from about 150 to 650 A/min. The highest enthalpy reaches a pH of about 3.5. The rate of oxide enthalpy is in the range of about 10 to 100 A/min, which is significantly lower. At pH values between 8 and 10, the oxide and nitride rates are kept low. From pH 1 1 to 13, the rate of oxide begins to increase while the rate of nitride remains low. The pH of these solutions was adjusted to a range of 1 to 7 with phosphoric acid, and was adjusted to a range of 8 to 11 with KOH. Referring to Figure 4, a method of planarizing a top layer in two or more steps and exposing the underlying footprint to the STI structure is provided. In a particularly suitable embodiment, the top layer comprises an oxide and the lower layer comprises a nitride. However, it should be understood that the present principles include a nitride or other pair of materials over the oxide that can be selectively etched relative to the other. In block 502, chemical mechanical polishing removes any cover layer and planarizes the oxide layer leaving an oxide of 300 to 600 Å. This polishing is carried out with an oxide slurry containing a cerium oxide abrasive or a slurry containing a cerium oxide abrasive and a surfactant. In block 594, there are two stages in chemical mechanical polishing. In block 506, the first stage includes removing the oxide layer and exposing the underlying nitride-covered surface to a ratio of oxide to nitride of about 1:1 to 2:1 to achieve a highly planar morphology . In block 508, the second stage includes removing any residual oxide remaining above the nitride layer to ensure complete exposure of the nitride surface.

-20- S 201234469 The first stage (block 506) may include cerium oxide granules dispersed in an aqueous solution at a concentration of 〇5 to 3% by weight, 有机.〇1 to 30 g/L of organic An acidic pH adjuster in the range of 1 to 1 〇g/L of acid, 〇·〇, and an alkaline pH adjuster in the range of 15 g/L. The slurry pH of the first stage (block 5〇6) can range from 1 to 11. The preferred component of the first stage (block 506) may comprise 5% by weight of colloidal cerium oxide granules dispersed in water, 〇5 to 50 g/L having two or more carboxylic acid groups. The organic acid, 0.25 to 0.35 g/L of the inorganic acid, 0_丨 to i.og/L of the inorganic base, has a pH in the range of 2 to 5, preferably pH 4. The slurry of the second stage (block 5 08) may comprise from 0.5 to 30% by weight of colloidal oxidized sand honing agent, 有机. 〇1 to 3 〇g/L of organic acid dispersed in an aqueous solution, 0.01 to Acidic pH regulator in the range of 10 g/L. The pH of the slurry in the second stage (block 508) is preferably from 1 to 5. The preferred component of the first stage (block 508) comprises 5 to 10% by weight of colloidal oxidized sand honing agent dispersed in water, and 5 g/L of organic acid having two or more residual acid groups. , 0.25 to 0.35 g / L of inorganic acid, PH in the range of 2 to 3. In blocks 510 and 512, the slurry of blocks 506 and 508 can be introduced in two or more portions and varied to achieve the desired result. In one embodiment, the slurry can be used as a two-part slurry having the following composition: Part 1 · 0·5 to 30% cerium oxide slurry + 0.5 to 50 g/L of organic acid + 0.01 to 5 g/L of an acidic pH adjuster; and a second part - 0.01 to 5 g/L of an alkaline pH adjuster + 0.01 to 50 g/L of an acidic pH adjuster. The slurry can be supplied to the table as two ingredients and allowed to mix -21 - 201234469 on a polishing table to produce a slurry with the desired final composition. By using the same or different slurry flow rates, the composition of the slurry can be varied during polishing to achieve the desired polishing rate for oxides and nitrides at different polishing stages. In another embodiment, the slurry can be used as a two-part slurry having the following composition: Part 1 - 0.5 to 30% cerium oxide slurry + 0.5 to 50 g/L organic acid + 0.01 to 5 g/L acidic pH adjuster, second part - 0.5 to 30% oxidized sand honing agent prize + 0.01 to 5 g/L alkaline pH adjuster + 0.01 to 50 g/L acidity pH regulator. The slurry can be supplied to the table as two components and mixed on a polishing table to produce a slurry having the desired final composition. By using the same or different slurry flow rates, the composition of the slurry can be varied during polishing to achieve the desired polishing rate for oxides and nitrides at different polishing stages. In yet another embodiment, the slurry provides a high polishing rate for the oxide and no significant polishing rate for the nitride. The composition of the slurry may include 0.5 to 7% by weight of a colloidal cerium oxide grinding agent dispersed in water, 5 g/L of an organic acid having two or more carboxylic acid groups, and 0.25 to 0.35 g/L. The inorganic acid has a pH in the range of 2 to 3. The other component of the slurry comprises 8 to 20% by weight of colloidal cerium oxide grinding agent dispersed in water, 15 g/L of organic acid having two or more carboxylic acid groups, 0.25 to 0-35 The g/L inorganic acid, 0.01 to 5 g/L ammonium hydroxide, has a pH in the range of 2 to 5, preferably a pH of about 4. In yet another embodiment, the slurry provides a high polishing rate for the nitride and no significant polishing rate for the oxide. The composition of the slurry includes 5 to 10% by weight of a colloidal cerium oxide granule, 0.1 to 10 g/L of a mineral acid, and a pH in the range of 2 to 6.

