JP3437557B2 - Plasma ashing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma ashing method for removing a resist film applied on 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 is provided on the surface of a semiconductor substrate, and an insulating film, a semiconductor film or a metal film under the resist film is etched through the resist film. Is being done.

The resist film is removed from the surface of the substrate after the etching process is completed. The removal method is mainly a wet processing method using a chemical such as hydrogen peroxide or an organic solvent, and oxygen plasma. There is a dry processing method of ashing (ashing) the resist film using plasma of the reactive gas.

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

On the other hand, in the dry processing method, the C _X H _Y N _Z resist film coated on the substrate is reacted with radicals generated in the plasma of the reactive gas, mainly oxygen radicals, and the resist film is subjected to CO _Since it is removed by decomposing and vaporizing into ₂ and H ₂ O, it does not generate harmful substances to the human body unlike a wet processing method and does not contain impurities, and is suitable for fine processing of substrates.

An outline of an apparatus used in the dry processing method is as shown in FIG. 1, and a substrate (1) coated with a resist film is shown.
Is placed above the heating means (5) in the vacuum processing chamber (4) equipped with an inlet (2) for the reactive gas composed of a discharge tube and a vacuum exhaust port (3), and the inlet (2) The oxygen gas introduced from the reactive gas source (6) connected to or the reactive gas in which a small amount of CF ₄ , N ₂ or H ₂ is mixed therein is connected to the microwave power source (7) to generate a plasma ( Plasma generator consisting of 8) (9)
To generate plasma, and the radicals of oxygen radicals and other reactive gases react with the resist film on the heated substrate (1) to decompose and vaporize the resist film and the vacuum exhaust port (3)
To be removed by discharging with a vacuum pump (11).

[0007]

In the apparatus shown in FIG. 1, the reaction 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. It is called a stream type ashing device,
This device is advantageous in that charged particles do not collide with the substrate and the circuit pattern formed on the substrate is not damaged. However, recently, with the miniaturization of circuits, it has become more frequent to locally implant ions of impurities on the surface of the substrate by using the resist film coated on the substrate as a mask. In this case, as shown in FIG. 2, the resist film (10) used as a mask is irradiated with an ion beam and its surface layer portion (10a) is hardened and deteriorated, and the resist film (10) is ashed. Then, there is a drawback that it becomes difficult to remove.

The first object of the present invention is to provide a method of removing a resist film which has been hardened and changed in the 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 one vacuum processing chamber, a vacuum exhaust port is provided in the vacuum processing chamber, and heating means for heating the substrate .
Provided with a reactive gas inlet equipped with a plasma generator,
In the method of removing the resist film of the substrate by ashing with the plasma, front electrodes facing each other are provided on the front surface of the substrate with a space where plasma can be generated, and a narrow space where plasma is not generated on the back surface of the substrate. After the step of etching the surface layer of the resist film by connecting the rear electrode or the front electrode to a high frequency power source , the switching means is used in the same vacuum processing chamber.
The rear electrode or front electrode from the high frequency power source.
Then, the plasma generator is operated and the plasma of the reactive gas is used to ash the resist film on the substrate without using magnetron discharge to achieve the above object.

[0010]

In the plasma ashing method of the present invention, when the surface layer of the resist film coated on the surface of the substrate is cured and altered by the irradiation of the ion beam, the substrate is placed in the vacuum processing chamber and exhausted from the inlet. A reactive gas is flown into the mouth, and a high frequency power source is connected to the rear electrode facing the back surface of the substrate,
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 plasma is not generated between them, the substrate has almost the same potential as the rear electrode, and a high high-frequency potential from the high-frequency power source adds a negative potential. A plasma discharge occurs between the substrate and the front electrode at ground potential. Ions in the plasma are attracted by the potential of the substrate to move and collide with the front surface of the substrate. The resist film coated on the surface of the substrate is sputtered by collision of ions, and the surface layer portion of the resist film which has been hardened and modified can be physically peeled and removed.

When the removal of the hardened and altered portion of the surface layer is completed, the substrate is heated by the heating means, and the same vacuum processing chamber is used.
The switching means is used to switch the connection of the rear electrode from the high-frequency power source to the ground and activate the plasma generator.
As a result, the reactive gas introduced into the vacuum processing chamber from the inlet is excited by plasma, the radicals of the generated reactive gas chemically react with the resist film remaining on the substrate, and the remaining resist film is ashed from the substrate surface. Removed at high speed,
The decomposed / vaporized components are removed from the exhaust port.

