JPH1145873A - Plasma-ashing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the ashing of a resist film whose surface layer is hardened and converted, and to attain the ashing of the resist film without giving damages to a substrate. SOLUTION: A substrate 1 to which a resist film is applied is provided in a evacuated processing chamber 4, and a vacuum air discharge outlet and a reactive gas inlet port equipped with a heating means for heating the substrate and a plasma-generating device 9 are provided in the vacuum-processing chamber. This is a method for removing the resist film of the substrate by operating the ashing of the resist film by plasma. A front electrode 13 is provided on the front face of the substrate so as to be faced with an interval in which plasma can be generated, and a rear electrode 16 is provided on the back face of the substrate so as to be faced with an interval in which plasma does not generate. Then, one of the electrodes is connected with a high-frequency power source, the other electrode is connected with ground, the etching of the surface layer of the resist film is carried out, both the electrodes are grounded, the generator is operated, and the ashing of the resist film on the substrate is attained by plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a plasma ashing method for removing a resist film applied to a semiconductor substrate by ashing (ashing) using plasma.

[0002]

2. Description of the Related Art In order to process a fine integrated circuit, a resist film having a circuit pattern formed thereon is provided on a surface of a semiconductor substrate, and an insulating film, a semiconductor film or a metal film thereunder is etched through the resist film. That is being done.

[0003] The resist film is removed from the substrate surface after the etching process is completed. The removal method mainly includes a wet processing method using a chemical such as hydrogen peroxide and an organic solvent, and an oxygen plasma. There is a dry processing method in which the resist film is ashed (ashed) by using plasma of a reactive gas to be applied.

Many of the chemicals used in the wet processing method are harmful to the human body, and it is troublesome to pay attention to maintaining the safety of the removing operation and preventing pollution of the waste liquid. In addition, the chemicals used contain some impurities, which cause defects or contamination of the pattern of the semiconductor circuit, and are not suitable for fine processing of VLSI.

On the other hand, in the dry processing method, radicals generated in the plasma of the reactive gas, mainly oxygen radicals, are reacted with the C _X H _Y N _Z resist film applied to the substrate, and the resist film is CO 2 _Since it is removed by decomposition and vaporization into H ₂ O and H ₂ O, there is no generation of harmful substances to the human body as in a wet processing method, and it is suitable for fine processing of a substrate because it contains no impurities.

The apparatus used in the dry processing method is schematically shown in FIG. 1, and a substrate (1) coated with a resist film is used.
Is placed above a heating means (5) in a vacuum processing chamber (4) provided with a reactive gas inlet (2) constituted by a discharge tube and a vacuum exhaust port (3), and the inlet (2) Oxygen gas introduced from a reactive gas source (6) connected thereto or a reactive gas containing a small amount of CF ₄ , N ₂ , or H ₂ mixed therein with a plasma generator (7) connected to a microwave power supply (7) Plasma generator (9) consisting of (8)
By the plasma, oxygen radicals and other reactive gas radicals are reacted with the resist film on the heated substrate (1), the resist film is decomposed and vaporized, and the vacuum exhaust port (3)
And is removed by discharging with a vacuum pump (11).

[0007]

In the apparatus shown in FIG. 1, the reactant gas flows from above the vacuum processing chamber along the surface of the substrate and is discharged from a vacuum exhaust port provided below the vacuum processing chamber, so that the apparatus is down. It is called a stream type ashing device,
This device is advantageous in that charged particles do not collide with the substrate and do not damage circuit patterns formed on the substrate. In recent years, however, the use of a resist film applied to a substrate as a mask and local ion implantation of impurities on the surface of the substrate has been frequently performed with miniaturization of circuits. In this case, as can be seen in FIG. 2, the resist film (10) used as a mask is irradiated with an ion beam and its surface layer (10a) is cured and deteriorated, and the resist film (10) is ashed. There is a drawback that it is difficult to remove it.

It is a first object of the present invention to provide a method for removing a hardened and deteriorated resist film on a surface layer by ashing.
The second purpose is to remove the resist film by ashing without damaging the substrate.

