HIGH SPEED INJECTION NOZZLE FOR PRE-POLISH MODIFICATION OF SUBSTRATE THICKNESS

Abstract

A method of fabrication of a substrate includes, after deposition of an outer layer on a substrate and before polishing of an exposed surface of the outer layer of the substrate, performing a hydroblasting treatment of a selected portion of the exposed surface by directing a treatment liquid from a nozzle at a sufficiently high velocity onto the selected portion to remove material from the selected portion such that a thickness non-uniformity of the outer layer is reduced. Then the outer layer of the treated substrate is subject to chemical mechanical polishing to planarize and reduce a thickness of the outer layer.

Description

TECHNICAL FIELD

The present disclosure relates to chemical mechanical polishing, and more particularly to modifying a substrate thickness profile prior to polishing.

BACKGROUND

An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. A variety of fabrication processes require planarization of a layer on the substrate. For example, one fabrication step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. For certain applications, the filler layer is planarized until the top surface of a patterned layer is exposed. For example, a metal layer can be deposited on a patterned insulative layer to fill the trenches and holes in the insulative layer. After planarization, the remaining portions of the metal in the trenches and holes of the patterned layer form vias, plugs, and lines to provide conductive paths between thin film circuits on the substrate.

Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. A polishing slurry with abrasive particles is typically supplied to the surface of the polishing pad.

SUMMARY

In one aspect, a method of fabrication of a substrate includes, after deposition of an outer layer on a substrate and before polishing of an exposed surface of the outer layer of the substrate, performing a hydroblasting treatment of a selected portion of the exposed surface by directing a treatment liquid from a nozzle at a sufficiently high velocity onto the selected portion to remove material from the selected portion such that a thickness non-uniformity of the outer layer is reduced. Then the outer layer of the treated substrate is subject to chemical mechanical polishing to planarize and reduce a thickness of the outer layer.

In another aspect, a hydroblasting treatment station for modification of a substrate undergoing integrated circuit fabrication includes a chuck to hold the substrate, a nozzle coupled to a source of treatment liquid, the nozzle laterally movable relative to the substrate, and a controller configured to cause the nozzle to direct the treatment liquid at a sufficiently high velocity onto the selected portion to remove material from the selected portion such that a thickness non-uniformity of an outer layer of the substrate is reduced.

Implementations can optionally include, but are not limited to, one or more of the following advantages. The substrate layer thickness can be more uniform prior to polishing, which can make control of polishing parameters during polishing easier, and can improve polishing uniformity and reduce within-wafer-nonuniformity (WIWNU) of the polished substrate.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of a substrate after a deposition process.

FIG. 2 is a schematic cross-sectional view of a substrate during treatment by fluid ejected from a high-speed nozzle.

FIG. 3 is a schematic cross-sectional view of a substrate after the treatment.

FIG. 4 is a schematic cross-sectional view of a substrate being polished.

FIG. 5 is a schematic cross-sectional view of a substrate after being polished.

FIG. 6 is a schematic cross-sectional view of a hydroblasting treatment station.

FIG. 7 is a schematic top view of the hydroblasting treatment station of FIG. 6.

FIG. 8 is a schematic cross-sectional view of another implementation of a hydroblasting treatment station.

DETAILED DESCRIPTION

A typical semiconductor fabrication process includes deposition of a layer, followed by chemical mechanical polishing of that layer to remove the layer until a desired thickness remains or an underlying layer is exposed. If the underlying layer is patterned, then the deposited layer typically has some small-scale topography, e.g., on the order of nanometers, resulting from the deposited layer filling trenches or holes required for the integrated circuit. This small-scale topography can be removed, i.e., the substrate can be planarized, by the polishing process.

Some deposition processes result in uneven deposition across the substrate. This uneven deposition is on a much larger scale and thickness than the small scale-topography, e.g., thicknesses of up to 1 μm across regions, often annular regions that are 5 to 40 mm wide. Many chemical mechanical polishing systems include components that can vary the polishing rate across the substrate, e.g., a carrier head with multiple individually pressurizable chambers, to compensate for non-uniform polishing effects or non-uniform layer thickness on the incoming substate. However, the uneven deposition resulting from an upstream process may strain or exceed the compensating capability of the polishing system.

