JP2554857B2 - Asssing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ashing device for removing a film deposited on a wafer or the like, and more particularly to a photoresist film on a wafer (hereinafter simply referred to as resist) using ozone. ) Is related to the ashing apparatus suitable for the single-wafer processing which removes by oxidizing.

[Prior Art] A fine pattern of a semiconductor integrated circuit is generally formed by etching a base film formed on a wafer using a resist film of an organic polymer formed by exposure and development as a mask.

Therefore, the resist film used as the mask is
After the etching process, it needs to be removed from the surface of the wafer. An ashing process is performed as a process for removing the resist in such a case.

This ashing process is also used for removing the ink, removing solvent residues, etc., including cleaning of the silicon wafer and mask, and is suitable for performing a dry cleaning process in a semiconductor process.

An ashing process for removing the resist is generally performed by oxygen plasma.

In the ashing of resist by oxygen plasma, a wafer with a resist film is placed in a processing chamber, the oxygen gas introduced into the processing chamber is turned into plasma by a high-frequency electric field, and the oxygen atom radicals generated oxidize the resist, which is an organic substance. It utilizes the action of decomposing into carbon dioxide, carbon monoxide and water and vaporizing.

However, the ashing process using the oxygen plasma has a disadvantage that ions and electrons accelerated by an electric field existing in the plasma irradiate the wafer, which adversely affects the electrical characteristics of the semiconductor integrated circuit.

As a device for avoiding such a drawback, there is a device for generating oxygen atom radicals by similarly irradiating ultraviolet rays (UV) and performing an ashing process in a batch process. In this type of device, since there is almost no damage to the element by the electric field as compared with the plasma processing, there is an advantage that the element can be efficiently stripped and cleaned without damaging the element.

FIG. 17 shows a conventional ashing apparatus using ultraviolet irradiation.

A large number of wafers 101, 101 ... Are vertically arranged at a predetermined interval in the processing chamber 100, and ultraviolet rays from an ultraviolet ray emitting tube 103 installed in the upper portion of the processing chamber 100 are provided on the upper surface of the processing chamber 100. Irradiate through a transparent window 102 such as quartz
The oxygen filled in the processing chamber 100 is excited to generate ozone. An ashing process is performed by causing oxygen atom radicals generated from the ozone atmosphere to act on the wafer 101.

By the way, in recent years, wafers have been increasing in diameter,
Along with this, a single-wafer processing method for processing wafers one by one is becoming popular.

[Problem to be Solved] In the ashing process by the ultraviolet irradiation,
It has the advantage of not damaging the wafer, but has the disadvantage of being time consuming due to batch processing. Moreover, the resist ashing rate is only about 500 Å to 1500 Å / min because it is merely an action in an ozone atmosphere.

On the other hand, in single-wafer processing of wafers suitable for large diameters,
The processing speed is usually required to be about 1 μm to 2 μm / min, and a conventional apparatus for irradiating ultraviolet rays cannot sufficiently deal with single-wafer processing.

Further, there is a drawback that the apparatus must be increased in size due to the use of ultraviolet rays, and the apparatus becomes expensive.

[Object of the Invention] Therefore, in order to eliminate the above-mentioned problems of the prior art, the inventors of the present invention have stated that "a flow space through which a gas containing ozone flows is provided in contact with a wafer to cover the surface of the wafer. It proposes a technique of "oxidizing and removing the deposited film".

Here, in order to guarantee that the ashing process is completed, it is necessary to secure an extra ashing process time with a slight margin. This may lead to a state in which the ashed wafer is further ashed together with the processing overhead, which may cause a risk of damaging the wafer.

From this, in order to perform a more complete and more reliable ashing process and improve the operating rate of the device, it is necessary to detect the end point of the ashing process and move to the next ashing process in a short time. I came to solve this.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an ashing end point detection method that solves such problems.

[Means for Solving Problems] To achieve the above object, according to the present invention, a wafer is provided in contact with a space in which a gas containing ozone flows, and a film attached to the surface of the wafer is chemically reacted. In an ashing device that oxidizes and removes, a detection device that monitors the concentration of carbon dioxide in the exhaust gas generated as a result of the chemical reaction and detects a change point at which the concentration of carbon dioxide begins to decrease, and the carbon dioxide. An ashing device is provided, comprising: a detection device that detects a point at which is decreased to a certain value or less; and an end point determination device that determines an ashing end point based on a signal from each of the detection devices. As an example of the configuration of the end point determination device in this case, there is a combination of a comparator with a differentiation circuit or a peak detection circuit.

[Operation] For example, an ozone outflow portion is provided at a position opposed to the wafer at a predetermined interval, a gas flow space of ozone + oxygen is formed between the ozone outflow portion and the wafer, and new ozone is continuously supplied to the wafer surface. This accelerates the oxidation chemical reaction between the oxygen atom radicals and the film deposited on the wafer, and at the same time vaporizes carbon dioxide, carbon monoxide, water, etc. generated after the reaction by oxygen (O ₂ ) that is not a radical. It can be moved and discharged from the wafer surface as it is.

As a result, it is possible to efficiently expose the reaction surface of a film deposited on the wafer, for example, a film of an organic material, to oxygen atom radicals that perform an extremely strong oxidizing action.

Therefore, high-speed ashing processing can be performed, and an ashing apparatus suitable for single-wafer processing can be realized.

Then, when the ashing process is completed and the process proceeds to the next ashing process, the concentration of carbon dioxide in the exhaust gas generated as a result of the chemical reaction by the process is monitored as described above, and the concentration of the carbon dioxide decreases. The ashing end point is determined by the end point determination device based on the starting change point and the point decreased below a certain value. Therefore, since it is not necessary to wait until the concentration of carbon dioxide becomes zero, the transition time to the next ashing process can be shortened and the throughput is also improved. Also, there is little risk of damaging the wafer.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of an example of an ashing device of the present invention, FIG. 2 is another similar device, and a sectional explanatory view showing an overall configuration including a wafer transfer mechanism, and FIG. 3 ( (a) And (b) is a concrete explanatory view of the electrostatic chuck in the wafer conveyance mechanism, (a) is a II sectional view of the same figure (b), (b) is the top view, FIG. 4 is an enlarged explanatory diagram of the reaction part, and FIG. 5 (a) is a diagram for explaining the relationship between the reaction by oxygen atom radicals and transfer,
5 (b) and 5 (c) are views for explaining the relationship between the diffusion opening and the ashing state on the wafer surface, respectively.
The figure is a graph explaining the relationship between the decomposition half-life of ozone and the temperature of the diffusion opening.

