JPH0231857B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for processing photoresist coated on a semiconductor wafer, and in particular, to a method for processing photoresist coated on a semiconductor wafer. The present invention relates to a treatment method that combines treatment and ultraviolet irradiation treatment.

[Conventional technology]

In the manufacturing process of semiconductor devices, the steps for forming a photoresist pattern can be roughly divided into the following order: resist coating, pre-baking, exposure, development, and post-baking. Thereafter, using this photoresist pattern, ion implantation or plasma etching of the silicon oxide film, silicon nitride film, aluminum thin film, etc. previously formed on the surface of the semiconductor wafer before applying the resist is performed. At this time, since the temperature of the photoresist increases during ion implantation, it is better to have high heat resistance, and during plasma etching, durability is required to prevent "film peeling" from occurring. However, in recent years, with the increasing integration and miniaturization of semiconductor devices, photoresists with higher resolution have come to be used, but in this case, photoresists are positive type, and are generally more sensitive than negative types. Poor heat resistance.

As methods for increasing the heat resistance and plasma resistance of photoresists, methods are being considered, such as increasing the temperature stepwise during post-baking and performing heat treatment for a sufficient period of time, and irradiating the photoresist pattern with ultraviolet rays after development. However, the former method has the disadvantage that sufficient heat resistance and plasma resistance cannot be obtained and the processing time is significantly longer. and,
In the latter method, the heat resistance temperature increases due to ultraviolet irradiation, but if the photoresist film is thick, the ultraviolet rays will not reach the inside of the photoresist, and the heat resistance will not be sufficiently improved or the processing time will increase. The disadvantage is that it is long.

Therefore, recently, "heating" and "ultraviolet irradiation" are being used, for example, as disclosed in JP-A No. 60-45247 "Photoresist curing method and curing device".
A combination of the two has been proposed, and some have put it into practical use with some success. however,
The curing speed and state of curing differ slightly depending on the type and thickness of the photoresist, as well as the intensity of ultraviolet irradiation, and in particular, the heat resistance is sufficiently improved to the inside of thick photoresists. In order to achieve this, it was found that it was necessary to consider a method of raising the temperature.

For example, the photoresist formed by applying TSMR-8800 manufactured by Tokyo Ohka Kogyo Co., Ltd. is usually 1.7μm.
A slightly thicker film of about 2.0 μm is used, and the intensity of the ultraviolet rays is increased to promote polymerization, and the temperature rise rate of the processing table is increased accordingly. Attempting to shorten processing time causes the following problems. In other words, since photoresist does not originally have good UV transmittance, increasing the UV intensity and shortening the irradiation treatment time will result in a large difference in the UV intensity that reaches the surface layer and the inside of the film. There is a difference in the degree of progress of etching, and the heat resistance and plasma etching resistance of the surface layer improve, but the improvement does not improve sufficiently inside.

[Problem that the invention seeks to solve]

In this way, with conventional resist processing methods, even if some improvement in heat resistance and plasma resistance can be achieved, especially when the photoresist film is thick, the heat resistance inside it is insufficient. However, as a result, the problem remains that the heat resistance of the photoresist is low. If an attempt is made to sufficiently improve heat resistance, a problem arises in that the processing time becomes extremely long. That is, there is a problem in that the entire resist process cannot be carried out organically and effectively.

In view of these circumstances, the present invention provides a resist processing method that organically combines ultraviolet irradiation with heat treatment, sufficiently improves heat resistance to the inside of the photoresist film even if it is thick, and has excellent productivity. The purpose is to

[Means for solving problems]

Therefore, in the present invention, the photoresist coated on a wafer placed on a processing table equipped with a temperature control means is irradiated with ultraviolet rays to increase the flow temperature of the photoresist, thereby improving its heat resistance, plasma resistance, etc. In the resist processing method, the wafer is placed on a processing table that has been heated in advance to a temperature slightly higher than the flow temperature of the photoresist, and the processing table is heated while irradiating ultraviolet rays so that the photoresist temperature is always slightly higher than the flow temperature. a step of raising the temperature to a first predetermined temperature at a uniform temperature increase rate of 1; and after reaching the first predetermined temperature, a step of increasing the temperature to a second constant temperature increase rate slower than the first constant temperature increase rate while also irradiating ultraviolet rays; The above-mentioned object is achieved by including the steps of: heating up to a second predetermined temperature at a constant heating rate of .

