WO2003072329A1

WO2003072329A1 - Automated control of wafer slicing process

Info

Publication number: WO2003072329A1
Application number: PCT/IT2002/000126
Authority: WO
Inventors: Carlo Zavattari; Ferdinando Severico
Original assignee: Memc Electronic Materials, S.P.A.
Priority date: 2002-02-28
Filing date: 2002-02-28
Publication date: 2003-09-04

Abstract

A method and system for managing a sequence of processing operations performed at a plurality of stations for producing semiconductor wafers from silicon ingots. A server computer (10) stores processing information relating to one or more of the stations (70, 95, 120, 145, 170) and correlates the processing information to crystal information for a selected ingot. The crystal information indentifies the selected ingot (66) and relates to desired characteristics of wafers to be produced from the selected ingot. The crystal information is also correlated to the processing information based on location of the selected ingot in the sequence of processing operations performed by the stations. The server computer automatically initializes the processing operations performed by the stations based on the correlated crystal and processing information to produce the wafers substantially in accordance with the crystal information for the selected ingot.

Description

AUTOMATED CONTROL OF WAFER SLICING PROCESS

BACKGROUND OF THE INVENTION

The present invention relates generally to producing silicon wafer manufacturing processes and, particularly, to the automatic management of processing operations, which are used to produce semiconductor wafers, solar cells, and the like.

Most processes for fabricating semiconductor electronic components start with monocrystalline, or single crystal, silicon in the form of wafers. In general, semiconductor wafers are produced by thinly slicing a single crystal silicon ingot. After slicing, each wafer undergoes a number of processing operations to shape the wafer, reduce its thickness, remove damage caused by the slicing operation, and to create a highly reflective surface. Typically, the different steps of the wafer slicing, shaping, and testing processes are performed at different locations within a semiconductor wafer manufacturing plant. For this reason, ingots and then wafers must be transported facility-to-facility within the plant .

For a number of reasons, including quality control, wafer manufacturers desire to track wafer lots as they travel facility-to-facility within a plant and to record process data on each lot cut from a particular ingot through final packing. In this regard, a single lot of wafers may be loaded into multiple cassettes for transport and each cassette, loaded with wafers cut from a specific ingot, may travel independently of the other cassettes in the same lot. U.S. Patent No. 6,330,971, the entire disclosure of which is incorporated herein by reference, describes a system for tracking wafer lots that provide improved automatic identification, tracking, and data collection, as well as custom protocol interfaces with designated equipment.

Notwithstanding these improvements, presently available manufacturing processes are complex, which makes them prone -to operating and procedural errors . For instance, procedural errors in the ingot orientation alignment process may result in an ingot being incorrectly mounted on its carrier, which can lead to wafer breakage or chipped ingots during the slicing process. Moreover, operator errors may result in an ingot being loaded onto a slicing machine that is not capable of producing wafers within the particular specifications requested by a customer. In either case, such errors result in reduced yield and increased production time. For these reasons, further improvements in silicon wafer manufacturing processes are desired to achieve integrated control of the processing operations in addition- to monitoring the progress of wafer production.

BRIEF SUMMARY OF THE INVENTION

The invention meets the above needs and overcomes the deficiencies of the prior art by providing full automatic management of the various operations to slice silicon rods to obtain wafers for use in electronics, solar cells, and like applications. The invention manages a complete slicing operation, including the sequence of single operations such as crystal orientation, silicon rod mounting on a metal ingot holder, slicing, slurry preparation and control, wire saw set up, and wafer mechanical parameter measurement. The implementation of the integrated, automated system of the invention significantly reduces operating and procedural errors and, thus, provides cost savings.

Briefly described, a method embodying aspects of the invention manages a sequence of processing operations performed at a plurality of stations for producing semiconductor wafers from silicon ingots. The method includes storing processing information at a server computer. The processing information relates ^' to one or more stations for performing processing operations to produce semiconductor wafers from one or more silicon ingots. The method also includes identifying a selected one of the ingots to be sliced into wafers and correlating, by the server computer, crystal information for the selected ingot to the stored processing information. In this instance, the crystal information identifies the selected ingot and relates to desired characteristics of wafers to be produced from the selected ingot . The crystal information is also correlated to the processing information based on location of the selected ingot in the sequence of processing operations performed by the stations. The method further includes automatically initializing, by the server computer, the processing operations performed by the stations based on the correlated crystal and processing information to produce the wafers substantially in accordance with the crystal information for the selected ingot.

In another embodiment, a system of the invention includes a plurality of stations each performing at least one processing operation for producing semiconductor wafers from silicon ingots. The system also includes one or more local computers associated with the stations and a server computer connected to the local computer via a data communication network. The server computer stores processing information relating to one or more of the stations and correlates crystal information for a selected one of the ingots to be sliced into wafers to the stored processing information. The crystal information identifies the selected ingot and relates to desired characteristics of wafers to be produced from the selected ingot . The crystal information is also correlated to the processing information based on location of the selected ingot in a sequence of processing operations performed by the stations. Further, the server computer initializes the processing operations performed by the stations based on the correlated crystal and processing information to produce the wafers substantially in accordance with the crystal information for the selected ingot.