FIG. 7 is a graph for explaining the relationship between the gas flow rate and the ashing rate at a wafer surface temperature of 300 ° C. FIG. 8 is an ashing rate for the gap between the diffusion plate and the wafer surface at a wafer surface temperature of 300 ° C. FIG. 9 is an explanatory diagram showing the relationship between the gas temperature and the resist removal rate, and FIGS. 10 (a), (b),
(C), (d), (e) and (f) are explanatory diagrams of specific examples of the opening of the diffusion plate, respectively, and FIGS. 11 (a), (b) and
(C) and (d) are explanatory diagrams of a specific example of a gas cooling structure in an injection unit, respectively. FIG. 12 (a) is an explanatory diagram of a method of rotating a gas injection unit, and FIG. FIG. 13 is an explanatory diagram of an ashing effect when the wafer is not rotated, FIG. 14 is a block diagram of an embodiment of an ashing processing system for determining the end of the ashing process, and FIG. FIG. 16 is a graph showing a change in the concentration of carbon dioxide in the exhaust gas, and FIG. 16 is a graph for explaining a relationship between the ashing speed and the ozone concentration.

In FIG. 1, reference numeral 1 denotes an ashing processing system, which is an ashing device 2, an ozone + oxygen gas supply device 3 for supplying oxygen gas containing ozone to the ashing device 2, and an exhaust gas connected to the ashing device 2. Device 4,
A temperature controller 6 that controls the temperature of the wafer by adjusting the heat generation state of the elevating device 5 that vertically moves the wafer mounting table 21 disposed inside the ashing device 2 and the heating device 21a provided inside the wafer mounting table 21. It has and.

The ozone + oxygen gas supply device 3 is a gas flow controller.
3a, an ozone generator 3b, an oxygen supply source 3c,
The ozone concentration, the gas flow rate, and the gas pressure in the ashing device 2 (processing chamber) are controlled by the gas flow controller 3a, the ozone generator 3
b, the oxygen supply source 3c and the exhaust device 4 are adjusted.
In particular, the ozone concentration supplied to the ashing device 2 is adjusted by the ozone generator 3b and set to a predetermined value.

Further, the wafer mounting table 21 arranged inside the ashing device 2 is for holding the wafer 28 by suction, and the temperature of the held wafer 28 is maintained at a predetermined value by the temperature controller 6.

On the upper part of the wafer 28, there is provided a cone-shaped (cone-shaped) injection part 22 for injecting ozone + oxygen gas at an interval of about 0.5 to 20 mm from the surface of the wafer 28. The wafer mounting table 21 is raised by 5 and set to a predetermined value. In this case, the injection unit 22 may be moved up and down by a lifting device.

The injection unit 22 is made of SUS (stainless steel), Al, or the like, and has a disc-shaped diffusion plate 22a on the surface facing the wafer 28, which is parallel to the surface of the wafer 28. Then, the process of loading and unloading the wafer 28 is performed by the wafer mounting table 21.
Is lowered by the elevating device 5, the space between the diffusion plate portion 22 and the wafer 28 is enlarged, and the arm of the wafer transfer mechanism enters the space.

In the ashing process, the wafer 28 on the wafer mounting table 21 is set in a range of about 150 ° C. to 500 ° C., particularly, in a range of 200 ° C. to 350 ° C.
It is performed by heating the wafer to a specific value of ° C, and the mixing ratio of ozone and oxygen by the generated ozone is adjusted by the ozone generator 3c. Then, the oxygen gas containing this ozone, for example, about 3 to 15 / min, is sent into the ashing apparatus 2 which is the processing chamber. The gas pressure in the ashing device 2 at this time is set in the range of, for example, about 700 to 200 Torr.

Next, a process of loading / unloading the wafer 28 into / from the processing chamber of the ashing device 2 will be specifically described based on the ashing device 30 shown in FIG. The ashing device 30 differs from the ashing device 2 shown in FIG. 1 in that the injection unit is moved up and down instead of moving the wafer mounting table up and down.

2, the ashing device 30 includes a processing chamber 20 and loader / unloader units 23a and 23b disposed on both sides thereof.
The loader / unloader units 23a and 23b are provided with belt transport mechanisms 24a and 24b, respectively, provided inside the loader / unloader units 23a and 23b.

Here, the loader / unloader section 23a, the belt transport mechanism
The side 24a is the side for loading the wafer, and the loader / unloader unit 23b and the belt transport mechanism 24b are the side for unloading the ashing-processed wafer. Either may be the loading side or the unloading side. Furthermore, the loader / unloader section
There may be only one of them.

Although not shown, the belt transport mechanisms 24a and 24b
Cartridges for stacking and accommodating wafers at predetermined intervals are installed at the opposite ends of the cartridges. By moving the cartridges up and down, the wafers before processing are sequentially loaded from the cartridge by the belt transfer mechanism 24a. / It is sent to the unloader unit 23a. The ashing-processed wafers are sequentially stacked and stored in the cartridge from the loader / unloader unit 23b via the belt transport mechanism 24b.

The processing chamber 20 includes an Al chamber 29 coated with, for example, SUS, Al, or TiN, and a wafer mounting table 205 is installed in the center of the inside thereof. A gas injection unit 22a is supported on the upper side of the chamber 29 at a predetermined interval on the ceiling side of the chamber 29 so as to be vertically movable.

Here, the gas injection part 22a has a conical shape composed of a disc-shaped diffusion plate 200 and a cone part 203 connected thereto, and the cone part 203 has an ozone + oxygen gas introduction pipe 202. Is connected at the top of it, and the introduction pipe 202 is
A metal bellows 201 made of SUS or the like is hermetically sealed so as to be able to move up and down, and ozone + oxygen gas required for a reaction for ashing is introduced from the introduction pipe 202.

