JPH0795519B2 - Exposure amount control device for wafer peripheral exposure - Google Patents

Description

The present invention relates to a semiconductor substrate typified by a silicon wafer or a dielectric in a fine pattern forming step in the processing of parts in ICs, LSIs, and other electronic elements. , Peripheral exposure of a wafer for removing unnecessary resist in the peripheral portion of the substrate such as metal, insulator, etc. applied to the substrate in a developing process.

[Conventional technology]

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

Usually, the resist is applied by a spin coating method. In the spin coating method, the resist is not poured onto the center position of the wafer surface, the wafer is rotated, and the resist is applied to the surface of the wafer by centrifugal force. However, according to this spin coating method, the resist may protrude from the peripheral portion of the wafer and may go around to the back side of the wafer.

FIG. 3 is a partial cross-sectional view of the wafer showing the resist that has wrapped around to the back side of the wafer. 1 is the wafer, 1p is the wafer peripheral portion, 1a is the resist of the pattern forming portion, and 1b is the wafer peripheral portion 1p. The resist on the surface is shown as 1c, and the resist 1c extends from the edge of the wafer 1 to the back side.

FIG. 4 is a view showing the shape of the circuit pattern exposed on the wafer. One area indicated by T corresponds to one circuit pattern. In most cases, the circuit pattern cannot be correctly drawn on the peripheral portion of the wafer, and the yield is poor even if it can be drawn. Therefore, the surface of the peripheral portion of the wafer is actually an unnecessary resist.

The presence of the unnecessary resist that wraps around from the edge to the back side of the wafer peripheral portion and the unnecessary resist on the surface of the wafer peripheral portion causes the following problems. That is, the resist-coated wafer is transported by various processing steps and various methods. At this time, the peripheral portion of the wafer is mechanically grasped and held, or the peripheral portion of the wafer is rubbed against the wall of a container such as a wafer cassette. At this time, if unnecessary resist around the wafer is removed and adheres to the pattern forming portion of the wafer, correct pattern formation cannot be performed and the yield is reduced.

It is a serious problem that the unnecessary resist around the wafer becomes "dust" and the yield is lowered, especially in the present situation where the performance and miniaturization of integrated circuits are progressing.

Therefore, as a technique for removing the unnecessary resist on the peripheral portion of the wafer, a technique for spraying a solvent from the back surface of the peripheral portion of the wafer to dissolve and remove the unnecessary resist by a solvent injection method has been put into practical use. But with this method,
The resist 1c on the protruding portion in FIG. 3 can be removed, but the resist 1b on the surface of the peripheral portion of the wafer is not removed. Even if the solvent is sprayed from the surface of the wafer 1 in order to remove the resist 1b on the surface of the peripheral portion of the wafer, not only the problem of splashing of the solvent is caused but also the unnecessary resist 1b on the surface of the peripheral portion of the wafer is removed. It is not possible to remove only the unnecessary resist sharply and with good controllability at the boundary with the resist 1a in the pattern forming portion, which is a resist required as a mask layer for etching or ion implantation.

Therefore, recently, in addition to the exposure process for forming a pattern, a wafer peripheral exposure method has been performed in which exposure is separately performed to remove unnecessary resist in the peripheral portion of the wafer in a developing process.
In this wafer edge exposure method, while rotating a wafer coated with a resist, the light guided by a light guide fiber is applied to the wafer edge to circumferentially expose the wafer edge.

[Technical problem to be solved by the invention]

In such a wafer peripheral exposure, if the exposure amount for the resist is insufficient, the resist remains after development and becomes the above-mentioned "dust", which hinders correct pattern formation. Therefore, it is necessary to control the exposure amount on the peripheral portion of the wafer to maintain it at a constant amount required for resist removal.

In the case of exposure by a stepper in the photolithography process, it has been conventionally practiced to keep the exposure amount constant by controlling the exposure time.

