Method and apparatus for processing wafers

Abstract

A device for providing plasma treatment is provided. A plasma treatment chamber is provided. A first turbo pump having an inlet is fluidly connected to the plasma treatment chamber and an exhaust section. A gas source supplies gas to the plasma treatment chamber. At least one gas pipeline is fluidly connected between the gas source and the plasma treatment chamber. At least one discharge pipeline is fluidly connected to the at least one gas pipeline. At least one gas pipeline valve is on the at least one gas pipeline and is positioned between the position where the at least one discharge pipeline is connected to the at least one gas pipeline and the plasma treatment chamber. At least one bypass valve is located on the at least one discharge pipeline.

Description

[0001] Cross - reference to Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 691,922, filed on June 29, 2018, which is incorporated herein by reference for all purposes. Technical Field

[0003] The present disclosure relates to methods for forming semiconductor devices on semiconductor wafers. More particularly, the present disclosure relates to maintaining uniformity between wafers while processing the wafers. Background Art

[0004] In the formation of semiconductor devices, an etch layer may be selectively etched relative to an organic patterning mask to form recessed feature memory holes or lines. Residues are deposited in the plasma processing chamber. The residues may be removed between the processing of each substrate / wafers. Summary of the Invention

[0005] To achieve the foregoing and in accordance with the purposes of the present disclosure, there is provided an apparatus for providing plasma etching. A plasma processing chamber, such as an etch chamber, is provided. A first turbo pump having an inlet is fluidly connected to the plasma processing chamber and an exhaust. A gas source supplies gas to the plasma processing chamber. At least one gas line is fluidly connected between the gas source and the plasma processing chamber. At least one discharge line is fluidly connected to the at least one gas line. At least one gas line valve is on the at least one gas line and is positioned between the location where the at least one discharge line is connected to the at least one gas line and the plasma processing chamber. At least one bypass valve is located on the at least one discharge line.

[0006] In another aspect, there is provided a method for processing wafers in a plasma processing system that includes a plasma processing chamber and at least one gas line. The method includes a plurality of cycles. Each cycle includes: placing a wafer in the plasma processing chamber; processing the wafer; removing the wafer from the plasma processing chamber; cleaning the interior of the etch chamber using a waferless clean; and purging the at least one gas line with an inert gas that includes at least one of nitrogen (N2), helium (He), and argon (Ar).

[0007] These and other features of the present disclosure will be described in more detail below in the detailed description and in conjunction with the following drawings. Brief Description of the Drawings

[0008] The present disclosure is illustrated by way of example and not limitation in the figures, and like reference numerals in the figures denote similar elements, wherein:

[0009] Figure 1 It is a schematic diagram of an etching chamber that can be used in one embodiment.

[0010] Figure 2 It is a schematic diagram of a computer system that can be used to implement an embodiment.

[0011] Figure 3 It is a high-level flowchart of one embodiment.

[0012] Figure 4 It is a schematic diagram of another embodiment.

[0013] Figure 5 It is a schematic diagram of another embodiment. Detailed Description of the Invention

[0014] The present disclosure will now be described in detail with reference to several preferred embodiments shown in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process steps and / or structures have not been described in detail so as not to unnecessarily obscure the present disclosure.

[0015] Figure 1 It is a schematic diagram of a plasma processing chamber that can be used in one embodiment. In one or more embodiments, the plasma processing chamber 100 includes a gas distribution plate 106 that provides a gas inlet and an electrostatic chuck (ESC) 108, which is located within the etching chamber 149 and surrounded by a chamber wall 152. Within the etching chamber 149, a wafer 103 is positioned above the ESC 108. An edge ring 109 surrounds the ESC 108. An ESC source 148 can provide a bias to the ESC 108. A gas source 110 is connected to the etching chamber 149 via a gas line 114 and the gas distribution plate 106. The gas line 114 has a gas line valve 116.

[0016] The radio frequency (RF) source 130 provides RF power to the lower electrode and / or the upper electrode, which are the ESC 108 and the gas distribution plate 106 respectively in this embodiment. In an exemplary embodiment, a 400 kHz power supply, a 60 MHz power supply, and optionally a 2 MHz power supply and a 27 MHz power supply constitute the RF source 130 and the ESC source 148. In this embodiment, the upper electrode is grounded. In this embodiment, a generator is provided for each frequency. In other embodiments, the generators may be in separate RF sources, or separate RF generators may be connected to different electrodes. For example, the upper electrode may have an inner electrode and an outer electrode connected to different RF sources. Other arrangements of RF sources and electrodes may be used in other embodiments. The inlet side of the turbopump 120 is fluidly connected to the etching chamber 149.