Reference numeral 204 denotes a cooler for ozone + oxygen gas that spirally covers the outer periphery of the cone 203, and is fixed to the cone 203 by heat conductive cement or the like. And the cooler 204, the refrigerant is introduced from below the cone section 203,
It is configured to be discharged at the apex and guided to the outside.

On the other hand, as shown in FIG. 4, the diffusion plate 200 has a slit (opening) 31 for blowing out gas, and blows out cooled ozone + oxygen gas uniformly to the surface of the wafer 28. .

The diffusion plate 200 is supported at three points by ball screw mechanisms 231, 232, and 233 at substantially 120 ° intervals in the peripheral portion thereof, and moves up and down. The driving is performed by engaging gears formed in the ball portions 234, 235, 236 (not shown in the figure) of the ball screw mechanisms 231, 232, 233 with worm gears engraved on the rotary shaft 236 of the motor 230.

Note that the lifting mechanism of the injection unit 22a may be configured to directly move up and down by using an air cylinder or the like instead of such a combination of the motor, the ball screw, and the gear.

In the position shown in the figure, the ejection unit 22a is in the raised state (standby position), and the wafer 28 is carried into or out of the wafer mounting table 205. on the other hand,
As shown in FIG. 4, when the injection part 22a descends,
The blowing surface of the diffusion plate 200 is spaced from the wafer surface by about 0.5 to several mm or about 10 mm (reaction position).
The wafer on the wafer mounting table 205, which is positioned above the 205.
Gas is supplied to the surface of 28.

Note that a heating device 206 is provided inside the wafer mounting table 205 to heat the wafer mounting table 205.
In addition, in this example, in addition to the gas containing ozone, the flow of the gas from the diffusion plate 200 does not affect the chamber 29, and an N ₂ gas is introduced into the chamber 29 so as to cover the gas. I have.

Now, 26a is an adsorption chuck portion supported on the tip side of the transfer arm 25a, and 10a is an electrostatic chuck supported on the adsorption chuck portion 26a that moves up and down with respect to the main body of the adsorption chuck portion 26a. is there. The figure shows a state in which the wafer 28 is attracted to the electrostatic chuck 10a. The suction of the wafer in this case may be suction by negative pressure or mechanical clamping or holding.

The transfer arm 25a has the other end fixed to a support member 27a arranged in the loader / unloader unit 23a, and moves back and forth between the loader / unloader unit 23a and the wafer mounting table 205 of the processing chamber 20. Is the arm of. The transfer arm 25a may be composed of a magnetic cylinder, an air cylinder, or the like.

Here, the reason for using the frog leg transport mechanism is
The transport mechanism can be miniaturized and, for example, a loader /
If an ashing processing chamber is provided on both sides of the unloader section and the support member 27a of the frog leg transport mechanism is rotatable,
Since the frog-leg transfer mechanism can be directed to the desired chamber side, there is an advantage that the wafer can be selectively transferred or unloaded to the chambers on both sides.

In addition, the loader /
If the unloader section is provided linearly and the supporting member 27a is made rotatable, it is also possible to pick up a wafer from the belt transfer mechanism side, reverse it, and transfer it to the chamber side. Even in such a case, the whole apparatus can be realized as a small one.

The loader / unloader type 23b is also provided with a frog leg transfer mechanism type transfer arm 25b, a suction chuck portion 26b, an electrostatic chuck 10b thereof, and a support 27b which are similar in symmetry. In the figure, the electrostatic chuck
The processed wafer 28 is adsorbed on 10b.

Therefore, the wafer mounting table 205 has a hole 2 for vacuum suction.
20 are provided. In addition, around the wafer mounting table 205, in order to exhaust the exhaust gas after the reaction as evenly as possible, a plurality of exhaust openings provided annularly at predetermined intervals.
219, 219 ... are provided on the ring plate 222,
The ring plate 222 is fitted on the outer peripheral side of the wafer mounting table 205 at a position slightly lower than the upper surface of the wafer mounting table 205.

Reference numerals 221 and 223 denote exhaust pipes for exhausting the chamber 29, respectively, which are connected to the pump of the exhaust device 4. These exhaust pipes 221 and 223 are provided in two or more in number so that the exhaust is uniformly performed, but the number may be one. 224 and 225 are gate valves, respectively.

Further, 226 and 227 are conveyor belts of the belt conveyor mechanisms 24a and 24b, respectively, and 217 and 218 are loader / unloader section 2 respectively.
These are chambers 3a and 23b. Here, the chambers 217 and 218 of the loader / unloader units 23a and 23b may be evacuated by a vacuum pump in accordance with the internal pressure of the chamber 29.

Next, the operation of this device will be described.
It is assumed that a is set to the ascending state, held at the standby position, and the valve of the gas inlet 202 is closed.

When gate valves 224 and 225 are closed, chamber 2
Inside 01 is in a reduced pressure state close to normal pressure.

In the case of raising and lowering the wafer mounting table 21 of FIG. 1, the elevating device 5 is driven to lower the wafer setting table 21 and set it to the standby position. However, the relationship between the loader / unloader section is the same as that shown in FIG.

Now, in this state, the gate valve 224 is opened to lower the electrostatic chuck 10a of the wafer 28 carried into the loader / unloader section 23a from the belt transfer mechanism 24a, and a voltage is applied to the wafer 28 to cause the suction chuck 26a. Adsorb. Then, the electrostatic chuck 10a is raised to pick up the wafer 28. Next, the transfer arm 25a is extended, and the sucked wafer 28 is transferred from the loader / unloader unit 23a to the processing chamber 20 and positioned on the wafer mounting table 205 to lower the electrostatic chuck 10a and reduce the applied voltage. Alternatively, the wafer 28 is dropped by its own weight with zero. Then, the wafer is mounted on the wafer mounting table 205 by attracting the wafer to the wafer mounting table 205 under a negative pressure.

Next, after raising the electrostatic chuck 10a, the transfer arm 2
5a is reduced and suction chuck 26a is loaded into loader / unloader 2
Return to 3a. After the suction chuck 26a moves to the loader / unloader section, the gate valve 224 is closed, the injection section 22a is lowered to the reaction position, and the diffusion plate 200 is set at the reaction position shown in FIG.

In the case of the ashing device 2 shown in FIG. 1, the wafer mounting table 21 is raised by the raising device 5 to set the wafer 28 at the reaction position.