-22- S 201234469. In block 51, a cleaning etch can be performed to remove residual material. For example, wet etching of HF or hot phosphoric acid can be performed. In block 514, the semiconductor wafer or mold can continue to be processed as recorded. Having described the preferred embodiments of the chemical mechanical planarization (CMP) system and method for shallow trench isolation, which are intended to be illustrative, but not limiting, it is noted that modifications and variations can be made by those skilled in the art in light of the above teaching. Therefore, it is to be understood that the modifications made in the particular embodiments disclosed are within the scope of the invention as defined by the appended claims. Therefore, the claims as set forth in the Detailed Description of the Invention and the specificity required by the Patent Law, the claims and the claims of which are protected by the Letters Patent are listed in the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS The details of the disclosure are provided by the following description of the preferred embodiments of the invention, in which: FIG. 1 is a schematic diagram showing a cross section of a semiconductor device and method steps to illustrate two steps as in the present principles. a shallow trench isolation (STI) chemical mechanical planarization (CMP) method; FIG. 2 is a two-part slurry system diagram showing a two-part slurry with variable flow rate as shown in a specific example; KOH adjusts the pH effect on the oxide and nitride polishing rates; and Figure 4 is a flow chart showing an illustrative method as in this principle. -23- 201234469 [Explanation of main component symbols] 1 〇: semiconductor substrate 12: trench 1 4 : oxide pad 1 6 : nitride pad 1 8 : oxide layer 1 9 : oxide cap layer 20: flat oxide layer 402: Rotating pad 404: Polishing table 406: Slurry 408: Slurry 4 1 0 · Wafer 4 1 2: Back film 4 1 4 : Wafer carrier 4 1 6 : Valve-24-

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Claims (1)

201234469 VII. Patent application scope: 1. A polishing method comprising: polishing a wafer in a first polishing to remove a cover layer and flatten the top layer to leave a portion on the lower layer; Polishing in two stages of polishing, wherein in the first stage, the top layer is removed and the lower layer is exposed such that the top to bottom selection ratio is between about 1:1 and about 2:1' to provide a flat topography: And in the second stage, the remaining portion of the top layer is removed from above the lower layer to ensure that the underlying surface is completely exposed. 2. The method of claim 1, wherein the polishing in the first polishing comprises removing the cover layer to reduce the top layer to between about 30,000 A and 6,000 A 〇3. The method of claim 1, wherein the first stage of removing the top layer and exposing the lower layer includes adjusting a ratio of a line width, a pattern density, and a characteristic size on the crystal circle. 4. The method of claim 1, wherein the top layer comprises an oxide and the lower layer comprises a nitride, and the step of removing the top layer and exposing the lower layer in the first stage comprises: having a polishing rate of about 30,000 The slurry to about 600 A/min is polished with oxides and nitrides. 5. The method of claim 1, wherein the top layer comprises an oxide and the lower layer comprises a nitride, and the step of removing the residual portion in the second stage comprises using an oxide polishing rate and no significant nitrogen. A slurry of the polishing rate. C-25-201234469 6. The method of claim 5, wherein the material comprises: 〇5 to 7% by weight of colloidal cerium oxide grinding agent dispersed in water, having two or more carboxylic acids 5 g/L of organic acid of the group, 0.25 to 35 g/L of mineral acid and pH in the range of 2 to 3. 7. The method of claim 5, wherein the forging comprises: 8 to 20% by weight of colloidal cerium oxide grinding agent dispersed in water, 15 g/L having two or more carboxylic acid groups The organic acid, 〇·25 to 0 35 g/L of the inorganic acid, 0.01 to 5 g/L of ammonium hydroxide and the pH in the range of 2 to 5. 8. The method of claim 5, wherein the material comprises: 5 to 10% by weight of a colloidal cerium oxide abrasive, 〇1 to 10 g/L of a mineral acid, and a pH in the range of 2 to 6. Inside. 9. The method of claim 1, wherein at least one of the two stages of the second polishing comprises a slurry of two components, wherein the two components of the slurry are used in one stage, and one of the slurry The composition is used in other stages. 10. The method of claim 1, wherein the polishing of the first stage comprises a slurry of 0.5 to 30% by weight of an oxidized sand honing agent dispersed in an aqueous solution. The method of claim 10, wherein the slurry comprises an organic acid ranging from 0.01 to 30 g/L. 1 2. The method of claim 2, wherein the slurry comprises an acidic pH adjuster ranging from 0. 01 to 10 g/L. The method of claim 12, wherein the slurry comprises an alkaline pH adjuster in the range of S-26 to 201234469 in the range of 〇 to 15 g/L. 1 4 - The method of claim 1 wherein the polishing in the first stage comprises 5% by weight of a colloidal cerium oxide granule dispersed in water, 0.5 to 2 or more carboxylic acid groups A slurry of 50 g/L of an organic acid, 0.25 to 0.35 g/L of a mineral acid, an inorganic base of 0.1 to 1.0 g/L, and a pH in the range of 2 to 5. 