METHOD AND APPARATUS FOR DETERMINING MEASUREMENT FREQUENCY BASED ON HARDWARE AGE AND USAGE

Abstract: A processing line (10) includes a processing tool (20), a measurement tool (40), and an automatic process controller (50). The processing tool (20) is adapted to process articles (30). The measurement tool (40) is adapted to measure a characteristic of selected articles (30) at a measurement frequency. The automatic process controller (50) is adapted to change the measurement frequency based on a usage characteristic of the processing tool (20). A method for monitoring a processing tool (20) includes processing a plurality of articles (30) in the processing tool (20); measuring a characteristic of selected articles (30) at a measurement frequency; and changing the measurement frequency based on a usage characteristic of the processing tool (20).

Description: METHOD AND APPARATUS FOR DETERMINING MEASUREMENT FREQUENCY BASED ON HARDWARE AGE AND USAGE TECHNICAL FIELD This invention relates generally to semiconductor device manufacturing, and, more particularly, to a method and apparatus for determining measurement frequency based on hardware age and usage BACKGROUND ART The manufacture of most devices, such as semiconductor devices, requires a number of discrete processing steps to create the device For the example of semiconductor devices, a number of discrete steps are needed to produce a packaged semiconductor circuit device from raw semiconductor material The starting substrate is usually a slice of single crystal silicon referred to as a wafer Circuits of a particular type are fabricated together in batches of wafers called "lots" or "runs" The fabπcation process creates regular arrays of a circuit on the wafers of a lot During processmg, the individual wafers m a lot may go through individual processmg steps one at a time or as a batch At the completion of wafer processing, the wafers are tested to determine circuit functionality Later the wafers are sliced, the functioning devices are packaged, and further testing occurs prior to use by the customer Data gathered during the course of wafer processmg is used to diagnose yield problems and forms the basis of yield improvement efforts Such performance measurements include defect count measurements, thickness measurements (I e , indicative of deposition rate), and resistivity measurements, for example The number of defects is often predictable as a function of tool hardware life The resistivity and deposition rate also change with hardware life, and/or mamtenance history For much deposition equipment, defects are more probable when the tool is first put together and at the end of its life In a sputtering deposition tool, the source of metal to be sputtered is referred to as a target The target is depleted as sputtering is conducted, and, thus, the target is changed frequently The resistivity and/or deposition rate of the layer being deposited change slowly after a target change and after a wet clean In a chemical vapor deposition (CVD) tool, reactive gases are introduced into the processing chamber through a gas supply header, commonly referred to as a showerhead Over time, process materials and/or byproducts collect on the showerhead, eventually leading to degraded performance As the showerhead becomes obstructed, the deposition rate of the CVD tool decreases and becomes more erratic The gas supplied to the showerhead often passes through an in-line filter Over time, the filter may become obstructed, thus reducmg the amount of reactive gases it passes This reduction could also eventually cause a reduction in the deposition rate of the tool Current semiconductor processing techniques typically take performance measurements at a fixed rate (e g , every fourth lot processed in a tool) or by pre-assigning a fixed percentage of lots for measurement Because lots are not typically processed in a particular order, the percentage technique sometimes results in periods where multiple lots are measured consecutively, followed by peπods where no lots are measured To address the stability problem identified above, preventative maintenance tasks, such as cleanings, tool refurbishment, showerhead replacement, in-line filter replacement, and target replacement, are scheduled at intervals that are less than the expected time where the likelihood of instabilities increases These intervals, by nature, are conservative, and may result in the performance of the preventative mamtenance task before it is actually necessary Also, due to the limitations of the performance measurement intervals described above, degradation of the tool prior to the end of the preventative maintenance interval mav not be readily identified As a result defective wafers could be manufactured, necessitating costly re-work or scrapping of the wafers The present invention is directed to resolving one or all of the problems mentioned above DISCLOSURE OF INVENTION One aspect of the present invention is seen in a processmg line including a processing tool, a measurement tool, and an automatic process controller The processing tool is adapted to process articles The measurement tool is adapted to measure a characteristic of selected articles at a measurement frequency The automatic process controller is adapted to change the measurement frequency based on a usage characteristic of the processing tool Another aspect of the present invention is seen in a method for monitoring a processing tool The method includes processmg a plurality of articles in the processing tool, measurmg a characteristic of selected articles at a measurement frequency, and changing the measurement frequency based on a usage characteristic of the processing tool BRIEF DESCRIPTION OF THE DRAWINGS The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which Figure 1 is a simplified block diagram of a processmg line in accordance with the present invention, Figure 2 is a defect count curve for a deposition tool of Figure 1 following a cleaning or refurbishment, Figure 3 is a deposition rate curve for the deposition tool of Figure 1 following a cleaning or part replacement, and Figure 4 is a flow diagram of a method for monitoring a processing tool in accordance with the present mvention