[0017] The inlet side of the dry pump 124 is fluidly connected to the exhaust side of the turbopump 120. The discharge line 128 is connected between the gas line 114 and the etching chamber 149. The discharge line 128 has a discharge line valve 129. The plasma region 132 is the region in the etching chamber 149 where plasma is generated. A gas flowing through the gas line 114 and the gas distribution plate 106 is provided at a first side of the plasma region 132 such that the gas passes through the plasma region 132 and reaches the turbopump 120. The gas flowing through the discharge line 128 is provided to the etching chamber 149 at a second side of the plasma region 132 such that the gas flowing from the discharge line 128 does not pass through the plasma region 132 and reach the turbopump 120. The controller 135 is controllably connected to the RF source 130, the ESC source 148, the turbopump 120, the gas line valve 116, the discharge line valve 129, and the gas source 110. An example of such an etching chamber is the Exelan Hex manufactured by Lam Research Corporation (Fremont, CA). TM Etching system. The processing chamber can be a CCP (capacitively coupled plasma) reactor or an ICP (inductively coupled plasma) reactor.

[0018] Figure 2FIG. 0 is a high-level block diagram showing a computer system 200 that is adapted to implement the controller 135 used in the embodiments. The computer system can have a variety of physical forms, ranging from integrated circuits, printed circuit boards, and small handheld devices to giant supercomputers. The computer system 200 includes one or more processors 202, and may further include an electronic display device 204 (for displaying graphics, text, and other data), a main memory 206 (e.g., random access memory (RAM)), a storage device 208 (e.g., a hard disk drive), a removable storage device 210 (e.g., a CD drive), a user interface device 212 (e.g., a keyboard, touch screen, keypad, mouse, or other pointing device, etc.), and a communication interface 214 (e.g., a wireless network interface). The communication interface 214 enables software and data to be transmitted between the computer system 200 and external devices via a link. The system may also include a communication infrastructure 216 (e.g., a communication bus, crossbar, or network), to which the aforementioned devices / modules are connected.

[0019] The information transmitted via the communication interface 214 can be in the form of signals that can be received by the communication interface 214 via a communication link, and the signals are, for example, electrical, electromagnetic, optical, or other signals. The communication link carries the signals and can be a communication link implemented using wires or cables, optical fibers, telephone lines, cellular phone links, radio frequency links, and / or other communication channels. With such a communication interface, it is expected that one or more processors 202 can receive information from a network or output information to a network during the process of implementing the above method steps. Additionally, method embodiments can be executed only on a processor or can be executed in combination with a remote processor that shares part of the processing on a network such as the Internet.

[0020] The term "non-transitory computer-readable medium" generally refers to media such as main memory, auxiliary memory, removable storage devices, and storage devices (e.g., hard disks, flash memories, hard drive memories, CD-ROMs, and other forms of permanent memory), and should not be construed to cover transient subject matter such as carrier waves or signals. Examples of computer code include machine code, such as machine code generated by a compiler, and files including higher-level code that is executed by a computer using an interpreter. A computer-readable medium can also be computer code transmitted via a computer data signal embodied in a carrier wave and represented as a sequence of instructions executable by a processor.

[0021] Figure 3High-level flowchart of an embodiment. In this embodiment, a wafer having an etch layer under an organic patterning mask is placed in a plasma processing chamber (step 304). The etch layer is etched (step 308). The wafer is removed from the plasma processing chamber (step 312). The plasma processing chamber is cleaned (step 316). At least one gas line is purged (step 320). The process is repeated by proceeding to step 304 and placing another wafer in the plasma processing chamber.

[0022] Example

[0023] In an exemplary embodiment, a wafer 103 having an etch layer under an organic patterning mask is placed in a plasma processing chamber 100 (step 304). After the wafer 103 is placed in the plasma processing chamber 100, the etch layer is etched (step 308). In this embodiment, the etch layer is a silicon oxide (SiO2) layer above the wafer 103 and under a photoresist mask. The wafer 103 is removed from the plasma processing chamber 100 (step 312).

