TWI244691B - Process for polishing a semiconductor wafer - Google Patents

Abstract

The invention relates to a process for the simultaneous polishing of the front surface and the back surface of a semiconductor wafer between two rotating polishing plates covered with polishing cloth while a polishing fluid is supplied, the polishing cloth of the lower polishing plate having a smooth surface and the polishing cloth of the upper polishing plate having a surface which is interrupted by channels, and the semiconductor wafer lying in a cutout in a carrier plate and being held on a defined geometric path, wherein the front surface of the semiconductor wafer, during polishing, is in contact with the polishing cloth of the lower polishing plate, and wherein the back surface of the semiconductor wafer, during polishing, is in contact with the polishing cloth of the upper polishing plate.

Description

1244691 Description of the invention (1) — [Technical field to which the invention belongs] It is intended to be suitable for making nanometer phases of semiconductor wafers with line widths less than or equal to 0. 丨. $ Important, Pure, Nano-materials (Lake) Pair, Nano-phase ”OR Gate, Ninzhen II 9 η \ 疋 义 疋: The flattening deviation of the entire wafer front is at two wavelengths 0 · 2 to 20 mm (within the relevant ^ area " inside (FCU. Fixed, Wengtian related length) and located in the " applicable surface then Q \ Ϊ area; the surface of the characteristic required by the product specification = must be qualified) The measurement of nanometer phase is based on the complete wafer surface = trace and overlap of measurement fields (area; range) with different sizes. It is found that the height change (peak to valley) in the surface can exceed the entire crystal. The larger value required by 51. The size of the measurement field depends on the specification. For example, it is defined as 2x 2 square millimeters, 5 × 5 square millimeters, and 10 × 10 square meters... The final nanometer phase of the circle is formed by polishing. In order to improve the flatness of the semiconductor wafer, the equipment and methods for polishing the front and back of the semiconductor wafer at the same time have been progressively improved and continuously developed. [Previous technology]

By way of example, the so-called double-sided polishing is described in U.S. Patent No. 3,691,694. According to the specific embodiment of double-side polishing described in European patent EP 208 3 1 5B1, the semiconductor wafer in the carrier disc with the appropriate size cutting frame is between two rotating polishing discs covered with polishing cloth, between In the presence of a polishing fluid, it moves along a path predetermined by the machine and processing parameters, so it is polished (in expert literature, the carrier plate is also called a template).

Page 41244691 V. Description of the invention (2) For example, the German patent DE 1 0 0 045 78C1 described the implementation of the double-sided polishing step by using a uniform, porous polymer foam with hardness A polishing cloth of 60 to 90 (Shore A). The document also revealed that the polishing cloth attached to the upper polishing disc has a grooved mesh, and the polishing cloth attached to the lower polishing disc does not have any such texture. The purpose of this measurement is: first, to ensure the uniform distribution of the polishing abrasive used in the polishing process, and second, to prevent the semiconductor wafer from sticking to the upper polishing cloth when the upper polishing disc is lifted after the polishing work is completed. In order to perform double-sided polishing, the semiconductor wafer is placed in a cutting frame in a carrier plate (conveyor board) by an appropriate method, and the back side of the semiconductor wafer is erected on the lower polishing plate. Therefore, during the polishing process, the back surface of the semiconductor wafer is polished by a non-textured polishing cloth adhered to the lower polishing disc, and the front surface of the semiconductor wafer is polished by a textured polishing cloth adhered to the upper polishing disc. The front side of the semiconductor is a surface on which electronic components are intended to be formed. After the polishing step, the semiconductor wafers are usually transferred to a water bath, for example, by means of a vacuum getter. This method of the existing technology cannot meet the requirements of implementing double-sided polishing for future generations of components and increasing the benefits of semiconductor wafers. Therefore, it is an object of the present invention to provide a method which can produce a semiconductor wafer having an improved nanophase, and can satisfy the requirements for manufacturing components with special needs. 3. Summary of the Invention The content of the present invention is a method for polishing a semiconductor wafer, which can achieve an improved nano configuration of polishing a semiconductor wafer. This type of semiconductor wafer is suitable for the semiconductor industry, especially for the manufacture of electronic components. The technical content of the present invention is: when a polishing fluid is supplied

