KR100426274B1 - Wafer Ashing Apparatus and Method using Lamp Heating - Google Patents

Abstract

The present invention relates to a semiconductor wafer ashing apparatus and method capable of quickly performing a two-stage ashing operation while preventing popping of the cured photoresist by providing a lamp heating unit. The present invention relates to a reaction chamber and an upper portion of the reaction chamber. A lamp heating unit having three to twelve lamps, a heating means under the reaction chamber, and three or more lift pins disposed above the heating means to support the wafer in two stages to adjust the distance between the wafer and the heating means. It characterized in that it comprises a lift pin that can be up or down (down).

According to the present invention, the time required for the ashing process of the wafer can be dramatically shortened by quickly removing the cured photoresist of the high energy implanted wafer without popping.

Description

Semiconductor Wafer Ashing Apparatus and Method Using Lamp Heating {Wafer Ashing Apparatus and Method using Lamp Heating}

The present invention provides a wafer ashing apparatus and method in a semiconductor manufacturing process, and more particularly, a lamp heating portion to quickly perform a two-step ashing operation while preventing popping of the cured photoresist. It relates to a wafer ashing apparatus and method that can be.

Photolithography, one of the semiconductor manufacturing processes, includes a step of coating a photoresist on a semiconductor substrate to form a photoresist layer, selectively exposing a photoresist layer, and a photoresist pattern. Developing the exposed photoresist layer to etch, etching the regions of the semiconductor substrate not covered by the photoresist, and removing the photoresist pattern used as a mask in the etching step. It consists of steps.

The first half of this photolithography process may be used to create a mask that can be used in an ion implantation process. That is, the resist pattern generated by the selective exposure can be used as a mask for the ion implantation process for introducing impurities into the surface region of the semiconductor.

An ashing process performed using a plasma containing O ₂ radicals or oxygen ions is a process of removing a resist pattern after completion of the ion implantation process.

A typical ashing process is performed by placing a wafer in a reaction chamber and injecting plasma (O ₂ gas injection and high energy electric field application) with the wafer temperature raised using a suitable heating device. Since the ashing rate in the ashing process is proportional to the temperature, the ashing process is preferably performed at a high temperature. That is, looking at the temperature characteristics of the photoresist, the active energy state is rapidly increased in proportion to the temperature from 80 ℃ to 300 ℃, after 300 ℃ the active energy is reduced.

On the other hand, in the ion implantation process, the physical properties of the upper layer of the photoresist pattern are chemically changed and hardened. The ashing process performed after the ion implantation process is performed at a high temperature as described above, and when the temperature is about 170 ° C. or more, a “popping” in which the cured photoresist layer is destroyed due to the expansion of vaporization material under the cured photoresist is performed. popping) "phenomenon. Such popping is undesirable because it contaminates the wafer surface and the inner surface of the ashing device and causes the productivity to decrease by rejecting the wafer to prolong the production cost and processing time.

Therefore, in order to prevent such popping, when ashing is performed in a low temperature state, time is consumed and the ashing efficiency is reduced as a whole.

On the other hand, a process that does not perform ion implantation using the photoresist as a direct mask may be performed, and in this case, since the hardening of the photoresist does not occur and there is no risk of popping, ashing is performed at a high temperature of 200 ° C. or more for a short time. Needs to be.

Accordingly, there is a need for an apparatus capable of ashing hard photoresist cured in the low temperature region and simultaneously ashing the remaining soft photoresist at high temperature.

Of course, in the conventional ashing apparatus, the temperature of the heating means, commonly called a heating chuck, may be changed to a low temperature while the hard photoresist is removed, to a high temperature while the remaining soft photoresist is removed, but the heating chuck is mainly heated. Because it is manufactured in the form of a coil (coil), it is difficult to use a sudden temperature change, and when the temperature change is severe, the heating chuck is easily damaged.

Various ashing devices are being developed according to this need, for example, US Patent No. 6,199,561.

1 shows an ashing apparatus according to the patent, which includes a reaction chamber 130 having an upper gas inlet 110 and a lower gas outlet 120, and a pair of discharge electrodes 150. It is arrange | positioned along this gas inlet. In addition, the wafer support 210 is disposed on the vertically movable support rod 180. The support rod 180 is moved up and down using a motor and gear means, not shown, so that the wafer stays at three selected levels A, B, and C for a predetermined time. In addition, an annular stage 190 having a heating means therein is disposed around the support rod 180.

In the ashing process using this equipment, the wafer is placed at the highest position A when loaded into the chamber, and placed at the intermediate position B during the first step (cold ashing operation) to remove the cured photoresist. It is located at the bottom C during the second step (hot ashing operation) for removing the remaining soft photoresist.