Alternatively, the invention may comprise various other methods and apparatuses . Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the integration between a computer information system and a data carrier system of a preferred embodiment of the invention.

FIG. 2 illustrates the integrated system for controlling processing operations of a preferred embodiment of the invention. FIG. 3 illustrates the operation of the integrated system according to a preferred embodiment of the invention.

Corresponding reference characters indicate corresponding parts throughout the drawings .

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, particularly FIG. 1, an exemplary block diagram illustrates components of an integrated control system 10 according to a preferred embodiment of the invention. In general, the present invention achieves automated management of processing operations involved in the manufacturing of silicon wafers from ingots and/or as cut wafers. In this regard, the system 10 provides a full integration between a computer information system 20, a plurality of operating stations 25, a carrier data communication system 30, and process operators .

The control system 10 provides full automatic management of the various operations in slicing silicon rods to obtain wafers for electronics applications, solar cells, and the like. It is to be understood that the invention operates independently of wafer diameter and shape and is applicable for use with industrial machines and equipment, such as those involving wire saw or inner diameter blade technologies for slicing a variety of materials. In a preferred embodiment of the invention, control system 10 manages a complete slicing process to prepare single crystal silicon as wafers for electronic featuring. The process includes a known sequence of single operations (e.g., crystal orientation, silicon rod gluing on a metal ingot holder, slicing, slurry preparation and control, wire saw set up, and wafer mechanical parameter measurement) performed by various equipment (e.g., x-ray station, adhesive station, wire saw machines, slurry preparation tank, devices to measure the physical properties of the slurry, and devices to measure the mechanical parameters of the wafers) .

In one embodiment of the invention, control system 10 manages process operations starting from silicon monocrystal or polycrystal rod slicing involving wire saw technology. The sequence of operations include ingot crystallographic orientation by an x-ray device (i.e., employing the Bragg principle) ; ingot mounting on a metallic ingot holder prior to loading the rod on the wire saw machine; ingot loading into the machine and wire saw set up (i.e., consumable regeneration and set up of the slicing process and parameters) ; slicing slurry preparation and physical parameter check (e.g., density and viscosity); demounting and cassette loading after slicing wafer; mechanical wafer characteristic check (e.g., thickness, maximum thickness variation (TTV) , wafer deformation (warp) , and surface roughness) ; and automatic control chart creation (SPC) for the mechanical wafer parameters.

Still referring to FIG. 1, the computer information system 20 provides, for example, applications for operator interfaces, product work-in-process, container inventory, scheduling container moves, interlocking equipment, manufacturing recipes, history, and reporting as a function of data gathered by the communication system. The carrier data communication system 30 includes data capture devices, control modules, power supplies, communication hardware, and software to buffer the captured data. In this instance, the data capture devices employ radio frequency identification (RFID) tracking technology for capturing data from passive data carrying device. The operating stations 25 are, for example, x-ray machines, saws, grinders, polishers, thickness sorters, or any other machinery used in the manufacturing process of silicon wafers .

FIG. 1 shows one embodiment of computer information system 20 in block diagram form. A data communication network 35 transfers data to and/or receives data from at least one local server 40. For example, the network 35 is a wide area or local area network permitting communication between a number of computing devices connected via the network. Those skilled in the art are familiar with processing plant networks, such as network 35. As shown in FIG. 1, the local server 40 is connected to network 35.

Preferably, local server 40 is configured to transfer data to and/or receive data from a plurality of local operating station personal computers (PCs) 45. In this embodiment, the data represents processing information related to silicon wafer production. The local server 40 is described in greater detail below. Referring further to FIG. 1, the carrier data- system 30 preferably includes an RFID controller, embodied by a configurable data collection reader 50 and at least one antenna 55. The reader has a radio frequency (RF) module that transmits RF energy via the antenna 55. A relatively small FM radio transponder, or tag 60, mounted on a carrier 65 for carrying wafers or an ingot, for example, receives the transmitted RF signal and generates an appropriate reply signal. The reader 50 receives the reply signal via the respective antenna 55. In this instance, the reply signal includes a unique identification (ID) code for identifying the ingot or the wafers carried by the particular carrier 65. Preferably, depending on factors such as the size of the manufacturing plant, the carrier data system 30 includes a plurality of readers 50, and each reader supports a plurality of antennas 55.

The tag 60 is a receiver/transmitter device that automatically transmits signals when it receives the proper interrogation. In this instance, tag 60 receives the RF interrogation signal generated by reader 50 when the carrier 65, to which it is affixed, moves within range of antenna 55. The RF signal transmitted by antenna 55 excites tag 60 into transmitting the stored information back to antenna 55. The stored information may include a unique carrier address,, lot number, plant order, current and next process operation, product count, and other information valuable to -he manufacturing process. In this manner, reader 50 and antenna 55 work -together to generate, transmit, receive and read radio frequency transmissions. Although described in connection with carrier 65, it is to be understood that tag 60 may also be embedded in or attached to other items used in the manufacturing process .

