JPH0257699B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to processing of photoresist (hereinafter referred to as resist) applied to a semiconductor wafer.
In particular, the present invention relates to a resist processing method using an ultraviolet irradiator to improve the heat resistance and plasma etching resistance of the resist.

[Prior Art] Regarding the conventional processing of resist using ultraviolet irradiation, ultraviolet rays are used in the process of exposing a mask pattern to the resist coated on a semiconductor wafer, the pre-cleaning process of decomposing and cleaning organic contaminants attached to the resist surface, etc. Irradiation has been used, but recently,
Application to the baking process, which is one of the resist processing processes, is attracting attention.

The baking process is an intermediate process between the process of forming a resist pattern by resist coating, exposure, and development, and the process of performing ion implantation, plasma etching, etc. using this resist pattern, and is used to bond the resist to the semiconductor substrate. This is a heating process aimed at improving properties and heat resistance. Recently, studies have been conducted on methods and apparatuses for increasing the heat resistance and plasma etching resistance during baking in a shorter time by irradiating the resist with ultraviolet rays before or during the baking process after development.

[Problems to be Solved by the Invention] As described above, irradiation with ultraviolet rays has recently been considered in the resist baking process.

However, when a resist is irradiated with high-intensity ultraviolet light to speed up processing, gas is generated from inside the resist, and this gas can cause bubbles to form, resist pattern to collapse, resist film to peel, burst, and become rough. Destruction of the resist film occurs, resulting in semiconductor device failure.

One of the causes of this gas generation is the rapid photochemical reaction of exposed photosensitive groups in the resist, and the photochemical reaction between the resist and HMDS (hexamethyldisilazane) or antireflective agent applied to the wafer as a pretreatment for resist coating. Possible causes include photochemical reactions of resist additives such as dyes, and photochemical reactions of solvents remaining in the resist.

These photochemical reactions have wavelengths of 300nm to 500nm.
Therefore, resist processing equipment that emits light in these wavelength ranges cannot increase the intensity of the light. In other words, there was a problem that high-speed processing could not be performed.

In view of these problems, the present invention provides a resist processing method that can process the resist by ultraviolet irradiation at high speed and effectively by preventing the resist film from being destroyed by the radiation emitted from the ultraviolet irradiator. The purpose is to provide

[Means for Solving the Problems] In order to achieve this object, in the present invention, an ultraviolet irradiator and a processing chamber are constructed by sandwiching an ultraviolet transmitting member, and the shutter opening/closing time in the ultraviolet irradiator is reduced. a control means for controlling a filter drive time; a control means for controlling a light emission intensity and a light emission time of at least one lamp for ultraviolet irradiation; and control means for controlling the elapsed time with respect to the temperature.

[Function] In the present invention, for example, by effectively blocking or reducing the exposure wavelength of the resist, photochemical reactions that generate gas from the resist are suppressed, and destruction of the resist film is prevented. Moreover, even if the exposure wavelength of the resist is blocked or reduced, the irradiated light still contains a strong ultraviolet component that is effective in improving the heat resistance and plasma etching resistance of the resist. Can perform resist processing. In addition, since the type of filter or shutter can be changed depending on the cause of gas generation, the method of gas generation, and other causes of membrane damage, a variety of treatments can be performed.

[Example] FIG. 1 is an explanatory diagram of an ultraviolet treatment apparatus showing an example of the resist processing method of the present invention, in which 20 is an ultraviolet irradiator and 30 is a treatment chamber. In addition, 1 is one or more lamps for ultraviolet irradiation, 2
3 is a shutter; 4 is a reversible motor that drives the shutter 3 to open and close; 5 is a control means that controls the operation of the reversible motor 4 to control the opening and closing time of the shutter 3; Control means for controlling; 6 is a wavelength selective filter formed by forming a multilayer vapor deposited film on a quartz glass plate; 7 is a reversible motor that drives the filter 6 to open and close; 8 is a control means for controlling the driving time of the filter 6; 9 is a mirror placed behind the lamp 1; 10 is an ultraviolet-transparent glass plate; 11 is a flange that covers the edge of this ultraviolet-transparent glass plate;
12 is a packing that fills the gap between the flange 11 and the processing chamber 30; 13 is a blower that prevents the temperature of the air inside the ultraviolet irradiator 20 from rising and sucks the air to cool the lamp 1; and 14 and 15 are the blowers 1.
3 is an air inlet/outlet for suction, 31 is a processing table on which the object to be processed is placed, 32 is a heating means for heating this processing table 31, and 33 is a cooling means for cooling this processing table 31. Reference numeral 34 denotes an entrance/exit for loading and unloading the objects to be processed along the conveyance line 35, and heating means 32 and cooling means 33 are connected to the processing table 3.
1 and the elapsed time for that temperature.

FIG. 2 is a timing chart showing an example of an operating state when resist processing is performed using the ultraviolet processing apparatus shown in FIG.

Although there are various patterns of operation depending on the type of resist to be processed, the resist processing method in the embodiment shown in FIG. 1 will be explained below according to the example shown in FIG.