[0024] The plasma processing chamber 100 is cleaned (step 316). In this embodiment, waferless automatic cleaning (WAC) is used. An exemplary recipe for WAC provides a flow of 800 sccm of O2 into the plasma processing chamber 100. 400 watts of RF power at a frequency of 600 MHz is provided to convert the O2 gas into plasma. The plasma cleans the residues in the plasma processing chamber 100.

[0025] The gas line 114 is purged (step 320). In this embodiment, the oxygen remaining in the gas line 114 is removed. The gas line valve 116 is closed and the exhaust line valve 129 is opened. The turbo pump 120 continuously provides vacuum. The oxygen in the gas line 114 is drawn through the exhaust line 128 and the plasma processing chamber 100 into the turbo pump 120. Any remaining oxygen from the gas line 114 is purged. The cycle is repeated by placing another wafer 103 in the plasma processing chamber 100.

[0026] It has been found that in the prior art, the length of the idle time between the completion of the cleaning of the plasma processing chamber 100 and the start of the etching of the etched layer affects the critical dimension (CD) of the etching of the etched layer, which is referred to as the idle effect. Due to the idle effect, the CD uniformity between wafers is reduced, thereby increasing semiconductor device defects. Reducing or eliminating the idle effect has been studied for many years. Without being limited by theory, it has been unexpectedly found that residual oxygen in the gas line 114 after cleaning the plasma processing chamber 100 leaks into the plasma processing chamber 100. The leaked oxygen removes some of the organic patterning masks, which causes the CD to change. Therefore, it has been unexpectedly found that the operation of purging oxygen from the gas line 114 reduces or eliminates the idle effect.

[0027] In the process of determining whether the residual oxygen in the gas line causes the observed reduction in CD uniformity, an experiment of purging oxygen from the gas line was conducted. It was unexpectedly found that this purging operation increased the CD uniformity by at least four times.

[0028] In one embodiment, since the turbo pump 120 has a single inlet connection, the discharge line 128 is connected to the inlet of the turbo pump 120 via the plasma processing chamber 100. The discharge line 128 is connected to the plasma processing chamber 100 near the inlet of the turbo pump 120. The connection position between the discharge line 128 and the plasma processing chamber 100 allows gas to flow from the discharge line 128 to the turbo pump 120 without passing through the plasma region 132.

[0029] The plasma processing chamber 100 can be a module of a large wafer processing system. Such a wafer processing system may have a load lock and a wafer transfer module that transfers wafers between the load lock and various processing chambers. In some embodiments, the time taken to transfer a wafer to the plasma processing chamber 100 via the wafer transfer module is approximately the same as the time taken to purge the gas line (step 320). Therefore, the wafer transfer can be performed simultaneously with the gas line purge (step 320). In such an embodiment, the gas line purge (step 320) does not increase the total processing time.

[0030] Figure 4Schematic diagram of another embodiment of the plasma processing chamber 400. The etching chamber 449 is connected to the turbopump 420. Further, the turbopump 420 is connected to the dry pump 424. Generally, the turbopump 420 can pump to a pressure of about 10-8 mTorr. The dry pump 424 can pump to a pressure of about 10 mTorr. The gas source 410 supplies gas to the etching chamber 449. The first gas pipeline 414a is connected between the gas source 410 and the central region at the top of the etching chamber 449. The first gas pipeline valve 416a is located on the first gas pipeline 414a. The second gas pipeline 414b is connected between the gas source 410 and the peripheral region at the top of the etching chamber 449. The second gas pipeline valve 416b is located on the second gas pipeline 414b.

[0031] The first discharge pipeline 428a is connected to the first gas pipeline 414a. The first discharge pipeline valve 429a is located on the first discharge pipeline 428a. The second discharge pipeline 428b is connected to the second gas pipeline 414b. The second discharge pipeline valve 429b is located on the second discharge pipeline 428b. The first discharge pipeline 428a and the second discharge pipeline 428b are connected to the bottom chamber pipeline 432, and the bottom chamber pipeline 432 is connected to the bottom of the etching chamber 449. The bottom chamber pipeline 432 has a bottom chamber pipeline valve 434. The helium extraction pipeline 436 extends from the etching chamber 449 to the bottom chamber pipeline 432. The helium extraction pipeline 436 has an extraction valve 438. The bottom chamber pipeline 432 is also fluidly connected to the dry pump 424. The controller 435 is controllably connected to the etching chamber 449, the turbopump 420, the dry pump 424, the gas source 410, the first gas pipeline valve 416a, the second gas pipeline valve 416b, the first discharge pipeline valve 429a, the second discharge pipeline valve 429b, the bottom chamber pipeline valve 434, and the extraction valve 438.