[Effect]

In this invention, by organically combining resist treatment with strong ultraviolet irradiation and heating, heat resistance can be effectively improved to the inside even if the photoresist film is thick. More specifically, in the first step, as the flow temperature of the surface layer of the photoresist increases due to ultraviolet irradiation, the temperature of the photoresist is increased at a first constant rate to a first predetermined temperature. Irradiation treatment is performed while increasing the temperature at a rapid rate. Here, the flow temperature increases as the ultraviolet irradiation progresses, but since there is a difference in the degree of ultraviolet irradiation between the surface layer and the inside, the rate of increase in the flow temperature differs between the surface layer and the inside. In other words, although the rate of increase in flow temperature in the surface layer is high, the heat resistance and plasma etching resistance of the surface layer are efficiently improved by the first stage treatment in which the temperature is increased at a correspondingly high rate. However, if the temperature continues to rise at the same rate and the irradiation time is shortened, as mentioned above, the polymerization of the surface layer will progress significantly and it will be difficult for ultraviolet rays to penetrate inside, so the internal heat resistance will not improve sufficiently. However, in the present invention, in the second stage, after reaching the first predetermined temperature, the temperature is increased to the second predetermined temperature at a second constant temperature increase rate that is slower than the first constant temperature increase rate, that is, the final treatment. Heat up to temperature. Therefore, ultraviolet rays can penetrate well into the photoresist, and as the internal flow temperature increases, the processing temperature can be raised, so even if the photoresist film is thick, its internal heat resistance is sufficiently improved. do.

[Example] FIG. 1 shows an example of an apparatus for carrying out the resist processing method according to the present invention.

A patterned photoresist 4 is formed on a semiconductor wafer 5 , and the semiconductor wafer 5 is placed on a wafer processing table 6 . Wafer processing table 6
is heated by the heater 10 by supplying electricity through the heater lead wire 9, or cooled by flowing cooling water through the cooling hole 11. The temperature of the semiconductor wafer 5 is controlled by this heating and cooling mechanism. Temperature detection is performed by a temperature sensor 12, and the output of this temperature sensor 12 is used, for example, as a control signal for power supply to the heater 10. Further, the wafer processing table 6 is provided with a vacuum suction hole 7, which has the function of tightly fixing the semiconductor wafer 5 on the wafer processing table 6 by drawing a vacuum through the communication hole 8 with a vacuum pump. It also has The irradiation unit is composed of a high-pressure mercury lamp 1, a concave mirror 2, and a shutter 3 that can be opened and closed, and the radiation including ultraviolet rays emitted from the high-pressure mercury lamp 1 is reflected by the concave mirror 2, etc.
The photoresist 4 coated on the semiconductor wafer 5 is irradiated with light.