Specifically, in the ashing process, the wafer is inserted into the chamber when the wafer support is in the best position A, and the temperature is moved to the lower position B of about 120 ° C. for performing the first step. Then, after vacuuming the interior of the chamber, O ₂ gas is filled into the chamber and a high frequency electric field is generated between the electrodes. In this first step, the wafer is exposed to O radicals and O plasma at temperatures of about 120 ° C. and the cured photoresist is removed without popping.

After the cured photoresist is removed, the wafer support moves to the bottommost position C, which maintains a temperature of about 150 ° C. or more, and the ashing of the remaining second steps is performed. In the ashing operation at a high temperature, the throughput increases, so that the soft photoresist can be removed more quickly than in the first step. Therefore, the ashing operation of the wafer having the cured hard photoresist and the uncured soft photoresist at the same time can be performed quickly and safely without popping.

However, with such equipment, the pre-heating time for heating until the temperature of the intermediate position B where the first step occurs after the wafer is inserted into the chamber rises to about 120 ° C is relatively long, Since the first step by plasma application is performed during the temperature rise before reaching 120 ° C., the time taken for the first step for removing the hardened hard photoresist is relatively long. This disadvantage is described in more detail with reference to FIG. 5 in the following examples.

In fact, in such a configuration, the heat transfer rate is very low because there is almost a vacuum between the heating means and the wafer. Therefore, when the wafer is a few cm away from the coil-type heating means, it takes about 3 to 6 minutes to heat up to about 100 ° C., so that the time required for the entire ashing is very long.

The present invention focuses on this point, in order to increase the ashing throughput of the wafer and to prevent popping, by using a halogen lamp array as the heating device of the first step, the time required for the first step is shortened and the wafer is kept at a uniform temperature. This is to ensure good ashing by exposure to the distribution.

It is an object of the present invention to provide a photoresist ashing apparatus that can safely and quickly remove cured hard photoresist without popping.

Another object of the present invention is to provide a photoresist ashing method capable of improving ashing throughput.

It is still another object of the present invention to use a plurality of halogen lamp arrays having a specific shape in addition to the conventional heating apparatus, so that the wafer can be heated uniformly and quickly, thereby reducing the time required for ashing. To provide a device.

1 shows a configuration of a wafer ashing apparatus according to US Pat. No. 6,199,561.

2 is a cross-sectional view showing the overall configuration of a wafer ashing apparatus according to the present invention.

Figure 3a is a bottom view of the lamp housing of the lamp heating portion, Figure 3b is a front view and side view of the lamp used in the present invention, Figure 3c shows a reflector and two lamps installed below the reflector, Figure 3d is a lamp heating Bottom view of wealth.

4 is a step-by-step view of the wafer ashing process using the ashing apparatus according to the present invention.

5 is a graph showing the ashing time in the case of using the ashing apparatus and method according to the present invention in comparison with the conventional method.

Figure 6 shows the change of wafer during the ashing process according to the present invention.

* Description of the symbols for the main parts of the drawings *

1: reaction chamber 2: lift pin

3: heating chuck 5: gas inlet

6: wafer 10: lamp heating part

11: lamp 12: reflector

13 lamp housing 14 reflector mounting groove

15: Diaphragm 21: Hard Photoresist

22: soft photoresist

In order to achieve the above object, the photoresist ashing apparatus according to the present invention has the following configuration.

A lamp heating unit having a reaction chamber and an upper portion of the reaction chamber and having three to twelve lamps, a heating means below the reaction chamber, and three or more lift pins arranged above the heating means to support the wafer and the wafer. And a lift pin that can be up or down to adjust the spacing of the means in two steps.

The lamp housing may further include one or more reflecting plates for improving the reflectance of the lamp, wherein the distance between the wafer and the heating means when the lift pin is up is about 5 to 30 mm, wherein the wafer and The distance between the lamps is preferably about 50 to 250 mm. In addition, each lamp may be a round (horseshoe type), hemispherical, bulb-type, or c-shaped lamp having an output (power consumption) of 1 kW or less, but is preferably a 1-kW c-shaped halogen lamp.

In addition, the photoresist ashing method according to the present invention uses the above-described ashing apparatus, and includes the following steps.

The wafer is loaded on the lift pin in the state where the lift pin is up while the heating means is maintained at 200 ° C. or higher, and the chamber is sealed. Then, the vacuum pump for vacuuming the inside of the chamber is operated. A lamp heating step of heating the temperature of the wafer to 130 to 170 ° C. by turning on the lamp and maintaining it for 12 to 30 seconds;

A first ashing step of turning off the lamp after the lamp heating step and injecting plasma to maintain the cured hard photoresist while it is removed;

And a second ashing step of bringing the lift pin down while the heating means continues to operate above 200 ° C. and exposing it until the soft photoresist is removed.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

2 is a cross-sectional view showing the overall configuration of the ashing apparatus according to the present invention.