Here, the temperature of the wafer 28 is monitored, and when the temperature reaches a predetermined ashing processing temperature, the valve of the gas inlet 202 is immediately opened, and ozone + oxygen gas is applied to the surface of the wafer 28 set on the wafer mounting table 205. Spray evenly.

As a result, the resist of the wafer 28 is oxidized, and gases such as carbon dioxide, carbon monoxide, and water generated by this chemical reaction are exhausted by the exhaust device 4 through the exhaust pipes 221 and 223 together with oxygen after the reaction. .

When the ashing process is completed (for example, 1 min to several mi
In step n), the valve of the gas inlet 202 is closed and the diffusion plate 200 is raised to the standby position (in FIG.
5 down to the standby position) and gate valve 2
25, the transfer arm 25b is extended from the loader / unloader section 23b to the processing chamber 20, the suction chuck 26b is moved onto the wafer mounting table 205, and the electrostatic chuck 10b on the tip side thereof is lowered to Voltage. Then, the ashing-processed wafer 28 is sucked on the wafer mounting table 205, and the electrostatic chuck 10b is lifted and picked up. After raising the electrostatic chuck 10a, the transfer arm 25b is reduced and the processed wafer 28 is carried out to the loader / unloader unit 23b.

The wafer thus unloaded to the loader / unloader section 23b is transferred from the loader / unloader section 23b to the belt transfer mechanism 24b and stored in the cartridge, and the ashed wafer is taken out of the apparatus.

Here, the electrode portion of the electrostatic chuck will be described. In FIG. 1, the electrostatic chucks 10a and 10b have the same configuration.
The electrode section is referred to as an electrostatic chuck electrode section 17.

As shown in FIGS. 3 (a) and 3 (b), the electrode portion 17 of the wafer suction electrostatic chuck 10 has a semi-circular plate-like shape having semicircular recesses 11a and 12a inside the back surface. It is formed by first and second electrodes 11 and 12 made of a conductor such as a metal.

By the way, in the case of automatically carrying a wafer, it is often overwhelmingly required to suck the wafer from the front surface side and carry it. Therefore, the electrode section 17 is attached so that its suction surface side is downward in a state of being suspended from the wafer transfer device as an electrostatic suction chuck.

Here, the first and second electrodes 11 and 12 are thinly coated with the insulating films 13 and 14, and are arranged with a predetermined gap D therebetween. The gap D may be a void, or an insulator may be inserted depending on the structure. The selection may be determined from the overall structure of the electrostatic chuck 10.

As shown in FIG. 3A, the first and second electrodes 11 and 12 are recessed inside (depth h), leaving a portion of width W on the outer periphery of a substantially semicircle having a radius R. The portion having the width W forms the suction portions 15 and 16 of the semiconductor wafer. The surface of each of the adsorbing portions 15 and 16 has an insulating film 1 as a part of the insulating films 13 and 14.
5a and 16a are provided as coated layers, and the film thickness of these insulating films 15a and 16a is determined by the suction force of the wafer and the like. And insulating film other than this part 13,1
The thickness of 4 is determined in consideration of the fact that this electrode portion has a sufficient withstand voltage when it comes into contact with another metal portion or the like.

Next, the ashing reaction will be described in detail with reference to FIG. 4, FIG. 5 (a) and FIG.

As shown in FIG. 4, in the ashing process, the ozone supplied from the ozone + oxygen gas supply device 3 is in the following thermal parallel state inside the injection section 22a (or the same applies to the injection section 22 and below). Has become.

O ₃ O ₂ + O In this case, the lifetime of the oxygen atom radical O obtained by the decomposition of ozone depends on the temperature, and as shown in FIG.
In the vicinity, it is very long. However, when the temperature rises, its life is rapidly shortened.

On the other hand, the ashing process using oxygen atom radicals is an oxidative chemical reaction, and the faster the process, the higher the temperature.
Moreover, it takes some time for the oxygen atom radicals to act on the wafer surface. Therefore, how to efficiently supply oxygen atom radicals to the surface of the wafer 28 is an important problem.

The ashing process proposed in the present invention is to efficiently supply oxygen atom radicals to the surface of the wafer 28 and quickly remove reaction products from the wafer surface. In the processing of the synergistic effect with the supply of radicals, the ashing speed can be increased to a processing speed suitable for single-wafer processing.

Therefore, while supplying oxygen atom radicals,
It is important to create a suitable gas flow space to eliminate reaction products.

In this embodiment, as shown in FIG. 4, the gas flow space is formed between the wafer mounting table 205 and the diffusion plate 200 of the injection unit 22a.

The distance between the wafer mounting table 205 and the diffusion plate 200 is relatively narrow, and if the heating temperature of the wafer 28 is set high, it is necessary to set it to about 0.5 to several mm with respect to the wafer surface. Become. The outermost opening position (position of the slit 31a in FIG. 4) is determined so that the gas to be jetted is blown outward by 5 mm or more from the outer shape of the wafer 28.

By blowing the gas outside the outer shape of the wafer 28 in this way, a negative pressure region is formed by the gas flow outside the outer peripheral portion of the wafer, and the generated gas from the central portion side is transported to the outer side of the outer periphery of the wafer faster, To discharge.

As a result, there is an effect that the supply of ozone and the contact of oxygen atom radicals to the wafer surface are facilitated, and the oxidation reaction can be promoted.

Now, the ozone + oxygen cooled by the cooler 204 is
For example, it is cooled to 25 to 50 ° C. Therefore, the rate at which oxygen atom radicals are retained inside the cone 203 of the injection unit 22a increases.

Then, as soon as ozone (O ₃ , O ₂ + O) and oxygen O ₂ are jetted from the opening of the diffusion plate 200, they are exposed to the high temperature atmosphere. Then, the film deposited on the wafer surface is ashed (ashed, that is, oxidized and removed from the wafer surface).

As shown in FIG. 5 (a), carbon dioxide, carbon monoxide, and vaporized water generated by ashing rise simultaneously and are ejected from the diffusion plate 200 as oxygen (O ₂ ) and ozone (O ₃ ) that is not a radical. ), Is removed from its surface, and is discharged from the exhaust opening 219 of the ring plate 222 to the exhaust pipe 221,
It is carried to 223 and is sequentially exhausted by 4 to the exhaust device.