Next, a method of resist processing using this resist processing apparatus will be explained. A semiconductor wafer 5 coated with a photoresist 4 is placed on a wafer processing table 6 that has been heated in advance to a temperature slightly higher than the flow temperature, which is the allowable temperature limit of the photoresist 4. Then, by evacuating the vacuum suction hole 7, the semiconductor wafer 5 is brought into close contact with the wafer processing table 6.
In this state, the shutter 3 is opened and the photoresist 4 is irradiated with light containing ultraviolet light emitted from the high-pressure mercury lamp 1. This irradiation causes the flow temperature of the photoresist 4 to rise, but the heater power of the wafer processing table 6 is controlled accordingly, and the wafer processing table 6 is kept constant so that the photoresist temperature is always slightly higher than the flow temperature. The temperature is raised to the first predetermined temperature at a heating rate of . Thereafter, the temperature is increased to a second predetermined temperature at a second constant temperature increase rate in which the temperature increase rate is suppressed by, for example, slightly weakening the power supplied to the heater 10 or increasing cooling. In terms of control accuracy, it is easier to execute by lowering the power supplied to the heater 10. When the process is finished, stop heating,
Close the shutter 3 to stop synchrotron radiation.
Then, cooling water is allowed to flow through the cooling holes 11 to cool the semiconductor wafer 5 to a predetermined temperature, the vacuum suction is released, and the semiconductor wafer 5 is removed from the wafer processing table 6 . Once the processing is completed, the above operations may be repeated to sequentially perform the registration processing.

This will be explained in more detail below.

Using the aforementioned equipment, the Tokyo Ohka Kogyo Co., Ltd.
A 2.0 μm thick photoresist coated with TSMR-8800 and molded was subjected to ultraviolet irradiation treatment based on the time chart shown in FIG. That is, first, a wafer is placed on a processing table maintained at 100°C,
The temperature was raised to 170℃ at a constant temperature increase rate of 0.78℃/sec, and then at a constant temperature increase rate of 0.25℃/sec.
The temperature was raised to 220℃. As a result, the heat resistance temperature of the photoresist, which was 130°C before treatment, increased to 300°C. Therefore, durability against ion implantation and plasma etching is significantly improved, making it suitable for producing patterns with small line widths. Incidentally, in the past, there were almost no examples of increasing the heat resistance temperature to 300°C, and even if heat resistance were to be improved to this temperature, it was thought that it would be necessary to process for a very long time.

〔Effect of the invention〕

As explained above, a photoresist coated on a wafer placed on a processing table equipped with a temperature control means is irradiated with ultraviolet rays to increase the flow temperature of the photoresist, thereby improving its heat resistance and plasma resistance. In a resist processing method that improves the photoresist flow temperature, the wafer is placed on a processing table that is preheated to a temperature slightly higher than the flow temperature of the photoresist, and the processing table is heated while irradiating ultraviolet rays until the photoresist temperature is always slightly higher than the flow temperature. A step of increasing the temperature to a first predetermined temperature at a first uniform temperature increase rate, and after reaching the first predetermined temperature, a second step of increasing the temperature at a rate slower than the first constant temperature increase rate while also irradiating ultraviolet rays. This method includes the step of raising the temperature to the second predetermined temperature at a constant temperature increase rate, so even if the photoresist film is thick, it is possible to sufficiently improve the heat resistance to the inside of the photoresist film, and it can be done in a short time. Both heat resistance and plasma resistance can be improved by heating and ultraviolet irradiation, which significantly improves productivity.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of an apparatus for implementing the resist processing method according to the present invention, and FIG. 2 is a time chart of the processing method. 1...High-pressure mercury lamp, 2...Concave mirror, 3...Shutter, 4...Photoresist, 5...Semiconductor wafer,
6... Wafer processing table, 7... Vacuum suction hole, 8... Communication hole, 9... Heater lead wire, 10... Heater, 11...
Cooling hole, 12...Temperature sensor.

Claims (1)

[Claims] 1. Irradiating ultraviolet rays to a photoresist coated on a wafer placed on a processing table equipped with a temperature control means to increase the flow temperature of the photoresist;
In a resist processing method for improving its heat resistance and plasma resistance, a wafer is placed on a processing table that has been heated in advance to a temperature slightly higher than the flow temperature of the photoresist, and the processing table is heated to a temperature of the photoresist while being irradiated with ultraviolet rays. a step of raising the temperature to a first predetermined temperature at a first constant temperature increase rate that is always slightly higher than the flow temperature; A resist processing method comprising the steps of: raising the temperature to a second predetermined temperature at a second constant temperature increase rate that is slower than the constant temperature increase rate of .