[0032] In an exemplary embodiment, a wafer (not shown) having an etched layer under an organic patterning mask is placed in the etching chamber 449 (step 304). After the wafer (not shown) is placed in the etching chamber 449, the etched layer is etched (step 308). In this embodiment, the etched layer is a silicon oxide (SiO2) layer above the wafer (not shown) and under the photoresist mask. The etching gas is made to flow from the gas source 410 into the etching chamber 449. The etching gas is converted into a plasma, which etches the etched layer on the wafer (not shown). The wafer (not shown) is removed from the etching chamber 449 (step 312).

[0033] Clean the interior of the etching chamber 449 (step 316). In this embodiment, the first gas line 414a and the second gas line 414b are used to flow the cleaning gas from the gas source 410 to the etching chamber 449. In this embodiment, the cleaning gas contains oxygen. Sweep the first gas line 414a and the second gas line 414b (step 320). In this embodiment, the oxygen remaining in the first gas line 414a and the second gas line 414b is removed. Close the first gas line valve 416a and the second gas line valve 416b, and open the first discharge line valve 429a and the second discharge line valve 429b. The turbo pump 420 continuously provides a vacuum. The oxygen in the first gas line 414a and the second gas line 414b is respectively drawn through the first discharge line 428a and the second discharge line 428b and the etching chamber 449 and into the turbo pump 420. The residual oxygen in the first gas line 414a and the second gas line 414b is swept away. Repeat this cycle by placing another wafer (not shown) in the etching chamber 449. The turbo pump 420 operates continuously during each cycle.

[0034] This embodiment provides for the sweeping of more than one gas line. Multiple gas lines enable different gas zones to provide different gases, or different gas flow rates, or different gas ratios.

[0035] Figure 5 Schematic diagram of another embodiment of the plasma processing chamber 500. The etching chamber 549 is connected to the turbo pump 520. The turbo pump 520 is in turn connected to the dry pump 524. The gas source 510 supplies gas to the etching chamber 549. The gas source 510 includes an oxygen (O2) source 511, a nitrogen (N2) source 512, and other gas sources 513. The first gas line 514a is connected between the gas source 510 and the central region at the top of the etching chamber 549. The first gas line valve 516a is located on the first gas line 514a. The second gas line 514b is connected between the gas source 510 and the peripheral region at the top of the etching chamber 549. The second gas line valve 516b is located on the second gas line 514b. The helium extraction line 536 extends from the etching chamber 549 to the dry pump 524. The helium extraction line 536 has an extraction valve 538. The controller 535 is controllably connected to the etching chamber 549, the turbo pump 520, the dry pump 524, the gas source 510, the first gas line valve 516a, the second gas line valve 516b, and the extraction valve 538.

[0036] In an exemplary embodiment, a wafer (not shown) having an etch layer under an organic patterning mask is placed in an etch chamber 549 (step 304). After the wafer (not shown) is placed in the etch chamber 549, the etch layer is etched (step 308). In this embodiment, the etch layer is a silicon oxide (SiO2) layer above the wafer (not shown) and under a photoresist mask. The wafer (not shown) is removed from the etch chamber 549 (step 312).

[0037] The etch chamber 549 is cleaned (step 316). In this embodiment, both the first gas line 514a and the second gas line 514b are used to flow a cleaning gas from the gas source 510 to the etch chamber 549. In this embodiment, the cleaning gas contains oxygen. The first gas line 514a and the second gas line 514b are purged (step 320). In this embodiment, the first gas line valve 516a and the second gas line valve 516b remain open. The turbopump 520 continuously provides a vacuum. A purge gas (e.g., N2) inert to the patterned organic mask flows out from the N2 source 512. In this embodiment, at least 1000 sccm of N2 flows through the first gas line 514a and the second gas line 514b. In this example, the purge operation of the first gas line 514a and the second gas line 514b occurs for about 10 seconds. Preferably, the purge operation occurs for at least 3 seconds. Other embodiments provide a purge operation for at least 5 seconds. Residual oxygen in the first gas line 514a and the second gas line 514b is purged by the flow of the purge gas. This cycle is repeated by placing another wafer in the etch chamber 549. In other embodiments, other gas line arrangements can be sufficiently purged with a lower N2 flow rate.