RFID reader 50 uploads the information that it scanned from tag 60 to the local PC 45. Preferably, local PC 45 is linked to one operating station 25 and to data network 35 of the wafer processing facility via local server 40. Local PC 45 communicates with reader 50 and processes information related to inventory tracking, mix prevention, work-in-process, automated process control, and the like. Furthermore, local PC 45 is configured to download data via antenna 55 for programming tag 60. FIG. 2 illustrates an exemplary manufacturing facility controlled by the system 10. The facility has, for example, six exemplary operating stations 25, namely, x-ray, - adhesive, slicing, slurry, demount, and measurement. It is to be understood that the wafer manufacturing plant for which system 10 provides integrated control may include a plurality of x-ray machines and/or saws as well as various processing machines .

Referring further to FIG. 2, an ingot 66 first arrives at x-ray station 70 to be oriented for slicing. The ingot 66 must be "slice oriented" in order to properly slice the ingot into wafers. In this instance, x-ray station 70 defines an orientation error between crystallographic and mechanical planes, using the Bragg refraction theory. Under conventional processes, an operator uses this error to properly align the ingot on an ingot support fixture or holder 75. The integrated control according to the invention first involves collecting characteristic data for ingot 66 directly from a database 76 associated with the manufacturing facility network 35. An operator using, for example, a bar code system to enter or scan the ingot's lot number preferably accomplishes this during the crystallographic orientation measurement step. The lot number may be identified on a paper documentation traveler that accompanied ingot 66 from a previous processing step (e.g., cropping) . The database 76 associated with the plant network 35 stores all the ingot available data to get them available for ingot processing during mounting, slicing, etc. The data includes ingot length, diameter, customer requirements, and wafers warp limit value, thickness target, orientation limits, etc. In a preferred embodiment, the x-ray station is linked with local server 40, which connects the local operating area with the external world and is connected to a local PC 80 associated with an x-ray machine 85. Local server 40 uses the lot number entered or scanned by the operator to query a general database 86 to retrieve recipe and/or processing information for that particular lot number. ^■ Among other things, local server 40 stores data in the database 86. The local server 40 then transfers the retrieved orientation data contained in the recipe, such as the appropriate reference plane, to the local PC 80 associated with x ray machine 85. The x-ray PC 80 uses the measurement data collected by x-ray machine 85 along with the recipe's orientation data to determine the orientation error and to calculate a suitable correction. Further, the recipe insures that the measurement steps are executed according to a predetermined sequence and allows the operator to proceed only if each step is performed correctly. After x-ray station 70 performs the crystallographic orientation measurement, the process proceeds to an adhesive station 95 for mounting ingot 66 on the holder 75. Holder 75 assists in transporting ingot 66 and is used for loading ingot 66 onto a conventional slicing machine (e.g., I.D. saw, wire saw) . In one embodiment, the ingot support fixture, or holder 75, has a mount to which the ingot is bonded during slicing. The holder 75 positions the silicon ingot 66 to accurately align an orientation of its crystalline structure relative to the saw's cutting plane. A rack typically extends upward from holder 75 and a motor- driven pinion engages the rack for advancing and retracting the ingot 66. In other words, holder 75 is moveable in translation to bring the ingot into contact with the cutting surface of the saw. The ingot holder 75 is, for example, a stainless steel support plate. It is very important that the ingot be held firmly during ^'slicing. In this instance, the silicon ingot is firmly affixed to the holder 75 at the adhesive station 95.

Referring again to FIG. 2, a preferred embodiment of the integrated system 10 controls adhesive station 95. The system 10 includes an antenna 100, a reader 105, a local PC 110 associated with an adhesive machine 115.

To insure that the ingot is properly attached to the holder 75, an intermediate "gluing" step is performed where ingot 66 is, for example, mounted on a beam (not shown) using an epoxy resin. The beam is then mounted firmly on the holder 75. The "relative" gluing steps between ingot 66 and holder 75 provide an operator the ability to align the ingot for slicing such that any crystallographic orientation errors may be corrected.

The adhesive station 95 is preferably equipped with a numerical control, which is set to the orientation values transferred from the server 40. As described above, server 40 receives crystal data (e.g., diameter, length, warp limits, lot number) from the plant network 35. The server 40 preferably receives orientation measurements, written to a .TXT file, from the local PC 80 associated with x-ray station 70. According to the invention, server 40 transfers data from plant network 35 and ingot orientation parameters from x-ray station 70 to adhesive station 95 for correcting any orientation errors that otherwise might have occurred when mounting the ingot 66 on the holder 75.

One technique for slicing wafers involves coupling two ingots 66 together at the adhesive station 95. Commonly assigned International Publication WO 01/91981, the entire disclosure of which is incorporated herein by reference, discloses a wire saw process for slicing multiple ingots. In a preferred embodiment of the invention, server 40 transfers coupling information to the adhesive station PC no along with the orientation data. The coupling information is preferably transferred to the adhesive station PC 110 via a bar code reader or the like to ensure mounting the ingots 66 with the correct orientation correction and in the correct sequence. For example, the adhesive step information is added to the original data string from server 40, forming a single string containing lot data, orientation data, and coupling data. An arrangement of a radio frequency identification tag 116 associated with the ingot holder 75 and the antenna 100 in communication with server 40 may be used to communicate the tag identification number. Through the adhesive station antenna 100 and the ingot holder tag 116, the server 40 combines the string with the tag identification number. Preferably, the combined string is referred to as the ingot holder tag number. Further, in a preferred embodiment, system 10 provides a visual and/or audible indication of whether ingot 66 has been properly aligned. This integrated control system 10 facilitates the correct "gluing" of silicon crystals and the ability to couple rods for a multiple ingot slicing process and for a multiple lane slicing process, thereby maximizing the coupling among crystals and optimizing the slicing lengths.

