JP7734644B2 - Semiconductor manufacturing apparatus and semiconductor device manufacturing method - Google Patents

Description

This disclosure relates to semiconductor manufacturing equipment and methods for manufacturing semiconductor devices.

Conventionally, the method of controlling the temperature by circulating cooling water inside the chuck stage during the laser annealing process, which is part of the semiconductor device manufacturing process, indirectly cools the semiconductor wafer placed on the wafer mounting surface of the chuck stage. Because the cooling capacity for the semiconductor wafer is insufficient, the heat from the laser beam causes the temperature of the semiconductor wafer to rise, and the protective film on the semiconductor wafer in contact with the wafer mounting surface of the chuck stage melts due to the heat. Because the melted protective film acts as an adhesive, there is a problem in that the semiconductor wafer sticks to the chuck stage during the semiconductor wafer ejection process, causing cracks or breakage in the semiconductor wafer.

To solve this problem, a method of cooling semiconductor wafers using gas has been proposed (see, for example, Patent Document 1).

JP 2011-086677 A

However, conventional equipment is designed so that gas is blown perpendicular to the direction from the bottom to the top of the semiconductor wafer, which means that the semiconductor wafer cannot be cooled sufficiently and efficiently. During the laser annealing process, the chuck stage becomes very hot due to the heat of the laser beam, and the protective film in contact with the wafer-mounting surface of the chuck stage can melt due to the heat. As a result, during the semiconductor wafer removal process, the semiconductor wafer tends to stick to the chuck stage, causing cracks or breaks to occur in the semiconductor wafer.

The present disclosure therefore aims to provide technology that can prevent cracks and breakage from occurring in semiconductor wafers during the semiconductor wafer discharge process.

The semiconductor manufacturing apparatus according to the present disclosure includes a wafer mounting surface on which a semiconductor wafer is mounted, the semiconductor wafer having a first main surface and a second main surface opposite the first main surface and a protective film formed on the second main surface, and a chuck stage having a plurality of grooves formed on the wafer mounting surface; and a control unit connected to the chuck stage for controlling the flow rate of the refrigerant gas so that the refrigerant gas is blown onto the semiconductor wafer from an air supply port formed in each of the grooves and the refrigerant gas circulated along each of the grooves is sucked through an outlet port formed in each of the grooves and discharged from each of the grooves. Each of the grooves is provided with a plurality of pairs of air supply ports for blowing the refrigerant gas in a first direction that is obliquely inclined with respect to the direction from the second main surface to the first main surface, and an outlet port for sucking the refrigerant gas in a second direction that is obliquely inclined with respect to the direction from the second main surface to the first main surface and intersects with the first direction, and discharging the refrigerant gas from each of the grooves.

According to the present disclosure, semiconductor wafers can be cooled sufficiently and efficiently, preventing the protective film on the semiconductor wafer from dissolving. This prevents the semiconductor wafer from sticking to the chuck stage during the semiconductor wafer ejection process, thereby preventing cracks and breakage from occurring in the semiconductor wafer.

2 is a cross-sectional view of a chuck stage and a cooling temperature regulator included in the semiconductor manufacturing apparatus according to the embodiment. FIG. 1 is a top view of a semiconductor manufacturing apparatus according to an embodiment; 1 is a cross-sectional view of a semiconductor manufacturing apparatus according to an embodiment. 5 is an explanatory diagram for explaining the flow of refrigerant gas around a semiconductor wafer in an embodiment. FIG. FIG. 10 is a top view of a semiconductor manufacturing apparatus according to a first modified example of the embodiment. FIG. 10 is a top view of a semiconductor manufacturing apparatus according to a second modified example of the embodiment. 10 is an explanatory diagram for explaining the flow of refrigerant gas around a semiconductor wafer in a second modification of the embodiment. FIG. FIG. 11 is a top view of a semiconductor manufacturing apparatus according to a third modified example of the embodiment. FIG. 11 is a cross-sectional view of a chuck stage and a heat dissipation fin provided in a semiconductor manufacturing apparatus according to a third modified example of the embodiment.

