JPH02263983A - Formation of film by sputtering - Google Patents

Abstract

PURPOSE:To allow the thickness of a film to attain accurately to the desired value even when the temp. of a substrate is arbitrarily changed during sputtering by calculating the rate of film formation at each time of measuring the temp. of the substrate from a previously set formula expressing the relation between the temp. of the substrate and the rate of film formation and by stopping sputtering at the time when the estimated value of the thickness of a film attains to the desired value. CONSTITUTION:When sputtering is carried out under nearly fixed conditions except the temp. of a substrate, a formula expressing the relation between the temp. of the substrate and the rate of film formation is previously registered in a controller. After the beginning of sputtering, the temp. of the substrate is measured at regular intervals of time and inputted into the controller and the rate of film formation is calculated from the formula every time the temp. is inputted. The product of the rate of film formation and unit time is then calculated with the controller to obtain the thickness of a film formed in a certain time. This thickness is cumulated during sputtering and the resulting value is considered to be the estimated value of the thickness of a film at the cumulation time. At the time when the estimated value attains to the desired value registered in the controller, sputtering is stopped.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sputter film forming method that can form a film to a predetermined thickness with high precision even if the substrate temperature changes during sputtering. .

[Conventional technology]

Sputtering is a thin film formation method with excellent reproducibility. Also, in particular,
The magnetron sputtering apparatus described in No. 9 has been widely used in manufacturing processes for semiconductors and the like because the film formation rate is high and it is possible to form a film while keeping the substrate at a low temperature.

In sputtering, the substrate is placed in an electric field, so the substrate temperature rises even without external heating of the substrate. In order to form uniform modification, it is desirable that the substrate temperature be as constant as possible. In a general sputtering film forming method, the film forming rate is kept constant by keeping all settable sputtering conditions including the substrate temperature constant.

As a method of keeping the substrate temperature constant during sputtering, there is a method of optimally controlling the substrate temperature by heating a metal contact plate installed close to the substrate, as described in Japanese Patent Application Laid-Open No. 62-50462. As described in JP-A No. 63-65066, there is a method of controlling heating by forming a heat pipe in a substrate holder and operating it as an evaporation section for the heat transfer medium inside.

Furthermore, after sputtering is completed, it is desirable to cool the substrate sufficiently before breaking the vacuum. The reason for this is to prevent the thin film from deteriorating due to exposure to the atmosphere at high temperatures.Normally, it is common to cool naturally while maintaining a high vacuum.
As described in Japanese Unexamined Patent Publication No. 59-70776, there is also a method of efficiently cooling the substrate by lowering the substrate temperature by current control and linearly lowering the temperature with a cooling medium when necessary.

[Problem that the invention seeks to solve]

In sputtering equipment, in order to form a thin film with the required modification, the substrate is often heated and deposited while keeping the temperature constant.In this case, the substrate is heated below a certain temperature to prevent film quality deterioration. After cooling, it is necessary to break the vacuum and take out the substrate. If natural cooling is performed after sputtering is completed, the operating efficiency of the sputtering apparatus will deteriorate because cooling will take a long time. Moreover, when cooling is performed forcibly, the sputtering apparatus becomes large-scale and the initial cost becomes high. Modifying a device without a forced cooling function is difficult depending on the structure around the board.

Further, there are cases where it is desired to change the temperature little by little during sputtering. For example, while the initial layer of a thin film needs to be formed while maintaining the substrate at a high temperature, heating of the substrate after the intermediate layer is stopped in order to shorten the cooling time. However, it is known that when the substrate temperature changes during sputtering, the film formation rate (sputter rate) changes significantly, and it is difficult to accurately keep the film thickness within a predetermined value using this method.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sputter film forming method that solves the above-mentioned problems and makes it easy to accurately maintain the film thickness within a target value even if the substrate temperature is arbitrarily changed during sputtering.

[Means for solving problems]

The present invention is a sputtering method in which sputtering conditions other than substrate temperature are kept almost constant, and a relational expression between substrate temperature and film formation rate is registered in advance in a control device, and after the start of sputtering, the substrate temperature is is measured and input to the control device. Each time this temperature is input using the control device, the film formation rate is determined from the relational expression between the substrate temperature and the film formation rate. continue,
Using a control device, the product of the film formation rate and unit time is calculated to determine the film thickness for a certain period of time, and the value accumulated during sputtering is used as the estimated film thickness at that time. Then, when this estimated film thickness value reaches a target film thickness value registered in advance in the control device, sputtering is stopped.

〔Example〕

An embodiment of the present invention will be described with respect to a method of forming a thin film of SiO□ using a high frequency magnetron sputtering device. In this example, as shown in FIG. 3, the substrate temperature is controlled to a constant temperature using a heater provided in the sputtering apparatus until a certain time t after the start of sputtering, and thereafter the heating of the heater is stopped. Therefore, we adopted a natural cooling method to shorten the substrate cooling time.

FIG. 1 is a diagram showing the entire apparatus for implementing the present invention. In the figure, 1 is a sputtering device.

