# US 7,745,762 B2 · Optimizing the thermal budget during a pulsed heating process

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- Number: US 7,745,762 B2
- Document ID: US7745762B2
- Status: Granted
- Kind: B2
- Application number: 11/443,464
- Filed: 2006-05-30
- Published: 2006-12-28
- Granted: 2010-06-29
- Earliest claimed: 2005-06-01
- Assignees: Mattson Technology, Inc.
- Inventors: Paul Janis Timans
- Web page: https://patentgrep.com/patent/US7745762B2

## CPC

- H10P 72/0436: {mainly by radiation}
- F27B 5/04: adapted for treating the charge in vacuum or special atmosphere
- F27B 17/0025: {specially adapted for treating semiconductor wafers}
- H10P 72/0434: {mainly by convection}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- F27B: FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS

## Abstract

An approach for optimizing the thermal budget during a pulsed heating process is disclosed. A heat sink or thermal transfer plate is configured and positioned near an object, such as a semiconductor wafer, undergoing thermal treatment. The heat sink is configured to enhance the thermal transfer rate from the object so that the object is rapidly brought down from the peak temperature after an energy pulse. High thermally-conductive material may be positioned between the plate and the object. The plate may include protrusions, ribs, holes, recesses, and other discontinuities to enhance heat transfer and avoid physical damage to the object during the thermal cycle. Additionally, the optical properties of the plate may be selected to allow for temperature measurements via energy measurements from the plate, or to provide for a different thermal response to the energy pulse. The plate may also allow for pre-heating or active cooling of the wafer.

## Claims

### Claim 1

A method of thermally treating an object, the method comprising:
providing an object in a thermal processing chamber;
positioning a thermal transfer plate in close thermal communication with the object, the thermal transfer plate having a thermal mass no greater than about three times the thermal mass of the object;
pre-heating the object; and
heating the object by directing at least one pulse of energy toward the object for a duration of less than 1 s such that the average temperature of the semiconductor wafer increases by a temperature difference ΔT to a peak temperature;
wherein the thermal transfer plate is configured and positioned such that the cooling rate from the object is enhanced such that the average temperature of the object is brought down from the peak temperature by at least 50% of the value of ΔT within 1.0 s.

### Claim 2 (depends on 1)

The method as set forth in claim 1, wherein the thermal transfer plate has a thermal mass no greater than the approximate thermal mass of the object.

### Claim 3 (depends on 1)

The method as set forth in claim 1, wherein heating the object includes scanning the surface of the object with a laser.

### Claim 4 (depends on 1)

The method as set forth in claim 1, wherein heating the object includes illuminating the object with at least one lamp.

### Claim 5 (depends on 1)

The method as set forth in claim 1, wherein the thermal transfer plate comprises at least one material selected from the following group: silicon, silicon carbide, silicon dioxide, silicon nitride, aluminium oxide, sapphire, quartz, aluminium nitride, boron nitride, aluminium oxynitride, graphite, carbon, diamond, yttrium aluminium garnet (YAG).

### Claim 6 (depends on 1)

The method as set forth in claim 1, wherein the thermal transfer plate is positioned such that the plate and a surface of the object are approximately parallel to one another and define a gap.

### Claim 7 (depends on 6)

The method as set forth in claim 6, wherein the gap distance is less than about 0.2 mm.

### Claim 8 (depends on 6)

The method as set forth in claim 6, further comprising: delivering a material into the gap to enhance thermal transfer between the object and the plate.

### Claim 9 (depends on 8)

The method as set forth in claim 8, wherein the material comprises a gas.

### Claim 10 (depends on 9)

The method as set forth in claim 9, wherein the gas has a thermal conductivity of at least 0.1 Wm-1K-1.

### Claim 11 (depends on 10)

The method as set forth in claim 10, wherein the gas comprises helium.

### Claim 12 (depends on 8)

The method as set forth in claim 8, wherein at least two different materials are delivered into the gap such that the degree of thermal coupling between the object and the thermal transfer plate differs during the thermal treatment process.

### Claim 13 (depends on 1)

The method as set forth in claim 1, wherein pre-heating the object comprises emitting heat from the thermal transfer plate.

### Claim 14 (depends on 1)

The method as set forth in claim 1, wherein the plate includes a plurality of holes smaller than about 2 mm in diameter.