<Embodiment>
An embodiment will be described below with reference to the drawings. Fig. 1 is a cross-sectional view of a chuck stage 10 and a cooling temperature regulator 50 provided in a semiconductor manufacturing apparatus according to the embodiment. Fig. 2 is a top view of the semiconductor manufacturing apparatus according to the embodiment. Fig. 3 is a cross-sectional view of the semiconductor manufacturing apparatus according to the embodiment. Note that Fig. 3 shows a state in which the chuck stage 10 and the cooling temperature regulator 50 of Fig. 1 are connected.

As shown in Figures 1, 2, and 3, the semiconductor manufacturing apparatus is a laser annealing apparatus that performs a laser annealing process, which is part of the manufacturing process for semiconductor devices. The semiconductor manufacturing apparatus includes a chuck stage 10 and a cooling temperature regulator 50.

The chuck stage 10 includes a wafer mounting surface 11 on which the semiconductor wafer 1 is placed, multiple grooves 12, an air supply path 13, an exhaust path 14, an adsorption air exhaust path 15, an air supply port 16, an exhaust port 17, an adsorption port 18, a refrigerant gas inlet 13a, a refrigerant gas outlet 14a, and an adsorption air outlet 15a.

First, we will explain the semiconductor wafer 1 mounted on the chuck stage 10. The semiconductor wafer 1 has a first main surface 1a and a second main surface 1b opposite the first main surface 1a. A semiconductor functional layer, such as a semiconductor element (not shown), is formed on the second main surface 1b of the semiconductor wafer 1. Before the laser annealing process, a protective film 2 is formed on the second main surface 1b of the semiconductor wafer 1. Here, in FIG. 1, the first main surface 1a is the upper surface of the semiconductor wafer 1, and the second main surface 1b is the lower surface of the semiconductor wafer 1.

The laser annealing process is a process that follows the implantation process in which impurities are implanted into the first main surface 1a of the semiconductor wafer 1. The semiconductor wafer 1 is then placed on the wafer mounting surface 11 of the chuck stage 10, and the impurities are activated by irradiating the first main surface 1a with a laser beam.

As shown in Figure 2, the chuck stage 10 is circular when viewed from the first main surface 1a of the semiconductor wafer 1 (i.e., when viewed from above). Also, as shown in Figures 1 and 3, the entire chuck stage 10 is formed in the shape of a short cylinder in both the vertical direction.

As shown in Figures 1, 2, and 3, multiple grooves 12 are provided on the wafer mounting surface 11. Here, the wafer mounting surface 11 is the upper surface of the chuck stage 10.

The multiple grooves 12 include ring-shaped grooves of different diameters that surround the center of the wafer mounting surface 11. Specifically, the multiple grooves 12 are composed of a circular groove 12 that includes the center of the wafer mounting surface 11 and four ring-shaped grooves 12 that surround this circular groove 12. The diameters of the four ring-shaped grooves 12 are longer for the grooves 12 located on the outer periphery of the wafer mounting surface 11 than for the grooves 12 located on the inner periphery. The number of grooves 12 is not limited to five, and is preferably changed to match the size of the semiconductor wafer 1.

Each groove 12 is provided with four pairs of air supply ports 16 and exhaust ports 17. Each pair of air supply ports 16 and exhaust ports 17 is arranged at equal intervals on a circle. Four suction ports 18 are provided between adjacent grooves 12 on the wafer mounting surface 11. The suction ports 18 are arranged at equal intervals on a circle. The number of pairs of air supply ports 16 and exhaust ports 17 may be an even or odd number, as long as the semiconductor wafer 1 can be cooled evenly. It is preferable to increase the number of pairs as the diameter of the semiconductor wafer 1 increases.

The air supply path 13, exhaust path 14, and suction air exhaust path 15 are provided inside the chuck stage 10. The air supply path 13 is provided to supply refrigerant gas from the cooling temperature regulator 50 to the second main surface 1b side of the semiconductor wafer 1. The air supply path 13 is connected to a refrigerant gas inlet 13a provided on the underside of the chuck stage 10 and air outlets 16 provided in each groove 12.

The exhaust path 14 is provided to exhaust the refrigerant gas circulated along each groove 12 from each groove 12 to the cooling temperature regulator 50. The exhaust path 14 is connected to a refrigerant gas outlet 14a provided on the underside of the chuck stage 10 and an exhaust port 17 provided in each groove 12.