However, in the peripheral exposure of the wafer, since the wafer is rotating, it is not possible to uniformly control the exposure amount in the peripheral portion of the wafer by simply controlling the exposure time.

On the other hand, since the exposure light source such as a mercury lamp, the light guide fiber for guiding the exposure light, and the optical components such as the projection lens deteriorate with time, the illuminance of the exposure light changes with time.

Conventionally, since the exposure amount of the peripheral portion of the wafer is not controlled according to the illuminance of the exposure light, there are cases in which a sufficient exposure amount cannot be secured, which is a cause of product defects.

[Object of the Invention]

The present invention has been made in view of the above problems, and the present invention can control the exposure amount of the peripheral portion of the wafer according to the change in the illuminance of the exposure light and can sufficiently secure the required exposure amount. An object of the present invention is to provide an exposure amount control device for wafer peripheral exposure.

[Structure of Invention]

In order to achieve such an object, the present invention provides an exposure amount control apparatus in wafer peripheral exposure, which includes a rotating mechanism for rotating a wafer coated with a resist and a light irradiation mechanism for irradiating the peripheral portion of the rotating wafer with light. When an illuminance monitor for monitoring the illuminance by the light from the light irradiation mechanism and a control means for controlling the rotating mechanism based on the illuminance monitor signal from the illuminance monitor are provided, when the illuminance detected by the illuminance monitor decreases. The time required for the wafer to rotate by a unit number of revolutions is increased, and the exposure amount at the peripheral portion of the wafer is kept constant.

[Action]

In the present invention, an illuminance monitor is provided, and when the illuminance detected by the illuminance monitor decreases, the time required for the wafer to rotate by a unit number of revolutions is increased. However, it is possible to sufficiently secure the necessary exposure amount. For this reason, the resist does not remain after development, and does not become "dust" and hinder pattern formation.

〔Example〕

 Examples of the present invention will be described below.

FIG. 1 is a schematic diagram for explaining an exposure amount control method in wafer peripheral exposure which is an embodiment of the present invention. L is a mercury lamp as an exposure light source, 2 is an elliptical focusing mirror, 3 is a flat reflecting mirror, 4 is a light guide fiber, 1 is a wafer, 6 is a rotating stage, 7 is an illuminance monitor, 8 is a comparator, 9 is a stage A drive motor, 10 is a controller.

FIG. 2 is a schematic view of the wafer 1 shown in FIG.
Is a peripheral portion of the wafer, 11 is an exposure pattern formed by light from a light guide fiber, and d is a width of the exposure pattern (hereinafter referred to as an exposure width).

In the wafer peripheral exposure of FIGS. 1 and 2, the light from the mercury lamp L is guided by the light guide fiber 4 and is rotated by the rotary stage 6 around the wafer 1.
Irradiate 1p.

Next, the operation of this embodiment in the wafer peripheral exposure shown in FIGS. 1 and 2 will be described.

Now, the amount of exposure to the wafer periphery ...... W (mJ / cm ² ) Exposure width ...... d (cm) Wafer radial exposure width ...... r (cm) Wafer diameter ...... a (cm) Reference illuminance ... … I ₀ (mW / cm ² ) Monitor illuminance …… I (mW / cm ² ) Rotation time required at standard illuminance …… t ₀ (sec) Controlled rotation time …… t (sec).

The exposure amount W is a value appropriately determined depending on the type and film thickness of the resist, and is, for example, manufactured by Tokyo Ohka Kogyo Co., Ltd.
When OFPR-800 is applied at a thickness of 2 μm, 460 mJ
An exposure dose of / cm ² is required. In this case, the reference illuminance I ₀ is 30
If it is 00 mW / cm ² , the rotation time t ₀ required when irradiating the wafer with the reference illuminance I ₀ (the time required for one rotation in this embodiment is a predetermined unit rotation speed). It takes 20 seconds to rotate).