During the "gluing" operation, local server 40 decides whether and how to couple ingots 66, on which slicing machine to process the coupled or individual ingots 66, and the appropriate slicing recipe. This information is transferred from local server 40 to the adhesive station PC 110, and is further transferred to tag 116 mounted on holder 75 via reader 105 and antenna 100. The local server 40 then sends the same information to a slicing or saw station 120 via a local PC 125 associated therewith.

Known wafering processes include slicing an ingot into individual wafers with a cutting apparatus, such as a wire saw. The saw slices the ingot in a direction normal to the ingot's longitudinal axis to produce as many as several hundred thin, disk-shaped wafers. In a typical wire slicing operation, a reciprocating wire formed into a web contacts the ingot while a liquid slurry containing abrasive particles (e.g., grains of silicon carbide) is supplied to the contact area between the ingot and the

5 wire. As the wire rubs the abrasive particles in the slurry against the ingot, the saw removes silicon crystal and gradually slices the ingot. The wire saw provides a gentle mechanical method useful for cutting silicon crystal, which is brittle and more likely damaged by other

1G types of saws (e.g., conventional internal diameter saws). U.S. Patent Nos . 5,735,258, 5,827,113, and 6,006,736, the entire disclosures of which are incorporated herein by - reference, disclose wire saw apparatus for slicing silicon wafers .

15 Referring again to FIG. 2, system 10 according to the invention also provides integrated control of the slicing operation. The slicing station 120 includes the local PC 125, an antenna 130, a reader 135, and a slicing machine 140.

2C In a preferred embodiment, local server 40 automatically manages two saw-ingot coupling operations during the adhesive operation: the coupling operation of an individual ingot to a slicing machine; and the coupling operation of multiple rods (i.e., for multiple slicing or t multiple lanes slicing) to a slicing machine.

To manage saw-ingot coupling, the slicing process is linked to the silicon material specifications (e.g., rod diameter, single crystal, multiple crystals, parallel lane rod slicing, wafer thickness) . This means that for any

X "gluing" process, rod diameter, and wafer thickness, an appropriate recipe is created to define the slicing parameters and the particular machine set up. The parameters may include wire amount, slurry regeneration rate, wire speed, and table feed rates. The machine set up

X includes, for example, adjusting or selecting wire tensioning pulley run out, slurry type, wire guide and bearing box cooling temperature, temperature profile along the cut, density and viscosity limit values for the slurry, wire tension and speed profile, slurry type, maximum slicing crystal length, and wire guide pitch to define the

6 wafer thickness.

In other words, to properly load the ingot holder 75 on the slicing machine 140, the server 40 must combine the characteristics contained in the ingot holder string with the characteristics of each slicing machine (e.g., web

*,(j length, warp capabilities, twin or single) . When the characteristics match properly, the server 40 assigns the ingot holder 75 to the slicing machine 140. As such, the particular ingot holder 75 is allowed to be loaded only on the particular slicing machine 140 to which it has been 5 assigned. Server 40 sends the assigning information to local PC 125 associated with the slicing machine 140 and, when the ingot holder 75 approaches the antenna 130, a crosscheck is made. Based on the string information, slicing machine 140 loads the proper slicing recipe 0 retrieved from database 76 and all of the parameters required to properly slice ingot 66 (e.g., slurry regeneration and pulley change) .

In addition, server 40 provides recipe generation; maintains a saw diary and archive collection; and provides 5 timer definition and collection. Preferably, software for remote connection to each saw together with the software installed on each saw's local PC 125, such as PCAnywhere networking software, allows a remote connection via password to authorized people. The connection level is 0 important so these people can fully interact with the saws and the server to change recipes, saw parameters, and the like. It is also possible to observe slicing machine behavior in real time. The access is possible from any remote PC using a modem to connect to the plant network 35. 5 in the embodiment of FIG. 2, antenna 130 receives information from and transmits information to tag 116, which is attached to holder 75, The tag 116 is written (i.e., coded) with processing information that local server 40 transferred to tag 116 via the adhesive station antenna 130. After tag 116 is coded, the holder 75 becomes unequivocally identified. It is contemplated to use a read-only tag in which the tag has a number that identifies it unequivocally and, in this instance, all of the string records and connections are made on the server even though it seems that the tag itself has the string on it.

The assigned slicing machine 140 receives the same code information previously transferred to tag 116, and a local PC 125 associated with slicing machine 140 further _. retains code information regarding current performance capabilities of the slicing machine 140. When the holder 75 is loaded on an assigned slicing machine 140, the tag 116 passes within the reception range of antenna 130 associated with slicing machine 140, and the two recorded codes are compared. As stated above, if the codes match, slicing machine 140 initiates the slicing operation. This automatic verification step insures that the assigned slicing machines are properly equipped and set for the correct process. For instance, in the event the saw's operating capability changes prior to loading, such as warp degradation, the code on the slicing machine 140 is changed. Thus, when ingot 66 approaches slicing machine 140, the code information stored on tag 116 does not match what is written on the slicing machine 140, and the run is forbidden. However, the operation can be forced under password. This communicative process can be repeated for other processing operations.