Therefore, the surface of the wafer 28 can create an environment that is always exposed to oxygen atom radicals. In FIG. 5A, 28a is a surface portion of the wafer 28, 28b is a resist portion deposited on the wafer 28, and an arrow 32 is ozone + oxygen from the diffusion plate 200. The flow of gas is shown.

Here, the wafer temperature is set to 300 ° C. and the wafer mounting table 205
The ashing speed with respect to the gas flow rate in the standard state (normal temperature and normal pressure conditions) at the opening of the diffusion plate 200 is measured using the gap (gap) between the surface of the diffusion plate and the diffusion plate 200 (at the injection port side) as a parameter. And as you can see in Figure 7,
For a 6 ″ wafer, particularly in the range of about 2 sl to 40 sl (sl: flow rate at normal temperature and normal pressure conversion), particularly high-speed ashing processing is possible, and the direction gradually becomes saturated from about 40 sl / min.

In order to correspond this flow rate to a general wafer diameter, when converted to a flow rate per unit area of the wafer, 0.01 to 0.25 sl
/ min · cm ² .

Also, when the relationship between the ashing speed and the gap between the diffusion plate and the wafer surface was measured with the gas flow rate as a parameter at a wafer surface temperature of 300 ° C., as shown in FIG. Irrespective of the above, a characteristic is shown in which the value converges toward a constant value.

Further, regarding the relationship between the temperature of the gas ejected from the diffusion plate 200 and the resist removal rate, the gap with the wafer (from the surface of the wafer 28 placed on the wafer mounting table 205 to the diffusion plate 2
When the reaction time is 1 mm, the gas flow rate is a parameter, and the characteristics are measured. As shown in FIG. 9, when the temperature is increased to about 200 ° C., It can be understood that it is difficult to remove.

Therefore, when the wafer side is heated to 200 ° C or higher to carry out the reaction, the injected gas (ozone + oxygen) is
Cooling is preferred. And as a particularly preferable range, the outflow gas temperature of the diffusion plate 200 is 15 to 50 ° C.

This is in agreement with the characteristic of ozone decomposition half-life, which was seen in FIG.

Further, as shown in FIG. 16, when the relationship between the ashing speed and the ozone concentration is investigated, the ashing speed increases as the ozone concentration increases. However, at about 10% by weight or more, it shifts to the saturation direction.
The characteristics were measured for a 6 ″ wafer, the temperature of which was 250 ° C., the gas flow rate was 5 sl / min, and the chamber pressure was about 700 Torr. Things.

As can be understood from the respective characteristic graphs, a flowing gas space is formed above the wafer, and a gas containing ozone is jetted or discharged from the wafer, thereby forming a fluid gas space.
Ashing processing of several μm / min becomes possible. This realizes ashing suitable for single-wafer processing and suitable for processing large-diameter wafers.

FIGS. 10 (a) to 10 (d) are explanatory views of a specific example of a diffusion plate 200 for uniformly injecting ozone + oxygen gas onto the surface of a wafer.

FIG. 10 (a) shows four arc-shaped slits 311 formed in a circular shape and a concentric shape. The grooves may be perpendicular to the wafer, but the gas flow to the outer side. In order to form the gas, an oblique slot is formed so that gas flows out toward the outside.

In FIG. 10 (b), holes 312 are provided at the center of the circle, and slits 313 are arranged radially to the holes.
In FIG. 10 (c), holes 314 are provided radially, and each hole 314 is slightly larger outward. FIG. 10 (d)
A sintered alloy 200a is used as the diffusion plate 200,
Porous holes 315 are uniformly provided over the entire surface of the plate.

In FIG. 10 (e), the injection port 316 is formed in a spiral shape, and in FIG. 10 (f), the small hole 317 is simply formed in a circular shape.

Here, in order to study the effect of evenly outflowing the gas from the diffusion plate 200, the holes are sparsely formed as shown in FIG. 10 (f) and the sintered alloy 200a of FIG. 10 (d) is used. Compared with the case where the porous pores are evenly distributed,
In the former case, as shown in FIG. 5 (b), the resist portion 28b is ashed in accordance with the gas flow 32 (arrow), and the ashing is undulating. On the other hand, when the porous pores are uniformly distributed as in the latter sintered alloy, uniform ashing is performed as shown in FIG. 5 (c).

Therefore, it is preferable to provide a gas injection port so that the gas becomes more uniform. This has the advantage that the processing time until complete ashing can be shortened, and the wafer is hardly damaged even if ozone is applied to the wafer surface. . In FIGS. 5 (b) and 5 (c), the portion shown by the dotted line is the surface position (thickness) of the resist before ashing.

As shown in the characteristic graphs of FIG. 6 and the like, it is preferable that the gas (ozone + oxygen) be injected from the diffusion plate while being cooled as much as possible.

By the way, the distance between the wafer mounting table 205 and the diffusion plate 200 is
Relatively close. On the other hand, the wafer mounting table 205 and the wafer 28
Heated by the heating device 206 to the reaction temperature. Therefore, the diffusion plate 200 is heated by radiation heat or the like radiated from the wafer mounting table 205 and the wafer 28 side, and the surface of the diffusion plate 200 tends to increase in temperature.

As a result, the temperature of the gas rises near the injection port and the amount of oxygen atom radicals supplied to the wafer surface decreases. In particular, if the gap is large, the effect of heat is somewhat reduced, but since the time for the oxygen atom radicals to move is long, the life of the oxygen atom radicals is exhausted by the time it reaches the surface of the wafer 28, including the effect of temperature rise. Also increases. Also,
If the gap is too small, the temperature of the surface of the diffusion plate 200 tends to be higher due to the direct influence of the temperature on the wafer mounting table 205 side. In addition, the temperature rise value differs depending on the flow rate of the gas blown from the diffusion plate 200.

For this reason, there are more optimal conditions in the ashing process. In the reaction mode shown in FIG. 4, when the temperature of the wafer is about 200 ° C. to 350 ° C., the more optimal gap is about 1 to 3 mm, and the flow rate of the gas is normal temperature and normal pressure. For 6 ″ wafer, 5.5 ~ 17sl /
It is about min. Therefore, when this is converted into the flow rate per unit surface area of the wafer, it is 0.03 to 0.1 sl / min · cm ² .