On the other hand, when the surface of the substrate may be damaged, a high frequency power source is connected to the front electrode and the rear electrode is grounded. In this case, since the front electrode has a negative potential and the substrate has a ground potential, the ions in the plasma generated during that time collide gently so as not to damage the surface of the substrate, and the resist film on the substrate is loosely sputtered. It When the hardened and deteriorated portion of the surface of the resist film has been peeled off by sputtering, the substrate is heated by the heating means, the connection of the front electrode is switched from the high frequency power source to the ground, and the plasma generator is operated to move to the vacuum processing chamber. The remaining resist film is ashed and removed at high speed by the radicals of the reactive gas introduced.

According to the second aspect of the present invention, the radicals of the reactive gas flow to the front surface of the substrate through the through holes of the front electrode and uniformly ash the entire resist film.

[0014] In the present invention, the narrow gap between the back of the aft electrode and the substrate is set at intervals of, such for example 1mm, as plasma is not generated therebetween.

[0015]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIG. In the figure, reference numerals (1) to (9) and (11) refer to the same elements as those shown by the same reference numerals in FIG. 1, and the surface of the substrate (1) is different from that in FIG. Similarly resist film (10)
Is applied, and the resist film is irradiated with an ion beam.
It is the same as in the case of FIG. 1 that the surface layer (10a) of (10) has a hardened and altered layer.

In the embodiment of the present invention shown in FIG. 3, 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) and the front electrodes (13) facing each other are provided and the substrate is
The rear electrodes (16) facing each other with a narrow space (15) where plasma is not generated are provided on the back surface of (1), and these electrodes (13) (16)
Is configured to be 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 flat plate-shaped electrode having a large number of through holes (19) formed therein. 28m diameter
It is formed in a large-diameter through hole (19a) of m, and the rest is 1m in diameter.
It was formed in a small-diameter through hole (19b). About 1000 small-diameter through-holes (19b) were formed with a space of 1 mm. Further, in order to maintain the narrow space (15), for example, the space of 1 mm, a plurality of vertically movable pins (20) as shown in FIG. 5 which can be stopped by inserting the rear electrode (16) and projecting forward by 1 mm. Book establishment,
The substrate (1) was placed on the pins (20).

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 in} oxygen gas. , Or H ₂
Or a mixed gas of N ₂ gas and H ₂ gas is used.

Surface layer (10a) which has been hardened and altered by the apparatus shown in FIG.
The operation in the case of removing the resist film (10) having the structure from the substrate (1) by etching and ashing is as follows.

When the surface damage of the substrate (1) does not pose a problem, the inside of the vacuum processing chamber (4) is set to, for example, 10 ^-1 Torr.
The reactive gas from the gas source (6) to the exhaust port (3), for example, 5
Flowing at a rate of 000 SCCM, the front electrode (13) is connected to the ground (18) and the rear electrode (16) is connected to the high frequency power supply (17). Since the space (15) between the substrate (1) and the rear electrode (16) is narrow, the substrate (1) is at the same negative potential as the rear electrode (16), and the plasma of the reactive gas is generated in the space (14) with the front electrode (13). Are generated, and the ions in the plasma etch the resist film (10) on the surface of the substrate (1). The surface layer (10) of the resist film (10) which has been hardened and altered
When a) is finished is removed by etching, the substrate is heated (1) by, for example, to 200 ° C. the heating means (5), and switching means
The rear electrode (16) at a high frequency by switching the switch (55).
Rutotomoni is connected to ground (18) from connection with the wave power (17), to generate a plasma of reactive gas in the plasma generating part to put a microwave power source (7) of the plasma generator (9) (8) . Radicals of the reactive gas generated thereby , mainly oxygen radicals, remain on the substrate (1) in the resist film (1
By chemically reacting with 0), the resist film (10) is ashed and rapidly removed from the substrate (1).

[0021] When the substrate (1) are those susceptible to damage, switch (55) in front side electrode (13) a high-frequency power source (17)
And connect the rear electrode (16) to ground (18). As a result, a plasma of reactive gas is generated in the interval (14), but the ions in the plasma have a strong impact on the substrate (1), which is almost at ground potential, because the front electrode (13) has a negative potential. The board does not rush into the
The resist film (10) can be softly etched without damaging (1). When the surface layer (10a) of the resist film (10) which has been hardened and changed is removed by this etching, the switch (5
5) and connect the front electrode (13) to the ground (18),
Heat the (1) and activate the plasma generator (9) to
The resist film (10) remaining in (1) is rapidly removed by ashing.

The resist film (10) is applied to the front surface of the substrate (1), but in practice, it often wraps around the back surface of the substrate (1) as shown in FIG. Removal of the resist film was difficult with the conventional ashing equipment,
By providing the rear electrode (16) with a narrow space (15) from the substrate (1), reactive radicals such as oxygen radicals can be provided at this space.
The resist film on the back surface can be removed by ashing by going into (15).