To address this problem, a substrate can be treated after the deposition process, but before the next polishing process, to modify the thickness profiles of the substrate. In particular, the substrate can be subjected to a fluid jet ejected from a high-speed nozzle, e.g., a hydroblasting process. In contrast to an etchant treatment, hydroblasting is primarily a mechanical removal process.

FIG. 1 is a schematic cross-sectional view of a substrate 10 after a deposition process. The substrate 10 includes a semiconductor wafer 12, one or more intermediate layers 14, and an outermost layer 16 having an exposed surface 18. The one or more intermediate layers 14 can include one or more patterned layers. In this case, the outermost layer 16 can have small-scale topography resulting from the outermost layer 16 filling holes or trenches. However, this small-scale topography is not illustrated in FIGS. 1-5.

In addition to any small-scale topography, non-uniformity in the deposition process can result in a non-uniform thickness profile of the outermost layer 16. For example, the outermost layer 16 can have a relatively thick region 20 that is thicker relative to other regions 22 of the outermost layer 16. The thick region 20 can be near the edge of the substrate, e.g., within 1-5 cm of the substrate edge. As deposition processes are typically more uniform near the center of the substrate, a central portion 22 of the outermost layer 16 on the substrate 10 can have relatively uniform thickness.

To address this non-uniformity, as shown in FIG. 2 the relatively thicker region 20 can be subjected to a hydroblasting treatment in which a fluid 50, e.g., deionized water, is ejected from a nozzle 52 at high speed (shown by arrow A). The nozzle 52 can move laterally (shown by arrow B) in order to scan the jet of fluid 50 across the relatively thicker region 20. In contrast, the thinner region(s) 22 of relatively uniform thickness are not treated by hydroblasting.

In order to determine which regions of the surface 18 of the outermost layer 16 of substrate 10 should be subject to treatment, the substrate can be transferred to a metrology station after deposition but before treatment. The metrology station can be a stand-alone metrology system. The metrology station can generate a thickness profile, e.g. thickness of the outermost layer 16 as a function of radial position, or as a two-dimensional map, e.g., an R⊖ or XY map. This measured thickness profile can be stored by a controller and compared to a desired thickness profile. Regions where the measured thickness profile are thicker than the desired thickness profile are identified as regions to be treated. In some implementations, only one substrate from a batch or cassette is measured; other substrates from that batch or cassette are assumed to have the same measured thickness profile.

Referring to FIG. 3, following the hydroblasting treatment the thickness difference between the relatively thicker region 20′ and the thinner region 22 is significantly reduced. For example, the thickness difference can be less than 2%, e.g., less than 1%, of the total layer thickness. In particular, the thickness difference can be reduced to the point that variation of the polishing parameters in the chemical mechanical polishing process, e.g., the load applied to different regions on the substrate by different pressurizable chambers, can address the remaining non-uniformity.

FIG. 4 is a schematic cross-sectional view of a substrate 10 during a polishing process. The substrate 10 is held by a carrier head and the surface 18 of the outer layer 16 is pressed against a polishing pad 60. A polishing liquid 62, e.g., an abrasive slurry, is applied to the polishing pad 60, and relative motion (shown by arrow C) is generated between the polishing pad 60 and the substrate 10. For example, the polishing pad 60 can be located on a platen that rotates, and the carrier head can rotate to rotate the substrate 10, and optionally, the carrier head and substrate can sweep laterally across the polishing pad 60.

The polishing system can include an in-situ monitoring system that generates a signal that depends on the thickness of the outermost layer 16. A controller in the polishing system thus can receive this thickness data and control the polishing parameters, e.g., pressurized in chambers in the carrier head, to provide polishing rates that will result in a more uniform thickness after polishing.

Although FIG. 4 illustrates the substrate 10 in a face-up orientation, this is for consistency with FIGS. 1-3; in practice the substrate 10 would typically be polished in a face-down orientation.