In a preferred embodiment, the local PC 125 associated with slicing machine 140 receives a slicing recipe and automatically generates a statistical process control (SPC) chart for the warp performance of that particular slicing machine 140. This chart defines the maximum warp value that can be processed on the slicing machine 140 without creating warp values outside of the customer's specifications and/or generating scrap. For example, if the SPC reports a warp performance of X microns for a particular slicing machine, when the customer requests of a

5 warp value less than X microns, an ingot cannot be processed on the particular slicing machine because of the risk of cutting wafers with an unacceptable warp value. Thus, through local PC 125, the SPC chart transfers the process limits of a particular slicing machine 140 to the

10 recipe to insure that the customer request is within the machine's capabilities. The slicing recipe is included in the local PC 125 associated with slicing machine 140 through the common data base 86 shared among slicing machines 140 and local server 40. Thus, the local server

15 40 "knows" the recipe on each slicing machine 140, and

"knows" which recipes are allowed on each slicing machine 140. Further, the local server 40 knows which cut is in progress on each slicing machine 140.

Considering all the previous information (both product

20 and process and performances) during the "gluing", the server 40 decides how to couple the rods (if coupling is required) , how to couple the rods to the slicing machine 140, assigning the correct slicing recipe based on all the characteristics. The whole information is transferred from

25 server 40 to adhesive station 95, which transfers the same information to the tag 116 mounted on holder 75 through antenna 100 associated with adhesive station 95. The server 40 sends the same information to the slicing machine 140 devoted to slice the rods of interest. This double

•^ information transfer facilitates the data comparison for slicing machine/ingot assignment verification process as described above.

In another preferred embodiment, the slicing machine/ingot assignment can be forced, for example, under 5 a password and with a driven path. Thus, in addition to the one or more slicing machines proposed for assignment by local server 40, at least one additional slicing machine 140 can be assigned through forcing. This option provides the ability to assign slicing machine 140 using a non- standard process, such as in -case of test trials or temporary process changes. Furthermore, the forcing function can occur either before or after the slicing machine-ingot assignment by local server 40. The ability to force after the saw-ingot assignment- further allows automatic correction in the event that the assigned slicing machine's characteristics change during the time between gluing and saw loading. For example, a machine's characteristics may change during the time required for the adhesive to cure, but the machine may still be desired for processing. After ingot slicing, the process forwards the metal support fixture to a demounting station 145 to remove the as-cut wafers from holder 75.

Referring further to FIG. 2, integrated system 10 also controls a demounting operation. The demounting station 145 includes an antenna 150, a reader 155, a local PC 160, and a demounting machine 165. The demounting machine 165 loads the as-cut wafers into a cassette 166 having a tag 167 embedding therein or affixed thereto.

The antenna 150 communicates with associated demounting operating station 145. Holder 75 is loaded on the demounting machine 165, and antenna 150 detects tag 116, which transmits the information of the lot contained in the code. After the sliced ingot 66 is loaded on the demounting machine 165, the function of tag 116 on holder 75 is complete. If desired, the recorded code identifying the tag 116 to the holder75 maybe deleted from the memory of local server 40. Thus, when holder 75 returns to the adhesive station 95, server 40 detects an obsolete code on the tag and overwrites it with a new one. This begins a new cycle. After the demounting operation, the wafers are collected in the cassette 166. Cassettel66 is used to transport the wafers to the remaining processing operations. The tag 167 is also connected to cassette 166,

5 and when it moves within the transmission range of antenna 150 associated with demount station 145, the code information is transferred from the local demount station PC 160 to^' tag 167 On cassette 166 via antenna 150. Accordingly, as with the tag 116 on holder 75, tag 167 on

•J cassette 166 contains processing information relating to the lot number of the wafers contained in a given cassette.

FIG. 2 also illustrates integrated control of a parametric measurement operation by system 10. After demount the wafers are placed in cassettes 166, and washed,

15 and a sample of these wafers are forwarded to a mechanical parameter measurement station 170. The integrated system comprises an antenna 175, a reader 180, a local PC 185, and a measurement device 190. The antenna 175 communicates with the measurement station 170. The cassette 166 is

20 loaded onto the wafer mechanical parameter measurement device 190, and by positioning cassettel66 within the reception range of antenna 175, the processing information from the tag 167 is transferred to the local measurement device PC 185. ^• The processing information includes, for £ example, the limits of the wafer's mechanical parameters

(e.g., warp, TTV, roughness) as specified by the customer.