The suction air exhaust path 15 is provided to exhaust air present between the protective film 2 formed on the second main surface 1b of the semiconductor wafer 1 and the wafer mounting surface 11 through the suction port 18, thereby suctioning the second main surface 1b of the semiconductor wafer 1. The suction air exhaust path 15 is connected to the suction air outlet 15a provided on the underside of the chuck stage 10 and the suction port 18 provided between adjacent grooves 12 on the wafer mounting surface 11.

As shown in FIG. 3, the cooling temperature regulator 50 is connected to the chuck stage 10. Although not shown, the outlet of the cooling temperature regulator 50 is connected to the refrigerant gas inlet 13a of the chuck stage 10, and the inlet of the cooling temperature regulator 50 is connected to the refrigerant gas outlet 14a of the chuck stage 10. The suction air outlet 15a of the chuck stage 10 is connected to a vacuum pump, not shown.

In addition to regulating the temperature of the refrigerant gas, the cooling temperature regulator 50 is a control device that controls the flow rate of the refrigerant gas so that the internal pressure of the chuck stage 10 is lower than the external pressure, in order to blow the refrigerant gas onto the semiconductor wafer 1 through the air outlets 16 provided in each groove 12 and suck the refrigerant gas circulating along each groove 12 through the outlets 17 provided in each groove 12 and discharge it from each groove 12. Here, the internal pressure is the product of the gas pressure of the refrigerant gas supplied to the multiple grooves 12 and the area of the semiconductor wafer 1 in contact with the refrigerant gas. The external pressure is the product of atmospheric pressure and the area of the chuck stage 10 in contact with the semiconductor wafer 1.

The semiconductor wafer 1 is placed on the wafer mounting surface 11 of the chuck stage 10 so that the protective film 2 formed on the second main surface 1b of the semiconductor wafer 1 is in contact with the wafer mounting surface 11. The placed semiconductor wafer 1 is adsorbed to the wafer mounting surface 11 by suction through the suction ports 18.

Meanwhile, the first main surface 1a of the semiconductor wafer 1 is heat-treated by laser scanning during the laser annealing step. The temperature of the semiconductor wafer 1 rises as a result of the laser scanning, but the semiconductor wafer 1 is cooled by a refrigerant gas supplied from a cooling temperature regulator 50 passing through a refrigerant gas inlet 13a and an air flow path 13 and then blown onto the semiconductor wafer 1 from an air outlet 16. The refrigerant gas may be any gas capable of cooling the semiconductor wafer 1, and may be, for example, an inert gas such as _N2 gas or Ar.

The refrigerant gas blown onto the semiconductor wafer 1 circulates along each groove 12, is sucked through the exhaust port 17, and is discharged to the cooling temperature regulator 50 through the exhaust path 14 and the refrigerant gas outlet 14a. The refrigerant gas discharged to the cooling temperature regulator 50 is temperature-regulated within the cooling temperature regulator 50 before being supplied to the chuck stage 10.

Next, the flow of refrigerant gas around the semiconductor wafer 1 will be explained using Figures 2 and 4. Figure 4 is an explanatory diagram for explaining the flow of refrigerant gas around the semiconductor wafer 1 in this embodiment.

As shown in FIG. 4, the air outlet 16 faces a first direction so that it can blow refrigerant gas in the first direction, which is a direction obliquely inclined with respect to the direction from the second main surface 1b to the first main surface 1a. The exhaust outlet 17 faces a second direction so that it can draw in refrigerant gas from a second direction, which is a direction obliquely inclined with respect to the direction from the second main surface 1b to the first main surface 1a and intersects with the first direction, and exhaust the refrigerant gas from each groove 12. Here, the first direction is the direction of the arrow on the left in FIG. 4, and the second direction is the direction of the arrow on the right in FIG. 4.

As shown in Figures 2 and 4, the refrigerant gas is blown directly onto the protective film 2 of the semiconductor wafer 1 from the first direction and circulates along each groove 12. The refrigerant gas circulates along each groove 12 and is discharged from the outlet 17 in the second direction. In this way, the air outlet 16 blows the refrigerant gas in the first direction, and the outlet 17 discharges the refrigerant gas in the second direction. This allows the refrigerant gas to be blown onto the semiconductor wafer 1 more efficiently than when the refrigerant gas is blown perpendicular to the direction from the second main surface 1b to the first main surface 1a.