While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims MODE(S) FOR CARRYING OUT THE INVENTION Illustrative embodiments of the invention are described below In the interest of clarity, not all features of an actual implementation are described m this specification It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure Turning now to the figures, and, in particular, to Figure 1, a block diagram of a processmg line 10 in accordance with the present invention is provided The processing line 10 includes a processmg tool 20 for processing semiconductor wafers 30 and a measurement tool 40 for taking performance measurements on some of the wafers 30 processed by the processing tool 20 to measure the efficacy of the process implemented by the processing tool 20 An automatic process controller 50 interfaces with the measurement tool 40 and the processing tool 20, at least in part, to determine the measurement frequency used by the measurement tool 40 based on characteristics of the processing tool 20 The measurement tool 40 may be remote from the processing tool 20 as shown, or alternatively, the measurement tool 40 may be integrated with the processing tool 20 (/ e , in situ) The particular process performed by the processing tool 20 and the particular performance measurement taken by the measurement tool 40 may vary widely Various illustrative examples will be described m greater detail hereinafter, however, application of the present invention is not limited to the particulars described in such examples Rather, the instant invention is applicable to a wide variety of processmg tools 20 related or not to semiconductor processing, and the performance measurement may be selected from a wide range of performance measurements applicable to the particular product being processed or the particular process being performed The automatic process controller 50 adjusts the measurement frequency of the measurement tool 40 based on usage characteristics of the processing tool 20 Exemplary usage characteπstics include the time elapsed smce a preventative maintenance task has been performed (e g , cleanmg) and the time elapsed since a particular part in the processing tool 20 has been replaced (e g , target, shower head, in-line filter) The performance measurement taken by the measurement tool 40 to gauge the efficacy of the processing tool 20 may include parameters such as, but not limited to, process layer thickness, defect count, or resistivity In the illustrated embodiment, the automatic process controller 50 compπses a computer executing application software adapted to perform the functions described The automatic process controller 50 may be coupled to other computers (not shown) over a computer network (not shown) Mamtenance on the processing tool 20 may be tracked by a factory control system accessible to the automatic process controller 50 Alternatively, the automatic process controller 50 may receive usage characteristics via manual input from the operator of the processing tool 20 Based on the usage characteristics derived or received by the automatic process controller 50, the measurement frequency of the measurement tool 40 is mcreased or decreased, based, at least in part, on the expected stability of the processing tool 20 During times of expected instability, the automatic process controller 50 increases the measurement frequency of the measurement tool 40, and during times of expected greater stability, the measurement frequency is decreased It will be appreciated that mtermediate frequencies may be used dunng transitions from expected periods of instability to periods of greater stability Exemplary period of increased instability mclude immediately following a cleaning operation, immediately following a target, showerhead, or in-line filter replacement, near the expected end-of- fe of a target, showerhead, or filter, near the anticipated time that a cleaning should be performed, etc Periods of greater stability may be defined as those periods other than those described above as being unstable, otherwise referred to as normal or steady-state operating conditions Figure 2 illustrates a defect count curve for a deposition tool following a cleanmg or refurbishment In an initial period 100, the defect count may be high During the initial period 100, the measurement frequency of the measurement tool 40 is mcreased as compared to its default value A steady-state period 110 follows the initial period 100, and the measurement frequency of the measurement tool 40 is decreased to the default value Finally, as the age of the hardware increases, an end-of-life period 120 is entered where the defect count again may increase During the end-of-life period 120, the measurement frequency of the measurement tool 40 is again mcreased The transition times between the steady-state period 110 and the initial and end-of-life periods 100, 120 are not completely predictable The determination of the times to transition from one period 100, 1 10, 120 to another may be based on predetermined time frames or, alternatively based on the performance measurements themselves The particular frequencies for the initial period 100 and the end-of-life period 120 may not necessarily be the same For example, if during the initial period 100, where the measurement tool 40 is measuring at an mcreased frequency, and the automatic process controller 50 detects a sustained decrease in the defect count, the automatic process controller 50 directs the measurement tool 40 to transition to the default frequency Likewise, if the measurement tool 40 is measuring at the default frequency, and the automatic process controller 50 detects a susta ed increase in the defect count, the automatic process controller 50 directs the measurement tool 40 to transition to the increased frequency Figure 3 illustrates a deposition rate curve for a deposition tool following a cleanmg or showerhead replacement In an initial period 200, the deposition rate is generally stable Dur g the initial period 200, the measurement frequency of the measurement tool 40 is set by the automatic process controller 50 to the default frequency Over time, as material builds up on the processing tool 20, the target is depleted, or the in-line filter becomes obstructed, the deposition rate