After the information is transferred, measurement device PC 185 generates and displays a string containing all of the lot information. The only information that

"-r, requires manual entry is the amount of wafers in the lot and the sample amount to be measured on the device. The measurements of the sample wafers are taken as representative of the entire lot. After the sample wafers are processed on the measurement device 190, the collected parametric measurement data (e.g., average value, standard deviation, etc.) of the sample wafers is ultimately recorded on the measurement device PC 185. The measurement data of sample wafers is compared with the customer's requirements, which were previously transferred to measurement device PC 185. In another preferred embodiment, using the previously collected slicing and measurement data, the measurement device PC 185 is configured to create and update control charts of each "mechanical measurement parameter associated with each slicing machine 140. Further, the measurement device PC 185 can be configured to transfer the updated control data to each slicing machine PC 125, in order to display the control charts on each slicing machine PC 125. This option facilitates real time feedback on the performance of a particular slicing machine 140. After the data is transferred to the slicing machine 140, the slicing machine PC 125 transfers the information to server 40 to delete the code written on the tag 167. Thus, when cassette 166 re-approaches demounting station 145, the code on tag 167 is obsolete and the demounting station antenna 150 can overwrite the obsolete code with a new code. In this way, the lot is followed from its entrance into in the slicing area until it exit from the area after the parameter measurement on the sample wafers . At this step, the lot is sent in another manufacturing area in which the wafers are treated to remove the surface damage due to slicing. The same integrated and automatic management can be introduced in these areas, and they can be linked with the other areas. This would provide the ability to track all the information about the product, and can be useful for either internal control, customer inquiries and/or troubleshooting.

Referring now to FIG. 3, an exemplary flow diagram illustrates operation of system 10 according to a preferred embodiment of the invention. Beginning at 302, the plant network provides the x-ray station with crystal orientation set values via bar code reading. At 304, the plant network communicates crystal lot and specification number and crystal parameters, such as warp limits, wafer thickness, and crystal length to the server. The x-ray station, at 306, determines orientation measurements for correction and communicates this information to the server for use by the adhesive station. Proceeding to 308, the server links the information from 304 with the information from 306. The server at 310 generates a definition of rod coupling for multiple and twin mounts, if desired. The adhesive station and the server communicate at 312. In particular, by using a bar code reading system, "gluing" parameters, such as orientation angle and crystal length are retrieved. Moreover^ the bar code system transfers and links the retrieved data with the ingot holder tag number and the lot string on the server in order to facilitate saw assignment. At 314, the ingot holder is ready to be loaded on saw(s) with appropriate flag and, at 316, the server -couples or assigns the ingot holder and saw. Proceeding to 318, the server communicates information to the saw for the coupling followed by 320 for comparison between the string on the server correlated to the tag identification number and the information on the saw to allow the loading. At 322, the operator can interact with the server to force loading if the desired saw does not match the saw as assigned at 312. In a conventional wafer manufacturing process, a fluid dispensing system transports slurry from a nearby slurry container and dispenses it onto the ingot at the saw's cutting surface. A portion of the slurry then moves with the wire, for example, into a contact area between the wire and the ingot where the silicon crystal is cut. The server 40 manages another important operation: slicing slurry preparation. This operation is not connected with the previous steps, even though it is part of the wire saw area automation. The slurry preparation area is comprised of several tanks in which the abrasive powder is properly mixed with the suspending agent (liquid) . Preferably, every tank is provided with an infra red sensor to determine an amount of slurry 205, a propeller with a relatively large shaft and wings to mix the suspension, and a hopper to properly distribute the power in the tank before mixing. The liquid is pumped from the storage tank to the slurry preparation tank through a distributing central system and a sequence of electro-valves. The powder comes from paper bags and is dropped in the tank manually, for example. 0 The server 40 manages both the slurry preparation steps and the slurry usage for the saws. It records the slurry level in each tank and, when the level in one tank goes below the minimum set level, a new slurry preparation begins. Server 40 tells the operator if the pump to pump 5 the liquid in the tank is in place in the storage tank. If so, server 40 gives the input to pump a certain amount of liquid in the right preparation tank, opening and closing the appropriate valves. If the liquid from the storage tank is not enough to fill up the preparation tank, server 0 40 detects it through the flowmeter set on the pump. In this case an alarm (e.g., a buzzer) calls the operator to change the empty storage tank with a full one. After that the operation goes on until all the required liquid is pumped in the preparation tank. With the step completed, b the server 40 tells the operator the amount of powder to add and the way to do it . The mixing rule depends on the abrasive and liquid kind. After the powder step, the operator gives the confirmation of the preparation procedure end. Server 40 also defines the mixer speed and It tunes the speed depending on the phase of operation (e.g., in the preparation phase or in the mixing phase waiting for the usage) .

After a fixed time in which the slurry 205 is properly and uniformly mixed, it is necessary to check the slurry c physical characteristics (density and viscosity) . To do that, every tank is connected to a measurement device (one for all the tanks) through a pipeline, a pump and a valve system. The device includes a viscometer and a flowmeter (same devices equip each wire saw machine) , a valve and pipe system to lead the liquid from the tank to pass through the two devices and to go back to the tank.

Furthermore, the instrument is equipped with a thermal sensor to measure the slurry temperature and a pump to return the slurry to the preparation tank. After the slurry has passed through the two devices, the real measurements are elaborated by the device PLC 210 to calculate the viscosity and density to the process temperature (such as the set up temperature on the wire saw), or to any desired temperature. In this way, the values transferred from PLC 210 to server 40 can be correlated and it is possible to build a chart; more over they can be correlated with the values obtained on the saw devices . In such a way control charts for every preparation tank are created, and every slurry preparation is tracked. It is to be understood that PLC 210 constitutes a local computer.