2 consists of a microcomputer +li! I
011 device, input/output device 3 such as keyboard and CRT
, an external storage device 4 such as a hard disk is connected. A/D converters 5a, 5b, 5c, .
b, board temperature 6c,... at fixed time intervals #door device 2
It is now being incorporated into the 7 is a power supply device of the sputtering apparatus 1.

In the present invention, first, the relationship between the substrate temperature during sputtering and the film formation rate is determined, and this relationship is determined in advance. II control device 2
Register it in the storage device. The relationship between the substrate temperature and film formation rate described above is determined as follows.

1) Using an apparatus having the configuration shown in FIG. 1, the sputtering conditions are controlled so that the sputtering conditions other than the substrate temperature 6c are always constant. The upper and lower limits of the substrate temperature can be changed arbitrarily during sputtering (for example, 150°C to 350°C).
Set a temperature interval of about 20"C at each temperature, keep the temperature constant for each temperature, and deposit a sputtering film on the substrate for a certain period of time. After sputtering is finished, measure the film thickness on the substrate. Then, The value obtained by dividing the measured film thickness by the sputtering time is defined as the film formation rate at that temperature.

2) Once the film formation rates at all the set temperatures have been determined, the relational expression TI between the substrate temperature and the film formation rate is determined using a regression analysis method.

r (f) = r + (f) + r z (f) +
rs(f) +++++++++... (Formula 11, where r (f) is the film formation rate when the substrate temperature is f, and r
+(f), rz(f), and r5(f) are each a function of the substrate temperature f realized as a result of regression analysis. Further, FIG. 2 shows an example of a graph representing the relationship between the substrate temperature 1 and the film formation rate 2.

The above relational expression (1) can be obtained by incorporating a regression analysis program into the control device 1, or alternatively, it can be obtained using another personal computer.

3) Register the above relational expression (1) between substrate temperature and film formation rate in the external storage device 4 of the control device 1.

Next, a sputtering film forming method will be explained.

First, the program of the control device 2 is started, and a target film thickness value is inputted from the input/output device 3 and registered in the control device 2. Subsequently, the sputtering apparatus 1 is operated. The sputtering apparatus 1 is set in advance to heat the substrate to a constant temperature (for example, 300°C) until a certain period of time has elapsed (for example, 30 minutes at t shown in FIG. 3) after the start of sputtering, and then it is heated naturally. Cooling.

When the sputtering apparatus 1 is operated and sputtering work begins, the control apparatus 2 automatically acquires the substrate temperature of the sputtering apparatus 1 at regular intervals, for example, every 10 seconds, via the AD converter 5. Then, each time the substrate temperature is input, the control device 2 calculates the film formation rate at this point in time from the relational expression fll between the substrate temperature and the film formation rate shown in FIG. Subsequently, the control device 2 calculates the product of the film formation rate and the unit time (10 seconds), and sets it as the film thickness per unit time at that point. and,
The film thickness per unit time is accumulated to obtain the estimated film thickness at that time. In this way, the control device 2 calculates the estimated sputter film thickness each time the substrate temperature is input, and when this value reaches the target film thickness value, outputs the sputter stop signal 8 to the power supply 7 of the sputter device 1. do. As a result, one batch of sputtering work is completed, the vacuum inside the sputtering apparatus 1 is broken, and the substrate on which the sputtered film has been formed is removed.

〔Effect of the invention〕

The present invention described above has the following effects.

■) Even if the substrate temperature is changed during sputtering, the target film thickness can be formed with high accuracy.Especially after starting sputtering,
The present invention is highly effective when applied to a sputtering film forming method in which a substrate is heated to a certain temperature for a certain period of time, and then heating of the substrate is stopped.

2) The present invention can be implemented without major modification of existing sputtering equipment.

3) If the present invention is applied to film formation in which sputtering is performed while naturally cooling the substrate during sputtering, it is possible to perform film formation with high accuracy with respect to the target film thickness value.

[Brief explanation of drawings]

Fig. 1 is an overall diagram showing an embodiment of the present invention, Fig. 2 is a graph showing the relationship between substrate temperature and film formation rate, and Fig. 3 is a graph showing the temperature drop after heating the substrate to a constant temperature. It is. 1 varnish batter device, 2; control device, 3; input/output device. Figure Figure Figure Time

Claims (1)

[Claims] In a sputter film deposition method, the sputtering conditions other than the substrate temperature are kept almost constant, the substrate is heated to a predetermined temperature until a certain period of time has elapsed after the start of sputtering, and then substrate heating is stopped until the end of the sputtering. A relational expression with the film speed is registered in the control device, and after the start of sputtering, the substrate temperature is measured at fixed time intervals and inputted into the control device, and the film formation rate at each substrate temperature measurement is determined from the relational expression. A sputtering film forming method, comprising: calculating an estimated film thickness at the time of substrate temperature measurement from the film forming rate and sputtering time, and stopping sputtering when the estimated film thickness reaches a target film thickness value.