[0009]

According to the present invention, a substrate coated with a resist film is provided in a vacuum processing chamber, and a vacuum exhaust port, heating means for heating the substrate, and a plasma generator are provided in the vacuum processing chamber. A reactive gas introduction port provided therein, wherein the resist film on the substrate is removed by ashing with the plasma, and the front electrode is opposed to the front surface of the substrate at an interval where plasma can be generated. And a rear electrode opposed to the back surface of the substrate at a small interval where no plasma is generated, and one of the two electrodes is connected to a high-frequency power source and the other is connected to ground to etch the surface layer of the resist film. After completion of the process, both electrodes are connected to the ground, and the plasma generator is operated to ashing the resist film on the substrate with the plasma of the reactive gas, thereby forming an upper electrode. And so as to achieve the purpose of. After the step of connecting the front electrode to a high-frequency power source and connecting the rear electrode to ground and etching the surface layer of the resist film is completed, both electrodes are connected to ground and the plasma generator is operated to activate the reactive gas. Ashing a resist film on a substrate by gas plasma can perform ashing without damaging the substrate. By forming the front electrode provided to face the front surface of the substrate with a plate-like electrode having a large number of holes, active radicals of the reactive gas introduced from the inlet through the holes are formed. The resist film can uniformly reach the substrate surface, and the resist film is uniformly removed by ashing. The distance between the substrate and the rear electrode behind the substrate is set to a narrow distance of, for example, 1 mm at which no plasma is generated.

[0010]

When the surface layer of the resist film applied on the surface of the substrate is cured and deteriorated by the irradiation of the ion beam, the substrate is placed in a vacuum processing chamber, and a reactive gas is supplied from the inlet to the exhaust port. A high-frequency power source is connected to a rear electrode facing the rear surface of the substrate, and the front electrode on the front surface of the substrate is grounded.
Since the distance between the substrate and the rear electrode is set so narrow that no plasma is generated between the substrate and the substrate, the substrate has almost the same potential as the rear electrode. Plasma discharge occurs between the substrate and the front electrode at ground potential. The ions in the plasma move due to the potential of the substrate and collide with the front surface of the substrate. The resist film applied to the surface of the substrate is sputtered by ion bombardment, and the hardened and deteriorated surface layer of the resist film can be physically peeled off.

When the hardened and deteriorated portion of the surface layer has been removed, the substrate is heated by the heating means, the connection of the rear electrode is switched from the high frequency power source to the ground, and the plasma generator is operated. As a result, the reactive gas introduced from the inlet into the vacuum processing chamber is excited by plasma, and the radicals of the generated reactive gas chemically react with the resist film remaining on the substrate, and the remaining resist film is ashed to the substrate surface. At high speed, and its decomposition and vaporization components are removed from the exhaust port.

When the surface of the substrate is likely to be damaged, a high frequency power supply is connected to the front electrode and the rear electrode is grounded. In this case, the front electrode is at a negative potential, and the substrate is at the ground potential, so that ions in the plasma generated during the collision gently collide so as not to damage the surface of the substrate, and the resist film of the substrate is sputtered loosely. You. When the hardened and deteriorated portion of the surface of the resist film is peeled off by sputtering, the substrate is heated by a heating means, the connection of the front electrode is switched from the high frequency power supply to the ground, and the plasma generator is operated, and the vacuum processing chamber is opened. The remaining resist film is ashed at high speed and removed by the radicals of the introduced reactive gas.

The radicals of the reactive gas flow to the front surface of the substrate through the through holes of the front electrode, and uniformly ashing the entire resist film.

The narrow distance between the rear electrode and the rear surface of the substrate is set to, for example, 1 mm so that no plasma is generated therebetween.

[0015]

An embodiment of the present invention will be described with reference to FIG. In the figure, reference numerals (1) to (9) and (11) denote FIG.
Nominate the same thing as shown by the same reference
A resist film (10) is applied to the surface of (1) in the same manner as in FIG.
A hardened and deteriorated layer is formed on the surface layer (10a) of (0) as in the case of FIG.

The embodiment of the present invention shown in FIG. 3 has, in addition to the configuration of FIG. 1, an interval (1) at which plasma can be generated on the front surface of the substrate (1).
4) providing a front electrode (13) opposed to the substrate and
On the back of (1), a rear electrode (16) opposed to the electrode with a small interval (15) where plasma is not generated is provided, and these electrodes (13) (16)
Is selectively connected to a 200 W, 13.56 MHz high frequency power supply (17) and a ground (18). Both electrodes (13) (16)
Are provided at intervals of, for example, 20 mm, and the inside of the vacuum processing chamber (4) is adjusted to, for example, several Torr to 10 ^-2 Torr.

In this case, as shown in FIG. 4, the front electrode (13) is composed of a plate-like electrode having a large number of through holes (19) formed therein. Thing 28m in diameter
m with a large diameter through hole (19a) and the remaining one is 1m in diameter.
It was formed in a small diameter through hole (19b). About 1,000 small-diameter through holes (19b) were formed at intervals of 1 mm. Also, in order to maintain the narrow interval (15), for example, an interval of 1 mm, a plurality of pins (20) as shown in FIG. 5 that can be stopped by being inserted into the rear electrode (16) and protruding 1 mm forward are provided, The pin (20)
The substrate (1) was placed on the substrate.

