Semiconductor manufacturing method with reduced wafer excursion

Abstract

A semiconductor manufacturing method includes placing a wafer on a tray in a processing chamber, wherein the processing chamber has a gas flow rate according to a gas inlet means and / or a gas exhaust means; maintaining the gas flow rate of the processing chamber at a first low flow rate to perform a first process; increasing the gas flow rate of the processing chamber from the low flow rate to a high flow rate to perform a second process; and after the second process, decreasing the gas flow rate of the processing chamber from the high flow rate to a second low flow rate.

Description

TECHNICAL FIELD

[0001] The present invention relates to a semiconductor manufacturing method, and more particularly to a method for securing a wafer on a heated chuck during a process requiring a high flow gas environment. BACKGROUND

[0002] In semiconductor processing, throughput has always been a challenge. As technology advances, wafers must be processed in a continuous and efficient manner. For example, multi-chamber processing equipment or cluster tools have met this need by processing multiple wafers in batches in a configuration of multiple stations, which can be maintained at the same or different environmental conditions to achieve uniform or varied wafer processing. Such multi-chamber equipment has replaced the practice of processing a single wafer and then exposing the wafer to air during the time it is transferred to another chamber. By connecting multiple processing chambers to a common transfer chamber, wafers can be transferred from one processing chamber to the next in the same vacuum environment after processing is completed in a chamber.

[0003] Known processes include various plasma-enhanced processes such as film deposition, etching, and chamber cleaning. Chambers for performing such plasma processes typically have radio frequency components for applying radio frequency power to certain parts of the chamber (e.g., between a support pedestal and a showerhead or chamber wall) to ionize and introduce a particular gas into the chamber for chemical processing. For example, in a chamber dry cleaning process, radio frequency energy can be applied to a gas such as H2, NH3, Ar, or N2 through a showerhead to activate the selected gas and contact the interior surfaces of the chamber for cleaning.

[0004] In some processes for wafers, the environment of the processing chamber needs to be maintained at a specific gas flow rate to ensure that the reaction gas can effectively cover the desired processing range. For example, in some deposition processes, the in-chamber gas flow rate needs to be maintained at 8 LPM or more per station, which is a relatively high flow rate throughout the process. Generally, the wafer being processed is placed on a support pedestal, and some support pedestals have a disk surface formed with a sunken space for receiving the wafer, and the diameter of the sunken space is greater than the diameter of the wafer. It has been found that the wafer in the high flow environment, especially the wafer received in the sunken space of the pedestal, can be affected by the gas flow and vibrate, causing the wafer to be relatively displaced from the disk surface by a considerable degree. Of course, the displacement phenomenon can be solved by hardware means, such as adding a limiting member or a correction device, but it also relatively brings the cost of manufacturing.

[0005] Therefore, it is necessary to develop a non-hardware solution to control the wafer offset caused by the high flow environment within an acceptable range. SUMMARY

[0006] The present application provides a semiconductor manufacturing method, comprising: placing a wafer on a tray in a processing chamber, wherein the processing chamber has a gas flow according to an inlet means and / or an exhaust means; maintaining the gas flow of the processing chamber at a first low flow to perform a first processing; increasing the gas flow of the processing chamber from the low flow to a high flow to perform a second processing; and after the second processing, decreasing the gas flow of the processing chamber from the high flow to a second low flow.

[0007] In one embodiment, the first processing at the first low flow is a preheating processing of the processing chamber.

[0008] In one embodiment, the method further comprises, before increasing from the first low flow to the high flow, increasing the environment in the processing chamber from a first pressure to a second pressure, the second pressure being suitable for a process.

[0009] In one embodiment, the method further comprises, before increasing from the low flow to the high flow, applying a radio frequency power to the tray so that the tray attracts the wafer by Coulomb force.

[0010] In one embodiment, the second processing is a deposition processing of introducing a reaction gas into the processing chamber.

[0011] In one embodiment, the radio frequency power is maintained to be applied to the tray during the decreasing from the high flow to the second low flow.

[0012] In one embodiment, the method further comprises, after the high flow decreases to the second low flow, decreasing the radio frequency power to zero.

[0013] In one embodiment, the method further comprises, after the high flow decreases to the second low flow, decreasing from the second pressure to a third pressure.

[0014] In one embodiment, the tray is a heating tray and has a sunken space for accommodating the wafer, the diameter of the sunken space being greater than the diameter of the wafer.

