Patent Application
20130025786
1. Field
This disclosure relates generally to mole or gas delivery devices, and more particularly to a method of and system for pulse gas delivery (PGD). As used herein the term “gas(es)” includes the term “vapor(s)” should the two terms be considered different.
2. Overview
The manufacture or fabrication of semiconductor devices often requires the careful synchronization and precisely measured delivery of as many as a dozen gases to a process tool such as a vacuum process chamber. For purposes herein, the term “process tool” may or may not include a process chamber. Various recipes are used in the manufacturing process, involving many discrete process steps, where a semiconductor device is typically cleaned, polished, oxidized, masked, etched, doped, metalized, etc. The steps used, their particular sequence, and the materials involved all contribute to the making of particular devices.
As more device sizes have shrunk below 90 nm, one technique known as atomic layer deposition, or ALD, continues to be required for a variety of applications, such as the deposition of barriers for copper interconnects, the creation of tungsten nucleation layers, and the production of highly conducting dielectrics. In the ALD process, two or more precursor gases are delivered in pulses and flow over a wafer surface in a process tool maintained under vacuum. The two or more precursor gases flow in an alternating or sequential manner so that the gases can react with the sites or functional groups on the wafer surface. When all of the available sites are saturated from one of the precursor gases (e.g., gas A), the reaction stops and a purge gas is used to purge the excess precursor molecules from the process tool. The process is repeated, as the next precursor gas (e.g., gas B) flows over the wafer surface. For a process involving two precursor gases, a cycle can be defined as one pulse of precursor A, purge, one pulse of precursor B, and purge. A cycle can include the pulses of additional precursor gases, as well as repeats of a precursor gas, with the use of a purge gas between successive pulses of two precursor gases. This sequence is repeated until the final geometrical characteristic is reached. These sequential, self-limiting surface reactions result in one monolayer of deposited film per cycle.
The delivery of pulses of precursor gases introduced into the process tool can be controlled using on/off-type valves which are simply opened for a predetermined period of time to deliver a desired amount (mass) of precursor gas with each pulse into the process chamber of the process tool. Alternatively, a mass flow controller, which is a self-contained device comprising a transducer, control valve, and control and signal-processing electronics, is used to deliver an amount of gas (mass) at predetermined and repeatable flow rates, in short time intervals. In both cases, the amount of material (mass) flowing into the process tool is not actually measured, but inferred from measuring parameters of the ideal gas law.
Systems known as pulse gas delivery (PGD) devices have been developed that can deliver measured pulsed mass flow of precursor gases into semiconductor process tools. Such devices are designed to provide repeatable and precise quantities (mass) of gases for use in semiconductor manufacturing processes, such as atomic layer deposition (ALD) processes.
Single channel PGD devices each include a delivery reservoir or chamber containing the gas to be delivered during the ALD process upstream to the process tool. Gas is introduced into the delivery chamber through an inlet valve during a charging phase (when the corresponding inlet and outlet valves are respectively opened and closed), while gas is delivered from the delivery chamber through an outlet valve during a delivery phase. A pressure sensor and a temperature sensor are used to measure the pressure and temperature of the gas in the delivery chamber, and a dedicated controller is used to sense the pressure and temperature information and control the opening and closing of the inlet and output valves. Since the volume of the delivery is fixed and known, the amount of gas, measured moles, delivered with each pulse is a function of the gas type, the temperature of the gas in the chamber, and the pressure drop of the gas during the duration of the pulse.
Multiple channel PGD devices include multiple delivery chambers, each containing a precursor or purge gas used in a gas delivery process. Each precursor and purge gas used in a process can then be introduced through a different channel. This allows the device to operate in the charging phase for one gas provided in one channel, while delivering pulses of a gas provided in another channel. The flow of the pulse of gas from each delivery chamber is controlled with a corresponding on/off-type outlet valve between the delivery chamber of the PGD and the process tool receiving the gas. The amount of time the valve is required to be open to deliver a pulse of gas of a given mass is a further function of the starting pressures of the gas in the corresponding delivery chamber and the downstream pressure of the process tool. For example, for a given amount of gas that needs to be delivered, the starting pressure in the delivery chamber at a higher starting pressure requires a shorter time for the valve to be open than at a lower starting pressure since the mass flow occurs more quickly at the higher starting pressure. The charge period and the delivery period of PGDs are tightly controlled for fast pulse gas delivery applications in order to insure accurate delivery of prescribed amounts of gas(es). As a result, the upstream pressure of the PGDs as well as the charged pressure in the PGDs are tightly controlled in order to meet the repeatability and the accuracy requirement of the ALD process. By using multiple channels, and staggering the charging and delivery phases of the channels, the sequential delivery of pulses of different gases can be faster than achieved by a single channel device since it is possible to charge a delivery chamber of one channel, while delivering a predetermined amount of gas from the delivery chamber of another channel.