The reactive gas sent from the gas source (6) into the vacuum processing chamber (4) is oxygen gas, N ₂ gas, CF ₄ gas, H ₂ gas, or a small amount of CF ₄ , N ₂ gas in oxygen gas. Or H ₂
Or a mixed gas of N ₂ gas and H ₂ gas is used.

Surface layer (10a) hardened and deteriorated by the apparatus shown in FIG.
The operation for removing the resist film (10) having the above from the substrate (1) by ashing will be described as follows.

When the damage on the surface of the substrate (1) is not a serious problem, the inside of the vacuum processing chamber (4) is kept at, for example, 10 ^-1 Torr.
And a reactive gas, for example, 5 from the gas source (6) to the exhaust port (3).
Flow at a rate of 000 SCCM, and connect the front electrode (13) to the ground (18) and connect the rear electrode (16) to the high frequency power supply (17). Since the distance between the substrate (1) and the rear electrode (16) (15) is narrow, the substrate (1) has the same negative potential as the rear electrode (16), and the reactive gas plasma is applied to the distance (14) from the front electrode (13). Are generated, and ions in the plasma etch the resist film (10) on the surface of the substrate (1). The cured and deteriorated surface layer of the resist film (10) (10
When the a) is removed by etching, the substrate (1) is heated to, for example, 200 ° C. by the heating means (5), and the rear electrode (1) is heated.
6) is connected to the earth (18) and the plasma generator (9)
The microwave power supply (7) is turned on to generate a plasma of a reactive gas in the plasma generating section (8). Oxygen radicals, mainly the radicals of the reactive gas generated by this,
(1) It chemically reacts with the resist film (10) remaining on the resist film, and the resist film (10) is ashed and rapidly removed from the substrate (1).

When the substrate (1) is easily damaged, the switch (55) is switched to connect the front electrode (13) to the high frequency power supply (17) and to connect the rear electrode (16) to the ground (18). Connect to As a result, a plasma of the reactive gas is generated in the interval (14), and the ions in the plasma are strongly impacted on the substrate (1) almost at the ground potential because the front electrode (13) has a negative potential. The resist film (10) is soft without damaging the substrate (1) because it collides loosely without entering
Can be etched. With this etching, resist film (10)
When the hardened and deteriorated surface layer (10a) is peeled off, the front electrode (13) is connected to the ground (18), the substrate (1) is heated, the plasma generator (9) is operated, and the substrate (1) Remaining resist film
(10) is rapidly removed by ashing.

The resist film (10) is applied to the front surface of the substrate (1). However, in practice, as shown in FIG. Although removal of the resist film was difficult with a conventional ashing device,
By providing the rear electrode (16) at a small distance (15) from the substrate (1), reactive radicals such as oxygen radicals
(15), the resist film on the rear surface can be removed by ashing.

A more specific embodiment of the present invention will be described with reference to FIGS. 7 to 9.
7) shows a frame-shaped body, and a vacuum processing chamber is provided above the body (47).
(4) is attached. A plasma generator (9) is provided beside the vacuum processing chamber (4), and a reactive gas source (6) passes through the inside of the plasma generator (9) into the vacuum processing chamber (4). ) Is provided with an inlet (2) of a reactive gas inlet pipe (41) communicating therewith. Further, the substrate (1) is unloaded into the vacuum processing chamber (4) via the valve (48) at a position turned about 90 ° from the plasma generator (9) beside the vacuum processing chamber (4). A transfer room (49) is provided therein, and a cassette room (21) is further provided in the transfer room (49). The cassette room
(21) is provided with two tables which are individually raised and lowered by two sets of lifting rods (22) introduced from the outside, and accommodates a plurality of substrates on each table so that they can be taken in and out from the side. The shelf-shaped cassette case (23a) (23b) as shown in FIG.
Is placed.

A substrate to be ashed is stored in one cassette case (23a), and the substrate is lowered and a frog arm-shaped transfer device (for example, as shown in FIG. 11) provided in the transfer chamber (49). According to 24), the cassette case (23a) is sent to the fixed position in the vacuum processing chamber (4) via the valve (48) by the rotation and expansion and contraction of the transfer device (24). In the vacuum processing chamber (4), the valve (49) is closed during the ashing process on the substrate, and the transfer device is
(24) waits in the transfer room (49). When the ashing process is completed, the transfer device (24) is opened again with the valve (1) opened.
9), enters the vacuum processing chamber (4), returns the ashed substrate to the transfer chamber (49), and transfers the substrate on the transfer device (24) to another cassette case (23b). The cassette device (24b) is carried into the inside by extension of the transport device (24), and is housed at a predetermined position by raising the cassette case (23b). When the processed substrate is stored in another cassette case (23b), the next substrate is transported from the other cassette case (23a) to the vacuum processing chamber (4), and the substrate ashing process is sequentially performed. Done.