Referring to FIG. 5, as a result of the polishing process, the thickness of the outermost layer 16 of the substrate 10 is reduced, e.g., to a predetermined thickness, or until an underlying layer is exposed. This underlying layer would be one of the one or more intermediate layers 14 is exposed. Due to the prior hydroblasting treatment, the outermost layer 16 can have substantially uniform thickness, e.g., non-uniformity of less than 3%, e.g., at 1-2%. Moreover, the substrate can have more uniform thickness near the substrate edge, which can improve bonding integration and edge die performance.

FIG. 6 is cross-sectional side view of a hydroblasting treatment station 100, e.g., to perform the treatment shown in FIG. 2. The hydroblasting treatment station 100 includes a chuck 110 to hold the substrate 10, and a dispenser 130 to deliver the fluid 50 at high speed onto the surface 18 of the substrate 10.

The chuck 110 has a top surface 112 to contact the back side of the substrate 10. In some implementations, the chuck 110 is rotatable, e.g., by drive shaft 114 that is driven by a motor 116. Although FIG. 6 illustrates the chuck 110 as narrower (horizontally) than the substrate 10, the chuck 110 could be wider than the substrate. A plurality of passages 120 can be formed through the chuck 110 with openings in the top surface 112. The passages 120 can be connected to a vacuum source 122, e.g., through a rotary fluid connection and any necessary piping, flexible tubing, etc., to apply a vacuum to chuck the substrate 10 to the chuck 110.

An annular shield 128 can surround the chuck 110, e.g., be concentric with the chuck 110, to block treatment fluid 50 flung off the substrate and thus prevent contamination of other portions of the system. The shield 128 can also serve as a catch-bowl to collect treatment fluid 50 that flows off the substrate 10.

To transfer the substrate 10 onto the chuck 110, an end effector of a robot can carry the substrate 10 into position over the chuck. After the substrate is lowered on the chuck 110, a treatment fluid 50, e.g., deionized water, is ejected from a nozzle 52 at high speed (shown by arrow A). In some implementations, lift pins 126 embedded in the chuck 110 can rise up from the chuck 110 to temporarily support the substrate 10. When the lift pins 126 are supporting the substrate 10, the robot can withdraw the end effector. Then the lift pins 126 can retract back into the chuck 110 until the substrate 10 is in contact with the top surface 112 of the chuck 110.

Alternatively, if the chuck 110 is narrower than the substrate 10 and the end effector is an edge grip or edge support ring, then transfer of the substrate 10 can be accomplished simply by raising the chuck 110 with a vertical actuator, e.g., the motor 116, until the chuck 110 contacts the substrate. The chuck 110 can be raised so that its top surface 112 is above the top edge 129 of the shield 128.

Alternatively, if the gap between the chuck 110 and shield 128 is sufficiently wide and the end effector is an edge grip or edge support ring, then transfer of the substrate 10 can be accomplished simply by lowering the end effector.

The dispenser 130 can include a nozzle 52 at the end of an arm 132 that extends from a base support 134. In some implementations, the arm 132 is pivotable, e.g., by rotation of a portion of the base support 134, such that the nozzle 52 can swing in an arc (shown by arrow D) so as to control the radial position of the nozzle 52 relative to the center of the substrate 10, e.g., relative to the axis of rotation of the chuck 110. In conjunction, rotation of the chuck 110 and sweep of the arm can provide motion of the nozzle (arrow B in FIG. 2) to position the nozzle 52 at any desired position on the surface of the substrate 19.

Of course, many other combinations are possible for positioning of the nozzle 52. For example, the arm 132 could be linearly extendable rather than pivotable. The base support 134 could be movable, e.g., in a direction to orthogonal to the linear motion of the arm 132, to provide X-Y positioning of the nozzle 52 over the substrate 10. In this case, rotation of the chuck 110 is not needed and is optional.