Due to the effect of the refrigerant gas blown from the first direction, which is oblique to the direction from the second main surface 1b to the first main surface 1a, the semiconductor wafer 1 can be cooled more sufficiently and efficiently than when the refrigerant gas is blown perpendicular to the direction from the second main surface 1b to the first main surface 1a. This allows the semiconductor wafer 1 to be efficiently adjusted to the desired temperature and improves the productivity of semiconductor devices with a simple structure. Furthermore, by increasing the air velocity of the refrigerant gas, the semiconductor wafer 1 can be cooled even more efficiently. In particular, the ring-shaped groove 12 makes it possible to further efficiently increase the air velocity when blowing the refrigerant gas.

<Modification of the embodiment>
Next, a modification of the embodiment will be described below: Fig. 5 is a top view of a semiconductor manufacturing apparatus according to a first modification of the embodiment.

As shown in FIG. 5, the multiple grooves 12 may be formed linearly, with multiple sets of air supply ports 16 and exhaust ports 17 provided in each groove 12. In order to evenly cool the semiconductor wafer 1, the air supply ports 16 and exhaust ports 17 in each groove 12 are preferably provided at the outer periphery and center of the wafer mounting surface 11. Furthermore, by scanning the laser beam in the same direction as the linear grooves 12, the semiconductor wafer 1 can be cooled more sufficiently and efficiently than by scanning in a direction different from the grooves 12.

When the laser beam is scanned from left to right in FIG. 5, the air supply port 16 and the exhaust port 17 are positioned so that the refrigerant gas also flows from left to right. On the other hand, when the laser beam is scanned from right to left in FIG. 5, the air supply port 16 and the exhaust port 17 are positioned so that the refrigerant gas also flows from right to left, thereby enabling the semiconductor wafer 1 to be cooled more efficiently.

Figure 6 is a top view of a semiconductor manufacturing apparatus according to a second variation of the embodiment. Figure 7 is an explanatory diagram illustrating the flow of refrigerant gas around a semiconductor wafer 1 in the second variation of the embodiment.

As shown in Figures 6 and 7, a temperature sensor 20 for detecting the temperature of the semiconductor wafer 1 may be provided between the air outlet 16 and the exhaust outlet 17 in each groove 12. In this case, the cooling temperature regulator 50 controls the flow rate of the refrigerant gas based on the detection results of the temperature sensor 20 so that the semiconductor wafer 1 reaches a set temperature. This makes it possible to control the flow rate of the refrigerant gas to an optimum level in accordance with the temperature of the semiconductor wafer 1.

Figure 8 is a top view of a semiconductor manufacturing apparatus according to a third variation of the embodiment. Figure 9 is a cross-sectional view of the chuck stage 10 and heat dissipation fins 21 provided in the semiconductor manufacturing apparatus according to the third variation of the embodiment.

As shown in Figures 8 and 9, multiple heat dissipation fins 21 may be provided on the outer surface of the chuck stage 10 to more evenly cool the semiconductor wafer 1. In particular, the chuck stage 10 has a circular shape when viewed from above, and by providing heat dissipation fins 21 extending from the center of the chuck stage 10 toward the outer periphery at equal intervals along the outer surface of the chuck stage 10, the semiconductor wafer 1 can be cooled more evenly.

In addition, although not shown, the wafer mounting surface 11 may be coated with a DLC (Diamond Like Carbon) film. This reduces the frictional resistance of the wafer mounting surface 11, and therefore prevents the semiconductor wafer 1 from sticking to the wafer mounting surface 11 of the chuck stage 10 during the semiconductor wafer 1 ejection process, even if the protective film 2 of the semiconductor wafer 1 in contact with the wafer mounting surface 11 is thermally melted. In Figure 8, the temperature sensor 20 does not need to be provided.

It is also possible to combine multiple of the above variations.