First, so-called baking is performed by raising the temperature of the processing table 31 to T ₁ (120° C.) for a certain time x ₁ (approximately 5 seconds) with the shutter 3 closed. This is because it is necessary to raise the temperature of the resist as high as possible in order to improve the heat resistance of the resist and speed up resist processing. If the resist is suddenly irradiated with high-intensity ultraviolet light in order to speed up resist processing, gas will be generated from inside the resist, but if the baking process described above is performed, a certain amount of gas can escape just by increasing the temperature due to heating. This can prevent sudden firing within the resist.

Next, shutter 3 is operated for a time y ₁ (approximately 5 seconds).
When opened and exposed to weak light, a photochemical reaction gradually occurs within the resist and gas is generated. in this case,
Even when the shutter is opened, only weak light is transmitted through the filter 6 as will be described later. If this shutter 3 is left open, gas will be generated rapidly, and before it can escape from the surface of the resist, it will turn into bubbles and grow larger.
is closed for a time x ₂ (about 5 seconds), the light irradiation is temporarily stopped, and the baking process is continued again to allow the gas generated within the resist to escape.

After that, shutter 3 is opened, but if the light is irradiated rapidly, there is a risk that the remaining gas will ignite, so the irradiation is performed for a certain period of time (about ₂ seconds) and the irradiation is gradually increased. . In addition, the temperature of the processing table was gradually increased after the baking process for time t ₁ (approximately 15 seconds), and the use of filter 6 was also stopped after the first time t _F (12 seconds) and filter 6 was removed. ,
The workpiece is irradiated with ultraviolet light with high intensity and heated to high temperatures.

Here, the use of the filter 6 will be described. Gas is rapidly generated by a photochemical reaction within the resist, and before it escapes from the surface of the resist, it becomes a cannon and grows in size, which depends on the wavelength of the light irradiating the resist, and will be discussed later. If light of a certain wavelength is cut off, even if gas is generated, it will easily escape to the outside. Therefore, a filter 6 is used to cut out light of a certain wavelength, and a degassing process is performed. Specifically, the light having a certain wavelength that is cut by the filter 6 is, for example, ultraviolet light having a short wavelength of 300 nm or less.

When this short wavelength light of 300 nm or less is irradiated,
Resist easily hardens through a polymerization reaction, and once the resist hardens, a thin skin forms on its surface, and this thin skin makes it difficult for the gas generated inside the resist to dissipate. As a result, the resist itself ruptures. Therefore, in order to prevent this rupture, it is necessary to prevent the formation of the thin skin as much as possible in the above-mentioned initial degassing step.

Also, the wavelength at which gas is easily generated is 300 to 500 nm.
Therefore, the light with a wavelength of 300 to 500 nm is weakened and irradiated for a short period of time u ₂ (about 5 seconds) until the gas generated in the resist is dissipated. Of course, in that case, the time to use the filter t _F (about 12 seconds)
Because it is inside, 300nm light is filtered out, so there is no formation of a thin skin on the resist surface, and the generated gas is dissipated to the outside.

Once the gas is completely drained, filter 6
If the gas is dissipated, the filter 6 will be cut off and the _resist will not harden.
, and sufficiently irradiates light with a short wavelength of 300 nm or less.

The above is an outline of an example of the resist processing method, and the temperature of the processing table 31 is kept constant T ₁ during a certain time t ₁ (approximately 15 seconds) at the start of processing. it is,
Heat resistance improves only after the resist is cured, but in the initial stage (time _tF : approximately 12 seconds), the filter 6 is used to cut out the light at the wavelength at which the resist is cured, so the resist does not cure. This is because it lacks heat resistance due to the lack of heat resistance. Therefore, filter 6
The resist processing speed can be increased by increasing the temperature of the processing table 31 after the resist is removed and the heat resistance is improved.

Furthermore, when the shutter 3 is open for a time y ₂ , the relationship between the temperature of the processing table and time does not rise in a straight line between the time t ₂ and the time t ₃ , which is due to the relationship with time. , indicating that the increase in heat resistance of the resist does not necessarily increase linearly. When the temperature of the resist increases to a certain degree, the heat resistance improves slowly, and a rapid temperature increase is not desirable. Therefore, when the temperature rises to a certain extent, it is necessary to use the heating means 32 or the cooling means 33, which are temperature control means of the processing table, to moderate the degree of temperature rise. Therefore, the temperature pattern is changed as shown by the curve in FIG.

Furthermore, in the above embodiments, the temperature control and the wavelength and intensity of the irradiation light were variously changed using time as a parameter, but it is not necessary that all resist processing be performed according to the curve shown in FIG. Of course, it is possible to change it according to each resist pattern.

FIG. 3 shows a specific example of the control means 5 for controlling the opening/closing time of the shutter 3 or the control means 8 for controlling the driving time of the filter 6 in FIG. 1, and FIG. FIG. 5 is a circuit diagram showing a specific example of the control means 2 for controlling the light emission time, FIG. 5 is a specific example of the cooling means 33 shown in FIG. 1, and FIG. 6 is a circuit diagram showing a specific example of the heating means 32 shown in FIG. 1. In addition, in each figure, CPU is a central processing unit of a computer that controls the processing method of the present invention, 31, 41,
51 is a relay, 32, 42, 52 are switches,
LT is leakage transformer, PS is power supply, H is heater, C is capacitor, SCR is thyristor,
V ₁ and V ₂ indicate solenoid valves, and the same symbols as in FIG. 1 indicate the same or corresponding parts.