Current multichannel PGD devices include a separate dedicated channel controller for operating each channel. Each channel controller receives all of its commands from the tool/host controller used to control the process in the process tool. In this way each channel is controlled by the tool/host controller so that the entire process can be coordinated and controlled by that central controller. Thus, during a process run, the tool/host controller continually sends instruction commands to each channel controller to insure the timely and coordinated delivery of the individual pulses of gas from the multiple channels.
More recently, certain processes have been developed that require high speed pulsed or time-multiplexed processing, such processes being referred to generally as “deep reactive-ion etching”, or “DRIE” processes. For example, the semiconductor industry is developing advanced, 3-D integrated circuits thru-silicon vias (TSVs) to provide interconnect capability for die-to-die and wafer-to-wafer stacking Manufacturers are currently considering a wide variety of 3-D integration schemes that present an equally broad range of TSV etch requirements. Plasma etch technology such as the Bosch process, which has been used extensively for deep silicon etching in memory devices and MEMS production, is well suited for TSV creation. The Bosch process, also known as a high speed pulsed or time-multiplexed etching, alternates repeatedly between two modes to achieve nearly vertical structures using SF6 and the deposition of a chemically inert passivation layer using C4F8. Targets for TSV required for commercial success are: adequate functionality, low cost and proven reliability.
The high speed processes require fast response times between successive pulses in order to better control the processes. While multichannel PGD devices have made the processes possible, in general the faster the device can transition between the alternating etch and passivation steps, the better the control of the process. Timing is very important for controlling the etching and passivation steps, particularly the time it takes to introduce the passivation gas following an etching step so that the etching step is stopped at a precise time. The faster the steps can be performed the better.
Accordingly, it is desirable to design a multichannel PGD device that can carry out high speed processes faster, without sacrificing the advantages of a multichannel PGD device.
Current multichannel PGD devices include a separate dedicated channel controller for operating each channel. Each channel controller receives all of its commands from the tool/host controller used to control the process in the tool. In this way each channel is controlled by the tool/host controller so that the entire process can be coordinated and controlled by that central controller. Thus, during a process run, the tool/host controller continually sends instruction commands to each channel controller to insure the timely and coordinated delivery of the individual pulses of gas from the multiple channels.
One improvement is described in the copending '534 application, wherein a multi-channel PGD system is described as comprising a dedicated multichannel controller configured so as to receive all of the instructions from the host controller or a user interface prior to running all of the process steps to be carried out by the PGD system. The multichannel controller is thus configured to control all of the individual channels through the steps of an etch-passivation process where a gas is introduced into a process tool to perform an etching process followed by the introduction of a second passivation gas to stop the etching process. The dedicated multichannel controller thus can be easily programmed to provide control signals for the multiple channels for the entire process, reducing the computing overhead of the host controller so that it is free to carry out other functions relating to the process tool. In one embodiment, the host computer or user interface provides a start command to the dedicated multichannel controller, and the controller singularly runs the process by providing all of the commands to the individual components of all of the channels while receiving the signals from the pressure and temperature sensors of the channels. While this system allows for an improved system architecture for controlling the flow of pulses into the chamber, the system does nothing to control the pressure within and the flow of fluid from the processing tool.
Examples of pulse mass flow delivery systems can be found in U.S. Pat. Nos. 7,615,120; 7,615,120; 7,628,860; 7,628,861, 7,662,233; 7735452 and 7794544; U.S. Patent Publication Nos. 2006/0060139; and 2006/0130755, and pending U.S. application Ser. Nos. 12/689,961, entitled CONTROL FOR AND METHOD OF PULSED GAS DELIVERY, filed Jan. 19, 2010 in the name of Paul Meneghini and assigned the present assignee (Attorney's Docket No. 56231-751 (MKS-194)); and U.S. patent application Ser. No. 12/893,554, entitled SYSTEM FOR AND METHOD OF FAST PULSE GAS DELIVERY, filed Sep. 29, 2010 in the name of Junhua Ding, and assigned to the present assignee (Attorney's Docket No. 86400-015 (MKS-218)); and U.S. patent application Ser. No. 13/035,534, entitled METHOD AND APPARATUS FOR MULTIPLE-CHANNEL PULSE GAS DELIVERY SYSTEM, filed Feb. 25, 2011 in the name of Junhua Ding and assigned to the present assignee (Attorney's Docket No. 86400-0027 (MKS-219)).
