Substrate treatment process

Abstract

In a substrate treatment process, substrates are moved by a transporting device in a transporting direction through a substrate treatment installation having a number of chambers. The substrates are moved by transporting sections of the transporting device driven independently of one another. The transporting sections are driven such that, if substrates dwell temporarily in the transporting section, they are moved back and forth. Stresses in a substrate brought about by differing inputs of heat as a result of both process-induced and malfunction-induced dwell times of the substrate in a chamber are reduced by compensating within the chamber for a structurally brought about input of heat into the substrate, varying periodically over the length of the chamber, during temporary dwelling of the substrate in the chamber by moving the substrate back and forth over at least one period of the heat input by a change of the transporting direction.

Claims

1. A substrate treatment process, in which substrates are moved by a transporting device in a transport plane in a transporting direction through a substrate treatment installation having a number of chambers, the substrates being moved by transporting sections of the transporting device that are driven independently of one another and the transporting sections of the transporting device being driven in such a way that, if a substrate dwells temporarily in a first transporting section, the substrate arranged on the first transporting section is moved back and forth in an oscillating movement, wherein, within a chamber of the substrate treatment installation, compensation is provided for a structurally brought about input of heat into a substrate, an intensity of the input of heat varying periodically over a length of the chamber with a period corresponding to a spacing between two transporting rollers of the transporting device arranged following one another in the transporting direction, during temporary dwelling of the substrate in the chamber, by the substrate located in the chamber being moved back and forth over an oscillating distance of at least said spacing and less than a length of the substrate by a periodic change of transporting direction, wherein the periodic change of the transporting direction takes place on the basis of a trapezoidal velocity function, wherein the intensity of the input of heat into the substrate, varying periodically over a length of the chamber, is produced by arranging a series of heaters, below the transport plane, one behind another along the transporting direction interspersed between respective pairs of transporting rollers of the first transporting section, and wherein the oscillating distance corresponds to an integral multiple of the spacing between the two transporting rollers.

2. The substrate treatment process as claimed in claim 1, wherein the process is performed during dwelling of the substrate in a buffer chamber.

3. The substrate treatment process as claimed in claim 1, wherein the process is performed in a transfer chamber.

4. The process as claimed in claim 1, wherein the spacing is determined by a spacing between two transporting rollers of the first transporting section arranged following one another in the transporting direction, with a heater arranged between the two transporting rollers.

5. The process as claimed in claim 1, further comprising: monitoring operation of other sections of the transporting device arranged downstream of the first transporting section and, if there is detection of a backup and/or in accordance with a process sequence to be predetermined for the treatment of substrates, switching the first transporting section of the transporting device over from a continuous forward movement to the periodic change of the transporting direction.

6. The process as claimed in claim 1, wherein the substrate is moved back and forth in the chamber at a velocity such that n complete periods of the heat input are covered by precisely an end of dwell time of the temporary dwelling, n being a positive integer.

7. The process as claimed in claim 6, wherein said velocity comprises at least 2 meters/minute.

8. The process as claimed in claim 1, wherein the integral multiple equals one, and the oscillating distance is equal to the spacing.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) The invention is to be explained in more detail below on the basis of an exemplary embodiment. In the associated drawing:

(2) FIG. 1 shows a schematic cross-sectional representation of a detail of a substrate treatment installation,

(3) FIG. 2 shows a heat input profile within the chamber and

(4) FIG. 3 shows the temperature profile forming on a substrate to be treated at a standstill and when the proposed process is being used.

DETAILED DESCRIPTION

(5) In FIG. 1, a chamber 1 of a substrate treatment installation 2, which also has further chambers 3 and 4, is schematically represented.

(6) In this chamber 1, a transporting device 5 for transporting a substrate 6 is provided. This allows the substrate 6 to be moved in a substrate transporting plane 7 in the longitudinal direction 8.

(7) FIG. 1 indicates a cross section through part of a substrate treatment installation 2, which consequently extends in width transversely in relation to the longitudinal direction 8, as it were through the plane of the page.

(8) The transporting device 6 has driven transporting rollers 9, which extend longitudinally over the width of the substrate transporting plane 7, i.e. transversely in relation to the longitudinal direction of the substrate treatment installation. Arranged between the transporting rollers 9 are heaters 10, which serve for heating up the substrate 6. The alternation of transporting roller 9 and heater 10 produces a periodic profile of an input of heat into the substrate 6, i.e. the intensity of the input heat into the substrate, as is represented in FIG. 2 over the length 1 of the chamber 1, which has a total length l.sub.tot.

(9) As can be seen, for structural reasons, the input of heat changes periodically to form a heat input profile occurring periodically over the length 1 of the chamber 1, with a period L, which corresponds to the spacing a between two transporting rollers 9.

(10) When there is a movement of the substrate 6 on the transporting rollers 9, the differing input of heat into the substrate 6 is compensated. If, however, the substrate 6 must dwell in the chamber 1, for example because further transport into the following chamber 4 is not possible, the heat input profile would emerge as the temperature profile over the length of the substrate 6 if the substrate were to come to a standstill, such as that represented in FIG. 3.

(11) According to the invention, this is compensated by a substrate 6 located in the chamber 1 concerned being moved back and forth over at least one period L of the heat input by a change of the transporting direction 5. For this purpose, the transporting device 5 is designed in such a way that it forms an independently controllable transporting section in the region of the chamber 1.

(12) If the substrate 6 is moved at a constant velocity, the differences in temperature between the heater 10 and the transporting roller 9 are compensated completely after each distance over a roller spacing a. The available distance is usually limited to one or two roller spacings a. Therefore, the substrate 6 is moved back and forth (oscillated) n times. In order to keep down the negative influences due to the velocity not being constant at the necessary reversal points, the changing of the direction of movement should take place as quickly as possible. According to experience, the oscillating velocity should be at least 2 m/min. A controller calculates the velocity such that n complete roller spacings a or complete periods L are covered by precisely the end of the dwell time.

(13) In FIG. 3 it can be seen that a further temperature profile 12 is superposed on the periodic temperature profile 11 of the substrate 6 that would be obtained when the substrate is at a standstill. This results from the velocity not being constant at transitions from rapid transfer movements to slow oscillating movements. It is therefore also necessary here to pay particular attention that transfers in heated regions move at a constant velocity and the change to a different velocity takes place as quickly as possible.

(14) It must therefore be ensured for example when treating glass substrates that, in a very hot temperature regime, they always remain in motion. As soon as dwelling in a chamber is intended for process-related reasons, the glass substrate must nevertheless be kept in motion. Preferably, the substrate 6 is then moved back and forth by a transporting roller spacing a in such a way that the change between the back and forth movements takes place as quickly as possible. If the glass substrate were to dwell in one position, the differing temperature zones in the chamber 1 would form on the glass substrate 6. The maximum temperature amplitude that would then form is dependent on the difference in temperature between the heaters 10 and the transporting rollers 9 and the velocity at which the substrate 6 is moved.

(15) With oscillation of the substrate 6, the temperature profile 12 will then be established over the length of the substrate 6.