JPS593549B2 - Surface treatment method for substrate to be treated - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a substrate for a photomask, in which a thin film of chrome or the like is deposited on a glass substrate, a photoresist is applied thereon, prebaked, and then exposed to light using a master plate; A thin film of aluminum is deposited on silicon, a photoresist coated on top is prebaked, and then a photomask is used to expose the silicon wafer. Processes such as development, etching, and film removal are performed on the silicon wafer. A surface treatment method for a substrate to be processed using a so-called spin spray method, in which processing liquids are sequentially sprayed from a nozzle while rotating the substrate to be processed, and a method for developing and etching the substrate. It is something.

FIG. 1 is an explanatory diagram schematically showing a surface treatment process of a silicon wafer by a photolithography process.
In the figure, 1 is a silicon wafer, 2 is a metal thin film such as aluminum deposited on it, 3 is a photoresist coated on the soil, and 5 is a photomask having a mask pattern 4. A is a process of vapor deposition of a metal thin film 2 such as aluminum onto a silicon wafer 1, a photoresist 3 is applied and a pre-bake process is shown, and C is a process of positioning and contact exposure with ultraviolet light (indicated by an arrow) (projection exposure may also be performed). .) process, 2 is the development (and post-bake) process, 5 is the etching process of the metal thin film 2, 3 is the peeling process of the photoresist 3, and between the processes 2, 5 and 6, and after the process . may be piloted and dried. In addition, in the above, 1 is a glass substrate,
The same applies if 2 is a vapor deposited film of chromium or the like. Among these treatment steps, various methods have been tried in the past to implement each treatment step, but the current method is
As shown in the figure, a horizontal plane occupying a certain position in a space surrounded by a guard 11 and provided with measures to prevent splashes and vapors of processing liquids such as developing solution, etching solution, and stripping solution from flowing into the work room. The vacuum chuck rotary plate (spinner head) 12 is rotated, for example, the silicon wafer 10 that has undergone the steps A, C, and C is fixedly held on the plate surface, and while being rotated at a predetermined rotational speed, the spinner head 12 is rotated. A method of surface treatment, such as development, by uniformly spraying a processing liquid, such as a developing liquid, over a predetermined period of time onto the surface of the surface from a nozzle 13, ie, a spin spray method, has come into widespread use. Surface treatment of a substrate to be treated, such as a silicon wafer 10, in a rotary surface treatment apparatus whose main parts are shown in a partial side sectional view in FIG.
The current method of development will be explained below.

First, the silicon wafer 10 which has undergone the above-mentioned steps 1 to 3 is adsorbed onto the vacuum chuck rotary plate 12 with its center aligned and fixedly held. Then, a draft device (not shown) is operated so that airflow flows from an opening in a top plate (not shown) provided at the top of the guard 11 to the outlet 14 of the guard 11. The silicon wafer 10 is rotated by rotating the vacuum chuck rotary plate 12 at, for example, 500 rpm, and a developer is sprayed onto the rotating silicon wafer 10 from a developer spray nozzle 13 for about 20 seconds. In this case, since the circumferential speed is different between the center and the outer edge of the silicon wafer 10, centrifugal force acts on the developing solution on the surface of the silicon wafer 10 hardly at the center, but strongly at the outer edge. act. The formed image liquid layer is thinner at the outer edge than at the center, resulting in uneven development. In order to suppress the occurrence of uneven development, the rotational speed of the vacuum chuck rotating plate 12 is reduced to 1 for a short period of time just before stopping the injection of the developer.
The rotation speed is reduced to about 0.00 rpm, and the rotation is continued for about 20 seconds even after the injection of the developer has stopped, to complete the development. Now, the surface tension of the developer is γL, and the contact angle with the silicon wafer is θ.
Then, the wettability measure A = RLeOsθ, but since this θ is small when exposed to the developer, the wettability measure A becomes large, and the silicon wafer 10 is easily wetted by the developer. However, in addition, the rotational speed of silicon wafer 10 can be reduced depending on the location of the centrifugal force acting on the developer layer of silicon wafer 10.
By making the developer form a layer of about 0.2 to 1 mm on the surface of the mask and stagnate almost uniformly, uneven development can be prevented and an accurate development pattern as shown in mask pattern 9 can be obtained. That is to say.

However, in this conventional developing method, the silicon wafer is rotated by a vacuum chuck rotating plate 1t during development.
10 is rotated only in one direction, for example, counterclockwise, for example, after exposure according to the mask pattern 4 of the positive type photoresist 3, the unexposed portion that is insoluble in the developer, i.e. Development pattern 35
However, the exaggerated plan view of FIG. 4 and its V-V
The problem is that the image is developed with minute distortions as shown in the cross-sectional view of FIG. 5.

This fine strain exists on the A side shown in the figure, and the development reaction progresses slightly excessively, so that the width B in the V-V cross section of FIG. 4, that is, the width B on the A side (FIG. This is caused by thinning by 3μ. This invention was made in order to solve the above-mentioned problems in the conventional spin-spray method for surface treatment of a substrate to be processed, especially in the development method.
In a spin-spray surface treatment method in which surface treatment is performed by spraying a treatment liquid onto the surface of the substrate from a nozzle while rotating the substrate, the direction of rotation of the substrate is changed at regular intervals. The present invention relates to a surface treatment method for a substrate to be processed, which is characterized in that the surface treatment is performed alternately in the counterclockwise direction and in the counterclockwise direction. Embodiments of the invention will now be described in detail with reference to the drawings.