The nozzle 52 is fluidically coupled by a fluid line 136, e.g., by pipes, flexible tubing, passages through the arm 132, etc., to a treatment fluid source 138. The fluid source 138 can be a reservoir of temperature-controlled fluid, a facilities line, etc. A pump or valve 140 can control the flow rate of the treatment fluid 50 from the fluid source 136 to the nozzle.

The treatment fluid 50 can be deionized water (DI water). In particular, unlike slurry-based polishing operations the treatment fluid 136 can be abrasive-free. Moreover, the treatment fluid 50 need not include any etchant. The treatment fluid 50 can include a pH adjustor and/or an accelerant. In some implementations the treatment fluid can be include abrasive particles, e.g., be a slurry.

In operation, the pump or valve 140 can direct fluid 50 through the nozzle 52 at a rate such that the stream of fluid 50 is ejected at about 5-20 m/s, e.g., 10 m/s, onto the surface 18 of the outermost layer 16 of the substrate 10. This speed should be sufficient to create a hydroblasting effect that removes material from the substrate. Too high a velocity may create the risk of over-removal or damage to the substrate. Too low a velocity may simply not act to remove material. The size of the nozzle opening and spacing between the nozzle and substrate can be selected such that the treatment fluid 50 impinges the substrate in an area 0.5 to 20 mm across.

Although FIGS. 6-7 illustrate the substate 10 in a face-up position for the hydroblasting treatment, this is not necessary. For example, referring to FIG. 8, the substrate 10 could be held in a face-down position such that the treatment fluid 50 is ejected upwards from the nozzle 52. In some situations this may be a superior configuration, as the treatment fluid 50 will naturally fall off the surface of the substrate 10.

Returning to FIGS. 6-7, the hydroblasting treatment station 100 can include a controller 190 coupled to various components of the station, e.g., the motor 116 to control rotation and/or vertical position of the chuck 110, the motor(s) to control the position of the arm 132 and nozzle 52, and the pump or valve 140 to control the flow rate of the treatment fluid onto the substrate 10. Thus, the controller 190 is configured to cause the system to perform the hydroblasting treatment operation.

The controller 190 can store a desired thickness profile, e.g. a desired thickness of the outermost layer as a function of radial position, or as a two-dimensional map, e.g., an R⊖ or XY map. The desired thickness profile can be received from user input, from an uploaded file, or generated algorithmically. The controller 190 can also receive a measured thickness profile, e.g., from a stand-alone metrology station that measures the substrate after deposition of the outermost layer 16. The controller 190 can compare the measured thickness profile to the desired thickness profile to identify regions where the measured thickness profile are thicker than the desired thickness profile. Based on this identification, the controller 190 can generate a scan and flow plan, e.g., a set of motions for the chuck 110 and/or arm 132, as well as a flow rate for the treatment liquid as the nozzle 52 moves relative to the substrate, so as to treat the identified regions and reduce the difference between the measured thickness profile and the desired thickness profile.

In some implementations, the controller 190 stores data, e.g., in the form of a lookup table, that contains information about the rate of removal of the outermost layer 16 as a function of flow rate of the treatment fluid 50. The data can be empirically determined for each type of substrate, e.g., can depend on the composition of the outermost layer 18 and the pattern on the substate 10.

The hydroblasting treatment station 100 can also include an in-situ monitoring system 180 that provides a measurement of the thickness of the outermost layer 116 during treatment process. Examples of the monitoring system 180 include eddy current sensors, or optical monitors such as reflectometer or spectrometer. For example, the monitoring system 180 can include a light source 182 to generate a light beam 184 that is reflected off the surface 18 of the outermost layer 18 of the substrate, and a detector 186, e.g., a photodetector, to detect an intensity of the reflected light. The monitoring system 180 can be positioned to monitor a region at the same radial position on the substrate as the nozzle 52 is treating. For example, the optical monitoring system 180 could be attached to the same arm 132 that holds the nozzle 52, or the optical monitoring system 180 could be attached to a separate arm that extends over the chuck and controller 190 can cause the separate arm to position the monitoring region at the same radial distance from the center of the substrate as the nozzle 52. The monitoring system 180 can communicate with the controller 190 to provide feedback to and control the treatment process.