In accordance with one aspect of the improved gas delivery system for delivering a sequence of pulses of prescribed amounts of at least two gases to a process tool in accordance with a predetermined recipe of steps of a gas delivery process, comprising:
In accordance with another aspect of the invention, the combination of a process tool system including a process chamber, and a pulse gas delivery system for delivering a sequence of pulses of prescribed amounts of gases to a process tool is provided, wherein the pulse gas delivery system comprises:
A method of delivering a sequence of pulses of prescribed amounts of gases in accordance with the steps of a recipe to a process chamber of a process tool using a pulse gas delivery system comprising a plurality of channels, each channel including a control valve connected so as to control the duration of each pulse of gas flowing through the corresponding channel into the process chamber of the process tool; and an exhaust valve for controlling the pressure within the process chamber, the exhaust valve including a valve controller for controlling the operation of the control valves and the exhaust valve in accordance with the predetermined recipe of steps; the method comprising:
In accordance with another aspect of the invention, the exhaust valve controller is configured to operate in a hybrid feedback mode including both open feedback loop control wherein the exhaust valve is set at a preselected position based on a past learned position for each step of the gas delivery process, and closed feedback loop control of the system for each step of the gas delivery process as a function of the pressure within the process tool following the open loop control.
These, as well as other components, steps, features, objects, benefits, and advantages, will now become clear from a review of the following detailed description of illustrative embodiments, the accompanying drawings, and the claims.
The drawings disclose illustrative embodiments. They do not set forth all embodiments. Other embodiments may be used in addition or instead. Details which may be apparent or unnecessary may be omitted to save space or for more effective illustration. Conversely, some embodiments may be practiced without all of the details which are disclosed. When the same numeral appears in different drawings, it refers to the same or like components or steps.
In the drawings:
Referring to
Thus, each channel includes a pulse control valve 18 for controlling the duration of each pulse of gas delivered through that channel 12 to the process chamber 20. Each channel may also include a mass flow controller 16 configured to control the amount of gas of each pulse delivered through the corresponding pulse control valve 18, although the mass flow controllers are not essential to accomplish the advantages described herein. In the illustrated embodiment, the pulse control valves 18 can be shut-off valves having relatively fast shut off responses, i.e., transition between a fully open state and a fully shut off state quickly. For example, the shut off valves can transition between the two states on the order of between one and five milliseconds, although this can clearly vary based upon a number of factors, such as the valves used, the process controlled by the system 10, etc. A pressure sensor 22 is provided for the process chamber so that the pressure within the chamber 20 can be monitored as a part of the control of the pulse gas delivery process described herein, since the required time duration of each pulse is at least a partial function of the pressure within the process chamber 20. As will be more apparent hereinafter, the pressure within the process chamber is controlled by using a vacuum pump 26 to pump gas from the process chamber 20, and controlling the rate at which the gas is pumped from the chamber by controlling the position of the valve body of exhaust valve 24. Exhaust valve is in the form of a throttle valve, and in one embodiment is in the form of a pendulum valve. The throttle valve 24 should have a very fast response time, e.g. the transition time between a fully closed position and a fully opened position is in the order of 600 millisec. The throttle valve 24 includes an exhaust valve controller 28, provided to control the operation of the throttle valve, but is modified to control the opening and closing of the pulse control valves 18 and the throttle valve 24 so as to control all of the steps of the pulse delivery process. The exhaust valve controller 28 can receive from the host computer 30, or some other device through a user interface 32, the specific recipe instructions for processing the recipe of steps of the gas delivery process carried out in the chamber 20. Similarly, the process can be initiated with a command through user interface 32 from host computer 30 or other device. Storage memory 34 is provided for storing instructions and data relating to the detailed steps of the recipe, as well as learned data relating to the approximate position of the valve body of the throttle valve for each step, the need for which will become more evident hereinafter. Memory 34 can be internal or external of the valve controller 28, but should be dedicated for use in operating valve 24 to control the pressure within the process chamber 20 with each step of the stored recipe of steps. Using the memory 34 to store the sequence of each recipe allows for valve controller 28 to control the pressure within and flow from the process chamber 20 separate from the host computer 30 in accordance with the each step of each stored recipe.
The exhaust valve controller 28 is connected to receive pressure signals from the pressure sensor 22, as well as control the valves 18 and 24 all in accordance with the instruction steps provided in memory 34 so as to carry out the stored recipe. The exhaust valve controller 28 thus controls (a) the duration of each gas pulse by the opening and closing of the appropriate valves 18 in the proper sequence determined by the recipe as a function of the pressure readings provided from sensor 22, and (b) the pressure of the gas in the chamber by controlling the position of the valve body of the throttle valve. With the recipe steps stored in memory 34, the exhaust valve controller can run an entire process with a single start command from the host computer 30, or other device, provided through user interface 32, without further need for the user or the host computer to interact with the system, unless it is desired to prematurely end the process. In the later case a single stop command can be initiated and provided to the exhaust valve controller. This approach provides better feedback, and also reduces the amount of computer overhead for the host computer, and less interaction by the user through the user interface.