Page 51244691 V. Description of the invention (3) Method for simultaneously polishing the front and back of a semiconductor wafer between two rotating polishing discs covered with a polishing cloth. The polishing cloth of the lower polishing disc has a flat surface, a bone surface and an upper surface. The surface of the polishing cloth of the polishing disc is spaced by grooves. The semiconductor circle is located in a cutting frame of the carrier and fixed on a defined geometric pattern. Among them, 'the surface of the semiconductor wafer is connected to The polishing cloth of the lower polishing disc is in contact, and during the polishing process, the back surface of the semiconductor wafer is in contact with the polishing cloth of the upper polishing disc.实施 IV. [Embodiment] The starting product of processing is a semiconductor wafer divided from a crystal by conventional methods, for example, it is separated from a silicon crystal, cut into a _ fixed length, and rounded by grinding. Edges, whose front and / or back sides are cut by means of grinding or lapping steps. The edges of the semiconductor wafer can also be rounded somewhere in the processing sequence by means of a suitably distributed grinding wheel. Furthermore, the surface of the semiconductor wafer may be etched after the grinding step. According to the present invention, when double-side polishing is to be performed, a semiconductor wafer is placed in a cutting frame of a carrier (conveyor board) in an appropriate manner, and its front surface is supported on a polishing cloth of a lower polishing disc. Therefore, in the process of performing double-side polishing, the front surface of the semiconductor wafer is in contact with the smooth polishing cloth of the lower polishing disc, and the back surface of the semiconductor wafer is in contact with the textured polishing cloth of the upper polishing disc. Otherwise, the double-side polishing process is performed in a manner familiar to those skilled in the art. The final product obtained by this method is a semiconductor wafer that has undergone double-side polishing and has been substantially improved in nanophase. In principle, the method of the invention can be used to make wafer-shaped objects.

Page 61244691 V. Description of the invention (4) $ = The system can be processed by common chemical-mechanical double-side polishing methods; '' 22% are examples of such materials (mainly implemented in the semiconductor industry / ,, And is not limited to such special applications) including: Shi Xi, ^ GeSi, SiN, GaAs, and other 冚 -v semiconductors. Moving stone eve (for example: by using the left Kolaskira crystal method or Fujia. Especially with (100), ⑴0) or "nn" This method is particularly suitable for making diameters of 200 mm, 300 mm , F / ifoo and ^ 5 + 0 mm and thickness from hundreds of microns to a few centimeters (especially from 400 microns to 1200 microns), + ^ is used to make semiconductor components Ba®. These semiconductor wafers can be Directly after the polishing step and / or Chi'er material, or after the implementation of the final silicon or other appropriate semiconductor material if / · / layer (❹: f-side sealing layer or adjustment by heat treatment; coating) according to the existing technology And / or hereby manufacture Shi Xi wafer for intended use. ^ P1I, ^ ® as an example, the method of the present invention will be further explained. And the method of mining and cutting method and the (depending on the diameter of the stone in the area) Even the wafer can be directly ^ / ϋ. The crystal lattice depth is 10 to 40 microns. Before the double-sided polishing is performed, the second and second yokes are double-sided polished. But the 'round' will be clearly defined and ^ 助 fsuit # Shaped grinding disc (sand round. Furthermore, to improve the wafer edge, the silicon wafer is polished to improve the sensitivity. Mechanical polishing cattle is used to remove and deduct the solar body layer, which can be used in the polishing step of the present invention (such as lapping or grinding) to reduce the surface and edges of the wafer that are unavoidably damaged. Fate ,,, and 0-day zones and removals may occur

1244691 Description of the invention (5) Any miscellaneous shells (for example, metal impurities connected to the buckle part) can be followed by an etching step. The embodiment of the etching step may be a chemical treatment or a plasma treatment of the silicon wafer in a basic or acidic etching mixture. For example, a technical report of the United States Computer Manufacturing Company (IBM) as 22.234 2 described a commercially available, double-sided polishing machine of an appropriate size. A surface polishing machine can be used to implement the polishing step of the present invention. The polisher master