[0015] In one embodiment, the low flow is between 1.1 to 2.0 liters / minute, and the high flow is between 5.0 to 11.6 liters / minute. BRIEF DESCRIPTION OF DRAWINGS

[0016] The application can be more fully understood with reference to the following drawings and descriptions. Non-limiting and non-exhaustive examples are described with reference to the following figures. The components in the figures are not necessarily to scale; emphasis is instead placed upon illustrating the structures and principles of the application.

[0017] Figure 1 A schematic view of a semiconductor processing chamber.

[0018] Figure 2 A flow chart of a semiconductor manufacturing method according to the present application.

[0019] Figure 3 A schematic view of gas pressure / flow rate versus time in a chamber, showing a ramp up.

[0020] Figure 4 A schematic view of gas pressure / flow rate versus time in a chamber, showing a step up.

[0021] In the figure, 100, chamber wall; 101, showerhead assembly; 102, support pedestal; 103, gas source; 104, remote plasma source; 105, RF power source; 106, tray; 107, metal layer; 108, pump. DETAILED DESCRIPTION

[0022] The application will be more fully understood with reference to the following figures and description. Non-limiting and non-exhaustive examples are described with reference to the following figures. The components in the figures are not necessarily to scale; emphasis is instead placed upon illustrating the structures and principles of the application.

[0023] The use of the word "an" or "one" to describe the application does not foreclose the use of more than one, and "or" does not foreclose the use of more than one. The conjunctive term "and" does not foreclose the conjunctive term "or". The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. The term "one" or "another" does not foreclose the use of more than one.

[0024] Figure 1A schematic of a semiconductor processing chamber, particularly a processing chamber capable of applying RF power, is shown. The chamber generally includes a chamber wall 100, a showerhead assembly 101 disposed at the top of the chamber wall 100, and a support pedestal 102. A wafer W is disposed in a chamber defined by the chamber wall 100 to undergo various processes. The showerhead assembly 101 is fluidly coupled to a gas source 103 and a remote plasma source 104. The remote plasma source 104 receives one or more gases from the gas source 103 and ionizes the gases for introduction into the chamber through the showerhead assembly 101. The showerhead assembly 101 can also be electrically coupled to an RF power source 105. The RF power source 105 applies an appropriate RF power to the showerhead assembly 101 to enable the gases passing through the showerhead to be ionized to form a plasma. In most operations, the remote plasma source 104 and the RF power source 105 are optional.

[0025] The wafer W is disposed on a tray 106 of the support pedestal 102. Generally, the tray 106 is configured as a heated platen having heating coils to heat the wafer W disposed on the platen. The tray 106 also has a grounded metal layer 107 to enable the plasma to chemically react with the wafer W disposed on the tray 106. The reacted gases can be pumped out of the chamber by a pump 108 coupled to the bottom of the chamber wall 100.

[0026] As shown, the tray 106 can be formed with a sink space having a radial dimension greater than the wafer to enable the wafer W to be disposed in the sink space and to be constrained to the center of the tray 106. As previously mentioned, however, the sink space is not intended to precisely constrain the position of the wafer W relative to the tray 106, and the wafer W can shift due to jostling in a high flow chamber environment.

[0027] Figure 2 A flow diagram of a method of the present application is shown, including steps S200 through S209. Using the method of the present application, the jostling and shifting of the wafer in a high flow environment can be reduced to an acceptable range without requiring additional hardware in the configuration of the chamber. For example, the relative shift between the wafer W and the tray 106 can be within 1 mm to be acceptable. It should be appreciated that the flow diagram shown is with respect to, but not limited to, a plasma deposition process.

[0028] The flow begins at step S200 by loading a wafer to be processed on a tray of a processing chamber, such as the chamber shown in FIG. 1. Figure 1The wafer is transferred from a vacuum environment of a transfer chamber to a processing chamber which is also maintained in a vacuum environment. After the wafer is placed in the processing chamber, the showerhead assembly and / or the pump in the processing chamber can be operated to fill the processing chamber with a process gas (non-reactive gas) to change the pressure of the processing chamber to a process pressure. The process gas is flowed into the processing chamber at a first low flow rate of 1.1 to 2.0 LPM (liters per minute) to preheat the wafer to a desired temperature. The preheating step S200 is completed.