For both density and viscosity a validity range is set to properly slice silicon rods. If one of the two values is out of this range, the server 40 (following certain rules) tells the operator that the slurry preparation is not completed and that he has to add more powder or liquid to set the viscosity and density values in the range. After the preparation correction, and after a certain mixing time, the measurement is made once again, and the correction goes on until the values are both correct. After that, server 40 tells the operator that the slurry preparation has been successfully completed; then server 40 activates a green signal, which means that slurry 205 can be safely used for slicing.

The measuring device is equipped with cleaning washing and piping drying system. The server 40 automatically activates the cleaning and drying procedures after the measurement and after the return of the slurry 205 in the preparation tank.

When introducing elements of the present invention or the embodiment (s) thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and

"having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A method for managing a sequence of processing operations performed at a plurality of stations for producing semiconductor wafers from silicon ingots, said method comprising: storing processing information at a server computer, said processing information relating to one or more stations for performing processing operations to produce semiconductor wafers from one or more silicon ingots; identifying a selected one of the ingots to be sliced into wafers ; correlating, by the server computer, crystal information for the selected ingot to the stored processing information, said crystal information identifying the selected ingot and relating to desired characteristics of wafers to be produced from the selected ingot, said crystal information further being correlated to the processing information based on location of the selected ingot in the sequence of processing operations performed by the stations; and automatically initializing, by the server computer, the processing operations performed by the stations based on the correlated crystal and processing information to produce the wafers substantially in accordance with the crystal information for the selected ingot.

2. The method of claim 1 wherein one of the stations comprises a saw station for performing a slicing operation to slice the ingot into wafers and wherein automatically initializing the processing operations includes assigning the saw station to the selected ingot based on the stored processing information for the saw station and the crystal information for the selected ingot.

3. The method of claim 2 wherein the processing information for the saw station includes slicing performance data and wherein assigning the saw station includes matching the slicing performance data for the saw station to the desired characteristics of the wafers to be produced from the selected ingot in the crystal information.

4. The method of claim 2 wherein the saw station has a local computer associated therewith and further comprising connecting the server computer to the saw station local computer via a data communication network and communicating assigning information to the saw station local computer from the server computer.

5. The method "of claim 4 further comprising verifying, by the server computer, the assigning information as the selected ingot approaches the saw station for slicing.

6. The method of claim 2 further comprising prohibiting slicing operations to be performed at the stations other than the assigned saw station.

7. The method of claim 6 further comprising permitting an operator to manually override the prohibiting of slicing operations to be performed at the stations other than the assigned saw station.

8. The method of claim 1 wherein one of the stations comprises an x-ray station for performing a crystallographic orientation operation to determine an orientation correction parameter for the selected ingot and wherein correlating the crystal information to the processing information includes linking the crystal information for the selected ingot to the orientation correction parameter for the selected ingot.

9. The method of claim 8 wherein one of the stations comprises an adhesive station for performing a mounting

5 operation to mount the ingot on an ingot support fixture and wherein automatically initializing the processing operations includes transferring the linked crystal information and orientation correction parameter for the selected ingot from the server computer to the adhesive

10 station to orient the selected ingot on the ingot support fixture for the mounting operation.

10. The method of claim 9 further comprising: identifying another selected one of the ingots to be sliced into wafers; 5 correlating, by the server computer, the crystal information for the other selected ingot to the processing information; automatically initializing, by the server computer, the mounting operation performed by the adhesive station 0 based on the correlated crystal and processing information to couple the selected ingots and to orient the coupled ingots on the ingot support fixture for the mounting operation. •

11. The method of claim 1 wherein each of the 5 stations has a local computer associated therewith and further comprising connecting the server computer to the local computers via a data communication network.

12. The method of claim 11 wherein automatically initializing the processing operations includes inputting C one or more setup parameters from the server computer to the respective stations via the local computers.

13. The method of claim ^'1 further comprising scanning a bar code associated with the selected ingot to collect the crystal information for the selected ingot.

14. The method of claim 1 wherein the crystal information includes one or more of the following: a lot number, a specification number, an orientation value, a specified warp limit, a specified wafer thickness, and a crystal length.

15. The method of claim 1 wherein correlating the crystal information to the processing information comprises writing a data string following at least one of the processing operations to combine the crystal information for the selected ingot with the processing information for the respective station that performed the processing operation.

16. The method of claim 15 further comprising storing the data string in a radio frequency identification tag associated with the selected ingot.

17. The method of claim 16 further comprising mounting the selected ingot on an ingot support fixture for transporting the selected ingot between at least two of the stations for performing the respective processing operations, said ingot support fixture having ^'the tag storing the data string mounted thereon, said data string further identifying the ingot support structure.

18. The method of claim 16 further comprising loading the wafers produced from the selected ingot into a cassette for transporting the wafers between at least two of the stations for performing the respective processing operations, said cassette having the tag storing the data string mounted thereon, said data string further identifying the cassette.