The ashing apparatus according to the present invention largely includes a reaction chamber 1, a lamp heating unit 10 disposed above the chamber, a heating chuck 3 as a heating apparatus, and a wafer lift pin 2. Doing.

In addition, like the conventional plasma ashing device, the ion gas inlet 5 and an outlet, a power supply device, a control device, and the like, may be provided.

The lamp heating unit 10 according to the present embodiment includes eight U-shaped halogen lamps 11, four reflecting plates 12 for improving the heating efficiency of the lamps, and a circular lamp housing for supporting the reflecting plates and the lamps. It consists of (13).

3A is a bottom view of the lamp housing 13, which is made of a metal frame having a diameter of about 35 cm, and has a reflector plate recess 14 into which four reflector plates 12 can be inserted.

FIG. 3B is a front view and a side view of a lamp used in this example, and a C-shaped halogen lamp having a length of about 75 mm, a height (distance from the end of the lamp to the socket part) of about 55 mm, and a thickness of about 10 mm is used. However, as described above, the shape and the filling gas are not necessarily limited, and a lamp having a shape such as a bulb type, a horseshoe type (round type), a hemispherical type or the like may be used.

3C shows a reflector and two lamps installed below the reflector.

The reflecting plate 12 is composed of a fan-shaped frame having a middle diaphragm 15, and two lamps 11 can be provided in one reflecting plate. The reflector is to increase the reflectivity of the lamp to increase the efficiency of heating, but may be coated with an aluminum film that reflects heat well, but is not limited thereto.

Each reflecting plate is fixed to the reflecting plate mounting groove of the lamp housing shown in Fig. 3A.

FIG. 3D is a bottom view of the lamp heating unit 10 in which four reflecting plates 12 and eight U-shaped halogen lamps 11 are provided in the lamp housing 13.

4 is a step-by-step view of the photoresist ashing process using the ashing apparatus according to the present invention.

4A shows a ramp heating step, in which the wafer 6 is loaded onto the lift pins while the lift pins 2 are up while maintaining the heating chuck 3 at 200 ° C. or higher (preferably around 250 ° C.). After the chamber 1 is sealed, the vacuum pump (not shown) is operated and eight halogen lamps 11 are turned on and held for 12 to 30 seconds. In this step, the wafer temperature is 130 to 170 ° C.

FIG. 4B shows a first ashing process for removing hard photoresist, in which the lamp is turned off after the lamp heating step and plasma is injected to maintain the cured hard photoresist while it is removed. In this case, the injected plasma is O ₂ plasma, and other reaction gases such as nitrogen (N ₂ ) may be added to improve reactivity. Since the plasma ashing method is commonly used, a detailed description thereof will be omitted.

4C illustrates a second frosting process for removing the remaining soft photoresist, wherein the lift pin is brought down to contact the wafer with the heating chuck while the heating chuck is held at 200 ° C. or higher, and then the soft photoresist is removed. Expose until removed.

The distance between the ramp and the wafer is about 50 to 300 mm, more preferably 120 to 140 mm, with the lift pin up. In addition, the length of the lift pin may be appropriately selected from 5 to 30mm, more preferably 10 to 20mm.

The length of the lamp and the wafer spacing and the lift pin may be appropriately selected depending on the number of lamps and the power consumption so that the wafer temperature is 130 to 170 ° C. when the lamp is turned on for 12 to 30 seconds with the lift pin up.

Since the thickness of the hard photoresist to be cured varies depending on the implantation time during ion implantation and the energy of the ions, the time of the first ashing step is difficult to determine uniformly, and may be appropriately selected according to the wafer.

Since the time of the second frosting step also varies depending on the thickness of the photoresist coated on the first wafer and the thickness of the hardened hard photoresist, it is difficult to determine uniformly and is appropriately selected according to the thickness of the soft photoresist.

5 is a graph showing the ashing time in the case of using the ashing apparatus and method according to the present invention in comparison with the conventional method.

5A is a conventional ashing method, in which a vacuum pumping is performed while a wafer is loaded into a device and heated. When the wafer is heated to about 80 ° C. by vacuum pumping and heating for about 20 seconds, plasma is injected to ashing. When using this process, the cured hard photoresist and soft photoresist are removed at the same temperature of about 80 ° C., which takes a lot of time and about 200 seconds from the time of loading the wafer.

FIG. 5B illustrates a case using the apparatus as described in the above-described US patent, in which a wafer is loaded and a vacuum pump is performed for about 20 seconds while the heating means is operated and the wafer support is moved to the position B. FIG. After the vacuum pumping is completed, the first step of removing the hard photoresist is performed by turning on the plasma and exposing the wafer for about 2 minutes until the temperature of the wafer gradually rises to about 120 ° C. After the cured photoresist is removed, the wafer support is moved to the bottommost position, and the ashing of the remaining second steps is performed. Using this method according to the US patent takes about 180 seconds of ashing time shorter than the conventional method as shown in FIG.

