semi合集-English.pdf - 第1415页

SEMI E30-1103 © SEMI 1992, 2003 89 A.7 Examples of Limits Monitoring A7.1 Introduction A7.1.1 Four lim its moni toring examples are included below to help clarify th e use of limits and to illustrate typical applicati on…

SEMI E30-1103 © SEMI 1992, 2003

Figure A.6.1 shows the effective control model

based

on the following host assumptions:

— The fundamental requirements are met, but the

additional host-intiated control capability is not

implemented.

— The configuration for the default entry to

CONTROL is set to an OFF-LINE substate (either

ATTEMPT ON-LINE or EQUIPMENT OFF-

LINE).

— The destination state for transition 4 (failure of

S1,F1 transaction) is configured to EQUIPMENT

OFF-LINE.

Figure A.6.1

Example of the Simplified “Effective” Control

Model

This view of the model has two further settings that the

host recognizes

as changeable at the equipment. The

first is the configuration of which substate of OFF-

24 See Section 3.3 for details of the control model.

LINE to be activated upon system initialization. The

second is the front panel switch that determines

whether the active system substate is LOCAL or

REMOTE when ON-LINE.

This application has the following implications:

— This application requires that the equipment begin

with the OFF-LINE state active. Thus, an

equipment initiated S1,F1/F2 transaction must be

completed before the equipment will begin sending

all messages to the host.

— If a failed attempt to go ON-LINE is made by the

equipment, it will not allow the host to complete

the transition at a later time. An operator will be

required to re-initiate the transition to ON-LINE

when the host becomes ready.

— Once ON-LINE, the equipment will remain ON-

LINE until an operator sets the equipment OFF-

LINE at the equipment front panel.

— Since all transitions into the HOST OFF-LINE

state are eliminated, this state is effectively

eliminated from the host view of the control model.

This application retains the following features:

— The ON-LINE state is achieved only after the host

acknowledges the equipment by replying to the

S1,F1 with and S1,F2. This confirms to the

operator attempting to put the equipment ON-LINE

that the host application is ready for work to begin.

— It provides the operator the means to set the

equipment OFF-LINE for non-host-related

activities

(e.g., maintenance, test lots).

— The operator has the ability to operate the

equipment with either the REMOTE or LOCAL

state active. As the equipment transitions to ON-

LINE, the preferred substate is automatically

chosen (based on a front panel switch).

— The user may configure which substate of OFF-

LINE the equipment will initially activate at

system initialization. If ATTEMPT ON-LINE is

chosen, the equipment will automatically attempt

the transition to the ON-LINE state as system

initialization.

25 Which activities are “non-host-related” varies from factory to

factory. In general, fewer activities are “non-host-related” as a

factory’s automation level increases.

SEMI E30-1103 © SEMI 1992, 2003

A.7 Examples of Limits Monitoring

A7.1 Introduction

A7.1.1 Four limits monitoring examples are included

below to help clarify the use of limits and to illustrate

typical applications. The first example shows how to

apply limits to boolean values. The second illustrates

application of several limits to a floating point variable

in a classical control zone style. The third example

shows an integer counter variable used to prompt for

equipment maintenance.

A7.2 Examples

A7.2.1 Example 1 –– Valve Monitoring

A7.2.1.1 The ACME Shine-Um-Rite Model 13

includes a sump which contains the chemical agent

used to clean bare wafers. A chemical feeder system

serves to refill the sump when the level drops below a

certain level. The fill is accomplished via an on-off

value driven by sensors in the sump. Facilities must be

informed of the proportion of the time the valve is open

(approximates usage) and any time the value remains

open for more than 5 minutes (valve likely broken).

A7.2.1.2 To implement this requirement, a limit was

defined for the Boolean status variable which contains

the current state of the valve (i.e., 0 = Closed, 1 =

Open). See Figure A7.1 for illustration. LIMITID1 was

defined with UPPERDB = LIMITMAX = 1 (Open) and

LOWERDB = LIMITMIN = 0 (Closed). As a result,

any time the valve opens, a collection event is

generated with TransitionType = 0 and when the valve

closes, a collection event is generated with

TransitionType = 1. An event report containing the

DVVAL LimitVariable was attached to each collection

event and reporting for the event was enabled.

NOTE: Boolean values are defined as 0 =

False/Closed/Off and any value > 0 = True/Open/On ––

never depend on a value of 1.

Figure A7.1

Valve Monitoring Example

A7.2.2 Example 2 –– Environment Monitoring

A7.2.2.1 ACME also makes a Model 2 Stepper. The

environmental control system of this equipment is

designed to hold the internal temperature relatively

constant, but is sensitive to large changes in the

external environment, opening of access doors, etc. To

ensure that processing conditions are appropriate, the

internal stepper temperature is monitored to ensure it

remains in a safe operating zone (within “Shutdown”

limits). In addition, a second set of limits are used

within the Shutdown limits to bound the “Normal”

operating range. Frequent excursions from the normal

range into the “warning” range will prompt service on

the environmental control system. The target

temperature range is specified as 98–100° , the

shutdown limits as 95–103° .