1 5. The method of claim 1 wherein the polishing in the second stage comprises from 0.5 to 3% by weight of the colloidal cerium oxide abrasive dispersed in the aqueous solution, in the range of 0.01 to 30 g/L. The organic acid, an acidic pH adjuster in the range of 0.01 to 10 g/L, and a slurry having a pH of 1 to 5. 16. The method of claim 1, wherein the polishing in the second stage comprises having 5 to 1% by weight of a colloidal cerium oxide abrasive dispersed in water, and 5 g/L having two or more a carboxylic acid group organic acid, a 0.25 to 0.35 g/L inorganic acid, and a slurry having a pH in the range of 2 to 3, as in the method of claim 1, wherein in the second polishing stage The polishing in the slurry includes using a slurry as a two-part slurry comprising: having 0.5 to 30% by weight of a cerium oxide abrasive slurry, 〇5 to 50 g/L of an organic acid, and 0. 01 to 5 g a first portion of the slurry of the /L acidic pH adjuster; and a second portion of the slurry having an alkaline pH adjuster of 0.01 to 5 g/L and an acidic pH adjuster of 〇·〇1 to 5〇g/L, -27- 201234469 wherein the slurry can be supplied to a polishing table as a mixture of two components on the polishing table to change the flow rate of the first portion of the slurry and the second portion of the slurry to obtain a top layer and The polishing rate of the lower layer at different polishing stages. 18. The method of claim 1, wherein the polishing in the second polishing stage comprises using a slurry as a two-part slurry comprising: 0.5 to 30% by weight of cerium oxide abrasive Slurry, 0.5 to 5 g/L organic acid, and a part-part slurry of 0.01 to 5 g/L acidic pH adjuster; and 0.5 to 30% cerium oxide abrasive slurry, 〇.〇1 a second partial slurry of 5 g/L alkaline pH adjuster and 0.01 to 50 g/L acidic pH adjuster, wherein the slurry can be supplied to a polishing table as two kinds mixed on the polishing table The composition changes the flow rate of the first portion of the slurry and the second portion of the slurry to obtain a polishing rate of the top layer and the lower layer at different polishing stages. 19. A method of polishing a shallow trench isolation (STI) structure to planarize an oxide layer and expose a nitride of the underlying layer, comprising: a first chemical mechanical polishing step to remove the cap layer and planarize the oxide layer , leaving an oxide of 300 to 600 A; a second chemical mechanical polishing step comprising two stages: the first stage includes removing the oxide layer and exposing the surface of the underlying nitride to select an oxide to nitride The ratio is about 1:1 to 2:1 to provide a flat topography; and the second stage includes removing residual oxidized -28 - 201234469 residues above the nitride surface to ensure complete exposure of the nitride surface. The method of claim 19, wherein the removing the residual oxide comprises using a slurry having an oxide polishing rate and no significant nitride polishing rate. 21. The method of claim 19, wherein at least one of the first stage and the second stage comprises a two-component slurry, wherein the two components of the slurry are used in one stage, and the slurry is One component is used in other stages. 2 2 The method of claim 19, wherein the first stage comprises an oxidized sand honing agent having a dispersion of 0.5 to 30% by weight in an aqueous solution, in a range of 0.01 to 30 g/L An organic acid, an acidic pH adjuster in the range of 1 to 1 g/L, and a slurry of an alkaline pH adjuster in the range of 15 g/L. 23. The method of claim 19, wherein the first stage comprises using a slurry as a two-part slurry comprising: having 0.5 to 30% by weight of a cerium oxide slurry, 0.5 to 5 Å a partial slurry of g/L organic acid and 〇.〇1 to 5 g/L acidic pH adjuster; and having an alkaline pH adjuster of 0.01 to 5 g/L and an acidic pH of 0.01 to 50 g/L a second portion of the conditioner, wherein the slurry is supplied to the polishing table as a mixture of the two components on the polishing table to cause flow rates of the first portion of the slurry and the second portion of the slurry Change 'to obtain the polishing rate of the top and bottom layers at different polishing stages. 2. The method of claim 19, wherein the first stage -29-201234469 comprises using a slurry as a two-part slurry comprising: having 0.5 to 30% by weight of cerium oxide abrasive slurry 〇5 to 5〇g/L organic acid, and 第一.〇丨 to the first part of the 5 g/L acidic pH adjuster; and 〇·5 to 30% cerium oxide abrasive slurry, 0.01 to 5 g/L of an alkaline pH adjuster and a second portion of a slurry of 1 to 5 g/L of an acidic pH adjuster, wherein the slurry can be supplied to a polishing table as the polishing table The two components are mixed to change the flow rate of the first portion of the slurry and the second portion of the slurry to obtain a polishing rate of the top layer and the lower layer at different polishing stages. 25. The method of claim 19, wherein the first chemical mechanical polishing step comprises removing the cover layer to reduce the oxide layer to between about 300A and 600A. -30- S