A more specific embodiment of the present invention will be described with reference to FIGS. 7 to 9. In these drawings, reference numeral (4)
7) shows a frame-shaped machine body, and a vacuum processing chamber is provided above the machine body (47).
(4) is attached. A plasma generator (9) is provided on the side of the vacuum processing chamber (4), and a reactive gas source (6) is passed through the inside of the plasma generation device (9) into the vacuum processing chamber (4). (2) is provided with an inlet (2) of a reactive gas introduction pipe (41). Further, the substrate (1) is carried out into the vacuum processing chamber (4) through the valve (48) at a position which is turned by about 90 ° from the plasma generator (9) on the side of the vacuum processing chamber (4). A transfer chamber (49) for entering is provided, and a cassette chamber (21) is continuously provided in the transfer chamber (49). The cassette room
Inside the (21), there are provided two tables that can be individually raised and lowered by two sets of lifting rods (22) introduced from the outside, and accommodate a plurality of substrates on each table so that they can be taken in and out sideways. Shelf-shaped cassette case (23a) (23b) as shown in FIG.
Will be posted.

A substrate to be ashed is housed in one of the cassette cases (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). By means of 24), the lower case of the cassette case (23a) is sent to a fixed position in the vacuum processing chamber (4) via the valve (48) by turning and expanding and contracting of the transfer device (24). In the vacuum processing chamber (4) in, while ashing process on the substrate, the valve (4 8) is closed, the transport device
(24) stands by in the transfer room (49). When the ashing process is completed, the transfer device (24) is opened again and the valve ( 4
8 ) advance into the vacuum processing chamber (4), load the ashed substrate and return to the transfer chamber (49), and the substrate on the transfer device (24) is another cassette case (23b) It is carried in by the extension of the carrying device (24) and is housed in a predetermined position by raising the cassette case (23b). When the processed substrate is stored in the other cassette case (23b), the next substrate is carried out from the other cassette case (23a) to the vacuum processing chamber (4) repeatedly, and the substrate ashing process is sequentially performed. Done.

A vacuum exhaust pipe (50) equipped with a throttle valve (25) is connected below the vacuum processing chamber (4), and the vacuum processing chamber (4) is evacuated to a vacuum 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.

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

Details of the plasma generator (9) are shown in FIG.
And as shown in FIG. 13, 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 microwaves to generate plasma, and the excited radicals of the 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 so as to prevent the casing from becoming hot due to plasma discharge. At a position facing the end of the quartz tube (41a) of the casing (9a), a mercury lamp (3
0) is provided, and the mercury lamp (30) is turned on at the start of plasma discharge to photoionize the reactive gas in the quartz tube (41a) so that the microwave discharge can be started quickly. Further, a slide block (32) that advances and retreats by turning the adjusting screw (31) extending to the outside through the casing (9a) is provided at the end of the inside of the microwave waveguide (27), and the plasma discharge is caused by the reciprocation. I tried to match.

The details of the inside of the vacuum processing chamber (4) are as shown in FIG. 14, and the vacuum processing chamber (4) is formed by a vertical empty chamber, and a substrate (1 ) To and from the transfer chamber (49), and a reactive gas introduction pipe (41) at a position rotated by 90 ° from the opening (33).
Is formed with an opening. And the vacuum processing chamber (4)
A circular recess (35a) supported on the bottom surface of the vacuum processing chamber (4) by a plurality of polytetrafluoroethylene insulating material supports (34) is provided slightly below the opening (33).
The holder (35) made of Al ₂ O ₃ was provided, and the heating means (5) composed of a disc-shaped sheathed heater was housed in the recess (35a). The upper surface of the heating means (5) is covered with an insulating plate (36) made of Al ₂ O ₃ , and the periphery of the upper surface of the heating means (5) is a ring (37) made of SiO ₂ .
To be covered with. Further, the disk-shaped heating means (5) and the holder (35) are provided with a through hole (38) through which these are inserted vertically.
There are three quartz pins (4) which are provided at an interval of ° and are moved up and down from below the holder (35) by an elevating device (39).
0) is inserted into each of the through holes 38. The substrate is then transferred into the vacuum processing chamber (4) through the opening (33) by the transfer device (24).
When the (1) is carried in, the heating means (5) is inserted and the pins (40) that rise are supported so that the substrate (1) is lifted, and the transfer device (24) is pushed through the opening (33). After the withdrawal, each pin (40) descends and the substrate (1) is positioned 1 to 2 mm above the upper surface of the heating means (5) for etching, ashing and ashing the resist film of the substrate (1). Is heated. When the ashing of the substrate (1) is finished, the pins (40) lift the substrate (1) above the heating means (5) again,
When the transfer device (24) enters between the heating means (5) and the substrate (1), each pin (40) descends, and the substrate is in the process of descending.
(1) is held by the transfer device (24) and the opening (3) of the vacuum processing chamber (4) is held.
Carried out from 3).