Also, carbon dioxide reacted by oxygen atom radicals,
Considering that reaction products such as carbon monoxide and water are carried out of the wafer surface mainly by oxygen (O ₂ ),
There is a more efficient weight percent of ozone and oxygen.

That is, if the amount of ozone (O ₃ ) is small, the rate of ashing (the rate of decrease of the unit time with respect to the film thickness) becomes low, resulting in poor uniformity and poor efficiency. On the other hand, when the amount of ozone (O ₃ ) is large and the amount of oxygen (O ₂ ) is small, the rate is high, but stagnation of reaction products occurs on the wafer surface and the reaction rate decreases.

Taking these points into consideration, the optimum weight% of ozone is about 3 to 5% by weight.

Now, in consideration of such a situation, a specific example of the cooling structure of the injection unit for injecting the gas having the lowest possible temperature together with the uniform gas injection will be described below.

In the injection unit 22b shown in FIG. 11 (a), a cooling pipe 207a made of a flexible pipe is also arranged on the inner surface of the diffusion plate 200, and the cooling pipe 207a is installed in the cooling unit 20.
It communicates with 4, which is a meandering crawler that avoids the slit 318 for gas injection.

The injection unit 22b shown in FIG. 11 (b) has a cooling pipe 204b, which is a flexible tube, provided on the outer surface (wafer 28 side) of the diffusion plate 200 and communicated with the cooler 204. Similarly, it is meandering and crawling in a state where the slit 318 is avoided. In this case, in FIGS. 11A and 11B, the cooler 204 disposed around the cone portion 203 may not be provided.

By doing so, even if there is thermal radiation from the wafer mounting table 205 side, the surface of the diffusion plate 200 can be suppressed to a low state, the temperature of the gas to be injected can be suppressed, and under more free conditions An efficient ashing process can be performed.

The injection portion 22c shown in FIGS. 11 (c) and (d) is not a conical shape but a cylindrical shape, and has a dome 22d for gas diffusion at an upper portion. Diffusion plate with slit after gas is diffused in advance
311 or sintered alloy 200a is sent to the diffusion plate.

In particular, in FIG. 11 (c), a snake-shaped cooler 204c is built in the inside of the cylindrical portion, and in FIG. 11 (d), a ball 200b having a relatively large diameter is provided in order to make the injection uniform. It is filled inside. In addition, although a cooler is not provided on the outside, it is a matter of course that a cooling pipe may be provided outside the cylindrical portion as in FIGS. 11 (a) and 11 (b).

Next, an example will be described in which the gas is blown more uniformly onto the wafer surface, and the wafer and the diffusion plate are relatively rotated for the purpose of promoting the oxidation reaction.

The injection unit 33 shown in FIG. 12 (a) is composed of a diffusion tube 34 and a gas introduction tube 35 communicating with the central portion thereof. The gas introduction tube 36 is rotatable on the ceiling side of the chamber 29 so as to be rotatable. It is pivoted.

Here, the diffusion tube 34 is closed at both ends, and a plurality of injection ports 36, 36, ... That diffuse and blow out gas are arranged at predetermined intervals on the opposite surface side of the wafer 28. ing. In addition, injection ports 37 and 38 are provided at positions opposite to each other on the end side surfaces (the side perpendicular to the wafer surface), and when the gas is injected from these, the diffusion pipe 34 is formed.
Rotates on its own by the reaction. In addition, the gas injected from both ends is located outside the outer periphery of the wafer 28 and also serves to transport the ashing product to the outside. Instead of the injection port 36, a porous material may be used on the lower surface of the diffusion tube 34.

In the example shown in FIG. 12 (b), the wafer mounting table 205 is axially supported, and this shaft is pivotally supported on the floor surface side of the chamber 29.
In this example, a motor is used to rotate the wafer mounting table 205. Note that the injection unit 22a may be a tubular one or a rod-like one as shown in FIG. 12 (a).

Comparing the effects of the case where the rotation operation is performed and the case where the rotation operation is not performed, when the rotation method is used, the processing time for removing the resist on the wafer is reduced. That is, comparing the case where the rotation is not performed in the same processing time as the rotation method and the case where the rotation is not performed, as shown in FIG. 13, the resist is removed at the central portion of the wafer when the rotation is not performed. In the periphery, the remaining resist
A phenomenon is observed in which 40 is not removed and remains as a striated pattern.
Note that this was performed on a 6 ″ wafer.

From this, it can be said that the rotation processing is effective in shortening the ashing processing time, and is also effective for the ashing processing in the peripheral part except the central part of the wafer. In particular, it is effective for a large-diameter wafer such as 6 ″ to 10 ″. In the case of FIG. 12 (a), since the gas injection unit is automatically rotated, there is an advantage that the apparatus is simple, but the gas must be injected more. On the other hand, in the case of FIG. 12 (b), since the wafer mounting table 205 side is rotated, the apparatus is somewhat complicated, but there is an advantage that the gas injection amount is small.

Next, detection of the end of the ashing process related to the overall control when performing the single-wafer process will be described.

As shown in FIG. 14, the gas analyzer 7 is interposed before the exhaust device 4 when the ashing process is completed. Then, the detection signal corresponding to the carbon dioxide (CO ₂ ) concentration obtained from the gas analyzer 7 is input to the end point determination / control device 8 to monitor the concentration of carbon dioxide, and the concentration starts to decrease and falls below the reference value. When a certain time is added to the time point, it is determined that the ashing process is completed.

Here, the end point determination / control device 8 has a comparator and a controller constituted by a microprocessor inside, and receives an ashing processing end point detection signal from a comparator that receives an output of the gas analyzer 7, and performs ashing. Device 2, gas introduction pipe (gas introduction pipe 202 in FIG. 2)
(See FIG. 2).
230) to control.

That is, when the end point is detected, a signal for closing the valve of the gas introduction pipe is generated, and control for stopping gas injection is performed. At the same time, a lowering signal of the wafer mounting table 21 is sent to the elevating device 5 and controlled to increase the gap between the diffuser plate and the wafer mounting table, thereby increasing the wafer mounting table (see FIG. 2). In the example, the injection unit is moved to the standby position.