A7.2.2.2 Event reports are desired when the internal

temperature moves outside of the normal operating

zone into a warning zone (above or below), when the

temperature moves back into the normal operating zone

from the warning zones, and when the temperature

moves out of the warning zones into the shutdown

zones. Furthermore, temperature fluctuations of 0.5°

should not trigger multiple event reports.

A7.2.2.3 Probably the most intuitive use of the limits

monitoring capability is in establishing normal,

warning, and shutdown zones for a particular

equipment variable. Limits may be combined to provide

such a scenario. The method is described below and

illustrated in Figure A7.2. Please note that in the figure,

limits are denoted as solid lines for simplicity, with

deadbands indicated using the ± notation.

Figure A7.2

Environment Monitoring Example

A7.2.3 Example 3 –– Calibration Counter

A7.2.3.1 Another ACME equipment is the multi-

chamber Duz-It-All Model 7. This machine includes

redundant chambers to increase throughput. One

particular chamber on this equipment requires periodic

SEMI E30-1103 © SEMI 1992, 2003

calibration. The need for calibration is a non-linear

function of the number of wafers processed in that

chamber. A status variable exists which contains the

number of wafers processed since the last calibration

was performed. Maintenance is definitely required after

every 8 cycles, but the machine must be checked after 5

and 7 cycles to determine whether early calibration is

necessary. This checking may be done by examining

certain other equipment status variables.

A7.2.3.2 To meet this need, three limits are defined for

the counter variable. Three limits were set, at 5, 7, and

8. Deadbands are set to zero, since chattering is not a

problem. All the pertinent information is placed in an

event report which is attached to the CEID for the

limits of the counter to negate the need for further

message exchange. Event reports are generated as each

limit is reached (one zone transition each), and when

the counter is reset following calibration (one, two, or

three zone transitions referenced in one report). Figure

A7.3 illustrates this example. Note that disabling the

report upon counter reset (downward transitions) is not

possible.

Figure A7.3

Calibration Counter Example

A7.2.4 Example 4 –– Derived Variables

A7.2.4.1 The flagship of the ACME line is the new

HotDog Furnace. This is a vertical furnace which

exposes wafers to a variety of temperatures during

processing. The temperature profile during the run is

critical to the process and is typically contains a number

of plateau’s at different levels during the run. The

owner wishes to monitor the temperature and be alerted

whenever the actual temperature profile differs from the

ideal by > 0.5° . The derived variable was created to

provide a steady target range during the run, no matter

what the desired temperature range happened to be.

Deviation from “ideal temperature profile” was chosen

as the new variable to be monitored. The equipment

already had access to the profile for the run, which

described the desired temperature at a given time into

the process. The manufacturer added a calculation each

time the actual temperature was sampled, subtracting

the ideal temperature from the actual. They provided as

status variables the actual temperature, the ideal

temperature, and the new “deviation from profile”

variable. One limit was activated and set to 0.5 degrees

and a second set to –0.5 degrees (each with a deadband

width of 0.05). Thus, when the temperature deviation

from setpoint exceeds ± 0.5, an event is generated

containing the current desired temperature and the

actual temperature. For good measure, additional data

was added, providing time since start of run to

document the precise point in the process that the

problem occurred.

A7.2.4.2 In order to achieve the desired behavior, the

host defines four monitoring limits. Two of the limits

establish the target zone. These are responsible for

reporting transitions from normal to warning zones in

either direction. The other two limits establish the

transitions between the warning zones and the error

zones. The difference between UPPERDB and

LOWERDB for each limit is 0.5. This may also be

expressed as limit ± 0.25. Combining limits does not

change the way the equipment treats limits monitoring,

but rather builds a method of interpreting limits from

the host’s point of view.

A.8 Process Parameter Modification for

Process and Equipment Control

A8.1 Introduction

A8.1.1 In many equipment control applications there is

a need for a GEM host to modify one or a small set of

process parameters associated with a recipe. The

number of parameters modified, frequency of

modification (e.g., wafer-to-wafer, batch-to-batch, etc.),

range of modification, etc., is largely a function of the

equipment control application. Utilizing GEM, at least

two methods are envisioned for modifying process

parameters on a tool. With the first method,

“Equipment Constants” can be used to relate process

parameters of the updated recipe. Equipment Constants

can also be used in a mode where they relate suggested

modifications to process parameters from the stored

recipe, i.e., the constants contain only the + /-

differential from a nominal value. The former mode is

preferred because it better ensures data integrity

between the controller and tool. With the second

method the entire recipe could be downloaded, but this

results in an enormous amount of communication

overhead. Note that, in all cases, the Equipment

Constants do not replace the process parameters inside

a recipe, but are associated with (e.g., linked to) these

parameters to relate modifications. The remainder of

this application note provides a description of how

process parameter modification can be implemented

using existing GEM capabilities. The method may be

used in a GEM compliant system provided that the

specific GEM capabilities described are supported.