[0029] In step S201, the pressure in the processing chamber is increased to a process pressure. The pressure is increased according to one or more linear relationships or according to a step relationship. Referring to FIG. 2, the pressure is increased according to a linear relationship. The pressure is increased according to a step relationship in FIG. 3. Figure 3 The pressure is increased according to a linear relationship in FIG. 2. Preferably, the linear relationship has a slope of 0.1 to 1.0 torr / s. Although a single slope linear relationship is shown from an initial pressure / flow rate to a target pressure / flow rate, a multi-slope linear relationship is also possible in alternative embodiments. Referring to FIG. 2, the pressure is increased according to a linear relationship. The pressure is increased according to a step relationship in FIG. 3. Figure 3 The pressure is increased according to a linear relationship in FIG. 2. Preferably, the linear relationship has a slope of 0.1 to 1.0 torr / s. Although a single slope linear relationship is shown from an initial pressure / flow rate to a target pressure / flow rate, a multi-slope linear relationship is also possible in alternative embodiments. Referring to FIG. 2, the pressure is increased according to a linear relationship. The pressure is increased according to a step relationship in FIG. 3. Figure 4 The pressure is increased according to a linear relationship in FIG. 2. Preferably, the linear relationship has a slope of 0.1 to 1.0 torr / s. Although a single slope linear relationship is shown from an initial pressure / flow rate to a target pressure / flow rate, a multi-slope linear relationship is also possible in alternative embodiments. Referring to FIG. 2, the pressure is increased according to a linear relationship. The pressure is increased according to a step relationship in FIG. 3.

[0030] In step S202, a suitable RF power is applied to the processing chamber through the showerhead assembly 20 to induce a Coulomb force in the metal layer of the wafer to secure the wafer to the wafer support. The RF power is not necessarily the same as the RF power used in the plasma process. Although the flow chart shows step S202 after step S201, the two steps can be performed in either order or simultaneously. In other processes that do not involve plasma processing, step S202 can be omitted. Figure 1

[0031] ​Step S203, the gas flow rate in the chamber is increased from the first low flow rate to a process flow rate. The process flow rate is the flow rate suitable for the plasma deposition process. The increase is according to the linear relationship or the step relationship as described above. As shown in Figures 3 and 4, preferably, the linear relationship for the flow rate increase has a slope between 100 seem / s and 2500 seem / s, and the time interval (Tl, T2) for the stage increase has a range between 2 seconds and 10 seconds. In this way, the change of the gas flow rate in the chamber is more gradual, and the disturbance to the wafer is reduced. The process flow rate is relatively high during the process, and has a range between 5.0 LPM and 11.6 LPM. The gas flow rate in the chamber reaches the process flow rate, and step S203 is completed.

[0032] Step S204, the reaction gas is introduced into the processing region in the chamber through the showerhead assembly to react with the wafer. The reaction gas can be a mixture of gases that are ionized in the showerhead assembly. The reaction gas contains the material used to form the deposition film. The wafer is reacted in the process environment suitable for the specific process in this step, as in the known process. However, the relative displacement between the wafer and the pedestal is ensured to be within an acceptable range by the preceding steps S201 to S203. Therefore, the wafer is still within a predetermined deposition range, and the manufacturing yield is improved. Step S205, the valve for delivering the reaction gas is closed, or the reaction gas is directed to bypass the processing chamber (not to enter the processing region in the chamber), to end the deposition process.

[0033] Step S206, the gas flow rate in the chamber is decreased from the high flow rate suitable for the process to a second low flow rate. Although only the linear relationship is shown in the figure, the decreasing trend can also be according to a linear relationship or a step relationship. Preferably, the linear relationship for the flow rate decrease has a slope between 100 seem / s and 2500 seem / s, and the time interval (dwell time) for the stage decrease has a range between 2 seconds and 10 seconds. In addition, the RF power applied to the process can be adjusted appropriately but not zero during the flow rate decrease, so that the wafer is still attracted to the pedestal by the Coulomb force. In step S207, when the gas flow rate in the chamber is decreased to a predetermined flow rate or to the second low flow rate, the RF power is decreased to between 0 and 50 W, and the next step is directly set to 0, and step S207 is completed. Figure 3 Figure 4 Step S208, the pressure in the chamber is decreased to a lower pressure. Although only the linear relationship is shown in the figure, the decreasing trend can also be according to a linear relationship or a step relationship. Preferably, the linear relationship for the pressure decrease has a slope between 100 Torr / s and 2500 Torr / s, and the time interval (dwell time) for the stage decrease has a range between 2 seconds and 10 seconds. In addition, the RF power applied to the process can be adjusted appropriately but not zero during the pressure decrease, so that the wafer is still attracted to the pedestal by the Coulomb force. In step S209, when the pressure in the chamber is decreased to a predetermined pressure or to the lower pressure, the RF power is decreased to between 0 and 50 W, and the next step is directly set to 0, and step S209 is completed.