At the time of receiving the standby position setting signal from the lifting device 5, the end point determination / control device 8 causes the gate valve (the second valve) communicating with the loader / unloader unit on the wafer unloading side (see the loader / unloader unit 23b in FIG. 2). A control signal for releasing the gate valve 225) shown in the figure is sent to the ashing device 2. Upon receiving this signal, the ashing apparatus 2 releases its gate valve to make the chamber (see the chamber 29 in FIG. 2) communicate with the loader / unloader unit on the wafer unloading side.

Next, the end point determination / control device 8 sends to the ashing device 2 a signal for operating the carry-out side wafer handling mechanism (transfer arm 25b in FIG. 2). The ashing device 2 is
In response to this signal, the suction and holding of the wafer 28 is released and the wafer handling mechanism is operated to pick up the wafer 28 on the wafer mounting table 21 (see the wafer mounting table 205 in FIG. 2) and carry it out of the chamber. To do. Then, the wafer is transferred to a belt transfer mechanism (see belt transfer mechanism 24b in FIG. 2).
Hand over to

On the other hand, when the unloading of the wafer from the chamber by the unloading-side wafer handling mechanism is completed, the ashing device 2 sends a completion signal to the end point determination / control device 8. Upon receiving the completion signal, the end point determination / control device 8 sends a control signal to the ashing device 2 to close the gate valve (gate valve 225) communicating with the loader / unloader on the wafer unloading side. Then, the valve is closed and the loader / unloader on the wafer carry-out side is separated.
Next, a control signal for releasing a valve (valve 224 in FIG. 2) communicating with the loader / unloader unit (see the loader / unloader unit 23a in FIG. 2) on the wafer loading side is sent to the ashing device 2. The ashing device 2 releases its valve to make the chamber communicate with the loader / unloader unit.

Next, the end point determination / control device 8 sends out a signal for operating the carry-in side wafer handling mechanism (the transfer arm 25a in FIG. 2) from the ashing device 2. The ashing device 2 is
The wafer handling mechanism on the loading side is operated to pick up the wafer 28 from the belt transport mechanism (see the belt transport mechanism 24a in FIG. 2), which is loaded into the chamber and placed on the wafer mounting table 21 (wafer mounting table 205). To install. Then, the wafer mounting table 21 holds the wafer by suction. When the completion of the wafer loading of the loading side wafer handling mechanism is completed and the arm or the like returns to the loader / unloader, the ashing device 2 sends a loading completion signal to the end point determination / control device 8.

Upon receiving this signal, the end point determination / control device 8 sends a control signal for closing the valve communicating with the loader / unloader unit on the wafer loading side to the ashing device 2 and also sends the wafer mounting table 21 to the elevating device 5. (A descending signal of the injection unit 22 in FIG. 2).

Ashing device 2 receiving control signal to close valve
Block the valve, load the chamber and loader / loader
Separate from the unloader section. On the other hand, the elevating device 5 that has received the lift signal of the wafer mounting table 21 controls the wafer mounting table 21 to set the gap between the diffusion plate and the wafer mounting table to a gap necessary for the reaction (set to the reaction position). ).

Upon receiving the reaction position setting signal from the lifting / lowering device 5, the end point determination / control device 8 generates a signal to open the valve of the gas introduction pipe, and performs control to start gas injection.
Then, the exhaust gas is monitored to start an end point determination process.

FIG. 15 is a graph showing a change in the concentration of carbon dioxide in the exhaust gas in this case.

As shown in the figure, the concentration of carbon dioxide gradually increases to a constant value as the ashing time elapses, and when the temperature of the gap of the oxidation reaction space and the temperature of the wafer and the gas flow rate are in the optimum range, 6 ″ The ashing process is completed within 1 minute for the wafer and within 1 to several minutes depending on the temperature of the gap and the wafer and the gas flow rate.

Therefore, the end point determination of the ashing process can be predicted on the basis of a change point where the carbon dioxide concentration starts to decrease or a point where the carbon dioxide concentration has decreased to a constant value close to zero.

On the other hand, as seen in this graph, the tendency that the gas generation starts to decrease from a constant value and becomes zero becomes almost the same characteristic in the exhaust gas. Therefore,
By detecting the change point A of this characteristic or the point B that has decreased below a certain value, the end point can be predicted.

The detection of the decreased point B may be performed by changing the reference value of the comparator, and the prediction end point can be determined by adding a certain time to the detection point.

The detection of the change point A can be easily realized by combining a differentiating circuit or a peak detecting circuit with a comparator.

By the way, when detecting that the amount of exhaust gas is equal to or less than the predetermined value, the gas analyzer 7 and the determination unit of the end determination / control device 8 shown in FIG. Detector (gas sensor) that detects a value or a specific range
And an end point determination circuit (a determination process by a comparator, a logic circuit, or a microprocessor) that determines the end time point from the detection signal is sufficient. On the other hand, when detecting the change point of the exhaust gas, a measuring instrument that generates a signal corresponding to the amount of the specific gas as a detection signal, a sensor, or a sensor that detects only the change state is required.

As described above, in the embodiment, the diffusion plate is arranged on the upper part of the wafer. This is because the wafer is on the upper side, and the diffusion plate side is gaseous from the bottom to the upper side. May be adopted, and they may be arranged with a predetermined gap in the lateral direction. In short, these arrangement relations are not limited to the upper and lower sides, but may be any arrangement as long as they face each other at a fixed interval.

The loading and unloading of wafers into and out of the ashing apparatus may be performed by any handling mechanism, and is not limited to the embodiment.

In this embodiment, one of the wafer mounting table and the diffusion plate is relatively moved in order to carry in the wafer, thereby securing a space for inserting the handling arm. But these are
At the same time, both parties may move up and down.

Further, if the belt transfer mechanism and the pusher or the like are used to feed the wafer to the wafer mounting table, the distance between the diffusion plate and the wafer mounting table may be small, and an enlarged space into which the handling arm or the like enters is unnecessary. Therefore, the vertical movement mechanism of the wafer mounting table or the diffusion plate is not essential.

In the embodiment, the case where the gas is injected is described. However, this may be simply performed by flowing the ozone + oxygen gas into the reaction space. Therefore, it is enough that it simply flows out.

