Adaptive baking system and method of using the same

An adaptive baking system includes a baking chamber configured to receive a wafer, and a heating element configured to support the wafer. The adaptive baking system further includes a controller configured to receive temperature information related to the heating element and the wafer, wherein the controller is further configured to adjust an amount of heat provided by the heating element during a baking process in response to the temperature information.

BACKGROUND

Wafer baking is used to help cure a photoresist material on a wafer prior to patterning the photoresist material. The wafer is placed in a baking chamber and heated using a heating element. A duration and temperature of the baking process are predetermined based on a material of the photoresist material and characteristics of the wafer. The temperature in the baking chamber is kept at a constant temperature during the baking process. Following the baking process, the photoresist is patterned.

DETAILED DESCRIPTION

FIG. 1is a schematic diagram of an adaptive baking system100in accordance with some embodiments. Adaptive baking system100includes a chamber110. A heating element112is positioned within chamber110and configured to support a wafer114. Wafer114has a curvature which results from warpage induced by prior processing steps performed on the wafer. A gap116exists between wafer114and heating element112due to the warpage. During operation, heating element112is configured to generate heat in order to bake wafer114. A controller120is configured to provide signals to heating element112to control an amount of heat provided to wafer114. Adaptive baking system100further includes sensors118embedded in a surface of heating element112.

Chamber110is configured to house wafer114on heating element112. Chamber110includes a port for inserting and removing wafer114from an interior of the chamber. In some embodiments, chamber110includes an insulating covering configured to reduce heat loss from walls of the chamber to a surrounding environment. In some embodiments, walls of chamber110include steel, aluminum, ceramic or other suitable material. In some embodiments, chamber110is sufficiently large to house multiple heating elements112.

Heating element112is configured to support wafer114and supply heat to the wafer during the baking process. Heating element112is configured to receive signals from controller120and change an amount or a location of heat provided to wafer114during the baking process. In some embodiments, heating element112includes sensors configured to measure a temperature at a surface of the heating element closest to wafer114. In some embodiments, the sensors include thermometers, thermocouples, or other suitable temperature measuring elements. In some embodiments, heating element112includes a resistive heater. In some embodiments, heating element112includes at least one channel for transporting a heating fluid through the heating element. In some embodiments, heating element112includes an infrared light source configured to emit infrared radiation to contact wafer114.

FIG. 2is a top view of a heating element200in accordance with some embodiments. Heating element200includes thirteen heating zones1-13. In some embodiments, the heating element includes from2to100zones or from5to30zones. In some embodiments, the heating element as from1to5heating zones per 50-80 cm2of the heating element surface. In some embodiments, heating element200includes more or less than thirteen heating zones. In some embodiments, the heating zones are arranged in a concentric pattern. In some embodiments, the heating zones are arranged in a radial pattern. In some embodiments, the heating zones are arranged in a linear pattern or any other suitable arrangement. In some embodiments, the heating zones are individually controllable to adjust an amount and a duration of heating provided to a wafer, e.g., wafer114(FIG. 1).

In some embodiments where heating element200includes resistive heating elements, at least one separate heating element is included in each heating zone. In some embodiments where heating element200includes a channel for transporting a heating fluid, each heating zone includes a flow controlling element configure to enable increased or decreased flow of the heating fluid through the channel in the respective heating zone. In some embodiments, the flow controlling element includes a diverter, a valve, or another suitable flow controlling element. In some embodiments where heating element200includes an infrared light source, each heating zone includes radiation blocking element configured to selectively enable propagation of the infrared radiation through the heating element. In some embodiments, the radiation blocking element includes a shutter, a liquid crystal element, an electro-chromic element or another suitable radiation blocking element.

Returning toFIG. 1, during operation wafer114is housed in chamber110and supported on heating element112. In some embodiments, wafer114includes active elements. In some embodiments, wafer114includes a photoresist layer over a surface thereof. In some embodiments, the baking process is used to cure the photoresist layer over wafer114.