A vacuum exhaust pipe (50) having a throttle valve (25) is connected below the vacuum processing chamber (4), and the inside of the vacuum processing chamber (4) is evacuated by a vacuum pump (11). However, the middle of the vacuum exhaust pipe (50) is branched and connected to the cassette chamber (21),
The inside of the cassette chamber (21) was also evacuated to a vacuum.

In FIGS. 7 and 8, reference numeral (26) indicates a microwave oscillating device, and the generated microwave is introduced into the plasma generating device (9) through the waveguide (27). .

The details of the plasma generator (9) are shown in FIG.
13, and the waveguide (27) is provided so as to intersect with the quartz tube (41a) in the middle of the reactive gas introduction pipe (41) connected to the reactive gas source (6), At the intersection, the reactive gas is excited by the microwave to generate plasma, and radicals of the excited reactive element are sent to the vacuum processing chamber (4). The casing (9a) of the plasma generator (9) is provided with a passage (28) through which cooling water circulates to prevent the casing from becoming hot due to plasma discharge. A mercury lamp (3) is placed on the casing (9a) at a position facing the end of the quartz tube (41a) through a quartz window (29).
0), the mercury lamp (30) was turned on at the start of the plasma discharge to perform photoionization of the reactive gas in the quartz tube (41a), so that the microwave discharge could be started quickly. A slide block (32) is provided at the end of the microwave waveguide (27) at the end of the microwave (27) so as to advance and retreat by turning an adjustment screw (31) extending to the outside through the casing (9a). Was made to match.

The details of the inside of the vacuum processing chamber (4) are as shown in FIG. 14, which is formed by a vertical cylindrical chamber, and the substrate (1) is provided above the side thereof with the transfer chamber (49). And an opening (33) for taking in and out between the opening (33) and 90 ° from the opening (33).
An opening is formed at the pivoted position with the end of the reactive gas introduction pipe (41). A little below the opening (33) of the vacuum processing chamber (4), it was supported on the bottom surface of the vacuum processing chamber (4) by a plurality of polytetrafluoroethylene insulating material supports (34). Al ₂ O ₃ holder with circular recess (35a)
(35) was provided, and a heating means (5) composed of a disk-shaped sheathed heater was accommodated in the recess (35a). The heating means
(5) of the upper surface is covered with a made of Al ₂ O ₃ insulating plate (36), heating means
The periphery of the upper surface of (5) was covered with a ring (37) made of SiO ₂ . Further, three through holes (38) for vertically inserting these into the disk-shaped heating means (5) and the holder (35) are provided at intervals of 120 °, and a lifting device is provided from behind the holder (35). The three quartz pins (40), which move up and down by (39), are
(38) is inserted respectively. And opened into the vacuum processing chamber (4)
When the substrate (1) is carried in by the transfer device (24) via (33), the pins (40) that are inserted and raised by the heating means (5) are lifted from the transfer device (24). After the transfer device (24) withdraws from the opening (33), the pins (40) are lowered and the substrate (1) is moved upward by 1 to 2 mm from the upper surface of the heating means (5).
And heating for etching, ashing, and ashing of the resist film on the substrate (1) is performed. When the ashing of the substrate (1) is completed, the substrate (1) is lifted again above the heating means (5) by the pins (40) and transported between the heating means (5) and the substrate (1). When the device (24) enters, each pin (40) descends, and during the descent, the substrate (1) is held by the transfer device (24) and carried out from the opening (33) of the vacuum processing chamber (4). It is.

The elevating device (39) is an elevating rod extending from the bottom surface of the vacuum processing chamber (4) to the outside via a sealing device (59).
(39a), an elevating plate (39b) attached to the upper end of the elevating rod (39a), a connecting plate (39c) attached to the lower end of the elevating rod (39b), and the connecting plate (39c). It has a screw shaft (39d) for screwing, and a synchronous motor (4) attached to a fixed plate (42) outside the vacuum processing chamber (4).
The rotation of 3) is a gear integrated with the screw shaft (39d) supported on the plate (42) via its output shaft (44) and idle gear (45).
(39e), the screw shaft (39d) rotates to raise or lower the connecting plate (39c) and the elevating rod (39a), and accordingly the elevating plate (39c) moves the pin (40) It goes up and down with. The pin (40) has its root at the hole (39) of the lifting plate (39c).
f) and fixed with a spring (39 g).

