SU758054A1 - Method and device for automatic developing of metallized photo patterns - Google Patents

Description

The invention relates to photographic methods and processes, and in particular to methods for developing photomasks for the manufacture of semiconductor devices, large and extra-large integrated circuits. .

Known methods of manifestation of photosensitive materials, which consists in the fact that the photosensitive layer is placed between the electrodes and summed up during the development of the electric voltage for 30 s, and after the development of the voltage is removed.

Drawbacks of the method are the lack of monitoring of the processes' sa ⁵ manifestations and the need to control display for selecting the processing time.

Known devices for processing photomasks containing a developing tank, a control unit with a time relay, a DC source and two electrodes [2 ^.

2

The disadvantages of these devices are the inability to automatically adjust the time of development directly during processing, as well as the insufficiently high quality of the development of photomasks.

There are known methods for automatically developing metallized photo masks, which consist in measuring electrical current between the metallized layer of the photomask and the bath electrode and determining the first derivative of the current function over time, the magnitude of which controls the development process [s].

The disadvantage of these methods is the low quality of the development of photomasks. Known devices for implementing

data methods containing a bath with

negative electrode

DC power potential

DC amplifier, input of which is 758054

The go is connected to a metallized layer of a photomask, a differentiating device, and an actuator [3].

The disadvantage of these devices is high precision control. $

To improve the quality of photomask development and control accuracy, the proposed method additionally measures the initial value of the second derivative of the current function over time, determines its ratio to the initial value of the first derivative, and terminates the development process after a time interval equal to the modulus of this ratio. 15

In the proposed device add. A delay circuit, an electronic key, a differentiating device, a dividing unit and a time relay have been entered; the amplifier output is connected to the first ₂ θ input of the electronic key, the second input of which is connected to the delay circuit, and the output to the first differentiating device whose outputs are connected directly and through the second differential device to the division unit, the output of which is connected via an time relay to the actuator.

The essence of the method is that the moment of termination of the process is determined by the magnitude of the slope of the curve of the current function from time to its initial part. The rate of current increase between the electrode and the metallized layer of the photomask depends on the properties of the developer and photoresist, the magnitude of the applied voltage and the area of the washed out areas. The higher this speed, hem less time lasts the process of developing photomask. However, it is not possible to determine the development time using the initial value of only the first derivative of the current function over time. In connection with this process manifestation nyya ₄₅ is stopped after a time interval whose magnitude is directly proportional to the initial value modulo the first derivative and inversely proportional to the modulus of the initial values of the second derivative of the current function of time.

FIG. .1 is a block diagram of a device implementing the proposed method, a general view; in fig. 2 - current versus time.

The device consists of a bath 1 with a developer 2 and an electrode 3, a constant current source 4, a load resistance 5 connected to the negative

thirty

35

40

50

55

the pole of the DC source 4 and to the metallized layer. 6 photo masks with the substrate 7 and the photoresist film 8, as well as the direct current amplifier 9, the first differentiating device 10 and the actuator 11, the delay circuit 12, the electronic switch 13, the second differentiating device 14, the target unit 15 and the time relay 16.

The device works as follows.

When the metallized layer 6 of the photomask is connected to the DC source 4 and when the photomask is placed in the bath 1 with the developer 2, a development process takes place, i.e. leaching of individual sections of the film 8. In this connection, the ohmic resistance of the circuit: electrode 3 - developer 2 - metallized the photomask layer 6 decreases, the current in the circuit grows along the curve shown in FIG. 2, a. The voltage taken from the resistance of the load 5, is amplified using a DC amplifier 9 and through the electronic key 13 is fed to the input of the differentiating device 10.

The control of the electronic key 13, the main element of which is, for example, the Schmitt trigger, is produced using the delay circuit 12, for example, in the form of a generator of linearly varying voltage. The delay circuit 12 provides the inclusion of an electronic key 13 at the time f _about the time required for accurate measurement of the first and. second derivative of the current function of time. A time delay. £ - £ _{o is} necessary in order to avoid significant runes. Decisions Measurements at zero time, since the modules of the first and second derivatives tend to infinity (see; Fig. 2, b, c) due to the fact that the value of the current 3 ₀ at time point £ -0 is infinitely small or even zero / From the output of the differentiating device 1O, a voltage proportional to <33 / <3 £ is supplied to one of the inputs of the division unit 15 and to the input of the second differentiating device 14.

From the last output, the signal 8 ² 3 / <3 £ ^{2 is} fed to the second input of the division unit 15. Its output voltage is directly proportional to the module of the first derivative of the current function of time and inversely proportional to the module of the first derivative of the current function of time and 758054

five

It is proportional to the module of the second derivative, producing control, barely ¹ time, which turns on the actuator, automatically stopping the development process.

When using the method and device significantly increases the accuracy of determining the time of development of photomasks. Due to that, the quality of manifestation increases, especially high-complexity photo masks for making large and extra-large integrated circuits. For example, the percentage of the yield of suitable photomasks from C p on glass. substrate For the manufacture of chips 15 on a semiconductor wafer with a diameter of 60 mm increases by 25-30%. In addition, in this case, the processing conditions of the metal film are improved due to the application of a voltage of 0.1–2 V, which creates a directional ionic process and cathodic protection of the metal film against the effects of negative developer ions.

Claims (2)

Claim 1. A method for the automatic development of zo-metallized photo masks, which consists in that an electric current is measured between the metallized layer of the photomask and the electrode bath and the first derivative of the current function ₃₅ is determined over time, the magnitude of which is controlled by the development process, which the purpose. improve the quality of the development of photomasks, additionally measure the initial 40 6 the value of the second derivative of the function go - ι ka from time to time, determines its relation to the initial value of the first derivative and stops the process of manifestation 5 after a period of time equal to the modulus of the given relation. 2. A device for the automatic development of metallized photomasks, containing a bath with an electrode, 10 connected with a negative potential of a DC source, a DC amplifier whose input is connected to a metallized photomask layer, a differentiating device and an actuator, characterized in that, in order to improve control accuracy and quality of development, a delay circuit is added to it, an electronic switch , the second differential device, a division unit and a time relay, the amplifier output being connected to the first input of the electronic switch, the second input of which is connected to the deceleration circuit ki, and output - with a first differentiating unit 25, the outputs of which are connected directly and via a second differentiator to the block division, the output of which is connected via a time switch with the actuator.