In some embodiments, chamber110includes sensors configured to measure a temperature of at least one surface of the wafer114. In some embodiments, the sensors are configured to connect to wafer114prior to insertion into chamber110. In some embodiments, the sensors are configured to connect to wafer114following insertion into chamber110. In some embodiments, the sensors, e.g., sensors118, are embedded in a surface of heating element112. In some embodiments, the sensors are remote sensors configured to measure a temperature of wafer114without contacting the wafer. In some embodiments, the sensors include thermometers, thermocouples, or other suitable temperature measuring elements.

Gap116is between wafer114and heating element112. In some embodiments, where wafer114experiences little or no warpage during prior processing gap116is reduced or omitted. Gap116changes an ability of heating element112to transfer heat to wafer114by changing a medium through which the heat energy is transferred. Edges of wafer114are in direct contact with heating element112while gap116has a greatest thickness near a center portion of the wafer. Based on this arrangement, the edges of wafer114will receive a higher amount of heat energy in comparison with the center portion of the wafer if heating element112is configured to provide uniform heating across an entire surface of the heating element.

Controller120is configured to control an amount of heat energy provided by heating element112. In some embodiments, controller120is configured to receive temperature information from wafer temperature sensors. In some embodiments, controller120is configured to receive temperature information from heating element temperature sensors. In some embodiments, controller120is configured to individually control heating zones of heating element112.

In some embodiments where controller120is configured to individually control heating zones, the controller is configured to send a single heating signal to heating element112. Heating element112then addresses the signal to the heating zones based on address information in the signal. In some embodiments where controller120is configured to individually control heating zones, the controller is configured to send a separate signal to each heating zone of heating element112. In some embodiments, controller120is configured to control individual heating zones in based on an amount of heat provided in adjacent heating zones. For example, control for heating zone3of heating element200(FIG. 2) is controlled based on an amount of heat provided in adjacent heating zones1,2,4,7and8.

In some embodiments, controller120is configured to control heating element112based on a graph of a temperature of heating element112and of a temperature of wafer114.FIG. 3is a graph300of a temperature of a wafer and a heating element during a baking process in accordance with some embodiments. Graph300includes a plot310of a target heating element temperature and a plot320of a measured heating element temperature. Graph300further includes a plot330of a target wafer temperature and a plot340of a measured wafer temperature. A largest heating element temperature variation350exists between plot310and plot320. A largest wafer temperature variation360exists between plot330and plot340. A compensation heating duration370is used to modify a baking process to obtain satisfactory results for a wafer, e.g., wafer114(FIG. 1).

In some embodiments, a controller, e.g., controller120(FIG. 1) is configured to control compensation heating duration370. In some embodiments, as an area between plot310and plot320or an area between plot330and plot340increases, the controller is configured to increase compensation heating duration370. In some embodiments, as largest heating element temperature variation350or largest wafer temperature variation360increases, the controller is configured to increase compensation heating duration370. In some embodiments, as a magnitude of a slope of plot310increases, the controller is configured to decrease compensation heating duration370. The controller is configured to adjust a size of compensation heating duration370by sending signals to a heating element, e.g., heating element112. In some embodiments, the controller is configured to adjust an amount of heat provided by the heating element uniformly across the heating element. In some embodiments, the controller is configured to adjust an amount of heat provided by the heating element based on individual heating zones on the heating element.

FIG. 4is a flow chart of a method400of using an adaptive baking system in accordance with some embodiments. Method400begins with operation402in which a wafer is inserted into a baking chamber. The wafer is positioned on a heating element, e.g., heating element112(FIG. 1), in the baking chamber. In some embodiments, the wafer, e.g., wafer114, is inserted through a port in an outer wall of the baking chamber, e.g., chamber110. In some embodiments, the wafer is inserted using a robotic arm. In some embodiments, the wafer is stored in a front opening universal pod (FOUP) prior to insertion in to the baking chamber. In some embodiments, the port is configured to close following insertion of the wafer. In some embodiments, multiple wafers are positioned on a single heating element. In some embodiments, the baking chamber includes multiple heating elements and a single wafer is placed on each heating element.

