JPH02177421A - Wafer periphery aligner - Google Patents

Abstract

PURPOSE:To obtain a device which can elevate productivity in exposure of wafer periphery by shortening exposure time and in which bubbling of resist does not occur by providing additionally a cooling mechanism, which cools a wafer, a second rotary stage, and a second light irradiation mechanism, which exposes the periphery of the water placed thereon at intensive illuminance. CONSTITUTION:This is equipped with a first rotary stage 17, where a wafer W to which resist is applied is placed, a temperature control mechanism 71, which is provided in the first rotary stage 17, a first light irradiation mechanism, which consists of a light guide fiber 16, for exposing the periphery Wp of the wafer W placed on the first rotary stage 17, and a light source lamp 11, a second rotary stage 27, where the wafer W which was exposed in the first rotary stage 17 is placed, a second light irradiation mechanism, which consists of a light guide fiber 26, for exposing the periphery Wp of the wafer W placed thereon at illuminance more intensive than the pivot light irradiation mechanism, and a light source lamp 21, and a cooling mechanism 30, which cools the wafer W while the wafer W which was exposed in the first rotary stage 17 is transferred to a second rotary stage 27.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention is applicable to semiconductor substrates such as silicon wafers,
Alternatively, it relates to wafer peripheral exposure for removing unnecessary resist in the peripheral area of a resist coated on a substrate such as a dielectric, metal, or insulator in a developing process.

[Conventional technology]

In the manufacturing process of ICs, LSIs, etc., when forming fine patterns, a resist is applied to the surface of a silicon wafer, etc., and then exposed and developed to form a resist pattern. Processing such as ion implantation, etching, and lift-off is performed using the pattern as a mask.

Usually, resist is applied by a spin code method. In the spin code method, resist is poured onto the center of the wafer surface, the wafer is rotated, and the resist is applied to the wafer surface using centrifugal force. However, when this spin code method is used, the resist sometimes protrudes from the periphery of the wafer and wraps around the back side of the wafer.

FIG. 3 is a partial cross-sectional view of the wafer showing the resist that has gone around to the back side of the wafer, where W is the wafer, Wp is the periphery of the wafer, Ra is the resist in the pattern forming area, and Rh
Rc shows the resist on the surface of the peripheral part Wp of the wafer, and Rc shows the resist that has gone around from the edge of the wafer W to the back side.

FIG. 4 is a diagram showing the shape of a circuit pattern exposed on a wafer. One area indicated by 2 corresponds to one circuit pattern. In most cases, circuit patterns cannot be drawn correctly on the periphery of the wafer, and even if they can be drawn, the yield is poor.Therefore, the resist on the surface of the wafer's periphery is actually unnecessary resist.

The presence of unnecessary resist that has spread from such edges to the back side of the wafer's periphery and on the surface of the wafer's periphery causes the following problems, namely:
Wafers coated with resist are transported through various processing steps and in various ways. At this time, the periphery of the wafer may be mechanically grasped and held, or the periphery of the wafer may be held in place. It may rub against the wall of the storage container. At this time, if unnecessary resist from the periphery of the wafer comes off and adheres to the pattern forming area of the wafer, correct pattern formation becomes impossible and the yield decreases.

Unnecessary resist on the periphery of the wafer becomes "dust" and reduces yield, which is a serious problem especially now that integrated circuits are becoming more sophisticated and smaller.

Therefore, as a technique for removing such unnecessary resist from the periphery of the wafer, a technique has been put into practical use in which a solvent is sprayed from the back surface of the periphery of the wafer to dissolve and remove the unnecessary resist using a solvent injection method. However, with this method, although the resist RC in the protruding portion shown in FIG. Even if the solvent is sprayed from the surface of the
Not only does this cause problems with solvent splashes, but also the unnecessary resist Rb on the peripheral surface of the wafer and the resist (Ra) in the pattern forming area, which is a necessary resist as a mask layer for later etching and ion implantation, etc. It is not possible to remove only unnecessary resist with sharp border areas and good controllability.

Therefore, recently, a wafer circumferential 122n light method has been used in which, in addition to the exposure process for pattern formation, the wafer is exposed separately in order to remove unnecessary resist on the periphery of the wafer in a development process. In this wafer peripheral exposure method, the wafer coated with resist is rotated and light guided by four guide fibers is irradiated onto the wafer's periphery, thereby circumferentially exposing the wafer's periphery. .

[Technical Problems to be Solved by the Invention] When a resist is applied by the above-described spin code method, the film thickness at the periphery of the wafer is thicker than at the center, and may be about 3 to 5 μm. In order to expose such a thick resist to light and remove it in a development process, a certain amount of exposure on the plate is required. The amount of exposure is the product of illuminance and time, so in order to increase the amount of exposure, either increase the illuminance or lengthen the exposure time.