Including: a lower polishing disc (which can be rotated freely on the horizontal plane), and an upper polisher 1, which can be rotated freely on the horizontal plane), these polishing discs are covered with a polishing cloth 'and can be used for semiconductor wafers (here Silicon wafers) are applied with material removal and polishing on both sides, while a polishing fluid continuously supplied with an appropriate chemical composition can be simultaneously polished. The polishing machine has a pin gear, usually, so the diameter of the reference disc, the silicon wafer can polish only a plurality of silicon wafers such as Shi Xi and the carrier disc to accommodate Shi Xi transmission or gradually reverse (to ) The carrier disk is polished under the light operation example package. The silicon wafer is eccentrically. A silicon wafer is preferably fixed during the two polishing processes of the polished wafer size wire gear and the external pin. The shadow includes: Polished and carrier disc circles are placed in a circle along the circumference. However, generally, in order to save costs, the number of passes depends on the structure of the polishing machine and is on a geometric path, which is defined by the processing parameters in the process and the cutting frame of the carrier disc. By way of example, the carrier disc and the polishing machine contact disc are rotated by means of a needle drive (via a rotating internal pin or ring gear and / or ring gear). The size of the upper and lower polishing discs related to the Xiangshixi wafer is the design of the carrier disc and the rotation speed of the upper disc. If the center of the carrier disc always moves around the center of the polishing machine. If the 'tray' of the carrier disc is about its own axis 1244691 V. Description of the invention (6) The rotation will form an inner cycloid path. = Better. Especially using four to six two advance forces at the same time: the cycloid has at least three Shi Xi wafers within the industry, the interval is regular, and the configuration; the road mother: the carrier is mounted on the disk, in principle, the method used in the method of the present invention is better) . These materials are made of mechanical materials caused by driving, and have sufficient mechanical stability. 1 more negative; serious chemical and mechanical invasion of the body and the polishing cloth, in order to withstand the use of sufficient life and prevent silicon wafers from being polluted after polishing: the material of the carrier plate must be suitable for the manufacture of highly flat I, no stress And volts: the carrier plate of the thickness and geometry of the material period. In principle: For example: =, with a pre-: disc can be reinforced by metal, plastic, glass fiber U plastic steel carrier disc is better. Alas. Especially stainless carrier discs have one or more cutting frame circles. To ensure that ... can be moved freely within, the knife knife cutting frame of the straight # must be slightly larger than the person who is polishing the stone wafer. A slightly larger diameter of 0.1 to 2 mm is preferred, and a slightly larger diameter of 0.3 to 3 mm is more preferred. In order to prevent the edge of the wafer from being damaged by the inner edge of the cutting frame in the carrier plate during the polishing process, as suggested in European Patent EP 2083 1 5B1: It is best to add a layer of plastic liner as thick as the carrier plate inside the cutting frame. . As described in German Patent DE 1 990 573 7A1, the thickness of the carrier disk used in the polishing process of the present invention is preferably from 400 to 120 micrometers, especially depending on the final thickness of the polished wafer. The stone removal amount during the polishing step is preferably from 5 to 100 microns, but preferably from 0 to 60 microns, especially from 20 to 50 1244691. V. INTRODUCTION (7) Micron is better.

Within the context of the description of face-down semiconductor wafer orientation, the 'double-side polishing step is preferably performed in a manner familiar to those skilled in the art. Polishing cloths with a wide range of properties are commercially available. The polishing is preferably performed using a commercially available polyurethane polishing cloth having a hardness of 40 to 120 (Shore A). Polyurethane cloth with a hardness of 60 to 90 (Shore A) mixed with polyethylene fibers is particularly preferred. For polishing silicon wafers, it is recommended to continuously supply water with an acidity value of 9 to 12 (especially 10 to 11), including 1 to 10% by weight (particularly 1 to 5% reset ratio) in water. The polishing fluid and polishing pressure of S i 〇 2 are preferably from 0.05 to 0.5 bar, and more preferably from 0.1 to 0.3 bar. The removal rate of Shi Xi is preferably 1.5 micrometers / minute, and more preferably 0.4 to 0.9 micrometers / minute. When removing polished semiconductor wafers from the lower polishing disc, it is best to place the semiconductor wafers on a standard processing stand and further process them so that their surfaces are oriented correctly in subsequent processing steps. Compared with the conventional double-sided polishing (where the semiconductor wafer is polished with its front side facing up), if the holder containing the semiconductor wafer is configured to rotate 180 °. , Try to avoid the need to rotate the semiconductor wafer by 180. . This work can be achieved by manual unloading or robotic unloading. This type of work is also possible when mounting a semiconductor wafer on a lower polishing disc.

The polished semiconductor wafer can be removed from the lower polishing disc manually or by means of an automatic moving (removing) device; in both cases, a vacuum suction device is preferred. German patent DE 1 9 958077 A1 (page 6, lines 23 to 30) describes a suitable vacuum suction device. After being removed from the polishing disc, the semiconductor wafer is then sent into a liquid bath (especially water-based