decreases The period marked by a marked decrease in deposition rate is the end-of-life period 210 Durmg the end-of-life period 120, the measurement frequency of the automatic process controller increases the measurement frequency of the measurement tool 40 to the mcreased value The transition to the increased frequency could be used to trigger an alert or message to an operator of the processing tool 20 to evaluate the conditions and possibly schedule a maintenance task Usmg such an approach, the maintenance interval could be effectively lengthened when the transition to the higher frequency occurs at a point in time later than the expected time for entering the end-of-life interval 120, 210 This approach identifies both early degraded conditions as well as conditions more favorable than predicted where maintenance mtervals can be extended The specific frequencies for the default frequency and the increased frequency are application dependent For example, the default frequency may be every N lots, every shift, every month, etc The increased frequency may be some multiple (e g , two or three times) the default frequency It is contemplated that the automatic process controller 50 may be configured to adaptively change the frequency and or transition times based on the actual history of the measurement tool 40 For example, the automatic process controller 50 may attempt maintain a constant ratio between the percent failed and the percent measured That is, during periods with a low number of failures the frequency may be adaptively decreased Likewise, during periods with higher rates, the frequency may be adaptively increased In such an embodiment, there may not be distinct intervals, but rather a continuum of adaptively changing measurement frequencies based on the current failure rate The automatic process controller 50 may be adapted to change the measurement frequency of the measurement tool 40 to identify a number of degraded conditions For example, the automatic process controller 50 may increase the measurement frequency around times of expected cleanings, target replacement, shower-head replacement, and in-line filter replacement These intervals may or may not overlap Turning now to Figure 4, a flow diagram of a method for monitoring a processing tool 20 is provided In block 300, a plurality of articles are processed in the processing tool 20 In block 310, a characteristic of selected articles is measured at a measurement frequency The measurement frequency is changed based on a usage characteristic of the processing tool 20, in block 320 The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled m the art having the benefit of the teachings herein Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accord gly, the protection sought herein is as set forth in the claims below

Claims: CLAIMS 1 A processmg line (10), compπsmg a processing tool (20) adapted to process articles (30), a measurement tool (40) adapted to measure a characteristic of selected articles (30) at a measurement frequency, and an automatic process controller (50) adapted to change the measurement frequency based on a usage characteristic of the processing tool (20) 2 The processmg line (10) of claim 1 , wherein the automatic process controller (50) is adapted to set the measurement frequency at a first frequency durmg a first time period and set the measurement frequency at a second frequency durmg a second time period 3 The processing line (10) of claim 2, wherein the automatic process controller (50) is adapted to transition from the first time period to the second time period based on a least one of a predetermined time and the characteristic measured by the measurmg tool (40) 4 The processmg lme (10) of claim 1, where the articles (30) comprise semiconductor wafers, the processmg tool (20) is adapted to form a layer of material on the wafers, and the characteristic measured by the measurement tool (40) comprises at least one of a thickness of the layer of material, a resistivity of the layer of material, and a defect count associated with the layer of material 5 The processing l e (10) of claim 1, wherein the usage characteristic comprises at least one of a period of time elapsed since a preventative maintenance task has been performed on the processing tool (20) and a period of time elapsed since a particular part in the processing tool (20) has been replaced 6 A method for monitoring a processing tool (20), comprising processing a plurality of articles (30) in the processing tool (20), measuring a characteristic of selected articles (30) at a measurement frequency, and changing the measurement frequency based on a usage characteristic of the processing tool (20) 7 The method of claim 6, wherein changing the measurement frequency includes setting the measurement frequency at a first frequency during a first time period, and setting the measurement frequency at a second frequency durmg a second time period 8 The method of claim 7, wherem setting the measurement frequency at a second frequency includes setting the measurement frequency at a second frequency based on at least one of a predetermined period of time and the characteristic measured 9 The method of claim 6, wherein processing the plurality of articles (30) comprises processing a plurality of semiconductor wafers, the processing tool (20) is adapted to form a layer of material on the wafers, and measuring the characteristic comprises measuring at least one of a thickness of the layer of material, a resistivity of the layer of material, and a defect count associated with the layer of material 10 The method of claim 6, wherein changing the measurement frequency based on the usage characteristic of the processing tool (20) comprises changmg the measurement frequency based on at least one of a period of time elapsed since a preventative maintenance task has been performed on the processing tool (20) and a period of time elapsed since a particular part in the processing tool (20) has been replaced

Inventors: CHRISTIAN CRAIG W, DAVIS BRADLEY M, EVANS ALLEN L, CHRISTIAN, CRAIG, W., DAVIS, BRADLEY, M., EVANS, ALLEN, L.
Applicants: ADVANCED MICRO DEVICES INC, ADVANCED MICRO DEVICES, INC.
Application year: 2000
Main classification: H01L21
IPC codes: H01L21