Method400continues with operation404in which a baking process begins. In some embodiments, the baking process is used to cure a photoresist layer on the wafer. In some embodiments, the baking process begins by using a controller, e.g., controller120(FIG. 1), to provide a signal to the heating element. Heating element begins providing heat to the wafer in response to the signal from the controller. In some embodiments, an additional heating element is used to provide a portion of the heat provided to the wafer. In some embodiments, the additional heating element comprises a radiative heating element, a heating gas inserted into the baking chamber, a heating lamp or another suitable heating element. In some embodiments, a temperature of the baking process is determined based on a curing temperature of a layer on the wafer. In some embodiments, the temperature of the baking process is based on empirical data collected from previous baking processes.

In operation406, a temperature of the wafer and a temperature of the heating element are monitored. In some embodiments, the temperature of the wafer is monitored using a plurality of sensors positioned across a surface of the wafer. In some embodiments, the temperature of the wafer is monitored using a remote temperature sensing element. In some embodiments, the sensors are connected to the wafer prior to operation402. In some embodiments, the sensors are connected to the wafer following operation402. In some embodiments, the sensors are embedded in a surface of the heating element. In some embodiments, the sensors include thermometers, thermocouples, or other suitable temperature measuring elements.

In some embodiments, the temperature of the heating element is monitored using a plurality of sensors positioned across a surface of the heating element. In some embodiments, the temperature of the heating element is monitored using a remote temperature sensing element. In some embodiments, the sensors are embedded in a surface of the heating element. In some embodiments, the sensors include thermometers, thermocouples, or other suitable temperature measuring elements. In some embodiments, the sensors on the wafer are located to correspond to a position of the sensors on the heating element. In some embodiments, the sensors on the wafer are located at positions which do not correspond to a position of the sensors on the heating element.

The temperature information related to the wafer and the heating element is provided to a controller. In some embodiments, the controller is configured to directly receive the temperature information. In some embodiments, the controller is configured to receive the temperature information from a relay or decoding element electrically between the sensors of at least one of the wafer or the heating element and the controller.

Method400continues with operation408in which a temperature of the heating element is controlled. The controller receives the temperature information, determines whether a temperature of the wafer or the heating element is different from a target temperature and generates instructions for adjusting the temperature of the heating element based on this determination. In some embodiments, the controller extends a time of the baking process based on the determined temperature variation.

In some embodiments, the controller individually controls heating zones of the heating element. In some embodiments, the controller sends a single heating signal to the heating element, the heating signal is then addressed to a specific heating zone by the heating element. In some embodiments the controller sends a separate signal to each heating zone of the heating element. In some embodiments, the controller controls individual heating zones in based on an amount of heat provided in adjacent heating zones. For example, control for heating zone1of heating element200(FIG. 2) is controlled based on an amount of heat provided in adjacent heating zones2-5.

In operation410, the baking process ends and the wafer is removed from the baking chamber. In some embodiments, the wafer is removed through a port in an outer wall of the baking chamber. In some embodiments, the wafer is removed through a same port through which the wafer is inserted in operation402. In some embodiments, the wafer is removed through a different port from the port through which the wafer is inserted in operation402. In some embodiments, the wafer is removed using a robotic arm. In some embodiments, the wafer is stored in a FOUP following removal from the baking chamber. In some embodiments, the port is configured to close following removal of the wafer.

FIG. 5is a block diagram of a general purpose computer system500for implementing instructions for using an adaptive baking system in accordance with one or more embodiments System500includes a hardware processor502and a non-transitory, computer readable storage medium504encoded with, i.e., storing, the computer program code506, i.e., a set of executable instructions. Computer readable storage medium504is also encoded with instructions507for interfacing with manufacturing machines for producing the memory array. The processor502is electrically coupled to the computer readable storage medium504via a bus508. The processor502is also electrically coupled to an I/O interface510by bus508. A network interface512is also electrically connected to the processor502via bus508. Network interface512is connected to a network514, so that processor502and computer readable storage medium504are capable of connecting to external elements via network514. The processor502is configured to execute the computer program code506encoded in the computer readable storage medium504in order to cause system500to be usable for performing a portion or all of the operations as described in method400.