[0038] In other embodiments, the purge gas can be argon (Ar) or helium (He). Other embodiments flow at least 2000 sccm of the purge gas. Other embodiments can use other methods to purge the gas line 114 after cleaning the etch chamber 149. Other embodiments can have three or more gas lines 114. Other embodiments can provide a method or apparatus for etching dielectric or conductive materials. In another embodiment, the discharge line 128 can be connected to a second turbopump to purge the gas line 114. Other embodiments can have a deposition process or other wafer processes instead of an etch process.

[0039] Although the present disclosure has been described in terms of several preferred embodiments, there are changes, modifications, substitutions and various alternative equivalents that fall within the scope of the present disclosure. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present disclosure. Accordingly, the appended claims are intended to be construed to include all such changes, modifications, substitutions and various alternative equivalents that fall within the true spirit and scope of the present disclosure.

Claims

1. An apparatus for providing plasma processing to a substrate, comprising: A plasma processing chamber having a plasma region; A first turbo pump having an inlet and an exhaust section, the inlet being fluidly connected to the plasma processing chamber; A gas source for providing gas to the plasma processing chamber; At least one gas line connected to the gas source and the plasma processing chamber, wherein the at least one gas line is connected to the plasma processing chamber on a first side of the plasma region such that the gas provided by the at least one gas line is provided on the first side of the plasma region above the substrate, thereby allowing the gas from the at least one gas line to pass through the plasma region; At least one discharge line connected to the at least one gas line, wherein the at least one discharge line is connected to the plasma processing chamber below the substrate such that the gas provided by the at least one discharge line enters the plasma processing chamber below the substrate and flows to the inlet of the first turbo pump without passing through the plasma region of the plasma processing chamber, wherein, after cleaning the plasma processing chamber, oxygen in the at least one gas line is drawn through the at least one discharge line and the plasma processing chamber into the first turbo pump, thereby scavenging residual oxygen from the at least one gas line; At least one gas line valve on the at least one gas line and positioned between the location where the at least one discharge line is connected to the at least one gas line and the plasma processing chamber; At least one bypass valve located on the at least one discharge line; A dry pump having an inlet fluidly connected to the exhaust section of the first turbo pump, wherein the at least one discharge line is fluidly connected to the dry pump; and At least one extraction valve connected between the at least one discharge line and the dry pump.

2. The apparatus according to claim 1, further comprising a controller controllably connected to the at least one gas line valve and the at least one bypass valve and the gas source, wherein the controller comprises: At least one processor; and A computer-readable medium comprising computer code for providing a plurality of cycles, wherein each cycle comprises: Opening the at least one gas line valve and closing the at least one bypass valve; Transferring a first wafer into the plasma processing chamber; Etching an etched layer on the first wafer in the plasma processing chamber; Removing the first wafer from the plasma processing chamber; Providing a waferless clean of the plasma processing chamber; And Scavenging the gas in the at least one gas line via the at least one discharge line after providing the waferless clean, wherein the controller causes the gas to enter the plasma processing chamber from the at least one gas line and reach the inlet of the turbo pump without passing through the plasma region.

3. The apparatus according to claim 2, wherein purging the gas in the at least one gas line comprises closing the at least one gas line valve and opening the at least one bypass valve so that the gas in the at least one gas line can be emptied through the at least one discharge line.

4. The apparatus according to claim 3, further comprising a wafer transfer module connected to the plasma processing chamber, wherein, After providing the waferless cleaning, the purging is performed when the wafer is transferred to the plasma processing chamber via the wafer transfer module.

5. The apparatus according to claim 2, wherein an inert gas comprising at least one of nitrogen (N2), helium (He), and argon (Ar) is used to purge the gas in the at least one gas line.

6. The apparatus according to claim 2, wherein each cycle further comprises: after purging the gas in the at least one gas line, transferring a second wafer having an etched layer into the plasma processing chamber; and etching the etched layer on the second wafer in the plasma processing chamber.

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