Many recipes can require the system to continuously run for a relatively long time, e.g., 60 minutes, and execute a large number of commands, e.g., 1000 steps, within that time frame. Because of the long run time, and the various electro-mechanical operations of the system during the run time, variations in system performance can occur as a process proceeds through all of the steps of a recipe. Such variations can occur due to various factors, including variations in the response time of the pulse control valves, variations in pressure control within the process chamber due to heat build up in the various moving parts as the process proceeds, etc. As a consequence, it has been found that providing only closed loop system control can impose limits on how fast each step of the recipe can be performed since a typical recipe requires the system to be reconfigured at the beginning of each step, requiring a certain amount of settling time.
Accordingly, another aspect of the invention is to control the gas delivery process using a hybrid open and closed loop control approach, including partially open loop control and partially closed loop control. Open loop control uses data that is previously generated by running the steps in the prescribed sequence of each recipe in its entirety as closed loop controlled system during a “training run”, and generating data representing the valve body position for each step. This data can be stored in memory 34. The hybrid open and closed loop approach to controlling the valve position of valve 24 during a recipe process is illustrated in
As shown in more detail in
The closed loop control phase of each process step shown in
As mentioned, for each recipe the system requires data to be stored in the storage memory preferably in the form of a table for the open loop control. The data can be generated by running the system with closed loop control during a training run of the recipe. Once the data is acquired, the system can operate with hybrid control.
In operation, the process steps for the multichannel PGD device 10 are provided to the exhaust valve controller 28 by uploading a program to the controller 28 through the user interface 32 from host controller 30 or other device. The system is operating in a training run so that data can be stored in memory. Once the controller is properly programmed, the system is now ready to operate under hybrid control.
The exhaust valve controller 28 is configured to provide data and instructions to and from the components making up each of the channels, as well as any additional data and instructions to and from a user interface/host computer 28. The user interface/host computer 30 can be any suitable device such as a computer including a keyboard and monitor configured so that an operator can operate the PGD system 10. It should be apparent, that wherein the host computer is the computer used to operate the tool, the use of the dedicated controller to run the sequence of steps frees up operating overhead of the host computer, allowing it to operate more efficiently.
It should be evident that various changes can be made to the embodiments described without departing from the scope of the claims. For example, while the embodiment described utilizes the valve controller to control the pressure within the chamber of the tool, and the position of the throttle valve, the valve controller can also be used to control the mass flow controllers 16A-16N, and control valves 18A-18N. With such an arrangement the valve controller need only issue a start and stop commands for the entire recipe run, which is controlled by the valve controller.
The components, steps, features, objects, benefits and advantages which have been discussed are merely illustrative. None of them, nor the discussions relating to them, are intended to limit the scope of protection in any way. Numerous other embodiments are also contemplated. These include embodiments which have fewer, additional, and/or different components, steps, features, objects, benefits and advantages. These also include embodiments in which the components and/or steps are arranged and/or ordered differently.
Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications which are set forth in this specification, including in the claims which follow, are approximate, not exact. They are intended to have a reasonable range which is consistent with the functions to which they relate and with what is customary in the art to which they pertain.
All articles, patents, patent applications, and other publications which have been cited in this disclosure are hereby incorporated herein by reference.
The phrase “means for” when used in a claim is intended to and should be interpreted to embrace the corresponding structures and materials which have been described and their equivalents. Similarly, the phrase “step for” when used in a claim is intended to and should be interpreted to embrace the corresponding acts which have been described and their equivalents. The absence of these phrases in a claim means that the claim is not intended to and should not be interpreted to be limited to any of the corresponding structures, materials, or acts or to their equivalents.
Nothing which has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is recited in the claims.
The scope of protection is limited solely by the claims which now follow. That scope is intended and should be interpreted to be as broad as is consistent with the ordinary meaning of the language which is used in the claims when interpreted in light of this specification and the prosecution history which follows and to encompass all structural and functional equivalents.
Reference is made to U.S. patent application Ser. No. 12/893,554, entitled SYSTEM FOR AND METHOD OF FAST PULSE GAS DELIVERY, filed Sep. 29, 2010 in the name of Junhua Ding, and assigned to the present assignee (Attorney's Docket No. 86400-015 (MKS-218)); and U.S. patent application Ser. No. 13/035,534, entitled METHOD AND APPARATUS FOR MULTIPLE-CHANNEL PULSE GAS DELIVERY SYSTEM, filed Feb. 25, 2011 in the name of Junhua Ding and assigned to the present assignee (Attorney's Docket No. 86400-0027 (MKS-219)), both applications being incorporated herein in their entirety. The latter application is hereafter referred to as the '534 application”.