Here, in order to increase productivity, the above-mentioned exposure time is required to be shortened, and the amount of exposure cannot be increased by lengthening the exposure time.

On the other hand, however, when attempting to increase the illuminance to obtain a required amount of exposure above a certain level, the following problems arise. In other words, when a resist is irradiated with light at a strong intensity, gas is rapidly generated due to the photochemical reaction of the resist itself and the decomposition of solvents and additives in the resist. May form bubbles. When this resist foams, the foamed portion of the resist rubs against the wafer cassette and adheres to the pattern forming area of the wafer, causing the problem of pattern defects described above.

[Purpose of the invention]

The present invention has been made in consideration of such problems,
It is an object of the present invention to provide a wafer periphery exposure apparatus that can increase productivity in wafer periphery exposure by shortening the exposure time and does not cause foaming of the resist.

〔composition〕

In order to achieve the above object, the wafer peripheral exposure apparatus of the present invention includes a first rotary stage on which a wafer coated with resist is placed and rotates two or more revolutions, and a temperature controller provided on the second rotary stage. The mechanism, the light guide fiber that exposes the periphery of the wafer placed on the first rotation stage, and the wafer exposed in the light source lamp! 3! a second light beam consisting of a light guide fiber and a light source lamp that exposes the periphery of the wafer placed on the second rotation stage with a stronger illuminance than the first light irradiation mechanism; It is characterized by comprising an irradiation mechanism and a cooling mechanism that cools the wafer exposed on the first rotation stage until the wafer is transferred to the second rotation stage.

[Effect]

In the wafer periphery exposure apparatus having the above configuration, the wafer coated with resist is first exposed to light at low illuminance and high temperature on the first rotating stage, then cooled by the cooling mechanism, and then transferred to the second rotating stage. exposed at high illuminance and low temperature. Therefore, as will be explained later, the exposure can be completed in a short time without causing foaming of the resist.

(Example〕 The present invention will be explained in detail below.

FIG. 1 is a schematic explanatory diagram of a wafer peripheral exposure apparatus according to an embodiment of the present invention.

In Fig. 1, 11.21 is a light source lamp such as an ultra-high pressure mercury lamp, 12.22 is an elliptical condenser mirror, 1323 is a flat reflector, 14 is a neutral density filter, 15°25 is a shutter, 16
．． 26 is a light guide fiber, W is a wafer coated with resist, 1? .

Reference numeral 27 indicates first and second rotation stages having vacuum suction holes (not shown), reference numerals 18 and 28 indicate a stage drive mechanism, and reference numeral 30 indicates a cooling mechanism.

In FIG. 1, a heater 71 is provided inside the rotary stage 17 as a temperature control mechanism, and the heating temperature of the heater 71 is controlled by a controller (not shown).

The cooling mechanism 30 includes a cooling stage 37 having a water cooling pipe 3B therein, and the wafer W is cooled by being placed on the cooling stage 37 by a transport system (not shown). The cooling stage 37 has a temperature sensor (not shown), and a controller (not shown) controls the amount of cooling water in the water cooling pipe 38 based on a signal from the temperature sensor so that the cooling stage reaches a predetermined temperature.

The light source lamp 11 and the light guide fiber 16 constitute a first light irradiation mechanism, and the light source lamp 21 and the light guide fiber 26 constitute a second light irradiation mechanism.

In FIG. 1, a wafer W coated with resist is transferred to the first rotation stage 17 by a transfer mechanism (not shown) and vacuum-adsorbed, and at the same time, the rotation stage 17 starts rotating in response to a signal from the controller 9. The shutter 15 is opened and exposure on the first rotation stage 17 is started.

During exposure on the first rotation stage 17, a neutral density filter 14 is placed on the optical path, and for example, 1200 mW/c
The wafer W is exposed to light at a weak illumination intensity of m". Then, the wafer W is exposed so that the total exposure amount is, for example, 275 mJ/cs +
is rotated 6 times at a speed of 5 strokes/rotation. Note that the heater 7 is turned on so that the temperature of the wafer W at this time is, for example, 70°C.
1 is controlled by a controller (not shown).

When the exposure on the first rotary stage 17 is completed, the rotation of the rotary stage 17 is stopped and the shutter 15 is closed in response to a signal from the controller. Thereafter, the transport mechanism transports the wafer W from the rotation stage 17 to the cooling stage 37 in response to a signal from the controller.

In the cooling mechanism 30, the above-described control is performed by the controller so that the temperature of the wafer W is, for example, 25°C.