Figure 5c is a case of using the ashing apparatus and method according to the present invention, the lamp heating step of turning on the lamp and the vacuum heating step takes about 20 seconds, the time of about 60 seconds in the first ashing step at 130 ~ 170 ℃ Becomes In the second ashing step, it can be seen that the temperature of the wafer is heated to a high temperature for about 20 seconds without lowering the lift pin to the temperature of the heating chuck (250 ° C.). Thus, the overall ashing time is about 155 seconds, which is about 25 seconds shorter than the method according to the US patent.

In the conventional method according to the US patent, the first ashing step is performed while the temperature is gradually rising, while in the method according to the present invention, a temperature for rapidly performing the first ashing step by using lamp heating is increased to 130 to 170 ° C. The work time is shortened because the hard photoresist is removed while the wafer is heated.

Of course, when ashing a wafer without a cured photoresist using the apparatus according to the present invention, hot ashing may be performed in a conventional manner with the lift pins down without using a lamp heater.

FIG. 6 shows a change in wafer during the ashing process according to the present invention. FIG. 6A is a cross-sectional view of the wafer surface immediately before ion implantation, in which a photoresist 20 to be used as a protective film during ion implantation surrounds the gate electrode portion. have.

6B is a cross sectional view of the wafer after the ion implantation process is completed, and a hard photoresist 21 hardened on the top of the photoresist is formed by ion implantation. An uncured soft photoresist 22 is formed inside the hard photoresist.

FIG. 6C shows that the hard photoresist is removed as a wafer surface after the first ashing process according to the present invention, and in FIG. 6D after the second ashing process, all of the soft photoresist is removed.

Using the ashing apparatus and the ashing method according to the present invention, it is possible to perform the ashing operation of a large wafer of 300mm in a short time.

In particular, by using a halogen lamp heating means to quickly remove the cured photoresist of the high energy implanted wafer (popping) without popping, it is possible to significantly shorten the time required for the ashing process of the wafer .

Claims (8)

delete In the ashing apparatus for a semiconductor wafer, A wafer heating unit having a reaction chamber, a lamp heating unit provided at an upper end of the reaction chamber and having 3 to 12 lamps, a heating unit below the reaction chamber, and three or more lift pins disposed above the heating unit to support the wafer; It includes a lift pin that can be up or down to adjust the spacing of the heating means in two stages, The lamp heating unit, 3 to 12 lamps having one or more shapes of horseshoe-shaped (round), bulb-shaped, U-shaped, hemispherical and having a power consumption of 1 kW or less; At least one reflector for improving the heat reflection efficiency of the lamp, And a circular lamp housing for supporting the reflecting plate and the lamp. The method of claim 2, The lamp is made of eight halogen lamps of the U-shape, the reflecting plate is a semiconductor wafer ashing device, characterized in that consisting of four. The method of claim 2 or 3, And a distance between the wafer and the heating means is 5 to 30 mm, and a distance between the wafer and the lamp is 50 to 250 mm when the lift pin is up. A wafer heating unit having a reaction chamber, a lamp heating unit provided at an upper end of the reaction chamber and having 3 to 12 lamps, a heating unit below the reaction chamber, and three or more lift pins disposed above the heating unit to support the wafer; An ashing method using a semiconductor ashing device comprising a lift pin that can be up or down to adjust the spacing of the heating means in two steps, The wafer is loaded on the lift pin in the state where the lift pin is up while the heating means is maintained at 200 ° C. or higher, and the chamber is sealed. Then, the vacuum pump for vacuuming the inside of the chamber is operated. A lamp heating step of heating the temperature of the wafer to 130 to 170 ° C. by turning on the lamp and maintaining it for 12 to 30 seconds; A first ashing step of turning off the lamp after the lamp heating step and injecting plasma to maintain the cured hard photoresist while it is removed; And a second ashing step of bringing down the lift pins and exposing them until the soft photoresist is removed while the heating means continues to operate above 200 ° C. The method of claim 5, wherein The lamp heating unit, 3 to 12 lamps having one or more shapes of horseshoe-shaped (round), bulb-shaped, U-shaped, hemispherical and having a power consumption of 1 kW or less; At least one reflector for improving the heat reflection efficiency of the lamp, And a circular lamp housing for supporting the reflector and the lamp. The method of claim 6, The lamp is made of eight halogen lamps of the U-shape, the reflecting plate is a semiconductor wafer ashing method, characterized in that consisting of four. The method according to any one of claims 5 to 7, And a distance between the wafer and the heating means is 5 to 30 mm, and a distance between the wafer and the lamp is 50 to 250 mm when the lift pin is up.