As used in the instant specification, the term substrate can include, for example, a product substrate (e.g., which includes multiple memory or processor dies), a test substrate, a bare substrate, and a gating substrate. The substrate can be at various stages of integrated circuit fabrication.

The controller and other computing devices part of systems described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware. For example, the controller can include a processor to execute a computer program as stored in a computer program product, e.g., in a non-transitory machine-readable storage medium. Such a computer program (also known as a program, software, software application, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

5 In context of the controller, “configured” indicates that the controller has the necessary hardware, firmware or software or combination to perform the desired function when in operation (as opposed to simply being programmable to perform the desire function).

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the description. Accordingly, other implementations are within the scope of the following claims.

Claims

1. A method comprising: after deposition of an outer layer on a substrate and before polishing of an exposed surface of the outer layer of the substrate, performing a hydroblasting treatment of a selected portion of the exposed surface by directing a treatment liquid from a nozzle at a sufficiently high velocity onto the selected portion to remove material from the selected portion such that a thickness non-uniformity of the outer layer is reduced; andchemical mechanical polishing the outer layer of the treated substrate to planarize and reduce a thickness of the outer layer.

2. The method of claim 1, comprising depositing the outer layer at a deposition station, and transferring the substrate to a hydroblasting treatment station for the hydroblasting treatment.

3. The method of claim 1, comprising holding the substrate on a chuck during the hydroblasting treatment.

4. The method of claim 3, comprising holding the substrate in a face-up orientation during the hydroblasting treatment.

5. The method of claim 3, comprising holding the substrate in a face-down orientation during the hydroblasting treatment.

6. The method of claim 3, comprising vacuum chucking the substrate to a chuck.

7. The method of claim 3, comprising rotating the chuck and sweeping the nozzle radially across the substrate to position the nozzle over the selected portion.

8. The method of claim 1, wherein the treatment fluid comprises deionized (DI) water.

9. The method of claim 8, wherein the treatment fluid is free of abrasives and/or etchants.

10. The method of claim 1, wherein the selected portion is annular.

11. The method of claim 10, wherein the selected portion has a radial width of about 5 to 40 mm.

12. The method of claim 1, comprising flowing the treatment fluid at a velocity of 5-20 m/s onto the exposed surface of the substate.

13. The method of claim 1, comprising receiving a measured thickness profile of the outer layer from a metrology station, storing a desired thickness profile, and comparing the measured thickness profile to the desired thickness profile to determine the selected portion of the surface.

14. A hydroblasting treatment station for modification of a substrate undergoing integrated circuit fabrication, the station comprising: a chuck to hold the substrate;a nozzle coupled to a source of treatment liquid, the nozzle laterally movable relative to the substrate; anda controller configured to cause the nozzle to direct the treatment liquid at a sufficiently high velocity onto the selected portion to remove material from the selected portion such that a thickness non-uniformity of an outer layer of the substrate is reduced.

15. The hydroblasting treatment station of claim 14, comprising a shield to catch treatment fluid flung or dropping from the substrate.

16. The hydroblasting treatment station of claim 14, comprising a plurality of passages through the chuck that are coupled to a vacuum source to vacuum chuck the substrate to the chuck.

17. The hydroblasting treatment station of claim 14, wherein the controller is configured to receive a measured thickness profile of the outer layer from a metrology station, store a desired thickness profile, and compare the measured thickness profile to the desired thickness profile to determine the selected portion of the surface.

18. The hydroblasting treatment station of claim 14, comprising a pump or valve to control a flow rate of treatment liquid from the source to the nozzle.

19. The hydroblasting treatment station of claim 18, wherein the controller is configured to control the pump or valve such that the treatment liquid is ejected at a velocity of 5-20 m/s onto the exposed surface of the substate.

20. The hydroblasting treatment station of claim 14, wherein the chuck is rotatable.

21. The hydroblasting treatment station of claim 20, wherein the nozzle is suspended from a pivotable arm.