The lifting device (39) is a lifting rod extending from the bottom surface of the vacuum processing chamber (4) to the outside through a sealing device (59).
And (39a), and attached elevating plate (39 b) at the upper end of該昇Fu杆(39a), connecting plate attached to the lower end of該昇Fu杆(39 a) (39c), and said connecting plate (39c) Equipped with a screw shaft (39d) that is screwed into the vacuum processing chamber (4) and is mounted on a fixed plate (42) outside the vacuum processing chamber (4).
A gear whose rotation of 3) is integral with the screw shaft (39d) supported by the plate (42) via its output shaft (44) and idle gear (45).
Once transferred to (39e), to rotate the screw shaft (39d) is, the connecting plate (39c) and the lift rod a (39a) is raised or lowered, the lifting plate (39 b) is a pin along with this (40 ) And go up and down. The pin (40) has its root at the hole (39 b ) of the lifting plate (39 b ).
It was inserted into f) and fixed with a spring (39g).

An opening (33) in the vacuum processing chamber (4) and a gas introduction pipe
A step portion (46) projecting inward is provided between the inlet (2) of (41) and a large-diameter through hole is formed in the center portion of the step portion (46).
(19a) and a circular flat plate front electrode (13) having a small diameter through hole (19b) around it is placed via an insulating material (52), and the inside of the vacuum processing chamber (4) is the front electrode. It is divided into two chambers (53) and (54) by (13). The front electrode (13) is a vacuum processing chamber.
It is selectively connected to the high frequency power supply (17) or the ground (18) via the switch (55) outside 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 connected to the substrate (1) by energization thereof. The heating means (5) has one support (3
4) Insert the conductive shaft (58) from the outside of the vacuum processing chamber (4) through the inside, and connect the conductive shaft (58) through the switch (55) to the high frequency power supply (17) or ground (18). The heating means (5) acts as a rear electrode (16) by selectively connecting to the.

[0032]

As described above, according to the present invention, 1
A substrate coated with a resist film is provided in one vacuum processing chamber, and a vacuum exhaust port, a heating means for heating the substrate, and a reactive gas introduction port having a plasma generator are provided in the vacuum processing chamber. In the method of removing the resist film on the substrate by ashing with the plasma, front electrodes facing each other are provided on the front surface of the substrate with a space where plasma can be generated, and a narrow space where plasma is not generated on the back surface of the substrate. Existing rear electrodes, and rear electrodes or front
After the step of connecting the electrode to a high frequency power source and finishing the step of etching the surface layer of the resist film, the switching means is used to move to the rear electrode.
Or switch the connection of the front electrode from the high frequency power supply to ground
By operating the plasma generator to ash the resist film on the substrate by the plasma of the reactive gas without using magnetron discharge, it is possible to cleanly remove the resist film having the hardened and altered surface layer on the substrate, By 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, there is an effect that the substrate is prevented from being damaged and ashing can be performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional diagram of a conventional ashing device.

FIG. 2 is an enlarged cross-sectional view of a resist film applied on a substrate.

FIG. 3 is a cross-sectional diagram of an embodiment of the present invention.

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

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

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

FIG. 7 is a concrete side view showing a part of the apparatus of the present invention cut away.

8 is a cutaway side view taken along the line VIII-VIII in FIG.

FIG. 9 is a cutaway plan view taken along line IX-IX in FIG. 7.

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

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

FIG. 12 is an enlarged cutaway side view of the plasma generator.

13 is a right side view of FIG.

FIG. 14 is an enlarged cutaway side view of the vacuum processing chamber.

[Explanation of symbols]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-202521 (JP, A) JP 63-114210 (JP, A) JP 62-136573 (JP, A) JP 63- 224232 (JP, A) JP-A-61-292920 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/3065 G03F 7/42 H01L 21/027

Claims (2)

(57) [Claims] 1. A reactive gas introduction system comprising a substrate coated with a resist film in one vacuum processing chamber, a vacuum exhaust port, heating means for heating the substrate, and a plasma generator in the vacuum processing chamber. In the method of removing the resist film of the substrate by ashing with the plasma, the front surface of the substrate is provided with front electrodes facing each other with a space where plasma can be generated, and the plasma is formed on the back surface of the substrate. the rear electrode opposing provided exist a narrow interval but does not occur, connecting the rear electrode or front electrode to a high frequency power source, after the surface of the resist film was finished etching, the same vacuum treatment
In the back room, using the switching means,
A plasma ashing method, characterized in that the connection is switched from a high frequency power supply to ground, and a plasma generator is operated to ash the resist film on the substrate by plasma of the reactive gas without using magnetron discharge. 2. The plasma ashing method according to claim 1, wherein the front electrode provided facing the front surface of the substrate is formed of a flat plate having a large number of through holes.