The exposure width d is the width of the exposure pattern formed by the light from the light guide fiber shown in FIG. 2 (corresponding to the irradiation width by the light guide fiber), and the exposure width r in the wafer radial direction is shown in FIG. The exposure width in the radial direction of the wafer formed by the light from the light guide fiber and the monitor illuminance I are the illuminance monitored by the illuminance monitor 7 in FIG. Further, the controlled rotation time t is the time for actually rotating the rotary stage (in this embodiment, the time required for one rotation).

Now, when the wafer is rotated once at the rotation time t ₀ while irradiating with the reference illuminance I ₀ , the total amount E of light energy irradiated to the peripheral portion of the wafer is expressed by the following equation.

E = r × d × I ₀ × t ₀ (mJ · sec) On the other hand, E is the product r × π of the exposure amount W and the irradiation area r × πa.
Since it is equal to a × W (mJ · sec), the following equations (1) and (2)
Holds.

r × d × I ₀ × t ₀ = r × πa × W (1) When the illuminance detected by the illuminance monitor 7 is I, in order to make the exposure amount W equal to the above value, the rotation time t to be controlled may be defined by the following equation (3).

That is, the controlled rotation time t is expressed by the following equation (4).

In FIG. 1, the illuminance monitor 7 detects the illuminance of the exposure light emitted from the light guide fiber 11 and sends it to the comparator 8 when performing wafer peripheral exposure. The comparator 8 compares the monitored illuminance with the reference illuminance signal and sends the comparison result to the system controller 10.

When the monitored illuminance is equal to the reference illuminance, the system controller 10 drives the stage drive motor 9 so that the rotary stage 6 makes one rotation at time t ₀ . Also, if the monitor illuminance decreases for some reason, go to (4) above.
The time t is calculated by the formula, and the stage drive motor 9 is driven so as to make one rotation at the time t.

For example, OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.
For wafers coated with a thickness of
The peripheral area of the wafer is exposed so that the wafer rotates once in 20 seconds at 00 mW / cm ² (reference illuminance), but if the monitor illuminance decreases to 2500 mW / cm ² for some reason, The system controller 10 drives the stage drive motor 9 so that the wafer makes one revolution in seconds.

In the present embodiment, when performing the peripheral exposure of the wafer as described above, the illuminance of the exposure light is monitored, and when the illuminance is lowered, the time required to rotate the unit rotational speed is lengthened accordingly. The peripheral portion of the wafer can be uniformly exposed with a desired exposure amount.

〔The invention's effect〕

As described above, in the present invention, the illuminance of the exposure light is monitored and the time required for the wafer to rotate by a unit number of revolutions is controlled. It is possible to perform uniform exposure with the exposure amount of.

Therefore, there is no residual resist after development due to insufficient exposure amount, and the residual resist does not become "dust" and cause pattern defects.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an exposure amount control method in wafer peripheral exposure which is an embodiment of the present invention, and FIG.
FIG. 1 is a schematic view of the wafer of FIG. 1 seen from above, FIG. 3 is a partial sectional view of the wafer showing a resist which has wrapped around to the back side of the wafer, and FIG. 4 shows the shape of a circuit pattern exposed on the wafer. FIG. In the figure, 1 ... Wafer 1p ... Wafer peripheral part 4 ... Light guide fiber 6 ... Rotation stage 7 ... Illuminance monitor 8 ... Comparator 9 ... Stage drive motor 10 ... Controller.

Claims (1)

[Claims] 1. An exposure amount control apparatus for wafer peripheral exposure, comprising: a rotation mechanism for rotating a wafer coated with a resist; and a light irradiation mechanism for irradiating the rotating wafer with light to the peripheral portion of the wafer. An illuminance monitor for monitoring the illuminance by the light of, and a control means for controlling the rotating mechanism based on the illuminance monitor signal from the illuminance monitor are provided, and the control means, when the illuminance detected by the illuminance monitor decreases, An exposure amount control apparatus for wafer peripheral exposure, which increases the time required for the wafer to rotate a unit number of revolutions to keep the exposure amount at the peripheral portion of the wafer constant.