In some embodiments, the processor502is a central processing unit (CPU), a multi-processor, a distributed processing system, an application specific integrated circuit (ASIC), and/or a suitable processing unit.

In some embodiments, the storage medium504stores the computer program code506configured to cause system500to perform method400. In some embodiments, the storage medium504also stores information needed for performing a method400as well as information generated during performing the method400, such as a target wafer temperature parameter520, a wafer temperature parameter522, a target heating element temperature parameter524, a heating element temperature parameter, a heating element layout parameter and/or a set of executable instructions to perform the operation of method400.

In some embodiments, the storage medium504stores instructions507for interfacing with manufacturing machines. The instructions507enable processor502to generate manufacturing instructions readable by the manufacturing machines to effectively implement method400during a manufacturing process.

System500also includes network interface512coupled to the processor502. Network interface512allows system500to communicate with network514, to which one or more other computer systems are connected. Network interface512includes wireless network interfaces such as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA; or wired network interface such as ETHERNET, USB, or IEEE-1394. In some embodiments, method400is implemented in two or more systems500, and information such as wafer temperature, heating element temperature and heating element layout are exchanged between different systems500via network514.

System500is configured to receive information related to a target wafer temperature through I/O interface510or network interface512. The information is transferred to processor502via bus508, the information is then stored in computer readable medium504as target wafer temperature parameter520. System500is configured to receive information related to wafer temperature through I/O interface510or network interface512. The information is stored in computer readable medium504as wafer temperature parameter522. System500is configured to receive information related to the target heating element temperature through I/O interface510or network interface. The information is stored in computer readable medium504as target heating element temperature524. System500is configured to receive information related to heating element temperature through I/O interface510or through network interface512. The information is stored in computer readable medium504as heating element temperature parameter526. System500is configured to receive information related to heating element layout through I/O interface510or network interface512. The information is stored in computer readable medium504as heating element layout parameter528.

During operation, processor502executes a set of instructions to determine a difference between the target wafer temperature and the wafer temperature as well as between the target heating element temperature and the heating element temperature. Processor502is configured to use this difference to determine whether to adjust an amount heat being provided by the heating element. Processor502is configured to use the heating element layout parameter528to determine which heating zone(s) to increase or decrease an amount of heat provided. In some embodiments, processor502is configured to extend an amount of time of a baking process based on the determined temperature variation. In some embodiments, processor502is configured to increase an amount of heat provided by the heating element as a temperature variation between the target wafer temperature and the wafer temperature or between the target heating element temperature and the heating element temperature increases. In some embodiments, processor502is configured to increase an amount of heat provided by the heating element as a largest heating element temperature variation between the target wafer temperature and the wafer temperature or between the target heating element and the heating element temperature increases. In some embodiments, processor502is configured to decrease an amount of heat provided by the heating element as a rate of change of the temperature of the heating element versus time increases.

One aspect of this description relates to an adaptive baking system. The adaptive baking system includes a baking chamber configured to receive a wafer, and a heating element configured to support the wafer. The adaptive baking system further includes a controller configured to receive temperature information related to the heating element and the wafer, wherein the controller is further configured to adjust an amount of heat provided by the heating element during a baking process in response to the temperature information.

Another aspect of this description relates to a method of using an adaptive baking system. The method includes supporting a wafer on a heating element, wherein the heating element is located in a baking chamber. The method further includes heating the wafer for a first duration using the heating element, and measuring a temperature of the heating element and a temperature of the wafer during the first duration. The method further includes adjusting an amount of heat provided by the heating element during the first duration based on the temperature of the heating element or the temperature of the wafer.

Still another aspect of this description relates to a controller for an adaptive baking system. The controller includes a non-transitory computer readable medium configured to store information related to a target temperature of a wafer, a target temperature of a heating element, a temperature of the wafer, and a temperature of the heating element. The controller further includes a processor connected to the non-transitory computer readable medium, the processor configured to generate at least one heating signal during a baking process to adjust an amount of heat provided by the heating element to the wafer.