When the circuit shown in FIG. 3 is used as the control means 5 of the shutter 3, it is necessary to follow the processing program input into a computer (not shown) in advance.
A signal from the CPU is output, and based on this output signal, the voltage supplied to the drive coil of the reversible motor 4 is switched to the relay 31 to control the rotational direction of the reversible motor 4, and the shutter 3
Open and close.

When the circuit shown in FIG. 3 is used as the control means 8 for the filter 6, the rotation direction of the reversible motor 7 is controlled to move the filter 6 in the same manner as for the control means 5.

In the control means 2 in FIG. 4, a program for controlling the luminous intensity and luminous time of the lamp 1 is inputted in advance into a computer. Then, according to this program, a signal is output from the CPU,
Based on this output signal, there is a success or failure in energizing the relay 41, which determines whether the leakage transformer LT,
Two resonant circuits consisting of capacitors C ₁ and C ₂ , lamp 1, and resistor R are switched to control the current flowing through lamp 1, thereby changing the intensity of lamp 1.

The cooling means 33 in FIG. 5 supplies cold water to a pipe (not shown) installed inside the processing table 31 in order to control the temperature of the processing table 31 and the elapsed time for that temperature which are programmed in the computer in advance. This is intended to lower the temperature of the processing table.

When cooling the processing table 31, the relay 51 closes the solenoid valve V2 by switching the switch 52 according to a signal from the CPU, and opens _{the solenoid valve V1 to} allow cooling water to flow. To stop cooling, close V ₁ and then open V ₂ for a few seconds to close processing table 31.
Drain the water remaining in the pipe.

Further, the heating means 32 in FIG. 6 supplies current to a heater placed inside the processing table 31 in order to control the temperature of the processing table 31 and the elapsed time for that temperature, which are programmed in the computer in advance. This increases the temperature of the processing table.

When you want to heat, the gate of thyristor SCR ₁ or SCR ₂ is excited by the output signal from the CPU to supply heater current, and when you want to stop heating, stop the energization of the gate of SCR ₁ or SCR ₂ . Disconnect the heater circuit.

It should be noted that the circuits shown in FIGS. 3 to 6 are merely examples of implementing the present invention, and it goes without saying that the resist processing method of the present invention can be implemented by providing other control means. It is.

[Effects of the Invention] As explained above, the present invention comprises an ultraviolet irradiator and a processing chamber sandwiching an ultraviolet transmitting member,
The ultraviolet irradiator includes a means for controlling shutter opening/closing time, a control means for controlling filter drive time, and a control means for controlling the light emission intensity and light emission time of at least one lamp for ultraviolet irradiation, Furthermore, by providing a control means for controlling the temperature of the processing table in the processing chamber and the elapsed time with respect to the temperature, high-speed and effective resist processing has become possible.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of essential parts of an ultraviolet treatment device showing an embodiment of the resist processing method of the present invention, and FIG. 2 is an example of an operating state when resist processing is performed using the device shown in FIG. 1. FIG. 3 is a circuit diagram showing a specific example of the control means for controlling the opening and closing of the shutter or filter shown in FIG. 1, and FIG. 4 is a specific example of the control means for controlling the light emission of the lamp. The circuit diagram shown in Figure 5 is the first
FIG. 6 is a circuit diagram showing one specific example of the cooling means shown in the figure, and FIG. 6 is a circuit diagram showing one specific example of the heating means. In the figure, 1: lamp, 2, 5, 8, 33: control means, 3: shutter, 6: filter, 9: mirror, 10: ultraviolet transmitting glass plate, 20: ultraviolet irradiator, 30: processing chamber, 31: Processing table, 34: Entrance/exit, 35: Conveyance line.

Claims (1)

[Claims] 1. An ultraviolet irradiator equipped with at least one ultraviolet irradiation lamp with a mirror arranged behind it, a shutter and a filter installed in front of these lamps and each equipped with a drive mechanism, and a temperature control means. a processing chamber incorporating a processing table and having a slit-shaped entrance/exit for conveying the workpiece to the processing table; and the ultraviolet irradiator so that the ultraviolet rays from the ultraviolet irradiator are directed toward the processing table. In a resist processing method in which the resist is processed in an apparatus comprising an ultraviolet transmitting member that partitions the inside of the ultraviolet irradiator and the inside of the processing chamber when the shutter is installed on the processing chamber, the shutter is closed. After baking the wafer coated with resist on a pre-heated processing table, the shutter is opened and weak light from a lamp is irradiated through a filter for a few seconds, then the shutter is closed again and the wafer is exposed to light. After the baking step, the temperature is gradually increased and the lamp illuminance is increased step by step, and the lamp is turned off without passing through a filter within a range that does not cause bubbles to grow in the resist. A resist processing method characterized by comprising a step of irradiating strong light.