### Claim 15 (depends on 1)

The method as set forth in claim 1, wherein the plate includes discontinuities in the plate surface, wherein the discontinuities are smaller in size than thermal diffusion length associated with the process.

### Claim 16 (depends on 15)

The method as set forth in claim 15, wherein at least one discontinuity is selected from the group consisting of: slits, ribs, recesses, protrusions, and holes.

### Claim 17 (depends on 1)

The method as set forth in claim 1, wherein the surface of the plate is textured to further enhance heat transfer between the plate and the object.

### Claim 18 (depends on 1)

The method as set forth in claim 1, wherein the interior of the plate comprises a material that undergoes a phase change at a selected temperature, the temperature selected to optimize heat transfer from the object.

### Claim 19 (depends on 1)

The method as set forth in claim 1, further comprising: actively augmenting the cooling rate of the object.

### Claim 20 (depends on 19)

The method as set forth in claim 19, wherein the cooling rate is augmented by directing a cooling gas toward the object.

### Claim 21 (depends on 20)

The method as set forth in claim 20, wherein the cooling rate is augmented by directing the cooling gas toward the thermal transfer plate.

### Claim 22 (depends on 19)

The method as set forth in claim 19, wherein the cooling rate is augmented by directing a cooling gas toward the thermal transfer plate.

### Claim 23 (depends on 1)

The method as set forth in claim 1, further comprising monitoring the temperature of the object.

### Claim 24 (depends on 23)

The method as set forth in claim 23, wherein the temperature of the object is monitored using at least one optical pyrometer.

### Claim 25 (depends on 1)

The method as set forth in claim 1, wherein the temperature of the object is determined based on measuring energy from the thermal transfer plate.

### Claim 26

A system for thermal treatment of an object within a chamber, comprising:
a heating arrangement configured to direct a pulse of energy towards a surface of an object; the pulse of energy configured to increase the average temperature of the object by a temperature difference ΔT between the average temperature of the wafer just prior to the pulse (T1) and the maximum average temperature of the wafer after the pulse has ceased (T2); and
a thermal transfer plate positioned parallel to a surface of the object, the thermal transfer plate having a thermal mass no greater than about three times the thermal mass of the object; the thermal transfer plate being positioned such that the average temperature of the wafer decreases from T2 by at least 50% of the value of ΔT within 1.0 s.

### Claim 27 (depends on 26)

The system as set forth in claim 26, wherein the thermal mass of the thermal transfer plate is no greater than the approximate thermal mass of the object.

### Claim 28 (depends on 26)

The system as set forth in claim 26, further comprising a heat source configured to deliver pre-heating energy to the object.

### Claim 29 (depends on 26)

The system as set forth in claim 26, wherein the thermal transfer plate comprises at least one material selected from the following group: silicon, silicon carbide, silicon dioxide, silicon nitride, aluminium oxide, sapphire, quartz, aluminium nitride, boron nitride, aluminium oxynitride, graphite, carbon, diamond, yttrium aluminium garnet (YAG).

### Claim 30 (depends on 26)

The system as set forth in claim 26, wherein the thermal transfer plate is spaced such that the thermal transfer plate and a surface of the object define a gap.

### Claim 31 (depends on 30)

The system as set forth in claim 30, wherein the gap distance is less than about 0.2 mm.

### Claim 32 (depends on 31)

The system as set forth in claim 31, wherein the gap is filled with a material selected to enhance the thermal transfer rate between the object and the thermal transfer plate.

### Claim 33 (depends on 32)

The system as set forth in claim 32, wherein the material comprises a gas.

### Claim 34 (depends on 33)

The system as set forth in claim 33, wherein the gas has a thermal conductivity of at least 0.1 Wm-1K-1.

### Claim 35 (depends on 34)

The system as set forth in claim 34, wherein the gas comprises helium.

### Claim 36 (depends on 26)

The system as set forth in claim 26, wherein the heating arrangement comprises an array of lamps.

### Claim 37 (depends on 26)

The system as set forth in claim 26, wherein the heating arrangement comprises a laser configured to scan the surface of the object.

### Claim 38 (depends on 26)

The system of claim 26, further comprising at least one temperature measurement device.

### Claim 39 (depends on 38)

The system as set forth in claim 38, wherein the temperature measurement device comprises a pyrometer.