As shown in FIG. 2, the developer solution shown in the figure is sprayed from the developer spray nozzle 13 onto the surface of the silicon wafer 10 to wet the entire surface of the silicon wafer 10. At the same time as this injection, the wafer 10 is rotated clockwise by the vacuum chuck rotating plate 12 at about 250 to 300 rpm.
After being rotated for about seconds, the rotation is stopped, and then the rotation is continued for about 5 seconds at the same rotational speed in a counterclockwise direction, which is the opposite direction to that described above. Repeat this clockwise and counterclockwise rotation alternately twice each? vinegar. Next, the rotational speed of the vacuum chuck rotary plate 12 is set to about 100 rpm), and the wafer 10 is rotated in the cutting direction for about 5 seconds at this rotational speed. On the other hand, at the same time as this rotation starts, the injection of the developer from the nozzle 13 is stopped. After the injection of the developer is stopped, the silicon wafer 10 is moved clockwise and then counterclockwise twice for about 5 seconds each time to complete the development. . Next, the silicon wafer 10 is washed with water for 30 seconds while being rotated counterclockwise at 500 rpm by the vacuum chuck rotary plate 12, and finally the vacuum chuck rotary plate 12
The silicon wafer 10 is rotated at a high speed (for example, 2000 rpm) for 20 seconds, water is shaken off from the silicon wafer 10, and the silicon wafer 10 is dried to complete the development process. According to this method, the total time that the developer remains on the silicon wafer 10, ie, the total time between development, is 40 to 45 seconds, which is approximately the same as that of the conventional development method.

However, in this method, the rotational motion imparted to the silicon wafer 10 while it resides on the silicon wafer 10 is achieved by repeating the same number of clockwise and counterclockwise rotations for approximately 5 seconds each. Therefore, the residual resist, that is, the difference in the degree of progress of the development reaction with respect to the developed pattern 35, which is affected by the direction of rotation of the silicon wafer 10, is removed. As can be seen from the sectional view of FIG. 7 showing the -■ cross section, it is possible to obtain an accurate developed pattern throughout the mask pattern without causing minute distortions.

(b) It goes without saying that the rotational speed of the silicon wafer 10 and the length of time for one rotation in both directions are given as examples, and can be changed as appropriate.

What is the rotational speed when the wafer size is 3 inches, and when it is different from 2 inches or 5 inches? It is desirable to adjust the amount appropriately. Next, vacuum chuck rotating plate 1
An additional comment is made regarding the second rotation mechanism.

This rotating shaft 15 is mounted on a bearing (not shown) fixed to the machine base.
It is rotatably supported by the bearing and fixed to the rotating shaft 15 under the bearing. A timing belt is passed between a driven toothed pulley and a single drive toothed pulley at the output shaft end of a variable speed motor (for example, a DC motor) fixed to the machine base. Rotation and driving are performed by holding the shaft.

FIG. 3 shows an example of a control electric circuit for a DC motor of a rotating mechanism. In the figure, M is a DC motor, G is a tachometer generator, R is a switch switching relay, S is a servo amplifier, T is a timer for switching the rotation direction of the DC motor M and setting the time for holding the same rotation direction, and C is a changeover switch. When it is connected to the 1 side of the human power signal, the vacuum chuck rotating plate 12 is moved, for example, in the clockwise direction, and when it is connected to the → side of the input signal, the rotating plate 12 is moved, for example, in the counterclockwise direction, respectively. It is rotationally driven by. Moreover, this surface treatment method can of course be used for the etching process of the metal thin film 2 shown in FIG. In this case, the treatment liquid injection nozzle 1
3, the etching solution may be injected onto the silicon wafer 10 which is rotated alternately in both clockwise and counterclockwise directions for a fixed period of time in accordance with the developing process. In this case, the etching progresses not only in the thickness direction of the metal thin film 2, but also in a direction parallel to the surface of the thin film, and sometimes to the inside of the ring of the developed resist pattern 35 (this is called undercutting). It is important to prevent the occurrence of undercuts (referred to as It is easy to reduce and make the damage uniform. As is clear from the above explanation, the method for surface treatment of a substrate to be treated according to the present invention involves rotating the substrate to be treated and spraying a liquid to be treated from a nozzle onto the surface of the substrate to perform surface treatment. Although it uses a spin-spray method, the direction of rotation of the substrate to be processed is alternately changed clockwise and counterclockwise at regular intervals. When developing a wafer, the difference in the degree of progress of the development reaction to the developed pattern, which is affected by the direction of rotation of the silicon wafer, is removed, and an accurate developed pattern can be obtained without causing minute pattern distortion. Furthermore, in the subsequent etching of the metal thin film, undercutting can be reduced and made more uniform for the same reason as compared to the conventional method using unidirectional rotation.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram schematically showing the surface treatment process involved in the lithography process for silicon wafers, Fig. 2 is a partial side sectional view showing the main parts of an example of a rotary surface processing apparatus, 3 is a circuit diagram showing an example of the electric circuit for controlling the DC motor of the rotating mechanism of the surface treatment apparatus shown in FIG. 2; FIG. FIG. 5 is a sectional view taken along the line V-V, FIG. 6 is a plan view of a developed pattern of the photoresist according to the method of the present invention, and FIG. 7 is a sectional view taken along the line 1--2. 1... Silicon wafer, 2... Metal thin film, 3...
Photoresist, 10... Substrate to be processed (silicon wafer after the previous process), 12... Vacuum chuck rotating plate, 13... Nozzle 15... Rotating shaft.

Claims (1)

[Claims] 1. In a surface treatment method using a spin spray method in which surface treatment is performed by spraying a treatment liquid onto the surface of a substrate from a nozzle while rotating the substrate, the direction of rotation of the substrate to be treated is clockwise or counterclockwise. 1. A method for surface treatment of a substrate to be treated, characterized in that the surface of the substrate is alternately converted to .