<Effects>
As described above, the semiconductor manufacturing apparatus according to the embodiment and its variants 1 to 3 includes a wafer mounting surface 11 on which a semiconductor wafer 1 is placed, the semiconductor wafer 1 having a first main surface 1a and a second main surface 1b opposite the first main surface 1a and having a protective film 2 formed on the second main surface 1b, and a chuck stage 10 having a plurality of grooves 12 formed in the wafer mounting surface 11; and a cooling temperature regulator 50 connected to the chuck stage 10, which blows refrigerant gas onto the semiconductor wafer 1 from air outlets 16 formed in each groove 12, and controls the flow rate of refrigerant gas so that the refrigerant gas circulated along each groove 12 is sucked in through outlets 17 formed in each groove 12 and discharged from each groove 12. Each groove 12 is provided with multiple sets of air outlets 16 that blow refrigerant gas in a first direction, which is a direction that is obliquely inclined with respect to the direction from the second main surface 1b to the first main surface 1a, and exhaust outlets 17 that suck in refrigerant gas from each groove 12 in a second direction that is a direction that is obliquely inclined with respect to the direction from the second main surface 1b to the first main surface 1a and a direction that intersects with the first direction.

The semiconductor device manufacturing method according to the embodiment and its variations 1 to 3 also includes an implantation step of implanting impurities into the first main surface 1a of the semiconductor wafer 1, and a laser annealing step of placing the semiconductor wafer 1 on the wafer mounting surface 11 of the chuck stage 10 and activating the impurities by irradiating the first main surface 1a with a laser beam. During the laser annealing step, a refrigerant gas circulates along the multiple grooves 12.

As a result, the semiconductor wafer 1 can be cooled sufficiently and efficiently, preventing the protective film 2 on the semiconductor wafer 1 from dissolving. This prevents the semiconductor wafer 1 from sticking to the chuck stage 10 during the semiconductor wafer 1 ejection process, thereby preventing cracks and breakage from occurring in the semiconductor wafer 1. As a result, the yield of semiconductor wafers 1 is improved, and the yield of semiconductor devices is also improved.

In addition, the multiple grooves 12 include ring-shaped grooves of different diameters that surround the center of the wafer mounting surface 11, allowing the refrigerant gas to circulate in a ring-shaped manner through the multiple grooves 12 to match the shape of the semiconductor wafer 1. This allows the semiconductor wafer 1 to be cooled even more efficiently. Furthermore, because the grooves 12 are formed in a ring shape, the wind speed when blowing the refrigerant gas can be increased even more efficiently.

The semiconductor manufacturing equipment also includes a temperature sensor 20 located between the air outlet 16 and the exhaust outlet 17 in each groove 12 to detect the temperature of the semiconductor wafer 1. The cooling temperature regulator 50 controls the flow rate of the refrigerant gas based on the detection results of the temperature sensor 20 so that the semiconductor wafer 1 reaches a set temperature. Therefore, the refrigerant gas can be controlled to an optimal flow rate in accordance with the temperature of the semiconductor wafer 1, further enhancing the cooling effect of the semiconductor wafer 1.

In addition, because the wafer mounting surface 11 is coated with a DLC film, the frictional resistance of the wafer mounting surface 11 is reduced. Therefore, even if the protective film 2 of the semiconductor wafer 1 in contact with the wafer mounting surface 11 is thermally melted, the semiconductor wafer 1 can be prevented from sticking to the wafer mounting surface 11 of the chuck stage 10 during the semiconductor wafer 1 ejection process.

The chuck stage 10 is formed in a circular shape when viewed from the first main surface 1a of the semiconductor wafer 1, and heat dissipation fins 21 are provided on the outer surface of the chuck stage 10. Therefore, by adding the cooling effect of the heat dissipation fins 21 to the cooling effect of the semiconductor wafer 1 provided by the chuck stage 10, the cooling effect of the semiconductor wafer 1 can be further enhanced.

In addition, because the refrigerant gas is an inert gas, its ozone depletion potential and global warming potential are both zero, making the product environmentally friendly and reducing its environmental impact.

The embodiment can be modified as appropriate.

The various aspects of this disclosure are summarized below as appendices.

(Appendix 1)
a chuck stage including a wafer mounting surface on which a semiconductor wafer is mounted, the semiconductor wafer having a first main surface and a second main surface opposite to the first main surface and a protective film formed on the second main surface, the wafer mounting surface having a plurality of grooves;
a control unit connected to the chuck stage and configured to control the flow rate of the refrigerant gas so that the refrigerant gas is blown onto the semiconductor wafer from an air outlet provided in each of the grooves, and the refrigerant gas circulated along each of the grooves is sucked in through an outlet provided in each of the grooves and discharged from each of the grooves;
each groove is provided with a plurality of sets of blower ports that blow the refrigerant gas in a first direction that is obliquely inclined with respect to the direction from the second main surface to the first main surface, and exhaust ports that suck the refrigerant gas from each groove in a second direction that is obliquely inclined with respect to the direction from the second main surface to the first main surface and intersects with the first direction.