[0034] Step S208, the pressure in the chamber is decreased to a lower pressure. Although only the linear relationship is shown in the figure, the decreasing trend can also be according to a linear relationship or a step relationship. Preferably, the linear relationship for the pressure decrease has a slope between 100 Torr / s and 2500 Torr / s, and the time interval (dwell time) for the stage decrease has a range between 2 seconds and 10 seconds. In addition, the RF power applied to the process can be adjusted appropriately but not zero during the pressure decrease, so that the wafer is still attracted to the pedestal by the Coulomb force. In step S209, when the pressure in the chamber is decreased to a predetermined pressure or to the lower pressure, the RF power is decreased to between 0 and 50 W, and the next step is directly set to 0, and step S209 is completed. Figure 3 Figure 4 ​​The pressure / rate rise curve of the present application is illustrated, and the falling trend described herein can also be based on a linear relationship or a step relationship. Preferably, the linear relationship based on the pressure drop can have a slope between 0.1 torr / s and 1 torr / s, and the time interval (dwell time) of the falling rate can be in the range of 2 s to 50 s. The ambient pressure is reduced to a predetermined pressure, and step S208 is ended. In step S209, the gas valve is closed, and any gas supply to the chamber of the processing chamber is stopped. Conversely, the pump can be started to pump out the residual gas in the chamber ambient until the chamber ambient pressure matches the transfer chamber ambient pressure.

[0035] In an experimental example, a multi-station processing chamber was tested using the method of the present application. The multi-station processing chamber has six processing chambers. In a wafer-to- processing chamber offset test, the processing of wafers was performed multiple times using the method of the present application with high flow and no gas supply, respectively, and the results showed that the horizontal offset of the wafer relative to the tray can be controlled within 1 mm, and the relative offset between the wafers placed in front and back can be controlled within 0.5 mm.

[0036] In summary, the semiconductor manufacturing method of the present application is mainly based on a specific pressure and flow control strategy, i.e., the control of the pressure and flow is based on a specific linear relationship or step relationship, which ensures that the wafer in the chamber ambient with high flow is still maintained within an acceptable offset range, without the need for additional limiting hardware or correction mechanisms.

Claims

1. A semiconductor manufacturing method, characterized by, Comprising: placing a wafer on a tray in a processing chamber, wherein the tray is a heated tray and has a sink space for accommodating the wafer, the sink space has a diameter greater than that of the wafer, the processing chamber has a gas flow according to an inlet means and / or an exhaust means; maintaining the gas flow of the processing chamber at a first low flow to perform a first processing; increasing the gas flow of the processing chamber from the first low flow to a high flow to perform a second processing, and after the second processing, decreasing the gas flow of the processing chamber from the high flow to a second low flow, wherein the first low flow and the second low flow are between 1.1 to 2.0 liter / minute, the high flow is between 5.0 to 11.6 liter / minute, before increasing from the first low flow to the high flow, the environment in the processing chamber is ramped up from a first pressure to a second pressure, the second pressure is suitable for a process, before increasing from the low flow to the high flow, a radio frequency power is applied to the tray to make the tray attract the wafer with a coulomb force.

2. The method of claim 1, wherein: wherein the first processing at the first low flow is a preheating processing of the processing chamber.

3. The method of claim 1, wherein: wherein the second processing is a deposition processing of passing a reaction gas into the processing chamber.

4. The method of claim 1, wherein: wherein during the process of decreasing from the high flow to the second low flow, the radio frequency power applied to the tray is maintained.

5. The method of claim 1, wherein, further comprising: after the high flow is decreased to the second low flow, decreasing the radio frequency power to zero.

6. The method of claim 1, wherein, further comprising: after the high flow is decreased to the second low flow, decreasing from the second pressure to a third pressure.

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