Further, in the embodiment, the structure of the injection unit is a conical shape, a cylindrical shape, and a tubular shape. For example, a disc-shaped structure or a nozzle-like structure is used to supply ozone + gas. It may be injected or spilled,
Various shapes can be applied.

Therefore, the flat plate portion in this specification includes a flat portion formed by rotating a rod-shaped object so that its trajectory forms an even gas flow with the flat plate.

The cooler may be employed depending on the reaction conditions, and is not always necessary. In addition, the structure cites a case in which a refrigerant flows through a pipe. In this case, a double structure space in which a refrigerant flows directly may be provided in an injection unit, and various liquids and gases including water and cooling air may be provided. Further, cooling may be performed by a cooling metal or the like utilizing the Peltier effect or the like.

As the diffusion plate, an example in which a sintered alloy is used is given as one having uniform porous holes, but the porous material is not limited to metal, and various materials such as ceramics can be used. Of course.

Furthermore, the higher the temperature of the wafer during the ashing process, the faster the oxidation reaction speed, but this is related to the speed of loading / unloading the wafer, and is not necessarily set to a high value. Is also good. Furthermore, the reaction can be carried out at about room temperature or lower, even in view of the lifetime of ozone. Further, if the weight% of ozone can be set to a high value, a value lower than room temperature is possible. However, in the current apparatus, it is considered that the limit of the ozone generation weight% is around 10 to 13%.

In the examples, the resist is mainly described as the ashing target, but as described in the prior art, such an ashing process can be applied to various things such as removal of the solvent including removal of the ink and oxidation. Any material can be used as long as it can be removed.

Moreover, although the case where ozone is contained in oxygen gas is given, ozone is not limited to oxygen, and ozone is not limited to various gases that do not react with ozone, in particular, various inert gases such as N ₂ , Ar, and Ne. It can be contained and used.

EFFECTS OF THE INVENTION According to the present invention, the concentration of carbon dioxide in the exhaust gas generated during the ashing process is monitored, and the concentration of carbon dioxide is reduced to a change point or a certain value or less. The ashing end point can be predicted in advance and accurately because it is provided with the detection device that detects the above-mentioned point and the end point determination device that determines the ashing end point based on the signal from this detection device. Therefore, the transition time to the ashing process of the next wafer can be shortened, and the high-speed ashing process in the single wafer process can be performed. Also, there is little risk of damaging the wafer.

[Brief description of drawings]

FIG. 1 is a block diagram of an ashing apparatus according to an embodiment of the present invention, and FIG. 2 is a cross-sectional explanatory view showing an overall configuration including a wafer transfer mechanism, which is another similar embodiment.
3 (a) and 3 (b) are specific explanatory views of the electrostatic chuck in the wafer transfer mechanism. FIG. 3 (a) is a sectional view taken along line I-I of FIG. 3 (b), and FIG. A plan view thereof, FIG. 4 is an enlarged explanatory view of a reaction portion thereof, and FIG. 5 (a) is a view explaining a relationship between a reaction by oxygen atom radicals and transfer,
5 (b) and 5 (c) are views for explaining the relationship between the diffusion opening and the ashing state on the wafer surface, respectively.
The figure is a graph explaining the relationship between the decomposition half-life of ozone and the temperature of the diffusion opening. FIG. 7 is a graph for explaining the relationship between the gas flow rate and the ashing rate at a wafer surface temperature of 300 ° C. FIG. 8 is an ashing rate for the gap between the diffusion plate and the wafer surface at a wafer surface temperature of 300 ° C. FIG. 9 is an explanatory diagram showing the relationship between the gas temperature and the resist removal rate, and FIGS. 10 (a), (b),
(C), (d), (e) and (f) are explanatory diagrams of specific examples of the opening of the diffusion plate, respectively, and FIGS. 11 (a), (b) and
(C) and (d) are explanatory diagrams of a specific example of a gas cooling structure in an injection unit, respectively. FIG. 12 (a) is an explanatory diagram of a method of rotating a gas injection unit, and FIG. FIG. 13 is an explanatory diagram of an ashing effect when the wafer is not rotated, FIG. 14 is a block diagram of an embodiment of an ashing processing system for determining the end of the ashing process, and FIG. FIG. 16 is a graph illustrating the relationship between the concentration of ozone and the ashing speed, and FIG. 17 is a diagram illustrating a conventional ultraviolet ashing device. 1 ... Ashing system, 2,20 ... Ashing device,
3 ... Oxygen gas supply device, 3a ... Gas flow controller, 3b ... Ozone generator, 3c ... Oxygen supply source, 4 ... Exhaust device, 5 ... Lifting device, 6 ... Temperature controller, 7 ...... Gas analyzer, 8 …… End point determination / control device, 10a, 10b …… Electrostatic chuck, 21 …… Wafer mounting table, 21a, 206 …… Heating device, 22,22a, 22b …… Gas injection part, 23a, 23b …… loader / unloader section, 24a, 24b …… belt transport mechanism section, 25a, 25b …… transfer arm, 26a, 26b …… suction chuck, 28 …… wafer, 31 …… slit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keisuke Shikaki 1-26-26 Nishishinjuku, Shinjuku-ku, Tokyo Within Tokyo Electron Ltd. (72) Hiroyuki Sakai 1-226 Nishishinjuku, Shinjuku-ku, Tokyo No. Tokyo Electron Ltd. (56) Reference JP-A-52-20766 (JP, A) JP-A-54-32069 (JP, A) JP-A-51-35639 (JP, A) JP-A-56- 125841 (JP, A)

Claims (3)

(57) [Claims] 1. An ashing device which is provided as a wafer in contact with a space in which a gas containing ozone flows, and which oxidizes and removes a film attached to the surface of the wafer by a chemical reaction. Monitoring the concentration of carbon dioxide in the exhaust gas, a detection device for detecting a change point where the concentration of carbon dioxide starts to decrease, a detection device for detecting a point where the carbon dioxide has decreased to a certain value or less, each of the above An ashing device, comprising: an end point determination device that determines an ashing end point based on a signal from a detection device. 2. The ashing device according to claim 1, wherein the end point determination device has a comparator and a differentiating circuit. 3. The ashing device according to claim 1, wherein the end point determination device has a comparator and a peak detection circuit.