After cooling the wafer W to, for example, 25° C., a transport mechanism (not shown) transports the wafer W from the cooling stage 37 to the second rotation stage 27, and as in the case of the first rotation stage 17, the wafer W is subjected to vacuum suction. The second rotary stage 27 starts rotating, the shutter 25 opens, and the light guide fiber 26 exposes the periphery Wp of the wafer on the second rotary stage 27 . The illumination intensity is stronger than the illumination intensity at the first rotation stage 17, for example, 3000 mW/c-
= illuminance, and the exposure ends when the wafer W is rotated once. At this time, the temperature of the wafer W may be room temperature, but the second rotation stage 27 may also be provided with a temperature control mechanism and controlled by a controller so that the wafer W is maintained at, for example, the aforementioned 25° C.

Under the above conditions, 0FPR-8 manufactured by Tokyo Ohka Kogyo Co., Ltd.
When a resist coated with 00 to a thickness of 2 μm was exposed and tested, no foaming of the resist was found and the resist could be reliably removed in the development process, which was found to be suitable.

Hereinafter, the reason why resist firing does not occur in this example and the exposure is completed in a short time will be explained in more detail.

FIG. 2 is a perspective view for explaining the exposure amount in this example, where W is the wafer, Wp is the wafer periphery, A is a fixed point around the wafer, and E is the light emitted from the light guide fiber 6. In this embodiment, the exposure amount is the total amount of light that the fixed point A receives while passing through the exposure area E. For example, if the illuminance is set to 1. If the time taken for the fixed point A to pass through the exposure area E is t, and the number of revolutions at which the wafer is rotated is n, then the exposure amounts will be lXt and Xn.

Specifically, the bubbling phenomenon of the resist occurs because the amount of gas generated per unit time (hereinafter referred to as generation rate) is larger than the amount of gas released per unit time (hereinafter referred to as release rate). That is, since the amount of gas generated is greater than the amount of gas released to the outside of the resist, the inside of the resist is filled with gas, and the filled gas increases and concentrates, leading to foaming.

The rate of gas production is the rate of photochemical reaction (hereinafter referred to as reaction rate)
The gas release rate is determined by the rate at which the generated gas diffuses in the resist (hereinafter referred to as diffusion rate).

Therefore, in terms of -S, in order to perform exposure while suppressing foaming of the resist, it is sufficient to reduce the reaction rate (and increase the diffusion rate to keep the production rate below the release rate).

Here, the reaction rate is vP, the diffusion rate is v4r, and the illuminance is 1.
When the temperature of the resist is T, /v, OCT, exp (-Ha/kT) -i
v a ec exp <-〇/ni? )
---ii It is known that there is a relationship.

In addition, Ea is the activation energy of reaction, is a gas constant, and Q is the activation energy of diffusion.

Therefore, in order to establish the relationship V,<V, l
It is conceivable to reduce V by lowering . but,
Lowering I requires longer exposure times to provide a certain amount of exposure needed to remove the resist during the development step. However, if the gas release medium in the resist has been sufficiently reacted and decomposed and released (hereinafter referred to as gas release) in advance, no bubbles will be generated even if exposed to a large l.Therefore, the first rotation stage 17 If the gas release medium is exposed to a low illumination intensity (hereinafter referred to as !1) and the gas release medium is sufficiently released, the second rotation stage 2
Even if exposure is performed at a strong illumination intensity (hereinafter referred to as 1.) in step 7, no firing occurs, and the rotation speed of the wafer W can be increased to shorten the exposure time.

Here, strong illumination at the second rotating stage 27! !
In order to cause sufficient gas release through exposure at the first rotation stage 17 so that bubbles do not occur even when exposed to light at Exposure necessary for sufficient gas release! (hereinafter referred to as gas release exposure IH1) at 1 and T satisfying the above relationship vr<v4, the rotation speed of the wafer W must be considerably slowed down, and the The exposure time (t, Xn, hereinafter referred to as t) becomes long and does not actually contribute much to improving productivity.

Here, even if v,>v, foaming does not occur immediately, but there is gas filled in it - it is necessary for it to gather in an amount greater than the window. If exposure is started under the condition of v,>V, and the time required for the filled gas to collect above a certain level and bubble to form is the bubbling time tb, then the passage time is [. 〈If the bubbling time (b) is reached, no bubbling will occur, and the amount of gas generated by passing the - time is determined by the product of the illuminance and the passing time t + 1 × (. In other words, 1. Even if t is increased, the amount of gas generated remains the same if t is decreased.In other words, it is possible to increase It by decreasing t.

Therefore, in this embodiment, the first rotation stage 17
The number of rotations n of the wafer W is set to a plurality of times, the gas release exposure amount H1 is applied to the resist in each pass, and the above-mentioned passing time t0 is decreased, that is, the rotation speed is increased, and the passing time 1. <Foaming time t.