### Claim 40 (depends on 38)

The system as set forth in claim 38, wherein the measurement device is configured to determine the temperature of the object based on measuring energy from the thermal transfer plate.

### Claim 41 (depends on 26)

The system as set forth in claim 26, wherein the thermal transfer plate is configured to selectively act as a heat source.

### Claim 42 (depends on 26)

The system as set forth in claim 26, wherein the thermal transfer plate includes a plurality of holes with diameters smaller than about 2 mm.

### Claim 43 (depends on 26)

The systems set forth in claim 26, wherein the thermal transfer plate includes a discontinuity selected from the group consisting of: slits, ribs, recesses, protrusions, and holes; and wherein the discontinuity is smaller than the thermal diffusion length associated with the thermal treatment process.

### Claim 44 (depends on 26)

The system as set forth in claim 26, wherein the thermal transfer plate comprises an interior and exterior, and at least a portion of the interior is configured to undergo a phase change at a selected temperature.

### Claim 45 (depends on 26)

The system as set forth in claim 26, wherein the surface of the thermal transfer plate is textured.

### Claim 46

A method of processing a semiconductor wafer, the method comprising:
placing a semiconductor wafer into a rapid thermal processing chamber;
pre-heating the semiconductor wafer to an average temperature T1;
after pre-heating, subjecting the semiconductor wafer to at least one pulse of energy for less than 1 s, such that the average temperature of the semiconductor wafer increases by a temperature difference ΔT between the average temperature of the wafer just prior to the pulse (T1) and the maximum average temperature of the wafer after the pulse has ceased (T2);
enhancing heat transfer from the wafer by placing a thermal transfer plate in close thermal communication with the wafer, the thermal transfer plate having a thermal mass no greater than about three times the thermal mass of the semiconductor wafer;
wherein the thermal transfer plate is configured and positioned such that the average temperature of the wafer decreases from T2 by at least 50% of the value of ΔT within 1.0 s.

### Claim 47 (depends on 46)

The method as set forth in claim 46, wherein T1 is at least about 600° C.

### Claim 48 (depends on 46)

The method as set forth in claim 46, wherein ΔT is at least 50° C.

### Claim 49 (depends on 46)

The method as set forth in claim 46, wherein the average temperature of the wafer decreases from T2 by at least 50% of the value of ΔT within 0.5 s.

### Claim 50 (depends on 49)

The method as set forth in claim 49, wherein the average temperature of the wafer decreases from T2 by at least 50% of the value of ΔT within 0.3 s.

### Claim 51

A system for thermal treatment of an object within a chamber, comprising:
a heating arrangement configured to direct a pulse of energy towards a surface of an object; and
a thermal transfer plate positioned parallel to a surface of the object, the thermal transfer plate having a thermal mass no greater than about three times the thermal mass of the object; and
at least one temperature measurement device.

### Claim 52 (depends on 51)

The system of claim 51, wherein the temperature measurement device comprises a pyrometer.

### Claim 53 (depends on 51)

The system of claim 51, wherein the measurement device is configured to determine the temperature of the object based on measuring energy from the transfer plate.

### Claim 54

A system for thermal treatment of an object within a chamber, comprising:
a heating arrangement configured to direct a pulse of energy towards a surface of an object; and
a thermal transfer plate positioned parallel to a surface of the object, the thermal transfer plate having a thermal mass no greater than about three times the thermal mass of the object;
wherein the thermal transfer plate includes a plurality of holes with diameters smaller than about 2 mm.

### Claim 55

A system for thermal treatment of an object within a chamber, comprising:
a heating arrangement configured to direct a pulse of energy towards a surface of an object; and
a thermal transfer plate positioned parallel to a surface of the object, the thermal transfer plate having a thermal mass no greater than about three times the thermal mass of the object;
wherein the thermal transfer plate includes a discontinuity selected from the group consisting of: slits, ribs, recesses, protrusions, and holes; and wherein the discontinuity is smaller than the thermal diffusion length associated with the thermal treatment process.

### Claim 56

A system for thermal treatment of an object within a chamber, comprising:
a heating arrangement configured to direct a pulse of energy towards a surface of an object; and
a thermal transfer plate positioned parallel to a surface of the object, the thermal transfer plate having a thermal mass no greater than about three times the thermal mass of the object;
wherein the surface of the thermal transfer plate is textured.