Opening (33) in vacuum processing chamber (4) and gas inlet pipe
An inwardly protruding step (46) is provided between the inlet (2) of (41) and a large-diameter through hole in the center of the step (46).
(19a) and a circular flat front electrode (13) having a small-diameter through hole (19b) therearound is placed via an insulating material (52), and the inside of the vacuum processing chamber (4) is the front electrode. (13) is divided into two rooms (53) and (54). The front electrode (13) is a vacuum processing chamber.
It is selectively connected to a high frequency power supply (17) or a ground (18) via an external switch (55) of (4).

The heating means (5) is connected to wirings (56) and (57) from a power source outside the vacuum processing chamber (4), and the heating means (5) is energized so that the substrate (1) The heating means (5) generates heat due to the heating of the heating means (5).
4) penetrate the inside and introduce and connect the conductive shaft (58) from the outside of the vacuum processing chamber (4), and connect the conductive shaft (58) to the high frequency power supply (17) or the ground (18) via the switch (55). And the heating means (5) acts as a rear electrode (16).

[0032]

As described above, according to the present invention, the front electrode is provided on the front surface of the substrate to be ashed with a space capable of generating plasma, and the narrow space where plasma is not generated is formed on the back surface of the substrate. After the process of etching the surface layer of the resist film by connecting one of the electrodes to the high-frequency power source and connecting the other to the ground and connecting the other electrode to the ground, a plasma generator is provided. Is operated to ashing the resist film on the substrate with the plasma of the reactive gas, so that the resist film having a hardened and deteriorated surface layer on the substrate can be removed cleanly, and the front electrode is connected to a high-frequency power source and By connecting the back electrode to the ground and etching the surface layer of the resist film, ashing can be performed while preventing damage to the substrate. A.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conventional ashing device.

FIG. 2 is an enlarged sectional view of a resist film applied to a substrate.

FIG. 3 is a sectional view of an embodiment of the present invention.

FIG. 4 is an enlarged plan view of the front electrode of FIG. 3;

FIG. 5 is a perspective view showing a holding state of the substrate of FIG. 3;

FIG. 6 is an enlarged sectional view showing a coated state of a resist film on the entire substrate.

FIG. 7 is a specific side view in which a part of the device of the present invention is cut.

8 is a sectional side view taken along the line VIII-VIII in FIG. 7;

9 is a cut-away plan view along the line IX-IX in FIG. 7;

FIG. 10 is a perspective view of a cassette case.

FIG. 11 is an enlarged plan view of a main part of the transfer device.

FIG. 12 is an enlarged sectional side view of a plasma generator.

FIG. 13 is a right side view of FIG.

FIG. 14 is an enlarged sectional side view of a vacuum processing chamber.

[Explanation of symbols]

(1) ... substrate, (2) ... inlet for reactive gas, (3) ... outlet
(4) ... vacuum processing chamber, (5) ... heating means, (9) ... plasma generator, (10) ... resist film, (10a) ... hardened and deteriorated surface layer,
(13) ... front electrode, (14) ... spacing, (15) ... narrow spacing, (16) ...
Rear electrode, (17) high frequency power supply, (18) earth, (19) through hole,

Claims (3)

[Claims] A substrate coated with a resist film is provided in a vacuum processing chamber, and the vacuum processing chamber has a vacuum exhaust port, a heating means for heating the substrate, and a reactive gas inlet provided with a plasma generator. In the method of removing the resist film of the substrate by ashing with the plasma, a front electrode opposed to the front surface of the substrate at an interval where plasma can be generated is provided, and a front electrode is provided on the rear surface of the substrate. After providing a rear electrode facing at a narrow interval where plasma is not generated, one of the two electrodes is connected to a high-frequency power source and the other is connected to the ground, and after the step of etching the surface layer of the resist film is completed, the both electrodes are A plasma ashing method comprising: connecting a substrate to ground and operating a plasma generator to ashing a resist film on a substrate with plasma of the reactive gas. 2. After the step of connecting the front electrode to a high-frequency power source and connecting the rear electrode to ground and etching the resist film is completed, both electrodes are connected to ground and the plasma generator is operated. 2. The plasma ashing method according to claim 1, wherein the resist film on the substrate is ashed by the plasma of the reactive gas. 3. The plasma ashing method according to claim 1, wherein the front electrode provided to face the front surface of the substrate is a flat plate having a large number of through holes.