Then, the gas generated by the exposure is released into the resist during a time period during which the fixed point A is not irradiated with light until the wafer W rotates once and the same fixed point A is exposed next time. At this time, since the wafer W is heated, the gas is quickly released from the resist during the time period when the wafer W is not irradiated with light, according to the above equation (ii). Furthermore, as mentioned above, t.

11 can be increased by decreasing , so the exposure time of the first rotating stage 17 by 1° (=(. 27, the exposure is performed at a stronger illuminance than the first rotating stage 17, but the gas release medium is sufficiently reacted and decomposed and released by the exposure on the first rotating stage 17, so that no foaming occurs. That is, since exposure is performed at an illuminance of 12, which is stronger than the illuminance of 1, the exposure time t at the second rotating stage 27, which provides the exposure N (hereinafter referred to as H2) necessary for removing the resist in the developing process, can be shortened. If a trace amount of the gas release medium remains in the resist after exposure on the first rotation stage 17, it will be irradiated with light at the above-mentioned strong illuminance 12, but the remaining amount of the gas release medium is small. Moreover, since the temperature of the resist is lower than that during exposure on the first rotation stage 17, the gas generation rate from the first generation is sufficiently lower than the gas release rate and does not result in foaming.

In the above embodiment, the cooling mechanism 30 is composed of the cooling stage 37 and the water-cooling bib 138, but the invention is not limited to this. Forced air cooling
A cooling stage with cooling fins or the like may be used.

Moreover, various heaters such as a sheet-shaped heater, a cartridge-shaped heater, a sheath heater, etc. can be used as the heater 71 as a temperature control mechanism.

Note that the light source lamp 11 and light guide fiber 1 described above
For the first light irradiation mechanism consisting of 6 and the second light irradiation mechanism consisting of the light source lamp 21 and light guide fiber 26, if a light guide fiber branched into two from the middle is used, one light source lamp and light guide fiber can be used. can serve as both.

〔Effect of the invention〕

As explained above, the wafer peripheral exposure apparatus of the present invention includes a first rotation stage on which a resist-coated wafer is placed and rotates two or more revolutions, and a temperature control mechanism provided on the second rotation stage. , a first light irradiation mechanism consisting of a light guide fiber and a light source lamp that exposes the peripheral part of the wafer placed on the first rotation stage; A second light irradiation mechanism consisting of a light guide fiber and a light source lamp that exposes the periphery of the wafer placed on the second rotation stage; Since the wafer is equipped with a cooling mechanism that cools the wafer until it is transferred to the second rotation stage, it is first exposed with low illuminance and a high temperature of the resist, and then exposed with high illuminance and a low temperature of the resist. can be exposed to light. Therefore, the exposure can be completed in a short time without foaming of the resist, resulting in a wafer peripheral exposure apparatus with high productivity.

In addition, since the cooling mechanism is not provided separately from the rotation stage, the structure of the rotation stage is not complicated, and since there are two rotation stages and the cooling mechanism is provided separately, the second rotation stage is used to control the exposure. At the same time, the next wafer can be cooled by the cooling mechanism, and the next wafer can be exposed at the same time on the first rotation stage, making the wafer peripheral exposure apparatus highly productive in this respect as well.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a wafer peripheral exposure apparatus according to an embodiment of the present invention, Fig. 2 is a perspective view for explaining the exposure amount in this embodiment, and Fig. 3 is a resist that has gone around to the back side of the wafer. FIG. 4 is a partial cross-sectional view of a wafer showing the shape of a circuit pattern exposed on the wafer. In the figure, 11.21 -・-・-1---Light source lamp 16.
26 -・------Light guide fiber 1'l
−・・・−−−m=−・・−・−First rotation stage 27・−・・−・・−・・−−−1−−−−−Second rotation stage 71 −−・・−・・−・・−・−・・
Heater 30-------1------------
- Indicates the cooling mechanism p. Maruhino Ginru” Suspension 20 Wafer Surrounding area of wafer

Claims (1)

[Claims] A first rotation stage on which a wafer coated with resist is placed and rotates two or more revolutions, a temperature control mechanism provided on the first rotation stage, and a peripheral area of the wafer placed on the first rotation stage. a first light irradiation mechanism consisting of a light guide fiber and a light source lamp that exposes the wafer; a second rotation stage on which the wafer exposed on the first rotation stage is placed; A second light irradiation mechanism consists of a light guide fiber and a light source lamp that exposes the periphery of the wafer with a stronger illuminance than the first light irradiation mechanism, and the wafer exposed on the first rotation stage is moved to the second rotation stage. A wafer peripheral exposure apparatus comprising: a cooling mechanism that cools the wafer until the wafer is transported to the wafer.