19. The method of claim 16 wherein at least one of the stations has a local computer associated therewith,

5 said local computer for the station being connected to the server computer via a data communication network, and

.further comprising: reading the data string from the tag via radio frequency signals when the tag is proximate the station; 10 communicating the data string to the server computer via the local computer for the station and the data communication network; communicating one or more setup parameters from the server computer to the station via the local computer for 15 the station and the data communication network in response to the data string read from the tag, said setup parameters initializing the processing operation performed by the station.

20. A system comprising:

20 a plurality of stations each performing at least one processing operation for producing semiconductor wafers from silicon ingots; one or more local computers associated with the stations; and

25 a server computer connected to the local computer via a data communication. network, said server computer storing processing information relating to one or more of the stations and correlating crystal information for a selected . one of the ingots to be sliced into wafers to the stored

^ processing information, said crystal information identifying .the selected ingot and relating to desired characteristics of wafers to be produced from the selected ingot, said crystal information further being correlated to the processing information based on location of the selected ingot in a sequence of processing operations performed by the stations, and said server computer further initializing the processing operations performed by the stations based on the correlated crystal and processing information to produce the wafers substantially in accordance with the crystal information for the selected ingot .

21. The system of claim 20 wherein one of the stations comprises a saw station for performing a slicing

10 operation to slice the ingot into wafers and wherein the server computer assigns the saw station to the selected ingot based on the stored processing information for the saw station and the crystal information for the selected ingot thereby initializing the slicing operation.

15 22. The system of claim 21 wherein the processing information for the saw station includes slicing performance data and wherein the server computer matches the slicing performance data for the saw station to the desired characteristics of the wafers to be produced from

20 the selected ingot in the crystal information for assigning the saw station to the selected ingot.

23. The system of claim 21 wherein one of the local < computers is associated with the saw station and wherein the server computer communicates assigning information to

25 the saw station local computer via the data communication network .

24. The system of claim 23 wherein the server computer verifies the assigning information as the selected ingot approaches the saw station for slicing.

b0 25. The system of claim 1 wherein one of the stations comprises an x-ray station for performing a crystallographic orientation operation to determine an orientation correction parameter for the selected ingot and wherein the^' server computer links the crystal information for the selected ingot to the orientation correction parameter for the selected ingot thereby correlating the crystal information to the processing information.

26. The system of claim 25 wherein another one of the stations comprises an adhesive station for performing a mounting operation to mount the ingot on an ingot support

10 fixture and wherein the server computer transfers the linked crystal information and orientation correction parameter for the selected ingot to the adhesive station to orient the selected ingot on the ingot support fixture for the mounting operation thereby initializing the processing

15 operations .

27. The system of claim 20 further comprising a bar code reader for scanning -a bar code associated with the selected ingot to collect the crystal information for the selected ingot.

20 28. The system of claim 20 wherein the crystal information includes one or more of the following: a lot number, a specification number, an orientation value, ^'a specified warp limit, a specified wafer thickness, and a crystal length.

ⁱ

29. The system of claim 20 further comprising a radio frequency identification tag associated with the selected ingot storing a data string written thereto following at least one of the processing operations to combine the crystal information for the selected ingot with the

30 processing information for the respective station that performed the processing operation.

30. The system of claim 29 further comprising an ingot support fixture on which the selected ingot is mounted for transporting the selected ingot between at least two of the stations for performing the respective processing operations, said ingot support fixture having the tag storing the data string mounted thereon, said data string further identifying the ingot support structure.

31. The system of claim 29 further comprising a cassette into which the wafers produced from the selected ingot are loaded for transporting the wafers between at least two of the stations for performing the respective processing operations, said cassette having the tag storing the data string mounted thereon, said data string further identifying the cassette.

32. The system of claim 29 further comprising a tag reader associated with at least one of the stations for reading the data string from the tag via radio frequency signals when the tag is proximate the station, said reader communicating the data string to the server computer via the local computer for the station and the data communication network and said server computer communicating one or more setup parameters to the station via the local computer for the station and the data communication network m response to the data string read from the tag, said setup parameters initializing the processing operation performed by the station.

33. The system of claim 20 wherein the stations include one or more of the following: an x-ray station for determining ingot orientation; an adhesive station for mounting the selected ingot to a carrier based on the determined ingot orientation; a slurry station for managing slurry preparation and usage; a slicing station for producing wafers from the selected ingot; a demounting station for removing the wafers from the carrier; and a measurement station for obtaining parametric data with respect to said wafers produced from the selected ingot.

34. A system for slicing silicon ingots comprising: a saw station for performing a slicing operation to slice a silicon ingot into wafers; a slurry station coupled with the saw station for performing a slurry operation to supply slurry to the saw -station during the slicing operation; a local computer associated with the saw station and a local computer associated with the slurry station; and a server computer connected to the local computers via a data communication network, said server computer storing processing information relating to the saw and slurry stations and correlating crystal information for the ingot to be sliced into wafers to the stored processing information, said crystal information identifying the selected ingot and relating to desired characteristics of wafers to be produced from the selected ingot, and said server computer further managing the slurry operation based on the correlated crystal and processing information to produce the wafers substantially in accordance with the crystal information for the selected ingot .