1244691 V. Description of the invention (8) Better in the bath). In this way, it can effectively prevent the polishing abrasive from drying out and prevent the vacuum suction appliances or (general name) removal equipment from forming a mark. After the green polishing process is completed, any attached polishing fluid is cleaned from the silicon wafer and the wafer is dried. Depending on its further use, the front side of these wafers may need to be final polished in accordance with existing techniques, such as using a soft polishing cloth and with an alkaline polishing fluid containing Si02 as the main component. Experimental examples: The users of the following experimental examples and comparative examples are a commercially available, AC 20000 = 2 type double-sided polishing machine, produced by Peter, Waters, Rendsburg, Germany). _ This polishing machine is equipped with five stainless steel carrier discs with a polished surface and a thickness of 72 microns. Each carrier disc has six circles with a diameter of 20.5 mm and a cutting frame. The cutting frames are equidistantly arranged on a circular path and lined with a layer of polyvinylidene chloride. Each batch of the machine can simultaneously polish 30 silicon wafers with a diameter of 200 mm. The upper and lower polishing discs are coated with a commercially available polishing cloth made by Rodel Corporation under the trademark 2 called SUBA 50, having a hardness of 74 (Shore A), and reinforced with polyethylene fibers. The polishing cloth taut on the lower polishing disc has a 3-slip surface; the surface of the polishing cloth taut on the upper polishing disc is made by pressing, with a visibility of 1.5 mm and a depth of 0.5 mm, A checkerboard pattern formed by partially annular grooves, and the arrangement pitch of these grooves is 30 mm. _ Comparative Example Always place 30 Shixi wafers with an etched surface and a diameter of 2000 μm into the cutting frame of a carrier tray with the front side always. During the polishing process, water-based polishing abrasives (Levasi 丨 200) were continuously supplied.

1244691

, Produced by Bayer Corporation, Leverkusen, Germany), its fixed s0 02 solid stem with a weight ratio of 3.1% and its acidity value is set at 11.4 by adding potassium carbonate and potassium hydroxide . . The polishing process was carried out under a pressure of 0.2 bar and a temperature of the upper and lower polishing discs totaling 38 C, and its material removal rate was 0.58 micrometers / minute. The silicon removed from each side of the wafer is 5 microns. (2) After the thickness of the polished wafer reaches 725 m, the supply of the polishing abrasive is terminated, and the supply of the stopper is replaced for 2 minutes. The stopping agent used is a 1% by weight aqueous solution of Glanzox 3600 manufactured by Fujimi Corporation of Japan.之后 After the stop step is terminated ', the device is opened, and the silicon wafer in the carrier tray is completely wetted by the stop liquid. A commercially available, Peter Walters pick-up station is used to transport the silicon wafers into a frame located in a water bath. After that, the Shixi wafers are dried in a batch cleaning equipment. The bathing sequence of this equipment is: tetramethylammonium hydroxide / ¾¾; HF / HC1; ozone; HC1 and a commercially available baking oven. Dry the device and operate in accordance with Marangani principles. The nanometer phase system of the cleaned wafer was measured on a ADE SQM CR83 device using a measurement field of 2 mm x 2 mm (HCT 2 > < 2) and 10 mm x ίο mm (HCT 10 X 10). A total of 1,96 8 silicon wafers were polished 'and their nanophases were subsequently identified. Experimental Example In a manner similar to the comparative example, a total of 2 157 silicon wafers with an etched surface and a straight blue orchid of 200 mm were processed. The only difference from the comparative example is that the Shi Xi wafer, which is placed in a carrier disc cutting frame, has its front side facing down 'and is polished in this direction. The results of the statistical analysis of the obtained nano values are shown in the table.

1244691 V. Description of the invention (10) Comparative example: 19 6 8 silicon wafers Experimental example: 2157 silicon wafers measurement field HCT 2x2 HCT 10x10 HCT 2x2 HCT 10x10 Average 18.50 40.48 15.24 33.06 Standard deviation 4.87 9.65 2.06 5.66 If this The silicon wafer is polished in a face-down manner, and the comparison shows that the nano-phase of the silicon wafer has been greatly improved for the measurement fields of two sizes. ❿

Page 13 1244691 Schematic description There is no schema for this application. # 11111 Page 14

Claims (1)

1244691 VI. Application Patent Scope 1 · A method for simultaneously polishing the front and back of a semiconductor wafer between two rotating polishing discs covered with a polishing cloth with a polishing fluid. The polishing cloth for the lower polishing disc has a The smooth surface and the surface of the polishing cloth of the upper polishing disc are separated by grooves. The semiconductor wafer is located in a carrier disc cutting frame and fixed on a defined geometric path. During the polishing process, the semiconductor wafer The front side is in contact with the polishing cloth of the lower polishing disc, and during the polishing process, the back side of the semiconductor wafer is in contact with the polishing cloth of the upper polishing disc. 2. The method of claim 1 in which the semiconductor silicon wafer is transferred to a water bath by means of a vacuum suction device after the front and back surfaces are polished simultaneously. 3. The method of claim 1 or 2 in which the front surface and the back surface are polished simultaneously, and then the front surface of the semiconductor wafer is subjected to final polishing. Page 15