(Appendix 2)
2. The semiconductor manufacturing apparatus according to claim 1, wherein the plurality of grooves include ring-shaped grooves of different diameters that surround the center of the wafer mounting surface.

(Appendix 3)
a temperature sensor provided in each of the grooves between the air outlet and the exhaust port for detecting a temperature of the semiconductor wafer;
3. The semiconductor manufacturing apparatus according to claim 1, wherein the control unit controls the flow rate of the refrigerant gas based on the detection result of the temperature sensor so that the semiconductor wafer reaches a set temperature.

(Appendix 4)
4. The semiconductor manufacturing apparatus according to claim 1, wherein the wafer mounting surface is coated with a DLC film.

(Appendix 5)
the chuck stage is formed in a circular shape when viewed from the first main surface side of the semiconductor wafer,
5. The semiconductor manufacturing apparatus according to claim 1, wherein a heat dissipation fin is provided on an outer surface of the chuck stage.

(Appendix 6)
6. The semiconductor manufacturing apparatus according to claim 1, wherein the refrigerant gas is an inert gas.

(Appendix 7)
A semiconductor manufacturing method using the semiconductor manufacturing apparatus according to any one of Supplementary Note 1 to Supplementary Note 6,
an implantation step of implanting impurities into the first main surface of the semiconductor wafer;
a laser annealing step of placing the semiconductor wafer on the wafer mounting surface of the chuck stage and activating the impurities by irradiating the first main surface with a laser beam,
The method for manufacturing a semiconductor device, wherein the refrigerant gas circulates along the plurality of grooves during the laser annealing step.

1 semiconductor wafer, 1a first main surface, 1b second main surface, 2 protective film, 10 chuck stage, 11 wafer mounting surface, 12 groove, 16 air outlet, 17 exhaust outlet, 20 temperature sensor, 21 heat dissipation fin, 50 cooling temperature controller.

Claims (7)

a chuck stage including a wafer mounting surface on which a semiconductor wafer is mounted, the semiconductor wafer having a first main surface and a second main surface opposite to the first main surface and a protective film formed on the second main surface, the wafer mounting surface having a plurality of grooves;
a control unit connected to the chuck stage and configured to control the flow rate of the refrigerant gas so that the refrigerant gas is blown onto the semiconductor wafer from an air outlet provided in each of the grooves, and the refrigerant gas circulated along each of the grooves is sucked in through an outlet provided in each of the grooves and discharged from each of the grooves;
each groove is provided with a plurality of sets of blower ports that blow the refrigerant gas in a first direction that is obliquely inclined with respect to the direction from the second main surface to the first main surface, and exhaust ports that suck the refrigerant gas from each groove in a second direction that is obliquely inclined with respect to the direction from the second main surface to the first main surface and intersects with the first direction. The semiconductor manufacturing apparatus of claim 1, wherein the plurality of grooves include rings of different diameters surrounding the center of the wafer mounting surface. a temperature sensor provided in each of the grooves between the air outlet and the exhaust port for detecting a temperature of the semiconductor wafer;
2. The semiconductor manufacturing apparatus according to claim 1, wherein the control unit controls the flow rate of the refrigerant gas based on the detection result of the temperature sensor so that the semiconductor wafer reaches a set temperature. The semiconductor manufacturing apparatus of claim 1, wherein the wafer mounting surface is coated with a DLC film. the chuck stage is formed in a circular shape when viewed from the first main surface side of the semiconductor wafer,
2. The semiconductor manufacturing apparatus according to claim 1, wherein the chuck stage is provided with heat dissipation fins on an outer surface thereof. The semiconductor manufacturing apparatus according to any one of claims 1 to 5, wherein the refrigerant gas is an inert gas. A semiconductor manufacturing method using the semiconductor manufacturing apparatus according to claim 1,
an implantation step of implanting impurities into the first main surface of the semiconductor wafer;
a laser annealing step of placing the semiconductor wafer on the wafer mounting surface of the chuck stage and activating the impurities by irradiating the first main surface with a laser beam,
The method for manufacturing a semiconductor device, wherein the refrigerant gas circulates along the plurality of grooves during the laser annealing step.